WorldWideScience

Sample records for surface interaction forces

  1. Probing anisotropic surface properties and interaction forces of chrysotile rods by atomic force microscopy and rheology.

    Science.gov (United States)

    Yang, Dingzheng; Xie, Lei; Bobicki, Erin; Xu, Zhenghe; Liu, Qingxia; Zeng, Hongbo

    2014-09-16

    Understanding the surface properties and interactions of nonspherical particles is of both fundamental and practical importance in the rheology of complex fluids in various engineering applications. In this work, natural chrysotile, a phyllosilicate composed of 1:1 stacked silica and brucite layers which coil into cylindrical structure, was chosen as a model rod-shaped particle. The interactions of chrysotile brucite-like basal or bilayered edge planes and a silicon nitride tip were measured using an atomic force microscope (AFM). The force-distance profiles were fitted using the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, which demonstrates anisotropic and pH-dependent surface charge properties of brucite-like basal plane and bilayered edge surface. The points of zero charge (PZC) of the basal and edge planes were estimated to be around pH 10-11 and 6-7, respectively. Rheology measurements of 7 vol % chrysotile (with an aspect ratio of 14.5) in 10 mM NaCl solution showed pH-dependent yield stress with a local maximum around pH 7-9, which falls between the two PZC values of the edge and basal planes of the rod particles. On the basis of the surface potentials of the edge and basal planes obtained from AFM measurements, theoretical analysis of the surface interactions of edge-edge, basal-edge, and basal-basal planes of the chrysotile rods suggests the yield stress maximum observed could be mainly attributed to the basal-edge attractions. Our results indicate that the anisotropic surface properties (e.g., charges) of chrysotile rods play an important role in the particle-particle interaction and rheological behavior, which also provides insight into the basic understanding of the colloidal interactions and rheology of nonspherical particles.

  2. Interaction force measurement between E. coli cells and nanoparticles immobilized surfaces by using AFM.

    Science.gov (United States)

    Zhang, Wen; Stack, Andrew G; Chen, Yongsheng

    2011-02-01

    To better understand environmental behaviors of nanoparticles (NPs), we used the atomic force microscopy (AFM) to measure interaction forces between E. coli cells and NPs immobilized on surfaces in an aqueous environment. The results showed that adhesion force strength was significantly influenced by particle size for both hematite (α-Fe(2)O(3)) and corundum (α-Al(2)O(3)) NPs whereas the effect on the repulsive force was not observed. The adhesion force decreased from 6.3±0.7nN to 0.8±0.4nN as hematite NPs increased from 26nm to 98nm in diameter. Corundum NPs exhibited a similar dependence of adhesion force on particle size. The Johnson-Kendall-Roberts (JKR) model was employed to estimate the contact area between E. coli cells and NPs, and based on the JKR model a new model that considers local effective contact area was developed. The prediction of the new model matched the size dependence of adhesion force in experimental results. Size effects on adhesion forces may originate from the difference in local effective contact areas as supported by our model. These findings provide fundamental information for interpreting the environmental behaviors and biological interactions of NPs, which barely have been addressed. Copyright © 2010 Elsevier B.V. All rights reserved.

  3. Nanophotonic force microscopy: characterizing particle-surface interactions using near-field photonics.

    Science.gov (United States)

    Schein, Perry; Kang, Pilgyu; O'Dell, Dakota; Erickson, David

    2015-02-11

    Direct measurements of particle-surface interactions are important for characterizing the stability and behavior of colloidal and nanoparticle suspensions. Current techniques are limited in their ability to measure pico-Newton scale interaction forces on submicrometer particles due to signal detection limits and thermal noise. Here we present a new technique for making measurements in this regime, which we refer to as nanophotonic force microscopy. Using a photonic crystal resonator, we generate a strongly localized region of exponentially decaying, near-field light that allows us to confine small particles close to a surface. From the statistical distribution of the light intensity scattered by the particle we are able to map out the potential well of the trap and directly quantify the repulsive force between the nanoparticle and the surface. As shown in this Letter, our technique is not limited by thermal noise, and therefore, we are able to resolve interaction forces smaller than 1 pN on dielectric particles as small as 100 nm in diameter.

  4. Surface mediated cooperative interactions of drugs enhance mechanical forces for antibiotic action

    Science.gov (United States)

    Ndieyira, Joseph W.; Bailey, Joe; Patil, Samadhan B.; Vögtli, Manuel; Cooper, Matthew A.; Abell, Chris; McKendry, Rachel A.; Aeppli, Gabriel

    2017-02-01

    The alarming increase of pathogenic bacteria that are resistant to multiple antibiotics is now recognized as a major health issue fuelling demand for new drugs. Bacterial resistance is often caused by molecular changes at the bacterial surface, which alter the nature of specific drug-target interactions. Here, we identify a novel mechanism by which drug-target interactions in resistant bacteria can be enhanced. We examined the surface forces generated by four antibiotics; vancomycin, ristomycin, chloroeremomycin and oritavancin against drug-susceptible and drug-resistant targets on a cantilever and demonstrated significant differences in mechanical response when drug-resistant targets are challenged with different antibiotics although no significant differences were observed when using susceptible targets. Remarkably, the binding affinity for oritavancin against drug-resistant targets (70 nM) was found to be 11,000 times stronger than for vancomycin (800 μM), a powerful antibiotic used as the last resort treatment for streptococcal and staphylococcal bacteria including methicillin-resistant Staphylococcus aureus (MRSA). Using an exactly solvable model, which takes into account the solvent and membrane effects, we demonstrate that drug-target interactions are strengthened by pronounced polyvalent interactions catalyzed by the surface itself. These findings further enhance our understanding of antibiotic mode of action and will enable development of more effective therapies.

  5. Analytical Model of the Nonlinear Dynamics of Cantilever Tip-Sample Surface Interactions for Various Acoustic-Atomic Force Microscopies

    Science.gov (United States)

    Cantrell, John H., Jr.; Cantrell, Sean A.

    2008-01-01

    A comprehensive analytical model of the interaction of the cantilever tip of the atomic force microscope (AFM) with the sample surface is developed that accounts for the nonlinearity of the tip-surface interaction force. The interaction is modeled as a nonlinear spring coupled at opposite ends to linear springs representing cantilever and sample surface oscillators. The model leads to a pair of coupled nonlinear differential equations that are solved analytically using a standard iteration procedure. Solutions are obtained for the phase and amplitude signals generated by various acoustic-atomic force microscope (A-AFM) techniques including force modulation microscopy, atomic force acoustic microscopy, ultrasonic force microscopy, heterodyne force microscopy, resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM), and the commonly used intermittent contact mode (TappingMode) generally available on AFMs. The solutions are used to obtain a quantitative measure of image contrast resulting from variations in the Young modulus of the sample for the amplitude and phase images generated by the A-AFM techniques. Application of the model to RDF-AFUM and intermittent soft contact phase images of LaRC-cp2 polyimide polymer is discussed. The model predicts variations in the Young modulus of the material of 24 percent from the RDF-AFUM image and 18 percent from the intermittent soft contact image. Both predictions are in good agreement with the literature value of 21 percent obtained from independent, macroscopic measurements of sheet polymer material.

  6. Atomic forces between noble gas atoms, alkali ions, and halogen ions for surface interactions

    Science.gov (United States)

    Wilson, J. W.; Outlaw, R. A.; Heinbockel, J. H.

    1988-01-01

    The components of the physical forces between noble gas atoms, alkali ions, and halogen ions are analyzed and a data base developed from analysis of the two-body potential data, the alkali-halide molecular data, and the noble gas crystal and salt crystal data. A satisfactory global fit to this molecular and crystal data is then reproduced by the model to within several percent. Surface potentials are evaluated for noble gas atoms on noble gas surfaces and salt crystal surfaces with surface tension neglected. Within this context, the noble gas surface potentials on noble gas and salt crystals are considered to be accurate to within several percent.

  7. Effect of energy source, salt concentration and loading force on colloidal interactions between Acidithiobacillus ferrooxidans cells and mineral surfaces.

    Science.gov (United States)

    Diao, Mengxue; Nguyen, Tuan A H; Taran, Elena; Mahler, Stephen M; Nguyen, Anh V

    2015-08-01

    The surface appendages and extracellular polymeric substances of cells play an important role in the bacterial adhesion process. In this work, colloidal forces and nanomechanical properties of Acidithiobacillus ferrooxidans (A. f) interacted with silicon wafer and pyrite (FeS2) surfaces in solutions of varying salt concentrations were quantitatively examined using the bacterial probe technique with atomic force microscopy. A. f cells were cultured with either ferrous sulfate or elemental sulfur as key energy sources. Our results show that A. f cells grown with ferrous ion and elemental sulfur exhibit distinctive retraction force vs separation distance curves with stair-step and saw tooth shapes, respectively. During the approach of bacterial probes to the substrate surfaces, surface appendages and biopolymers of cells are sequentially compressed. The conformations of surface appendages and biopolymers are significantly influenced by the salt concentrations. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. MDM2-MDM4 molecular interaction investigated by atomic force spectroscopy and surface plasmon resonance.

    Science.gov (United States)

    Moscetti, Ilaria; Teveroni, Emanuela; Moretti, Fabiola; Bizzarri, Anna Rita; Cannistraro, Salvatore

    Murine double minute 2 (MDM2) and 4 (MDM4) are known as the main negative regulators of p53, a tumor suppressor. They are able to form heterodimers that are much more effective in the downregulation of p53. Therefore, the MDM2-MDM4 complex could be a target for promising therapeutic restoration of p53 function. To this aim, a deeper understanding of the molecular mechanisms underlining the heterodimerization is needed. The kinetic and thermodynamic characterization of the MDM2-MDM4 complex was performed with two complementary approaches: atomic force spectroscopy and surface plasmon resonance. Both techniques revealed an equilibrium dissociation constant (KD ) in the micromolar range for the MDM2-MDM4 heterodimer, similar to related complexes involved in the p53 network. Furthermore, the MDM2-MDM4 complex is characterized by a relatively high free energy, through a single energy barrier, and by a lifetime in the order of tens of seconds. New insights into the MDM2-MDM4 interaction could be highly important for developing innovative anticancer drugs focused on p53 reactivation.

  9. Using optical tweezers for measuring the interaction forces between human bone cells and implant surfaces: System design and force calibration

    International Nuclear Information System (INIS)

    Andersson, Martin; Madgavkar, Ashwin; Stjerndahl, Maria; Wu, Yanrong; Tan, Weihong; Duran, Randy; Niehren, Stefan; Mustafa, Kamal; Arvidson, Kristina; Wennerberg, Ann

    2007-01-01

    Optical tweezers were used to study the interaction and attachment of human bone cells to various types of medical implant materials. Ideally, the implant should facilitate cell attachment and promote migration of the progenitor cells in order to decrease the healing time. It is therefore of interest, in a controlled manner, to be able to monitor the cell adhesion process. Results from such studies would help foresee the clinical outcome of integrating medical implants. The interactions between two primary cell culture models, human gingival fibroblasts and bone forming human osteoblast cells, and three different implant materials, glass, titanium, and hydroxyapatite, were studied. A novel type of optical tweezers, which has a newly designed quadrant detector and a powerful 3 W laser was constructed and force calibrated using two different methods: one method in which the stiffness of the optical trap was obtained by monitoring the phase lag between the trap and the moved object when imposing a forced oscillation on the trapped object and another method in which the maximum trapping force was derived from the critical velocity at which the object escapes the trap. Polystyrene beads as well as cells were utilized for the calibrations. This is the first time that cells have been used directly for these types of force calibrations and, hence, direct measurements of forces exerted on cells can be performed, thus avoiding the difficulties often encountered when translating the results obtained from cell measurements to the calibrations obtained with reference materials. This more straightforward approach represents an advantage in comparison to established methods

  10. Atomic force microscopy studies of bioprocess engineering surfaces - imaging, interactions and mechanical properties mediating bacterial adhesion.

    Science.gov (United States)

    James, Sean A; Hilal, Nidal; Wright, Chris J

    2017-07-01

    The detrimental effect of bacterial biofilms on process engineering surfaces is well documented. Thus, interest in the early stages of bacterial biofilm formation; in particular bacterial adhesion and the production of anti-fouling coatings has grown exponentially as a field. During this time, Atomic force microscopy (AFM) has emerged as a critical tool for the evaluation of bacterial adhesion. Due to its versatility AFM offers not only insight into the topographical landscape and mechanical properties of the engineering surfaces, but elucidates, through direct quantification the topographical and biomechnical properties of the foulants The aim of this review is to collate the current research on bacterial adhesion, both theoretical and practical, and outline how AFM as a technique is uniquely equipped to provide further insight into the nanoscale world at the bioprocess engineering surface. Copyright © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Experimental and numerical modelling of surface water-groundwater flow and pollution interactions under tidal forcing

    Science.gov (United States)

    Spanoudaki, Katerina; Bockelmann-Evans, Bettina; Schaefer, Florian; Kampanis, Nikolaos; Nanou-Giannarou, Aikaterini; Stamou, Anastasios; Falconer, Roger

    2015-04-01

    Surface water and groundwater are integral components of the hydrologic continuum and the interaction between them affects both their quantity and quality. However, surface water and groundwater are often considered as two separate systems and are analysed independently. This separation is partly due to the different time scales, which apply in surface water and groundwater flows and partly due to the difficulties in measuring and modelling their interactions (Winter et al., 1998). Coastal areas in particular are a difficult hydrologic environment to represent with a mathematical model due to the large number of contributing hydrologic processes. Accurate prediction of interactions between coastal waters, groundwater and neighbouring wetlands, for example, requires the use of integrated surface water-groundwater models. In the past few decades a large number of mathematical models and field methods have been developed in order to quantify the interaction between groundwater and hydraulically connected surface water bodies. Field studies may provide the best data (Hughes, 1995) but are usually expensive and involve too many parameters. In addition, the interpretation of field measurements and linking with modelling tools often proves to be difficult. In contrast, experimental studies are less expensive and provide controlled data. However, experimental studies of surface water-groundwater interaction are less frequently encountered in the literature than filed studies (e.g. Ebrahimi et al., 2007; Kuan et al., 2012; Sparks et al., 2013). To this end, an experimental model has been constructed at the Hyder Hydraulics Laboratory at Cardiff University to enable measurements to be made of groundwater transport through a sand embankment between a tidal water body such as an estuary and a non-tidal water body such as a wetland. The transport behaviour of a conservative tracer was studied for a constant water level on the wetland side of the embankment, while running a

  12. Measuring Forces between Oxide Surfaces Using the Atomic Force Microscope

    DEFF Research Database (Denmark)

    Pedersen, Henrik Guldberg; Høj, Jakob Weiland

    1996-01-01

    The interactions between colloidal particles play a major role in processing of ceramics, especially in casting processes. With the Atomic Force Microscope (AFM) it is possible to measure the inter-action force between a small oxide particle (a few micron) and a surface as function of surface...

  13. Effect of airway surface liquid on the forces on the pharyngeal wall: Experimental fluid-structure interaction study.

    Science.gov (United States)

    Pirnar, Jernej; Širok, Brane; Bombač, Andrej

    2017-10-03

    Obstructive sleep apnoea syndrome (OSAS) is a breathing disorder with a multifactorial etiology. The respiratory epithelium is lined with a thin layer of airway surface liquid preventing interactions between the airflow and epithelium. The effect of the liquid lining in OSAS pathogenesis remains poorly understood despite clinical research. Previous studies have shown that the physical properties of the airway surface liquid or altered stimulation of the airway mechanoreceptors could alleviate or intensify OSAS; however, these studies do not provide a clear physical interpretation. To study the forces transmitted from the airflow to the liquid-lined compliant wall and to discuss the effects of the airway surface liquid properties on the stimulation of the mechanoreceptors, a novel and simplified experimental system mimicking the upper airway fundamental characteristics (i.e., liquid-lined compliant wall and complex unsteady airflow features) was constructed. The fluctuating force on the compliant wall was reduced through a damping mechanism when the liquid film thickness and/or the viscosity were increased. Conversely, the liquid film damping was reduced when the surface tension decreased. Based on the experimental data, empirical correlations were developed to predict the damping potential of the liquid film. In the future, this will enable us to extend the existing computational fluid-structure interaction simulations of airflow in the human upper airway by incorporating the airway surface liquid effect without adopting two-phase flow interface tracking methods. Furthermore, the experimental system developed in this study could be used to investigate the fundamental principles of the complex once/twice-coupled physical phenomena. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Force spectroscopy to understand cell surface receptor interactions in the immune system.

    NARCIS (Netherlands)

    Riet, J. te

    2010-01-01

    Since the invention of the atomic force microscope (AFM) in 1986, the application of the instrument has shifted from a pure physicist’s tool to a useful instrument for physicists, chemists and biologists. The AFM is not a classical microscope in the sense that light or electrons are used to obtain

  15. Roughness in Surface Force Measurements: Extension of DLVO Theory To Describe the Forces between Hafnia Surfaces.

    Science.gov (United States)

    Eom, Namsoon; Parsons, Drew F; Craig, Vincent S J

    2017-07-06

    The interaction between colloidal particles is commonly viewed through the lens of DLVO theory, whereby the interaction is described as the sum of the electrostatic and dispersion forces. For similar materials acting across a medium at pH values remote from the isoelectric point the theory typically involves an electrostatic repulsion that is overcome by dispersion forces at very small separations. However, the dominance of the dispersion forces at short separations is generally not seen in force measurements, with the exception of the interaction between mica surfaces. The discrepancy for silica surfaces has been attributed to hydration forces, but this does not explain the situation for titania surfaces where the dispersion forces are very much larger. Here, the interaction forces between very smooth hafnia surfaces have been measured using the colloid probe technique and the forces evaluated within the DLVO framework, including both hydration forces and the influence of roughness. The measured forces across a wide range of pH at different salt concentrations are well described with a single parameter for the surface roughness. These findings show that even small degrees of surface roughness significantly alter the form of the interaction force and therefore indicate that surface roughness needs to be included in the evaluation of surface forces between all surfaces that are not ideally smooth.

  16. MDM2–MDM4 molecular interaction investigated by atomic force spectroscopy and surface plasmon resonance

    Directory of Open Access Journals (Sweden)

    Moscetti I

    2016-08-01

    Full Text Available Ilaria Moscetti,1 Emanuela Teveroni,2,3 Fabiola Moretti,3 Anna Rita Bizzarri,1 Salvatore Cannistraro1 1Biophysics and Nanoscience Centre, Department DEB, Università della Tuscia, Viterbo, Italy; 2Department of Endocrinology and Metabolism, Università Cattolica di Roma, Roma, Italy; 3Institute of Cell Biology and Neurobiology, Consiglio Nazionale delle Ricerche (CNR, Roma, Italy Abstract: Murine double minute 2 (MDM2 and 4 (MDM4 are known as the main negative regulators of p53, a tumor suppressor. They are able to form heterodimers that are much more effective in the downregulation of p53. Therefore, the MDM2–MDM4 complex could be a target for promising therapeutic restoration of p53 function. To this aim, a deeper understanding of the molecular mechanisms underlining the heterodimerization is needed. The kinetic and thermodynamic characterization of the MDM2–MDM4 complex was performed with two complementary approaches: atomic force spectroscopy and surface plasmon resonance. Both techniques revealed an equilibrium dissociation constant (KD in the micromolar range for the MDM2–MDM4 heterodimer, similar to related complexes involved in the p53 network. Furthermore, the MDM2–MDM4 complex is characterized by a relatively high free energy, through a single energy barrier, and by a lifetime in the order of tens of seconds. New insights into the MDM2–MDM4 interaction could be highly important for developing innovative anticancer drugs focused on p53 reactivation. Keywords: MDM2, MDM4, atomic force spectroscopy, surface plasmon resonance

  17. MDM2–MDM4 molecular interaction investigated by atomic force spectroscopy and surface plasmon resonance

    Science.gov (United States)

    Moscetti, Ilaria; Teveroni, Emanuela; Moretti, Fabiola; Bizzarri, Anna Rita; Cannistraro, Salvatore

    2016-01-01

    Murine double minute 2 (MDM2) and 4 (MDM4) are known as the main negative regulators of p53, a tumor suppressor. They are able to form heterodimers that are much more effective in the downregulation of p53. Therefore, the MDM2–MDM4 complex could be a target for promising therapeutic restoration of p53 function. To this aim, a deeper understanding of the molecular mechanisms underlining the heterodimerization is needed. The kinetic and thermodynamic characterization of the MDM2–MDM4 complex was performed with two complementary approaches: atomic force spectroscopy and surface plasmon resonance. Both techniques revealed an equilibrium dissociation constant (KD) in the micromolar range for the MDM2–MDM4 heterodimer, similar to related complexes involved in the p53 network. Furthermore, the MDM2–MDM4 complex is characterized by a relatively high free energy, through a single energy barrier, and by a lifetime in the order of tens of seconds. New insights into the MDM2–MDM4 interaction could be highly important for developing innovative anticancer drugs focused on p53 reactivation. PMID:27621617

  18. Intermolecular and surface forces

    CERN Document Server

    Israelachvili, Jacob N

    2011-01-01

    This reference describes the role of various intermolecular and interparticle forces in determining the properties of simple systems such as gases, liquids and solids, with a special focus on more complex colloidal, polymeric and biological systems. The book provides a thorough foundation in theories and concepts of intermolecular forces, allowing researchers and students to recognize which forces are important in any particular system, as well as how to control these forces. This third edition is expanded into three sections and contains five new chapters over the previous edition.· starts fr

  19. Chemical Force Microscopy Study on the Interactions of COOH Functional Groups with Kaolinite Surfaces: Implications for Enhanced Oil Recovery

    Directory of Open Access Journals (Sweden)

    Nipada Santha

    2017-12-01

    Full Text Available Clay–oil interactions play a critical role in determining the wettability of sandstone oil reservoirs, which, in turn, governs the effectiveness of enhanced oil recovery methods. In this study, we have measured the adhesion between –COOH functional groups and the siloxane and aluminol faces of kaolinite clay minerals by means of chemical force microscopy as a function of pH, salinity (from 0.001 M to 1 M and cation identity (Na+ vs. Ca2+. Results from measurements on the siloxane face show that Ca2+ displays a reverse low-salinity effect (adhesion decreasing at higher concentrations at pH 5.5, and a low salinity effect at pH 8. At a constant Ca2+ concentration of 0.001 M, however, an increase in pH leads to larger adhesion. In contrast, a variation in the Na+ concentration showed less effect in varying the adhesion of –COOH groups to the siloxane face. Measurements on the aluminol face showed a reverse low-salinity effect at pH 5.5 in the presence of Ca2+, whereas an increase in pH with constant ion concentration resulted in a decrease in adhesion for both Ca2+ and Na+. Results are explained by looking at the kaolinite’s surface complexation and the protonation state of the functional group, and highlight a more important role of the multicomponent ion exchange mechanism in controlling adhesion than the double layer expansion mechanism.

  20. The evaluations of the influence of surface conductivity to the energy of particles in discharge channel and interaction force in contact charging process

    Energy Technology Data Exchange (ETDEWEB)

    Alisoy, H.Z. [Department of Electric and Electronics Engineering, Inonu University, 44280 Malatya (Turkey)]. E-mail: halis@inonu.edu.tr; Alisoy, G.T. [Department of Mathematics Education, Inonu University, 44280 Malatya (Turkey); Sahin, A. [Department of Physics, Inonu University, 44280 Malatya (Turkey); Yeroglu, C. [Department of Electric and Electronics Engineering, Inonu University, 44280 Malatya (Turkey)

    2006-12-18

    In this Letter, we present some analytical expressions by using the equations of electric field, inside and outside of a cylindrical void, taking the surface conductivity into consideration. We apply the obtained expressions to the high voltage insulation and ion electron technology, such as: (i) energies of charged particles occurring in discharge channel in accordance with Townsend approach; (ii) interaction force between the dielectric particle and the electrode for DC and AC cases.

  1. Laser-surface interactions

    CERN Document Server

    Ganeev, Rashid A

    2014-01-01

    This book is about the interaction of laser radiation with various surfaces at variable parameters of radiation. As a basic principle of classification we chose the energetic or intensity level of interaction of laser radiation with the surfaces. These two characteristics of laser radiation are the most important parameters defining entire spectrum of the processes occurring on the surfaces during interaction with electromagnetic waves. This is a first book containing a whole spectrum of the laser-surface interactions distinguished by the ranges of used laser intensity. It combines the surface response starting from extremely weak laser intensities (~1 W cm-2) up to the relativistic intensities (~1020 W cm-2 and higher). The book provides the basic information about lasers and acquaints the reader with both common applications of laser-surface interactions (laser-related printers, scanners, barcode readers, discs, material processing, military, holography, medicine, etc) and unusual uses of the processes on t...

  2. Forces due to surface water measured by force microscopy. Consequences for anchoring biological cells to surfaces

    International Nuclear Information System (INIS)

    Schilcher, K.

    1997-05-01

    Interaction forces in 'Scanning Force Microscopy' (SFM). Force curves revealed exponentially decaying, attractive forces between silicon tip and silicon sample in aqueous media. Replacing the silicon sample by a sheet of mica, the interaction forces had both, an attractive and a repulsive component. Addition of salts generally reduced the forces. At 500 mM salt concentration, the attractive force became quantized with a residual force value of 23 pN. The attractive force is attributed to the gain in energy of water molecules which are released from surface water into free water during tip-sample approach. This conclusion is supported by a statistical model. The repulsive force contribution in the case of mica, is caused by hydration forces due to the spatial organization of crystalline water on the mica surface. Anchoring of biological cells. Molecular resolution of cell surfaces by SFM requires cell anchoring without interference with cell physiology. For this a novel strategy, 'hydrophobic anchoring' was designed. It avoids strong attractive forces between cell and by using a flexible spacer molecule. It establishes anchoring by a lipid (bound to the spacer), which weakly interacts with the hydrophobic core of the cell membrane. The method was subjected to tests using RBL-2H3, CH0 αβ and HEK-293 cells. The strength of cell anchoring was assayed by shear forces. In all cases 'hydrophobic anchoring' via a spacer caused elective anchoring much beyond controls. Such cell anchoring was employed for the imaging of RBL-2H3 cells by SFM. Images showed considerable finer details than images of loosely adsorbed cells. With about 50 rim resolution, SFM succeeded in imaging microvilli, filopodia, single cytoskeletal fibers (microtubules, microfilaments) and vesicles. In addition, as a consequence of cell stimulation upon ionomycin treatment, lamellae formation and the appearance of secretory granules on top of them were observed which indicates the viability of anchored

  3. Probing Anisotropic Surface Properties and Surface Forces of Fluorite Crystals.

    Science.gov (United States)

    Gao, Zhiyong; Xie, Lei; Cui, Xin; Hu, Yuehua; Sun, Wei; Zeng, Hongbo

    2018-02-20

    Fluorite is the most important mineral source for producing fluorine-based chemicals and materials in a wide range of engineering and technological applications. In this work, atomic force microscopy was employed, for the first time, to probe the surface interactions and adhesion energy of model oleic acid (a commonly used surface modification organics for fluorite) molecules on fluorite surfaces with different orientations in both air and aqueous solutions at different pH conditions. Fitted with the Derjaguin-Landau-Verwey-Overbeek theory, the force results during surface approaching demonstrate the anisotropy in the surface charge of different orientations, with the {111} surface exhibiting a higher magnitude of surface charge, which could be attributed to the difference in the atomic composition. The adhesion measured during surface retraction shows that model oleic acid molecules have a stronger adhesion with the {100} surface than with the {111} surface in both air and aqueous solutions. The anisotropic adhesion energy was analyzed in relation to the surface atom (especially calcium) activity, which was supported by the surface free energy results calculated based on a three-probe-liquid method. Each calcium atom on the {100} surface with four dangling bonds is more active than the calcium atom on the {111} surface with only one dangling bond, supported by a larger value of the Lewis acid component for the {100} surface. The model oleic acid molecules present in the ionic form at pH 9 exhibit a higher adhesion energy with fluorite surfaces as compared to their molecular form at pH 6, which was related to the surface activity of different forms. The adhesion energy measured in solution is much lower than that in air, indicating that the solvent exerts an important influence on the interactions of organic molecules with mineral surfaces. The results provide useful information on the fundamental understanding of surface interactions and adhesion energy of organic

  4. Acetic acid mediated interactions between alumina surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Kimiyasu, E-mail: sato.kimiyasu@aist.go.jp [National Institute of Advanced Industrial Science and Technology (AIST), Anagahora 2266-98, Shimoshidami, Moriyama-ku, Nagoya 463-8560 (Japan); Y Latin-Small-Letter-Dotless-I lmaz, Hueseyin [National Institute of Advanced Industrial Science and Technology (AIST), Anagahora 2266-98, Shimoshidami, Moriyama-ku, Nagoya 463-8560 (Japan); Gebze Institute of Technology, Materials Science and Engineering Department, 41400, Gebze-Kocaeli (Turkey); Ijuin, Atsuko; Hotta, Yuji; Watari, Koji [National Institute of Advanced Industrial Science and Technology (AIST), Anagahora 2266-98, Shimoshidami, Moriyama-ku, Nagoya 463-8560 (Japan)

    2012-02-01

    Low-molecular-weight organic acids have been known to modify colloidal stability of alumina-based suspensions. We investigated interaction forces between alumina surfaces mediated by acetic acid which is one of the simplest organic acids. Forces between alumina surfaces were measured using the colloid-probe method of atomic force microscope (AFM). Repulsive forces attributed to steric repulsion due to adsorbed molecules and electrostatic repulsion dominated the interaction. Results of rheological characterization of the alumina slurry containing acetic acid supported the finding.

  5. Interaction Force Estimation During Manipulation of Microparticles

    NARCIS (Netherlands)

    Khalil, I.S.M.; Metz, R.M.P.; Abelmann, Leon; Misra, Sarthak

    2012-01-01

    This work investigates the utilization of microparticles for the wireless sensing of interaction forces in magneticbased manipulation systems. The proposed force estimation approach allows for using microparticles in sensing the interaction forces at hard-to-reach regions to avoid the mechanical and

  6. Theoretical Models for Surface Forces and Adhesion and Their Measurement Using Atomic Force Microscopy

    Science.gov (United States)

    Leite, Fabio L.; Bueno, Carolina C.; Da Róz, Alessandra L.; Ziemath, Ervino C.; Oliveira, Osvaldo N.

    2012-01-01

    The increasing importance of studies on soft matter and their impact on new technologies, including those associated with nanotechnology, has brought intermolecular and surface forces to the forefront of physics and materials science, for these are the prevailing forces in micro and nanosystems. With experimental methods such as the atomic force spectroscopy (AFS), it is now possible to measure these forces accurately, in addition to providing information on local material properties such as elasticity, hardness and adhesion. This review provides the theoretical and experimental background of AFS, adhesion forces, intermolecular interactions and surface forces in air, vacuum and in solution. PMID:23202925

  7. Theoretical models for surface forces and adhesion and their measurement using atomic force microscopy.

    Science.gov (United States)

    Leite, Fabio L; Bueno, Carolina C; Da Róz, Alessandra L; Ziemath, Ervino C; Oliveira, Osvaldo N

    2012-10-08

    The increasing importance of studies on soft matter and their impact on new technologies, including those associated with nanotechnology, has brought intermolecular and surface forces to the forefront of physics and materials science, for these are the prevailing forces in micro and nanosystems. With experimental methods such as the atomic force spectroscopy (AFS), it is now possible to measure these forces accurately, in addition to providing information on local material properties such as elasticity, hardness and adhesion. This review provides the theoretical and experimental background of afs, adhesion forces, intermolecular interactions and surface forces in air, vacuum and in solution.

  8. Tritium-surface interactions

    International Nuclear Information System (INIS)

    Kirkaldy, J.S.

    1983-06-01

    The report deals broadly with tritium-surface interactions as they relate to a fusion power reactor enterprise, viz., the vacuum chamber, first wall, peripherals, pumping, fuel recycling, isotope separation, repair and maintenance, decontamination and safety. The main emphasis is on plasma-surface interactions and the selection of materials for fusion chamber duty. A comprehensive review of the international (particularly U.S.) research and development is presented based upon a literature review (about 1 000 reports and papers) and upon visits to key laboratories, Sandia, Albuquerque, Sandia, Livermore and EGβG Idaho. An inventory of Canadian expertise and facilities for RβD on tritium-surface interactions is also presented. A number of proposals are made for the direction of an optimal Canadian RβD program, emphasizing the importance of building on strength in both the technological and fundamental areas. A compendium of specific projects and project areas is presented dealing primarily with plasma-wall interactions and permeation, anti-permeation materials and surfaces and health, safety and environmental considerations. Potential areas of industrial spinoff are identified

  9. Preparation of stable silica surfaces for surface forces measurement

    Science.gov (United States)

    Ren, Huai-Yin; Mizukami, Masashi; Kurihara, Kazue

    2017-09-01

    A surface forces apparatus (SFA) measures the forces between two surfaces as a function of the surface separation distance. It is regarded as an essential tool for studying the interactions between two surfaces. However, sample surfaces used for the conventional SFA measurements have been mostly limited to thin (ca. 2-3 μm) micas, which are coated with silver layers (ca. 50 nm) on their back, due to the requirement of the distance determination by transmission mode optical interferometry called FECO (fringes of equal chromatic order). The FECO method has the advantage of determining the absolute distance, so it should be important to increase the availability of samples other than mica, which is chemically nonreactive and also requires significant efforts for cleaving. Recently, silica sheets have been occasionally used in place of mica, which increases the possibility of surface modification. However, in this case, the silver layer side of the sheet is glued on a cylindrical quartz disc using epoxy resin, which is not stable in organic solvents and can be easily swollen or dissolved. The preparation of substrates more stable under severe conditions, such as in organic solvents, is necessary for extending application of the measurement. In this study, we report an easy method for preparing stable silica layers of ca. 2 μm in thickness deposited on gold layers (41 nm)/silica discs by sputtering, then annealed to enhance the stability. The obtained silica layers were stable and showed no swelling in organic solvents such as ethanol and toluene.

  10. Lectin interactions on surface-grafted glycostructures: influence of the spatial distribution of carbohydrates on the binding kinetics and rupture forces.

    Science.gov (United States)

    Yu, Kai; Creagh, A Louise; Haynes, Charles A; Kizhakkedathu, Jayachandran N

    2013-08-20

    We performed quantitative analysis of the binding kinetics and affinity of carbohydrate-lectin binding and correlated them directly with the molecular and structural features of ligands presented at the nanoscale within the glycocalyx mimicking layers on surfaces. The surface plasmon resonance analysis identified that the mode of binding changed from multivalent to monovalent, which resulted in a near 1000-fold change in the equilibrium association constant, by varying the spatial distribution of carbohydrate ligands within the surface-grafted polymer layer. We identified, for the first time, that the manner in which the ligands presented on the surface has great influence on the binding at the first stage of bivalent chelating, not on the binding at the second stage. The rupture forces measured by atomic force microscope force spectroscopy also indicated that the mode of binding between lectin and ligands changed from multiple to single with variation in the ligand presentation. The dependence of lectin binding on the glycopolymer composition and grafting density is directly correlated with the nanoscale presentation of ligands on a surface, which is a determining factor in controlling the clustering and statistical effects contributing to the enhanced binding.

  11. Nanoscale effects in the characterization of viscoelastic materials with atomic force microscopy: coupling of a quasi-three-dimensional standard linear solid model with in-plane surface interactions.

    Science.gov (United States)

    Solares, Santiago D

    2016-01-01

    Significant progress has been accomplished in the development of experimental contact-mode and dynamic-mode atomic force microscopy (AFM) methods designed to measure surface material properties. However, current methods are based on one-dimensional (1D) descriptions of the tip-sample interaction forces, thus neglecting the intricacies involved in the material behavior of complex samples (such as soft viscoelastic materials) as well as the differences in material response between the surface and the bulk. In order to begin to address this gap, a computational study is presented where the sample is simulated using an enhanced version of a recently introduced model that treats the surface as a collection of standard-linear-solid viscoelastic elements. The enhanced model introduces in-plane surface elastic forces that can be approximately related to a two-dimensional (2D) Young's modulus. Relevant cases are discussed for single- and multifrequency intermittent-contact AFM imaging, with focus on the calculated surface indentation profiles and tip-sample interaction force curves, as well as their implications with regards to experimental interpretation. A variety of phenomena are examined in detail, which highlight the need for further development of more physically accurate sample models that are specifically designed for AFM simulation. A multifrequency AFM simulation tool based on the above sample model is provided as supporting information.

  12. Recent advances in the surface forces apparatus (SFA) technique

    Science.gov (United States)

    Israelachvili, J.; Min, Y.; Akbulut, M.; Alig, A.; Carver, G.; Greene, W.; Kristiansen, K.; Meyer, E.; Pesika, N.; Rosenberg, K.; Zeng, H.

    2010-03-01

    The surface forces apparatus (SFA) has been used for many years to measure the physical forces between surfaces, such as van der Waals (including Casimir) and electrostatic forces in vapors and liquids, adhesion and capillary forces, forces due to surface and liquid structure (e.g. solvation and hydration forces), polymer, steric and hydrophobic interactions, bio-specific interactions as well as friction and lubrication forces. Here we describe recent developments in the SFA technique, specifically the SFA 2000, its simplicity of operation and its extension into new areas of measurement of both static and dynamic forces as well as both normal and lateral (shear and friction) forces. The main reason for the greater simplicity of the SFA 2000 is that it operates on one central simple-cantilever spring to generate both coarse and fine motions over a total range of seven orders of magnitude (from millimeters to ångstroms). In addition, the SFA 2000 is more spacious and modulated so that new attachments and extra parts can easily be fitted for performing more extended types of experiments (e.g. extended strain friction experiments and higher rate dynamic experiments) as well as traditionally non-SFA type experiments (e.g. scanning probe microscopy and atomic force microscopy) and for studying different types of systems.

  13. Evaluation of single-cell force spectroscopy and fluorescence microscopy to determine cell interactions with femtosecond-laser microstructured titanium surfaces.

    Science.gov (United States)

    Aliuos, Pooyan; Fadeeva, Elena; Badar, Muhammad; Winkel, Andreas; Mueller, Peter P; Warnecke, Athanasia; Chichkov, Boris; Lenarz, Thomas; Reich, Uta; Reuter, Guenter

    2013-04-01

    One goal in biomaterials research is to limit the formation of connective tissue around the implant. Antiwetting surfaces are known to reduce ability of cells to adhere. Such surfaces can be achieved by special surface structures (lotus effect). Aim of the study was to investigate the feasibility for creating antiwetting surface structures on titanium and to characterize their effect on initial cell adhesion and proliferation. Titanium microstructures were generated using femtosecond- (fs-) laser pulses. Murine fibroblasts served as a model for connective tissue cells. Quantitative investigation of initial cell adhesion was performed using atomic force microscopy. Fluorescence microscopy was used for the characterization of cell-adhesion pattern, cell morphology, and proliferation. Water contact angle (WCA) measurements evinced antiwetting properties of laser-structured surfaces. However, the WCA was decreased in serum-containing medium. Initial cell adhesion to microstructured titanium was significantly promoted when compared with polished titanium. Microstructures did not influence cell proliferation on titanium surfaces. However, on titanium microstructures, cells showed a flattened morphology, and the cell orientation was biased according to the surface topography. In conclusion, antiwetting properties of surfaces were absent in the presence of serum and did not hinder adhesion and proliferation of NIH 3T3 fibroblasts. Copyright © 2012 Wiley Periodicals, Inc.

  14. Capacitance dilatometry in a surface force apparatus

    International Nuclear Information System (INIS)

    Stewart, A.M.

    2003-01-01

    Full text: A variant of the surface force apparatus has been developed which enables measurements of the forces between opaque surfaces to be obtained. A capacitance dilatometry attachment for the surface force apparatus has been constructed in which the surface that moves under the influence of the applied force is attached to one plate of a capacitor whose capacitance thereby changes. In order to detect movements of 0.1 nm of the plates of a capacitor with gap 0.1 mm the capacitance has to be measured to one part in one million, noting further that the measured capacitance is several hundred times smaller than the associated stray capacitances. This resolution is achieved by means of a transformer ratio bridge and, provided that adequate vibration isolation can be achieved, displacements of 0.1 nm can be resolved reliably. This is the case even with air between the surfaces, air giving much less vibrational damping than liquids. The method has been applied to measure the forces between mica in electrolyte and to measure dispersion forces of mica and silica in air. In the latter case the results are of unprecedented accuracy for this technique and show unambiguously that for surface separations greater than 10 nm the retarded form of the dispersion force fits the measurements much better than the non-retarded form

  15. Modeling noncontact atomic force microscopy resolution on corrugated surfaces

    Directory of Open Access Journals (Sweden)

    Kristen M. Burson

    2012-03-01

    Full Text Available Key developments in NC-AFM have generally involved atomically flat crystalline surfaces. However, many surfaces of technological interest are not atomically flat. We discuss the experimental difficulties in obtaining high-resolution images of rough surfaces, with amorphous SiO2 as a specific case. We develop a quasi-1-D minimal model for noncontact atomic force microscopy, based on van der Waals interactions between a spherical tip and the surface, explicitly accounting for the corrugated substrate (modeled as a sinusoid. The model results show an attenuation of the topographic contours by ~30% for tip distances within 5 Å of the surface. Results also indicate a deviation from the Hamaker force law for a sphere interacting with a flat surface.

  16. Surface forces between rough and topographically structured interfaces

    DEFF Research Database (Denmark)

    Thormann, Esben

    2017-01-01

    and manufactured materials, which possess topographical variations. Further, with technological advances in nanotechnology, fabrication of nano- or micro-structured surfaces has become increasingly important for many applications, which calls for a better understanding of the effect of surface topography...... on the interaction between interfaces. This paper presents a review of the current state of understanding of the effect of surface roughness on DLVO forces, as well as on the interactions between topographically structured hydrophobic surfaces in water. While the first case is a natural choice because it represents...

  17. Force interactions between magnetite, silica, and bentonite studied with atomic force microscopy

    Science.gov (United States)

    Dobryden, I.; Potapova, E.; Holmgren, A.; Weber, H.; Hedlund, J.; Almqvist, N.

    2015-04-01

    Iron ore pellets consist of variety of mineral particles and are an important refined product used in steel manufacturing. Production of high-quality pellets requires good understanding of interactions between different constituents, such as magnetite, gangue residues, bentonite, and additives. Much research has been reported on magnetite, silica, and bentonite surface properties and their effect on pellet strength but more scant with a focus on a fundamental particle-particle interaction. To probe such particle interaction, atomic force microscopy (AFM) using colloidal probe technique has proven to be a suitable tool. In this work, the measurements were performed between magnetite-magnetite, bentonite-magnetite, silica-bentonite, and silica-magnetite particles in 1 mM CaCl2 solution at various pH values. The interaction character, i.e., repulsion or attraction, was determined by measuring and analyzing AFM force curves. The observed quantitative changes in interaction forces were in good agreement with the measured zeta-potentials for the particles at the same experimental conditions. Particle aggregation was studied by measuring the adhesion force. Absolute values of adhesion forces for different systems could not be compared due to the difference in particle size and contact geometry. Therefore, the relative change of adhesion force between pH 6 and 10 was used for comparison. The adhesion force decreased for the magnetite-magnetite and bentonite-silica systems and slightly increased for the magnetite-bentonite system at pH 10 as compared to pH 6, whereas a pronounced decrease in adhesion force was observed in the magnetite-silica system. Thus, the presence of silica particles on the magnetite surface could have a negative impact on the interaction between magnetite and bentonite in balling due to the reduction of the adhesion force.

  18. Plasma-surface interactions

    International Nuclear Information System (INIS)

    Goeckner, M J; Nelson, C T; Sant, S P; Jindal, A K; Joseph, E A; Zhou, B S; Padron-Wells, G; Jarvis, B; Pierce, R; Overzet, L J

    2008-01-01

    Materials processing is at a crossroads. Currently a large fraction of industrially viable materials processing is via plasmas. Until recently it has been economical to just examine the influence the plasma properties on the desired surface processes and through this ultimately optimize manufacturing. For example, it is well known that the surface processes (etch or deposition), occur in the top few mono-layers of the surface. Thus, in film growth one requires that molecules from the gas-phase land and bond on the surface. However as processing has reached the nano-scale, development of viable processes has become more and more difficult. In part, this is because of all of the free parameters that exist in plasmas. To overcome this economic issue, tool vendors and semiconductor companies have turned to complex computational models of processing plasmas. For those models to work, one requires a through understanding of all of the gas-phase and surface-phase processes that are exhibited in plasmas. Unfortunately, these processes, particularly those at the surface, are not well understood. In this article we describe a viable model of the surface-phase based on cross sections for processes that occur. While originally developed of fluorocarbon systems, the model also appears to be applicable to hydrocarbon systems.

  19. Optical Near-field Interactions and Forces for Optoelectronic Devices

    Science.gov (United States)

    Kohoutek, John Michael

    Throughout history, as a particle view of the universe began to take shape, scientists began to realize that these particles were attracted to each other and hence came up with theories, both analytical and empirical in nature, to explain their interaction. The interaction pair potential (empirical) and electromagnetics (analytical) theories, both help to explain not only the interaction between the basic constituents of matter, such as atoms and molecules, but also between macroscopic objects, such as two surfaces in close proximity. The electrostatic force, optical force, and Casimir force can be categorized as such forces. A surface plasmon (SP) is a collective motion of electrons generated by light at the interface between two mediums of opposite signs of dielectric susceptibility (e.g. metal and dielectric). Recently, surface plasmon resonance (SPR) has been exploited in many areas through the use of tiny antennas that work on similar principles as radio frequency (RF) antennas in optoelectronic devices. These antennas can produce a very high gradient in the electric field thereby leading to an optical force, similar in concept to the surface forces discussed above. The Atomic Force Microscope (AFM) was introduced in the 1980s at IBM. Here we report on its uses in measuring these aforementioned forces and fields, as well as actively modulating and manipulating multiple optoelectronic devices. We have shown that it is possible to change the far field radiation pattern of an optical antenna-integrated device through modification of the near-field of the device. This modification is possible through change of the local refractive index or reflectivity of the "hot spot" of the device, either mechanically or optically. Finally, we have shown how a mechanically active device can be used to detect light with high gain and low noise at room temperature. It is the aim of several of these integrated and future devices to be used for applications in molecular sensing

  20. Synergistic effects in plasma surface interactions

    International Nuclear Information System (INIS)

    Roberto, J.B.; Behrisch, R.

    1984-01-01

    The possible synergistic effects which can contribute to plasma surface interaction phenomena in fusion devices are reviewed. These effects include the influence of reactive ions, surface modification, temperature, radiation damage, and external forces and fields on erosion yields, hydrogen retention and release, and other surface processes. The important synergistic effects are described in terms of surface and edge conditions encountered in present fusion devices and expected in future reactors. Priority data needs include the chemical erosion of graphite at high particle fluxes, melt-layer stability under disruption-induced eddy current forces, the influence of bulk neutron damage on hydrogen retention, and an in-situ evaluation of synergistic effects in operating fusion devices

  1. Nitrogen interactions at metal surfaces

    NARCIS (Netherlands)

    Gleeson, M.A.; Kleijn, A.W.

    2013-01-01

    Molecular beam experiments with specially prepared beams allow the study of the interaction of very reactive species with surfaces. In the present case the interaction of N-atoms with Ag(1 1 1) is studied. The energy of the atoms is around 5 eV, precisely between the classical energy regimes of

  2. Probing surfaces with single-polymer atomic force microscope experiments.

    Science.gov (United States)

    Friedsam, C; Gaub, H E; Netz, R R

    2006-03-01

    In the past 15 years atomic force microscope (AFM) based force spectroscopy has become a versatile tool to study inter- and intramolecular interactions of single polymer molecules. Irreversible coupling of polymer molecules between the tip of an AFM cantilever and the substrate allows one to study the stretching response up to the high force regime of several nN. For polymers that glide or slip laterally over the surface with negligible friction, on the other hand, the measured force profiles exhibit plateaus which allow one to extract the polymer adsorption energies. Long-term stable polymer coatings of the AFM tips allow for the possibility of repeating desorption experiments from solid supports with individual molecules many times, yielding good sampling statistics and thus reliable estimates for adsorption energies. In combination with recent advances in theoretical modeling, a detailed picture of the conformational statistics, backbone elasticity, and the adsorption characteristics of single polymer molecules is obtained.

  3. Modelling land surface - atmosphere interactions

    DEFF Research Database (Denmark)

    Rasmussen, Søren Højmark

    related to inaccurate land surface modelling, e.g. enhanced warm bias in warm dry summer months. Coupling the regional climate model to a hydrological model shows the potential of improving the surface flux simulations in dry periods and the 2 m air temperature in general. In the dry periods......The study is investigates modelling of land surface – atmosphere interactions in context of fully coupled climatehydrological model. With a special focus of under what condition a fully coupled model system is needed. Regional climate model inter-comparison projects as ENSEMBLES have shown bias...

  4. Collaboration Meets Interactive Surfaces (CMIS)

    DEFF Research Database (Denmark)

    Anslow, Craig; Campos, Pedro; Grisoni, Laurent

    2015-01-01

    This workshop proposes to bring together researchers who are interested in improving collaborative experiences through the combination of multiple interaction surfaces with diverse sizes and formats, ranging from large-scale walls, to tables, mobiles, and wearables. The opportunities for innovati...

  5. Modelling land surface - atmosphere interactions

    DEFF Research Database (Denmark)

    Rasmussen, Søren Højmark

    The study is investigates modelling of land surface – atmosphere interactions in context of fully coupled climatehydrological model. With a special focus of under what condition a fully coupled model system is needed. Regional climate model inter-comparison projects as ENSEMBLES have shown bias...

  6. Distinguishing magnetic and electrostatic interactions by a Kelvin probe force microscopy-magnetic force microscopy combination.

    Science.gov (United States)

    Jaafar, Miriam; Iglesias-Freire, Oscar; Serrano-Ramón, Luis; Ibarra, Manuel Ricardo; de Teresa, Jose Maria; Asenjo, Agustina

    2011-01-01

    The most outstanding feature of scanning force microscopy (SFM) is its capability to detect various different short and long range interactions. In particular, magnetic force microscopy (MFM) is used to characterize the domain configuration in ferromagnetic materials such as thin films grown by physical techniques or ferromagnetic nanostructures. It is a usual procedure to separate the topography and the magnetic signal by scanning at a lift distance of 25-50 nm such that the long range tip-sample interactions dominate. Nowadays, MFM is becoming a valuable technique to detect weak magnetic fields arising from low dimensional complex systems such as organic nanomagnets, superparamagnetic nanoparticles, carbon-based materials, etc. In all these cases, the magnetic nanocomponents and the substrate supporting them present quite different electronic behavior, i.e., they exhibit large surface potential differences causing heterogeneous electrostatic interaction between the tip and the sample that could be interpreted as a magnetic interaction. To distinguish clearly the origin of the tip-sample forces we propose to use a combination of Kelvin probe force microscopy (KPFM) and MFM. The KPFM technique allows us to compensate in real time the electrostatic forces between the tip and the sample by minimizing the electrostatic contribution to the frequency shift signal. This is a great challenge in samples with low magnetic moment. In this work we studied an array of Co nanostructures that exhibit high electrostatic interaction with the MFM tip. Thanks to the use of the KPFM/MFM system we were able to separate the electric and magnetic interactions between the tip and the sample.

  7. Distinguishing magnetic and electrostatic interactions by a Kelvin probe force microscopy–magnetic force microscopy combination

    Directory of Open Access Journals (Sweden)

    Miriam Jaafar

    2011-09-01

    Full Text Available The most outstanding feature of scanning force microscopy (SFM is its capability to detect various different short and long range interactions. In particular, magnetic force microscopy (MFM is used to characterize the domain configuration in ferromagnetic materials such as thin films grown by physical techniques or ferromagnetic nanostructures. It is a usual procedure to separate the topography and the magnetic signal by scanning at a lift distance of 25–50 nm such that the long range tip–sample interactions dominate. Nowadays, MFM is becoming a valuable technique to detect weak magnetic fields arising from low dimensional complex systems such as organic nanomagnets, superparamagnetic nanoparticles, carbon-based materials, etc. In all these cases, the magnetic nanocomponents and the substrate supporting them present quite different electronic behavior, i.e., they exhibit large surface potential differences causing heterogeneous electrostatic interaction between the tip and the sample that could be interpreted as a magnetic interaction. To distinguish clearly the origin of the tip–sample forces we propose to use a combination of Kelvin probe force microscopy (KPFM and MFM. The KPFM technique allows us to compensate in real time the electrostatic forces between the tip and the sample by minimizing the electrostatic contribution to the frequency shift signal. This is a great challenge in samples with low magnetic moment. In this work we studied an array of Co nanostructures that exhibit high electrostatic interaction with the MFM tip. Thanks to the use of the KPFM/MFM system we were able to separate the electric and magnetic interactions between the tip and the sample.

  8. Interactive Design of Developable Surfaces

    KAUST Repository

    Tang, Chengcheng

    2016-01-15

    We present a new approach to geometric modeling with developable surfaces and the design of curved-creased origami. We represent developables as splines and express the nonlinear conditions relating to developability and curved folds as quadratic equations. This allows us to utilize a constraint solver, which may be described as energy-guided projection onto the constraint manifold, and which is fast enough for interactive modeling. Further, a combined primal-dual surface representation enables us to robustly and quickly solve approximation problems.

  9. Friction and Adhesion Forces of Bacillus thuringiensis Spores on Planar Surfaces in Atmospheric Systems

    Energy Technology Data Exchange (ETDEWEB)

    Kweon, Hyojin [Georgia Inst. of Technology, Atlanta, GA (United States); Yiacoumi, Sotira [Georgia Inst. of Technology, Atlanta, GA (United States); Tsouris, Costas [Georgia Inst. of Technology, Atlanta, GA (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2011-11-07

    The kinetic friction force and the adhesion force of Bacillus thuringiensis spores on planar surfaces in atmospheric systems were studied using atomic force microscopy. The influence of relative humidity (RH) on these forces varied for different surface properties including hydrophobicity, roughness, and surface charge. The friction force of the spore was greater on a rougher surface than on mica, which is atomically flat. As RH increases, the friction force of the spores decreases on mica whereas it increases on rough surfaces. The influence of RH on the interaction forces between hydrophobic surfaces is not as strong as for hydrophilic surfaces. The friction force of the spore is linear to the sum of the adhesion force and normal load on the hydrophobic surface. In conclusion, the poorly defined surface structure of the spore and the adsorption of contaminants from the surrounding atmosphere are believed to cause a discrepancy between the calculated and measured adhesion forces.

  10. Direct Visualization of Dynamic Protein-DNA Interactions with a Dedicated Atomic Force Microscope

    NARCIS (Netherlands)

    van Noort, S.J.T.; van der Werf, Kees; Eker, Andre P.M.; Wyman, Claire; de Grooth, B.G.; van Hulst, N.F.; Greve, Jan

    1998-01-01

    Photolyase DNA interactions and the annealing of restriction fragment ends are directly visualized with the atomic force microscope (AFM). To be able to interact with proteins, DNA must be loosely bound to the surface. When MgCl2 is used to immobilize DNA to mica, DNA is attached to the surface at

  11. Interactions between acid- and base-functionalized surfaces

    NARCIS (Netherlands)

    Giesbers, M.; Kleijn, J.M.; Cohen Stuart, M.A.

    2002-01-01

    In this paper we present an AFM force study on interactions between chemically modified surfaces. Surfaces with terminal groups of either NH2 or COOH were obtained by chemisorption of a silane-based compound (3-amino-propyltriethoxysilane) on silica or a thiol compound (11-mercapto undecanoic acid)

  12. Surface Force of Polystyrene Latex Particles in Aqueous Anionic Amphipathic Solutions

    Science.gov (United States)

    Fujii, Masatoshi; Hamochi, Nagisa; Kato, Tadashi

    2008-07-01

    The surface forces between a polystyrene particle (negatively charged surface) of latex and a flat silica plate for several concentrations of aqueous solution of anionic amphipathic molecules (sodium dodecylsulfonate) were investigated using an atomic force microscope (AFM) colloidal probe method. In the lower concentration region approximately 1-2 mM, the surface force showed general repulsive profiles according to normal Derjaguin-Landau-Verwey-Overbeek (DLVO) theory between the surfaces having the same sign of surface charge under an electrolyte aqueous solution. While in the higher concentration region at less than the critical micelle concentration (cmc), the surface force showed attractive profiles. Findings suggest that the anionic amphipathic molecules adsorbed to the polystyrene particle in the higher concentration region and induced changes in the surface morphology and properties of the surface region. The change in the surface morphology is believed to be one of the origins of the attractive interaction.

  13. Surface chemical reactions probed with scanning force microscopy

    NARCIS (Netherlands)

    Werts, M.P L; van der Vegte, E.W.; Hadziioannou, G

    1997-01-01

    In this letter we report the study of surface chemical reactions with scanning force microscopy (SFM) with chemical specificity. Using chemically modified SFM probes, we can determine the local surface reaction conversion during a chemical surface modification. The adhesion forces between a

  14. Dependency of micro particle adhesion of dispersive and nondispersive interactions analyzed by atomic force microscopy

    CERN Document Server

    Kawal, A; Andoh, E

    1999-01-01

    The adhesion behaviour of a micro semi-sphere tip (radius of curvature of 18 nm) after making contact with various inorganic solid surfaces is analyzed. Measurement force by the AFM tip corresponds to the interactive force estimated $9 using surface energy components, dispersion and nondispersion, based on van der Waal's interaction. These components can be obtained by measuring the contact angle of standard liquids on a material surface. By using two kinds of tip $9 with different component values, analysis of the interactive mechanism and prediction of macro tip (particle) adhesion can be made. (6 refs).

  15. Predicting wind farm wake interaction with RANS: an investigation of the Coriolis force

    DEFF Research Database (Denmark)

    van der Laan, Paul; Hansen, Kurt Schaldemose; Sørensen, Niels N.

    2015-01-01

    A Reynolds-averaged Navier-Stokes code is used to simulate the interaction of two neighboring wind farms. The influence of the Coriolis force is investigated by modeling the atmospheric surface/boundary layer with three different methodologies. The results show that the Coriolis force is negligible...

  16. Forces and friction between hydrophilic and hydrophobic surfaces: influence of oleate species.

    Science.gov (United States)

    Theander, Katarina; Pugh, Robert J; Rutland, Mark W

    2007-09-15

    The atomic force microscope has been used to investigate normal surface forces and lateral friction forces at different concentrations of sodium oleate, a frequently used fatty acid in the deinking process. The measurements have been performed using the colloidal probe technique with bead materials consisting of cellulose and silica. Cellulose was used together with a printing ink alkyd resin and mica, whereas silica was used with a hydrophobized silica wafer. The cellulose-alkyd resin system showed stronger double layer repulsion and the friction was reduced with increasing surfactant concentration. The adhesive interaction disappeared immediately on addition of sodium oleate. The normal surface forces for cellulose-mica indicated no apparent adsorption of the sodium oleate however, the friction coefficient increased on addition of sodium oleate, which we ascribe to some limited adsorption increasing the effective surface roughness. The silica-hydrophobic silica system showed a completely different surface force behavior at the different concentrations. An attractive hydrophobic interaction was evident since the surfaces jumped into adhesive contact at a longer distance than the van der Waals forces would predict. The strong adhesion was reflected in the friction forces as a nonlinear relationship between load and friction and a large friction response at zero applied load. Indirect evidence of adsorption to the hydrophilic silica surface was also observed in this case, and QCM studies were performed to confirm the adsorption of material to both surfaces.

  17. Tip-force induced surface deformation in the layered commensurate tellurides NbA xTe 2 (A = Si, Ge) during atomic force microscopy measurements

    Science.gov (United States)

    Bengel, H.; Cantow, H.-J.; Magonov, S. N.; Monconduit, L.; Evain, M.; Whangbo, M.-H.

    1994-12-01

    The Te-atom surfaces of commensurate layered tellurides NbA xTe 2 ( A = Si, x = {1}/{2}; A = Ge, x = {1}/{3}, {2}/{5}, {3}/{7}) were examined by atomic force microscopy (AFM) at different applied forces. Although the bulk crystal structures show a negligible height corrugation in the surface Te-atom sheets, the AFM images exhibit dark linear patterns that become strongly pronounced at high applied forces (several hundreds nN). This feature comes about because the tip-sample force interactions induce a surface corrugation according to the local hardness variation of the surface.

  18. Adhesion force between cyclopentane hydrate and mineral surfaces.

    Science.gov (United States)

    Aman, Zachary M; Leith, William J; Grasso, Giovanny A; Sloan, E Dendy; Sum, Amadeu K; Koh, Carolyn A

    2013-12-17

    Clathrate hydrate adhesion forces play a critical role in describing aggregation and deposition behavior in conventional energy production and transportation. This manuscript uses a unique micromechanical force apparatus to measure the adhesion force between cyclopentane hydrate and heterogeneous quartz and calcite substrates. The latter substrates represent models for coproduced sand and scale often present during conventional energy production and transportation. Micromechanical adhesion force data indicate that clathrate hydrate adhesive forces are 5-10× larger for calcite and quartz minerals than stainless steel. Adhesive forces further increased by 3-15× when increasing surface contact time from 10 to 30 s. In some cases, liquid water from within the hydrate shell contacted the mineral surface and rapidly converted to clathrate hydrate. Further measurements on mineral surfaces with physical control of surface roughness showed a nonlinear dependence of water wetting angle on surface roughness. Existing adhesive force theory correctly predicted the dependence of clathrate hydrate adhesive force on calcite wettability, but did not accurately capture the dependence on quartz wettability. This comparison suggests that the substrate surface may not be inert, and may contribute positively to the strength of the capillary bridge formed between hydrate particles and solid surfaces.

  19. The extended surface forces apparatus. IV. Precision static pressure control

    OpenAIRE

    Schurtenberger E; Heuberger M

    2011-01-01

    We report on design and performance of an extended surface forces apparatus (eSFA) built into a pressurized system. The aim of this instrument is to provide control over static pressure and temperature to facilitate direct surface force experiments in equilibrium with fluids at different loci of their phase diagram. We built an autoclave that can bear a miniature eSFA. To avoid mechanical or electrical feedtroughs the miniature apparatus uses an external surface coarse approach stage under am...

  20. Surface Force Strategy: Return to Sea Control

    Science.gov (United States)

    2016-01-01

    the freedom of the seas provided by the U.S. Navy. Threats ranging from low-end piracy to well-armed non-state militant groups, to the navies of...improvements to mission planning software , battle management software for Warfare Commanders, and tools to manage unit and force level emissions. The

  1. Asperity Interaction and Substrate Deformation in Statistical Summation Models of Contact Between Rough Surfaces

    NARCIS (Netherlands)

    Vakis, Antonis I.

    A method is proposed to account for asperity interaction and bulk substrate deformation in models that utilize statistical summation of asperity forces to characterize contact between rough surfaces. Interaction deformations of noncontacting asperities are calculated based on the probability that

  2. Asperity interaction in adhesive contact of metallic rough surfaces

    International Nuclear Information System (INIS)

    Sahoo, Prasanta; Banerjee, Atanu

    2005-01-01

    The analysis of adhesive contact of metallic rough surfaces considering the effect of asperity interaction is the subject of this investigation. The micro-contact model of asperity interactions developed by Zhao and Chang (2001 Trans. ASME: J. Tribol. 123 857-64) is combined with the elastic plastic adhesive contact model developed by Chang et al (1988 Trans. ASME: J. Tribol. 110 50-6) to consider the asperity interaction and elastic-plastic deformation in the presence of surface forces simultaneously. The well-established elastic adhesion index and plasticity index are used to consider the different contact conditions. Results show that asperity interaction influences the load-separation behaviour in elastic-plastic adhesive contact of metallic rough surfaces significantly and, in general, adhesion is reduced due to asperity interactions

  3. Frictional forces between hydrophilic and hydrophobic particle coated nanostructured surfaces

    DEFF Research Database (Denmark)

    Hansson, Petra M; Claesson, Per M.; Swerin, Agne

    2013-01-01

    Friction forces have long been associated with the famous Amontons' rule that states that the friction force is linearly dependent on the applied normal load, with the proportionality constant being known as the friction coefficient. Amontons' rule is however purely phenomenological and does...... not in itself provide any information on why the friction coefficient is different for different material combinations. In this study, friction forces between a colloidal probe and nanostructured particle coated surfaces in an aqueous environment exhibiting different roughness length scales were measured...... by utilizing the atomic force microscope (AFM). The chemistry of the surfaces and the probe was varied between hydrophilic silica and hydrophobized silica. For hydrophilic silica surfaces, the friction coefficient was significantly higher for the particle coated surfaces than on the flat reference surface. All...

  4. Finite element modeling of intermuscular interactions and myofascial force transmission

    NARCIS (Netherlands)

    Yucesoy, C.A.; Koopman, Hubertus F.J.M.; Huijing, P.A.J.B.M.; Grootenboer, H.J.

    2001-01-01

    A finite element muscle model to study the principles of intermuscular myofascial force transmission is developed. The results obtained explain force differences at the distal and proximal tendons of muscles that have mechanical interaction. This is in agreement with experimental findings in other

  5. Colloid-probe AFM studies of the interaction forces of proteins adsorbed on colloidal crystals.

    Science.gov (United States)

    Singh, Gurvinder; Bremmell, Kristen E; Griesser, Hans J; Kingshott, Peter

    2015-04-28

    In recent years, colloid-probe AFM has been used to measure the direct interaction forces between colloidal particles of different size or surface functionality in aqueous media, as one can study different forces in symmerical systems (i.e., sphere-sphere geometry). The present study investigates the interaction between protein coatings on colloid probes and hydrophilic surfaces decorated with hexagonally close packed single particle layers that are either uncoated or coated with proteins. Controlled solvent evaporation from aqueous suspensions of colloidal particles (coated with or without lysozyme and albumin) produces single layers of close-packed colloidal crystals over large areas on a solid support. The measurements have been carried out in an aqueous medium at different salt concentrations and pH values. The results show changes in the interaction forces as the surface charge of the unmodified or modified particles, and ionic strength or pH of the solution is altered. At high ionic strength or pH, electrostatic interactions are screened, and a strong repulsive force at short separation below 5 nm dominates, suggesting structural changes in the absorbed protein layer on the particles. We also study the force of adhesion, which decreases with an increment in the salt concentration, and the interaction between two different proteins indicating a repulsive interaction on approach and adhesion on retraction.

  6. Adhesion force of staphylococcus aureus on various biomaterial surfaces.

    Science.gov (United States)

    Alam, Fahad; Balani, Kantesh

    2017-01-01

    Staphylococcus comprises of more than half of all pathogens in orthopedic implant infections and they can cause major bone infection which can result in destruction of joint and bone. In the current study, adhesion force of bacteria on the surface of various biomaterial surfaces is measured using atomic force microscope (AFM). Staphylococcus aureus was immobilized on an AFM tipless cantilever as a force probe to measure the adhesion force between bacteria and biomaterials (viz. ultra-high molecular weight poly ethylene (UHMWPE), stainless steel (SS), Ti-6Al-4V alloy, hydroxyapatite (HA)). At the contact time of 10s, UHMWPE shows weak adhesion force (~4nN) whereas SS showed strong adhesion force (~15nN) due to their surface energy and surface roughness. Bacterial retention and viability experiment (3M™ petrifilm test, agar plate) dictates that hydroxyapatite shows the lowest vaibility of bacteria, whereas lowest bacterial retention is observed on UHMWPE surface. Similar results were obtained from live/dead staining test, where HA shows 65% viability, whereas on UHMWPE, SS and Ti-6Al-4V, the bacterial viability is 78%, 94% and 97%, respectively. Lower adhesion forces, constrained pull-off distance (of bacterial) and high antibacterial resistance of bioactive-HA makes it a potential biomaterial for bone-replacement arthroplasty. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Cell surface engineering to control cellular interactions

    OpenAIRE

    Custódio, Catarina A.; Mano, João F.

    2016-01-01

    Cell surface composition determines all interactions of the cell with its environment, thus cell functions such as adhesion, migration and cell–cell interactions can potentially be controlled by engineering and manipulating the cell membrane. Cell membranes present a rich repertoire of molecules, therefore a versatile ground for modification. However the complex and dynamic nature of the cell surface is also a major challenge for cell surface engineering that should also involve strategies co...

  8. Surface Water Interactions using Environmental Isotopes

    Indian Academy of Sciences (India)

    40

    lead to the deterioration of water quality of both surface and groundwater. One of the important features of karst terrains is the interaction between surface water and groundwater, which has been the subject of interest for many researchers because of the potential of contamination of the aquifer from surface water recharge.

  9. Interaction between heterogeneously charged surfaces: surface patches and charge modulation.

    Science.gov (United States)

    Ben-Yaakov, Dan; Andelman, David; Diamant, Haim

    2013-02-01

    When solid surfaces are immersed in aqueous solutions, some of their charges can dissociate and leave behind charged patches on the surface. Although the charges are distributed heterogeneously on the surface, most of the theoretical models treat them as homogeneous. For overall non-neutral surfaces, the assumption of surface charge homogeneity is rather reasonable since the leading terms of two such interacting surfaces depend on the nonzero average charge. However, for overall neutral surfaces the nature of the surface charge distribution is crucial in determining the intersurface interaction. In the present work we study the interaction between two charged surfaces across an aqueous solution for several charge distributions. The analysis is preformed within the framework of the linearized Poisson-Boltzmann theory. For periodic charge distributions the interaction is found to be repulsive at small separations, unless the two surface distributions are completely out-of-phase with respect to each other. For quenched random charge distributions we find that due to the presence of the ionic solution in between the surfaces, the intersurface repulsion dominates over the attraction in the linear regime of the Poisson-Boltzmann theory. The effect of quenched charge heterogeneity is found to be particularly substantial in the case of large charged domains.

  10. Surface forces between hydrophilic silica surfaces in a moisture-sensitive oleophilic diacrylate monomer liquid

    Science.gov (United States)

    Ito, Shunya; Kasuya, Motohiro; Kurihara, Kazue; Nakagawa, Masaru

    2018-02-01

    We measured the surface forces generated between fused silica surfaces in a low-viscosity oleophilic diacrylate monomer for reliably repeated ultraviolet (UV) nanoimprinting, and studied the influence of water in monomer liquids on the forces. Fused silica surfaces, with a static contact angle of 52.6 ± 1.7° for water, owing to the low degree of hydroxylation, hardly showed reproducible surface forces with repeated scan cycles, comprising approach and separation, even in an identical liquid monomer medium with both of low and high water content. The monomer liquid with a high water content of approximately 420 ppm showed a greater tendency to increase the surface forces at longer surface-surface distances compared with the monomer liquid with a low water content of approximately 60 ppm. On the other hand, silica surfaces with a water contact angle of < 5° after exposure to vacuum UV (VUV) light under a reduced air pressure showed reproducible profiles of surfaces forces using the monomer with a low water concentration of approximately 60 ppm for repeated surface forces scan cycles even in separately prepared silica surfaces, whilst they showed less reproducible profiles in the liquids with high water content of 430 ppm. These results suggested that water possibly adsorbed on the hydrophilic and hydrophobic silica surfaces in the monomer liquid of the high water concentration influenced the repeatability of the surface forces profiles.

  11. Circuit Design of Surface Acoustic Wave Based Micro Force Sensor

    Directory of Open Access Journals (Sweden)

    Yuanyuan Li

    2014-01-01

    Full Text Available Pressure sensors are commonly used in industrial production and mechanical system. However, resistance strain, piezoresistive sensor, and ceramic capacitive pressure sensors possess limitations, especially in micro force measurement. A surface acoustic wave (SAW based micro force sensor is designed in this paper, which is based on the theories of wavelet transform, SAW detection, and pierce oscillator circuits. Using lithium niobate as the basal material, a mathematical model is established to analyze the frequency, and a peripheral circuit is designed to measure the micro force. The SAW based micro force sensor is tested to show the reasonable design of detection circuit and the stability of frequency and amplitude.

  12. Interactions between kaolinite Al−OH surface and sodium hexametaphosphate

    Energy Technology Data Exchange (ETDEWEB)

    Han, Yonghua, E-mail: hyh19891102@163.com [School of Chemical and Environmental Engineering, China University of Mining and Technology, Beijing 100083 (China); Liu, Wenli; Zhou, Jia [School of Chemical and Environmental Engineering, China University of Mining and Technology, Beijing 100083 (China); Chen, Jianhua [College of Resources and Metallurgy, Guangxi University, Nanning 530004 (China)

    2016-11-30

    Highlights: • Sodium hexametaphosphate (NaHMP) can adsorb on kaolinite Al−OH terminated (001) surface easily. • The oxygen atoms of hexametaphosphate form strong hydrogen bonds with the hydrogen atoms of kaolinite Al−OH surface. • The electrostatic force is the main interaction between NaHMP and Al−OH surface. • The linear hexaphosphate −[PO{sub 3}]{sub m}− chains adsorb stably than −[HPO{sub 3}]{sub m}− chains. - Abstract: To investigate the dispersion mechanism of sodium hexametaphosphate on kaolinite particles, we simulated the interaction between linear polyphosphate chains and kaolinite Al−OH terminated surface by molecular dynamics, as well as the interaction between the [HPO{sub 4}]{sup 2−} anion and kaolinite Al−OH surface by density functional theory (DFT). The calculated results demonstrate that hexametaphosphate can be adsorbed by the kaolinite Al−OH surface. The oxygen atoms of hexametaphosphate anions may receive many electrons from the Al−OH surface and form hydrogen bonds with the hydrogen atoms of surface hydroxyl groups. Moreover, electrostatic force dominates the interactions between hexametaphosphate anions and kaolinite Al−OH surface. Therefore, after the adsorption of hexametaphosphate on kaolinite Al−OH surface, the kaolinite particles carry more negative charge and the electrostatic repulsion between particles increases. In addition, the adsorption of −[PO{sub 3}]{sub m}− species on the Al−OH surface should be more stable than the adsorption of −[HPO{sub 3}]{sub m}− species.

  13. Force control is related to low-frequency oscillations in force and surface EMG.

    Directory of Open Access Journals (Sweden)

    Hwasil Moon

    Full Text Available Force variability during constant force tasks is directly related to oscillations below 0.5 Hz in force. However, it is unknown whether such oscillations exist in muscle activity. The purpose of this paper, therefore, was to determine whether oscillations below 0.5 Hz in force are evident in the activation of muscle. Fourteen young adults (21.07 ± 2.76 years, 7 women performed constant isometric force tasks at 5% and 30% MVC by abducting the left index finger. We recorded the force output from the index finger and surface EMG from the first dorsal interosseous (FDI muscle and quantified the following outcomes: 1 variability of force using the SD of force; 2 power spectrum of force below 2 Hz; 3 EMG bursts; 4 power spectrum of EMG bursts below 2 Hz; and 5 power spectrum of the interference EMG from 10-300 Hz. The SD of force increased significantly from 5 to 30% MVC and this increase was significantly related to the increase in force oscillations below 0.5 Hz (R(2 = 0.82. For both force levels, the power spectrum for force and EMG burst was similar and contained most of the power from 0-0.5 Hz. Force and EMG burst oscillations below 0.5 Hz were highly coherent (coherence = 0.68. The increase in force oscillations below 0.5 Hz from 5 to 30% MVC was related to an increase in EMG burst oscillations below 0.5 Hz (R(2 = 0.51. Finally, there was a strong association between the increase in EMG burst oscillations below 0.5 Hz and the interference EMG from 35-60 Hz (R(2 = 0.95. In conclusion, this finding demonstrates that bursting of the EMG signal contains low-frequency oscillations below 0.5 Hz, which are associated with oscillations in force below 0.5 Hz.

  14. Attractive interaction between an atom and a surface

    International Nuclear Information System (INIS)

    Manson, J.R.; Ritchie, R.H.

    1983-01-01

    Using a general self-energy formalism we examine the interaction between an atom and a surface. Considered in detail are deviations from the Van der Waals force due to recoil and finite velocity of the particle. Calculations for positronium near a metal surface show that for such systems recoil and velocity effects are significant even at very low energies. We also examine the mechanisms for energy exchange with the surface and calculations show that single quantum events do not always dominate the exchange rates. 8 references, 2 figures

  15. Reduction of vortex induced forces and motion through surface roughness control

    Science.gov (United States)

    Bernitsas, Michael M; Raghavan, Kamaldev

    2014-04-01

    Roughness is added to the surface of a bluff body in a relative motion with respect to a fluid. The amount, size, and distribution of roughness on the body surface is controlled passively or actively to modify the flow around the body and subsequently the Vortex Induced Forces and Motion (VIFM). The added roughness, when designed and implemented appropriately, affects in a predetermined way the boundary layer, the separation of the boundary layer, the level of turbulence, the wake, the drag and lift forces, and consequently the Vortex Induced Motion (VIM), and the fluid-structure interaction. The goal of surface roughness control is to decrease/suppress Vortex Induced Forces and Motion. Suppression is required when fluid-structure interaction becomes destructive as in VIM of flexible cylinders or rigid cylinders on elastic support, such as underwater pipelines, marine risers, tubes in heat exchangers, nuclear fuel rods, cooling towers, SPAR offshore platforms.

  16. Monitoring ligand-receptor interactions by photonic force microscopy

    International Nuclear Information System (INIS)

    Jeney, Sylvia; Mor, Flavio; Forro, Laszlo; Koszali, Roland; Moy, Vincent T

    2010-01-01

    We introduce a method for the acquisition of single molecule force measurements of ligand-receptor interactions using the photonic force microscope (PFM). Biotin-functionalized beads, manipulated with an optical trap, and a streptavidin-functionalized coverslip were used to measure the effect of different pulling forces on the lifetime of individual streptavidin-biotin complexes. By optimizing the design of the optical trap and selection of the appropriate bead size, pulling forces in excess of 50 pN were achieved. Based on the amplitude of three-dimensional (3D) thermal position fluctuations of the attached bead, we were able to select for a bead-coverslip interaction that was mediated by a single streptavidin-biotin complex. Moreover, the developed experimental system was greatly accelerated by automation of data acquisition and analysis. In force-dependent kinetic measurements carried out between streptavidin and biotin, we observed that the streptavidin-biotin complex exhibited properties of a catch bond, with the lifetime increasing tenfold when the pulling force increased from 10 to 20 pN. We also show that silica beads were more appropriate than polystyrene beads for the force measurements, as tethers, longer than 200 nm, could be extracted from polystyrene beads.

  17. Knocking on surfaces : interactions of hyperthermal particles with metal surfaces

    NARCIS (Netherlands)

    Ueta, Hirokazu

    2010-01-01

    The study of gas-surface interaction dynamics is important both for the fundamental knowledge it provides and also to aid the development of applications involving processes such as sputtering, plasma etching and heterogeneous catalysis. Elementary steps in the interactions, such as chemical

  18. Surface microstructure of bitumen characterized by atomic force microscopy.

    Science.gov (United States)

    Yu, Xiaokong; Burnham, Nancy A; Tao, Mingjiang

    2015-04-01

    Bitumen, also called asphalt binder, plays important roles in many industrial applications. It is used as the primary binding agent in asphalt concrete, as a key component in damping systems such as rubber, and as an indispensable additive in paint and ink. Consisting of a large number of hydrocarbons of different sizes and polarities, together with heteroatoms and traces of metals, bitumen displays rich surface microstructures that affect its rheological properties. This paper reviews the current understanding of bitumen's surface microstructures characterized by Atomic Force Microscopy (AFM). Microstructures of bitumen develop to different forms depending on crude oil source, thermal history, and sample preparation method. While some bitumens display surface microstructures with fine domains, flake-like domains, and dendrite structuring, 'bee-structures' with wavy patterns several micrometers in diameter and tens of nanometers in height are commonly seen in other binders. Controversy exists regarding the chemical origin of the 'bee-structures', which has been related to the asphaltene fraction, the metal content, or the crystallizing waxes in bitumen. The rich chemistry of bitumen can result in complicated intermolecular associations such as coprecipitation of wax and metalloporphyrins in asphaltenes. Therefore, it is the molecular interactions among the different chemical components in bitumen, rather than a single chemical fraction, that are responsible for the evolution of bitumen's diverse microstructures, including the 'bee-structures'. Mechanisms such as curvature elasticity and surface wrinkling that explain the rippled structures observed in polymer crystals might be responsible for the formation of 'bee-structures' in bitumen. Despite the progress made on morphological characterization of bitumen using AFM, the fundamental question whether the microstructures observed on bitumen surfaces represent its bulk structure remains to be addressed. In addition

  19. Scalar self-interactions loosen constraints from fifth force searches

    International Nuclear Information System (INIS)

    Gubser, Steven S.; Khoury, Justin

    2004-01-01

    The mass of a scalar field mediating a fifth force is tightly constrained by experiments. We show, however, that adding a quartic self-interaction for such a scalar makes most tests much less constraining: the nonlinear equation of motion masks the coupling of the scalar to matter through the chameleon mechanism. We discuss consequences for fifth force experiments. In particular, we find that, with quartic coupling of order unity, a gravitational strength interaction with matter is allowed by current constraints. We show that our chameleon scalar field results in experimental signatures that could be detected through modest improvements of current laboratory set-ups

  20. Adhesive Force of a Spider Mite, Tetranychus urticae, to a Flat Smooth Surface

    Science.gov (United States)

    Mizutani, Katsumi; Egashira, Kai; Toukai, Tadashi; Ogushi, Jun

    The adhesion of a spider mite to a surface of a flat smooth plate is investigated as a model for micromachine parts to adhere to and move on such surfaces. The measurement of adhesive force is carried out under various conditions in which plate material, surface roughness of a plate and environmental humidity are differed. The adhesion mechanism is also discussed. Of the forces acting between a spider mite and a surface, one from dispersion interaction is the most dominant because (1) there is a high correlation between the adhesive force and the dispersion force component of surface energy with adhesive forces of 8.2µN for glass, 9.7µN for mica, 9.9µN for silicon and 12.1µN for gold, and because (2) high humidity and high surface roughness reduce the adhesive force. For strong adhesion based on work of adhesion, spider mites have tenent hairs with a bell-shaped end.

  1. Molecular Tension Probes for Imaging Forces at the Cell Surface.

    Science.gov (United States)

    Liu, Yang; Galior, Kornelia; Ma, Victor Pui-Yan; Salaita, Khalid

    2017-12-19

    Mechanical forces are essential for a variety of biological processes ranging from transcription and translation to cell adhesion, migration, and differentiation. Through the activation of mechanosensitive signaling pathways, cells sense and respond to physical stimuli from the surrounding environment, a process widely known as mechanotransduction. At the cell membrane, many signaling receptors, such as integrins, cadherins and T- or B-cell receptors, bind to their ligands on the surface of adjacent cells or the extracellular matrix (ECM) to mediate mechanotransduction. Upon ligation, these receptor-ligand bonds transmit piconewton (pN) mechanical forces that are generated, in part, by the cytoskeleton. Importantly, these forces expose cryptic sites within mechanosensitive proteins and modulate the binding kinetics (on/off rate) of receptor-ligand complexes to further fine-tune mechanotransduction and the corresponding cell behavior. Over the past three decades, two categories of methods have been developed to measure cell receptor forces. The first class is traction force microscopy (TFM) and micropost array detectors (mPADs). In these methods, cells are cultured on elastic polymers or microstructures that deform under mechanical forces. The second category of techniques is single molecule force spectroscopy (SMFS) including atomic force microscopy (AFM), optical or magnetic tweezers, and biomembrane force probe (BFP). In SMFS, the experimenter applies external forces to probe the mechanics of individual cells or single receptor-ligand complexes, serially, one bond at a time. Although these techniques are powerful, the limited throughput of SMFS and the nN force sensitivity of TFM have hindered further elucidation of the molecular mechanisms of mechanotransduction. In this Account, we introduce the recent advent of molecular tension fluorescence microscopy (MTFM) as an emerging tool for molecular imaging of receptor mechanics in living cells. MTFM probes are

  2. Organic chemistry on Titan: Surface interactions

    Science.gov (United States)

    Thompson, W. Reid; Sagan, Carl

    1992-01-01

    The interaction of Titan's organic sediments with the surface (solubility in nonpolar fluids) is discussed. How Titan's sediments can be exposed to an aqueous medium for short, but perhaps significant, periods of time is also discussed. Interactions with hydrocarbons and with volcanic magmas are considered. The alteration of Titan's organic sediments over geologic time by the impacts of meteorites and comets is discussed.

  3. Interaction of gases with solid surfaces

    Science.gov (United States)

    Borisov, Sergei F.; Balakhonov, Nikifor F.; Gubanov, Vladimir A.

    Various problems related to the interaction of gases with solid surfaces are examined theoretically and experimentally. In particular, attention is given to the scattering of molecules by surfaces in the nonequilibrium system gas-solid; heat transfer in gas-solid systems over a wide range of Knudsen numbers; adsorption processes at the gas-solid interface; and thermal accommodation of gases on a controlled surface. The discussion also covers kinetic equations for the nonequilibrium heterogeneous system gas-solid; scattering nucleus and accommodation coefficients on solid surfaces; and quantum-chemical calculations of the electron states of a solid surface.

  4. Simulation of Gas-Surface Dynamical Interactions

    Science.gov (United States)

    2007-07-01

    surface. The substrate with lattice constant a is represented in a simple ball and spring picture. on the particular problem. Time-independent...παvwell , (26) Simulation of Gas-Surface Dynamical Interactions 4 - 10 RTO-EN-AVT-142 g E ad v mvc ∆ v’well vc cM Figure 4

  5. Circuit Design of Surface Acoustic Wave Based Micro Force Sensor

    OpenAIRE

    Yuanyuan Li; Wenke Lu; Changchun Zhu; Qinghong Liu; Haoxin Zhang; Chenchao Tang

    2014-01-01

    Pressure sensors are commonly used in industrial production and mechanical system. However, resistance strain, piezoresistive sensor, and ceramic capacitive pressure sensors possess limitations, especially in micro force measurement. A surface acoustic wave (SAW) based micro force sensor is designed in this paper, which is based on the theories of wavelet transform, SAW detection, and pierce oscillator circuits. Using lithium niobate as the basal material, a mathematical model is established ...

  6. Surface potential modeling and reconstruction in Kelvin probe force microscopy.

    Science.gov (United States)

    Xu, Jie; Wu, Yangqing; Li, Wei; Xu, Jun

    2017-09-08

    Kelvin probe force microscopy (KPFM) measurement has been extensively applied in metallic, semiconductor and organic electronic or photovoltaic devices, to characterize the local contact potential difference or surface potential of the samples at the nanoscale. Here, a comprehensive modeling of surface potential in KPFM is established, from the well-known single capacitance model to a precise electrodynamic model, considering the long range property of the electrostatic force in KPFM. The limitations and relations of different models are also discussed. Besides, the feedback condition of the KPFM system is reconsidered and modified, showing that the influence of the cantilever has been overestimated by about 20% in previous reports. Afterwards, the surface potential of charged Si-nanocrystals is reconstructed based on the electrodynamic model, and the calculated surface charge density is very consistent with the macroscopic capacitance-voltage (C-V) measurement. A deep understanding and correct reconstruction of surface potential is crucial to the quantitative analysis of KPFM results.

  7. Forces on nuclei moving on autoionizing molecular potential energy surfaces.

    Science.gov (United States)

    Moiseyev, Nimrod

    2017-01-14

    Autoionization of molecular systems occurs in diatomic molecules and in small biochemical systems. Quantum chemistry packages enable calculation of complex potential energy surfaces (CPESs). The imaginary part of the CPES is associated with the autoionization decay rate, which is a function of the molecular structure. Molecular dynamics simulations, within the framework of the Born-Oppenheimer approximation, require the definition of a force field. The ability to calculate the forces on the nuclei in bio-systems when autoionization takes place seems to rely on an understanding of radiative damages in RNA and DNA arising from the release of slow moving electrons which have long de Broglie wavelengths. This work addresses calculation of the real forces on the nuclei moving on the CPES. By using the transformation of the time-dependent Schrödinger equation, previously used by Madelung, we proved that the classical forces on nuclei moving on the CPES correlated with the gradient of the real part of the CPES. It was proved that the force on the nuclei of the metastable molecules is time independent although the probability to detect metastable molecules exponentially decays. The classical force is obtained from the transformed Schrödinger equation when ℏ=0 and the Schrödinger equation is reduced to the classical (Newtonian) equations of motion. The forces on the nuclei regardless on what potential energy surface they move (parent CPES or product real PESs) vary in time due to the autoionization process.

  8. Higher order terms of the nonlinear forces in plasmas with collisions at laser interaction

    International Nuclear Information System (INIS)

    Kentwell, G.W.; Hora, H.

    1980-01-01

    The evaluation of the general expression of the nonlinear force of laser-plasma interaction showed discrepancies depending on the assumptions of the phase and collisions in the expressions used for E and H. While the first order terms of the derivations are remaining unchanged, new third order terms are found for the case of perpendicular incidence without collisions. With collisions, the additional non-pondermotive terms are derived to be more general than known before. It is then possible to evaluate the forces for oblique incidence with collisions and find an absorption caused force in the plane of the plasma surface. (author)

  9. Reynolds analogy for subcooled surface boiling under forced convection

    International Nuclear Information System (INIS)

    Avdeev, A.A.

    1982-01-01

    For the case of subcooled surface boiling under forced convection the analytic expression of analogy between the heat transfer and carry pulse (Reynolds analogy) is derived. It is concluded that the obtained dependence creates the basis for solution of a series of problems of surface boiling physics. On the basis of the performed analysis the method of coordinate calculation of the origin of intensive vapour generation is developed and the formula for calculation of the broken-off-bubble radius under forced convection is derived [ru

  10. Interface bonding in silicon oxide nanocontacts: interaction potentials and force measurements

    Science.gov (United States)

    Wierez-Kien, M.; Craciun, A. D.; Pinon, A. V.; Le Roux, S.; Gallani, J. L.; Rastei, M. V.

    2018-04-01

    The interface bonding between two silicon-oxide nanoscale surfaces has been studied as a function of atomic nature and size of contacting asperities. The binding forces obtained using various interaction potentials are compared with experimental force curves measured in vacuum with an atomic force microscope. In the limit of small nanocontacts (typically measured with sensitive probes the bonding is found to be influenced by thermal-induced fluctuations. Using interface interactions described by Morse, embedded atom model, or Lennard-Jones potential within reaction rate theory, we investigate three bonding types of covalent and van der Waals nature. The comparison of numerical and experimental results reveals that a Lennard-Jones-like potential originating from van der Waals interactions captures the binding characteristics of dry silicon oxide nanocontacts, and likely of other nanoscale materials adsorbed on silicon oxide surfaces. The analyses reveal the importance of the dispersive surface energy and of the effective contact area which is altered by stretching speeds. The mean unbinding force is found to decrease as the contact spends time in the attractive regime. This contact weakening is featured by a negative aging coefficient which broadens and shifts the thermal-induced force distribution at low stretching speeds.

  11. Interactions between Rotavirus and Suwannee River Organic Matter: Aggregation, Deposition, and Adhesion Force Measurement

    KAUST Repository

    Gutierrez, Leonardo

    2012-08-21

    Interactions between rotavirus and Suwannee River natural organic matter (NOM) were studied by time-resolved dynamic light scattering, quartz crystal microbalance, and atomic force microscopy. In NOM-containing NaCl solutions of up to 600 mM, rotavirus suspension remained stable for over 4 h. Atomic force microscopy (AFM) measurement for interaction force decay length at different ionic strengths showed that nonelectrostatic repulsive forces were mainly responsible for eliminating aggregation in NaCl solutions. Aggregation rates of rotavirus in solutions containing 20 mg C/L increased with divalent cation concentration until reaching a critical coagulation concentration of 30 mM CaCl2 or 70 mM MgCl2. Deposition kinetics of rotavirus on NOM-coated silica surface was studied using quartz crystal microbalance. Experimental attachment efficiencies for rotavirus adsorption to NOM-coated surface in MgCl2 solution were lower than in CaCl2 solution at a given divalent cation concentration. Stronger adhesion force was measured for virus-virus and virus-NOM interactions in CaCl2 solution compared to those in MgCl2 or NaCl solutions at the same ionic strength. This study suggested that divalent cation complexation with carboxylate groups in NOM and on virus surface was an important mechanism in the deposition and aggregation kinetics of rotavirus. © 2012 American Chemical Society.

  12. Modulation of the Casimir force by laser pulses: Influence of oxide films on the silicon surface

    Science.gov (United States)

    Klimchitskaya, G. L.; Bukina, M. N.; Churkin, Yu. V.; Yurova, V. A.

    2010-10-01

    The possibility of modulating the Casimir force that acts in an air medium between a gold sphere and a silicon plate irradiated by laser pulses has been studied. It has been demonstrated that the oxide film that is formed on the silicon surface in air hardly affects the possibility of modulating the Casimir force when the distances between interacting bodies are of the order of 100 nm. With an increase in the distance, the modulation depth decreases; however, this region is of less practical interest, because the Casimir forces become too weak.

  13. Nonlinear Dynamics of Cantilever-Sample Interactions in Atomic Force Microscopy

    Science.gov (United States)

    Cantrell, John H.; Cantrell, Sean A.

    2010-01-01

    The interaction of the cantilever tip of an atomic force microscope (AFM) with the sample surface is obtained by treating the cantilever and sample as independent systems coupled by a nonlinear force acting between the cantilever tip and a volume element of the sample surface. The volume element is subjected to a restoring force from the remainder of the sample that provides dynamical equilibrium for the combined systems. The model accounts for the positions on the cantilever of the cantilever tip, laser probe, and excitation force (if any) via a basis set of set of orthogonal functions that may be generalized to account for arbitrary cantilever shapes. The basis set is extended to include nonlinear cantilever modes. The model leads to a pair of coupled nonlinear differential equations that are solved analytically using a matrix iteration procedure. The effects of oscillatory excitation forces applied either to the cantilever or to the sample surface (or to both) are obtained from the solution set and applied to the to the assessment of phase and amplitude signals generated by various acoustic-atomic force microscope (A-AFM) modalities. The influence of bistable cantilever modes of on AFM signal generation is discussed. The effects on the cantilever-sample surface dynamics of subsurface features embedded in the sample that are perturbed by surface-generated oscillatory excitation forces and carried to the cantilever via wave propagation are accounted by the Bolef-Miller propagating wave model. Expressions pertaining to signal generation and image contrast in A-AFM are obtained and applied to amplitude modulation (intermittent contact) atomic force microscopy and resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM). The influence of phase accumulation in A-AFM on image contrast is discussed, as is the effect of hard contact and maximum nonlinearity regimes of A-AFM operation.

  14. Chemical Force Microscopy of Chemical and Biological Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Noy, A

    2006-01-02

    Interactions between chemical functionalities define outcomes of the vast majority of important events in chemistry, biology and materials science. Chemical Force Microscopy (CFM)--a technique that uses direct chemical functionalization of AFM probes with specific functionalities--allows researchers to investigate these important interactions directly. We review the basic principles of CFM, some examples of its application, and theoretical models that provide the basis for understanding the experimental results. We also emphasize application of modern kinetic theory of non-covalent interactions strength to the analysis of CFM data.

  15. Designing an experiment to measure cellular interaction forces

    Science.gov (United States)

    McAlinden, Niall; Glass, David G.; Millington, Owain R.; Wright, Amanda J.

    2013-09-01

    Optical trapping is a powerful tool in Life Science research and is becoming common place in many microscopy laboratories and facilities. The force applied by the laser beam on the trapped object can be accurately determined allowing any external forces acting on the trapped object to be deduced. We aim to design a series of experiments that use an optical trap to measure and quantify the interaction force between immune cells. In order to cause minimum perturbation to the sample we plan to directly trap T cells and remove the need to introduce exogenous beads to the sample. This poses a series of challenges and raises questions that need to be answered in order to design a set of effect end-point experiments. A typical cell is large compared to the beads normally trapped and highly non-uniform - can we reliably trap such objects and prevent them from rolling and re-orientating? In this paper we show how a spatial light modulator can produce a triple-spot trap, as opposed to a single-spot trap, giving complete control over the object's orientation and preventing it from rolling due, for example, to Brownian motion. To use an optical trap as a force transducer to measure an external force you must first have a reliably calibrated system. The optical trapping force is typically measured using either the theory of equipartition and observing the Brownian motion of the trapped object or using an escape force method, e.g. the viscous drag force method. In this paper we examine the relationship between force and displacement, as well as measuring the maximum displacement from equilibrium position before an object falls out of the trap, hence determining the conditions under which the different calibration methods should be applied.

  16. Self-energies and the interactions of particles with surfaces

    International Nuclear Information System (INIS)

    Manson, J.R.; Ritchie, R.H.; Echenique, P.M.; Gras-Marti, A.

    1987-01-01

    We have in this paper reviewed the method of treating many-body problems by means of an effective interaction self-energy. We have developed an alternatvie approach to the self-energy which is simpler and more straight-forward than standard methods, and we have illustrated its use with two examples of a charge interacting with a metal surface. In each case the self-energy produces the classical image potential together with corrections due to quantum mechanical effects. This method has also been successfully applied to the problem of an atom interacting with a surface. Corrections to the Van der Waals dispersion force are obtained, and via the non-conservative imaginary parts to /summation//sub i/(z) we discuss transition rates and energy exchange. 14 refs., 1 fig

  17. Accurate fluid force measurement based on control surface integration

    Science.gov (United States)

    Lentink, David

    2018-01-01

    Nonintrusive 3D fluid force measurements are still challenging to conduct accurately for freely moving animals, vehicles, and deforming objects. Two techniques, 3D particle image velocimetry (PIV) and a new technique, the aerodynamic force platform (AFP), address this. Both rely on the control volume integral for momentum; whereas PIV requires numerical integration of flow fields, the AFP performs the integration mechanically based on rigid walls that form the control surface. The accuracy of both PIV and AFP measurements based on the control surface integration is thought to hinge on determining the unsteady body force associated with the acceleration of the volume of displaced fluid. Here, I introduce a set of non-dimensional error ratios to show which fluid and body parameters make the error negligible. The unsteady body force is insignificant in all conditions where the average density of the body is much greater than the density of the fluid, e.g., in gas. Whenever a strongly deforming body experiences significant buoyancy and acceleration, the error is significant. Remarkably, this error can be entirely corrected for with an exact factor provided that the body has a sufficiently homogenous density or acceleration distribution, which is common in liquids. The correction factor for omitting the unsteady body force, {{{ {ρ f}} {1 - {ρ f} ( {{ρ b}+{ρ f}} )}.{( {{{{ρ }}b}+{ρ f}} )}}} , depends only on the fluid, {ρ f}, and body, {{ρ }}b, density. Whereas these straightforward solutions work even at the liquid-gas interface in a significant number of cases, they do not work for generalized bodies undergoing buoyancy in combination with appreciable body density inhomogeneity, volume change (PIV), or volume rate-of-change (PIV and AFP). In these less common cases, the 3D body shape needs to be measured and resolved in time and space to estimate the unsteady body force. The analysis shows that accounting for the unsteady body force is straightforward to non

  18. Hydrogeological controls of groundwater - land surface interactions

    Science.gov (United States)

    Bresciani, Etienne; Batelaan, Okke; Goderniaux, Pascal

    2017-04-01

    Interaction of groundwater with the land surface impacts a wide range of climatic, hydrologic, ecologic and geomorphologic processes. Many site-specific studies have successfully focused on measuring and modelling groundwater-surface water interaction, but upscaling or estimation at catchment or regional scale appears to be challenging. The factors controlling the interaction at regional scale are still poorly understood. In this contribution, a new 2-D (cross-sectional) analytical groundwater flow solution is used to derive a dimensionless criterion that expresses the conditions under which the groundwater outcrops at the land surface (Bresciani et al., 2016). The criterion gives insights into the functional relationships between geology, topography, climate and the locations of groundwater discharge along river systems. This sheds light on the debate about the topographic control of groundwater flow and groundwater-surface water interaction, as effectively the topography only influences the interaction when the groundwater table reaches the land surface. The criterion provides a practical tool to predict locations of groundwater discharge if a limited number of geomorphological and hydrogeological parameters (recharge, hydraulic conductivity and depth to impervious base) are known, and conversely it can provide regional estimates of the ratio of recharge over hydraulic conductivity if locations of groundwater discharge are known. A case study with known groundwater discharge locations located in South-West Brittany, France shows the feasibility of regional estimates of the ratio of recharge over hydraulic conductivity. Bresciani, E., Goderniaux, P. and Batelaan, O., 2016, Hydrogeological controls of water table-land surface interactions. Geophysical Research Letters 43(18): 9653-9661. http://dx.doi.org/10.1002/2016GL070618

  19. Density-functional calculation of van der Waals forces for free-electron-like surfaces

    DEFF Research Database (Denmark)

    Hult, E.; Hyldgaard, P.; Rossmeisl, Jan

    2001-01-01

    A recently proposed general density functional for asymptotic van der Waals forces is used to calculate van der Waals coefficients and reference-plane positions for realistic low-indexed Al surfaces. Results are given for a number of atoms and molecules outside the surfaces, as well as for the in......A recently proposed general density functional for asymptotic van der Waals forces is used to calculate van der Waals coefficients and reference-plane positions for realistic low-indexed Al surfaces. Results are given for a number of atoms and molecules outside the surfaces, as well...... as for the interaction between the surfaces themselves. The densities and static image-plane positions that are needed as input in the van der Waals functional are calculated self-consistently within density-functional theory using the generalized-gradient approximation, pseudopotentials, and plane waves. This study...

  20. Bonding and interaction of molecules with surfaces

    International Nuclear Information System (INIS)

    Ellis, D.E.

    1988-01-01

    In this lecture it is intended to discuss some general features of bonding and interaction of molecules with surfaces. The geometry of surface complexes is sufficiently difficult and the interaction mechanisms are sufficiently subtle. That all possible theoretical models need to be exploited such as: i) Semiempirical - including Huckel molecular orbital theory; ii)first principles including self-consistent-field Hartree-Fock and Local Density approaches; iii)explicitly correlated, including C.I., Generalized Valence Bond, Coupled Cluster Perturbation Theory and Many Body Perturbation Theory. (A.C.A.S.) [pt

  1. Interaction of nitrogen ions with beryllium surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Dobes, Katharina [Institute of Applied Physics, TU Wien, Association EURATOM ÖAW, Vienna (Austria); Köppen, Martin [Institute of Energy and Climate Research – Plasma Physics, Forschungszentrum Jülich GmbH, 52425 Jülich (Germany); Oberkofler, Martin [Max-Planck-Institut für Plasmaphysik, Boltzmannstraße 2, D-85748 Garching (Germany); Lungu, Cristian P.; Porosnicu, Corneliu [National Institute for Laser, Plasma, and Radiation Physics, Bucharest (Romania); Höschen, Till; Meisl, Gerd [Max-Planck-Institut für Plasmaphysik, Boltzmannstraße 2, D-85748 Garching (Germany); Linsmeier, Christian [Institute of Energy and Climate Research – Plasma Physics, Forschungszentrum Jülich GmbH, 52425 Jülich (Germany); Aumayr, Friedrich, E-mail: aumayr@iap.tuwien.ac.at [Institute of Applied Physics, TU Wien, Association EURATOM ÖAW, Vienna (Austria)

    2014-12-01

    The interaction of energetic nitrogen projectiles with a beryllium surface is studied using a highly sensitive quartz crystal microbalance technique. The overall mass change rate of the beryllium sample under N{sub 2}{sup +} ion impact at an ion energy of 5000 eV (i.e. 2500 eV per N) is investigated in situ and in real-time. A strong dependency of the observed mass change rate on the nitrogen fluence (at constant flux) is found and can be attributed to the formation of a nitrogen-containing mixed material layer within the ion penetration depth. The presented data elucidate the dynamics of the interaction process and the surface saturation with increasing nitrogen fluence in a unique way. Basically, distinct interaction regimes can be discriminated, which can be linked to the evolution of the surface composition upon nitrogen impact. Steady state surface conditions are obtained at a total cumulative nitrogen fluence of ∼80 × 10{sup 16} N atoms per cm{sup 2}. In dynamic equilibrium, the interaction is marked by continuous surface erosion. In this case, the observed total sputtering yield becomes independent from the applied nitrogen fluence and is of the order of 0.4 beryllium atoms per impinging nitrogen atom.

  2. Surface energy budget responses to radiative forcing at Summit, Greenland

    Science.gov (United States)

    Miller, Nathaniel B.; Shupe, Matthew D.; Cox, Christopher J.; Noone, David; Persson, P. Ola G.; Steffen, Konrad

    2017-02-01

    Greenland Ice Sheet surface temperatures are controlled by an exchange of energy at the surface, which includes radiative, turbulent, and ground heat fluxes. Data collected by multiple projects are leveraged to calculate all surface energy budget (SEB) terms at Summit, Greenland, for the full annual cycle from July 2013 to June 2014 and extend to longer periods for the radiative and turbulent SEB terms. Radiative fluxes are measured directly by a suite of broadband radiometers. Turbulent sensible heat flux is estimated via the bulk aerodynamic and eddy correlation methods, and the turbulent latent heat flux is calculated via a two-level approach using measurements at 10 and 2 m. The subsurface heat flux is calculated using a string of thermistors buried in the snow pack. Extensive quality-control data processing produced a data set in which all terms of the SEB are present 75 % of the full annual cycle, despite the harsh conditions. By including a storage term for a near-surface layer, the SEB is balanced in this data set to within the aggregated uncertainties for the individual terms. November and August case studies illustrate that surface radiative forcing is driven by synoptically forced cloud characteristics, especially by low-level, liquid-bearing clouds. The annual cycle and seasonal diurnal cycles of all SEB components indicate that the non-radiative terms are anticorrelated to changes in the total radiative flux and are hence responding to cloud radiative forcing. Generally, the non-radiative SEB terms and the upwelling longwave radiation component compensate for changes in downwelling radiation, although exact partitioning of energy in the response terms varies with season and near-surface characteristics such as stability and moisture availability. Substantial surface warming from low-level clouds typically leads to a change from a very stable to a weakly stable near-surface regime with no solar radiation or from a weakly stable to neutral

  3. The forces on a single interacting Bose-Einstein condensate

    Science.gov (United States)

    Thu, Nguyen Van

    2018-04-01

    Using double parabola approximation for a single Bose-Einstein condensate confined between double slabs we proved that in grand canonical ensemble (GCE) the ground state with Robin boundary condition (BC) is favored, whereas in canonical ensemble (CE) our system undergoes from ground state with Robin BC to the one with Dirichlet BC in small-L region and vice versa for large-L region and phase transition in space of the ground state is the first order. The surface tension force and Casimir force are also considered in both CE and GCE in detail.

  4. Enhancement of vortex induced forces and motion through surface roughness control

    Science.gov (United States)

    Bernitsas, Michael M [Saline, MI; Raghavan, Kamaldev [Houston, TX

    2011-11-01

    Roughness is added to the surface of a bluff body in a relative motion with respect to a fluid. The amount, size, and distribution of roughness on the body surface is controlled passively or actively to modify the flow around the body and subsequently the Vortex Induced Forces and Motion (VIFM). The added roughness, when designed and implemented appropriately, affects in a predetermined way the boundary layer, the separation of the boundary layer, the level of turbulence, the wake, the drag and lift forces, and consequently the Vortex Induced Motion (VIM), and the fluid-structure interaction. The goal of surface roughness control is to increase Vortex Induced Forces and Motion. Enhancement is needed in such applications as harnessing of clean and renewable energy from ocean/river currents using the ocean energy converter VIVACE (Vortex Induced Vibration for Aquatic Clean Energy).

  5. Understanding nanorheology and surface forces of confined thin films

    Science.gov (United States)

    Huang, Jun; Yan, Bin; Faghihnejad, Ali; Xu, Haolan; Zeng, Hongbo

    2014-02-01

    Understanding the nanorheology and associated intermolecular/surface forces of fluids in confined geometries or porous media is of both fundamental and practical importance, providing significant insights into various applications such as lubrication and micro/nanoelectromechanical systems. In this work, we briefly reviewed the fundamentals of nanoreheolgy, advances in experimental techniques and theoretical simulation methods, as well as important progress in the nanorheology of confined thin films. The advent of advanced experimental techniques such as surface forces apparatus (SFA), X-ray surface forces apparatus (XSFA) and atomic force microscope (AFM) and computational methods such as molecular dynamics simulations provides powerful tools to study a wide range of rheological phenomena at molecular level and nano scale. One of the most challenging issues unresolved is to elucidate the relationship between the rheological properties and structural evolution of the confined fluid films and particles suspensions. Some of the emerging research areas in the nanorheology field include, but are not limited to, the development of more advanced characterization techniques, design of multifunctional rheological fluids, bio-related nanorheology, and polymer brushes.

  6. Acid-base properties and the chemical imaging of surface-bound functional groups studied with scanning force microscopy

    NARCIS (Netherlands)

    van der Vegte, E.W.; Hadziioannou, G

    1997-01-01

    In this paper we present a scanning force microscopy (SFM) study on electrostatic and hydrogen-bonding interactions between chemically modified SFM probes and surface functional groups. pH-dependent adhesion force measurements in aqueous media between various ionizable functional groups showed a

  7. Plasma surface interactions in controlled fusion devices

    Energy Technology Data Exchange (ETDEWEB)

    Ghendrih, Ph.; Becoulet, M.; Costanzo, L. [and others

    2000-07-01

    This report brings together all the contributions of EURATOM/CEA association to the 14. international conference on plasma surface interactions in controlled fusion devices. 24 papers are presented and they deal mainly with the ergodic divertor and the first wall of Tore-supra tokamak.

  8. Plasma-Surface Interaction Activities in KSTAR

    NARCIS (Netherlands)

    Hong, S. H.; Yu, Y.; Kim, K. P.; Bak, J. G.; Park, H. J.; Oh, Y. S.; Chung, J.; Nam, Y. U.; Bang, E. N.; Kim, K. R.; Litnovsky, A.; Hellwig, M.; Matveev, D.; Komm, M.; van den Berg, M. A.; Kim, W. C.; Kim, H. K.; Rho, T. H.; Chu, Y.; Oh, Y. K.; Yang, H. L.; Park, K. R.; Chung, K. S.; Kstar Team,

    2013-01-01

    Selected topics of Plasma-Surface Interaction (PSI) activities in KSTAR are briefly introduced. SOL parameter measurements, particle balance and fuel retention, in-vessel dust research, and finally tungsten R & D are discussed. Some quantitative numbers from the initial phase of the operation

  9. Surface Water Interactions using Environmental Isotopes

    Indian Academy of Sciences (India)

    40

    Quantification of Groundwater - Surface Water Interactions using Environmental. Isotopes; A Case Study of Bringi Watershed, Kashmir Himalayas, India. Nadeem A. Bhat* and Gh. Jeelani. Department of Earth Sciences, University of Kashmir, Srinagar, J&K 190 006, India. *Correspondence to: Nadeem A. Bhat. E-mail: ...

  10. Interactions between whey proteins and kaolinite surfaces

    International Nuclear Information System (INIS)

    Barral, S.; Villa-Garcia, M.A.; Rendueles, M.; Diaz, M.

    2008-01-01

    The nature of the interactions between whey proteins and kaolinite surfaces was investigated by adsorption-desorption experiments at room temperature, performed at the isoelectric point (IEP) of the proteins and at pH 7. It was found that kaolinite is a strong adsorbent for proteins, reaching the maximum adsorption capacity at the IEP of each protein. At pH 7.0, the retention capacity decreased considerably. The adsorption isotherms showed typical Langmuir characteristics. X-ray diffraction data for the protein-kaolinite complexes showed that protein molecules were not intercalated in the mineral structure, but immobilized at the external surfaces and the edges of the kaolinite. Fourier transform IR results indicate the absence of hydrogen bonding between kaolinite surfaces and the polypeptide chain. The adsorption patterns appear to be related to electrostatic interactions, although steric effects should be also considered

  11. Characterizing the surface charge of clay minerals with Atomic Force Microscope (AFM

    Directory of Open Access Journals (Sweden)

    Yuan Guo

    2017-05-01

    Full Text Available The engineering properties of clayey soils, including fluid permeability, erosion resistance and cohesive strength, are quite different from those of non-cohesive soils. This is mainly due to their small platy particle shape and the surrounding diffuse double layer structure. By using the Atomic Force Microscopy (AFM, the surface topography and the interaction force between the silicon dioxide tip and the kaolinite/montmorillonite clay minerals have been measured in the 1.0 mM NaCl solution at neutral pH. From this, the surface potential of the clay minerals is determined by mathematical regression analyses using the DLVO model. The length/thickness ratio of kaolinite and montmorillonite particles measured ranges from 8.0 to 15.0. The surface potential and surface charge density vary with particles. The average surface potential of montmorillonite is −62.8 ± 10.6 mV, and the average surface potential of kaolinite is −40.9 ± 15.5 mV. The measured results help to understand the clay sediment interaction, and will be used to develop interparticle force model to simulate sediment transport during erosion process.

  12. Investigation of magnetorheological elastomer surface properties by atomic force microscopy

    International Nuclear Information System (INIS)

    Iacobescu, G.E.; Balasoiu, M.; Bica, I.

    2012-01-01

    Magnetorheological elastomers consist of a natural or synthetic rubber matrix interspersed with micron-sized ferromagnetic particles. The magnetoelastic properties of such a composite are not merely a sum of elasticity of the polymer and stiffness and magnetic properties of the filler, but also the result of a complex synergy of several effects, relevant at different length scales and detectable by different techniques. In the present work we investigate the microstructures, the surface magnetic properties and the elastic properties of new isotropic and anisotropic magnetorheological elastomer prepared using silicone rubber and soft magnetic carbonyl iron microspheres. The measurements were performed by atomic force microscopy in the following modes: standard imaging-non-contact atomic force microscopy, magnetic force microscopy and nanoindentation. A comparative study for the samples with different particle concentrations and strength of magnetic field applied during the polymerization process is developed

  13. Adhesion forces in liquid media: effect of surface topography and wettability.

    Science.gov (United States)

    Serro, A P; Colaço, R; Saramago, B

    2008-09-15

    This work was motivated by the unexpected values of adhesion forces measured between an atomic force microscopy tip and the hydrophobic surface of ultra-high-molecular-weight polyethylene. Two types of samples with different roughness but similar wettability were tested. Adhesion forces of similar magnitude were obtained in air and in polar liquids (water and Hank's Balanced Salt Solution, a saline solution) with the rougher sample. In contrast, the adhesion forces measured on the smoother sample in air were much higher than those measured in water or in the aqueous solution. Those experimental results suggested the presence of nanobubbles at the interface between the rough sample and the polar liquids. The existence of the nanobubbles was further confirmed by the images of the interface obtained in noncontact tapping mode. The adhesion forces measured in a nonpolar liquid (hexadecane) were small and of the same order of magnitude for both samples and their values were in good agreement with the predictions of the London-Hamaker approach for the van der Waals interactions. Finally, we correlate the appearance of nanobubbles with surface topography. The conclusion of this work is that adhesion forces measured in aqueous media may be strongly affected by the presence of nanobubbles if the surface presents topographical accidents.

  14. Surface Tension of Organic Liquids Using the OPLS/AA Force Field.

    Science.gov (United States)

    Zubillaga, Rafael A; Labastida, Ariana; Cruz, Bibiana; Martínez, Juan Carlos; Sánchez, Enrique; Alejandre, José

    2013-03-12

    Molecular dynamics simulations are performed to obtain the surface tension of 61 organic liquids using the OPLS/AA (all-atom optimized potential for liquid simulations). The force field parameters are the same as those recently used (Caleman et al. J. Chem. Theory Comput.2012, 8, 61) to determine several thermodynamic properties of 146 organic liquids. The correct evaluation of surface tension using slab simulations of liquids requires one to properly take into account the long-range interactions (Trukhymchuk and Alejandre J. Chem. Phys.1999, 111, 8510). In addition, the liquid density from slab simulations has to be the same as that obtained in liquid simulations at constant temperature and pressure. The new results of surface tensions from this work improve those reported by Caleman et al. The OPLS/AA force field gives good surface tensions compared with experimental data for most of the systems studied in this work, although it was developed to simulate liquids.

  15. Anomalous water dynamics at surfaces and interfaces: synergistic effects of confinement and surface interactions

    Science.gov (United States)

    Biswas, Rajib; Bagchi, Biman

    2018-01-01

    In nature, water is often found in contact with surfaces that are extended on the scale of molecule size but small on a macroscopic scale. Examples include lipid bilayers and reverse micelles as well as biomolecules like proteins, DNA and zeolites, to name a few. While the presence of surfaces and interfaces interrupts the continuous hydrogen bond network of liquid water, confinement on a mesoscopic scale introduces new features. Even when extended on a molecular scale, natural and biological surfaces often have features (like charge, hydrophobicity) that vary on the scale of the molecular diameter of water. As a result, many new and exotic features, which are not seen in the bulk, appear in the dynamics of water close to the surface. These different behaviors bear the signature of both water–surface interactions and of confinement. In other words, the altered properties are the result of the synergistic effects of surface–water interactions and confinement. Ultrafast spectroscopy, theoretical modeling and computer simulations together form powerful synergistic approaches towards an understanding of the properties of confined water in such systems as nanocavities, reverse micelles (RMs), water inside and outside biomolecules like proteins and DNA, and also between two hydrophobic walls. We shall review the experimental results and place them in the context of theory and simulations. For water confined within RMs, we discuss the possible interference effects propagating from opposite surfaces. Similar interference is found to give rise to an effective attractive force between two hydrophobic surfaces immersed and kept fixed at a separation of d, with the force showing an exponential dependence on this distance. For protein and DNA hydration, we shall examine a multitude of timescales that arise from frustration effects due to the inherent heterogeneity of these surfaces. We pay particular attention to the role of orientational correlations and modification of

  16. Interaction of oxygen with zirconia surface

    International Nuclear Information System (INIS)

    Ivankiv, L.I.; Ketsman, I.V.

    1999-01-01

    The influence of surface heat treatment, electron (50-800) eV irradiation and UV (180-300) nM illumination of adsorption system on the state of oxygen adsorbed on zirconia surface have been investigated. On the basis of experimental results obtained by investigation of photon emission accompanying oxygen adsorption (AL) and TPD data existence of adsorption sites on the surface is suggested on which irreversible dissociative adsorption of oxygen occurs. These very sites are associated with emission processes Conclusion is made that the only type of adsorption sites connected with anion vacancy is present on zirconia surface and this is its charge state that determines the state of adsorbed oxygen. One of the important mechanisms by which the electron and UV photon excitation affects the adsorption interaction is the change of the charge state of the adsorption site

  17. Interaction of alcohols with the calcite surface

    DEFF Research Database (Denmark)

    Bovet, Nicolas Emile; Yang, Mingjun; Javadi, Meshkat Sadat

    2015-01-01

    . Controlling their growth requires complex polysaccharides. Polysaccharide activity depends on the functionality of OH groups, so to simplify the system in order to get closer to a molecular level understanding, we investigated the interaction of OH from a suite of alcohols with clean, freshly cleaved calcite...... surfaces. X-ray photoelectron spectroscopy (XPS) provided binding energies and revealed the extent of surface coverage. Molecular dynamics (MD) simulations supplemented with information about molecule ordering, orientation and packing density. The results show that all alcohols studied bond...... with the calcite surface through the OH group, with their carbon chains sticking away in a standing-up orientation. Alcohol molecules are closely packed and form a well-ordered monolayer on the surface....

  18. Surface structure investigations using noncontact atomic force microscopy

    International Nuclear Information System (INIS)

    Kolodziej, J.J.; Such, B.; Goryl, M.; Krok, F.; Piatkowski, P.; Szymonski, M.

    2006-01-01

    Surfaces of several A III B V compound semiconductors (InSb, GaAs, InP, InAs) of the (0 0 1) orientation have been studied with noncontact atomic force microscopy (NC-AFM). Obtained atomically resolved patterns have been compared with structural models available in the literature. It is shown that NC-AFM is an efficient tool for imaging complex surface structures in real space. It is also demonstrated that the recent structural models of III-V compound surfaces provide a sound base for interpretation of majority of features present in recorded patterns. However, there are also many new findings revealed by the NC-AFM method that is still new experimental technique in the context of surface structure determination

  19. The extended surface forces apparatus. IV. Precision static pressure control.

    Science.gov (United States)

    Schurtenberger, E; Heuberger, M

    2011-10-01

    We report on design and performance of an extended surface forces apparatus (eSFA) built into a pressurized system. The aim of this instrument is to provide control over static pressure and temperature to facilitate direct surface force experiments in equilibrium with fluids at different loci of their phase diagram. We built an autoclave that can bear a miniature eSFA. To avoid mechanical or electrical feedtroughs the miniature apparatus uses an external surface coarse approach stage under ambient conditions. The surface separation is thus pre-adjusted to approximately ~3 μm before sliding the apparatus into the autoclave. Inside the autoclave, the surface separation can be further controlled with a magnetic drive at sub-Ångstrom precision over a 14 μm range. The autoclave pressure can then be set and maintained between 20 mbar and 170 bars with few mbar precision. The autoclave is connected to a specially designed pressurization system to precondition the fluids. The temperature can be controlled between -20 and 60 °C with few mK precision. We demonstrate the operation of the instrument in the case of gaseous or liquid carbon dioxide. Thanks to a consequent decoupling of the eSFA mechanical loop from the autoclave structure, the obtained measurement stability and reproducibility, at elevated pressures, is comparable to the one established for the conventional eSFA, operated under ambient conditions.

  20. The extended surface forces apparatus. IV. Precision static pressure control

    Science.gov (United States)

    Schurtenberger, E.; Heuberger, M.

    2011-10-01

    We report on design and performance of an extended surface forces apparatus (eSFA) built into a pressurized system. The aim of this instrument is to provide control over static pressure and temperature to facilitate direct surface force experiments in equilibrium with fluids at different loci of their phase diagram. We built an autoclave that can bear a miniature eSFA. To avoid mechanical or electrical feedtroughs the miniature apparatus uses an external surface coarse approach stage under ambient conditions. The surface separation is thus pre-adjusted to approximately ˜3 μm before sliding the apparatus into the autoclave. Inside the autoclave, the surface separation can be further controlled with a magnetic drive at sub-Ångstrom precision over a 14 μm range. The autoclave pressure can then be set and maintained between 20 mbar and 170 bars with few mbar precision. The autoclave is connected to a specially designed pressurization system to precondition the fluids. The temperature can be controlled between -20 and 60 °C with few mK precision. We demonstrate the operation of the instrument in the case of gaseous or liquid carbon dioxide. Thanks to a consequent decoupling of the eSFA mechanical loop from the autoclave structure, the obtained measurement stability and reproducibility, at elevated pressures, is comparable to the one established for the conventional eSFA, operated under ambient conditions.

  1. Modeling the mean interaction forces between powder particles. Application to silica gel-magnesium stearate mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, G., E-mail: gthomas@emse.fr [Ecole Nationale Superieure des Mines de Saint Etienne, Centre SPIN-LPMG, UMR CNRS 5148, 158 Cours Fauriel, 42023 Saint-Etienne Cedex 02 (France); Ouabbas, Y. [Ecole Nationale Superieure des Mines de Saint Etienne, Centre SPIN-LPMG, UMR CNRS 5148, 158 Cours Fauriel, 42023 Saint-Etienne Cedex 02 (France); Ecole Nationale Superieure des Techniques Industrielles et des Mines d' Albi-Carmaux, Centre RAPSODEE, UMR CNRS 2392, Campus Jarlard-81013 Albi (France); Grosseau, P. [Ecole Nationale Superieure des Mines de Saint Etienne, Centre SPIN-LPMG, UMR CNRS 5148, 158 Cours Fauriel, 42023 Saint-Etienne Cedex 02 (France); Baron, M.; Chamayou, A.; Galet, L. [Ecole Nationale Superieure des Techniques Industrielles et des Mines d' Albi-Carmaux, Centre RAPSODEE, UMR CNRS 2392, Campus Jarlard-81013 Albi (France)

    2009-06-15

    Dry coating experiments were performed by using the Hybridizer (Nara). Large host silica gel (SG) particles (d{sub 50} = 55 {mu}m) were coated with fine invited particles of magnesium stearate (MS, d{sub 50} = 4.6 {mu}m) for different contents of MS in the mixture. The real MS mass fraction w{sub I} obtained after mechanical treatment has been determined thanks to calibration from TGA measurements. The surface structure and morphology of MS coatings were observed using environmental scanning electron microscopy (ESEM) and atomic force microscopy (AFM) [Y. Ouabbas, A. Chamayou, L. Galet, M. Baron, J. Dodds, A.M. Danna, G. Thomas, B. Guilhot, P. Grosseau, Modification of powders properties by dry coating: some examples of process and products characteristics, Proceedings of CHISA2008, Prague, August 2008, submitted for publication; L. Galet, Y. Ouabbas, A.M. Danna, G. Thomas, P. Grosseau, M. Baron, A. Chamayou, Surface morphology analysis and AFM study of silica gel particles after mechanical dry coating with magnesium stearate, Proceedings of PSA2008, UK, September 2008, submitted for publication]. AFM has been also used to measure the adhesion forces between particles. Interaction forces between the material attached to the cantilever (magnesium stearate MS) and the surface of the composite material (silica gel SG or magnesium stearate MS) have been determined at different surface locations. For different compositions w{sub I} of the mixture MS-SG, the numeric distribution and the mean value f of the forces f{sub H} obtained for MS-SG interactions or f{sub I} for MS-MS interactions have been established and the experimental curve showing the evolution of f versus w{sub I} has been derived. Models of ordered structures have been developed, implying morphological hypotheses concerning large spherical or cylindrical host particles H and small invited spherical I. Different types of distribution of I materials onto the surface of H have been considered: for examples a

  2. Modeling the mean interaction forces between powder particles. Application to silica gel-magnesium stearate mixtures

    Science.gov (United States)

    Thomas, G.; Ouabbas, Y.; Grosseau, P.; Baron, M.; Chamayou, A.; Galet, L.

    2009-06-01

    Dry coating experiments were performed by using the Hybridizer (Nara). Large host silica gel (SG) particles ( d50 = 55 μm) were coated with fine invited particles of magnesium stearate (MS, d50 = 4.6 μm) for different contents of MS in the mixture. The real MS mass fraction w obtained after mechanical treatment has been determined thanks to calibration from TGA measurements. The surface structure and morphology of MS coatings were observed using environmental scanning electron microscopy (ESEM) and atomic force microscopy (AFM) [Y. Ouabbas, A. Chamayou, L. Galet, M. Baron, J. Dodds, A.M. Danna, G. Thomas, B. Guilhot, P. Grosseau, Modification of powders properties by dry coating: some examples of process and products characteristics, Proceedings of CHISA2008, Prague, August 2008, submitted for publication; L. Galet, Y. Ouabbas, A.M. Danna, G. Thomas, P. Grosseau, M. Baron, A. Chamayou, Surface morphology analysis and AFM study of silica gel particles after mechanical dry coating with magnesium stearate, Proceedings of PSA2008, UK, September 2008, submitted for publication]. AFM has been also used to measure the adhesion forces between particles. Interaction forces between the material attached to the cantilever (magnesium stearate MS) and the surface of the composite material (silica gel SG or magnesium stearate MS) have been determined at different surface locations. For different compositions w of the mixture MS-SG, the numeric distribution and the mean value f of the forces fH obtained for MS-SG interactions or fI for MS-MS interactions have been established and the experimental curve showing the evolution of f versus w has been derived. Models of ordered structures have been developed, implying morphological hypotheses concerning large spherical or cylindrical host particles H and small invited spherical I. Different types of distribution of I materials onto the surface of H have been considered: for examples a discrete monolayer - or multilayers - of

  3. Biological Surface Adsorption Index of Nanomaterials: Modelling Surface Interactions of Nanomaterials with Biomolecules.

    Science.gov (United States)

    Chen, Ran; Riviere, Jim E

    2017-01-01

    Quantitative analysis of the interactions between nanomaterials and their surrounding environment is crucial for safety evaluation in the application of nanotechnology as well as its development and standardization. In this chapter, we demonstrate the importance of the adsorption of surrounding molecules onto the surface of nanomaterials by forming biocorona and thus impact the bio-identity and fate of those materials. We illustrate the key factors including various physical forces in determining the interaction happening at bio-nano interfaces. We further discuss the mathematical endeavors in explaining and predicting the adsorption phenomena, and propose a new statistics-based surface adsorption model, the Biological Surface Adsorption Index (BSAI), to quantitatively analyze the interaction profile of surface adsorption of a large group of small organic molecules onto nanomaterials with varying surface physicochemical properties, first employing five descriptors representing the surface energy profile of the nanomaterials, then further incorporating traditional semi-empirical adsorption models to address concentration effects of solutes. These Advancements in surface adsorption modelling showed a promising development in the application of quantitative predictive models in biological applications, nanomedicine, and environmental safety assessment of nanomaterials.

  4. Modelling of energetic molecule-surface interactions

    International Nuclear Information System (INIS)

    Kerford, M.

    2000-09-01

    This thesis contains the results of molecular dynamics simulations of molecule-surface interactions, looking particularly at fullerene molecules and carbon surfaces. Energetic impacts of fullerene molecules on graphite create defect craters. The relationship between the parameters of the impacting molecule and the parameters of the crater axe examined and found to be a function of the energy and velocity of the impacting molecule. Less energetic fullerene molecules can be scattered from a graphite surface and the partitioning of energy after a scattering event is investigated. It is found that a large fraction of the kinetic energy retained after impact is translational energy, with a small fraction of rotational energy and a number of vibrational modes. At impact energies where the surface is not broken and at normal incidence, surface waves axe seen to occur. These waves axe used to develop a method of desorbing molecules from a graphite surface without damage to either the surface or the molecules being desorbed. A number of fullerene molecules are investigated and ways to increase the desorption yield are examined. It is found that this is a successful technique for desorbing large numbers of intact molecules from graphite. This technique could be used for desorbing intact molecules into a gas phase for mass spectrometric analysis. (author)

  5. Atomic force microscopy analysis of different surface treatments of Ti dental implant surfaces

    International Nuclear Information System (INIS)

    Bathomarco, R.V.; Solorzano, G.; Elias, C.N.; Prioli, R.

    2004-01-01

    The surface of commercial unalloyed titanium, used in dental implants, was analyzed by atomic force microscopy. The morphology, roughness, and surface area of the samples, submitted to mechanically-induced erosion, chemical etching and a combination of both, were compared. The results show that surface treatments strongly influence the dental implant physical and chemical properties. An analysis of the length dependence of the implant surface roughness shows that, for scan sizes larger than 50 μm, the average surface roughness is independent of the scanning length and that the surface treatments lead to average surface roughness in the range of 0.37 up to 0.48 μm. It is shown that the implant surface energy is sensitive to the titanium surface area. As the area increases there is a decrease in the surface contact angle

  6. Atomic force microscopy analysis of different surface treatments of Ti dental implant surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Bathomarco, R.V.; Solorzano, G.; Elias, C.N.; Prioli, R

    2004-06-30

    The surface of commercial unalloyed titanium, used in dental implants, was analyzed by atomic force microscopy. The morphology, roughness, and surface area of the samples, submitted to mechanically-induced erosion, chemical etching and a combination of both, were compared. The results show that surface treatments strongly influence the dental implant physical and chemical properties. An analysis of the length dependence of the implant surface roughness shows that, for scan sizes larger than 50 {mu}m, the average surface roughness is independent of the scanning length and that the surface treatments lead to average surface roughness in the range of 0.37 up to 0.48 {mu}m. It is shown that the implant surface energy is sensitive to the titanium surface area. As the area increases there is a decrease in the surface contact angle.

  7. Atmosphere-surface interactions over polar oceans and heterogeneous surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Vihma, T.

    1995-12-31

    Processes of interaction between the atmospheric boundary layer and the planetary surface have been studied with special emphasis on polar ocean surfaces: the open ocean, leads, polynyas and sea ice. The local exchange of momentum, heat and moisture has been studied experimentally both in the Weddell Sea and in the Greenland Sea. Exchange processes over heterogeneous surfaces are addressed by modelling studies. Over a homogeneous surface, the local turbulent fluxes can be reasonably well estimated using an iterative flux-profile scheme based on the Monin-Obukhov similarity theory. In the Greenland Sea, the near-surface air temperature and the generally small turbulent fluxes over the open ocean were affected by the sea surface temperature fronts. Over the sea ice cover in the Weddell Sea, the turbulent sensible heat flux was generally downwards, and together with an upward oceanic heat flux through the ice it compensated the heat loss from the surface via long-wave radiation. The wind dominated on time scales of days, while the current became important on longer time scales. The drift dynamics showed apparent spatial differences between the eastern and western regions, as well as between the Antarctic Circumpolar Current and the rest of the Weddell Sea. Inertial motion was present in regions of low ice concentration. The surface heterogeneity, arising e.g. from roughness or temperature distribution, poses a problem for the parameterization of surface exchange processes in large-scale models. In the case of neutral flow over a heterogeneous terrain, an effective roughness length can be used to parameterize the roughness effects

  8. Enhanced solar evaporation of water from porous media, through capillary mediated forces and surface treatment

    Energy Technology Data Exchange (ETDEWEB)

    Canbazoglu, F. M.; Fan, B.; Kargar, A.; Vemuri, K.; Bandaru, P. R., E-mail: pbandaru@ucsd.edu [Department of Mechanical Engineering, University of California, San Diego, La Jolla, CA (United States)

    2016-08-15

    The relative influence of the capillary, Marangoni, and hydrophobic forces in mediating the evaporation of water from carbon foam based porous media, in response to incident solar radiation, are investigated. It is indicated that inducing hydrophilic interactions on the surface, through nitric acid treatment of the foams, has a similar effect to reduced pore diameter and the ensuing capillary forces. The efficiency of water evaporation may be parameterized through the Capillary number (Ca), with a lower Ca being preferred. The proposed study is of much relevance to efficient solar energy utilization.

  9. Adhesion forces and mechanics in mannose-mediated acanthamoeba interactions.

    Directory of Open Access Journals (Sweden)

    Steven Huth

    Full Text Available The human pathogenic amoeba Acanthamoeba castellanii (A. castellanii causes severe diseases, including acanthamoeba keratitis and encephalitis. Pathogenicity arises from the killing of target-cells by an extracellular killing mechanism, where the crucial first step is the formation of a close contact between A. castellanii and the target-cell. This process is mediated by the glycocalix of the target-cell and mannose has been identified as key mediator. The aim of the present study was to carry out a detailed biophysical investigation of mannose-mediated adhesion of A. castellanii using force spectroscopy on single trophozoites. In detail, we studied the interaction of a mannose-coated cantilever with an A. castellanii trophozoite, as mannose is the decisive part of the cellular glycocalix in mediating pathogenicity. We observed a clear increase of the force to initiate cantilever detachment from the trophozoite with increasing contact time. This increase is also associated with an increase in the work of detachment. Furthermore, we also analyzed single rupture events during the detachment process and found that single rupture processes are associated with membrane tether formation, suggesting that the cytoskeleton is not involved in mannose binding events during the first few seconds of contact. Our study provides an experimental and conceptual basis for measuring interactions between pathogens and target-cells at different levels of complexity and as a function of interaction time, thus leading to new insights into the biophysical mechanisms of parasite pathogenicity.

  10. Adhesion forces and mechanics in mannose-mediated acanthamoeba interactions

    Science.gov (United States)

    Leippe, Matthias

    2017-01-01

    The human pathogenic amoeba Acanthamoeba castellanii (A. castellanii) causes severe diseases, including acanthamoeba keratitis and encephalitis. Pathogenicity arises from the killing of target-cells by an extracellular killing mechanism, where the crucial first step is the formation of a close contact between A. castellanii and the target-cell. This process is mediated by the glycocalix of the target-cell and mannose has been identified as key mediator. The aim of the present study was to carry out a detailed biophysical investigation of mannose-mediated adhesion of A. castellanii using force spectroscopy on single trophozoites. In detail, we studied the interaction of a mannose-coated cantilever with an A. castellanii trophozoite, as mannose is the decisive part of the cellular glycocalix in mediating pathogenicity. We observed a clear increase of the force to initiate cantilever detachment from the trophozoite with increasing contact time. This increase is also associated with an increase in the work of detachment. Furthermore, we also analyzed single rupture events during the detachment process and found that single rupture processes are associated with membrane tether formation, suggesting that the cytoskeleton is not involved in mannose binding events during the first few seconds of contact. Our study provides an experimental and conceptual basis for measuring interactions between pathogens and target-cells at different levels of complexity and as a function of interaction time, thus leading to new insights into the biophysical mechanisms of parasite pathogenicity. PMID:28472161

  11. Naval Reserve Force: Cost and Benefit Analysis of Reducing the Number of Naval Surface Reserve Force Operating Budget Holders

    National Research Council Canada - National Science Library

    Young, Eric

    1997-01-01

    .... This thesis examines one of Commander Naval Surface Reserve Force's initiatives for reducing the current number of Operating Budget holder's Comptroller Departments without sacrificing efficiency...

  12. Interaction of alcohols with the calcite surface.

    Science.gov (United States)

    Bovet, N; Yang, M; Javadi, M S; Stipp, S L S

    2015-02-07

    A clearer understanding of calcite interactions with organic molecules would contribute to a range of fields including harnessing the secrets of biomineralisation where organisms produce hard parts, increasing oil production from spent reservoirs, remediating contaminated soils and drinking water aquifers and improving manufacturing methods for industrial products such as pigments, soft abrasives, building materials and optical devices. Biomineralisation by some species of blue green algae produces beautifully elaborate platelets of calcite where the individual crystals are of nanometer scale. Controlling their growth requires complex polysaccharides. Polysaccharide activity depends on the functionality of OH groups, so to simplify the system in order to get closer to a molecular level understanding, we investigated the interaction of OH from a suite of alcohols with clean, freshly cleaved calcite surfaces. X-ray photoelectron spectroscopy (XPS) provided binding energies and revealed the extent of surface coverage. Molecular dynamics (MD) simulations supplemented with information about molecule ordering, orientation and packing density. The results show that all alcohols studied bond with the calcite surface through the OH group, with their carbon chains sticking away in a standing-up orientation. Alcohol molecules are closely packed and form a well-ordered monolayer on the surface.

  13. Interaction of the Helium, Hydrogen, Air, Argon, and Nitrogen Bubbles with Graphite Surface in Water.

    Science.gov (United States)

    Bartali, Ruben; Otyepka, Michal; Pykal, Martin; Lazar, Petr; Micheli, Victor; Gottardi, Gloria; Laidani, Nadhira

    2017-05-24

    The interaction of the confined gas with solid surface immersed in water is a common theme of many important fields such as self-cleaning surface, gas storage, and sensing. For that reason, we investigated the gas-graphite interaction in the water medium. The graphite surface was prepared by mechanical exfoliation of highly oriented pyrolytic graphite (HOPG). The surface chemistry and morphology were studied by X-ray photoelectron spectroscopy, profilometry, and atomic force microscopy. The surface energy of HOPG was estimated by contact angle measurements using the Owens-Wendt method. The interaction of gases (Ar, He, H 2 , N 2 , and air) with graphite was studied by a captive bubble method, in which the gas bubble was in contact with the exfoliated graphite surface in water media. The experimental data were corroborated by molecular dynamics simulations and density functional theory calculations. The surface energy of HOPG equaled to 52.8 mJ/m 2 and more of 95% of the surface energy was attributed to dispersion interactions. The results on gas-surface interaction indicated that HOPG surface had gasphilic behavior for helium and hydrogen, while gasphobic behavior for argon and nitrogen. The results showed that the variation of the gas contact angle was related to the balance between the gas-surface and gas-gas interaction potentials. For helium and hydrogen the gas-surface interaction was particularly high compared to gas-gas interaction and this promoted the favorable interaction with graphite surface.

  14. Electrical Double-Layer and Ion Bridging Forces between Symmetric and Asymmetric Charged Surfaces in the Presence of Mono- and Divalent Ions

    DEFF Research Database (Denmark)

    Liu, Xiaoyan; Feilberg, Karen Louise; Yan, Wei

    2017-01-01

    charged (3-aminopropyl)trimethoxysilane, and the negatively charged (3-mercaptopropyl)trimethoxysilane. The interactions between the three symmetric systems, as well as between the three asymmetric combinations of surfaces, were measured and compared to calculated electrical double-layer forces....... The results demonstrated that the long-range interactions between the surfaces in all cases were dominated by double-layer forces, while short-range interactions, including adhesion, were dominated by ion bridging forces in the cases where both interaction surfaces favored adsorption of calcium ions...

  15. Interacting Stochastic Processes: From Viciousness to Caging to Force Chains

    Science.gov (United States)

    Xu, Shiliyang

    the heterogeneous force network present in amorphous solids near the onset of rigidity, or jamming. The onset of rigidity can, in some sense, be viewed an interacting stochastic process with added constraints to enforce force-balance on each particle, for example. Our analysis yields string-like correlations in the locally-large forces in the system. Such correlations are reminiscent of force chains. While force chains have been readily observed in experiments, it is the first time these correlations have been observed in conjugate gradient simulations of repulsive soft spheres. We also study the contact geometry of the force network and explore a link with spin systems, namely spin glasses, to search for signatures of chaos due to marginal stability, for instance. Connections between jamming systems and spin glass systems will hopefully open up new avenues of theoretical investigation for both systems. Finally, we explore the quantum version of an individual stochastic process, namely the fractional Schrodinger equation. We prove that previously claimed exact solutions for certain potentials are incorrect and determine a new exact solution for a Levy index of unity and the harmonic oscillator potential. While our results contribute to the realm of mathematical physics, a physical realization of the fractional Schrodinger equation will indeed launch a new subfield of quantum mechanics.

  16. Motivating forces of human actions. Neuroimaging reward and social interaction.

    Science.gov (United States)

    Walter, Henrik; Abler, Birgit; Ciaramidaro, Angela; Erk, Susanne

    2005-11-15

    In neuroeconomics, reward and social interaction are central concepts to understand what motivates human behaviour. Both concepts are investigated in humans using neuroimaging methods. In this paper, we provide an overview about these results and discuss their relevance for economic behaviour. For reward it has been shown that a system exists in humans that is involved in predicting rewards and thus guides behaviour, involving a circuit including the striatum, the orbitofrontal cortex and the amygdala. Recent studies on social interaction revealed a mentalizing system representing the mental states of others. A central part of this system is the medial prefrontal cortex, in particular the anterior paracingulate cortex. The reward as well as the mentalizing system is engaged in economic decision-making. We will discuss implications of this study for neuromarketing as well as general implications of these results that may help to provide deeper insights into the motivating forces of human behaviour.

  17. Forces that Drive Nanoscale Self-assembly on Solid Surfaces

    International Nuclear Information System (INIS)

    Suo, Z.; Lu, W.

    2000-01-01

    Experimental evidence has accumulated in the recent decade that nanoscale patterns can self-assemble on solid surfaces. A two-component monolayer grown on a solid surface may separate into distinct phases. Sometimes the phases select sizes about 10 nm, and order into an array of stripes or disks. This paper reviews a model that accounts for these behaviors. Attention is focused on thermodynamic forces that drive the self-assembly. A double-welled, composition-dependent free energy drives phase separation. The phase boundary energy drives phase coarsening. The concentration-dependent surface stress drives phase refining. It is the competition between the coarsening and the refining that leads to size selection and spatial ordering. These thermodynamic forces are embodied in a nonlinear diffusion equation. Numerical simulations reveal rich dynamics of the pattern formation process. It is relatively fast for the phases to separate and select a uniform size, but exceedingly slow to order over a long distance, unless the symmetry is suitably broken

  18. Investigation of integrin expression on the surface of osteoblast-like cells by atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Caneva Soumetz, Federico [Department of Communication, Computer and System Sciences, University of Genova, Via Opera Pia, 13-16145 Genova (Italy); Saenz, Jose F. [Biophysical and Electronic Engineering Department, University of Genova, Via All' Opera Pia 11a, 16145 Genova (Italy); Pastorino, Laura; Ruggiero, Carmelina [Department of Communication, Computer and System Sciences, University of Genova, Via Opera Pia, 13-16145 Genova (Italy); Nosi, Daniele [Department of Anatomy, Histology and Forensic Medicine, Bio-photonic Laboratory, University of Florence, viale Morgagni, 85 Firenze, CAP 50134 Florence (Italy); Raiteri, Roberto, E-mail: rr@unige.it [Biophysical and Electronic Engineering Department, University of Genova, Via All' Opera Pia 11a, 16145 Genova (Italy)

    2010-03-15

    The transforming growth factor {beta}1 (TGF-{beta}1) is a human cytokine which has been demonstrated to modulate cell surface integrin repertoire. In this work integrin expression in response to TGF-{beta}1 stimulation has been investigated on the surface of human osteoblast-like cells. We used atomic force microscopy (AFM) and confocal laser scanning microscopy to assess integrin expression and to evaluate their distribution over the dorsal side of the plasma membrane. AFM probes have been covalently functionalised with monoclonal antibodies specific to the {beta}1 integrin subunit. Force curves have been collected in order to obtain maps of the interaction between the immobilized antibody and the respective cell membrane receptors. Adhesion peaks have been automatically detected by means of an ad hoc developed data analysis software. The specificity of the detected interactions has been assessed by adding free antibody in the solution and monitoring the dramatic decrease in the recorded interactions. In addition, the effect of TGF-{beta}1 treatment on both the fluorescence signal and the adhesion events has been tested. The level of expression of the {beta}1 integrin subunit was enhanced by TGF-{beta}1. As a further analysis, the adhesion force of the single living cells to the substrate was measured by laterally pushing the cell with the AFM tip and measuring the force necessary to displace it. The treatment with TGF-{beta}1 resulted in a decrease of the cell/substrate adhesion force. Results obtained by AFM have been validated by confocal laser scanning microscopy thus demonstrating the high potential of the AFM technique for the investigation of cell surface receptors distribution and trafficking at the nanoscale.

  19. Investigation of integrin expression on the surface of osteoblast-like cells by atomic force microscopy

    International Nuclear Information System (INIS)

    Caneva Soumetz, Federico; Saenz, Jose F.; Pastorino, Laura; Ruggiero, Carmelina; Nosi, Daniele; Raiteri, Roberto

    2010-01-01

    The transforming growth factor β1 (TGF-β1) is a human cytokine which has been demonstrated to modulate cell surface integrin repertoire. In this work integrin expression in response to TGF-β1 stimulation has been investigated on the surface of human osteoblast-like cells. We used atomic force microscopy (AFM) and confocal laser scanning microscopy to assess integrin expression and to evaluate their distribution over the dorsal side of the plasma membrane. AFM probes have been covalently functionalised with monoclonal antibodies specific to the β1 integrin subunit. Force curves have been collected in order to obtain maps of the interaction between the immobilized antibody and the respective cell membrane receptors. Adhesion peaks have been automatically detected by means of an ad hoc developed data analysis software. The specificity of the detected interactions has been assessed by adding free antibody in the solution and monitoring the dramatic decrease in the recorded interactions. In addition, the effect of TGF-β1 treatment on both the fluorescence signal and the adhesion events has been tested. The level of expression of the β1 integrin subunit was enhanced by TGF-β1. As a further analysis, the adhesion force of the single living cells to the substrate was measured by laterally pushing the cell with the AFM tip and measuring the force necessary to displace it. The treatment with TGF-β1 resulted in a decrease of the cell/substrate adhesion force. Results obtained by AFM have been validated by confocal laser scanning microscopy thus demonstrating the high potential of the AFM technique for the investigation of cell surface receptors distribution and trafficking at the nanoscale.

  20. Asperity interaction in elastic-plastic contact of rough surfaces in presence of adhesion

    International Nuclear Information System (INIS)

    Sahoo, Prasanta; Banerjee, Atanu

    2005-01-01

    This paper presents an analysis of the effect of asperity interaction in elastic-plastic contact of rough surfaces in the presence of adhesion. The micro-contact model of asperity interactions, developed by Zhao and Chang (2001 Trans. ASME: J. Tribol. 123 857-64), is integrated into the elastic-plastic contact model developed by Roy Chowdhury and Ghosh (1994 Wear 174 9-19) to allow the asperity interaction and elastic-plastic deformation in the presence of surface forces to be considered simultaneously. The well-established elastic and plastic adhesion indices are used to consider the different conditions that arise as a result of varying load and material parameters. Results show that asperity interaction influences the loading-unloading behaviour in elastic-plastic adhesive contact of rough surfaces and in general asperity interactions reduce the effect of surface forces

  1. Parallel force assay for protein-protein interactions.

    Directory of Open Access Journals (Sweden)

    Daniela Aschenbrenner

    Full Text Available Quantitative proteome research is greatly promoted by high-resolution parallel format assays. A characterization of protein complexes based on binding forces offers an unparalleled dynamic range and allows for the effective discrimination of non-specific interactions. Here we present a DNA-based Molecular Force Assay to quantify protein-protein interactions, namely the bond between different variants of GFP and GFP-binding nanobodies. We present different strategies to adjust the maximum sensitivity window of the assay by influencing the binding strength of the DNA reference duplexes. The binding of the nanobody Enhancer to the different GFP constructs is compared at high sensitivity of the assay. Whereas the binding strength to wild type and enhanced GFP are equal within experimental error, stronger binding to superfolder GFP is observed. This difference in binding strength is attributed to alterations in the amino acids that form contacts according to the crystal structure of the initial wild type GFP-Enhancer complex. Moreover, we outline the potential for large-scale parallelization of the assay.

  2. Concurrent Modeling of Hydrodynamics and Interaction Forces Improves Particle Deposition Predictions.

    Science.gov (United States)

    Jin, Chao; Ren, Carolyn L; Emelko, Monica B

    2016-04-19

    It is widely believed that media surface roughness enhances particle deposition-numerous, but inconsistent, examples of this effect have been reported. Here, a new mathematical framework describing the effects of hydrodynamics and interaction forces on particle deposition on rough spherical collectors in absence of an energy barrier was developed and validated. In addition to quantifying DLVO force, the model includes improved descriptions of flow field profiles and hydrodynamic retardation functions. This work demonstrates that hydrodynamic effects can significantly alter particle deposition relative to expectations when only the DLVO force is considered. Moreover, the combined effects of hydrodynamics and interaction forces on particle deposition on rough, spherical media are not additive, but synergistic. Notably, the developed model's particle deposition predictions are in closer agreement with experimental observations than those from current models, demonstrating the importance of inclusion of roughness impacts in particle deposition description/simulation. Consideration of hydrodynamic contributions to particle deposition may help to explain discrepancies between model-based expectations and experimental outcomes and improve descriptions of particle deposition during physicochemical filtration in systems with nonsmooth collector surfaces.

  3. Interactions of benzoic acid and phosphates with iron oxide colloids using chemical force titration.

    Science.gov (United States)

    Liang, Jana; Horton, J Hugh

    2005-11-08

    Colloidal iron oxides are an important component in soil systems and in water treatment processes. Humic-based organic compounds, containing both phenol and benzoate functional groups, are often present in these systems and compete strongly with phosphate species for binding sites on the iron oxide surfaces. Here, we examine the interaction of benzoate and phenolic groups with various iron oxide colloids using atomic force microscopy (AFM) chemical force titration measurements. Self-assembled monolayers (SAMs) of 4-(12-mercaptododecyloxy)benzoic acid and 4-(12-mercaptododecyloxy)phenol were used to prepare chemically modified Au-coated AFM tips, and these were used to probe the surface chemistry of a series of iron oxide colloids. The SAMs formed were also characterized using scanning tunneling microscopy, reflection-absorption infrared spectroscopy, and X-ray photoelectron spectroscopy. The surface pK(a) of 4-(12- mercaptododecyloxy)benzoic acid has been determined to be 4.0 +/- 0.5, and the interaction between the tip and the sample coated with a SAM of this species is dominated by hydrogen bonding. The chemical force titraton profile for an AFM probe coated with 4-(12- mercaptododecyloxy)benzoic acid and a bare iron oxide colloid demonstrates that the benzoic acid function group interacts with all three types of iron oxide sites present on the colloid surface over a wide pH range. Similar experiments were carried out on colloids precipitated in the presence of phosphoric, gallic, and tannic acids. The results are discussed in the context of the competitive binding interactions of solution species present in soils or in water treatment processes.

  4. Visualising the Micro World of Chemical/Geochemical Interactions Using Atomic Force Microscopy (AFM)

    Energy Technology Data Exchange (ETDEWEB)

    Graham, G.M.; Sorbie, K.S.

    1996-12-31

    Scanning force microscopy, in particular AFM (Atomic Force Microscopy), provides a particular useful and interesting tool for the examination of surface structure at the near-atomic level. AFM is particularly well suited to the study of interactions at the surface in aqueous solutions using real time in-situ measurements. In this paper there is presented AFM images showing in situ crystal growth from supersaturated BaSO{sub 4} solutions onto the surface of barite. Growth structures in the form of spiral crystal growth features, presumably originating from screw dislocations, are illustrated. AFM images of novel scale crystal growth inhibition experiments are presented. Examination of the manner in which generically different species adsorb onto growth structures may help to explain mechanistic differences in the way which different inhibitor species perform against barium sulphate scale formation. Adsorption of polyacrylamide species onto mica surfaces have been viewed. The general utility of AFM to a number of other common surface interactions in oil field chemistry will be discussed. 17 refs., 3 figs.

  5. Characterization of polymer surface structure and surface mechanical behaviour by sum frequency generation surface vibrational spectroscopy and atomic force microscopy

    International Nuclear Information System (INIS)

    Opdahl, Aric; Koffas, Telly S; Amitay-Sadovsky, Ella; Kim, Joonyeong; Somorjai, Gabor A

    2004-01-01

    Sum frequency generation (SFG) vibrational spectroscopy and atomic force microscopy (AFM) have been used to study polymer surface structure and surface mechanical behaviour, specifically to study the relationships between the surface properties of polymers and their bulk compositions and the environment to which the polymer is exposed. The combination of SFG surface vibrational spectroscopy and AFM has been used to study surface segregation behaviour of polyolefin blends at the polymer/air and polymer/solid interfaces. SFG surface vibrational spectroscopy and AFM experiments have also been performed to characterize the properties of polymer/liquid and polymer/polymer interfaces, focusing on hydrogel materials. A method was developed to study the surface properties of hydrogel contact lens materials at various hydration conditions. Finally, the effect of mechanical stretching on the surface composition and surface mechanical behaviour of phase-separated polyurethanes, used in biomedical implant devices, has been studied by both SFG surface vibrational spectroscopy and AFM. (topical review)

  6. Thermal desorption study of physical forces at the PTFE surface

    Science.gov (United States)

    Wheeler, D. R.; Pepper, S. V.

    1987-01-01

    Thermal desorption spectroscopy (TDS) of the polytetrafluoroethylene (PTFE) surface was successfully employed to study the possible role of physical forces in the enhancement of metal-PTFE adhesion by radiation. The thermal desorption spectra were analyzed without assumptions to yield the activation energy for desorption over a range of xenon coverage from less than 0.1 monolayer to more than 100 monolayers. For multilayer coverage, the desorption is zero-order with an activation energy equal to the sublimation energy of xenon. For submonolayer coverages, the order for desorption from the unirradiated PTFE surface is 0.73 and the activation energy for desorption is between 3.32 and 3.36 kcal/mol; less than the xenon sublimation energy. The effect of irradiation is to increase the activation energy for desorption to as high as 4 kcal/mol at low coverage.

  7. Shear force microscopy using piezoresistive cantilevers in surface metrology

    Science.gov (United States)

    Gotszalk, Teodor; Kopiec, Daniel; Sierakowski, Andrzej; Janus, Paweł; Grabiec, Piotr; Rangelow, Ivo W.

    2014-09-01

    In this article we describe application of piezoresistive cantilevers in surface investigations carried out with the use of shear force microscopy (ShFM). The novel piezoresistive cantilevers integrate a Wheatstone piezoresistive bridge was used to detect the cantilever deflection, thermal deflection detector and planar tip protruding out of the spring beam. Because the planar tip deflection can be detected and controlled electronically the described technology is very flexible and can be applied in many surface investigations. In this article we will present operation theory of the described solution, experimental setup, methods for calibration of the tip deflection detection and actuation The analysis will be illustrated with example results of topography measurements performed using the described technology.

  8. Plasma diagnostics surface analysis and interactions

    CERN Document Server

    Auciello, Orlando

    2013-01-01

    Plasmas and their interaction with materials have become subjects of major interest because of their importance in modern forefront technologies such as microelectronics, fusion energy, and space. Plasmas are used in microelectronics to process semiconductors (etching of patterns for microcircuits, plasma-induced deposition of thin films, etc.); plasmas produce deleterious erosion effects on surfaces of materials used for fusion devices and spaceships exposed to the low earth environment.Diagnostics of plasmas and materials exposed to them are fundamental to the understanding of the physical a

  9. Interaction of ethanol and water with the {1014} surface of calcite

    DEFF Research Database (Denmark)

    Cooke, David; Gray, R J; Sand, K K

    2010-01-01

    Molecular dynamics simulations have been used to model the interaction between ethanol, water, and the {1014} surface of calcite. Our results demonstrate that a single ethanol molecule is able to form two interactions with the mineral surface (both Ca-O and O-H), resulting in a highly ordered...... the starting configuration consists of a complete monolayer of water at the surface. The computational results are in good agreement with the results from atomic force microscopy experiments where it is observed that a layer of ethanol remains attached to the calcite surface, decreasing its ability to interact...

  10. Surface force measurements at the basal planes of ordered kaolinite particles.

    Science.gov (United States)

    Gupta, Vishal; Miller, Jan D

    2010-04-15

    An experimental procedure is presented to order kaolinite particles on substrates for interrogation of the two basal plane surfaces by atomic force microscopy. Surface force measurements were performed between a silicon nitride tip and each of the two faces (silica tetrahedral face and alumina octahedral face) of kaolinite in 1 mM KCl solution at pH 4, 5, 6, 8 and 10, using atomic force microscopy. The colloidal force measurements reveal that the silica tetrahedral face of kaolinite is negatively charged at pH>4, whereas the alumina octahedral face of kaolinite is positively charged at pH8. Such measurements have not been reported previously and the results suggest that the iso-electric point of the silica tetrahedral face is at pHkaolinite carry a permanent negative charge due to minor substitution of Al(3+) for Si(4+) in the silica tetrahedral layer, and suggest some surface charge dependency of the two faces with respect to solution pH. With this new information it may be possible to further explain the electrokinetic behavior of kaolinite particles, and their interactions in aqueous suspensions. 2010 Elsevier Inc. All rights reserved.

  11. XIX Conference on Plasma Surface Interactions

    International Nuclear Information System (INIS)

    Kurnaev, V A; Gasparyan, Yu M

    2016-01-01

    The 19 th Conference on Plasma Surface Interactions (PSI-2016) was held at National Research Nuclear University MEPhI (Moscow Engineering Physics Institute) on 28-29 January 2016. This is a traditional annual meeting organized by MEPhI for many years and devoted to the recent achievements of Russian scientists and foreign colleagues in experimental and computer simulations of plasma and its components' interactions with plasma faced materials (PFM) for fusion devices and plasma technologies. The conference agenda covered a broad list of topics including: • plasma induced erosion and modification of materials; • radiation damage in materials; • lithium and liquid metals as PFM; • modeling of plasma surface interaction and processes in SOL of tokamak plasma; • diagnostics of plasma-surface interaction. The aim of the conference was to present and discuss new results in PSI in a wide audience with different areas of expertise. The important feature of the conference is to give PhD and undergraduate students the opportunity for approbation of results of their scientific activity and improve their knowledge in the novel directions of R and D in the field of fusion and plasma technologies. In total, more than 80 experienced and young researchers participated in the conference. These Proceedings contain 21 papers selected for publication, which were reviewed by the invited international team of editors (T. Tanabe, S. Petrovich, Ch. Grisolia, Yu. Martynenko, S. Krasheninnikov, L. Begrambekov, A. Pisarev). The Conference as well as editing of this issue were supported by National Research Nuclear University MEPhI in the framework of the Russian Academic Excellence Project (contract No. 02.a03.21.0005, 27.08.2013). Finally, we would like to thank all of the speakers, participants and organizing committee members for their contribution to the conference. Acknowledgements The organizers of the conference would like to thank for the support from National Research

  12. Unlocking higher harmonics in atomic force microscopy with gentle interactions.

    Science.gov (United States)

    Santos, Sergio; Barcons, Victor; Font, Josep; Verdaguer, Albert

    2014-01-01

    In dynamic atomic force microscopy, nanoscale properties are encoded in the higher harmonics. Nevertheless, when gentle interactions and minimal invasiveness are required, these harmonics are typically undetectable. Here, we propose to externally drive an arbitrary number of exact higher harmonics above the noise level. In this way, multiple contrast channels that are sensitive to compositional variations are made accessible. Numerical integration of the equation of motion shows that the external introduction of exact harmonic frequencies does not compromise the fundamental frequency. Thermal fluctuations are also considered within the detection bandwidth of interest and discussed in terms of higher-harmonic phase contrast in the presence and absence of an external excitation of higher harmonics. Higher harmonic phase shifts further provide the means to directly decouple the true topography from that induced by compositional heterogeneity.

  13. Turbulent flow over an interactive alternating land-water surface

    Science.gov (United States)

    Van Heerwaarden, C.; Mellado, J. P.

    2014-12-01

    The alternating land-water surface is a challenging surface to represent accurately in weather and climate models, but it is of great importance for the surface energy balance in polar regions. The complexity of this surface lies in the fact that secondary circulations, which form at the boundary of water and land, interact strongly with the surface energy balance. Due to its large heat capacity, the water temperature adapts slowly to the flow, thus the properties of the atmosphere determine the uptake of energy from the water. In order to study this complex system in a simpler way, retaining only the most essential physics, we have simplified the full surface energy balance including radiation. We have derived a boundary condition that mimics the full balance and can be formulated as a so-called Robin boundary condition: a linear combination of Dirichlet (fixed temperature) and Neumann (fixed temperature gradient) ones. By spatially varying the coefficients, we are able to express land and water using this boundary condition. We have done a series of direct numerical simulations in which we generate artificial land-water patterns from noise created from a Gaussian spectrum centered around a dominant wave number. This method creates realistic random patterns, but we are still in control of the length scales. We show that the system can manifest itself in three regimes: micro-, meso- and macro-scale. In the micro-scale, we find perfect mixing of the near-surface atmosphere that results in identical air properties over water and land. In the meso-scale, secondary circulations alter the heat exchange considerably by advecting air between land and water. In addition, they bring the surface temperature of the land closer to that of the air, thereby modulating the energy loss due to outgoing longwave radiation. In the macro-scale regime, the flow over land and water become independent of each other and only the large scale forcings determine the energy balance.

  14. Determination of electrostatic potential distribution by atomic force microscopy (AFM) on model silica and alumina surfaces in aqueous electrolyte solutions

    International Nuclear Information System (INIS)

    Yelken, Gulnihal Ozek; Polat, Mehmet

    2014-01-01

    Graphical abstract: - Highlights: • Atomic force microscopy was employed to quantitatively determine the surface potential on silica and alumina surfaces immersed in aqueous electrolyte solutions at various pH values using the DLVO theory. • Potential distributions could be presented in the form of a potential map by repeating the procedure on multiple locations on these surfaces. • The average potential of the distributions agreed very well with the surface potentials measured by electrophoretic techniques. • Several experimental procedures required to achieve the very sensitive force measurements were outlined and demonstrated. - Abstract: AFM was employed as a physicochemical probe to determine the electrostatic potential distribution quantitatively on selected ideal oxide surfaces (quartz 0 0 0 1 and sapphire 0 0 0 1) in aqueous media. The force of interaction between a silicon nitride tip and the oxide surface was measured at a given point under well-defined solution conditions. Relevant theories were used to isolate the electrostatic component from the total force of interaction which was then employed to estimate the surface potential at that point. Repeating the procedure on selected locations generated a potential map of the surface. Comparison of these potentials with those obtained from independent electrokinetic measurements confirmed the validity of the approach

  15. Bubble size in surface boiling with forced convection

    International Nuclear Information System (INIS)

    Avdeev, A.A.

    1985-01-01

    Mechanisms of heat supply and removal were analyzed to obtain formula for calculating maximal bubble diameter for ''growth-condensation'' cycle in surface boiling with forced convection. Effect of some conditional parameters on the maximal bubble diameter was analyzed. Pressure (0.147-17.7 MPa), rate (0.2-9.15 m/s), subcooling (3-62 K), heat flux density (0.38-8.53 MW/m 2 ) configuration and geometrical sizes of the channel were considered. It was shown that change of heat flux density on channel wall affects slightly the diameter. Bubble size reduces at 0.1-2 MPa especially with pressure increase correlation of calculation results with experimental data shows a good agreement

  16. Optimized Model Surfaces for Advanced Atomic Force Microscopy Studies of Surface Nanobubbles.

    Science.gov (United States)

    Song, Bo; Zhou, Yi; Schönherr, Holger

    2016-11-01

    The formation of self-assembled monolayers (SAMs) of binary mixtures of 16-mercaptohexadecanoic acid (MHDA) and 1-octadecanethiol (ODT) on ultraflat template-stripped gold (TSG) surfaces was systematically investigated to clarify the assembly behavior, composition, and degree of possible phase segregation in light of atomic force microscopy (AFM) studies of surface nanobubbles on these substrates. The data for SAMs on TSG were compared to those obtained by adsorption on rough evaporated gold, as reported in a previous study. Quartz crystal microbalance and surface plasmon resonance data acquired in situ on TSG indicate that similar to SAM formation on conventional evaporated gold substrates ODT and MHDA form monolayers and bilayers, respectively. The second layer on MHDA, whose formation is attributed to hydrogen bonding, can be easily removed by adequate rinsing with water. The favorable agreement of the grazing incidence reflection Fourier transform infrared (GIR FTIR) spectroscopy and contact angle data analyzed with the Israelachvili-Gee model suggests that the binary SAMs do not segregate laterally. This conclusion is fully validated by high-resolution friction force AFM observations down to a length scale of 8-10 nm, which is much smaller than the typical observed surface nanobubble radii. Finally, correspondingly functionalized TSG substrates are shown to be valuable supports for studying surface nanobubbles by AFM in water and for addressing the relation between surface functionality and nanobubble formation and properties.

  17. Nonlinear effects of anthropogenic aerosol and urban land surface forcing on spring climate in eastern China

    Science.gov (United States)

    Deng, Jiechun; Xu, Haiming; Zhang, Leying

    2016-05-01

    Anthropogenic aerosols and urban land cover change induce opposite thermal effects on the atmosphere near surface as well as in the troposphere. One can think of these anthropogenic effects as composed of two parts: the individual effect due to an individual anthropogenic forcing and the nonlinear effects resulting from the coexistence of two forcing factors. In this study, we explored the role of such nonlinear effects in affecting East Asian climate, as well as individual forcing effects, using the Community Atmosphere Model version 5.1 coupled with the Community Land Model version 4. Atmospheric responses were simulated by including anthropogenic aerosol emission only, urban cover only, or the combination of the two, over eastern China. Results showed that nonlinear responses were different from any effects by an individual forcing or the linear combination of individual responses. The nonlinear interaction could generate cold horizontal temperature advection to cool the troposphere, which induced anomalous subsidence along the Yangtze River Valley (YRV). This anomalous vertical motion, together with a weakened low-level southwesterly, favored below-normal (above-normal) rainfall over the YRV (southern China), shifting the spring rain belt southward. The resultant diabatic cooling, in turn, amplified the anomalous descent and further decreased tropospheric temperature over the YRV, forming a positive feedback loop to maintain the nonlinear effects. Consequently, the nonlinear effects acted to reduce the climate anomalies from a simple linear combination of two individual effects and played an important role in regional responses to one anthropogenic forcing when the other is prescribed.

  18. A relationship between three-dimensional surface hydration structures and force distribution measured by atomic force microscopy

    Science.gov (United States)

    Miyazawa, Keisuke; Kobayashi, Naritaka; Watkins, Matthew; Shluger, Alexander L.; Amano, Ken-Ichi; Fukuma, Takeshi

    2016-03-01

    Hydration plays important roles in various solid-liquid interfacial phenomena. Very recently, three-dimensional scanning force microscopy (3D-SFM) has been proposed as a tool to visualise solvated surfaces and their hydration structures with lateral and vertical (sub) molecular resolution. However, the relationship between the 3D force map obtained and the equilibrium water density, ρ(r), distribution above the surface remains an open question. Here, we investigate this relationship at an interface of an inorganic mineral, fluorite, and water. The force maps measured in pure water are directly compared to force maps generated using the solvent tip approximation (STA) model and from explicit molecular dynamics simulations. The results show that the simulated STA force map describes the major features of the experimentally obtained force image. The agreement between the STA data and the experiment establishes the correspondence between the water density used as an input to the STA model and the experimental hydration structure and thus provides a tool to bridge the experimental force data and atomistic solvation structures. Further applications of this method should improve the accuracy and reliability of both interpretation of 3D-SFM force maps and atomistic simulations in a wide range of solid-liquid interfacial phenomena.Hydration plays important roles in various solid-liquid interfacial phenomena. Very recently, three-dimensional scanning force microscopy (3D-SFM) has been proposed as a tool to visualise solvated surfaces and their hydration structures with lateral and vertical (sub) molecular resolution. However, the relationship between the 3D force map obtained and the equilibrium water density, ρ(r), distribution above the surface remains an open question. Here, we investigate this relationship at an interface of an inorganic mineral, fluorite, and water. The force maps measured in pure water are directly compared to force maps generated using the solvent

  19. Construction of force-free fields which have toroidal surfaces about a given surface

    International Nuclear Information System (INIS)

    Bouligand, G.

    1983-05-01

    A study of two-fields (B vector, rotB vector) of conservative flux which admits a family of toroidal surfaces of parameter phi on a domain limited by a given surface S, suggests their construction by a Cauchy-Arzela method of step by step. Taking into account the Newcomb condition this method is consistent with force-free magnetic fields and with helical equilibria with scalar pressure. The method supposes that B vector is of class C 1 . This construction makes use of the remarkable property of the field B vector to be the surface gradient of a generating multivalued function Q on a closed surface. Consequently, the initial surface will be given with its normal metric coefficient K; that is to say, B vector admits a family F of homotopic surfaces on a infinitesimal domain about S, an element of F. From this, the periodic part of Q is a solution of a Beltrami equation for the flux conservation of which numerical resolution is envisaged. The study of these fields is made in a biorthogonal system of coordinates. The coeffficients of the two fundamental metric forms of magnetic surfaces vary with phi and are interrelated by a sixth order differential system of equations which gives their variation [fr

  20. Quantitative modeling assesses the contribution of bond strengthening, rebinding and force sharing to the avidity of biomolecule interactions.

    Directory of Open Access Journals (Sweden)

    Valentina Lo Schiavo

    Full Text Available Cell adhesion is mediated by numerous membrane receptors. It is desirable to derive the outcome of a cell-surface encounter from the molecular properties of interacting receptors and ligands. However, conventional parameters such as affinity or kinetic constants are often insufficient to account for receptor efficiency. Avidity is a qualitative concept frequently used to describe biomolecule interactions: this includes incompletely defined properties such as the capacity to form multivalent attachments. The aim of this study is to produce a working description of monovalent attachments formed by a model system, then to measure and interpret the behavior of divalent attachments under force. We investigated attachments between antibody-coated microspheres and surfaces coated with sparse monomeric or dimeric ligands. When bonds were subjected to a pulling force, they exhibited both a force-dependent dissociation consistent with Bell's empirical formula and a force- and time-dependent strengthening well described by a single parameter. Divalent attachments were stronger and less dependent on forces than monovalent ones. The proportion of divalent attachments resisting a force of 30 piconewtons for at least 5 s was 3.7 fold higher than that of monovalent attachments. Quantitative modeling showed that this required rebinding, i.e. additional bond formation between surfaces linked by divalent receptors forming only one bond. Further, experimental data were compatible with but did not require stress sharing between bonds within divalent attachments. Thus many ligand-receptor interactions do not behave as single-step reactions in the millisecond to second timescale. Rather, they exhibit progressive stabilization. This explains the high efficiency of multimerized or clustered receptors even when bonds are only subjected to moderate forces. Our approach provides a quantitative way of relating binding avidity to measurable parameters including bond

  1. Plasma-surface interactions under high heat and particle fluxes

    NARCIS (Netherlands)

    De Temmerman, G.; Bystrov, K.; Liu, F.; Liu, W.; Morgan, T.; Tanyeli, I.; van den Berg, M.; Xu, H.; Zielinski, J.

    2013-01-01

    The plasma-surface interactions expected in the divertor of a future fusion reactor are characterized by extreme heat and particle fluxes interacting with the plasma-facing surfaces. Powerful linear plasma generators are used to reproduce the expected plasma conditions and allow plasma-surface

  2. Intercomparison of oceanic and atmospheric forced and coupled mesoscale simulations Part I: Surface fluxes

    Directory of Open Access Journals (Sweden)

    P. Josse

    1999-04-01

    Full Text Available A mesoscale non-hydrostatic atmospheric model has been coupled with a mesoscale oceanic model. The case study is a four-day simulation of a strong storm event observed during the SEMAPHORE experiment over a 500 × 500 km2 domain. This domain encompasses a thermohaline front associated with the Azores current. In order to analyze the effect of mesoscale coupling, three simulations are compared: the first one with the atmospheric model forced by realistic sea surface temperature analyses; the second one with the ocean model forced by atmospheric fields, derived from weather forecast re-analyses; the third one with the models being coupled. For these three simulations the surface fluxes were computed with the same bulk parametrization. All three simulations succeed well in representing the main oceanic or atmospheric features observed during the storm. Comparison of surface fields with in situ observations reveals that the winds of the fine mesh atmospheric model are more realistic than those of the weather forecast re-analyses. The low-level winds simulated with the atmospheric model in the forced and coupled simulations are appreciably stronger than the re-analyzed winds. They also generate stronger fluxes. The coupled simulation has the strongest surface heat fluxes: the difference in the net heat budget with the oceanic forced simulation reaches on average 50 Wm-2 over the simulation period. Sea surface-temperature cooling is too weak in both simulations, but is improved in the coupled run and matches better the cooling observed with drifters. The spatial distributions of sea surface-temperature cooling and surface fluxes are strongly inhomogeneous over the simulation domain. The amplitude of the flux variation is maximum in the coupled run. Moreover the weak correlation between the cooling and heat flux patterns indicates that the surface fluxes are not responsible for the whole cooling and suggests that the response of the ocean mixed layer

  3. Intercomparison of oceanic and atmospheric forced and coupled mesoscale simulations Part I: Surface fluxes

    Directory of Open Access Journals (Sweden)

    H. Giordani

    Full Text Available A mesoscale non-hydrostatic atmospheric model has been coupled with a mesoscale oceanic model. The case study is a four-day simulation of a strong storm event observed during the SEMAPHORE experiment over a 500 × 500 km2 domain. This domain encompasses a thermohaline front associated with the Azores current. In order to analyze the effect of mesoscale coupling, three simulations are compared: the first one with the atmospheric model forced by realistic sea surface temperature analyses; the second one with the ocean model forced by atmospheric fields, derived from weather forecast re-analyses; the third one with the models being coupled. For these three simulations the surface fluxes were computed with the same bulk parametrization. All three simulations succeed well in representing the main oceanic or atmospheric features observed during the storm. Comparison of surface fields with in situ observations reveals that the winds of the fine mesh atmospheric model are more realistic than those of the weather forecast re-analyses. The low-level winds simulated with the atmospheric model in the forced and coupled simulations are appreciably stronger than the re-analyzed winds. They also generate stronger fluxes. The coupled simulation has the strongest surface heat fluxes: the difference in the net heat budget with the oceanic forced simulation reaches on average 50 Wm-2 over the simulation period. Sea surface-temperature cooling is too weak in both simulations, but is improved in the coupled run and matches better the cooling observed with drifters. The spatial distributions of sea surface-temperature cooling and surface fluxes are strongly inhomogeneous over the simulation domain. The amplitude of the flux variation is maximum in the coupled run. Moreover the weak correlation between the cooling and heat flux patterns indicates that the surface fluxes are not responsible for the whole cooling and suggests that the response of the ocean mixed layer

  4. ForceFit: a code to fit classical force fields to ab-initio potential energy surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Henson, Neil Jon [Los Alamos National Laboratory; Waldher, Benjamin [WSU; Kuta, Jadwiga [WSU; Clark, Aurora [WSU; Clark, Aurora E [NON LANL

    2009-01-01

    The ForceFit program package has been developed for fitting classical force field parameters based upon a force matching algorithm to quantum mechanical gradients of configurations that span the potential energy surface of the system. The program, which runs under Unix and is written in C++, is an easy to use, nonproprietary platform that enables gradient fitting of a wide variety of functional force field forms to quantum mechanical information obtained from an array of common electronic structure codes. All aspects of the fitting process are run from a graphical user interface, from the parsing of quantum mechanical data, assembling of a potential energy surface database, setting the force field and variables to be optimized, choosing a molecular mechanics code for comparison to the reference data, and finally, the initiation of a least squares minimization algorithm. Furthermore, the code is based on a modular templated code design that enables the facile addition of new functionality to the program.

  5. Combining confocal and atomic force microscopy to quantify single-virus binding to mammalian cell surfaces.

    Science.gov (United States)

    Newton, Richard; Delguste, Martin; Koehler, Melanie; Dumitru, Andra C; Laskowski, Pawel R; Müller, Daniel J; Alsteens, David

    2017-11-01

    Over the past five years, atomic force microscopy (AFM)-based approaches have evolved into a powerful multiparametric tool set capable of imaging the surfaces of biological samples ranging from single receptors to membranes and tissues. One of these approaches, force-distance curve-based AFM (FD-based AFM), uses a probing tip functionalized with a ligand to image living cells at high-resolution and simultaneously localize and characterize specific ligand-receptor binding events. Analyzing data from FD-based AFM experiments using appropriate probabilistic models allows quantification of the kinetic and thermodynamic parameters that describe the free-energy landscape of the ligand-receptor bond. We have recently developed an FD-based AFM approach to quantify the binding events of single enveloped viruses to surface receptors of living animal cells while simultaneously observing them by fluorescence microscopy. This approach has provided insights into the early stages of the interaction between a virus and a cell. Applied to a model virus, we probed the specific interaction with cells expressing viral cognate receptors and measured the affinity of the interaction. Furthermore, we observed that the virus rapidly established specific multivalent interactions and found that each bond formed in sequence strengthened the attachment of the virus to the cell. Here we describe detailed procedures for probing the specific interactions of viruses with living cells; these procedures cover tip preparation, cell sample preparation, step-by-step FD-based AFM imaging and data analysis. Experienced microscopists should be able to master the entire set of protocols in 1 month.

  6. Surface radiation budget and cloud radiative forcing from pan-Arctic Baseline Surface Radiation Network (BSRN) stations

    Science.gov (United States)

    Cox, C. J.; Long, C. N.; Crepinsek, S.; Maturilli, M.; McComiskey, A. C.; Miller, N.; Konopleva-Akish, E.; Kustov, V. Y.; Shupe, M.; Steffen, K.; Stanitski, D.; Starkweather, S.; Stone, R. S.; Uttal, T.; Walden, V. P.

    2015-12-01

    Monitoring and forecasting of the seasonal melt of snow and ice in the Arctic is a priority need as Arctic climate changes and the number of stakeholders increases. Seasonal snow and ice melt represent the largest annual perturbation to the surface net radiation budget. Radiative interactions between clouds, the surface and the atmosphere play an important role on scales of minutes to decades, but models insufficiently represent cloud properties. Furthermore, the surface radiation budget is not directly observed from satellite platforms. Direct observations from the surface must therefore be used to document the physical and correlative relationships between variables, and to provide a baseline target for data sets with more comprehensive spatial representation. High-quality, continuous, long-term observations of radiative fluxes are collected from land stations surrounding the Arctic Basin as part of the Baseline Surface Radiation Network (BSRN). The International Arctic Systems for Observing the Atmosphere (IASOA) facilitates international collaboration amongst station scientists and other topic experts for the purposes of streamlining pan-Arctic synthesis studies. The IASOA Radiation Working Group is currently analyzing the data acquired from Barrow, Alaska (1993-2015), Alert, Canada (2004-2014), Ny-Ålesund, Svalbard (1993-2015), Eureka, Canada (2007-2015), and Tiksi, Russia (2011-2015). The measurements include upwelling and downwelling longwave and shortwave fluxes, as well as direct and diffuse shortwave flux components, and surface meteorology. The observations are post-processed using the Radiative Flux Analysis (RFA) method, which, in addition to basic quality control, provides value-added metrics such as cloud radiative forcing (CRF), optical depth, and fractional sky cover. Here, we present a spatial and temporal analysis of the surface radiation budget and calculated variables from the pan-Arctic BSRN stations. Particular attention is given to inter

  7. Interaction of von Willebrand factor domains with collagen investigated by single molecule force spectroscopy

    Science.gov (United States)

    Posch, Sandra; Obser, Tobias; König, Gesa; Schneppenheim, Reinhard; Tampé, Robert; Hinterdorfer, Peter

    2018-03-01

    von Willebrand factor (VWF) is a huge multimeric protein that plays a key role in primary hemostasis. Sites for collagen binding, an initial event of hemostasis, are located in the VWF-domains A1 and A3. In this study, we investigated single molecule interactions between collagen surfaces and wild type VWF A1A2A3 domain constructs, as well as clinically relevant VWF A3 domain point mutations, such as p.Ser1731Thr, p.Gln1734His, and p.His1786Arg. For this, we utilized atomic force microscopy based single molecular force spectroscopy. The p.Ser1731Thr mutant had no impact on the VWF-collagen type III and VI interactions, while the p.Gln1734His and p.His1786Arg mutants showed a slight increase in bond stability to collagen type III. This effect probably arises from additional hydrogen bonds that come along with the introduction of these mutations. Using the same mutants, but collagen type VI as a binding partner, resulted in a significant increase in bond stability. VWF domain A1 was reported to be essential for the interaction with collagen type VI and thus our findings strengthen the hypothesis that the VWF A1 domain can compensate for mutations in the VWF A3 domain. Additionally, our data suggest that the mutations could even stabilize the interaction between VWF and collagen without shear. VWF-collagen interactions seem to be an important system in which defective interactions between one VWF domain and one type of collagen can be compensated by alternative binding events.

  8. A comparative analysis of strategic approaches for Information Technology (IT) for Commander Naval Surface Forces

    OpenAIRE

    Johnson, Devine R.

    2010-01-01

    Approved for public release; distribution is unlimited As the lead organization for all United States Naval Surface Forces, Commander Naval Surface Forces (CNSF) is committed to providing operational commanders with well-trained, highly effective, and technologically relevant surface forces. Aligning itself with the Department of the Navy's Information Management (IM) and Information Technology (IT) strategic mission objectives, CNSF is dedicated to delivering secure, interoperable, and in...

  9. Control of fingertip forces in young and older adults pressing against fixed low- and high-friction surfaces.

    Directory of Open Access Journals (Sweden)

    Kevin G Keenan

    Full Text Available Mobile computing devices (e.g., smartphones and tablets that have low-friction surfaces require well-directed fingertip forces of sufficient and precise magnitudes for proper use. Although general impairments in manual dexterity are well-documented in older adults, it is unclear how these sensorimotor impairments influence the ability of older adults to dexterously manipulate fixed, low-friction surfaces in particular. 21 young and 18 older (65+ yrs adults produced maximal voluntary contractions (MVCs and steady submaximal forces (2.5 and 10% MVC with the fingertip of the index finger. A Teflon covered custom-molded splint was placed on the fingertip. A three-axis force sensor was covered with either Teflon or sandpaper to create low- and high-friction surfaces, respectively. Maximal downward forces (F(z were similar (p = .135 for young and older adults, and decreased by 15% (p<.001 while pressing on Teflon compared to sandpaper. Fluctuations in F(z during the submaximal force-matching tasks were 2.45× greater (p<.001 for older adults than in young adults, and reached a maximum when older adults pressed against the Teflon surface while receiving visual feedback. These age-associated changes in motor performance are explained, in part, by altered muscle activity from three hand muscles and out-of-plane forces. Quantifying the ability to produce steady fingertip forces against low-friction surfaces may be a better indicator of impairment and disability than the current practice of evaluating maximal forces with pinch meters. These age-associated impairments in dexterity while interacting with low-friction surfaces may limit the use of the current generation of computing interfaces by older adults.

  10. Bimanual Lifting: Do Fingertip Forces Work Independently or Interactively?

    Science.gov (United States)

    Dimitriou, Pan; Buckingham, Gavin

    2018-01-01

    Bimanual coordination is a commonplace activity, but the consequences of using both hands simultaneously are not well understood. The authors examined fingertip forces across 4 experiments in which participants undertook a range of bimanual tasks. They first measured fingertip forces during simultaneous lifts of 2 identical objects, noting that individuals held the objects with more force bimanually than unimanually. They then varied the mass of the objects held by each hand, noting that when both hands lifted together performance was equivalent to unimanual lifts. The authors next measured one hand's static grip force while the other hand lifted an object. They found a gradual reduction of grip force throughout the trial, but once again no evidence of one hand influencing the other. In the final experiment the authors tested whether tapping with one hand could influence the static grip force of its counterpart. Although the authors found no changes in static grip force as a direct consequence of the other hand's actions, they found clear differences from one task to the other, suggesting an effect of task instruction. Overall, these results suggest that fingertip forces are largely independent between hands in a bimanual lifting context, but are sensitive to different task requirements.

  11. Direct measurement of colloidal interactions between polyaniline surfaces in a uv-curable coating formulation

    DEFF Research Database (Denmark)

    Jafarzadeh, Shadi; Claesson, Per M.; Pan, Jinshan

    2014-01-01

    The interactions between polyaniline particles and polyaniline surfaces in polyester acrylate resin mixed with 1,6-hexanediol diacrylate monomer have been investigated using contact angle measurements and the atomic force microscopy colloidal probe technique. Polyaniline with different characteri......The interactions between polyaniline particles and polyaniline surfaces in polyester acrylate resin mixed with 1,6-hexanediol diacrylate monomer have been investigated using contact angle measurements and the atomic force microscopy colloidal probe technique. Polyaniline with different...... cantilever and a pressed pellet of either hydrophilic or hydrophobic polyaniline powders, in resins of various polymer:monomer ratios. A short-range purely repulsive interaction was observed between hydrophilic polyaniline (doped with phosphoric acid) surfaces in polyester acrylate resin. In contrast...

  12. AFM Colloidal Probe Measurements Implicate Capillary Condensation in Punch-Particle Surface Interactions during Tableting.

    Science.gov (United States)

    Badal Tejedor, Maria; Nordgren, Niklas; Schuleit, Michael; Millqvist-Fureby, Anna; Rutland, Mark W

    2017-11-21

    Adhesion of the powders to the punches is a common issue during tableting. This phenomenon is known as sticking and affects the quality of the manufactured tablets. Defective tablets increase the cost of the manufacturing process. Thus, the ability to predict the tableting performance of the formulation blend before the process is scaled-up is important. The adhesive propensity of the powder to the tableting tools is mostly governed by the surface-surface adhesive interactions. Atomic force microscopy (AFM) colloidal probe is a surface characterization technique that allows the measurement of the adhesive interactions between two materials of interest. In this study, AFM steel colloidal probe measurements were performed on ibuprofen, MCC (microcrystalline cellulose), α-lactose monohydrate, and spray-dried lactose particles as an approach to modeling the punch-particle surface interactions during tableting. The excipients (lactose and MCC) showed constant, small, attractive, and adhesive forces toward the steel surface after a repeated number of contacts. In comparison, ibuprofen displayed a much larger attractive and adhesive interaction increasing over time both in magnitude and in jump-in/jump-out separation distance. The type of interaction acting on the excipient-steel interface can be related to a van der Waals force, which is relatively weak and short-ranged. By contrast, the ibuprofen-steel interaction is described by a capillary force profile. Even though ibuprofen is not highly hydrophilic, the relatively smooth surfaces of the crystals allow "contact flooding" upon contact with the steel probe. Capillary forces increase because of the "harvesting" of moisture-due to the fast condensation kinetics-leaving a residual condensate that contributes to increase the interaction force after each consecutive contact. Local asperity contacts on the more hydrophilic surface of the excipients prevent the flooding of the contact zone, and there is no such adhesive

  13. Modeling and experiments of the adhesion force distribution between particles and a surface.

    Science.gov (United States)

    You, Siming; Wan, Man Pun

    2014-06-17

    Due to the existence of surface roughness in real surfaces, the adhesion force between particles and the surface where the particles are deposited exhibits certain statistical distributions. Despite the importance of adhesion force distribution in a variety of applications, the current understanding of modeling adhesion force distribution is still limited. In this work, an adhesion force distribution model based on integrating the root-mean-square (RMS) roughness distribution (i.e., the variation of RMS roughness on the surface in terms of location) into recently proposed mean adhesion force models was proposed. The integration was accomplished by statistical analysis and Monte Carlo simulation. A series of centrifuge experiments were conducted to measure the adhesion force distributions between polystyrene particles (146.1 ± 1.99 μm) and various substrates (stainless steel, aluminum and plastic, respectively). The proposed model was validated against the measured adhesion force distributions from this work and another previous study. Based on the proposed model, the effect of RMS roughness distribution on the adhesion force distribution of particles on a rough surface was explored, showing that both the median and standard deviation of adhesion force distribution could be affected by the RMS roughness distribution. The proposed model could predict both van der Waals force and capillary force distributions and consider the multiscale roughness feature, greatly extending the current capability of adhesion force distribution prediction.

  14. Investigation of specific interactions between T7 promoter and T7 RNA polymerase by force spectroscopy using atomic force microscope.

    Science.gov (United States)

    Zhang, Xiaojuan; Yao, Zhixuan; Duan, Yanting; Zhang, Xiaomei; Shi, Jinsong; Xu, Zhenghong

    2018-01-11

    The specific recognition and binding of promoter and RNA polymerase is the first step of transcription initiation in bacteria and largely determines transcription activity. Therefore, direct analysis of the interaction between promoter and RNA polymerase in vitro may be a new strategy for promoter characterization, to avoid interference due to the cell's biophysical condition and other regulatory elements. In the present study, the specific interaction between T7 promoter and T7 RNA polymerase was studied as a model system using force spectroscopy based on atomic force microscope (AFM). The specific interaction between T7 promoter and T7 RNA polymerase was verified by control experiments, and the rupture force in this system was measured as 307.2 ± 6.7 pN. The binding between T7 promoter mutants with various promoter activities and T7 RNA polymerase was analyzed. Interaction information including rupture force, rupture distance and binding percentage were obtained in vitro , and reporter gene expression regulated by these promoters was also measured according to a traditional promoter activity characterization method in vivo Using correlation analysis, it was found that the promoter strength characterized by reporter gene expression was closely correlated with rupture force and the binding percentage by force spectroscopy. These results indicated that the analysis of the interaction between promoter and RNA polymerase using AFM-based force spectroscopy was an effective and valid approach for the quantitative characterization of promoters. © 2018 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society.

  15. Nanoscale imaging of the Candida-macrophage interaction using correlated fluorescence-atomic force microscopy.

    Science.gov (United States)

    El-Kirat-Chatel, Sofiane; Dufrêne, Yves F

    2012-12-21

    Knowledge of the molecular bases underlying the interaction of fungal pathogens with immune cells is critical to our understanding of fungal infections and offers exciting perspectives for controlling immune responses for therapy. Although fluorescence microscopy is a valuable tool to visualize pathogen-host interactions, the spatial resolution is low, meaning the fine structural details of the interacting cells cannot be observed. Here, we demonstrate the ability of correlated fluorescence-atomic force microscopy (AFM) to image the various steps of the interaction between fungal pathogens and macrophages with nanoscale resolution. We focus on Candida albicans, known to grow as two morphological forms (yeast cells, filamentous hyphae) that play important roles in modulating the interaction with macrophages. We observe the main steps of macrophage infection, including initial intercellular contact, phagocytosis by internalization of yeast cells, intracellular hyphal growth leading to mechanical stretching, and piercing of the macrophage membrane resulting in pathogen escape. While fluorescence imaging clearly distinguishes fungal cells from macrophages during the various steps of the process, AFM captures nanoscale structural features of the macrophage surface that are of high biological relevance, including ruffles, lamellipodia, filopodia, membrane remnants, and phagocytic cups. As fungal pathogenesis is mainly controlled by the ability of fungi to escape from immune cells, the nanoimaging platform established here has great potential in nanomedicine for understanding and controlling fungal infections.

  16. Role of different Skyrme forces and surface corrections in exotic ...

    Indian Academy of Sciences (India)

    Skyrme forces. Our study reveals that different Skyrme forces do not alter the transfer structure of fractional yields significantly. The cluster decay half-lives of different clusters lie within ±10% for preformed cluster models (PCM) and ±15% for unified fission models (UFM). Keywords. Heavy-ion reactions; cluster decay.

  17. Characterization of the Surface Morphology of Bacillus Spores by Atomic Force Microscopy

    National Research Council Canada - National Science Library

    Zolock, Ruth

    2002-01-01

    The surface morphology of Bacillus spores was resolved by atomic force microscopy in order to determine if characteristic surface features could be used to distinguish between closely related species...

  18. The structure of the interface in the solvent mediated interaction of dipolar surfaces

    International Nuclear Information System (INIS)

    Dzhavakhidze, P.G.; Levadny, V.G.

    1987-08-01

    Interaction of two dipolar surfaces separated by a polar medium is considered within the framework of nonlocal electrostatics. The dipolar surface layers are modelled as regular lattices with fixed orientation of dipoles which are immersed into the solvent; solvent response is characterized by nonlocal dielectric function. The model is elaborated in order to reveal the role of the dipolar layer discreteness in the electric field produced by one surface and the interaction between two surfaces (which gives rise to the so called ''hydration'' or ''structural'' force acting between mineral surfaces and phospholipid bilayers). The discreteness effects are present only for commensurate lattices. Their special mutual arrangement then may lead to considerable reduction of structural forces, viz. the usual repulsion regime may change at short distances to attraction. Conditions are considered when repulsion is entirely replaced by attraction, i.e. the ''hydration barrier'' disappears. In appended note we discuss the role of solvation of surface dipolar groups. We propose an explanation of why two modes of decay (one with oscillative fine structure) may be present in the dependence of the force upon distance if the surface dipolar groups are immersed deep enough in the solvent and how the long-range oscillative mode disappears when the surface is but weakly solvated. (author). 35 refs, 5 figs

  19. Dependence of capillary forces on relative humidity and the surface properties of femtosecond laser micromachined titanium.

    Science.gov (United States)

    Lehr, Jorge; Kietzig, Anne-Marie

    2015-06-15

    Capillary forces were measured with colloidal atomic force microscopy at different levels of relative humidity on femtosecond laser micromachined titanium surfaces. After laser machining at different intensity levels, the titanium surfaces show a nanoscale ripple topology or microscopic bumpy structures. Different machining environments were chosen to influence the surface chemistry in addition to topology: while machining in pure oxygen and water resulted in surfaces consisting of TiO2, a composite surface of TiO2 and TiN was obtained after machining in pure nitrogen. All samples were subsequently exposed to pure oxygen, carbon dioxide or water, and showed different levels of wettability and capillary force. We have introduced the concept of humidity sensitivity as the relative increase of the capillary force with respect to the measured force at 0% humidity. We report that samples with a nanoscale ripple topology machined in pure oxygen exhibit the lowest level of capillary force and the lowest sensitivity towards humidity in the environment. Surfaces with low sensitivity towards changes of the relative humidity are good candidates for technical applications, where capillary forces have to be controlled. This study contributes to the development of such surfaces, to a better understanding of how capillary bridges are formed on rough surfaces and ultimately to the exploration of the relationship between surface wettability and capillary forces. Copyright © 2015 Elsevier Inc. All rights reserved.

  20. Effect of forced convection on the collision and interaction between nanoparticles and ultramicroelectrode.

    Science.gov (United States)

    Jiang, Jing; Huang, Xinjian; Wang, Lishi

    2016-04-01

    Detection of nanoparticle (NP) collision events at ultramicroelectrode (UME) has emerged as a new methodology for the investigation of single NP in recent years. Although the method was widely employed, some fundamental knowledge such as how the NP moves to and interacts with the UME remain less understood. It was generally recognized that the recorded rate of collision was determined by diffusion that should follow Fick's first law. However, significant lower collision frequency compared with that of predicted by theory were frequently reported. Experiments carried out by us suggest that the collision frequency will increase dramatically if forced convection (stir or flow injection) is applied during detection. Furthermore, the collision frequency gradually increases to a maximum and then decreases, along with the increase of the convection intensity. This phenomenon is interpreted as follows: (a) there are two steps for a freely moving NP to generate a detectable collision signal. The first step is the move of NP from bulk solution to the surface of the UME which is mass transfer limited; the second step is the landing of NP on the surface of UME which is affected by many factors and is the critical step; (b) there is a barrier that must be overcame before the contact between freely moving NP and UME. Forced convection with moderate intensity can not only increase the mass transfer rate but also help to overcome this barrier and thus enhance the collision frequency; (c) the landing of NP on the surface of UME can be suppressed by stronger convections, because NP will be swept away by hydrodynamic force. Copyright © 2016 Elsevier Inc. All rights reserved.

  1. Biological and environmental surface interactions of nanomaterials: characterization, modeling, and prediction.

    Science.gov (United States)

    Chen, Ran; Riviere, Jim E

    2017-05-01

    The understanding of nano-bio interactions is deemed essential in the design, application, and safe handling of nanomaterials. Proper characterization of the intrinsic physicochemical properties, including their size, surface charge, shape, and functionalization, is needed to consider the fate or impact of nanomaterials in biological and environmental systems. The characterizations of their interactions with surrounding chemical species are often hindered by the complexity of biological or environmental systems, and the drastically different surface physicochemical properties among a large population of nanomaterials. The complexity of these interactions is also due to the diverse ligands of different chemical properties present in most biomacromolecules, and multiple conformations they can assume at different conditions to minimize their conformational free energy. Often these interactions are collectively determined by multiple physical or chemical forces, including electrostatic forces, hydrogen bonding, and hydrophobic forces, and calls for multidimensional characterization strategies, both experimentally and computationally. Through these characterizations, the understanding of the roles surface physicochemical properties of nanomaterials and their surface interactions with biomacromolecules can play in their applications in biomedical and environmental fields can be obtained. To quantitatively decipher these physicochemical surface interactions, computational methods, including physical, statistical, and pharmacokinetic models, can be used for either analyses of large amounts of experimental characterization data, or theoretical prediction of the interactions, and consequent biological behavior in the body after administration. These computational methods include molecular dynamics simulation, structure-activity relationship models such as biological surface adsorption index, and physiologically-based pharmacokinetic models. WIREs Nanomed Nanobiotechnol 2017

  2. Interaction particles from the surface of the curved pipeline

    Directory of Open Access Journals (Sweden)

    Vasilevsky Michail

    2017-01-01

    Full Text Available The interaction of the agglomerated fine dust particles from the surface of the rotary pyleprovoda, given deposit formation evaluation. The interaction of large particles to the surface of the rotary pyleprovoda. The analysis of hydrodynamic phenomena in the means of protection against wear.

  3. Definition of interaction force between car wheel and rough road while driving

    Directory of Open Access Journals (Sweden)

    Polyakov V.M.

    2016-08-01

    Full Text Available For the calculation of indicators of operational properties of a car moving on a rough road, in most cases it is necessary to know the support reactions on the wheels of the vehicle and changing depending on mode of motion. In this connection, there arises an interest in determining strength of the central plane of rotation of the car wheel while driving over uneven at different speeds its movement. A mathematical model for definition of force in the central plane of rotation wheel at uniform rectilinear movements of the car on the support surface with single sinusoidal roughness, was developed. Parameters of mass and geometric parameters of the car and asperity, elastic and dissipative properties of the suspension and tires are taken into account. Results of investigation of interaction of car wheel and single sinusoidal roughness at uniform rectilinear movements Renault 15TS with different speeds, was presented. The plots to assess the influence of vehicle speed on rough roads on the strength of interaction force between car wheel and rough road are presented.

  4. Local triboelectrification of an n-GaAs surface using the tip of an atomic-force microscope

    Energy Technology Data Exchange (ETDEWEB)

    Brunkov, P. N., E-mail: brunkov@mail.ioffe.ru; Goncharov, V. V.; Rudinsky, M. E.; Gutkin, A. A.; Gordeev, N. Yu.; Lantratov, V. M.; Kalyuzhnyy, N. A.; Mintairov, S. A.; Sokolov, R. V.; Konnikov, S. G. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

    2013-09-15

    The method of scanning Kelvin-probe microscopy is used to show that the effect of triboelectrification is observed when the tip of an atomic-force microscope interacts with the surface of n-GaAs epitaxial layers. The sign of the change in the potential indicates that the sample surface after triboelectrification becomes more negative. The observed specific features of the phenomena can be attributed to the thermally activated generation of point defects in the vicinity of the sample surface due to deformation caused by the tip.

  5. Reverse engineering of an affinity-switchable molecular interaction characterized by atomic force microscopy single-molecule force spectroscopy.

    Science.gov (United States)

    Anselmetti, Dario; Bartels, Frank Wilco; Becker, Anke; Decker, Björn; Eckel, Rainer; McIntosh, Matthew; Mattay, Jochen; Plattner, Patrik; Ros, Robert; Schäfer, Christian; Sewald, Norbert

    2008-02-19

    Tunable and switchable interaction between molecules is a key for regulation and control of cellular processes. The translation of the underlying physicochemical principles to synthetic and switchable functional entities and molecules that can mimic the corresponding molecular functions is called reverse molecular engineering. We quantitatively investigated autoinducer-regulated DNA-protein interaction in bacterial gene regulation processes with single atomic force microscopy (AFM) molecule force spectroscopy in vitro, and developed an artificial bistable molecular host-guest system that can be controlled and regulated by external signals (UV light exposure and thermal energy). The intermolecular binding functionality (affinity) and its reproducible and reversible switching has been proven by AFM force spectroscopy at the single-molecule level. This affinity-tunable optomechanical switch will allow novel applications with respect to molecular manipulation, nanoscale rewritable molecular memories, and/or artificial ion channels, which will serve for the controlled transport and release of ions and neutral compounds in the future.

  6. The impact of the competitive adsorption of ions at surface sites on surface free energies and surface forces

    Science.gov (United States)

    Parsons, Drew F.; Salis, Andrea

    2015-04-01

    The relationship between surface charge and surface potential at the solid-liquid interface is often determined by a charge regulation process, the chemisorption of a potential determining ion such as H+. A subtle ion-specific effect can be observed when other ions compete with the primary potential determining ion to bind to a surface site. Site competition may involve alternative ions competing for a first binding site, e.g., metals ions competing with H+ to bind to a negatively charged oxide or carboxyl site. Second-binding sites with site competition may also be found, including amphoteric OH2+ sites, or anion binding to amine groups. In this work, a general theoretical model is developed to describe the competitive adsorption of ions at surface sites. Applied to the calculation of forces, the theory predicts a 20% increase in repulsion between titania surfaces in 1 mM NaCl, and a 25% reduction in repulsion between silica surfaces in 0.1M NaCl compared to calculations neglecting ion site competition.

  7. Biomaterial surface proteomic signature determines interaction with epithelial cells.

    Science.gov (United States)

    Abdallah, Mohamed-Nur; Tran, Simon D; Abughanam, Ghada; Laurenti, Marco; Zuanazzi, David; Mezour, Mohamed A; Xiao, Yizhi; Cerruti, Marta; Siqueira, Walter L; Tamimi, Faleh

    2017-05-01

    Cells interact with biomaterials indirectly through extracellular matrix (ECM) proteins adsorbed onto their surface. Accordingly, it could be hypothesized that the surface proteomic signature of a biomaterial might determine its interaction with cells. Here, we present a surface proteomic approach to test this hypothesis in the specific case of biomaterial-epithelial cell interactions. In particular, we determined the surface proteomic signature of different biomaterials exposed to the ECM of epithelial cells (basal lamina). We revealed that the biomaterial surface chemistry determines the surface proteomic profile, and subsequently the interaction with epithelial cells. In addition, we found that biomaterials with surface chemistries closer to that of percutaneous tissues, such as aminated PMMA and aminated PDLLA, promoted higher selective adsorption of key basal lamina proteins (laminins, nidogen-1) and subsequently improved their interactions with epithelial cells. These findings suggest that mimicking the surface chemistry of natural percutaneous tissues can improve biomaterial-epithelial integration, and thus provide a rationale for the design of improved biomaterial surfaces for skin regeneration and percutaneous medical devices. Failure of most biomaterials originates from the inability to predict and control the influence of their surface properties on biological phenomena, particularly protein adsorption, and cellular behaviour, which subsequently results in unfavourable host response. Here, we introduce a surface-proteomic screening approach using a label-free mass spectrometry technique to decipher the adsorption profile of extracellular matrix (ECM) proteins on different biomaterials, and correlate it with cellular behaviour. We demonstrated that the way a biomaterial selectively interacts with specific ECM proteins of a given tissue seems to determine the interactions between the cells of that tissue and biomaterials. Accordingly, this approach can

  8. Magnetostatic interactions and forces between cylindrical permanent magnets

    Czech Academy of Sciences Publication Activity Database

    Vokoun, David; Beleggia, M.; Heller, Luděk; Šittner, Petr

    2009-01-01

    Roč. 321, č. 22 (2009), s. 3758-3763 ISSN 0304-8853 EU Projects: European Commission(XE) 46559 - CERINKA Institutional research plan: CEZ:AV0Z10100520 Keywords : cylinder * force measurement * magnet ostatic * permanent magnet Subject RIV: BM - Solid Matter Physics ; Magnet ism Impact factor: 1.204, year: 2009

  9. Interaction between force production and cognitive performance in humans

    NARCIS (Netherlands)

    Zijdewind, Inge; van Duinen, Hiske; Zielman, R; Lorist, MM

    Objective: A dual task paradigm was used to examine the effects of the generation of force on cognitive performance. Methods: Subjects (n = 22) were asked to respond to auditory stimuli with their left middle or index finger and concurrently maintain a sub-maximal contraction with their right index

  10. Nonperturbative theory of atom-surface interaction: corrections at short separations.

    Science.gov (United States)

    Bordag, M; Klimchitskaya, G L; Mostepanenko, V M

    2018-02-07

    The nonperturbative expressions for the free energy and force of interaction between a ground-state atom and a real-material surface at any temperature are presented. The transition to the Matsubara representation is performed, whereupon the comparison is made with the commonly used perturbative results based on the standard Lifshitz theory. It is shown that the Lifshitz formulas for the free energy and force of an atom-surface interaction follow from the nonperturbative ones in the lowest order of the small parameter. Numerical computations of the free energy and force for the atoms of He[Formula: see text] and Na interacting with a surface of an Au plate have been performed using the frequency-dependent dielectric permittivity of Au and highly accurate dynamic atomic polarizabilities in the framework of both the nonperturbative and perturbative theories. According to our results, the maximum deviations between the two theories are reached at the shortest atom-surface separations of about 1 nm. Simple analytic expressions for the atom-surface free energy are derived in the classical limit and for an ideal-metal plane. In the lowest order of the small parameter, they are found in agreement with the perturbative ones following from the standard Lifshitz theory. Possible applications of the obtained results in the theory of van der Waals adsorption are discussed.

  11. Incorporating contact angles in the surface tension force with the ACES interface curvature scheme

    Science.gov (United States)

    Owkes, Mark

    2017-11-01

    In simulations of gas-liquid flows interacting with solid boundaries, the contact line dynamics effect the interface motion and flow field through the surface tension force. The surface tension force is directly proportional to the interface curvature and the problem of accurately imposing a contact angle must be incorporated into the interface curvature calculation. Many commonly used algorithms to compute interface curvatures (e.g., height function method) require extrapolating the interface, with defined contact angle, into the solid to allow for the calculation of a curvature near a wall. Extrapolating can be an ill-posed problem, especially in three-dimensions or when multiple contact lines are near each other. We have developed an accurate methodology to compute interface curvatures that allows for contact angles to be easily incorporated while avoiding extrapolation and the associated challenges. The method, known as Adjustable Curvature Evaluation Scale (ACES), leverages a least squares fit of a polynomial to points computed on the volume-of-fluid (VOF) representation of the gas-liquid interface. The method is tested by simulating canonical test cases and then applied to simulate the injection and motion of water droplets in a channel (relevant to PEM fuel cells).

  12. Workplace surfaces as resource for social interactions

    NARCIS (Netherlands)

    Vyas, Dhaval; Nijholt, Antinus; Nishida, T.

    2009-01-01

    Space and spatial arrangements play an important role in our everyday social interactions. The way we use and manage our surrounding space is not coincidental, on the contrary, it reflects the way we think, plan and act. Within collaborative contexts, its ability to support social activities makes

  13. Protein-Ligand Informatics Force Field (PLIff): Toward a Fully Knowledge Driven "Force Field" for Biomolecular Interactions.

    Science.gov (United States)

    Verdonk, Marcel L; Ludlow, R Frederick; Giangreco, Ilenia; Rathi, Prakash Chandra

    2016-07-28

    The Protein Data Bank (PDB) contains a wealth of data on nonbonded biomolecular interactions. If this information could be distilled down to nonbonded interaction potentials, these would have some key advantages over standard force fields. However, there are some important outstanding issues to address in order to do this successfully. This paper introduces the protein-ligand informatics "force field", PLIff, which begins to address these key challenges ( https://bitbucket.org/AstexUK/pli ). As a result of their knowledge-based nature, the next-generation nonbonded potentials that make up PLIff automatically capture a wide range of interaction types, including special interactions that are often poorly described by standard force fields. We illustrate how PLIff may be used in structure-based design applications, including interaction fields, fragment mapping, and protein-ligand docking. PLIff performs at least as well as state-of-the art scoring functions in terms of pose predictions and ranking compounds in a virtual screening context.

  14. Aerosol Direct Radiative Forcing and Forcing Efficiencies at Surface from the shortwave Irradiance Measurements in Abu Dhabi, UAE

    Science.gov (United States)

    Beegum S, N.; Ben Romdhane, H.; Ghedira, H.

    2013-12-01

    Atmospheric aerosols are known to affect the radiation balance of the Earth-Atmospheric system directly by scattering and absorbing the solar and terrestrial radiation, and indirectly by affecting the lifetime and albedo of the clouds. Continuous and simultaneous measurements of short wave global irradiance in combination with synchronous spectral aerosol optical depth (AOD) measurements (from 340 nm to 1640 nm in 8 channels), for a period of 1 year from June 2012 to May 2013, were used for the determination of the surface direct aerosol radiative forcing and forcing efficiencies under cloud free conditions in Abu Dhabi (24.42°N, 54.61o E, 7m MSL), a coastal location in United Arab Emirates (UAE) in the Arabian Peninsula. The Rotating Shadow band Pyranometer (RSP, LI-COR) was used for the irradiance measurements (in the spectral region 400-1100 nm), whereas the AOD measurements were carried out using CIMEL Sunphotometer (CE 318-2, under AERONET program). The differential method, which is neither sensitive to calibration uncertainties nor model assumptions, has been employed for estimating forcing efficiencies from the changes in the measured fluxes. The forcing efficiency, which quantifies the net change in irradiance per unit change in AOD, is an appropriate parameter for the characterization of the aerosol radiative effects even if the microphysical and optical properties of the aerosols are not completely understood. The corresponding forcing values were estimated from the forcing efficiencies. The estimated radiative forcing and forcing efficiencies exhibited strong monthly variations. The forcing efficiencies (absolute magnitudes) were highest during March, and showed continuous decrease thereafter to reach the lowest value during September. In contrast, the forcing followed a slightly different pattern of variability, with the highest solar dimming during April ( -60 W m-2) and the minimum during February ( -20 W m-2). The results indicate that the aerosol

  15. Forced heat loss from body surface reduces heat flow to body surface.

    Science.gov (United States)

    Berman, A

    2010-01-01

    Heat stress is commonly relieved by forced evaporation from body surfaces. The mode of heat stress relief by heat extraction from the periphery is not clear, although it reduces rectal temperature. Radiant surface temperature (Ts) of the right half of the body surface was examined by thermovision in 4 lactating Holstein cows (30 kg of milk/d) during 7 repeated cycles of forced evaporation created by 30s of wetting followed by 4.5 min of forced airflow. Wetting was performed by an array of sprinklers (0.76 m(3)/h), and forced airflow (>3m/s velocity) over the right side of the body surface was produced by fans mounted at a height of 3m above the ground. Sprinkling wetted the hind legs, rump, and chest, but not the lower abdomen side, front legs, or neck. The animals were maintained in shade at an air temperature of 28 degrees C and relative humidity of 47%. Coat thickness was 1 to 2mm, so Ts closely represented skin temperature. Mean Ts of 5 x 20cm areas on the upper and lower hind and front legs, rump, chest, abdomen side, and neck were obtained by converting to temperature their respective gray intensity in single frames obtained at 10-s intervals. Little change occurred in Ts during the first wetting (0.1+/-0.6 degrees C), but it decreased rapidly thereafter (1.6+/-0.6 degrees C in the fifth wetting). The Ts also decreased, to a smaller extent, in areas that remained dry (0.7+/-1.0 degrees C). In all body sites, a plateau in Ts was reached by 2 min after wetting. The difference between dry and wet areas in the first cooling cycle was approximately 1.2 degrees C. The Ts of different body areas decreased during consecutive cooling cycles and reached a plateau by 3 cooling cycles in dry sites (front leg, neck, abdomen side), by 5 cooling cycles in the hind leg, and 7 cooling cycles in the rump and chest. The reduction in mean Ts produced by 7 cycles was 4.0 to 6.0 degrees C in wetted areas and 1.6 to 3.7 degrees C in sites that were not wetted. Initial rectal

  16. The Röntgen interaction and forces on dipoles in time-modulated optical fields

    Science.gov (United States)

    Sonnleitner, Matthias; Barnett, Stephen M.

    2017-12-01

    The Röntgen term is an often neglected contribution to the interaction between an atom and an electromagnetic field in the electric dipole approximation. In this work we discuss how this interaction term leads to a difference between the kinetic and canonical momentum of an atom which, in turn, leads to surprising radiation forces acting on the atom. We use a number of examples to explore the main features of this interaction, namely forces acting against the expected dipole force or accelerations perpendicular to the beam propagation axis.

  17. Regulating DNA Self-assembly by DNA-Surface Interactions.

    Science.gov (United States)

    Liu, Longfei; Li, Yulin; Wang, Yong; Zheng, Jianwei; Mao, Chengde

    2017-12-14

    DNA self-assembly provides a powerful approach for preparation of nanostructures. It is often studied in bulk solution and involves only DNA-DNA interactions. When confined to surfaces, DNA-surface interactions become an additional, important factor to DNA self-assembly. However, the way in which DNA-surface interactions influence DNA self-assembly is not well studied. In this study, we showed that weak DNA-DNA interactions could be stabilized by DNA-surface interactions to allow large DNA nanostructures to form. In addition, the assembly can be conducted isothermally at room temperature in as little as 5 seconds. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Radiative forcing by changes in surface albedo caused by changes in vegetation

    OpenAIRE

    Kvalevåg, Maria Malene

    2005-01-01

    The human influence on vegetation causes changes in the surface reflective properties. By using MODIS land cover and MODIS surface albedo products, an estimation of radiative forcing due to surface albedo changes caused by vegetation changes is performed. A potential natural vegetation data set is used to compute radiative forcing estimates from pre agricultural times to present. A combination between MODIS blacksky and whitesky albedo and diffuse and direct radiation at gr...

  19. Terahertz instability of surface optical-phonon polaritons that interact with surface plasmon polaritons in the presence of electron drift

    International Nuclear Information System (INIS)

    Sydoruk, O.; Solymar, L.; Shamonina, E.; Kalinin, V.

    2010-01-01

    Traveling-wave interaction between optical phonons and electrons drifting in diatomic semiconductors has potential for amplification and generation of terahertz radiation. Existing models of this interaction were developed for infinite materials. As a more practically relevant configuration, we studied theoretically a finite semiconductor slab surrounded by a dielectric. This paper analyzes the optical-phonon instability in the slab including the Lorentz force and compares it to the instability in an infinite material. As the analysis shows, the slab instability occurs because of the interaction of surface optical-phonon polaritons with surface plasmon polaritons in the presence of electron drift. The properties of the instability depend on the slab thickness when the thickness is comparable to the wavelength. For large slab thicknesses, however, the dispersion relation of the slab is similar to that of an infinite material, although the coupling is weaker. The results could be used for the design of practical terahertz traveling-wave oscillators and amplifiers.

  20. MODELING THE INTERACTION OF AGROCHEMICALS WITH ENVIRONMENTAL SURFACES: PESTICIDES ON RUTILE AND ORGANO-RUTILE SURFACES

    Science.gov (United States)

    Non-bonded interactions between model pesticides and organo-mineral surfaces have been studied using molecular mechanical conformational calculations and molecular dynamics simulations. The minimum energy conformations and relative binding energies for the interaction of atrazine...

  1. Forces involved in bacterial adhesion to hydrophilic and hydrophobic surfaces

    NARCIS (Netherlands)

    Boks, N.P.; Norde, W.; Meil, H.C.; Busscher, H.J.

    2008-01-01

    Using a parallel-plate flow chamber, the hydrodynamic shear forces to prevent bacterial adhesion (F-prev) and to detach adhering bacteria (F-det) were evaluated for hydrophilic glass, hydrophobic, dimethyldichlorosilane (DDS)-coated glass and six different bacterial strains, in order to test the

  2. Forces involved in bacterial adhesion to hydrophilic and hydrophobic surfaces

    NARCIS (Netherlands)

    Boks, Niels P.; Norde, Willem; van der Mei, Henny C.; Busscher, Henk J.

    2008-01-01

    Using a parallel-plate flow chamber, the hydrodynamic shear forces to prevent bacterial adhesion (F(prev)) and to detach adhering bacteria (F(det)) were evaluated for hydrophilic glass, hydrophobic, dimethyldichlorosilane (DDS)-coated glass and six different bacterial strains, in order to test the

  3. Coevolution of bed surface patchiness and channel morphology: 1. Mechanisms of forced patch formation

    Science.gov (United States)

    Nelson, Peter A.; McDonald, Richard R.; Nelson, Jonathan M.; Dietrich, William E.

    2015-01-01

    Riverbeds frequently display a spatial structure where the sediment mixture composing the channel bed has been sorted into discrete patches of similar grain size. Even though patches are a fundamental feature in gravel bed rivers, we have little understanding of how patches form, evolve, and interact. Here we present a two-dimensional morphodynamic model that is used to examine in greater detail the mechanisms responsible for the development of forced bed surface patches and the coevolution of bed morphology and bed surface patchiness. The model computes the depth-averaged channel hydrodynamics, mixed-grain-size sediment transport, and bed evolution by coupling the river morphodynamic model Flow and Sediment Transport with Morphological Evolution of Channels (FaSTMECH) with a transport relation for gravel mixtures and the mixed-grain-size Exner equation using the active layer assumption. To test the model, we use it to simulate a flume experiment in which the bed developed a sequence of alternate bars and temporally and spatially persistent forced patches with a general pattern of coarse bar tops and fine pools. Cross-stream sediment flux causes sediment to be exported off of bars and imported into pools at a rate that balances downstream gradients in the streamwise sediment transport rate, allowing quasi-steady bar-pool topography to persist. The relative importance of lateral gravitational forces on the cross-stream component of sediment transport is a primary control on the amplitude of the bars. Because boundary shear stress declines as flow shoals over the bars, the lateral sediment transport is increasingly size selective and leads to the development of coarse bar tops and fine pools.

  4. Direct measurement of interaction forces between a platinum dichloride complex and DNA molecules.

    Science.gov (United States)

    Muramatsu, Hiroshi; Shimada, Shogo; Okada, Tomoko

    2017-09-01

    The interaction forces between a platinum dichloride complex and DNA molecules have been studied using atomic force microscopy (AFM). The platinum dichloride complex, di-dimethylsulfoxide-dichloroplatinum (II) (Pt(DMSO) 2 Cl 2 ), was immobilized on an AFM probe by coordinating the platinum to two amino groups to form a complex similar to Pt(en)Cl 2 , which is structurally similar to cisplatin. The retraction forces were measured between the platinum complex and DNA molecules immobilized on mica plates using force curve measurements. The histogram of the retraction force for λ-DNA showed several peaks; the unit retraction force was estimated to be 130 pN for a pulling rate of 60 nm/s. The retraction forces were also measured separately for four single-base DNA oligomers (adenine, guanine, thymine, and cytosine). Retraction forces were frequently observed in the force curves for the DNA oligomers of guanine and adenine. For the guanine DNA oligomer, the most frequent retraction force was slightly lower than but very similar to the retraction force for λ-DNA. A higher retraction force was obtained for the adenine DNA oligomer than for the guanine oligomer. This result is consistent with a higher retraction activation energy of adenine with the Pt complex being than that of guanine because the kinetic rate constant for retraction correlates to exp(FΔx - ΔE) where ΔE is an activation energy, F is an applied force, and Δx is a displacement of distance.

  5. An Experimental Study On Drill Vibration Thrust Force And Surface Roughness In Drilling Of SCFCarbon Fibre Composite

    Directory of Open Access Journals (Sweden)

    B. Amar Babu

    2017-07-01

    Full Text Available In the present work SCFcarbon composite was prepared with a commercially available vinylester methyl ethyl ketone peroxide catalyst and cobalt napthenate accelerator. The prepared composite is aimed to use in aircraft application. The composite is treated to improve the characteristics of SCFCarbon. Drilling characteristics were studied for both treated and untreated composites. As per Taguchi orthogonal array of L8 eight experiments were conducted on the composites and machining characteristics like thrust force surface roughness and amplitude of drill vibration were measured. Interaction effect of parameter on the machine characteristics was studied using response surface methodology. Analysis of variance was also used to identify significant parameters for the three machining characteristics. A multi response optimization technique was used to optimise parameters for minimization of thrust force surface roughness and amplitude of drill vibration.

  6. Surface EMG and intra-socket force measurement to control a prosthetic device

    Science.gov (United States)

    Sanford, Joe; Patterson, Rita; Popa, Dan

    2015-06-01

    Surface electromyography (SEMG) has been shown to be a robust and reliable interaction method allowing for basic control of powered prosthetic devices. Research has shown a marked decrease in EMG-classification efficiency throughout activities of daily life due to socket shift and movement and fatigue as well as changes in degree of fit of the socket throughout the subject's lifetime. Users with the most severe levels of amputation require the most complex devices with the greatest number of degrees of freedom. Controlling complex dexterous devices with limited available inputs requires the addition of sensing and interaction modalities. However, the larger the amputation severity, the fewer viable SEMG sites are available as control inputs. Previous work reported the use of intra-socket pressure, as measured during wrist flexion and extension, and has shown that it is possible to control a powered prosthetic device with pressure sensors. In this paper, we present data correlations of SEMG data with intra-socket pressure data. Surface EMG sensors and force sensors were housed within a simulated prosthetic cuff fit to a healthy-limbed subject. EMG and intra-socket force data was collected from inside the cuff as a subject performed pre-defined grip motions with their dominant hand. Data fusion algorithms were explored and allowed a subject to use both intra-socket pressure and SEMG data as control inputs for a powered prosthetic device. This additional input modality allows for an improvement in input classification as well as information regarding socket fit through out activities of daily life.

  7. Single-ion and pair-interaction potentials near simple metal surfaces

    International Nuclear Information System (INIS)

    Barnett, R.N.; Barrera, R.G.; Cleveland, C.L.; Landman, U.

    1983-01-01

    Presented is a model for semi-infinite simple metals which does not require crystalline order or a single species, and thus is applicable to problems of defect energetics near the surface and random-alloy surfaces as well as ideal metal surfaces. The formulation is based on the use of ionic pseudopotentials and linear-response theory. An expression for the total energy is obtained which depends explicitly on ionic species and position. This expression is decomposed into a density-dependent term and single-ion and ionic pair-interaction potential terms. The single-ion potentials oscillate about a constant bulk value, with the magnitude of the oscillation decreasing rapidly away from the surface. The interaction between pairs of ions near the surface is shown to be a noncentral force interaction which differs significantly from the central-force bulk pair potential. The effect of quantum interference in the response of the semi-infinite electron gas to the ions is seen in both the single-ion and the pair-interaction potentials. Results are presented for the simple metals sodium, potassium, and rubidium

  8. Atomic force microscopy characterization of the surface wettability of natural fibres

    International Nuclear Information System (INIS)

    Pietak, Alexis; Korte, Sandra; Tan, Emelyn; Downard, Alison; Staiger, Mark P.

    2007-01-01

    Natural fibres represent a readily available source of ecologically friendly and inexpensive reinforcement in composites with degradable thermoplastics, however chemical treatments of fibres are required to prepare feasible composites. It is desirable to characterize the surface wettability of fibres after chemical treatment as the polarity of cellulose-based fibres influences compatibility with a polymer matrix. Assessment of the surface wettability of natural fibres using conventional methods presents a challenge as the surfaces are morphologically and chemically heterogeneous, rough, and can be strongly wicking. In this work it is shown that under atmospheric conditions the adhesion force between an atomic force microscopy (AFM) tip and the fibre surface can estimate the water contact angle and surface wettability of the fibre. AFM adhesion force measurements are suitable for the more difficult surfaces of natural fibres and in addition allow for correlations between microstructural features and surface wettability characteristics

  9. Investigation of graphite composite anodes surfaces by atomic force microscopy and related techniques

    Energy Technology Data Exchange (ETDEWEB)

    Hirasawa, Karen Akemi; Nishioka, Keiko; Sato, Tomohiro; Yamaguchi, Shoji; Mori, Shoichiro [Mitsubishi Chemical Corp., Tsukuba Research Center, Ibaraki (Japan)

    1997-11-01

    The surface of a synthetic graphite (KS-44) and polyvinylidene difluoride binder (PVDF) anode for lithium-ion secondary batteries is imaged using atomic force microscopy (AFM) and several related scanning probe microscope (SPM) instruments including: dynamic force microscopy (DFM), friction force microscopy (FFM), laterally-modulated friction force microscopy (LM-FFM), visco-elasticity atomic force microscopy (VE-AFM), and AFM/simultaneous current measurement mode (SCM). DFM is found to be an exceptional mode for topographic imaging while FFM results in the clearest contrast distinction between PVDF binder and KS-44 graphite regions. (orig.)

  10. PISCES program plasma-surface interactions research

    International Nuclear Information System (INIS)

    1989-05-01

    This paper discusses the following about the Pisces program: Major objectives of the program; Staff in the PISCES program at UCLA; Highlights in the program; Collaborations with other institutions; PISCES-A facility; PISCES-B facility; Fast scanning Langmuir probe; Omegatron mass spectrometer; Spectroscopic diagnostics; Data acquisition system; Redeposition effect on carbon chemical erosion; Erosion of carbon tokamakium from TFTR; Effect of boron-doping on carbon chemical erosion; Radiation enhanced sublimation of carbon; Surface analysis of TEXTOR titles; Spectroscopic analysis of carbon impurities; Biased limiter and divertor; Biased divertor channel; Gaseous divertor experiments; Presheath profile measurements; Particle transport in CCT tokamak; and Biased divertor experiments in CCT

  11. Atomic force microscopy imaging and single molecule recognition force spectroscopy of coat proteins on the surface of Bacillus subtilis spore.

    Science.gov (United States)

    Tang, Jilin; Krajcikova, Daniela; Zhu, Rong; Ebner, Andreas; Cutting, Simon; Gruber, Hermann J; Barak, Imrich; Hinterdorfer, Peter

    2007-01-01

    Coat assembly in Bacillus subtilis serves as a tractable model for the study of the self-assembly process of biological structures and has a significant potential for use in nano-biotechnological applications. In the present study, the morphology of B. subtilis spores was investigated by magnetically driven dynamic force microscopy (MAC mode atomic force microscopy) under physiological conditions. B. subtilis spores appeared as prolate structures, with a length of 0.6-3 microm and a width of about 0.5-2 microm. The spore surface was mainly covered with bump-like structures with diameters ranging from 8 to 70 nm. Besides topographical explorations, single molecule recognition force spectroscopy (SMRFS) was used to characterize the spore coat protein CotA. This protein was specifically recognized by a polyclonal antibody directed against CotA (anti-CotA), the antibody being covalently tethered to the AFM tip via a polyethylene glycol linker. The unbinding force between CotA and anti-CotA was determined as 55 +/- 2 pN. From the high-binding probability of more than 20% in force-distance cycles it is concluded that CotA locates in the outer surface of B. subtilis spores. Copyright (c) 2007 John Wiley & Sons, Ltd.

  12. An atomic force microscopy study of the interactions between indolicidin and supported planar bilayers

    DEFF Research Database (Denmark)

    Askou, Hans Jakob; Jakobsen, Rasmus Neergaard; Fojan, Peter

    2008-01-01

    Indolicidin, a tryptophane-rich antimicrobial peptide , was used to investigate the interactions with a zwitterionic phosphatidylcholine as a model membrane system. In situ atomic force microscopy in liquid medium and phosphatidylcholine supported planar bilayers enabled the study...

  13. Constraining Aerosol Forcing from the Land Surface Temperature Record

    Science.gov (United States)

    Shen, Z.; Ming, Y.; Held, I.

    2017-12-01

    Understanding the anthropogenic influence on regional climate change is important for policy making and adaption planning. Atmosphere/land global climate models (AGCMs) with prescribed oceanic boundary conditions allow a decomposition of historical climate change into a fast component that occurs on an atmospheric adjustment time scale of a month or less, and a slow component due to the changing ocean and sea ice. These two components are simultaneously present in comprehensive coupled climate models. The slow component contains much of the uncertainty in climate sensitivity and is where the forced signals are mixed most strongly with natural variability. Here we use AGCMs to investigate the fast component of the anthropogenic influence on regional temperature change. Although this fast component of the anthropogenic warming is often thought of as small, we find that it is detectable in the observed warming of Northern Hemisphere land during the warm season in recent decades. We suggest that the fast response to aerosol forcing in isolation can be detected on subcontinental scales, and that AGCM simulations of the fast response are useful for empirically constraining aerosol forcing.

  14. Normal and friction stabilization techniques for interactive rigid body constraint-based contact force computations

    DEFF Research Database (Denmark)

    Silcowitz-Hansen, Morten; Abel, Sarah Maria Niebe; Erleben, Kenny

    2010-01-01

    We present a novel, yet simple, method for stabilization of normal forces. A normal stabilization term, carefully designed from hypotheses about interactive usability, is added to the contact force problem. Further, we propose friction stabilization as a completely new stabilization paradigm in i...

  15. The Use of Force Notation to Detect Students' Misconceptions: Mutual Interactions Case

    Science.gov (United States)

    Serhane, Ahcene; Zeghdaoui, Abdelhamid; Debiache, Mehdi

    2017-01-01

    Using a conventional notation for representing forces on diagrams, students were presented with questions on the interaction between two objects. The results show that complete understanding of Newton's Third Law of Motion is quite rare, and that some problems relate to misunderstanding which force acts on each body. The use of the terms…

  16. System for measurement of interaction forces between wheel and rail for railway vehicles

    Directory of Open Access Journals (Sweden)

    Manea Ion

    2017-01-01

    Full Text Available Determination of the interaction forces between wheel and rail of railway vehicles is essential for assessment of the vehicle dynamic characteristics from point of view of running safety and rail loading as well as for approval the vehicle and alignment them to the Technical Specification for Interoperability. The direct measurement of transverse and vertical interaction forces using the existing full-disk wheel is practical impossible due to the impossibility of separating the two types of forces. To avoid this impediment it was realized a measuring wheelset fitted with 12 spokes achieved as force transducers for measurement of the vertical forces and 12 spokes achieved as force transducers for measurement of the transverse forces. The measuring wheelset was calibrated as a force transducer and was used to determine the wheel and rail interaction forces for LE-MA 6000kW electric locomotive made by Softronic Craiova. The article presents the measuring wheelset, the calibration principle and the calibration characteristics as well as some time history of the main parameters which characterize the running safety and rail loading, determined in the on-track tests.

  17. Evaluation of Chemical Interactions between Small Molecules in the Gas Phase Using Chemical Force Microscopy.

    Science.gov (United States)

    Lee, Jieun; Ju, Soomi; Kim, In Tae; Jung, Sun-Hwa; Min, Sun-Joon; Kim, Chulki; Sim, Sang Jun; Kim, Sang Kyung

    2015-12-04

    Chemical force microscopy analyzes the interactions between various chemical/biochemical moieties in situ. In this work we examined force-distance curves and lateral force to measure the interaction between modified AFM tips and differently functionalized molecular monolayers. Especially for the measurements in gas phase, we investigated the effect of humidity on the analysis of force-distance curves and the images in lateral force mode. Flat chemical patterns composed of different functional groups were made through micro-contact printing and lateral force mode provided more resolved analysis of the chemical patterns. From the images of 1-octadecanethiol/11-mercapto-1-undecanoic acid patterns, the amine group functionalized tip brought out higher contrast of the patterns than an intact silicon nitride tip owing to the additional chemical interaction between carboxyl and amine groups. For more complex chemical interactions, relative chemical affinities toward specific peptides were assessed on the pattern of 1-octadecanethiol/phenyl-terminated alkanethiol. The lateral image of chemical force microscopy reflected specific preference of a peptide to phenyl group as well as the hydrophobic interaction.

  18. MODELING THE INTERACTION OF AGROCHEMICALS WITH ENVIRONMENTAL SURFACES

    Science.gov (United States)

    The interactions between agrochemicals and organo-mineral surfaces were studied using molecular mechanical conformational calculations and molecular dynamics simulations. Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), 2,4-D (1, 2-dichlorophenoxyacetic acid), and DD...

  19. Streamer-Surface Interaction in Heptane with Micro-Gaps

    International Nuclear Information System (INIS)

    Hamdan, A.; Noel, C.; Henrion, G.; Belmonte, Th.

    2011-01-01

    Interaction between streamer and 316L Stainless Steel substrate in heptane with micro-gaps gives craters with a very specific shape. The role of the Marangoni forces is stressed, a phenomenon which is generally neglected in EDM processes to describe the shape of the craters.

  20. Force mapping on a partially H-covered Si(111)-(7x7) surface: Influence of tip and surface reactivity

    Czech Academy of Sciences Publication Activity Database

    Yurtsever, A.; Sugimoto, Y.; Tanaka, H.; Abe, M.; Morita, S.; Ondráček, Martin; Pou, P.; Pérez, R.; Jelínek, Pavel

    2013-01-01

    Roč. 87, č. 15 (2013), "155403-1"-"155403-10" ISSN 1098-0121 R&D Projects: GA ČR(CZ) GPP204/11/P578; GA ČR GAP204/10/0952; GA AV ČR IAA100100905 Grant - others:GA AV ČR(CZ) M100101207 Institutional support: RVO:68378271 Keywords : atomic force microscopy * DFT simulations * silicon surface * surface passivation * electrostatic interaction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.664, year: 2013 http://link. aps .org/doi/10.1103/PhysRevB.87.155403

  1. Plasma–Surface Interactions Under High Heat and Particle Fluxes

    Directory of Open Access Journals (Sweden)

    Gregory De Temmerman

    2013-01-01

    Full Text Available The plasma-surface interactions expected in the divertor of a future fusion reactor are characterized by extreme heat and particle fluxes interacting with the plasma-facing surfaces. Powerful linear plasma generators are used to reproduce the expected plasma conditions and allow plasma-surface interactions studies under those very harsh conditions. While the ion energies on the divertor surfaces of a fusion device are comparable to those used in various plasma-assited deposition and etching techniques, the ion (and energy fluxes are up to four orders of magnitude higher. This large upscale in particle flux maintains the surface under highly non-equilibrium conditions and bring new effects to light, some of which will be described in this paper.

  2. Understanding small biomolecule-biomaterial interactions: a review of fundamental theoretical and experimental approaches for biomolecule interactions with inorganic surfaces.

    Science.gov (United States)

    Costa, Dominique; Garrain, Pierre-Alain; Baaden, Marc

    2013-04-01

    Interactions between biomolecules and inorganic surfaces play an important role in natural environments and in industry, including a wide variety of conditions: marine environment, ship hulls (fouling), water treatment, heat exchange, membrane separation, soils, mineral particles at the earth's surface, hospitals (hygiene), art and buildings (degradation and biocorrosion), paper industry (fouling) and more. To better control the first steps leading to adsorption of a biomolecule on an inorganic surface, it is mandatory to understand the adsorption mechanisms of biomolecules of several sizes at the atomic scale, that is, the nature of the chemical interaction between the biomolecule and the surface and the resulting biomolecule conformations once adsorbed at the surface. This remains a challenging and unsolved problem. Here, we review the state of art in experimental and theoretical approaches. We focus on metallic biomaterial surfaces such as TiO(2) and stainless steel, mentioning some remarkable results on hydroxyapatite. Experimental techniques include atomic force microscopy, surface plasmon resonance, quartz crystal microbalance, X-ray photoelectron spectroscopy, fluorescence microscopy, polarization modulation infrared reflection absorption spectroscopy, sum frequency generation and time of flight secondary ion mass spectroscopy. Theoretical models range from detailed quantum mechanical representations to classical forcefield-based approaches. Copyright © 2012 Wiley Periodicals, Inc.

  3. Linear response theory of activated surface diffusion with interacting adsorbates

    Energy Technology Data Exchange (ETDEWEB)

    Marti' nez-Casado, R. [Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ (United Kingdom); Sanz, A.S.; Vega, J.L. [Instituto de Fi' sica Fundamental, Consejo Superior de Investigaciones Cientificas, Serrano 123, 28006 Madrid (Spain); Rojas-Lorenzo, G. [Instituto Superior de Tecnologi' as y Ciencias Aplicadas, Ave. Salvador Allende, esq. Luaces, 10400 La Habana (Cuba); Instituto de Fi' sica Fundamental, Consejo Superior de Investigaciones Cienti' ficas, Serrano 123, 28006 Madrid (Spain); Miret-Artes, S., E-mail: s.miret@imaff.cfmac.csic.es [Instituto de Fi' sica Fundamental, Consejo Superior de Investigaciones Cienti' ficas, Serrano 123, 28006 Madrid (Spain)

    2010-05-12

    Graphical abstract: Activated surface diffusion with interacting adsorbates is analyzed within the Linear Response Theory framework. The so-called interacting single adsorbate model is justified by means of a two-bath model, where one harmonic bath takes into account the interaction with the surface phonons, while the other one describes the surface coverage, this leading to defining a collisional friction. Here, the corresponding theory is applied to simple systems, such as diffusion on flat surfaces and the frustrated translational motion in a harmonic potential. Classical and quantum closed formulas are obtained. Furthermore, a more realistic problem, such as atomic Na diffusion on the corrugated Cu(0 0 1) surface, is presented and discussed within the classical context as well as within the framework of Kramer's theory. Quantum corrections to the classical results are also analyzed and discussed. - Abstract: Activated surface diffusion with interacting adsorbates is analyzed within the Linear Response Theory framework. The so-called interacting single adsorbate model is justified by means of a two-bath model, where one harmonic bath takes into account the interaction with the surface phonons, while the other one describes the surface coverage, this leading to defining a collisional friction. Here, the corresponding theory is applied to simple systems, such as diffusion on flat surfaces and the frustrated translational motion in a harmonic potential. Classical and quantum closed formulas are obtained. Furthermore, a more realistic problem, such as atomic Na diffusion on the corrugated Cu(0 0 1) surface, is presented and discussed within the classical context as well as within the framework of Kramer's theory. Quantum corrections to the classical results are also analyzed and discussed.

  4. The interaction of water and hydrogen with nickel surfaces

    NARCIS (Netherlands)

    Shan, Junjun

    2009-01-01

    As nickel and platinum are in the same group of the periodic table, the Ni(111) and Pt(111) surfaces may be expected to show similar interaction with water and hydrogen. However in this thesis, we show these interactions for Ni(111) are quite different from those of Pt(111). Moreover, our results

  5. Surface roughness and cutting force estimation in the CNC turning using artificial neural networks

    Directory of Open Access Journals (Sweden)

    Mohammad Ramezani

    2015-04-01

    Full Text Available Surface roughness and cutting forces are considered as important factors to determine machinability rate and the quality of product. A number of factors like cutting speed, feed rate, depth of cutting and tool noise radius influence the surface roughness and cutting forces in turning process. In this paper, an Artificial Neural Network (ANN model was used to forecast surface roughness and cutting forces with related inputs, including cutting speed, feed rate, depth of cut and tool noise radius. The machined surface roughness and cutting force parameters related to input parameters are the outputs of the ANN model. In this work, 24 samples of experimental data were used to train the network. Moreover, eight other experimental tests were implemented to test the network. The study concludes that ANN was a reliable and accurate method for predicting machining parameters in CNC turning operation.

  6. Electric double layer interactions in bacterial adhesion to surfaces

    NARCIS (Netherlands)

    Poortinga, AT; Norde, W; Busscher, HJ; Bos, R.R.M.

    2002-01-01

    The DLVO (Derjaguin, Landau, Verwey, Overbeek) theory was originally developed to describe interactions between non-biological lyophobic colloids such as polystyrene particles, but is also used to describe bacterial adhesion to surfaces. Despite the differences between the surface of bacteria and

  7. Continuous surface force based lattice Boltzmann equation method for simulating thermocapillary flow

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Lin, E-mail: lz@njust.edu.cn [School of Energy and Power Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Zheng, Song [School of Mathematics and Statistics, Zhejiang University of Finance and Economics, Hangzhou 310018 (China); Zhai, Qinglan [School of Economics Management and Law, Chaohu University, Chaohu 238000 (China)

    2016-02-05

    In this paper, we extend a lattice Boltzmann equation (LBE) with continuous surface force (CSF) to simulate thermocapillary flows. The model is designed on our previous CSF LBE for athermal two phase flow, in which the interfacial tension forces and the Marangoni stresses as the results of the interface interactions between different phases are described by a conception of CSF. In this model, the sharp interfaces between different phases are separated by a narrow transition layers, and the kinetics and morphology evolution of phase separation would be characterized by an order parameter via Cahn–Hilliard equation which is solved in the frame work of LBE. The scalar convection–diffusion equation for temperature field is resolved by thermal LBE. The models are validated by thermal two layered Poiseuille flow, and two superimposed planar fluids at negligibly small Reynolds and Marangoni numbers for the thermocapillary driven convection, which have analytical solutions for the velocity and temperature. Then thermocapillary migration of two/three dimensional deformable droplet are simulated. Numerical results show that the predictions of present LBE agreed with the analytical solution/other numerical results. - Highlights: • A CSF LBE to thermocapillary flows. • Thermal layered Poiseuille flows. • Thermocapillary migration.

  8. Continuous surface force based lattice Boltzmann equation method for simulating thermocapillary flow

    International Nuclear Information System (INIS)

    Zheng, Lin; Zheng, Song; Zhai, Qinglan

    2016-01-01

    In this paper, we extend a lattice Boltzmann equation (LBE) with continuous surface force (CSF) to simulate thermocapillary flows. The model is designed on our previous CSF LBE for athermal two phase flow, in which the interfacial tension forces and the Marangoni stresses as the results of the interface interactions between different phases are described by a conception of CSF. In this model, the sharp interfaces between different phases are separated by a narrow transition layers, and the kinetics and morphology evolution of phase separation would be characterized by an order parameter via Cahn–Hilliard equation which is solved in the frame work of LBE. The scalar convection–diffusion equation for temperature field is resolved by thermal LBE. The models are validated by thermal two layered Poiseuille flow, and two superimposed planar fluids at negligibly small Reynolds and Marangoni numbers for the thermocapillary driven convection, which have analytical solutions for the velocity and temperature. Then thermocapillary migration of two/three dimensional deformable droplet are simulated. Numerical results show that the predictions of present LBE agreed with the analytical solution/other numerical results. - Highlights: • A CSF LBE to thermocapillary flows. • Thermal layered Poiseuille flows. • Thermocapillary migration.

  9. Surface polarity of beta-HMX crystal and the related adhesive forces with Estane binder.

    Science.gov (United States)

    Yang, Lu

    2008-12-02

    Here I present the results on the study of surface properties of beta-HMX crystal utilizing molecular dynamics simulations. The surface polarity of three principal crystal surfaces, (011), (010), and (110), is investigated by measuring the water contact angles. The calculated contact angles are in excellent agreement with the values measured by experiment and show that the surface polarity of three crystal surfaces are different. The free energies and forces of detaching an Estane chain (with and without surrounding nitroplasticizer molecules) from the three principal crystal surfaces are also calculated using the umbrella sampling method. I find that the force for Estane detachment increases with the increasing HMX surface polarity. In addition, my results show that the nitroplasticizer also plays an important role in the adhesion between Estane and HMX surfaces.

  10. Force

    CERN Document Server

    Graybill, George

    2007-01-01

    Forces are at work all around us. Discover what a force is, and different kinds of forces that work on contact and at a distance. We use simple language and vocabulary to make this invisible world easy for students to ""see"" and understand. Examine how forces ""add up"" to create the total force on an object, and reinforce concepts and extend learning with sample problems.

  11. Experimental Investigation of the Wake-Mediated Interaction Forces Between Dust Particles in a Flowing Plasma

    Science.gov (United States)

    Petrov, Oleg; Lisin, Evgeny; Statsenko, Konstantin; Hyde, Truell; Carmona, Jorge

    2015-11-01

    An anisotropic spatial dependence of the wake-mediated interaction forces between dust particles in a plasma flow was studied experimentally. The measurements were performed at CASPER for the vertically aligned chain self-organized from 11 microparticles inside a glass box placed on the lower electrode of a RF gas discharge chamber. The experiment was conducted in argon plasma at 137 mTorr and monodisperse MF particles having diameters of 8.93 microns were used. To recover the wake-mediated interaction forces we improved the method based on solving the inverse Langevin problem of the dynamics of many interacting particles. To determine 3D trajectories of the particles we used a stereoscopic video surveillance system. Spatial profiles of the forces with which upstream particles act on downstream ones and vice versa were obtained. The difference between the interparticle interaction forces in the opposite directions indicates its non-reciprocal nature and can be associated with the wake. The peak position of the wake-field and the space charge concentrated in it were evaluated by the force profile analysis. The data analysis and interaction force recovering in this work was supported by the Russian Science Foundation (O.F. Petrov, K.B. Stacenko, E.?.Lisin) through Grant No. 14-12-01440).

  12. Students' Understanding on Newton's Third Law in Identifying the Reaction Force in Gravity Interactions

    Science.gov (United States)

    Zhou, Shaona; Zhang, Chunbin; Xiao, Hua

    2015-01-01

    In the past three decades, previous researches showed that students had various misconceptions of Newton's Third Law. The present study focused on students' difficulties in identifying the third-law force pair in gravity interaction situations. An instrument involving contexts with gravity and non-gravity associated interactions was designed and…

  13. Electronegativity determination of individual surface atoms by atomic force microscopy

    Czech Academy of Sciences Publication Activity Database

    Onoda, J.; Ondráček, Martin; Jelínek, Pavel; Sugimoto, Y.

    2017-01-01

    Roč. 8, Apr (2017), 1-6, č. článku 15155. ISSN 2041-1723 R&D Projects: GA ČR(CZ) GC14-16963J Institutional support: RVO:68378271 Keywords : AFM * DFT * electronegativity * surface science Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 12.124, year: 2016

  14. ENSO surface longwave radiation forcing over the tropical Pacific

    Directory of Open Access Journals (Sweden)

    K. G. Pavlakis

    2007-01-01

    Full Text Available We have studied the spatial and temporal variation of the surface longwave radiation (downwelling and net over a 21-year period in the tropical and subtropical Pacific Ocean (40 S–40 N, 90 E–75 W. The fluxes were computed using a deterministic model for atmospheric radiation transfer, along with satellite data from the ISCCP-D2 database and reanalysis data from NCEP/NCAR (acronyms explained in main text, for the key atmospheric and surface input parameters. An excellent correlation was found between the downwelling longwave radiation (DLR anomaly and the Niño-3.4 index time-series, over the Niño-3.4 region located in the central Pacific. A high anti-correlation was also found over the western Pacific (15–0 S, 105–130 E. There is convincing evidence that the time series of the mean downwelling longwave radiation anomaly in the western Pacific precedes that in the Niño-3.4 region by 3–4 months. Thus, the downwelling longwave radiation anomaly is a complementary index to the SST anomaly for the study of ENSO events and can be used to asses whether or not El Niño or La Niña conditions prevail. Over the Niño-3.4 region, the mean DLR anomaly values range from +20 Wm−2 during El Niño episodes to −20 Wm−2 during La Niña events, while over the western Pacific (15–0 S, 105–130 E these values range from −15 Wm−2 to +10 Wm−2, respectively. The long- term average (1984–2004 distribution of the net downwelling longwave radiation at the surface over the tropical and subtropical Pacific for the three month period November-December-January shows a net thermal cooling of the ocean surface. When El Niño conditions prevail, the thermal radiative cooling in the central and south-eastern tropical Pacific becomes weaker by 10 Wm−2 south of the equator in the central Pacific (7–0 S, 160–120 W for the three-month period of NDJ, because the DLR increase is larger than the increase in surface thermal emission. In contrast, the

  15. Interactions of planetary magnetospheres with icy satellite surfaces

    International Nuclear Information System (INIS)

    Cheng, A.F.; Haff, P.K.; Johnson, R.E.; Lanzerotti, L.J.

    1986-01-01

    When natural satellites and ring particles are embedded within magnetospheric plasmas, the charged particles interact with the surfaces of these solid bodies. These interactions have important implications for the surface, the atmosphere of the parent body, and the magnetosphere as a whole. Significant erosion of the surface by sputtering, as well as redeposition of sputter ejecta, can occur over geologic time. The surface can also be chemically modified. Sputter ejecta can make important contributions to the atmosphere; sputtering provides a lower limit to the atmospheric column density even for arbitrarily cold satellite surfaces. Sputter ejecta escaping from the parent body can form extensive neutral clouds within the magnetosphere. Ionization and dissociation within these neutral clouds can be dominant sources of low-energy plasma. The importance of these processes is discussed for the satellites and magnetospheres of Jupiter, Saturn and Uranus

  16. Automated boundary interaction force control of micromanipulators with in situ applications to microsurgery

    International Nuclear Information System (INIS)

    Eslami, Sohrab; Jalili, Nader

    2012-01-01

    Most recent works on miniature tasks are concentrated on developing tools to take advantage of the visual servoing feedback to control the ultra-small interaction forces. This paper spans an extensive platform for automatic controlling of boundary interaction forces with high precision in the level of micro/nano-Newton with extensive micro/nanoengineering applications such as the microsurgery. To this end, a comprehensive piezoresistive microcantilever (PMC) model considering the shear deformation and rotary inertia effects treating as the distributed-parameters model along with the Hertzian contact force is presented. The purpose of considering the Hertzian contact force model is to investigate the dynamic response of the interaction force between the microcantilever's tip and the specimen. Afterward, a control platform is introduced to automatically manipulate the PMC to follow an ideal micro/nano-interaction force. By using the integrated PMC with the micromanipulator and a digital signal processor, an intuitive programming code is written to incorporate the micromanipulator and the controller in a real-time framework. To calibrate and verify the induced voltage in the PMC, a self-sensing experiment on the piezoelectric microcantilever is carried out to warrant the calibration procedure. Some experiments are established to affirm the validity of the proposed control for the autonomous real-time tasks on the boundary interaction force control. Unlike the conventional research studies, the measured force here contributes as the feedback source in contrast to the vision feedback while force sensors possess more precision, productivity and small size. This technique has several potential applications listed but not limited to the micro/nanomanipulation, developing artificial biological systems (e.g., fabricating hydrogel for the scaffold), and medicine such as microsurgery. As a result, using the proposed platform, we are able to manipulate and control the

  17. Tracking Traction Force Changes of Single Cells on the Liquid Crystal Surface

    Directory of Open Access Journals (Sweden)

    Chin Fhong Soon

    2015-01-01

    Full Text Available Cell migration is a key contributor to wound repair. This study presents findings indicating that the liquid crystal based cell traction force transducer (LCTFT system can be used in conjunction with a bespoke cell traction force mapping (CTFM software to monitor cell/surface traction forces from quiescent state in real time. In this study, time-lapse photo microscopy allowed cell induced deformations in liquid crystal coated substrates to be monitored and analyzed. The results indicated that the system could be used to monitor the generation of cell/surface forces in an initially quiescent cell, as it migrated over the culture substrate, via multiple points of contact between the cell and the surface. Future application of this system is the real-time assaying of the pharmacological effects of cytokines on the mechanics of cell migration.

  18. Systematic study of the dolomite (104) surface by bimodal dynamic force microscopy in ultra-high vacuum.

    Science.gov (United States)

    Kawai, Shigeki; Pina, Carlos M; Bubendorf, Alexander; Fessler, Gregor; Glatzel, Thilo; Gnecco, Enrico; Meyer, Ernst

    2013-02-08

    We have investigated the morphology and structure of dolomite MgCa(CO(3))(2)(104) surfaces by bimodal dynamic force microscopy with flexural and torsional resonance modes in ultra-high vacuum at room temperature. We found that the surface slowly decomposes by degassing CO(2) in a vacuum and becomes covered by amorphous clusters, presumably MgO and CaO. By choosing an optimal sample preparation procedure (i.e. cleaving in a vacuum and mild annealing for stabilizing clusters for a short time), atomically clean surfaces were obtained. The complex tip-sample interaction, arising from carbonate groups and Mg and Ca atoms of the surface, induces a large variety of atomic-scale imaging features.

  19. Vibrational Analysis of Brucite Surfaces and the Development of an Improved Force Field for Molecular Simulation of Interfaces.

    Science.gov (United States)

    Zeitler, Todd R; Greathouse, Jeffery A; Gale, Julian D; Cygan, Randall T

    2014-04-17

    We introduce a nonbonded three-body harmonic potential energy term for Mg-O-H interactions for improved edge surface stability in molecular simulations. The new potential term is compatible with the Clayff force field and is applied here to brucite, a layered magnesium hydroxide mineral. Comparisons of normal mode frequencies from classical and density functional theory calculations are used to verify a suitable spring constant ( k parameter) for the Mg-O-H bending motion. Vibrational analysis of hydroxyl librations at two brucite surfaces indicates that surface Mg-O-H modes are shifted to frequencies lower than the corresponding bulk modes. A comparison of DFT and classical normal modes validates this new potential term. The methodology for parameter development can be applied to other clay mineral components (e.g., Al, Si) to improve the modeling of edge surface stability, resulting in expanded applicability to clay mineral applications.

  20. Exploiting impedance shaping approaches to overcome force overshoots in delicate interaction tasks

    Directory of Open Access Journals (Sweden)

    Loris Roveda

    2016-09-01

    Full Text Available The aim of the presented article is to overcome the force overshoot issue in impedance based force tracking applications. Nowadays, light-weight manipulators are involved in high-accurate force control applications (such as polishing tasks, where the force overshoot issue is critical (i.e. damaging the component causing a production waste, exploiting the impedance control. Two main force tracking impedance control approaches are described in literature: (a set-point deformation and (b variable stiffness approaches. However, no contributions are directly related to the force overshoot issue. The presented article extends both such methodologies to analytically achieve the force overshoots avoidance in interaction tasks based on the on-line estimation of the interacting environment stiffness (available through an EKF. Both the proposed control algorithms allow to achieve a linear closed-loop dynamics for the coupled robot-environment system. Therefore, control gains can be analytically on-line calculated to achieve an over-damped closed-loop dynamics of the controlled coupled system. Control strategies have been validated in experiments, involving a KUKA LWR 4+. A probing task has been performed, representative of many industrial tasks (e.g. assembly tasks, in which a main force task direction is defined.

  1. A review on data and predictions of water dielectric spectra for calculations of van der Waals surface forces.

    Science.gov (United States)

    Wang, Jianlong; Nguyen, Anh V

    2017-12-01

    Van der Waals forces are one of the important components of intermolecular, colloidal and surface forces governing many phenomena and processes. The latest examples include the colloidal interactions between hydrophobic colloids and interfaces in ambient (non-degassed) water in which dissolved gases and nanobubbles are shown to affect the van der Waals attractions significantly. The advanced computation of van der Waals forces in aqueous systems by the Lifshitz theory requires reliable data for water dielectric spectra. In this paper we review the available predictions of water dielectric spectra for calculating colloidal and surface van der Waals forces. Specifically, the available experimental data for the real and imaginary parts of the complex dielectric function of liquid water in the microwave, IR and UV regions and various corresponding predictions of the water spectra are critically reviewed. The data in the UV region are critical, but the available predictions are still based on the outdated data obtained in 1974 (for frequency only up to 25.5eV). We also reviewed and analysed the experimental data obtained for the UV region in 2000 (for frequency up to 50eV) and 2015 (for frequency up to 100eV). The 1974 and 2000 data require extrapolations to higher frequencies needed for calculating the van der Waals forces but remain inaccurate. Our analysis shows that the latest data of 2015 do not require the extrapolation and can be used to reliably calculate van der Waals forces. The most recent water dielectric spectra gives the (non-retarded) Hamaker constant, A=5.20×10 -20 J, for foam films of liquid water. This review provides the most updated and reliable water dielectric spectra to compute van der Waals forces in aqueous systems. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Influence of surface roughness on streptococcal adhesion forces to composite resins

    NARCIS (Netherlands)

    Mei, Li; Busscher, Henk J; van der Mei, Henny C; Ren, Yijin

    OBJECTIVE: To determine streptococcal adhesion forces with composite resins with different surface roughness. METHODS: Polishing and grinding were applied to obtain smooth (roughness 20 nm), moderately rough (150 nm) and rough (350 nm) surfaces of two orthodontic, light-cured composites. Adhesion

  3. Surface thermodynamics and adhesion forces governing bacterial transmission in contact lens related microbial keratitis

    NARCIS (Netherlands)

    Qu, Wenwen; Busscher, Henk J.; Hooymans, Johanna M. M.; van der Mei, Henny C.

    2011-01-01

    Contact lens induced microbial keratitis results from bacterial transmission from one surface to another. We investigated the adhesion forces of Pseudomonas aeruginosa, Staphylococci and Serratia to different contact lenses, lens cases and corneal surfaces using AFM, and applied a Weibull analysis

  4. Resistive-force theory for mesh-like superhydrophobic surfaces

    Science.gov (United States)

    Schnitzer, Ory; Yariv, Ehud

    2018-03-01

    A common realization of superhydrophobic surfaces makes use of a mesh-like geometry, where pockets of air are trapped in a periodic array of holes in a no-slip solid substrate. We consider the small-solid-fraction limit where the ribs of the mesh are narrow. In this limit, we obtain a simple leading-order approximation for the slip-length tensor of an arbitrary mesh geometry. This approximation scales as the solid-fraction logarithm, as anticipated by Ybert et al. [Phys. Fluids 19, 123601 (2007), 10.1063/1.2815730]; in the special case of a square mesh it agrees with the analytical results obtained by Davis and Lauga [Phys. Fluids 21, 113101 (2009), 10.1063/1.3250947].

  5. Pycortex: an interactive surface visualizer for fMRI

    Directory of Open Access Journals (Sweden)

    James Shuang Gao

    2015-09-01

    Full Text Available Surface visualizations of fMRI provide a comprehensive view of cortical activity. However, surface visualizations are difficult to generate and most common visualization techniques rely on unnecessary interpolation which limits the fidelity of the resulting maps. Furthermore, it is difficult to understand the relationship between flattened cortical surfaces and the underlying 3D anatomy using tools available currently. To address these problems we have developed pycortex, a Python toolbox for interactive surface mapping and visualization. Pycortex exploits the power of modern graphics cards to sample volumetric data on a per-pixel basis, allowing dense and accurate mapping of the voxel grid across the surface. Anatomical, functional and fiduciary information can be projected onto the cortical surface. The surface can be inflated and flattened interactively, aiding interpretation of the correspondence between the anatomical surface and the flattened cortical sheet. The output of pycortex can be viewed using WebGL, a technology compatible with modern web browsers. This allows complex fMRI surface maps to be distributed broadly online without requiring installation of complex software.

  6. Structures of multidomain proteins adsorbed on hydrophobic interaction chromatography surfaces.

    Science.gov (United States)

    Gospodarek, Adrian M; Sun, Weitong; O'Connell, John P; Fernandez, Erik J

    2014-12-05

    In hydrophobic interaction chromatography (HIC), interactions between buried hydrophobic residues and HIC surfaces can cause conformational changes that interfere with separations and cause yield losses. This paper extends our previous investigations of protein unfolding in HIC chromatography by identifying protein structures on HIC surfaces under denaturing conditions and relating them to solution behavior. The thermal unfolding of three model multidomain proteins on three HIC surfaces of differing hydrophobicities was investigated with hydrogen exchange mass spectrometry (HXMS). The data were analyzed to obtain unfolding rates and Gibbs free energies for unfolding of adsorbed proteins. The melting temperatures of the proteins were lowered, but by different amounts, on the different surfaces. In addition, the structures of the proteins on the chromatographic surfaces were similar to the partially unfolded structures produced in the absence of a surface by temperature as well as by chemical denaturants. Finally, it was found that patterns of residue exposure to solvent on different surfaces at different temperatures can be largely superimposed. These findings suggest that protein unfolding on various HIC surfaces might be quantitatively related to protein unfolding in solution and that details of surface unfolding behavior might be generalized. Copyright © 2014 Elsevier B.V. All rights reserved.

  7. Direct Measurements of Surface Energy, Elastic Modulus and Interparticle Forces of Titan Aerosol Analog (`Tholin') Using Atomic Force Microscopy

    Science.gov (United States)

    Yu, X.; Horst, S. M.; He, C.; McGuiggan, P.; Bridges, N. T.

    2017-12-01

    To understand the origin of the dunes on Titan, it is important to investigate the material properties of the sand particles on Titan, which are mainly made of organics deposited from the atmosphere [1]. The organic sand may behave differently compared to the quartz/basaltic sand on terrestrial planets (Earth, Venus, Mars) in terms of interparticle forces. We measured the surface energy (through contact angle measurements) and elastic modulus (through Atomic Force Microscopy, AFM) of Titan aerosol analog (tholins) produced in our lab. Tholins may be compositionally similar to sand on Titan. We directly measured the interparticle forces between a tholin particle adhered to an AFM cantilver and tholin particles on a substrate. We also measured the properties of walnut shells, a typical material used in the Titan Wind Tunnel (TWT, [2, 3]). We find the surface energy of a tholin thin film is about 70.9 mN/m and its elastic modulus is about 3.5 GPa (similar to hard polymers like PMMA and polystyrene). We used the two measured material properties of tholin to calculate its interparticle cohesion assuming simple sphere-sphere geometry [4]. For two 20 µm particles, the theoretical cohesion force is about 6682 nN. Under dry nitrogen (RHmeasured interparticle forces using AFM was approximately 4000 nN, which is smaller than theoretical predictions but still relatively strong under dry conditions. The interparticle cohesion between walnut shell particles is only 200 nN, which is much lower than between tholin particles. The key finding of this study is that the interparticle cohesion forces are much larger for tholins and presumably Titan sand particles than for terrestrial sand and materials used in the wind tunnel. This suggests we should increase the interparticle force in both analog experiments (TWT) and threshold models (e.g. [5]) to correctly translate the results to real Titan conditions. The strong cohesion of tholins may also inform us how the small aerosol

  8. Comparisons of the Maxwell and CLL gas/surface interaction models using DSMC

    Science.gov (United States)

    Hedahl, Marc O.; Wilmoth, Richard G.

    1995-12-01

    The behavior of two different models of gas-surface interactions is studied using the Direct Simulation Monte Carlo (DSMC) method. The DSMC calculations examine differences in predictions of aerodynamic forces and heat transfer between the Maxwell and the Cercignani-Lampis-Lord (CLL) models for flat plate configurations at freestream conditions corresponding to a 140 km orbit around Venus. The size of the flat plate represents one of the solar panels on the Magellan spacecraft, and the freestream conditions correspond to those experienced during aerobraking maneuvers. Results are presented for both a single flat plate and a two-plate configuration as a function of angle of attack and gas-surface accommodation coefficients. The two-plate system is not representative of the Magellan geometry but is studied to explore possible experiments that might be used to differentiate between the two gas-surface interaction models. The Maxwell and CLL models produce qualitatively similar results for the aerodynamic forces and heat transfer on a single flat plate. However, the flow fields produced with the two models are qualitatively different for both the single-plate and two-plate calculations. These differences in the flowfield lead to predictions of the angle of attack for maximum heat transfer in a two plate configuration that are distinctly different for the two gas-surface interactions models.

  9. Superhydrophobic Zr-based metallic glass surface with high adhesive force

    Science.gov (United States)

    Li, Ning; Xia, Ting; Heng, Liping; Liu, Lin

    2013-06-01

    Micro/nano hierarchical structures were constructed on Zr35Ti30Be26.75Cu8.25 metallic glass surface by silicon moulding and subsequently chemical etching. The as-formed surface exhibited both superhydrophobicity and high adhesive force towards water. The superhydrophobicity is rationalized based on the modified Cassie-Baxter model [A. B. D. Cassie and S. Baxter, Trans. Faraday Soc. 40, 546 (1944)]. The origin of the robust adhesion is described in terms of intermolecular capillary forces. The present results not only provide a method to fabricate superhydrophobic metallic glasses surface but also explore an important industrial application as dry adhesives and transport of liquid microdroplets.

  10. Continuous versus Arrested Spreading of Biofilms at Solid-Gas Interfaces: The Role of Surface Forces

    Science.gov (United States)

    Trinschek, Sarah; John, Karin; Lecuyer, Sigolène; Thiele, Uwe

    2017-08-01

    We introduce and analyze a model for osmotically spreading bacterial colonies at solid-air interfaces that includes wetting phenomena, i.e., surface forces. The model is based on a hydrodynamic description for liquid suspensions which is supplemented by bioactive processes. We show that surface forces determine whether a biofilm can expand laterally over a substrate and provide experimental evidence for the existence of a transition between continuous and arrested spreading for Bacillus subtilis biofilms. In the case of arrested spreading, the lateral expansion of the biofilm is confined, albeit the colony is biologically active. However, a small reduction in the surface tension of the biofilm is sufficient to induce spreading. The incorporation of surface forces into our hydrodynamic model allows us to capture this transition in biofilm spreading behavior.

  11. Gauge unification of basic forces, particularly of gravitation with strong interactions

    International Nuclear Information System (INIS)

    Salam, A.

    1977-01-01

    An attempt is made to present a case for the use of both the Einstein--Weyl spin-two and the Yang--Mills spin-one gauge structures for describing strong interactions. By emphasizing both spin-one and -two aspects of this force, it is hoped that a unification of this force, on the one hand, with gravity theory and, on the other, with the electromagnetic and weak interactions can be achieved. A Puppi type of tetrahedral interralation of fundamental forces, with the strong force playing a pivotal role due to its mediation through both spin-one and -two quanta, is proposed. It is claimed that the gauge invariance of gravity theory permits the use of ambuguity-free nonpolynomial techniques and thereby the securing of relistic regularization in gravity-modified field theories with the Newtonian constant G/sub N/ providing a relistic cutoff. 37 references

  12. Investigation of the surface potential of TiO2 (110) by frequency-modulation Kelvin probe force microscopy.

    Science.gov (United States)

    Kou, Lili; Li, Yan Jun; Kamijyo, Takeshi; Naitoh, Yoshitaka; Sugawara, Yasuhiro

    2016-12-16

    We investigate the surface potential distribution on a TiO 2 (110)-1 × 1 surface by Kelvin probe force microscopy (KPFM) and atom-dependent bias-distance spectroscopic mapping. The experimental results demonstrate that the local contact potential difference increases on twofold-coordinated oxygen sites, and decreases on OH defects and fivefold-coordinated Ti sites. We propose a qualitative model to explain the origin of the surface potential of TiO 2 (110). We qualitatively calculate the surface potential induced by chemical potential and permanent surface dipole. The calculated results agree with our experimental ones. Therefore, we suggest that the surface potential of TiO 2 (110) is dominated not only by the permanent surface dipole between the tip apex atom and surface, but also by the dipoles induced by the chemical interaction between the tip and sample. The KPFM technique demonstrate the possibility of investigation of the charge transfer phenomenon on TiO 2 surface under gas conditions. It is useful for the elucidation of the mechanism of the catalytic reactions.

  13. The Character of the Solar Wind, Surface Interactions, and Water

    Science.gov (United States)

    Farrell, William M.

    2011-01-01

    We discuss the key characteristics of the proton-rich solar wind and describe how it may interact with the lunar surface. We suggest that solar wind can be both a source and loss of water/OH related volatiles, and review models showing both possibilities. Energy from the Sun in the form of radiation and solar wind plasma are in constant interaction with the lunar surface. As such, there is a solar-lunar energy connection, where solar energy and matter are continually bombarding the lunar surface, acting at the largest scale to erode the surface at 0.2 Angstroms per year via ion sputtering [1]. Figure 1 illustrates this dynamically Sun-Moon system.

  14. Immobilized enzymes: understanding enzyme - surface interactions at the molecular level.

    Science.gov (United States)

    Hoarau, Marie; Badieyan, Somayesadat; Marsh, E Neil G

    2017-11-22

    Enzymes immobilized on solid supports have important and industrial and medical applications. However, their uses are limited by the significant reductions in activity and stability that often accompany the immobilization process. Here we review recent advances in our understanding of the molecular level interactions between proteins and supporting surfaces that contribute to changes in stability and activity. This understanding has been facilitated by the application of various surface-sensitive spectroscopic techniques that allow the structure and orientation of enzymes at the solid/liquid interface to be probed, often with monolayer sensitivity. An appreciation of the molecular interactions between enzyme and surface support has allowed the surface chemistry and method of enzyme attachement to be fine-tuned such that activity and stability can be greatly enhanced. These advances suggest that a much wider variety of enzymes may eventually be amenable to immobilization as green catalysts.

  15. Electron emission during multicharged ion-metal surface interactions

    International Nuclear Information System (INIS)

    Zeijlmans van Emmichoven, P.A.; Havener, C.C.; Hughes, I.G.; Overbury, S.H.; Robinson, M.T.; Zehner, D.M.; Meyer, F.W.

    1992-01-01

    The electron emission during multicharged ion-metal surface interactions will be discussed. The interactions lead to the emission of a significant number of electrons. Most of these electrons have energies below 30 eV. For incident ions with innershell vacancies the emission of Auger electrons that fill these vacancies has been found to occur mainly below the surface. We will present recently measured electron energy distributions which will be used to discuss the mechanisms that lead to the emission of Auger and of low-energy electrons

  16. Interfacial force measurements using atomic force microscopy

    NARCIS (Netherlands)

    Chu, L.

    2018-01-01

    Atomic Force Microscopy (AFM) can not only image the topography of surfaces at atomic resolution, but can also measure accurately the different interaction forces, like repulsive, adhesive and lateral existing between an AFM tip and the sample surface. Based on AFM, various extended techniques have

  17. Towards a Revised Monte Carlo Neutral Particle Surface Interaction Model

    International Nuclear Information System (INIS)

    Stotler, D.P.

    2005-01-01

    The components of the neutral- and plasma-surface interaction model used in the Monte Carlo neutral transport code DEGAS 2 are reviewed. The idealized surfaces and processes handled by that model are inadequate for accurately simulating neutral transport behavior in present day and future fusion devices. We identify some of the physical processes missing from the model, such as mixed materials and implanted hydrogen, and make some suggestions for improving the model

  18. Significance of force transfer in mitral valve-left ventricular interaction: in vivo assessment.

    Science.gov (United States)

    Askov, Jesper B; Honge, Jesper L; Jensen, Morten O; Nygaard, Hans; Hasenkam, J Michael; Nielsen, Sten L

    2013-06-01

    The objective of this study was to assess the combined force transfer from the papillary muscle tips to the mitral valve through the chordae tendineae in vivo, and thereby quantify the force transmitted through the papillary-chordal complex to augment left ventricular ejection. In an acute porcine model (n = 8), force transfer between papillary muscles and the mitral valve was recorded on the anterior and posterior papillary muscle tip using dedicated force transducers. Ultrasound sonomicrometry was utilized to record and calculate left ventricular long-axis shortening and mitral annular geometry. The closing force acting on the mitral valve leaflets was calculated as mitral annular area multiplied by the transmitral pressure difference throughout systole. Mitral valve competence was verified before measurements with color Doppler ultrasound. Peak force in the anterior and posterior papillary muscle was 5.9 ± 0.6 N and 5.8 ± 0.7 N (mean ± standard error of the mean), respectively, and peak closing force was 6.8 ± 0.3 N all at a transmitral pressure of 90 mm Hg. Peak rate of left ventricular contraction coincided with peak papillary muscle force. This study is the first to assess the magnitude and time course of the longitudinal force transmitted through the papillary-chordal complex to the left ventricular wall during ejection. The study also demonstrates a significant force transfer to the closing force acting on the mitral valve leaflets that constitutes an essential component of valvular-ventricular interaction to enhance left ventricular systolic pump performance. The magnitude of the combined papillary muscle force component emphasizes the crucial role of preserving mitral valve-left ventricular continuity in mitral valve surgery. Copyright © 2013 The American Association for Thoracic Surgery. Published by Mosby, Inc. All rights reserved.

  19. Investigating the adsorption of the gemini surfactant "12-2-12" onto mica using atomic force microscopy and surface force apparatus measurements

    NARCIS (Netherlands)

    Fielden, ML; Claesson, PM; Verrall, RE

    1999-01-01

    The adsorption of the cationic gemini surfactant 1,2-bis(n-dodecyldimethylammonium)ethane dibromide on mica was followed by measuring forces between mica surfaces and by atomic force microscopy (AFM) imaging. The surface charge was found to be neutralized at total surfactant concentrations between 8

  20. Force/position control of a robot manipulator for human-robot interaction

    Directory of Open Access Journals (Sweden)

    Neranon Paramin

    2016-01-01

    Full Text Available With regard to both human and robot capabilities, human-robot interaction provides several benefits, and this will be significantly developed and implemented. This work focuses on the development of real-time external force/position control used for human-robot interaction. The force-controlled robotic system integrated with proportional integral control was performed and evaluated to ensure its reliably and timely operational characteristics, in which appropriate proportional integral gains were experimentally adopted using a set of virtual crank-turning tests. The designed robotic system is made up of a robot manipulator arm, an ATI Gamma multi-axis force/torque sensor and a real-time external PC based control system. A proportional integral controller has been developed to provide stable and robust force control on unknown environmental stiffness and motion. To quantify its effectiveness, the robotic system has been verified through a comprehensive set of experiments, in which force measurement and ALTER real-time path control systems were evaluated. In summary, the results indicated satisfactorily stable performance of the robot force/position control system. The gain tuning for proportional plus integral control algorithm was successfully implemented. It can be reported that the best performance as specified by the error root mean square method of the radial force is observed with proportional and integral gains of 0.10 and 0.005 respectively.

  1. An analytical model for force prediction in ball nose micro milling of inclined surfaces

    DEFF Research Database (Denmark)

    Bissacco, Giuliano; Hansen, Hans Nørgaard; De Chiffre, Leonardo

    2010-01-01

    Ball nose micro milling is a key process for the generation of free form surfaces and inclined surfaces often present in mould inserts for micro replication. This paper presents a new cutting force model for ball nose micro milling that is capable of taking into account the effect of the edge rad...... radius and the effect of the surface topography due to the previous milling passes. The model is completely analytical can be applied to ball end micro milling of slanted surfaces for any value of the surface inclination angle relative to the tool axis....

  2. Seismic response of pile foundations and pile forces caused by kinematic and inertial interaction

    International Nuclear Information System (INIS)

    Hartmann, H.G.; Waas, G.

    1985-01-01

    The horizontal motion and pile forces of pile groups subjected to earthquake excitation are analysed. The piles are modelled as linear elastic beam elements embedded in a layered linear visco-elastic soil medium. Pile-soil-pile interaction is included. The earthquake excitation results from vertically propagating shear waves. Kinematic and inertial interaction effects on foundation motion and pile forces are studied for a single pile, a small pile group and a large pile group. Soft and stiff soil conditions are considered, and the effect of a flexible vs. a rigid halfspace below the soil layers is shown. (orig.)

  3. On the Transition from Bulk to Ordered Form of Water: A Theoretical Model to Calculate Adhesion Force Due to Capillary and van der Waals Interaction

    NARCIS (Netherlands)

    Yaqoob, M.A.; de Rooij, Matthias B.; Schipper, Dirk J.

    2013-01-01

    The adhesion force due to capillary interaction between two hydrophilic surfaces is strongly dependent on the partial pressure of water and is often calculated using the Kelvin equation. The validity of the Kelvin equation is questionable at low relative humidity (RH) of water, like in high vacuum

  4. Improved simulation of groundwater - surface water interaction in catchment models

    Science.gov (United States)

    teklesadik, aklilu; van Griensven, Ann; Anibas, Christian; Huysmans, Marijke

    2016-04-01

    Groundwater storage can have a significant contribution to stream flow, therefore a thorough understanding of the groundwater surface water interaction is of prime important when doing catchment modeling. The aim of this study is to improve the simulation of groundwater - surface water interaction in a catchment model of the upper Zenne River basin located in Belgium. To achieve this objective we used the "Groundwater-Surface water Flow" (GSFLOW) modeling software, which is an integration of the surface water modeling tool "Precipitation and Runoff Modeling system" (PRMS) and the groundwater modeling tool MODFLOW. For this case study, the PRMS model and MODFLOW model were built and calibrated independently. The PRMS upper Zenne River basin model is divided into 84 hydrological response units (HRUs) and is calibrated with flow data at the Tubize gauging station. The spatial discretization of the MODFLOW upper Zenne groundwater flow model consists of 100m grids. Natural groundwater divides and the Brussels-Charleroi canal are used as boundary conditions for the MODFLOW model. The model is calibrated using piezometric data. The GSFLOW results were evaluated against a SWAT model application and field observations of groundwater-surface water interactions along a cross section of the Zenne River and riparian zone. The field observations confirm that there is no exchange of groundwater beyond the Brussel-Charleroi canal and that the interaction at the river bed is relatively low. The results show that there is a significant difference in the groundwater simulations when using GSFLOW versus SWAT. This indicates that the groundwater component representation in the SWAT model could be improved and that a more realistic implementation of the interactions between groundwater and surface water is advisable. This could be achieved by integrating SWAT and MODFLOW.

  5. The mechanical interactions between an American football cleat and playing surfaces in-situ at loads and rates generated by elite athletes: a comparison of playing surfaces.

    Science.gov (United States)

    Kent, Richard; Forman, Jason L; Crandall, Jeff; Lessley, David

    2015-03-01

    This study quantified the mechanical interactions between an American football cleat and eight surfaces used by professional American football teams. Loading conditions were applied with a custom-built testing apparatus designed to represent play-relevant maneuvers of elite athletes. Two natural grass and six infill artificial surfaces were tested with the cleated portion of a shoe intended for use on either surface type. In translation tests with a 2. 8-kN vertical load, the grass surfaces limited the horizontal force on the cleats by tearing. This tearing was not observed with the artificial surfaces, which allowed less motion and generated greater horizontal force (3.2 kN vs. 4.5 kN, p force on the natural surfaces than on the artificial surfaces (2.4 kN vs. 3.0 kN, p force-limiting mechanism inherent to natural grass surfaces. Future work should consider implications of these findings for performance and injury risk and should evaluate the findings' sensitivity to cleat pattern and playing conditions.

  6. Dynamic interactions of Leidenfrost droplets on liquid metal surface

    Science.gov (United States)

    Ding, Yujie; Liu, Jing

    2016-09-01

    Leidenfrost dynamic interaction effects of the isopentane droplets on the surface of heated liquid metal were disclosed. Unlike conventional rigid metal, such conductive and deformable liquid metal surface enables the levitating droplets to demonstrate rather abundant and complex dynamics. The Leidenfrost droplets at different diameters present diverse morphologies and behaviors like rotation and oscillation. Depending on the distance between the evaporating droplets, they attract and repulse each other through the curved surfaces beneath them and their vapor flows. With high boiling point up to 2000 °C, liquid metal offers a unique platform for testing the evaporating properties of a wide variety of liquid even solid.

  7. Force field and a surface model database for silica to simulate interfacial properties in atomic resolution

    OpenAIRE

    Emami, FS; Puddu, V; Berry, RJ; Varshney, V; Patwardhan, SV; Perry, CC; Heinz, H

    2014-01-01

    Silica nanostructures find applications in drug delivery, catalysis, and composites, however, understanding of the surface chemistry, aqueous interfaces, and biomolecule recognition remain difficult using current imaging techniques and spectroscopy. A silica force field is introduced that resolves numerous shortcomings of prior silica force fields over the last thirty years and reduces uncertainties in computed interfacial properties relative to experiment from several 100% to less than 5%. I...

  8. Effects of surface design on aerodynamic forces of iced bridge cables

    DEFF Research Database (Denmark)

    Koss, Holger

    2014-01-01

    . The determination of these force coefficients require a proper simulation of the ice layer occurring under the specific climatic conditions, favouring real ice accretion over simplified artificial reproduction. The work presented in this paper was performed to study whether the design of bridge cable surface...... influences the accretion of ice to an extent that the aerodynamic forces differ significantly amongst the designs. The experiments were conducted in a wind tunnel facility capable amongst others to simulate in-cloud icing conditions....

  9. Theoretical Investigation of Hydrogen Adsorption and Dissociation on Iron and Iron Carbide Surfaces Using the ReaxFF Reactive Force Field Method

    Energy Technology Data Exchange (ETDEWEB)

    Zou, Chenyu; van Duin, Adri C.T.; Sorescu, Dan C.

    2012-06-01

    We have developed a ReaxFF reactive force field to describe hydrogen adsorption and dissociation on iron and iron carbide surfaces relevant for simulation of Fischer–Tropsch (FT) synthesis on iron catalysts. This force field enables large system (>>1000 atoms) simulations of hydrogen related reactions with iron. The ReaxFF force field parameters are trained against a substantial amount of structural and energetic data including the equations of state and heats of formation of iron and iron carbide related materials, as well as hydrogen interaction with iron surfaces and different phases of bulk iron. We have validated the accuracy and applicability of ReaxFF force field by carrying out molecular dynamics simulations of hydrogen adsorption, dissociation and recombination on iron and iron carbide surfaces. The barriers and reaction energies for molecular dissociation on these two types of surfaces have been compared and the effect of subsurface carbon on hydrogen interaction with iron surface is evaluated. We found that existence of carbon atoms at subsurface iron sites tends to increase the hydrogen dissociation energy barrier on the surface, and also makes the corresponding hydrogen dissociative state relatively more stable compared to that on bare iron. These properties of iron carbide will affect the dissociation rate of H{sub 2} and will retain more surface hydride species, thus influencing the dynamics of the FT synthesis process.

  10. Influence of Surface Properties on Adhesion Forces and Attachment of Streptococcus mutans to Zirconia In Vitro

    Science.gov (United States)

    Yu, Pei; Wang, Chuanyong; Zhou, Jinglin; Jiang, Li

    2016-01-01

    Zirconia is becoming a prevalent material in dentistry. However, any foreign bodies inserted may provide new niches for the bacteria in oral cavity. The object of this study was to explore the effect of surface properties including surface roughness and hydrophobicity on the adhesion and biofilm formation of Streptococcus mutans (S. mutans) to zirconia. Atomic force microscopy was employed to determine the zirconia surface morphology and the adhesion forces between the S. mutans and zirconia. The results showed that the surface roughness was nanoscale and significantly different among tested groups (P Medium (17.00 ± 3.81 nm) > Fine (11.89 ± 1.68 nm). The contact angles of the Coarse group were the highest, followed by the Medium and the Fine groups. Increasing the surface roughness and hydrophobicity resulted in an increase of adhesion forces and early attachment (2 h and 4 h) of S. mutans on the zirconia but no influence on the further development of biofilm (6 h~24 h). Our findings suggest that the surface roughness in nanoscale and hydrophobicity of zirconia had influence on the S. mutans initial adhesion force and early attachment instead of whole stages of biofilm formation. PMID:27975061

  11. SGP Cloud and Land Surface Interaction Campaign (CLASIC): Measurement Platforms

    Energy Technology Data Exchange (ETDEWEB)

    MA Miller; R Avissar; LK Berg; SA Edgerton; ML Fischer; TJ Jackson; B. Kustas; PJ Lamb; G McFarquhar; Q Min; B Schmid; MS Torn; DD Tuner

    2007-06-01

    The Cloud and Land Surface Interaction Campaign (CLASIC) will be conducted from June 8 to June 30, 2007, at the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) Climate Research Facility (ACRF) Southern Great Plains (SGP) site. Data will be collected using eight aircraft equipped with a variety of specialized sensors, four specially instrumented surface sites, and two prototype surface radar systems. The architecture of CLASIC includes a high-altitude surveillance aircraft and enhanced vertical thermodynamic and wind profile measurements that will characterize the synoptic scale structure of the clouds and the land surface within the ACRF SGP site. Mesoscale and microscale structures will be sampled with a variety of aircraft, surface, and radar observations. An overview of the measurement platforms that will be used during the CLASIC are described in this report. The coordination of measurements, especially as it relates to aircraft flight plans, will be discussed in the CLASIC Implementation Plan.

  12. Sikorsky interactive graphics surface design/manufacturing system

    Science.gov (United States)

    Robbins, R.

    1975-01-01

    An interactive graphics system conceived to be used in the design, analysis, and manufacturing of aircraft components with free form surfaces was described. In addition to the basic surface definition and viewing capabilities inherent in such a system, numerous other features are present: surface editing, automated smoothing of control curves, variable milling patch boundary definitions, surface intersection definition and viewing, automatic creation of true offset surfaces, digitizer and drafting machine interfaces, and cutter path optimization. Documented costs and time savings of better than six to one are being realized with this system. The system was written in FORTRAN and GSP for use on IBM 2250 CRT's in conjunction with an IBM 370/158 computer.

  13. On the Interaction of Capillary Shapes with Solid Surfaces

    NARCIS (Netherlands)

    Musterd, M.

    2015-01-01

    Control over the interaction of droplets with solid surfaces is commonplace in nature. Famous examples are the water-shedding capabilities of the lotus leaf and the water-harvesting skin of certain types of beetles. To date, this type of control remains a challenge in engineering applications.

  14. The interaction between surface water and groundwater and its ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 125; Issue 7. The interaction between surface water and groundwater and its effect on water quality in the Second Songhua River basin, northeast China. Bing Zhang Xianfang Song Yinghua Zhang Ying Ma Changyuan Tang Lihu Yang Zhong-Liang Wang. Volume ...

  15. Nonlinear interaction of the surface waves at a plasma boundary

    International Nuclear Information System (INIS)

    Dolgopolov, V.V.; El-Naggar, I.A.; Hussein, A.M.; Khalil, Sh.M.

    1976-01-01

    Amplitudes of electromagnetic waves with combination frequencies, radiating from the plasma boundary due to nonlinear interaction of the surface waves, have been found. Previous papers on this subject did not take into account that the tangential components of the electric field of waves with combination frequencies were discontinuous at the plasma boundary. (Auth.)

  16. Spatial spectrograms of vibrating atomic force microscopy cantilevers coupled to sample surfaces

    International Nuclear Information System (INIS)

    Wagner, Ryan; Raman, Arvind; Proksch, Roger

    2013-01-01

    Many advanced dynamic Atomic Force Microscopy (AFM) techniques such as contact resonance, force modulation, piezoresponse force microscopy, electrochemical strain microscopy, and AFM infrared spectroscopy exploit the dynamic response of a cantilever in contact with a sample to extract local material properties. Achieving quantitative results in these techniques usually requires the assumption of a certain shape of cantilever vibration. We present a technique that allows in-situ measurements of the vibrational shape of AFM cantilevers coupled to surfaces. This technique opens up unique approaches to nanoscale material property mapping, which are not possible with single point measurements alone

  17. Interaction of β-sheet folds with a gold surface.

    Directory of Open Access Journals (Sweden)

    Martin Hoefling

    Full Text Available The adsorption of proteins on inorganic surfaces is of fundamental biological importance. Further, biomedical and nanotechnological applications increasingly use interfaces between inorganic material and polypeptides. Yet, the underlying adsorption mechanism of polypeptides on surfaces is not well understood and experimentally difficult to analyze. Therefore, we investigate here the interactions of polypeptides with a gold(111 surface using computational molecular dynamics (MD simulations with a polarizable gold model in explicit water. Our focus in this paper is the investigation of the interaction of polypeptides with β-sheet folds. First, we concentrate on a β-sheet forming model peptide. Second, we investigate the interactions of two domains with high β-sheet content of the biologically important extracellular matrix protein fibronectin (FN. We find that adsorption occurs in a stepwise mechanism both for the model peptide and the protein. The positively charged amino acid Arg facilitates the initial contact formation between protein and gold surface. Our results suggest that an effective gold-binding surface patch is overall uncharged, but contains Arg for contact initiation. The polypeptides do not unfold on the gold surface within the simulation time. However, for the two FN domains, the relative domain-domain orientation changes. The observation of a very fast and strong adsorption indicates that in a biological matrix, no bare gold surfaces will be present. Hence, the bioactivity of gold surfaces (like bare gold nanoparticles will critically depend on the history of particle administration and the proteins present during initial contact between gold and biological material. Further, gold particles may act as seeds for protein aggregation. Structural re-organization and protein aggregation are potentially of immunological importance.

  18. Cluster-surface interaction: from soft landing to implantation

    DEFF Research Database (Denmark)

    Popok, Vladimir; Barke, Ingo; Campbell, Eleanor E.B.

    2011-01-01

    The current paper presents a state-of-the-art review in the field of interaction of atomic and molecular clusters with solids. We do not attempt to overview the entire broad field but rather concentrate on impact phenomena: how the physics of the cluster-surface interaction depends on the kinetic...... for utilisation in optics and electronics, as magnetic media and catalysts, in nanobiology and nanomedicine. We pay considerable attention to phenomena occurring on impact of clusters with increased kinetic energies. In particular, we discuss the physics of the intermediate regime between deposition...... for efficient smoothing of surfaces on the macroscopic scale. Several examples of successful applications of the cluster beam technique for polishing of surfaces are given. We also discuss how the physical sputtering can be combined with reactive accelerated cluster erosion. The latter can be an efficient tool...

  19. Photoresponsive peptide azobenzene conjugates that specifically interact with platinum surfaces

    Science.gov (United States)

    Dinçer, S.; Tamerler, C.; Sarıkaya, M.; Pişkin, E.

    2008-05-01

    The aim of this study is to prepare photoresponsive peptide-azobenzene compounds which interacts with platinum surfaces specifically, in order to create smart surfaces for further novel applications in design of smart biosensors and array platforms. Here, a water-soluble azobenzene molecule, 4-hydroxyazo benzene,4-sulfonic acid was synthesized by diazo coupling reaction. A platinum-specific peptide, originally selected by a phage display technique was chemically synthesized/purchased, and conjugated with the azobenzene compound activated with carbonyldiimidazole. Both azobenzene and its conjugate were characterized (including photoresponsive properties) by FTIR, NMR, and UV-spectrophotometer. The yield of conjugation reaction estimated by ninhydrin assay was about 65%. Peptide incorporation did not restrict the light-sensitivity of azobenzene. Adsorption of both the peptide and its azobenzene conjugate was followed by Quartz Crystal Microbalance (QCM) system. The kinetic evaluations exhibited that both molecules interact platinum surfaces, quite rapidly and strongly.

  20. Use of Atomic Force Microscopy to Study the Multi-Modular Interaction of Bacterial Adhesins to Mucins

    Directory of Open Access Journals (Sweden)

    A. Patrick Gunning

    2016-11-01

    Full Text Available The mucus layer covering the gastrointestinal (GI epithelium is critical in selecting and maintaining homeostatic interactions with our gut bacteria. However, the molecular details of these interactions are not well understood. Here, we provide mechanistic insights into the adhesion properties of the canonical mucus-binding protein (MUB, a large multi-repeat cell–surface adhesin found in Lactobacillus inhabiting the GI tract. We used atomic force microscopy to unravel the mechanism driving MUB-mediated adhesion to mucins. Using single-molecule force spectroscopy we showed that MUB displayed remarkable adhesive properties favouring a nanospring-like adhesion model between MUB and mucin mediated by unfolding of the multiple repeats constituting the adhesin. We obtained direct evidence for MUB self-interaction; MUB–MUB followed a similar binding pattern, confirming that MUB modular structure mediated such mechanism. This was in marked contrast with the mucin adhesion behaviour presented by Galectin-3 (Gal-3, a mammalian lectin characterised by a single carbohydrate binding domain (CRD. The binding mechanisms reported here perfectly match the particular structural organization of MUB, which maximizes interactions with the mucin glycan receptors through its long and linear multi-repeat structure, potentiating the retention of bacteria within the outer mucus layer.

  1. Multi-scale surface-groundwater interactions: Processes and Implications

    Science.gov (United States)

    Packman, A. I.; Harvey, J. W.; Worman, A.; Cardenas, M. B.; Schumer, R.; Jerolmack, D. J.; Tank, J. L.; Stonedahl, S. H.

    2009-05-01

    Site-based investigations of stream-subsurface interactions normally focus on a limited range of spatial scales - typically either very shallow subsurface flows in the hyporheic zone, or much larger scale surface- groundwater interactions - but subsurface flows are linked across this entire continuum. Broad, multi-scale surface-groundwater interactions produce complex patterns in porewater flows, and interfacial fluxes do not average in a simple fashion because of the competitive effects of flows induced at different scales. For example, reach-scale stream-groundwater interactions produce sequences of gaining and losing reaches that can either suppress or enhance local-scale hyporheic exchange. Many individual topographic features also produce long power-law tails in surface residence time distributions, and the duration of these tails is greatly extended by interactions over a wide range of spatial scales. Simultaneous sediment transport and landscape evolution further complicates the analysis of porewater flow dynamics in rivers. Finally, inhomogeneity in important biogeochemical processes, particularly microbial processes that are stimulated near the sediment- water interface, leads to a great degree of non-linearity in chemical transformation rates in stream channels. This high degree of complexity in fluvial systems requires that careful approaches be used to extend local observations of hyporheic exchange and associated nutrient, carbon, and contaminant transformations to larger spatial scales. It is important to recognize that conventional advection-dispersion models are not expected to apply, and instead anomalous transport models must be used. Unfortunately, no generally applicable model is available for stream-groundwater interactions at the present time. Alternative approaches for modeling conservative and reactive transport will be discussed, and a strategy articulated for coping with the complexity of coupled surface-subsurface dynamics in fluvial

  2. Interactions between internal forces, body stiffness, and fluid environment in a neuromechanical model of lamprey swimming.

    Science.gov (United States)

    Tytell, Eric D; Hsu, Chia-Yu; Williams, Thelma L; Cohen, Avis H; Fauci, Lisa J

    2010-11-16

    Animal movements result from a complex balance of many different forces. Muscles produce force to move the body; the body has inertial, elastic, and damping properties that may aid or oppose the muscle force; and the environment produces reaction forces back on the body. The actual motion is an emergent property of these interactions. To examine the roles of body stiffness, muscle activation, and fluid environment for swimming animals, a computational model of a lamprey was developed. The model uses an immersed boundary framework that fully couples the Navier-Stokes equations of fluid dynamics with an actuated, elastic body model. This is the first model at a Reynolds number appropriate for a swimming fish that captures the complete fluid-structure interaction, in which the body deforms according to both internal muscular forces and external fluid forces. Results indicate that identical muscle activation patterns can produce different kinematics depending on body stiffness, and the optimal value of stiffness for maximum acceleration is different from that for maximum steady swimming speed. Additionally, negative muscle work, observed in many fishes, emerges at higher tail beat frequencies without sensory input and may contribute to energy efficiency. Swimming fishes that can tune their body stiffness by appropriately timed muscle contractions may therefore be able to optimize the passive dynamics of their bodies to maximize peak acceleration or swimming speed.

  3. Sensitivity of surface temperature to radiative forcing by contrail cirrus in a radiative-mixing model

    Science.gov (United States)

    Schumann, Ulrich; Mayer, Bernhard

    2017-11-01

    Earth's surface temperature sensitivity to radiative forcing (RF) by contrail cirrus and the related RF efficacy relative to CO2 are investigated in a one-dimensional idealized model of the atmosphere. The model includes energy transport by shortwave (SW) and longwave (LW) radiation and by mixing in an otherwise fixed reference atmosphere (no other feedbacks). Mixing includes convective adjustment and turbulent diffusion, where the latter is related to the vertical component of mixing by large-scale eddies. The conceptual study shows that the surface temperature sensitivity to given contrail RF depends strongly on the timescales of energy transport by mixing and radiation. The timescales are derived for steady layered heating (ghost forcing) and for a transient contrail cirrus case. The radiative timescales are shortest at the surface and shorter in the troposphere than in the mid-stratosphere. Without mixing, a large part of the energy induced into the upper troposphere by radiation due to contrails or similar disturbances gets lost to space before it can contribute to surface warming. Because of the different radiative forcing at the surface and at top of atmosphere (TOA) and different radiative heating rate profiles in the troposphere, the local surface temperature sensitivity to stratosphere-adjusted RF is larger for SW than for LW contrail forcing. Without mixing, the surface energy budget is more important for surface warming than the TOA budget. Hence, surface warming by contrails is smaller than suggested by the net RF at TOA. For zero mixing, cooling by contrails cannot be excluded. This may in part explain low efficacy values for contrails found in previous global circulation model studies. Possible implications of this study are discussed. Since the results of this study are model dependent, they should be tested with a comprehensive climate model in the future.

  4. Sensitivity of surface temperature to radiative forcing by contrail cirrus in a radiative-mixing model

    Directory of Open Access Journals (Sweden)

    U. Schumann

    2017-11-01

    Full Text Available Earth's surface temperature sensitivity to radiative forcing (RF by contrail cirrus and the related RF efficacy relative to CO2 are investigated in a one-dimensional idealized model of the atmosphere. The model includes energy transport by shortwave (SW and longwave (LW radiation and by mixing in an otherwise fixed reference atmosphere (no other feedbacks. Mixing includes convective adjustment and turbulent diffusion, where the latter is related to the vertical component of mixing by large-scale eddies. The conceptual study shows that the surface temperature sensitivity to given contrail RF depends strongly on the timescales of energy transport by mixing and radiation. The timescales are derived for steady layered heating (ghost forcing and for a transient contrail cirrus case. The radiative timescales are shortest at the surface and shorter in the troposphere than in the mid-stratosphere. Without mixing, a large part of the energy induced into the upper troposphere by radiation due to contrails or similar disturbances gets lost to space before it can contribute to surface warming. Because of the different radiative forcing at the surface and at top of atmosphere (TOA and different radiative heating rate profiles in the troposphere, the local surface temperature sensitivity to stratosphere-adjusted RF is larger for SW than for LW contrail forcing. Without mixing, the surface energy budget is more important for surface warming than the TOA budget. Hence, surface warming by contrails is smaller than suggested by the net RF at TOA. For zero mixing, cooling by contrails cannot be excluded. This may in part explain low efficacy values for contrails found in previous global circulation model studies. Possible implications of this study are discussed. Since the results of this study are model dependent, they should be tested with a comprehensive climate model in the future.

  5. Track sensitivity and the surface roughness measurements of CR-39 with atomic force microscope

    CERN Document Server

    Yasuda, N; Amemiya, K; Takahashi, H; Kyan, A; Ogura, K

    1999-01-01

    Atomic Force Microscope (AFM) has been applied to evaluate the surface roughness and the track sensitivity of CR-39 track detector. We experimentally confirmed the inverse correlation between the track sensitivity and the roughness of the detector surface after etching. The surface of CR-39 (CR-39 doped with antioxidant (HARZLAS (TD-1)) and copolymer of CR-39/NIPAAm (TNF-1)) with high sensitivity becomes rough by the etching, while the pure CR-39 (BARYOTRAK) with low sensitivity keeps its original surface clarity even for the long etching.

  6. Evaluation of the roughness of the surface of porcelain systems with the atomic force microscope

    International Nuclear Information System (INIS)

    Chavarria Rodriguez, Bernal

    2013-01-01

    The surface of a dental ceramic was evaluated and compared with an atomic force microscope after being treated with different systems of polishing. 14 identical ceramic Lava® Zirconia discs were used to test the different polishing systems. 3 polishing systems from different matrix houses were used to polish dental porcelain. The samples were evaluated quantitatively with an atomic force microscope in order to study the real effectiveness of each system, on the roughness average (Ra) and the maximum peak to valley roughness (Ry) of the ceramic surfaces. A considerable reduction of the surface roughness was obtained by applying different polishing systems on the surface of dental ceramics. Very reliable values of Ra and Ry were obtained by making measurements on the structure reproduced by the atomic force microscope. The advanced ceramics of zirconium oxide presented the best physical characteristics and low levels of surface roughness. A smoother surface was achieved with the application of polishing systems, thus demonstrating the reduction of the surface roughness of a dental ceramic [es

  7. Asymptotic Completeness for Relativistic Kinetic Equations with Short-range Interaction Forces

    OpenAIRE

    Ha, Seung-Yeal; Kim, Yong Duck; Lee, Ho; Noh, Se Eun

    2007-01-01

    We present an $L^1$-asymptotic completeness results for relativistic kinetic equations with short range interaction forces. We show that the uniform phase space-time bound for nonlinear terms to the relativistic nonlinear kinetic equations yields the asymptotic completeness of the relativistic kinetic equations. For this space-time bound, we employ dispersive estimates and explicit construction of a Lyapunov functional.

  8. Interaction potential and repulsive force between atoms whose internuclear separations are small

    International Nuclear Information System (INIS)

    Barbaro, Jacques

    1971-01-01

    The Thomas-Fermi equation is solved for the homonuclear diatomic molecule. The electronic density and electrostatic potential at each point are used to calculate energies and interaction potentials for very small internuclear separation distances. The repulsive force between atoms is derived by means of the virial theorem. (author) [fr

  9. Cation-Pi Interaction: A Key Force for Sorption of Fluoroquinolone Antibiotics on Pyrogenic Carbonaceous Materials.

    Science.gov (United States)

    Zhao, Qing; Zhang, Siyu; Zhang, Xuejiao; Lei, Lei; Ma, Wei; Ma, Chuanxin; Song, Lei; Chen, Jingwen; Pan, Bo; Xing, Baoshan

    2017-12-05

    Cation-pi attraction is a major force that determines macromolecular structures and drug-receptor interactions. However, the role of the cation-pi interaction in sorption of fluoroquinolone antibiotics by pyrogenic carbonaceous materials (PCMs) has not been addressed. We studied sorption of ciprofloxacin (CIP) on graphite to quantify the contribution of the cation-pi interaction. Through competition experiments, the decreased amount of sorbed CIP by sequential treatment with hexadecane, phenanthrene and benzylamine represents the contribution of hydrophobic, pi-pi and cation-pi interactions, respectively. Benzylamine competed more strongly with CIP than n-hexadecane and phenanthrene, indicating that cation-pi is a major force. Cation-pi interactions accounted for up to 72.6% of the total sorption at an initial CIP concentration of 0.000015 mmol/L. Importantly, species transformation (CIP(0) captures H + from water to form CIP(+1)) induced by cation-pi interactions was verified both experimentally and theoretically and can be used to explain the environmental behavior of other fluoroquinolone antibiotics and biochemical processes of amino acids that interact with aromatic moieties. Because of the significant role of cation-pi interactions, CIP desorption increased up to 2.32 times when Na + increased from 0.01 mM to 0.45 mM, which is an environmentally relevant scenario at river estuaries. Hence, behaviors of fluoroquinolone antibiotics that are affected by ionic strength changes need to be carefully evaluated, especially in river estuaries.

  10. Investigation of a mutual interaction force at different pressure amplitudes in sulfuric acid

    International Nuclear Information System (INIS)

    Rezaee, Nastaran; Sadighi-Bonabi, Rasoul; Mirheydari, Mona; Ebrahimi, Homa

    2011-01-01

    This paper investigates the secondary Bjerknes force for two oscillating bubbles in various pressure amplitudes in a concentration of 95% sulfuric acid. The equilibrium radii of the bubbles are assumed to be smaller than 10 μm at a frequency of 37 kHz in various strong driving acoustical fields around 2.0 bars (1 bar=10 5 Pa). The secondary Bjerknes force is investigated in uncoupled and coupled states between the bubbles, with regard to the quasi-adiabatic model for the bubble interior. It finds that the value of the secondary Bjerknes force depends on the driven pressure of sulfuric acid and its amount would be increased by liquid pressure amplitude enhancement. The results show that the repulsion area of the interaction force would be increased by increasing the driven pressure because of nonlinear oscillation of bubbles. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  11. Nonsmooth Newton method for Fischer function reformulation of contact force problems for interactive rigid body simulation

    DEFF Research Database (Denmark)

    Silcowitz, Morten; Niebe, Sarah Maria; Erleben, Kenny

    2009-01-01

    contact response. In this paper, we present a new approach to contact force determination. We reformulate the contact force problem as a nonlinear root search problem, using a Fischer function. We solve this problem using a generalized Newton method. Our new Fischer - Newton method shows improved......n interactive physical simulation, contact forces are applied to prevent rigid bodies from penetrating each other. Accurate contact force determination is a computationally hard problem. Thus, in practice one trades accuracy for performance. The result is visual artifacts such as viscous or damped...... qualities for specific configurations where the most widespread alternative, the Projected Gauss-Seidel method, fails. Experiments show superior convergence properties of the exact Fischer - Newton method....

  12. Determination, by neutron diffraction, of basic interaction forces for flux pinning in superconductors

    International Nuclear Information System (INIS)

    Lippmann, G.; Schelten, J.; Schmatz, W.

    1976-01-01

    A new method has been developed for the determination of the basic interaction force exerted on the flux lines in type II superconductors. From neutron diffraction by flux line lattices in the two-phase system Nb with Nb 2 N precipitates of a well defined metallurgical structure, it is observed that the flux lines are bent due to the presence of pinning centres. A measure for the bending is the width of the rocking curve which is rather directly related to the main basic interaction force (f 2 )sup(1/2). For four specimens with different number densities of precipitates from 1.3 x 10 17 to 1.3 x 10 18 m -3 the force (f 2 )sup(1/2) has been evaluated as a function of the flux density B from the angular widths of the measured rocking curves. These widths ranged from 6' to 4 0 . The basic interaction forces were independent of the number density; at B/Bsub(c2) = 0.5 a value (f 2 )sup(1/2) = 2 x 10 -10 N was obtained. The maximum interaction force K 0 obtained from the pinning force densities for one sample agreed well with (f 2 )sup(1/2). Reasonable agreements result from further comparisons of (f 2 )sup(1/2) with K 0 at B = 0 calculated from superconductivity parameters and also with K 0 S measured by Antesberger and Ullmaier (Antesberger, G. and Ullmaier, H.; 1974, Phil. Mag., vol. 29, 1101) on the alloy NbTa which has a precipitate structure similar to that of the Nb samples. (author)

  13. Effects of Polishing Bur Application Force and Reuse on Sintered Zirconia Surface Topography.

    Science.gov (United States)

    Fischer, N G; Tsujimoto, A; Baruth, A G

    2018-03-16

    Limited information is available on how to polish and finish zirconia surfaces following computer-aided design/computer-aided manufacturing (CAD/CAM), specifically, how differing application forces and reuse of zirconia polishing systems affect zirconia topography. To determine the effect of differing, clinically relevant, polishing application forces and multiple usages of polishing burs on the surface topography of CAD/CAM zirconia. One hundred twenty 220-grit carbide finished zirconia disks were sintered according to manufacturer's directions and divided into two groups for the study of two coarse polishing bur types. Each group was divided into subgroups for polishing (15,000 rpm) at 15 seconds for 1.0 N, 4.5 N, or 11 N of force using a purpose-built fixture. Subgroups were further divided to study the effects of polishing for the first, fifth, 15th, and 30th bur use, simulating clinical procedures. Unpolished surfaces served as a control group. Surfaces were imaged with noncontact optical profilometry (OP) and atomic force microscopy (AFM) to measure average roughness values (Ra). Polishing burs were optically examined for wear. Scanning electron microscopy (SEM) was performed on burs and zirconia surfaces. One-way ANOVA with post hoc Tukey HSD (honest significant difference) tests (α=0.05) were used for statistical analyses. AFM and OP Ra values of all polished surfaces were significantly lower than those of the unpolished control. Different polishing forces and bur reuse showed no significant differences in AFM Ra. However, significant differences in OP Ra were found due to differing application forces and bur reuse between the first and subsequent uses. SEM and optical micrographs revealed notable bur wear, increasing with increasing reuse. SEM and AFM micrographs clearly showed polished, periodic zirconia surfaces. Nanoscale topography, as analyzed with kurtosis and average groove depth, was found dependent on the specific polishing bur type. These in

  14. Surface interactions involved in flashover with high density electronegative gases.

    Energy Technology Data Exchange (ETDEWEB)

    Hodge, Keith Conquest; Warne, Larry Kevin; Jorgenson, Roy Eberhardt; Wallace, Zachariah Red; Lehr, Jane Marie

    2010-01-01

    This report examines the interactions involved with flashover along a surface in high density electronegative gases. The focus is on fast ionization processes rather than the later time ionic drift or thermalization of the discharge. A kinetic simulation of the gas and surface is used to examine electron multiplication and includes gas collision, excitation and ionization, and attachment processes, gas photoionization and surface photoemission processes, as well as surface attachment. These rates are then used in a 1.5D fluid ionization wave (streamer) model to study streamer propagation with and without the surface in air and in SF6. The 1.5D model therefore includes rates for all these processes. To get a better estimate for the behavior of the radius we have studied radial expansion of the streamer in air and in SF6. The focus of the modeling is on voltage and field level changes (with and without a surface) rather than secondary effects, such as, velocities or changes in discharge path. An experiment has been set up to carry out measurements of threshold voltages, streamer velocities, and other discharge characteristics. This setup includes both electrical and photographic diagnostics (streak and framing cameras). We have observed little change in critical field levels (where avalanche multiplication sets in) in the gas alone versus with the surface. Comparisons between model calculations and experimental measurements are in agreement with this. We have examined streamer sustaining fields (field which maintains ionization wave propagation) in the gas and on the surface. Agreement of the gas levels with available literature is good and agreement between experiment and calculation is good also. Model calculations do not indicate much difference between the gas alone versus the surface levels. Experiments have identified differences in velocity between streamers on the surface and in the gas alone (the surface values being larger).

  15. Posterior Parietal Cortex Encoding of Dynamic Hand Force Underlying Hand-Object Interaction.

    Science.gov (United States)

    Ferrari-Toniolo, Simone; Visco-Comandini, Federica; Papazachariadis, Odysseas; Caminiti, Roberto; Battaglia-Mayer, Alexandra

    2015-08-05

    Major achievements of primate evolution are skilled hand-object interaction and tool use, both in part dependent on parietal cortex expansion. We recorded spiking activity from macaque inferior parietal cortex during directional manipulation of an isometric tool, which required the application of hand forces to control a cursor's motion on a screen. In areas PFG/PF, the activity of ∼ 70% neurons was modulated by the hand force necessary to implement the desired target motion, reflecting an inverse model, rather than by the intended motion of the visual cursor (forward model). The population vector matched the direction and amplitude of the instantaneous force increments over time. When exposed to a new force condition, that obliged the monkey to change the force output to successfully bring the cursor to the final target, the activity of a consistent subpopulation of neurons changed in an orderly fashion and, at the end of a "Wash-out" session, retained memory of the new learned association, at the service of predictive control of force. Our findings suggest that areas PFG/PF represent a crucial node of the distributed control of hand force, by encoding instantaneous force variations and serving as a memory reservoir of hand dynamics required for object manipulation and tool use. This is coherent with previous studies in humans showing the following: (1) impaired adaptation to a new force field under TMS parietal perturbation; (2) defective control of direction of hand force after parietal lesion; and (3) fMRI activation of parietal cortex during object manipulation requiring control of fine hand forces. Skilled object manipulation and tool use are major achievements of primate evolution, both largely dependent on posterior parietal cortex (PPC) expansion. Neurophysiological and fMRI studies in macaque and humans had documented a crucial role of PPC in encoding the hand kinematics underlying these functions, leaving to premotor and motor areas the role of

  16. Viscoelastic crack propagation and closing with Lennard-Jones surface forces

    International Nuclear Information System (INIS)

    Greenwood, J A

    2007-01-01

    An analysis of the opening and closing of a crack in a viscoelastic solid has been made assuming a Lennard-Jones law of force acting between the crack faces. The results are compared with those of an earlier analysis in which a simple Dugdale model of the surface forces was assumed. The approximate 'reciprocal rule' between the apparent surface energies for opening and closing cracks is confirmed. At low speeds a linear relation between the apparent surface energy and the crack speed is found. The lengths of the process zone for opening and closing cracks are found to be very similar and so presumably are not responsible for the very different values of the apparent surface energy

  17. Viscoelastic crack propagation and closing with Lennard-Jones surface forces

    Energy Technology Data Exchange (ETDEWEB)

    Greenwood, J A [Department of Engineering, Trumpington Street, Cambridge, CB2 1PZ (United Kingdom)

    2007-03-21

    An analysis of the opening and closing of a crack in a viscoelastic solid has been made assuming a Lennard-Jones law of force acting between the crack faces. The results are compared with those of an earlier analysis in which a simple Dugdale model of the surface forces was assumed. The approximate 'reciprocal rule' between the apparent surface energies for opening and closing cracks is confirmed. At low speeds a linear relation between the apparent surface energy and the crack speed is found. The lengths of the process zone for opening and closing cracks are found to be very similar and so presumably are not responsible for the very different values of the apparent surface energy.

  18. Cutting force analysis as a tool for evaluating the surface quality of machined parts

    International Nuclear Information System (INIS)

    Sanchez-Carrilero, M.; Marcos, M.; Alvarez-Alcon, M.; Sanchez-Corbacho, V.M.

    1998-01-01

    Surface quality is one of the most important criteria for establishing the optimum cutting parameters needed to perform a machining process. Usually, the evaluation of the degree of the surface finishing requires to apply metrological techniques which involve times out in the production. As a consequence of this, a loss in both the economy of the process and the fiability of the tests reproducibility can be produced. In this work a relation between cutting force and surface roughness has been studied for the turning process of an Al-Cu alloy. From this relation, the surface quality of the machined samples can be evaluated by using the cutting forces values acquired during the cutting process. (Author) 8 refs

  19. Interactions of Candida albicans with host epithelial surfaces

    Directory of Open Access Journals (Sweden)

    David W. Williams

    2013-10-01

    Full Text Available Candida albicans is an opportunistic, fungal pathogen of humans that frequently causes superficial infections of oral and vaginal mucosal surfaces of debilitated and susceptible individuals. The organism is however, commonly encountered as a commensal in healthy individuals where it is a component of the normal microflora. The key determinant in the type of relationship that Candida has with its host is how it interacts with the epithelial surface it colonises. A delicate balance clearly exists between the potentially damaging effects of Candida virulence factors and the nature of the immune response elicited by the host. Frequently, it is changes in host factors that lead to Candida seemingly changing from a commensal to pathogenic existence. However, given the often reported heterogeneity in morphological and biochemical factors that exist between Candida species and indeed strains of C. albicans, it may also be the fact that colonising strains differ in the way they exploit resources to allow persistence at mucosal surfaces and as a consequence this too may affect the way Candida interacts with epithelial cells. The aim of this review is to provide an overview of some of the possible interactions that may occur between C. albicans and host epithelial surfaces that may in turn dictate whether Candida removal, its commensal persistence or infection follows.

  20. Interaction of cement model systems with superplasticizers investigated by atomic force microscopy, zeta potential, and adsorption measurements.

    Science.gov (United States)

    Ferrari, Lucia; Kaufmann, Josef; Winnefeld, Frank; Plank, Johann

    2010-07-01

    Polyelectrolyte-based dispersants are commonly used in a wide range of industrial applications to provide specific workability to colloidal suspensions. Their working mechanism is based on adsorption onto the surfaces of the suspended particles. The adsorbed polymer layer can exercise an electrostatic and/or a steric effect which is responsible for achieving dispersion. This study is focused on the dispersion forces induced by polycarboxylate ether-based superplasticizers (PCEs) commonly used in concrete. They are investigated by atomic force microscopy (AFM) applying standard silicon nitride tips exposed to solutions with different ionic compositions in a wet cell. Adsorption isotherms and zeta potential analysis were performed to characterize polymer displacement in the AFM system on nonreactive model substrates (quartz, mica, calcite, and magnesium oxide) in order to avoid the complexity of cement hydration products. The results show that PCE is strongly adsorbed by positively charged materials. This fact reveals that, being silicon nitride naturally positively charged, in most cases the superplasticizer adsorbs preferably on the silicon nitride tip than on the AFM substrate. However, the force-distance curves displayed repulsive interactions between tip and substrates even when polymer was poorly adsorbed on both. These observations allow us to conclude that the dispersion due to PCE strongly depends on the particle charge. It differs between colloids adsorbing and not adsorbing PCE, and leads to different forces acting between the particles. Copyright 2010 Elsevier Inc. All rights reserved.

  1. Interaction of hydrogen and oxygen with bulk defects and surfaces of metals

    International Nuclear Information System (INIS)

    Besenbacher, F.

    1994-05-01

    The thesis deals with the interaction of hydrogen with defects in metals and the interaction of hydrogen and oxygen with metal surfaces studied by ion-beam techniques and scanning tunneling microscopy (STM), respectively. The first part of the thesis discusses the interaction of hydrogen with simple defects in transition metals. The trap-binding enthalpies and the lattice location of hydrogen trapped to vacancies have been determined, and an extremely simple and versatile picture of the hydrogen-metal interaction has evolved, in which the trap strength is mainly determined by the local electron density. Any dilution of the lattice will lead to a trap, vacancies and voids being the strongest trap. It is found that hydrogen trapped to vacancies in fcc metals is quantum-mechanically delocalized, and the excitation energies for the hydrogen in the vacancy potential are a few MeV only. The interaction of hydrogen with metal surfaces is studied by the transmission channeling (TC) technique. It is found that hydrogen chemisorbs in the highest-coordinated sites on the surfaces, and that there is a direct relationship between the hydrogen-metal bond length and the coordination number for the hydrogen. In the final part of the thesis the dynamics of the chemisorption process for oxygen and hydrogen on metal surfaces is studied by STM, a fascinating and powerful technique for exploring the atomic-scale realm of surfaces. It is found that there is a strong coupling between the chemisorption process and the distortion of the metal surface. The adsorbates induce a surface reconstruction, i.e. metal-metal bond breaks and metal-adsorbate bounds form. Whereas hydrogen interacts weakly with the metals and induces reconstructions where only nnn metals bonds are broken, oxygen interacts strongly with the metal, and the driving force for the O-induced reconstructions appears to be the formation of low-coordinated metal-O rows, formed by breaking of nn metal bonds. Finally it is shown

  2. Development of a reactive force field for the Fe-C interaction to investigate the carburization of iron.

    Science.gov (United States)

    Lu, Kuan; Huo, Chun-Fang; Guo, Wen-Ping; Liu, Xing-Wu; Zhou, Yuwei; Peng, Qing; Yang, Yong; Li, Yong-Wang; Wen, Xiao-Dong

    2018-01-03

    The approach of molecular dynamics with Reactive Force Field (ReaxFF) is a promising way to investigate the carburization of iron which is pivotal in the preparation of desired iron-based materials and catalysts. However, it is a challenge to develop a reliable ReaxFF to describe the Fe-C interaction, especially when it involves bond rearrangement. In this work, we develop an exclusive set of Reactive Force Field (ReaxFF) parameters, denoted RPOIC-2017, to describe the diffusion behavior of carbon atoms in the α-Fe system. It inherited some partial parameters in 2012 (ReaxFF-2012) which are suitable for hydrogen adsorption and dissociation. This set of parameters is trained against data from first-principles calculations, including the equations of state of α-Fe, the crystal constant of Fe 3 C and Fe 4 C, a variety of periodic surface structures with varying carbon coverages, as well as the barriers of carbon diffusion in the α-Fe bulk and on diverse surfaces. The success in predicting the carbon diffusion coefficient and the diffusion barrier using the developed RPOIC-2017 potential demonstrates that the performance is superior to that of the traditional MEAM potential. The new ReaxFF for the Fe-C interaction developed in this work is not only essential for the design of novel iron based materials, but could also help understand atomic arrangements and the interfacial structure of iron carbides.

  3. An investigation of force, surface roughness and chip in surface grinding of SKD 11 tool steel using minimum quantity lubrication-MQL technique

    Science.gov (United States)

    Soepangkat, Bobby O. P.; Agustin, H. C. Kis; Subiyanto, H.

    2017-06-01

    This research aimed to analyze the viability of the minimum quantity of lubricant (MQL) technique towards normal force, tangential force, surface roughness and chip formation in surface grinding of SKD 11 tool steel. The three surface grinding parameters were varied including the type of cooling method (MQL and dry), table speed, and depth of cut. Based on statistical analysis, depth of cut is the most influential factor which affects the four responses in both dry and MQL grinding. MQL could reduce normal force and tangential force considerably, but produce higher surface roughness. In MQL grinding, the chips removal took place mostly by shearing and fracturing.

  4. Direct measurement of colloidal interactions between polyaniline surfaces in a UV-curable coating formulation: the effect of surface hydrophilicity/hydrophobicity and resin composition.

    Science.gov (United States)

    Jafarzadeh, Shadi; Claesson, Per M; Pan, Jinshan; Thormann, Esben

    2014-02-04

    The interactions between polyaniline particles and polyaniline surfaces in polyester acrylate resin mixed with 1,6-hexanediol diacrylate monomer have been investigated using contact angle measurements and the atomic force microscopy colloidal probe technique. Polyaniline with different characteristics (hydrophilic and hydrophobic) were synthesized directly on spherical polystyrene particles of 10 μm in diameter. Surface forces were measured between core/shell structured polystyrene/polyaniline particles (and a pure polystyrene particle as reference) mounted on an atomic force microscope cantilever and a pressed pellet of either hydrophilic or hydrophobic polyaniline powders, in resins of various polymer:monomer ratios. A short-range purely repulsive interaction was observed between hydrophilic polyaniline (doped with phosphoric acid) surfaces in polyester acrylate resin. In contrast, interactions between hydrophobic polyaniline (doped with n-decyl phosphonic acid) were dominated by attractive forces, suggesting less compatibility and higher tendency for aggregation of these particles in liquid polyester acrylate compared to hydrophilic polyaniline. Both observations are in agreement with the conclusions from the interfacial energy studies performed by contact angle measurements.

  5. Engineering optical gradient force from coupled surface plasmon polariton modes in nanoscale plasmonic waveguides

    Science.gov (United States)

    Lu, Jiahui; Wang, Guanghui

    2016-11-01

    We explore the dispersion properties and optical gradient forces from mutual coupling of surface plasmon polariton (SPP) modes at two interfaces of nanoscale plasmonic waveguides with hyperbolic metamaterial cladding. With Maxwell’s equations and Maxwell stress tensor, we calculate and compare the dispersion relation and optical gradient force for symmetric and antisymmetric SPP modes in two kinds of nanoscale plasmonic waveguides. The numerical results show that the optical gradient force between two coupled hyperbolic metamaterial waveguides can be engineered flexibly by adjusting the waveguide structure parameters. Importantly, an alternative way to boost the optical gradient force is provided through engineering the hyperbolic metamaterial cladding of suitable orientation. These special optical properties will open the door for potential optomechanical applications, such as optical tweezers and actuators. Project supported by the National Natural Science Foundation of China (Grant No. 11474106) and the Natural Science Foundation of Guangdong Province, China (Grant No. 2016A030313439).

  6. Surface structure of polymers and their model compounds observed by atomic force microscopy

    NARCIS (Netherlands)

    Stocker, W.; Bickmann, B.; Magonov, S.N.; Cantow, H.J.; Lotz, B.; Wittmann, J.C.; Moller, M.; Möller, M.

    1992-01-01

    Results of atomic force microscopy (AFM) of normal alkanes, polyethylene, isotactic polypropylene and of a diblock copolymer are presented. Various types of surfaces - naturally and epitaxially grown on different substrates - have been examined from hundreds of nanometers down to the atomic scale.

  7. Theoretical investigation of van der Waals forces between solid surfaces at nanoscales

    NARCIS (Netherlands)

    Kudryavtsev, Y.V.; Gelinck, E.R.M.; Fischer, H.R.

    2009-01-01

    A theoretical investigation of van der Waals forces acting between two solid silicon surfaces at separations from zero to approximately 20 nm is presented. We focused our efforts on the analysis of different factors that can cause deviations from the classical pressure-distance dependence p ∼ 1/D3.

  8. Osteopontin adsorption to Gram-positive cells reduces adhesion forces and attachment to surfaces under flow

    DEFF Research Database (Denmark)

    Kristensen, M F; Zeng, G; Neu, T R

    2017-01-01

    The bovine milk protein osteopontin (OPN) may be an efficient means to prevent bacterial adhesion to dental tissues and control biofilm formation. This study sought to determine to what extent OPN impacts adhesion forces and surface attachment of different bacterial strains involved in dental...

  9. Unraveling protein-protein interactions in clathrin assemblies via atomic force spectroscopy.

    Science.gov (United States)

    Jin, Albert J; Lafer, Eileen M; Peng, Jennifer Q; Smith, Paul D; Nossal, Ralph

    2013-03-01

    Atomic force microscopy (AFM), single molecule force spectroscopy (SMFS), and single particle force spectroscopy (SPFS) are used to characterize intermolecular interactions and domain structures of clathrin triskelia and clathrin-coated vesicles (CCVs). The latter are involved in receptor-mediated endocytosis (RME) and other trafficking pathways. Here, we subject individual triskelia, bovine-brain CCVs, and reconstituted clathrin-AP180 coats to AFM-SMFS and AFM-SPFS pulling experiments and apply novel analytics to extract force-extension relations from very large data sets. The spectroscopic fingerprints of these samples differ markedly, providing important new information about the mechanism of CCV uncoating. For individual triskelia, SMFS reveals a series of events associated with heavy chain alpha-helix hairpin unfolding, as well as cooperative unraveling of several hairpin domains. SPFS of clathrin assemblies exposes weaker clathrin-clathrin interactions that are indicative of inter-leg association essential for RME and intracellular trafficking. Clathrin-AP180 coats are energetically easier to unravel than the coats of CCVs, with a non-trivial dependence on force-loading rate. Published by Elsevier Inc.

  10. Relationship between cloud radiative forcing, cloud fraction and cloud albedo, and new surface-based approach for determining cloud albedo

    OpenAIRE

    Y. Liu; W. Wu; M. P. Jensen; T. Toto

    2011-01-01

    This paper focuses on three interconnected topics: (1) quantitative relationship between surface shortwave cloud radiative forcing, cloud fraction, and cloud albedo; (2) surfaced-based approach for measuring cloud albedo; (3) multiscale (diurnal, annual and inter-annual) variations and covariations of surface shortwave cloud radiative forcing, cloud fraction, and cloud albedo. An analytical expression is first derived to quantify the relationship between cloud radiative forcing, cloud fractio...

  11. Relationship between cloud radiative forcing, cloud fraction and cloud albedo, and new surface-based approach for determining cloud albedo

    OpenAIRE

    Y. Liu; W. Wu; M. P. Jensen; T. Toto

    2011-01-01

    This paper focuses on three interconnected topics: (1) quantitative relationship between surface shortwave cloud radiative forcing, cloud fraction, and cloud albedo; (2) surface-based approach for measuring cloud albedo; (3) multiscale (diurnal, annual and inter-annual) variations and covariations of surface shortwave cloud radiative forcing, cloud fraction, and cloud albedo. An analytical expression is first derived to quantify the relationship between cloud radiative forcing, cloud fraction...

  12. Surface modification of polyacrylonitrile-based carbon fiber and its interaction with imide

    International Nuclear Information System (INIS)

    Xu Bing; Wang Xiaoshu; Lu Yun

    2006-01-01

    In this work, sized polyacrylonitrile (PAN)-based carbon fibers were chemically modified with nitric acid and maleic anhydride (MA) in order to improve the interaction between carbon fiber surface and polyimide matrix. Bismaleimide (BMI) was selected as a model compound of polyimide to react with modified carbon fiber. The surface characteristic changing after modification and surface reaction was investigated by element analysis (EA), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and surface enhanced Raman scattering (SERS). The results indicated that the modification of carbon fiber surface with MA might follow the Diels Alder reaction mechanism. In the surface reaction between modified fibers and BMI, among the various surface functional groups, the hydroxyl group provided from phenolic hydroxyl group and bridged structure on carbon fiber may be the most effective group reacted with imide structure. The results may shed some light on the design of the appropriate surface structure, which could react with polyimide, and the manufacture of the carbon fiber-reinforced polyimide matrix composites

  13. Parabolized Stability Equations analysis of nonlinear interactions with forced eigenmodes to control subsonic jet instabilities

    International Nuclear Information System (INIS)

    Itasse, Maxime; Brazier, Jean-Philippe; Léon, Olivier; Casalis, Grégoire

    2015-01-01

    Nonlinear evolution of disturbances in an axisymmetric, high subsonic, high Reynolds number hot jet with forced eigenmodes is studied using the Parabolized Stability Equations (PSE) approach to understand how modes interact with one another. Both frequency and azimuthal harmonic interactions are analyzed by setting up one or two modes at higher initial amplitudes and various phases. While single mode excitation leads to harmonic growth and jet noise amplification, controlling the evolution of a specific mode has been made possible by forcing two modes (m 1 , n 1 ), (m 2 , n 2 ), such that the difference in azimuth and in frequency matches the desired “target” mode (m 1 − m 2 , n 1 − n 2 ). A careful setup of the initial amplitudes and phases of the forced modes, defined as the “killer” modes, has allowed the minimizing of the initially dominant instability in the near pressure field, as well as its estimated radiated noise with a 15 dB loss. Although an increase of the overall sound pressure has been found in the range of azimuth and frequency analyzed, the present paper reveals the possibility to make the initially dominant instability ineffective acoustically using nonlinear interactions with forced eigenmodes

  14. Parabolized Stability Equations analysis of nonlinear interactions with forced eigenmodes to control subsonic jet instabilities

    Energy Technology Data Exchange (ETDEWEB)

    Itasse, Maxime, E-mail: Maxime.Itasse@onera.fr; Brazier, Jean-Philippe, E-mail: Jean-Philippe.Brazier@onera.fr; Léon, Olivier, E-mail: Olivier.Leon@onera.fr; Casalis, Grégoire, E-mail: Gregoire.Casalis@onera.fr [Onera - The French Aerospace Lab, F-31055 Toulouse (France)

    2015-08-15

    Nonlinear evolution of disturbances in an axisymmetric, high subsonic, high Reynolds number hot jet with forced eigenmodes is studied using the Parabolized Stability Equations (PSE) approach to understand how modes interact with one another. Both frequency and azimuthal harmonic interactions are analyzed by setting up one or two modes at higher initial amplitudes and various phases. While single mode excitation leads to harmonic growth and jet noise amplification, controlling the evolution of a specific mode has been made possible by forcing two modes (m{sub 1}, n{sub 1}), (m{sub 2}, n{sub 2}), such that the difference in azimuth and in frequency matches the desired “target” mode (m{sub 1} − m{sub 2}, n{sub 1} − n{sub 2}). A careful setup of the initial amplitudes and phases of the forced modes, defined as the “killer” modes, has allowed the minimizing of the initially dominant instability in the near pressure field, as well as its estimated radiated noise with a 15 dB loss. Although an increase of the overall sound pressure has been found in the range of azimuth and frequency analyzed, the present paper reveals the possibility to make the initially dominant instability ineffective acoustically using nonlinear interactions with forced eigenmodes.

  15. Computational study on the interactions and orientation of monoclonal human immunoglobulin G on a polystyrene surface

    Directory of Open Access Journals (Sweden)

    Javkhlantugs N

    2013-07-01

    Full Text Available Namsrai Javkhlantugs,1,2 Hexig Bayar,3 Chimed Ganzorig,1 Kazuyoshi Ueda2 1Center for Nanoscience and Nanotechnology and Department of Chemical Technology, School of Chemistry and Chemical Engineering, National University of Mongolia, Ulaanbaatar, Mongolia; 2Department of Advanced Materials Chemistry, Graduate School of Engineering, Yokohama National University, Yokohama, Japan; 3The Key Laboratory of Mammalian Reproductive Biology and Biotechnology of the Ministry of Education, Inner Mongolia University, Hohhot, Inner Mongolia Autonomous Region, People's Republic of China Abstract: Having a theoretical understanding of the orientation of immunoglobulin on an immobilized solid surface is important in biomedical pathogen-detecting systems and cellular analysis. Despite the stable adsorption of immunoglobulin on a polystyrene (PS surface that has been applied in many kinds of immunoassays, there are many uncertainties in antibody-based clinical and biological experimental methods. To understand the binding mechanism and physicochemical interactions between immunoglobulin and the PS surface at the atomic level, we investigated the binding behavior and interactions of the monoclonal immunoglobulin G (IgG on the PS surface using the computational method. In our docking simulation with the different arrangement of translational and rotational orientation of IgG onto the PS surface, three typical orientation patterns of the immunoglobulin G on the PS surface were found. We precisely analyzed these orientation patterns and clarified how the immunoglobulin G interacts with the PS surface at atomic scale in the beginning of the adsorption process. Major driving forces for the adsorption of IgG onto the PS surface come from serine (Ser, aspartic acid (Asp, and glutamic acid (Glu residues. Keywords: bionano interface, immunoassay, polystyrene, IgG, physical adsorption, simulation

  16. Heat transfer tests under forced convection conditions with high wettable heater surface

    Energy Technology Data Exchange (ETDEWEB)

    Mitsutake, Toru; Morooka, Shin-ichi; Miura, Shigeru; Akiba, Miyuki; Sato, Hisaki; Shirakawa, Ken-etsu; Oosato, Tetsuo; Yamamoto, Seiji [Toshiba Co., Kanagawa (Japan)

    2002-07-01

    Under forced convection and atmospheric pressure conditions, heat transfer tests were performed using the annulus channel of a heater rod with highly wettable surface. Improvement of boiling heat transfer requires that the cooling liquid can contact the heating surface, or a high-wettability heating surface, even if a vapor bubble layer is generated on the surface. >From this point of view, high-wettable heating surface was studied. As oxide semiconductor-coated materials are highly-wettable, we made a TiO{sub 2} coated heater rod. TiO{sub 2} coated surface has a high-wettability, in terms of contact angle and Leidenfrost temperature. The boiling curve was measured with and without TiO coated surface. The results showed difference between with and without TiO{sub 2} coating. TiO{sub 2} coating rod showed lower boiling onset heat flux, wider nucleate boiling region and higher critical heat flux than without coating. In summary, high wettablity heater surface produced higher boiling heat transfer characteristics under forced convection conditions. (author)

  17. Interactions between endothelial progenitor cells (EPC) and titanium implant surfaces.

    Science.gov (United States)

    Ziebart, Thomas; Schnell, Anne; Walter, Christian; Kämmerer, Peer W; Pabst, Andreas; Lehmann, Karl M; Ziebart, Johanna; Klein, Marc O; Al-Nawas, Bilal

    2013-01-01

    Endothelial cells play an important role in peri-implant angiogenesis during early bone formation. Therefore, interactions between endothelial progenitor cells (EPCs) and titanium dental implant surfaces are of crucial interest. The aim of our in vitro study was to investigate the reactions of EPCs in contact with different commercially available implant surfaces. EPCs from buffy coats were isolated by Ficoll density gradient separation. After cell differentiation, EPC were cultured for a period of 7 days on different titanium surfaces. The test surfaces varied in roughness and hydrophilicity: acid-etched (A), sand-blasted-blasted and acid-etched (SLA), hydrophilic A (modA), and hydrophilic SLA (modSLA). Plastic and fibronectin-coated plastic surfaces served as controls. Cell numbers and morphology were analyzed by confocal laser scanning microscopy. Secretion of vascular endothelial growth factor (VEGF)-A was measured by enzyme-linked immunosorbent assay and expressions of iNOS and eNOS were investigated by real-time polymerase chain reaction. Cell numbers were higher in the control groups compared to the cells of titanium surfaces. Initially, hydrophilic titanium surfaces (modA and modSLA) showed lower cell numbers than hydrophobic surfaces (A and SLA). After 7 days smoother surfaces (A and modA) showed increased cell numbers compared to rougher surfaces (SLA and modSLA). Cell morphology of A, modA, and control surfaces was characterized by a multitude of pseudopodia and planar cell soma architecture. SLA and modSLA promoted small and plump cell soma with little quantity of pseudopodia. The lowest VEGF level was measured on A, the highest on modSLA. The highest eNOS and iNOS expressions were found on modA surfaces. The results of this study demonstrate that biological behaviors of EPCs can be influenced by different surfaces. The modSLA surface promotes an undifferentiated phenotype of EPCs that has the ability to secrete growth factors in great quantities. In

  18. On the interaction between ocean surface waves and seamounts

    Science.gov (United States)

    Sosa, Jeison; Cavaleri, Luigi; Portilla-Yandún, Jesús

    2017-12-01

    Of the many topographic features, more specifically seamounts, that are ubiquitous in the ocean floor, we focus our attention on those with relatively shallow summits that can interact with wind-generated surface waves. Among these, especially relatively long waves crossing the oceans (swells) and stormy seas are able to affect the water column up to a considerable depth and therefore interact with these deep-sea features. We quantify this interaction through numerical experiments using a numerical wave model (SWAN), in which a simply shaped seamount is exposed to waves of different length. The results show a strong interaction that leads to significant changes in the wave field, creating wake zones and regions of large wave amplification. This is then exemplified in a practical case where we analyze the interaction of more realistic sea conditions with a very shallow rock in the Yellow Sea. Potentially important for navigation and erosion processes, mutatis mutandis, these results are also indicative of possible interactions with emerged islands and sand banks in shelf seas.

  19. Tribochemical interaction between nanoparticles and surfaces of selective layer during chemical mechanical polishing

    Energy Technology Data Exchange (ETDEWEB)

    Ilie, Filip, E-mail: filip@meca.omtr.pub.ro [Polytechnic University of Bucharest, Department of Machine Elements and Tribology (Romania)

    2013-11-15

    Nanoparticles have been widely used in polish slurries such as those in the chemical mechanical polishing (CMP) process. For understanding the mechanisms of CMP, an atomic force microscope (AFM) is used to characterize polished surfaces of selective layers, after a set of polishing experiments. To optimize the CMP polishing process, one needs to get information on the interaction between the nano-abrasive slurry nanoparticles and the surface of selective layer being polished. The slurry used in CMP process of the solid surfaces is slurry with large nanoparticle size colloidal silica sol nano-abrasives. Silica sol nano-abrasives with large nanoparticle are prepared and characterized by transmission electron microscopy, particles colloidal size, and Zeta potential in this paper. The movement of nanoparticles in liquid and the interaction between nanoparticles and solid surfaces coating with selective layer are very important to obtain an atomic alloy smooth surface in the CMP process. We investigate the nanoparticle adhesion and removal processes during CMP and post-CMP cleaning. The mechanical interaction between nanoparticles and the wafer surface was studied using a microcontact wear model. This model considers the nanoparticle effects between the polishing interfaces during load balancing. Experimental results on polishing and cleaning are compared with numerical analysis. This paper suggests that during post-CMP cleaning, a combined effort in chemical and mechanical interaction (tribochemical interactions) would be effective in removal of small nanoparticles during cleaning. For large nanoparticles, more mechanical forces would be more effective. CMP results show that the removal rate has been improved to 367 nm/min and root mean square (RMS) of roughness has been reduced from 4.4 to 0.80 nm. Also, the results show that the silica sol nano-abrasives about 100 nm are of higher stability (Zeta potential is −65 mV) and narrow distribution of nanoparticle

  20. Evaluation of temperature effect on the interaction between β-lactoglobulin and anti-β-lactoglobulin antibody by atomic force microscopy.

    Science.gov (United States)

    Wakayama, Jun'ichi; Sugiyama, Shigeru

    2012-01-10

    Molecular recognition such as antigen-antibody interaction is characterized by the parameters of kinetics and the energy landscape. Examinations of molecules involved in the interaction at different temperatures using atomic force microscopy (AFM) can provide information on not only the effects of temperature on the unbinding force between a molecule of interest and a complementary molecule but also the parameters of kinetics and the energy landscape for dissociation of the molecular complex. We investigated the effect of temperature on the dissociation process of the complex of β-lactoglobulin and anti-bovine β-lactoglobulin IgG polyclonal antibody using AFM. Measurements of the unbinding forces between β-lactoglobulin and the antibody were performed at 25, 35, and 45 °C. The following results were obtained in our present study: (i) The unbinding forces decreased as temperature increased, suggesting that the binding force between β-lactoglobulin and the antibody includes the force originating from temperature-dependent interactions (e.g., hydrogen bonding). (ii) At each temperature, the unbinding force exhibited two linear regimes in the force spectra, indicating that the dissociation process of the β-lactoglobulin-antibody complex passes at least two energy barriers from the bound state to the dissociated state. (iii) The dissociation rates at zero force and the position of energy barriers increased as temperature increased. (iv) The heights of the two energy barriers in the reaction coordinates were 49.7 k(B)T and 14.5 k(B)T. (v) The values of roughness of the barriers were ca. 6.1 k(B)T and 3.2 k(B)T. Overall, the present study using AFM revealed more information about the β-lactoglobulin-antibody interaction than studies using conventional bulk measurement such as surface plasmon resonance.

  1. Why must a solar forcing be larger than a CO2 forcing to cause the same global mean surface temperature change?

    International Nuclear Information System (INIS)

    Modak, Angshuman; Bala, Govindasamy; Cao, Long; Caldeira, Ken

    2016-01-01

    Many previous studies have shown that a solar forcing must be greater than a CO 2 forcing to cause the same global mean surface temperature change but a process-based mechanistic explanation is lacking in the literature. In this study, we investigate the physical mechanisms responsible for the lower efficacy of solar forcing compared to an equivalent CO 2 forcing. Radiative forcing is estimated using the Gregory method that regresses top-of-atmosphere (TOA) radiative flux against the change in global mean surface temperature. For a 2.25% increase in solar irradiance that produces the same long term global mean warming as a doubling of CO 2 concentration, we estimate that the efficacy of solar forcing is ∼80% relative to CO 2 forcing in the NCAR CAM5 climate model. We find that the fast tropospheric cloud adjustments especially over land and stratospheric warming in the first four months cause the slope of the regression between the TOA net radiative fluxes and surface temperature to be steeper in the solar forcing case. This steeper slope indicates a stronger net negative feedback and hence correspondingly a larger solar forcing than CO 2 forcing for the same equilibrium surface warming. Evidence is provided that rapid land surface warming in the first four months sets up a land-sea contrast that markedly affects radiative forcing and the climate feedback parameter over this period. We also confirm the robustness of our results using simulations from the Hadley Centre climate model. Our study has important implications for estimating the magnitude of climate change caused by volcanic eruptions, solar geoengineering and past climate changes caused by change in solar irradiance such as Maunder minimum. (letter)

  2. Irrigation Induced Surface Cooling in the Context of Modern and Increased Greenhouse Gas Forcing

    Science.gov (United States)

    Cook, Benjamin I.; Puma, Michael J.; Krakauer, Nir Y.

    2010-01-01

    There is evidence that expected warming trends from increased greenhouse gas (GHG) forcing have been locally masked by irrigation induced cooling, and it is uncertain how the magnitude of this irrigation masking effect will change in the future. Using an irrigation dataset integrated into a global general circulation model, we investigate the equilibrium magnitude of irrigation induced cooling under modern (Year 2000) and increased (A1B Scenario, Year 2050) GHG forcing, using modern irrigation rates in both scenarios. For the modern scenario, the cooling is largest over North America, India, the Middle East, and East Asia. Under increased GHG forcing, this cooling effect largely disappears over North America, remains relatively unchanged over India, and intensifies over parts of China and the Middle East. For North America, irrigation significantly increases precipitation under modern GHG forcing; this precipitation enhancement largely disappears under A1B forcing, reducing total latent heat fluxes and the overall irrigation cooling effect. Over India, irrigation rates are high enough to keep pace with increased evaporative demand from the increased GHG forcing and the magnitude of the cooling is maintained. Over China, GHG forcing reduces precipitation and shifts the region to a drier evaporative regime, leading to a relatively increased impact of additional water from irrigation on the surface energy balance. Irrigation enhances precipitation in the Middle East under increased GHG forcing, increasing total latent heat fluxes and enhancing the irrigation cooling effect. Ultimately, the extent to which irrigation will continue to compensate for the warming from increased GHG forcing will primarily depend on changes in the background evaporative regime, secondary irrigation effects (e.g. clouds, precipitation), and the ability of societies to maintain (or increase) current irrigation rates.

  3. Interactive system for quick modeling of aircraft surfaces

    Science.gov (United States)

    Mudur, S. P.; Khandekar, Dilip R.

    1990-08-01

    The precise specification of surface geometry of an aircraft is one of the most important and major activities inits design. An initial design, defined by the fundamental requirements, is iteratively analysed and modified till a satisfactory configuration is obtained. Very often in the early stages the need to rapidly make modifications to the geometry for immediate analysis overrides the stringency of smoothness and correctness ofthe surfaces. This paper describes the design of an interactive system which enables the designer to quickly specify the surface geometry and to modify it easily and rapidly. In particular, the software engineering aspects are emphasized. The system uses B-splines for the representation of complex geometry. Surfaces of revolution, required to model certain parts ofthe aircraft, and other simple geometric primitives are also supported. Apart from the usual modeller facilities, features such as camber, twist and form constraints such as tangent or curvature control at a point, etc., are also provided. The system enables easy input and rapid editing of geomeiry through the use of a number of innovative concepts which aim at simplifying and speeding up the man-machine interaction. Multiple window display of entities, augmented by plots of curvature, cross sections etc. provide the visualization tool necessary to assist the designer in decision making.

  4. The esa earth explorer land surface processes and interactions mission

    Science.gov (United States)

    Labandibar, Jean-Yves; Jubineau, Franck; Silvestrin, Pierluigi; Del Bello, Umberto

    2017-11-01

    The European Space Agency (ESA) is defining candidate missions for Earth Observation. In the class of the Earth Explorer missions, dedicated to research and pre-operational demonstration, the Land Surface Processes and Interactions Mission (LSPIM) will acquire the accurate quantitative measurements needed to improve our understanding of the nature and evolution of biosphere-atmosphere interactions and to contribute significantly to a solution of the scaling problems for energy, water and carbon fluxes at the Earth's surface. The mission is intended to provide detailed observations of the surface of the Earth and to collect data related to ecosystem processes and radiation balance. It is also intended to address a range of issues important for environmental monitoring, renewable resources assessment and climate models. The mission involves a dedicated maneuvering satellite which provides multi-directional observations for systematic measurement of Land Surface BRDF (BiDirectional Reflectance Distribution Function) of selected sites on Earth. The satellite carries an optical payload : PRISM (Processes Research by an Imaging Space Mission), a multispectral imager providing reasonably high spatial resolution images (50 m over 50 km swath) in the whole optical spectral domain (from 450 nm to 2.35 μm with a resolution close to 10 nm, and two thermal bands from 8.1 to 9.1 μm). This paper presents the results of the Phase A study awarded by ESA, led by ALCATEL Space Industries and concerning the design of LSPIM.

  5. Bottom boundary layer forced by finite amplitude long and short surface waves motions

    Science.gov (United States)

    Elsafty, H.; Lynett, P.

    2018-04-01

    A multiple-scale perturbation approach is implemented to solve the Navier-Stokes equations while including bottom boundary layer effects under a single wave and under two interacting waves. In this approach, fluid velocities and the pressure field are decomposed into two components: a potential component and a rotational component. In this study, the two components are exist throughout the entire water column and each is scaled with appropriate length and time scales. A one-way coupling between the two components is implemented. The potential component is assumed to be known analytically or numerically a prior, and the rotational component is forced by the potential component. Through order of magnitude analysis, it is found that the leading-order coupling between the two components occurs through the vertical convective acceleration. It is shown that this coupling plays an important role in the bottom boundary layer behavior. Its effect on the results is discussed for different wave-forcing conditions: purely harmonic forcing and impurely harmonic forcing. The approach is then applied to derive the governing equations for the bottom boundary layer developed under two interacting wave motions. Both motions-the shorter and the longer wave-are decomposed into two components, potential and rotational, as it is done in the single wave. Test cases are presented wherein two different wave forcings are simulated: (1) two periodic oscillatory motions and (2) short waves interacting with a solitary wave. The analysis of the two periodic motions indicates that nonlinear effects in the rotational solution may be significant even though nonlinear effects are negligible in the potential forcing. The local differences in the rotational velocity due to the nonlinear vertical convection coupling term are found to be on the order of 30% of the maximum boundary layer velocity for the cases simulated in this paper. This difference is expected to increase with the increase in wave

  6. Interaction between local parameters of two-phase flow and random forces on a cylinder

    International Nuclear Information System (INIS)

    Sylviane Pascal-Ribot; Yves Blanchet; Franck Baj; Phillippe Piteau

    2005-01-01

    Full text of publication follows: In the frame of assessments of steam generator tube bundle vibrations, a study was conducted in order to investigate the effects of an air/water flow on turbulent buffeting forces induced on a cylinder. The main purpose is to relate the physical parameters characterizing an air/water two-phase crossflow with the structural loading of a fixed cylindrical tube. In this first approach, the experiments are carried out in a rectangular acrylic test section supplied with a vertical upward bubbly flow. This flow is transversally impeded by a fixed rigid 12,15 mm diameter cylinder. Different turbulence grids are used in order to modify two-phase characteristics such as bubble diameter, void fraction profile, fluctuation parameters. Preliminarily, a dimensional analysis of fluid-structure interaction under two-phase turbulent solicitations has enabled to identify a list of physically relevant variables which must be measured to evaluate the random forces. The meaning of these relevant parameters as well as the effect of flow patterns are discussed. Direct measurements of two-phase flow parameters are performed simultaneously with measurements of forces exerted on the cylinder. The main descriptive parameters of a two-phase flow are measured using a bi-optical probe, in particular void fraction profiles, interfacial velocities, bubble diameters, void fraction fluctuations. In the same time, the magnitude of random forces caused by two-phase flow is measured with a force transducer. A thorough analysis of the experimental data is then undertaken in order to correlate physical two-phase mechanisms with the random forces exerted on the cylinder. The hypotheses made while applying the dimensional analysis are verified and their pertinence is discussed. Finally, physical parameters involved in random buffeting forces applied on a transverse tube are proposed to scale the spectral magnitude of these forces and comparisons with other authors

  7. Interaction of deuterium plasma with pre-nitrided tungsten surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Liang

    2016-06-15

    DE027289820Nitrogen (N{sub 2}) has been established as an optimal choice as seeding species to control the divertor heat load in ASDEX Upgrade. Based on a series of dedicated laboratory experiments, the present work is devoted to unravel the underlying physics of the interaction of W surfaces with N{sub 2}-seeded plasmas with respect to D retention in W, i.e., to answer ''how should the presence of N in W surfaces affect the hydrogen isotope retention in W after plasma loadings?''. Treated in a well-defined ECR plasma source (PlaQ) in Max-Planck-Institut fuer Plasmaphysik (IPP, Garching), the experiments in this thesis were performed under the following strategy. Namely, the interaction processes between W surfaces with mixed plasma was split into two major steps. Step one is the development and characterization of an appropriate model system for N-containing W layers and step two is the interaction of D plasmas with these model systems. As a first step, a model system for W:N layers formed at W surfaces during or after N{sub 2} seeding in fusion devices is established. By either N implantation into pure W surfaces or sputter-deposition of WN{sub x} films, two different W:N layers were produced. Different characterization techniques, such as XPS, RBS, NRA and TPD, were employed to characterize of these two different W:N layers, i.e., the implantation range of N into W surfaces, the diffusion of N in W, the determination of the N amount and the decomposition temperature of W:N layers. All the results from different techniques were cross-checked with each other, which allowed a reliable N content determination and its evolution during the consecutive D implantations. Based on these characterizations, sputter-deposited WN{sub x} films and N-implanted W surfaces under certain production conditions were selected for further investigation in the following D implantations. The second and main part of the experiments covers the exposure of

  8. Analysis of cutting force signals by wavelet packet transform for surface roughness monitoring in CNC turning

    Science.gov (United States)

    García Plaza, E.; Núñez López, P. J.

    2018-01-01

    On-line monitoring of surface finish in machining processes has proven to be a substantial advancement over traditional post-process quality control techniques by reducing inspection times and costs and by avoiding the manufacture of defective products. This study applied techniques for processing cutting force signals based on the wavelet packet transform (WPT) method for the monitoring of surface finish in computer numerical control (CNC) turning operations. The behaviour of 40 mother wavelets was analysed using three techniques: global packet analysis (G-WPT), and the application of two packet reduction criteria: maximum energy (E-WPT) and maximum entropy (SE-WPT). The optimum signal decomposition level (Lj) was determined to eliminate noise and to obtain information correlated to surface finish. The results obtained with the G-WPT method provided an in-depth analysis of cutting force signals, and frequency ranges and signal characteristics were correlated to surface finish with excellent results in the accuracy and reliability of the predictive models. The radial and tangential cutting force components at low frequency provided most of the information for the monitoring of surface finish. The E-WPT and SE-WPT packet reduction criteria substantially reduced signal processing time, but at the expense of discarding packets with relevant information, which impoverished the results. The G-WPT method was observed to be an ideal procedure for processing cutting force signals applied to the real-time monitoring of surface finish, and was estimated to be highly accurate and reliable at a low analytical-computational cost.

  9. DNA adsorption and desorption on mica surface studied by atomic force microscopy

    International Nuclear Information System (INIS)

    Sun Lanlan; Zhao Dongxu; Zhang Yue; Xu Fugang; Li Zhuang

    2011-01-01

    The adsorption of DNA molecules on mica surface and the following desorption of DNA molecules at ethanol-mica interface were studied using atomic force microscopy. By changing DNA concentration, different morphologies on mica surface have been observed. A very uniform and orderly monolayer of DNA molecules was constructed on the mica surface with a DNA concentration of 30 ng/μL. When the samples were immersed into ethanol for about 15 min, various desorption degree of DNA from mica (0-99%) was achieved. It was found that with the increase of DNA concentration, the desorption degree of DNA from the mica at ethanol-mica interface decreased. And when the uniform and orderly DNA monolayers were formed on the mica surface, almost no DNA molecule desorbed from the mica surface in this process. The results indicated that the uniform and orderly DNA monolayer is one of the most stable DNA structures formed on the mica surface. In addition, we have studied the structure change of DNA molecules after desorbed from the mica surface with atomic force microscopy, and found that the desorption might be ascribed to the ethanol-induced DNA condensation.

  10. Interpreting the probe-surface interaction of surface measuring instruments, or what is a surface?

    Science.gov (United States)

    Leach, Richard; Weckenmann, Albert; Coupland, Jeremy; Hartmann, Wito

    2014-09-01

    When using dimensional measuring instruments it is assumed that there is a property of the object, which we call surface, that is present before during and after the measurement, i.e. the surface is a fundamental property of an object that can, by appropriate means, be used to measure geometry. This paper will attempt to show that the fundamental property ‘surface’ does not exist in any simple form and that all the information we can have about a surface is the measurement data, which will include measurement uncertainty. Measurement data, or what will be referred to as the measured surface, is all that really exists. In this paper the basic physical differences between mechanically, electromagnetically and electrically measured surfaces are highlighted and discussed and accompanied by measurement results on a roughness artefact.

  11. Interpreting the probe-surface interaction of surface measuring instruments, or what is a surface?

    International Nuclear Information System (INIS)

    Leach, Richard; Weckenmann, Albert; Hartmann, Wito; Coupland, Jeremy

    2014-01-01

    When using dimensional measuring instruments it is assumed that there is a property of the object, which we call surface, that is present before during and after the measurement, i.e. the surface is a fundamental property of an object that can, by appropriate means, be used to measure geometry. This paper will attempt to show that the fundamental property ‘surface’ does not exist in any simple form and that all the information we can have about a surface is the measurement data, which will include measurement uncertainty. Measurement data, or what will be referred to as the measured surface, is all that really exists. In this paper the basic physical differences between mechanically, electromagnetically and electrically measured surfaces are highlighted and discussed and accompanied by measurement results on a roughness artefact. (paper)

  12. Measuring the force of single protein molecule detachment from surfaces with AFM.

    Science.gov (United States)

    Tsapikouni, Theodora S; Missirlis, Yannis F

    2010-01-01

    Atomic force microscopy (AFM) was used to measure the non-specific detachment force of single fibrinogen molecules from glass surfaces. The identification of single unbinding events was based on the characteristics of the parabolic curves, recorded during the stretching of protein molecules. Fibrinogen molecules were covalently bound to Si(3)N(4) AFM tips, previously modified with 3-aminopropyl-dimethyl-ethoxysilane, through a homobifunctional poly(ethylene glycol) linker bearing two hydroxysulfosuccinimide esters. The most probable detachment force was found to be 210 pN, when the tip was retracting with a velocity of 1400 nm/s, while the distribution of the detachment distances indicated that the fibrinogen chain can be elongated beyond the length of the physical conformation before detachment. The dependence of the most probable detachment force on the loading rate was examined and the dynamics of fibrinogen binding to the surface were found amenable to the simple expression of the Bell-Evans theory. The theory's expansion, however, by incorporating the concept of the rupture of parallel residue-surface bonds could only describe the detachment of fibrinogen for a small number of such bonds. Finally, the mathematical expression of the Worm-Like Chain model was used to fit the stretching curves before rupture and two interpretations are suggested for the description of the AFM curves with multiple detachment events.

  13. Colloquium: An algebraic model of localized surface plasmons and their interactions

    Science.gov (United States)

    Davis, T. J.; Gómez, D. E.

    2017-01-01

    Although localized surface plasmons in metal nanoparticles can be modeled by Maxwells equations, the difficulty in solving them forces many researchers to use numerical methods. Such methods give accurate results but rarely provide much insight into the complex behaviors of the surface plasmons, nor do they provide a means to choose a configuration of metal nanoparticles to achieve a desired optical response. This Colloquium presents a simple algebraic approach for modeling localized surface plasmons, their excitation by light, and their interactions with one another. Although the method is not numerically accurate it yields useful insight into plasmon behavior and provides a basis for the design of complex plasmonic devices. The approach relies on a description of the surface plasmons in terms of a set of eigenmodes. However, the functional form of these modes is not usually required and the entire problem is reduced to a simple algebra involving the plasmon amplitudes, resonance terms, and their mutual coupling. The algebraic method is derived from an electrostatic formalism, appropriate for near-field interactions at optical frequencies, which is then used to demonstrate a variety of optical effects associated with localized surface plasmons, such as plasmon hybridization, induced transparency, Fano resonances, optical phase detection, and all-optical modulation, among others.

  14. Including Finite Surface Span Effects in Empirical Jet-Surface Interaction Noise Models

    Science.gov (United States)

    Brown, Clifford A.

    2016-01-01

    The effect of finite span on the jet-surface interaction noise source and the jet mixing noise shielding and reflection effects is considered using recently acquired experimental data. First, the experimental setup and resulting data are presented with particular attention to the role of surface span on far-field noise. These effects are then included in existing empirical models that have previously assumed that all surfaces are semi-infinite. This extended abstract briefly describes the experimental setup and data leaving the empirical modeling aspects for the final paper.

  15. Polyphilic Interactions as Structural Driving Force Investigated by Molecular Dynamics Simulation (Project 7

    Directory of Open Access Journals (Sweden)

    Christopher Peschel

    2017-09-01

    Full Text Available We investigated the effect of fluorinated molecules on dipalmitoylphosphatidylcholine (DPPC bilayers by force-field molecular dynamics simulations. In the first step, we developed all-atom force-field parameters for additive molecules in membranes to enable an accurate description of those systems. On the basis of this force field, we performed extensive simulations of various bilayer systems containing different additives. The additive molecules were chosen to be of different size and shape, and they included small molecules such as perfluorinated alcohols, but also more complex molecules. From these simulations, we investigated the structural and dynamic effects of the additives on the membrane properties, as well as the behavior of the additive molecules themselves. Our results are in good agreement with other theoretical and experimental studies, and they contribute to a microscopic understanding of interactions, which might be used to specifically tune membrane properties by additives in the future.

  16. Relation between attractive force and keeper surface characteristics of iron-neodymium-boron magnetic attachment systems.

    Science.gov (United States)

    Ohashi, Norihisa; Koizumi, Hiroyasu; Ishikawa, Yumi; Furuchi, Mika; Matsumura, Hideo; Tanoue, Naomi

    2007-05-01

    The purpose of this study was to evaluate the influence of heating, cast bonding, and subsequent polishing procedures on attractive force of magnetic attachments. Two magnetic attachment systems with keepers of different chemical compositions (Hicorexslim 3013, 447J1; Magfit EX400, AUM20) were employed. Keepers examined were: (1) untreated; (2) heated; (3) cast-bonded with Ag-Pd alloy; (4) cast-bonded with Ag-Pd alloy and polished; (5) cast-bonded with gold alloy; and (6) cast-bonded with gold alloy and polished. Attractive force was determined with a force gauge, and surface structure was evaluated with scanning laser and electron microscopes. Attractive force of the Hicorex system was reduced by cast bonding, whereas that of the Magfit system was reduced by both heating and cast bonding. However, attractive force of both systems was somewhat recovered through the polishing process. Based on the findings of this study, it was suggested that careful polishing after cast bonding was indispensable to the recovery of attractive force for both attachment systems.

  17. Microscopic calculation of the sticking force for nanodrops on an inclined surface

    Science.gov (United States)

    Berim, Gersh O.; Ruckenstein, Eli

    2008-09-01

    A two-dimensional nanodrop on a vertical rough solid surface is examined using a nonlocal density functional theory in the presence of gravity. The roughness is modeled either as a chemical inhomogeneity of the solid or as a result of the decoration with pillars of a smooth homogeneous surface. From the obtained fluid density distribution, the sticking force, which opposes the drop motion along an inclined surface, and the contact angles on the lower and upper leading edges of the drop are calculated. On the basis of these results, it is shown that the macroscopically derived equation for a drop in equilibrium on an inclined surface is also applicable to nanodrops. The liquid-vapor surface tension involved in this equation was calculated for various specific cases, and the values obtained are of the same order of magnitude as those obtained in macroscopic experiments.

  18. Foreword: In situ gas surface interactions: approaching realistic conditions

    Science.gov (United States)

    Lundgren, Edvin; Over, Herbert

    2008-03-01

    This special issue is devoted to the application of in situ surface-sensitive techniques in the elucidation of catalysed reactions at (model) catalyst surfaces. Both reaction intermediates and the nature of the catalytically active phase are the targets of these investigations. In situ surface science techniques are also used to study the interaction of water with surfaces under realistic conditions. Since 80% of all technical chemicals are manufactured by utilizing (heterogeneous) catalysis, scientific understanding and technological development of catalysis are of central practical importance in modern society [1]. Heterogeneously catalysed reactions take place at the gas/solid interface. Therefore one of the major topics in surface chemistry and physics is closely related to heterogeneous catalysis, with the aim of developing novel catalysts and to improve catalysts' performances on the basis of atomic scale based knowledge. Despite the economical and environmental rewards—if such a goal is achieved—and despite 40 years of intensive research, practical catalysis is still safely in a black box: the reactivity and selectivity of a catalyst are commercially still optimized on a trial and error basis, applying the high throughput screening approach. The reason for this discrepancy between ambition and reality lies in the inherent complexity of the catalytic system, consisting of the working catalyst and the interaction of the catalyst with the reactant mixture. Practical (solid) catalysts consist of metal or oxide nanoparticles which are dispersed and stabilized on a support and which may be promoted by means of additives. These particles catalyse a reaction in pressures as high as 100 bar. Practical catalysis is in general considered to be far too complex for gaining atomic-scale understanding of the mechanism of the catalysed reaction of an industrial catalyst during its operation. Therefore it has been necessary to introduce idealization and simplification of

  19. Interactive Multimedia Software on Fundamental Particles and Forces. Final Technical Report

    International Nuclear Information System (INIS)

    Jack Sculley

    1999-01-01

    Research in the SBIR Phase 2 grant number 95 ER 81944 centered on creating interactive multimedia software for teaching basic concepts in particle physics on fundamental particles and forces. The work was undertaken from February 1997 through July 1998. Overall the project has produced some very encouraging results in terms of product development, interest from the general public and interest from potential Phase 3 funders. Although the original Phase 3 publisher, McGraw Hill Home Interactive, was dissolved by its parent company, and other changes in the CD-ROM industry forced them to change their focus from CD-ROM to the Internet, there has been substantial interest from software publishers and online content providers in the content developed in the course of the Phase 2 research. Results are summarized

  20. Gauge unification of basic forces particularly of gravitation with strong interactions

    International Nuclear Information System (INIS)

    Salam, A.

    1977-01-01

    Corresponding to the two known types of gauge theories, Yang-Mills with spin-one mediating particles and Einstein Weyl with spin-two mediating particles, it is speculated that two distinct gauge unifications of the basic forces appear to be taking place. One is the familiar Yang-Mills unification of weak and electromagnetic forces with the strong. The second is the less familiar gauge unification of gravitation with spin-two tensor-dominated aspects of strong interactions. It is proposed that there are strongly interacting spin-two strong gravitons obeying Einstein's equations, and their existence gives a clue to an understanding of the (partial) confinement of quarks, as well as of the concept of hadronic temperature, through the use of Schwarzschild de-Sitter-like partially confining solitonic solutions of the strong gravity Einstein equation

  1. Surface modification of hydrophobic polymers for improvement of endothelial cell-surface interactions

    NARCIS (Netherlands)

    Dekker, A.; Dekker, A.; Reitsma, K.; Beugeling, T.; Beugeling, T.; Bantjes, A.; Bantjes, A.; Feijen, Jan; Kirkpatrick, C.J.; van Aken, W.G.

    1992-01-01

    The aim of this study is to improve the interaction of endothelial cells with polymers used in vascular prostheses. Polytetrafluoroethylene (PTFE; Teflon) films were treated by means of nitrogen and oxygen plasmas. Depending on the plasma exposure time, modified PTFE surfaces showed water-contact

  2. Atomic Force Microscopy Study of the Interactions of Indolicidin with Model Membranes and DNA.

    Science.gov (United States)

    Fojan, Peter; Gurevich, Leonid

    2017-01-01

    The cell membrane is the first barrier and quite often the primary target that antimicrobial peptides (AMPs) have to destroy or penetrate to fulfill their mission. Upon penetrating through the membrane, the peptides can further attack intracellular targets, in particular DNA. Studying the interaction of an antimicrobial peptide with a cell membrane and DNA holds keys to understanding its killing mechanisms. Commonly, these interactions are studied by using optical or scanning electron microscopy and appropriately labeled peptides. However, labeling can significantly affect the hydrophobicity, conformation, and size of the peptide, hence altering the interaction significantly. Here, we describe the use of atomic force microscopy (AFM) for a label-free study of the interactions of peptides with model membranes under physiological conditions and DNA as a possible intracellular target.

  3. Analytical modeling of soliton interactions in a nonlocal nonlinear medium analogous to gravitational force

    Science.gov (United States)

    Zeng, Shihao; Chen, Manna; Zhang, Ting; Hu, Wei; Guo, Qi; Lu, Daquan

    2018-01-01

    We illuminate an analytical model of soliton interactions in lead glass by analogizing to a gravitational force system. The orbits of spiraling solitons under a long-range interaction are given explicitly and demonstrated to follow Newton's second law of motion and the Binet equation by numerical simulations. The condition for circular orbits is obtained and the oscillating orbits are proved not to be closed. We prove the analogy between the nonlocal nonlinear optical system and gravitational system and specify the quantitative relation of the quantity between the two models.

  4. Measurements on hydrophobic and hydrophilic surfaces using a porous gamma alumina nanoparticle aggregate mounted on Atomic Force Microscopy cantilevers

    NARCIS (Netherlands)

    Das, Theerthankar; Becker, Thomas; Nair, Balagopal N.

    2010-01-01

    Atomic Force Microscopy (AFM) measurements are extensively used for a detailed understanding of molecular and surface forces. In this study, we present a technique for measuring such forces, using an AFM cantilever attached with a porous gamma alumina nanoparticle aggregate. The modified cantilever

  5. Machining of bone: Analysis of cutting force and surface roughness by turning process.

    Science.gov (United States)

    Noordin, M Y; Jiawkok, N; Ndaruhadi, P Y M W; Kurniawan, D

    2015-11-01

    There are millions of orthopedic surgeries and dental implantation procedures performed every year globally. Most of them involve machining of bones and cartilage. However, theoretical and analytical study on bone machining is lagging behind its practice and implementation. This study views bone machining as a machining process with bovine bone as the workpiece material. Turning process which makes the basis of the actually used drilling process was experimented. The focus is on evaluating the effects of three machining parameters, that is, cutting speed, feed, and depth of cut, to machining responses, that is, cutting forces and surface roughness resulted by the turning process. Response surface methodology was used to quantify the relation between the machining parameters and the machining responses. The turning process was done at various cutting speeds (29-156 m/min), depths of cut (0.03 -0.37 mm), and feeds (0.023-0.11 mm/rev). Empirical models of the resulted cutting force and surface roughness as the functions of cutting speed, depth of cut, and feed were developed. Observation using the developed empirical models found that within the range of machining parameters evaluated, the most influential machining parameter to the cutting force is depth of cut, followed by feed and cutting speed. The lowest cutting force was obtained at the lowest cutting speed, lowest depth of cut, and highest feed setting. For surface roughness, feed is the most significant machining condition, followed by cutting speed, and with depth of cut showed no effect. The finest surface finish was obtained at the lowest cutting speed and feed setting. © IMechE 2015.

  6. Plasma surface interactions in Q-enhanced mirror systems

    International Nuclear Information System (INIS)

    Post, R.F.

    1978-01-01

    Two approaches to enhancement of the Q (energy gain) factor of mirror systems are under study at Livermore. These include the Tandem Mirror and the Field Reversed Mirror. Both of these new ideas preserve features of conventional mirror systems as far as plasma-wall interactions are concerned. Specifically in both approaches field lines exit from the ends of the system and impinge on walls located at a distance from the confinement chamber. It is possible to predict some aspects of the plasma/surface interactions of TM and FRM systems from experience obtained in the Livermore 2XIIB experiment. In particular, as observed in 2XIIB, effective isolation of the plasma from thermal contact with the ends owing to the development of sheath-like regions is to be expected. Studies presently underway directed toward still further enhancing the decoupling of the plasma from the effects of plasma surface interactions at the walls will be discussed, with particular reference to the problem of minimizing the effects of refluxing secondary electrons produced by plasma impact on the end walls

  7. Simplified TiO2 force fields for studies of its interaction with biomolecules

    Science.gov (United States)

    Luan, Binquan; Huynh, Tien; Zhou, Ruhong

    2015-06-01

    Engineered TiO2 nanoparticles have been routinely applied in nanotechnology, as well as in cosmetics and food industries. Despite active experimental studies intended to clarify TiO2's biological effects, including potential toxicity, the relation between experimentally inferred nanotoxicity and industry standards for safely applying nanoparticles remains somewhat ambiguous with justified concerns. Supplemental to experiments, molecular dynamics simulations have proven to be efficacious in investigating the molecular mechanism of a biological process occurring at nanoscale. In this article, to facilitate the nanotoxicity and nanomedicine research related to this important metal oxide, we provide a simplified force field, based on the original Matsui-Akaogi force field but compatible to the Lennard-Jones potentials normally used in modeling biomolecules, for simulating TiO2 nanoparticles interacting with biomolecules. The force field parameters were tested in simulating the bulk structure of TiO2, TiO2 nanoparticle-water interaction, as well as the adsorption of proteins on the TiO2 nanoparticle. We demonstrate that these simulation results are consistent with experimental data/observations. We expect that simulations will help to better understand the interaction between TiO2 and molecules.

  8. Three-dimensional hydration layer mapping on the (10.4) surface of calcite using amplitude modulation atomic force microscopy

    International Nuclear Information System (INIS)

    Marutschke, Christoph; Hermes, Ilka; Bechstein, Ralf; Kühnle, Angelika; Walters, Deron; Cleveland, Jason

    2014-01-01

    Calcite, the most stable modification of calcium carbonate, is a major mineral in nature. It is, therefore, highly relevant in a broad range of fields such as biomineralization, sea water desalination and oil production. Knowledge of the surface structure and reactivity of the most stable cleavage plane, calcite (10.4), is pivotal for understanding the role of calcite in these diverse areas. Given the fact that most biological processes and technical applications take place in an aqueous environment, perhaps the most basic—yet decisive—question addresses the interaction of water molecules with the calcite (10.4) surface. In this work, amplitude modulation atomic force microscopy is used for three-dimensional (3D) mapping of the surface structure and the hydration layers above the surface. An easy-to-use scanning protocol is implemented for collecting reliable 3D data. We carefully discuss a comprehensible criterion for identifying the solid–liquid interface within our data. In our data three hydration layers form a characteristic pattern that is commensurate with the underlying calcite surface. (paper)

  9. Spectral studies of Lanthanide interactions with membrane surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Karukstis, K.K.; Kao, M.Y.; Savin, D.A.; Bittker, R.A.; Kaphengst, K.J.; Emetarom, C.M.; Naito, N.R.; Takamoto, D.Y. [Harvey Mudd College, Claremont, CA (United States)

    1995-03-23

    We have monitored the interactions of the series of trivalent lanthanide cations with the thylakoid membrane surface of spinach chloroplasts using two complementary spectral techniques. Measurements of the fluorescence emission of the extrinsic probe 2-p-toluidinonaphthalene-6-sulfonate (TNS) and the absorbance of the intrinsic chromophore chlorophyll provide two sensitive means of characterizing the dependence of the cation-membrane interaction on the nature of the cation. In these systems, added lanthanide cations adsorb onto the membrane surface to neutralize exposed segments of membrane-embedded protein complexes. The lanthanide-induced charge neutralization increases the proximity of added TNS anion to the membrane surface as evidenced by variations in the TNS fluorescence level and wavelength of maximum emission. Our results reveal a strong dependence of TNS fluorescence parameters on both lanthanide size and total orbital angular momentum L value. Lanthanides with greater charge density (small size and/or low L value) enhance the TNS fluorescence level to a greater extent. A possible origin for the lanthanide-dependent TNS fluorescence levels is suggested in terms of a heterogeneity in the number and type of TNS binding sites. The data are consistent with the proposal that larger lanthanides with smaller enthalpies of hydration induce more significant membrane appression. 59 refs., 9 figs., 2 tabs.

  10. The interaction of carbon monoxide with model astrophysical surfaces.

    Science.gov (United States)

    Collings, Mark P; Dever, John W; McCoustra, Martin R S

    2014-02-28

    Carbon monoxide (CO) is an important component of the icy mantles that accrete on interstellar dust grains. To develop a better understanding of the physicochemical basis of its infrared spectroscopy, we have studied the interaction of submonolayer coverages of CO with the surface of films of other astrophysically relevant species--(13)CO, carbon dioxide (CO2), ammonia (NH3), methanol (CH3OH) and water (H2O)--under ultrahigh vacuum and cryogenic (10 K) conditions using reflection-absorption infrared spectroscopy (RAIRS). In support of these measurements, we have performed ab initio calculations of gas phase dimer complexes, and made comparisons to experimental results of gas phase and matrix isolated complexes, which are extensively reported in the literature. The interaction of CO can be categorised as occurring via the C atom (C(CO) bonded), the O atom (O(CO) bonded) or in a π-bonded configuration. The C(CO) configuration is characterised by a blue shifted C≡O stretch frequency, and is observed for CO adsorbed on (13)CO, CO2 and H2O surfaces. From the absence of such a feature from the spectra of CO adsorbed on CH3OH it can be concluded that the dangling OH bonds required for this adsorption configuration are not present at the surface of the CH3OH film.

  11. Effective Electrostatic Interactions Between Two Overall Neutral Surfaces with Quenched Charge Heterogeneity Over Atomic Length Scale

    Science.gov (United States)

    Zhou, S.

    2017-12-01

    Using Monte Carlo results as a reference, a classical density functional theory ( CDFT) is shown to reliably predict the forces between two heterogeneously charged surfaces immersed in an electrolyte solution, whereas the Poisson-Boltzmann ( PB) theory is demonstrated to deteriorate obviously for the same system even if the system parameters considered fall within the validity range of the PB theory in the homogeneously charged surfaces. By applying the tested CDFT, we study the effective electrostatic potential of mean force ( EPMF) between two face-face planar and hard surfaces of zero net charge on which positive and negative charges are separated and considered to present as discontinuous spots on the inside edges of the two surfaces. Main conclusions are summarized as follows: (i) strength of the EPMF in the surface charge separation case is very sensitively and positively correlated with the surface charge separation level and valency of the salt ion. Particularly, the charge separation level and the salt ion valency have a synergistic effect, which makes high limit of the EPMF strength in the surface charge separation case significantly go beyond that of the ideal homogeneously charged surface counterpart at average surface charge density similar to the average surface positive or negative charge density in the charge separation case. (ii) The surface charge distribution patterns mainly influence sign of the EPMF: symmetrical and asymmetrical patterns induce repulsive and attractive (at small distances) EPMF, respectively; but with low valency salt ions and low charge separation level the opposite may be the case. With simultaneous presence of both higher valency cation and anion, the EPMF can be repulsive at intermediate distances for asymmetrical patterns. (iii) Salt ion size has a significant impact, which makes the EPMF tend to become more and more repulsive with the ion diameter regardless of the surface charge distribution patterns and the valency of

  12. INVESTIGATION OF POLYMER SURFACES USING SCANNING FORCE MICROSCOPY (SFM) - A NEW DIRECT LOOK ON OLD POLYMER PROBLEMS

    NARCIS (Netherlands)

    GRIM, PCM; BROUWER, HJ; SEYGER, RM; OOSTERGETEL, GT; BERGSMASCHUTTER, WG; ARNBERG, AC; GUTHNER, P; DRANSFELD, K; HADZIIOANNOU, G

    In this contribution, the general concepts of force microscopy will be presented together with its application to polymer surfaces (Ref.1). Several examples will be presented to illustrate that force microscopy is a powerful and promising tool for investigation of (polymer) surfaces, such as the

  13. Cell/surface interactions on laser micro-textured titanium-coated silicon surfaces.

    Science.gov (United States)

    Mwenifumbo, Steven; Li, Mingwei; Chen, Jianbo; Beye, Aboubaker; Soboyejo, Wolé

    2007-01-01

    This paper examines the effects of nano-scale titanium coatings, and micro-groove/micro-grid patterns on cell/surface interactions on silicon surfaces. The nature of the cellular attachment and adhesion to the coated/uncoated micro-textured surfaces was elucidated by the visualization of the cells and relevant cytoskeletal & focal adhesion proteins through scanning electron microscopy and immunofluorescence staining. Increased cell spreading and proliferation rates are observed on surfaces with 50 nm thick Ti coatings. The micro-groove geometries have been shown to promote contact guidance, which leads to reduced scar tissue formation. In contrast, smooth surfaces result in random cell orientations and the increased possibility of scar tissue formation. Immunofluorescence cell staining experiments also reveal that the actin stress fibers are aligned along the groove dimensions, with discrete focal adhesions occurring along the ridges, within the grooves and at the ends of the cell extensions. The implications of the observed cell/surface interactions are discussed for possible applications of silicon in implantable biomedical systems.

  14. Cell-surface interactions involving immobilized magnetite nanoparticles on flat magnetic substrates.

    Science.gov (United States)

    Loichen, Juliane; Hartmann, Uwe

    2009-09-01

    A new method to affect cells by cell-surface interaction is introduced. Biocompatible magnetic nanobeads are deposited onto a biocompatible magnetic thin layer. The particles are composed of small magnetite crystals embedded in a matrix which can be functionalized by different molecules, proteins or growth factors. The magnetic interaction between surface and beads prevents endocytosis if the setup is utilized for cell culturing. The force acting between particles and magnetic layer is calculated by a magnetostatic approach. Biocompatibility is ensured by using garnet layers which turned out to be nontoxic and stable under culturing conditions. The garnet thin films exhibit spatially and temporally variable magnetic domain configurations in changing external magnetic fields and depending on their thermal pretreatment. Several patterns and bead deposition methods as well as the cell-surface interactions were analyzed. In some cases the cells show directed growth. Theoretical considerations explaining particular cell behavior on this magnetic material involve calculations of cell growth on elastic substrates and bending of cell membranes.

  15. Surface Interaction of Nanoscale Water Film with SDS from Computational Simulation and Film Thermodynamics

    Directory of Open Access Journals (Sweden)

    Tiefeng Peng

    2017-11-01

    Full Text Available Foam systems have been attracting extensive attention due to their importance in a variety of applications, e.g., in the cleaning industry, and in bubble flotation. In the context of flotation chemistry, flotation performance is strongly affected by bubble coalescence, which in turn relies significantly on the surface forces upon the liquid film between bubbles. Conventionally, unusual short-range strongly repulsive surface interactions for Newton black films (NBF between two interfaces with thickness of less than 5 nm were not able to be incorporated into the available classical Derjaguin, Landau, Verwey, and Overbeek (DLVO theory. The non-DLVO interaction would increase exponentially with the decrease of film thickness, as it plays a crucial role in determining liquid film stability. However, its mechanism and origin are still unclear. In the present work, we investigate the surface interaction of free-standing sodium dodecyl-sulfate (SDS nanoscale black films in terms of disjoining pressure using the molecular simulation method. The aqueous nanoscale film, consisting of a water coating with SDS surfactants, and with disjoining pressure and film tension of SDS-NBF as a function of film thickness, were quantitatively determined by a post-processing technique derived from film thermodynamics.

  16. Topography and Mechanical Property Mapping of International Simple Glass Surfaces with Atomic Force Microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Pierce, Eric M [ORNL

    2014-01-01

    Quantitative Nanomechanical Peak Force (PF-QNM) TappingModeTM atomic force microscopy measurements are presented for the first time on polished glass surfaces. The PF-QNM technique allows for topography and mechanical property information to be measured simultaneously at each pixel. Results for the international simple glass which represents a simplified version of SON68 glass suggests an average Young s modulus of 78.8 15.1 GPa is within the experimental error of the modulus measured for SON68 glass (83.6 2 GPa) with conventional approaches. Application of the PF-QNM technique will be extended to in situ glass corrosion experiments with the goal of gaining atomic-scale insights into altered layer development by exploiting the mechanical property differences that exist between silica gel (e.g., altered layer) and pristine glass surface.

  17. Potential dependent adhesion forces on bare and underpotential deposition modified electrode surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Serafin, J.M.; Hsieh, S.J.; Monahan, J.; Gewirth, A.A. [Univ. of Illinois, Urbana, IL (United States)

    1998-12-03

    Adhesion force measurements are used to determine the potential dependence of the force of adhesion between a Si{sub 3}N{sub 4} cantilever and a Au(111) surface modified by the underpotential deposition (upd) of Bi or Cu in acid solution or by oxide formation. The measured work of adhesion is near zero for most of the potential region examined in Bi upd but rises after the formation of a full Bi monolayer. The work of adhesion is high at positive potentials for Cu upd but then decreases as the Cu partial and full monolayers are formed. The work of adhesion is low in the oxide region on Au(111) but rises following the sulfate disordering transition at 1.1 V vs NHE. These results are interpreted in terms of the degree of solvent order on the electrode surface.

  18. Dynamical image potential and induced forces for charged particles moving parallel to a solid surface

    International Nuclear Information System (INIS)

    Arista, N.R.

    1994-01-01

    The dynamical image potential and ensuing forces induced by a charged particle moving parallel to a solid surface are investigated by using a dielectric formulation for semi-infinite dispersive media. The adiabatic behavior of the field in the asymptotic range is discussed in a general way using a multipole expansion. Several calculations illustrate the behavior of the field using both a simple model, where the surface response is approximated by a single plasma resonance, and a more realistic representation of the medium based upon the empirical information on the optical constants for various solids (Al, Cu, Ag, and Au). The model parameters may be adjusted to provide very good agreement with the optical-data integrations of the stopping and lateral forces on the moving charge. On the other hand, important differences in the description of the wake potential using either the simple plasma resonance model, or the optical-data representation, are obtained for Cu, Ag, and Au

  19. Non-additivity of molecule-surface van der Waals potentials from force measurements

    Science.gov (United States)

    Wagner, Christian; Fournier, Norman; Ruiz, Victor G.; Li, Chen; Müllen, Klaus; Rohlfing, Michael; Tkatchenko, Alexandre; Temirov, Ruslan; Tautz, F. Stefan

    2014-11-01

    Van der Waals (vdW) forces act ubiquitously in condensed matter. Despite being weak on an atomic level, they substantially influence molecular and biological systems due to their long range and system-size scaling. The difficulty to isolate and measure vdW forces on a single-molecule level causes our present understanding to be strongly theory based. Here we show measurements of the attractive potential between differently sized organic molecules and a metal surface using an atomic force microscope. Our choice of molecules and the large molecule-surface separation cause this attraction to be purely of vdW type. The experiment allows testing the asymptotic vdW force law and its validity range. We find a superlinear growth of the vdW attraction with molecular size, originating from the increased deconfinement of electrons in the molecules. Because such non-additive vdW contributions are not accounted for in most first-principles or empirical calculations, we suggest further development in that direction.

  20. Non-additivity of molecule-surface van der Waals potentials from force measurements.

    Science.gov (United States)

    Wagner, Christian; Fournier, Norman; Ruiz, Victor G; Li, Chen; Müllen, Klaus; Rohlfing, Michael; Tkatchenko, Alexandre; Temirov, Ruslan; Tautz, F Stefan

    2014-11-26

    Van der Waals (vdW) forces act ubiquitously in condensed matter. Despite being weak on an atomic level, they substantially influence molecular and biological systems due to their long range and system-size scaling. The difficulty to isolate and measure vdW forces on a single-molecule level causes our present understanding to be strongly theory based. Here we show measurements of the attractive potential between differently sized organic molecules and a metal surface using an atomic force microscope. Our choice of molecules and the large molecule-surface separation cause this attraction to be purely of vdW type. The experiment allows testing the asymptotic vdW force law and its validity range. We find a superlinear growth of the vdW attraction with molecular size, originating from the increased deconfinement of electrons in the molecules. Because such non-additive vdW contributions are not accounted for in most first-principles or empirical calculations, we suggest further development in that direction.

  1. On electrostatic and Casimir force measurements between conducting surfaces in a sphere-plane configuration

    International Nuclear Information System (INIS)

    Kim, W J; Brown-Hayes, M; Brownell, J H; Dalvit, D A R; Onofrio, R

    2009-01-01

    We report on measurements of forces acting between two conducting surfaces in a spherical-plane configuration in the 35 nm-1 μm separation range. The measurements are obtained by performing electrostatic calibrations followed by a residuals analysis after subtracting the electrostatic-dependent component. We find in all runs optimal fitting of the calibrations for exponents smaller than the one predicted by electrostatics for an ideal sphere-plane geometry. We also find that the external bias potential necessary to minimize the electrostatic contribution depends on the sphere-plane distance. In spite of these anomalies, by implementing a parametrization-dependent subtraction of the electrostatic contribution we have found evidence for short-distance attractive forces of magnitude comparable to the expected Casimir-Lifshitz force. We finally discuss the relevance of our findings in the more general context of Casimir-Lifshitz force measurements, with particular regard to the critical issues of the electrical and geometrical characterization of the involved surfaces.

  2. Interaction of stress and phase transformations during thermochemical surface engineering

    DEFF Research Database (Denmark)

    Jespersen, Freja Nygaard

    dissolution. The present project is devoted to understanding the mutual interaction of stresses and phase transformations during thermochemical surface engineering by combining numerical modelling with experimental materials science. The modelling was done by combining solid mechanics with thermodynamics...... by chromium atoms, and the effect of composition-induced stress on surface concentration and diffusive flux. The effect of plasticity was also included. Temperature and concentration dependencies of mechanical and diffusion material properties were studied, and the effect of incorporation in the model...... examined. The effect of pre-stressing the sample was also tested, to investigate the effects of a residual stress-state that might be present from processing of the metal specimen. Controlled thermochemical treatment of austenitic stainless steel was investigated experimentally by in-diffusion of nitrogen...

  3. Scattering function for a model of interacting surfaces

    International Nuclear Information System (INIS)

    Colangelo, P.; Gonnella, G.; Maritan, A.

    1993-01-01

    The two-point correlation function of an ensemble of interacting closed self-avoiding surfaces on a cubic lattice is analyzed in the disordered phase, which corresponds to the paramagnetic region in a related spin formulation. Mean-field theory and Monte Carlo simulations predict the existence of a disorder line which corresponds to a transition from an exponential decay to an oscillatory damped behavior of the two-point correlation function. The relevance of the results for the description of amphiphilic systems in a microemulsion phase is discussed. The scattering function is also calculated for a bicontinuous phase coexisting with the paramagnetic phase

  4. Surface water - groundwater interactions at different spatial and temporal scales

    DEFF Research Database (Denmark)

    Sebök, Éva

    As there is a growing demand for the protection and optimal management of both the surface water and groundwater resources, the understanding of their exchange processes is of great importance. This PhD study aimed at describing the natural spatial and temporal variability of these interactions...... detected large spatial variability in SWI temperatures with scattered high-discharge sites in a stream and also in a lake where discharge fluxes were estimated by vertical temperature profiles and seepage meter measurements. On the kilometre scale DTS indicated less spatial variability in streambed...

  5. Nuclear Fusion Research Understanding Plasma-Surface Interactions

    CERN Document Server

    Clark, Robert E.H

    2005-01-01

    It became clear in the early days of fusion research that the effects of the containment vessel (erosion of "impurities") degrade the overall fusion plasma performance. Progress in controlled nuclear fusion research over the last decade has led to magnetically confined plasmas that, in turn, are sufficiently powerful to damage the vessel structures over its lifetime. This book reviews current understanding and concepts to deal with this remaining critical design issue for fusion reactors. It reviews both progress and open questions, largely in terms of available and sought-after plasma-surface interaction data and atomic/molecular data related to these "plasma edge" issues.

  6. Colloid transport with wetting fronts: interactive effects of solution surface tension and ionic strength.

    Science.gov (United States)

    Zhuang, Jie; Goeppert, Nadine; Tu, Ching; McCarthy, John; Perfect, Edmund; McKay, Larry

    2010-02-01

    Transport of colloids with transient wetting fronts represents an important mechanism of contaminant migration in the vadose zone. The work presented here used steady-state saturated and transient unsaturated flow columns to evaluate the transport of a fluorescent latex microsphere (980 nm in diameter) with capillary wetting fronts of different solution surface tensions and ionic strengths. The saturated transport experiments demonstrated that decreasing solution surface tension and ionic strength decreased colloid deposition at the solid-liquid interface and increased colloid recovery in the column effluent. The effect of solution surface tension on colloid transport and deposition was greater at lower ionic strength, suggesting an interaction between these two factors. Under transient unsaturated flow conditions, the number of colloids retained in sand decreased exponentially with travel distance through the porous media. However, lowering the solution surface tension and ionic strength resulted in a more even distribution of colloids along the column. The measured zeta potentials of colloids in different solutions suggest that both lowering surface tension and ionic strength would enhance the electrostatic repulsion between colloid and sand. The experimental results revealed that the effects are nonlinear, implying the possible existence of critical threshold values, beyond which the effects were not significant. In addition, colloid migration slowed down as solution surface tension decreased due to reduction of capillary forces that drove liquid movement. Copyright 2009 Elsevier Ltd. All rights reserved.

  7. Interaction of slow highly charged ions with surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Aumayr, F. [Technische Universitaet Wien (Austria)

    1994-12-31

    A review will be presented on recent investigations concerning the interaction of slow ({le} 10{sup 6} m/s) ions in high charge states approaching a clean metal surface. Detailed information on the generation and decay of transiently formed multiply excited {open_quotes}hollow atoms{close_quotes} can be gained from the measurement of total yields and energy distributions of emitted electrons and, in particular, from the electron emission statistics. By comparing measured results with model calculations based on a recently extended classical over-barrier approach, different sources for the observed electron emission can be identified: autoionisation of the multiply excited hollow atoms on their way toward the surface; promotion above the vacuum barrier of electrons previously captured by the projectile, due to their self- and image-charge screening near the surface; `peeling-off` of electrons still bound in highly excited projectile states at the moment of surface impact, and finally; electron emission due to final subsurface de-excitation.

  8. Atomic force microscopy of surface topography of nitrogen plasma treated steel

    CERN Document Server

    Mahboubi, F

    2002-01-01

    Nitriding of steels, using plasma environments has been practiced for many years. A lot of efforts have been put on developing new methods, such as plasma immersion ion implantation (Pl sup 3) and radio frequency (RF) plasma nitriding, for mass transfer of nitrogen into the surface of the work piece. This article presents the results obtained from an in depth investigation of the surface morphology of the treated samples, carried out using an atomic force microscope. Samples from a microalloyed steel, were treated by both methods for 5 hours at different temperatures ranging from 350 to 550 sup d eg sup C in 75% N sub 2 -25% H sub 2 atmosphere. It has been found that the surface of the samples treated by PI sup 3 technique, although having more favorable properties, were rougher than the surfaces treated by RF plasma nitriding.

  9. Surface tension effect on the mechanical properties of nanomaterials measured by atomic force microscopy

    Science.gov (United States)

    Cuenot, Stéphane; Frétigny, Christian; Demoustier-Champagne, Sophie; Nysten, Bernard

    2004-04-01

    The effect of reduced size on the elastic properties measured on silver and lead nanowires and on polypyrrole nanotubes with an outer diameter ranging between 30 and 250 nm is presented and discussed. Resonant-contact atomic force microscopy (AFM) is used to measure their apparent elastic modulus. The measured modulus of the nanomaterials with smaller diameters is significantly higher than that of the larger ones. The latter is comparable to the macroscopic modulus of the materials. The increase of the apparent elastic modulus for the smaller diameters is attributed to surface tension effects. The surface tension of the probed material may be experimentally determined from these AFM measurements.

  10. Spot Surface Labeling of Magnetic Microbeads and Application in Biological Force Measurements

    Science.gov (United States)

    Estes, Ashley; O'Brien, E. Tim; Hill, David; Superfine, Richard

    2006-11-01

    Biological force measurements on single molecules and macromolecular structures often use microbeads for the application of force. These techniques are often complicated by multiple attachments and nonspecific binding. In one set of experiments, we are applying a magnetic force microscope that allows us to pull on magnetic beads attached to ciliated human bronchial epithelial cells. These experiments provide a means to measure the stall force of cilia and understand how cilia propel fluids. However, because we are using beads with diameters of one and 2.8 microns, and the diameter of human airway cilia is approximately 200 nm, we cannot be assured that the bead is bound to a single cilium. To address this, we have developed a sputter coating technique to block the biotin binding capability of the streptavidin labeled bead over its entire surface except for a small spot. These beads may also have applications in other biological experiments such as DNA force experiments in which binding of a single target to an individual bead is critical.

  11. Contact-free calibration of an asymmetric multi-layer interferometer for the surface force balance

    Science.gov (United States)

    Balabajew, Marco; van Engers, Christian D.; Perkin, Susan

    2017-12-01

    The Surface Force Balance (SFB, also known as Surface Force Apparatus, SFA) has provided important insights into many phenomena within the field of colloid and interface science. The technique relies on using white light interferometry to measure the distance between surfaces with sub-nanometer resolution. Up until now, the determination of the distance between the surfaces required a so-called "contact calibration," an invasive procedure during which the surfaces are brought into mechanical contact. This requirement for a contact calibration limits the range of experimental systems that can be investigated with SFB, for example, it precludes experiments with substrates that would be irreversibly modified or damaged by mechanical contact. Here we present a non-invasive method to measure absolute distances without performing a contact calibration. The method can be used for both "symmetric" and "asymmetric" systems. We foresee many applications for this general approach including, most immediately, experiments using single layer graphene electrodes in the SFB which may be damaged when brought into mechanical contact.

  12. The surface interactions of a near-neutral carbon nanoparticle tracer with calcite

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yan Vivian, E-mail: yan.li@colostate.edu [Colorado State University, Department of Design and Merchandising (United States); Cathles, Lawrence M., E-mail: lmc19@cornell.edu [Cornell University, Earth and Atmospheric Sciences (United States)

    2016-03-15

    A new class of nearly charge-neutral carbon-cored nanoparticle tracers are remarkably non-interactive with solid surfaces and could provide a valuable baseline for diverse hydrological and environmental studies of subsurface flow and particle transport. We investigate the causes of inertness by studying the interactions with calcite of a nanoparticle of this class synthesized from malic acid and ethanolamine (M-dots) dispersed in brine (NaCl, CaCl{sub 2}, and MgCl{sub 2}) solutions. None of the M-dots are retained in calcite sand-packed columns when dispersed in DI water. Dispersed in the NaCl and mixed brine solutions, 5.6 % of and 7.3 % of the M-dots are initially retained, but 65 and 13 % of these retained particles are subsequently released when the column is flushed with DI water. When dispersed in the CaCl{sub 2} and MgCl{sub 2} solutions, 65 and 54 % of the M-dots are initially retained, and 28 and 26 % subsequently released in the DI water flush. The M-dots have a small negative zeta potential in all solutions, but the calcite zeta potential changes from strongly negative to strongly positive across the solution series, and the particle retention tracks this change. Derjaguin–Landau–Verwey–Overbeek (DLVO) modeling of the force between a calcite probe and an M-dot coated surface shows that hydration forces repel the particles in the DI water, NaCl, and mixed solutions, but not in the CaCl{sub 2} and MgCl{sub 2} solutions. These results show that near-zero charge and strongly hydrophilic decoration are the causes of the remarkable inertness of carbon-cored nanoparticles, and also suggest that nanoparticles could be useful in solute-surface interaction studies.Graphical Abstract.

  13. The surface interactions of a near-neutral carbon nanoparticle tracer with calcite

    International Nuclear Information System (INIS)

    Li, Yan Vivian; Cathles, Lawrence M.

    2016-01-01

    A new class of nearly charge-neutral carbon-cored nanoparticle tracers are remarkably non-interactive with solid surfaces and could provide a valuable baseline for diverse hydrological and environmental studies of subsurface flow and particle transport. We investigate the causes of inertness by studying the interactions with calcite of a nanoparticle of this class synthesized from malic acid and ethanolamine (M-dots) dispersed in brine (NaCl, CaCl 2 , and MgCl 2 ) solutions. None of the M-dots are retained in calcite sand-packed columns when dispersed in DI water. Dispersed in the NaCl and mixed brine solutions, 5.6 % of and 7.3 % of the M-dots are initially retained, but 65 and 13 % of these retained particles are subsequently released when the column is flushed with DI water. When dispersed in the CaCl 2 and MgCl 2 solutions, 65 and 54 % of the M-dots are initially retained, and 28 and 26 % subsequently released in the DI water flush. The M-dots have a small negative zeta potential in all solutions, but the calcite zeta potential changes from strongly negative to strongly positive across the solution series, and the particle retention tracks this change. Derjaguin–Landau–Verwey–Overbeek (DLVO) modeling of the force between a calcite probe and an M-dot coated surface shows that hydration forces repel the particles in the DI water, NaCl, and mixed solutions, but not in the CaCl 2 and MgCl 2 solutions. These results show that near-zero charge and strongly hydrophilic decoration are the causes of the remarkable inertness of carbon-cored nanoparticles, and also suggest that nanoparticles could be useful in solute-surface interaction studies.Graphical Abstract

  14. The surface interactions of a near-neutral carbon nanoparticle tracer with calcite

    KAUST Repository

    Li, Yan Vivian

    2016-03-02

    A new class of nearly charge-neutral carbon-cored nanoparticle tracers are remarkably non-interactive with solid surfaces and could provide a valuable baseline for diverse hydrological and environmental studies of subsurface flow and particle transport. We investigate the causes of inertness by studying the interactions with calcite of a nanoparticle of this class synthesized from malic acid and ethanolamine (M-dots) dispersed in brine (NaCl, CaCl2, and MgCl2) solutions. None of the M-dots are retained in calcite sand-packed columns when dispersed in DI water. Dispersed in the NaCl and mixed brine solutions, 5.6 % of and 7.3 % of the M-dots are initially retained, but 65 and 13 % of these retained particles are subsequently released when the column is flushed with DI water. When dispersed in the CaCl2 and MgCl2 solutions, 65 and 54 % of the M-dots are initially retained, and 28 and 26 % subsequently released in the DI water flush. The M-dots have a small negative zeta potential in all solutions, but the calcite zeta potential changes from strongly negative to strongly positive across the solution series, and the particle retention tracks this change. Derjaguin–Landau–Verwey–Overbeek (DLVO) modeling of the force between a calcite probe and an M-dot coated surface shows that hydration forces repel the particles in the DI water, NaCl, and mixed solutions, but not in the CaCl2 and MgCl2 solutions. These results show that near-zero charge and strongly hydrophilic decoration are the causes of the remarkable inertness of carbon-cored nanoparticles, and also suggest that nanoparticles could be useful in solute-surface interaction studies.

  15. The study of dynamic force acted on water strider leg departing from water surface

    Directory of Open Access Journals (Sweden)

    Peiyuan Sun

    2018-01-01

    Full Text Available Water-walking insects such as water striders can skate on the water surface easily with the help of the hierarchical structure on legs. Numerous theoretical and experimental studies show that the hierarchical structure would help water strider in quasi-static case such as load-bearing capacity. However, the advantage of the hierarchical structure in the dynamic stage has not been reported yet. In this paper, the function of super hydrophobicity and the hierarchical structure was investigated by measuring the adhesion force of legs departing from the water surface at different lifting speed by a dynamic force sensor. The results show that the adhesion force decreased with the increase of lifting speed from 0.02 m/s to 0.4 m/s, whose mechanic is investigated by Energy analysis. In addition, it can be found that the needle shape setae on water strider leg can help them depart from water surface easily. Thus, it can serve as a starting point to understand how the hierarchical structure on the legs help water-walking insects to jump upward rapidly to avoid preying by other insects.

  16. The study of dynamic force acted on water strider leg departing from water surface

    Science.gov (United States)

    Sun, Peiyuan; Zhao, Meirong; Jiang, Jile; Zheng, Yelong

    2018-01-01

    Water-walking insects such as water striders can skate on the water surface easily with the help of the hierarchical structure on legs. Numerous theoretical and experimental studies show that the hierarchical structure would help water strider in quasi-static case such as load-bearing capacity. However, the advantage of the hierarchical structure in the dynamic stage has not been reported yet. In this paper, the function of super hydrophobicity and the hierarchical structure was investigated by measuring the adhesion force of legs departing from the water surface at different lifting speed by a dynamic force sensor. The results show that the adhesion force decreased with the increase of lifting speed from 0.02 m/s to 0.4 m/s, whose mechanic is investigated by Energy analysis. In addition, it can be found that the needle shape setae on water strider leg can help them depart from water surface easily. Thus, it can serve as a starting point to understand how the hierarchical structure on the legs help water-walking insects to jump upward rapidly to avoid preying by other insects.

  17. Generating Converged Accurate Free Energy Surfaces for Chemical Reactions with a Force-Matched Semiempirical Model.

    Science.gov (United States)

    Kroonblawd, Matthew P; Pietrucci, Fabio; Saitta, Antonino Marco; Goldman, Nir

    2018-03-22

    We demonstrate the capability of creating robust density functional tight binding (DFTB) models for chemical reactivity in prebiotic mixtures through force matching to short time scale quantum free energy estimates. Molecular dynamics using density functional theory (DFT) is a highly accurate approach to generate free energy surfaces for chemical reactions, but the extreme computational cost often limits the time scales and range of thermodynamic states that can feasibly be studied. In contrast, DFTB is a semiempirical quantum method that affords up to a thousandfold reduction in cost and can recover DFT-level accuracy. Here, we show that a force-matched DFTB model for aqueous glycine condensation reactions yields free energy surfaces that are consistent with experimental observations of reaction energetics. Convergence analysis reveals that multiple nanoseconds of combined trajectory are needed to reach a steady-fluctuating free energy estimate for glycine condensation. Predictive accuracy of force-matched DFTB is demonstrated by direct comparison to DFT, with the two approaches yielding surfaces with large regions that differ by only a few kcal mol -1 .

  18. Quantification of the lift height for magnetic force microscopy using 3D surface parameters

    International Nuclear Information System (INIS)

    Nenadovic, M.; Strbac, S.; Rakocevic, Z.

    2010-01-01

    In this work, the quantitative conditions for the lift height for imaging of the magnetic field using magnetic force microscopy (MFM) were optimized. A thin cobalt film deposited on a monocrystalline silicon (1 0 0) substrate with a thickness of 55 nm and a thin nickel film deposited on a glass with a thickness of 600 nm were used as samples. The topography of the surface was acquired by tapping mode atomic force microscopy (AFM), while MFM imaging was performed in the lift mode for various lift heights. It was determined that the sensitivity of the measurements was about 10% higher for images obtained at a scan angle of 90 o compared to a scan angle of 0 deg. Therefore, the three-dimensional surface texture parameters, i.e., average roughness, skewness, kurtosis and the bearing ratio, were determined in dependence on the lift height for a scan angle of 90 deg. The results of the analyses of the surface parameters showed that the influence of the substrate and its texture on the magnetic force image could be neglected for lift heights above 40 nm and that the upper lift height limit is 100 nm. It was determined that the optimal values of the lift heights were in the range from 60 to 80 nm, depending on the nature of the sample and on the type of the tip used.

  19. Interaction of water with faceted NiO(1 1 1) surface tuned by films thickness

    Science.gov (United States)

    Liu, Lixia; Wang, Shuai; Liu, Shuming; Guo, Qinlin; Guo, Jiandong

    2018-01-01

    The interaction of water with the polar surface of NiO(1 1 1) films has been investigated using various in situ surface analytical techniques, as well as ex situ scanning electron microscopy and atomic force microscopy. The {1 0 0} facets are formed on NiO(1 1 1) films upon annealing. The boundary between {1 0 0} facet and bare (1 1 1) face and the corner on the facet can facilitate dissociation of water. The total boundary length and the number of corner sites vary with film thickness. The dissociated hydroxyls are thermally stable up to 700 K on the thinner films. Consequently the activity of water dissociation can be tuned by adjusting the film thickness.

  20. Natural convection - radiation interaction in boundary layer flow over horizontal surfaces

    International Nuclear Information System (INIS)

    Ali, M.M.; Chen, T.S.; Armaly, B.F.

    1982-01-01

    A numerical model is developed for natural convection-radiation interaction in the boundary layer over a semi-infinite horizontal flat plate with one hot and one cold surface. The fluid is assumed to be gray, to emit, absorb, be nonscattering, and constant with a density variation in the vertical direction, which induces a buoyancy force. Two-dimensional, boundary-layer equations are defined, and the radiative heat flux is simplified using a Rosseland approximation. Conservation equations are transformed into a system of nonlinear ordinary differential equations which can be solved simultaneously with a Runge-Kutta integration scheme, along with the Newton-Raphson shooting technique. The thermal radiation is found to enhance the wall shear stress and the surface heat transfer rate on both the hot and cold sides

  1. Investigation of the range of validity of the pairwise summation method applied to the calculation of the surface roughness correction to the van der Waals force

    Science.gov (United States)

    Gusso, André; Burnham, Nancy A.

    2016-09-01

    It has long been recognized that stochastic surface roughness can considerably change the van der Waals (vdW) force between interacting surfaces and particles. However, few analytical expressions for the vdW force between rough surfaces have been presented in the literature. Because they have been derived using perturbative methods or the proximity force approximation the expressions are valid when the roughness correction is small and for a limited range of roughness parameters and surface separation. In this work, a nonperturbative approach, the effective density method (EDM) is proposed to circumvent some of these limitations. The method simplifies the calculations of the roughness correction based on pairwise summation (PWS), and allows us to derive simple expressions for the vdW force and energy between two semispaces covered with stochastic rough surfaces. Because the range of applicability of PWS and, therefore, of our results, are not known a priori, we compare the predictions based on the EDM with those based on the multilayer effective medium model, whose range of validity can be defined more properly and which is valid when the roughness correction is comparatively large. We conclude that the PWS can be used for roughness characterized by a correlation length of the order of its rms amplitude, when this amplitude is of the order of or smaller than a few nanometers, and only for typically insulating materials such as silicon dioxide, silicon nitride, diamond, and certain glasses, polymers and ceramics. The results are relevant for the correct modeling of systems where the vdW force can play a significant role such as micro and nanodevices, for the calculation of the tip-sample force in atomic force microscopy, and in problems involving adhesion.

  2. Hydrodynamic interactions between two forced objects of arbitrary shape. I. Effect on alignment

    Science.gov (United States)

    Goldfriend, Tomer; Diamant, Haim; Witten, Thomas A.

    2015-12-01

    We study the properties and symmetries governing the hydrodynamic interaction between two identical, arbitrarily shaped objects, driven through a viscous fluid. We treat analytically the leading (dipolar) terms of the pair-mobility matrix, affecting the instantaneous relative linear and angular velocities of the two objects at large separation. We prove that the instantaneous hydrodynamic interaction linearly degrades the alignment of asymmetric objects by an external time-dependent drive [B. Moths and T. A. Witten, "Full alignment of colloidal objects by programed forcing," Phys. Rev. Lett. 110, 028301 (2013)]. The time-dependent effects of hydrodynamic interactions are explicitly demonstrated through numerically calculated trajectories of model alignable objects composed of four stokeslets. In addition to the orientational effect, we find that the two objects usually repel each other. In this case, the mutual degradation weakens as the two objects move away from each other, and full alignment is restored at long times.

  3. Surface modification for interaction study with bacteria and preosteoblast cells

    Science.gov (United States)

    Song, Qing

    Surface modification plays a pivotal role in bioengineering. Polymer coatings can provide biocompatibility and biofunctionalities to biomaterials through surface modification. In this dissertation, initiated chemical vapor deposition (iCVD) was utilized to coat two-dimensional (2D) and three-dimensional (3D) substrates with differently charged polyelectrolytes in order to generate antimicrobial and osteocompatible biomaterials. ICVD is a modified CVD technique that enables surface modification in an all-dry condition without substrate damage and solvent contamination. The free-radical polymerization allows the vinyl polymers to conformally coat on various micro- and nano-structured substrates and maintains the delicate structure of the functional groups. The vapor deposition of polycations provided antimicrobial activity to planar and porous substrates through destroying the negatively charged bacterial membrane and brought about high contact-killing efficiency (99.99%) against Gram-positive Bacillus subtilis and Gram-negative Escherichia coli. Additionally, the polyampholytes synthesized by iCVD exhibited excellent antifouling performance against the adhesion of Gram-positive Listeria innocua and Gram-negative E. coli in phosphate buffered saline (PBS). Their antifouling activities were attributed to the electrostatic interaction and hydration layers that served as physical and energetic barriers to prevent bacterial adhesion. The contact-killing and antifouling polymers synthesized by iCVD can be applied to surface modification of food processing equipment and medical devices with the aim of reducing foodborne diseases and medical infections. Moreover, the charged polyelectrolyte modified 2D polystyrene surfaces displayed good osteocompatibility and enhanced osteogenesis of preosteoblast cells than the un-modified polystyrene surface. In order to promote osteoinduction of hydroxyapatite (HA) scaffolds, bioinspired polymer-controlled mineralization was conducted

  4. Two dimensional simulation of high power laser-surface interaction

    International Nuclear Information System (INIS)

    Goldman, S.R.; Wilke, M.D.; Green, R.E.L.; Johnson, R.P.; Busch, G.E.

    1998-01-01

    For laser intensities in the range of 10 8 --10 9 W/cm 2 , and pulse lengths of order 10 microsec or longer, the authors have modified the inertial confinement fusion code Lasnex to simulate gaseous and some dense material aspects of the laser-matter interaction. The unique aspect of their treatment consists of an ablation model which defines a dense material-vapor interface and then calculates the mass flow across this interface. The model treats the dense material as a rigid two-dimensional mass and heat reservoir suppressing all hydrodynamic motion in the dense material. The computer simulations and additional post-processors provide predictions for measurements including impulse given to the target, pressures at the target interface, electron temperatures and densities in the vapor-plasma plume region, and emission of radiation from the target. The authors will present an analysis of some relatively well diagnosed experiments which have been useful in developing their modeling. The simulations match experimentally obtained target impulses, pressures at the target surface inside the laser spot, and radiation emission from the target to within about 20%. Hence their simulational technique appears to form a useful basis for further investigation of laser-surface interaction in this intensity, pulse-width range. This work is useful in many technical areas such as materials processing

  5. Study of the interactions between endolysin and bacterial peptidoglycan on S. aureus by dynamic force spectroscopy

    Science.gov (United States)

    Liu, Jianli; Zhang, Xuejie; Yang, Hang; Yuan, Jinghe; Wei, Hongping; Yu, Junping; Fang, Xiaohong

    2015-09-01

    The cell wall binding domain (CBD) of bacteriophage lysins can recognize target bacteria with extraordinary specificity through binding to bacterial peptidoglycan, thus it is a promising new probe to identify the corresponding bacterial pathogen. In this work, we used atomic force microscopy (AFM) based single-molecule force spectroscopy to investigate the interaction between the CBD of lysin PlyV12 (PlyV12C) and pathogenic bacterium Staphylococcus aureus (S. aureus). The binding forces of PlyV12C with S. aureus have been measured, and the dissociation process of their binding complex has been characterized. Furthermore, we compared the interactions of PlyV12C-S. aureus and antibody-S. aureus. It is revealed that PlyV12C has a comparable affinity to bacterial peptidoglycans as that of the S. aureus antibody. The results provide new information on the binding properties of lysin CBD with bacterium, and the application of lysin CBD in bacterium detection.

  6. Interactions between topographically and thermally forced stationary waves: implications for ice-sheet evolution

    Directory of Open Access Journals (Sweden)

    Johan Liakka

    2012-01-01

    Full Text Available This study examines mutual interactions between stationary waves and ice sheets using a dry atmospheric primitive-equation model coupled to a three-dimensional thermomechanical ice-sheet model. The emphasis is on how non-linear interactions between thermal and topographical forcing of the stationary waves influence the ice-sheet evolution by changing the ablation. Simulations are conducted in which a small ice cap, on an idealised Northern Hemisphere continent, evolves to an equilibrium continental-scale ice sheet. In the absence of stationary waves, the equilibrium ice sheet arrives at symmetric shape with a zonal equatorward margin. In isolation, the topographically induced stationary waves have essentially no impact on the equilibrium features of the ice sheet. The reason is that the temperature anomalies are located far from the equatorward ice margin. When forcing due to thermal cooling is added to the topographical forcing, thermally induced perturbation winds amplify the topographically induced stationary-wave response, which that serves to increase both the equatorward extent and the volume of the ice sheet. Roughly, a 10% increase in the ice volume is reported here. Hence, the present study suggests that the topographically induced stationary-wave response can be substantially enhanced by the high albedo of ice sheets.

  7. Soil Parameter Identification and Driving Force Prediction for Wheel-Terrain Interaction

    Directory of Open Access Journals (Sweden)

    Suksun Hutangkabodee

    2008-11-01

    Full Text Available This paper considers wheeled vehicles traversing unknown terrain, and proposes an approach for identifying the unknown soil parameters required for vehicle driving force prediction (drawbar pull prediction. The predicted drawbar pull can potentially be employed for traversability prediction, traction control, and trajectory following which, in turn, improve overall performance of off-road wheeled vehicles. The proposed algorithm uses an approximated form of the wheel-terrain interaction model and the Generalized Newton Raphson method to identify terrain parameters in real-time. With few measurements of wheel slip, i, vehicle sinkage, z, and drawbar pull, DP, samples, the algorithm is capable of identifying all the soil parameters required to predict vehicle driving forces over an entire range of wheel slip. The algorithm is validated with experimental data from a wheel-terrain interaction test rig. The identified soil parameters are used to predict the drawbar pull with good accuracy. The technique presented in this paper can be applied to any vehicle with rigid wheels or deformable wheels with relatively high inflation pressure, to predict driving forces in unknown environments.

  8. Hydrodynamic interactions between two forced objects of arbitrary shape. II. Relative translation

    Science.gov (United States)

    Goldfriend, Tomer; Diamant, Haim; Witten, Thomas A.

    2016-04-01

    We study the relative translation of two arbitrarily shaped objects, caused by their hydrodynamic interaction as they are forced through a viscous fluid in the limit of zero Reynolds number. It is well known that in the case of two rigid spheres in an unbounded fluid, the hydrodynamic interaction does not produce relative translation. More generally, such an effective pair-interaction vanishes in configurations with spatial inversion symmetry; for example, an enantiomorphic pair in mirror image positions has no relative translation. We show that the breaking of inversion symmetry by boundaries of the system accounts for the interactions between two spheres in confined geometries, as observed in experiments. The same general principle also provides new predictions for interactions in other object configurations near obstacles. We examine the time-dependent relative translation of two self-aligning objects, extending the numerical analysis of our preceding publication [Goldfriend, Diamant, and Witten, Phys. Fluids 27, 123303 (2015)], 10.1063/1.4936894. The interplay between the orientational interaction and the translational one, in most cases, leads over time to repulsion between the two objects. The repulsion is qualitatively different for self-aligning objects compared to the more symmetric case of uniform prolate spheroids. The separation between the two objects increases with time t as t1 /3 in the former case, and more strongly, as t , in the latter.

  9. Quantifying surface albedo and other direct biogeophysical climate forcings of forestry activities.

    Science.gov (United States)

    Bright, Ryan M; Zhao, Kaiguang; Jackson, Robert B; Cherubini, Francesco

    2015-09-01

    By altering fluxes of heat, momentum, and moisture exchanges between the land surface and atmosphere, forestry and other land-use activities affect climate. Although long recognized scientifically as being important, these so-called biogeophysical forcings are rarely included in climate policies for forestry and other land management projects due to the many challenges associated with their quantification. Here, we review the scientific literature in the fields of atmospheric science and terrestrial ecology in light of three main objectives: (i) to elucidate the challenges associated with quantifying biogeophysical climate forcings connected to land use and land management, with a focus on the forestry sector; (ii) to identify and describe scientific approaches and/or metrics facilitating the quantification and interpretation of direct biogeophysical climate forcings; and (iii) to identify and recommend research priorities that can help overcome the challenges of their attribution to specific land-use activities, bridging the knowledge gap between the climate modeling, forest ecology, and resource management communities. We find that ignoring surface biogeophysics may mislead climate mitigation policies, yet existing metrics are unlikely to be sufficient. Successful metrics ought to (i) include both radiative and nonradiative climate forcings; (ii) reconcile disparities between biogeophysical and biogeochemical forcings, and (iii) acknowledge trade-offs between global and local climate benefits. We call for more coordinated research among terrestrial ecologists, resource managers, and coupled climate modelers to harmonize datasets, refine analytical techniques, and corroborate and validate metrics that are more amenable to analyses at the scale of an individual site or region. © 2015 John Wiley & Sons Ltd.

  10. Hydrodynamic forces on a wall-bound leukocyte due to interactions with flowing red cells

    Science.gov (United States)

    Isfahani, Amir H. G.; Freund, Jonathan B.

    2011-11-01

    As part of both healthy and pathologically physiological mechanisms sphere-like white blood cells (leukocytes) adhere to the walls of small blood vessels. We use quantitative numerical simulations to compare the forces from flowing red blood cells on a wall-adhered leukocyte to a homogenized model of blood at the same flow conditions. We model the highly flexible red blood cells using a fast O (N log N) boundary integral formulation. These elastic membranes deform substantially but strongly resist surface dilatation. They enclose a higher than plasma viscosity hemoglobin solution. The no-slip condition is enforced on the stationary leukocyte as well as the vessel walls. Vessel diameters of 10 to 20 microns are studied. Different hematocrits, leukocyte shapes, and flow conditions are examined. In vessels comparable to the size of the cells, we show that the particulate character of blood significantly affects the magnitude of the forces that the leukocyte experiences, transiently increasing it well above the homogenized-blood prediction: for example, for a tube hematocrit of 25 % and a spherical protrusion with a diameter 0.75 that of the tube, the average forces are increased by about 40 % and the local forces by more than 100 % relative to those expected for a blood model homogenized by its effective viscosity.

  11. Air–water interface of submerged superhydrophobic surfaces imaged by atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Markus Moosmann

    2017-08-01

    Full Text Available Underwater air retention of superhydrophobic hierarchically structured surfaces is of increasing interest for technical applications. Persistent air layers (the Salvinia effect are known from biological species, for example, the floating fern Salvinia or the backswimmer Notonecta. The use of this concept opens up new possibilities for biomimetic technical applications in the fields of drag reduction, antifouling, anticorrosion and under water sensing. Current knowledge regarding the shape of the air–water interface is insufficient, although it plays a crucial role with regards to stability in terms of diffusion and dynamic conditions. Optical methods for imaging the interface have been limited to the micrometer regime. In this work, we utilized a nondynamic and nondestructive atomic force microscopy (AFM method to image the interface of submerged superhydrophobic structures with nanometer resolution. Up to now, only the interfaces of nanobubbles (acting almost like solids have been characterized by AFM at these dimensions. In this study, we show for the first time that it is possible to image the air–water interface of submerged hierarchically structured (micro-pillars surfaces by AFM in contact mode. By scanning with zero resulting force applied, we were able to determine the shape of the interface and thereby the depth of the water penetrating into the underlying structures. This approach is complemented by a second method: the interface was scanned with different applied force loads and the height for zero force was determined by linear regression. These methods open new possibilities for the investigation of air-retaining surfaces, specifically in terms of measuring contact area and in comparing different coatings, and thus will lead to the development of new applications.

  12. The influence of Southern Ocean surface buoyancy forcing on glacial-interglacial changes in the global deep ocean stratification

    OpenAIRE

    Sun, S; Eisenman, I; Stewart, AL

    2016-01-01

    ©2016. American Geophysical Union. All Rights Reserved. Previous studies have suggested that the global ocean density stratification below ∼3000 m is approximately set by its direct connection to the Southern Ocean surface density, which in turn is constrained by the atmosphere. Here the role of Southern Ocean surface forcing in glacial-interglacial stratification changes is investigated using a comprehensive climate model and an idealized conceptual model. Southern Ocean surface forcing is f...

  13. Sticking like sticky tape: tree frogs use friction forces to enhance attachment on overhanging surfaces.

    Science.gov (United States)

    Endlein, Thomas; Ji, Aihong; Samuel, Diana; Yao, Ning; Wang, Zhongyuan; Barnes, W Jon P; Federle, Walter; Kappl, Michael; Dai, Zhendong

    2013-03-06

    To live and clamber about in an arboreal habitat, tree frogs have evolved adhesive pads on their toes. In addition, they often have long and slender legs to facilitate not only long jumps, but also to bridge gaps between leaves when climbing. Both adhesive pads and long limbs are used in conjunction, as we will show in this study. Previous research has shown that tree frogs change from a crouched posture (where the limbs are close to the body) to a sprawled posture with extended limbs when clinging on to steeper inclines such as vertical or overhanging slopes. We investigated this change in posture in White's tree frogs (Litoria caerulea) by challenging the frogs to cling onto a tiltable platform. The platform consisted of an array of 24 three-dimensional force transducers, which allowed us to measure the ground reaction forces of the frogs during a tilt. Starting from a crouched resting position, the normal forces on the forelimbs changed sign and became increasingly negative with increasing slope angle of the platform. At about 106° ± 12°, tilt of the platform the frogs reacted by extending one or two of their limbs outwards. At a steeper angle (131° ± 11°), the frogs spread out all their limbs sideways, with the hindlimbs stretched out to their maximum reach. Although the extension was strongest in the lateral direction, limbs were significantly extended in the fore-aft direction as well. With the extension of the limbs, the lateral forces increased relative to the normal forces. The large contribution of the in-plane forces helped to keep the angle between the force vector and the platform small. The Kendall theory for the peeling of adhesive tape predicts that smaller peel angles lead to higher attachment forces. We compare our data with the predictions of the Kendall model and discuss possible implications of the sliding of the pads on the surface. The forces were indeed much larger for smaller angles and thus can be explained by peeling theory.

  14. Constraining the surface properties of effective Skyrme interactions

    Science.gov (United States)

    Jodon, R.; Bender, M.; Bennaceur, K.; Meyer, J.

    2016-08-01

    Background: Deformation energy surfaces map how the total binding energy of a nuclear system depends on the geometrical properties of intrinsic configurations, thereby providing a powerful tool to interpret nuclear spectroscopy and large-amplitude collective-motion phenomena such as fission. The global behavior of the deformation energy is known to be directly connected to the surface properties of the effective interaction used for its calculation. Purpose: The precise control of surface properties during the parameter adjustment of an effective interaction is key to obtain a reliable and predictive description of nuclear properties. The most relevant indicator is the surface-energy coefficient asurf. There are several possibilities for its definition and estimation, which are not fully equivalent and require a computational effort that can differ by orders of magnitude. The purpose of this study is threefold: first, to identify a scheme for the determination of asurf that offers the best compromise between robustness, precision, and numerical efficiency; second, to analyze the correlation between values for asurf and the characteristic energies of the fission barrier of 240Pu; and third, to lay out an efficient and robust procedure for how the deformation properties of the Skyrme energy density functional (EDF) can be constrained during the parameter fit. Methods: There are several frequently used possibilities to define and calculate the surface energy coefficient asurf of effective interactions built for the purpose of self-consistent mean-field calculations. The most direct access is provided by the model system of semi-infinite nuclear matter, but asurf can also be extracted from the systematics of binding energies of finite nuclei. Calculations can be carried out either self-consistently [Hartree-Fock (HF)], which incorporates quantal shell effects, or in one of the semiclassical extended Thomas-Fermi (ETF) or modified Thomas-Fermi (MTF) approximations. The

  15. Interaction between two solid surfaces across PDMS : influence of chain length and end group

    NARCIS (Netherlands)

    Sun, G.X.; Stark, R.; Kappl, M.; Leermakers, F.A.M.; Butt, H.J.

    2005-01-01

    Forces between solid surfaces across polymer melts are poorly understood despite their importance for adhesion and composite materials. Using an atomic force microscope (AFM) this force was measured for poly(dimethyl siloxane) (PDMS) on silicon oxide. The influence of molecular weight (4.0-40 kDa)

  16. Nanoscale Surface Photovoltage Mapping of 2D Materials and Heterostructures by Illuminated Kelvin Probe Force Microscopy

    KAUST Repository

    Shearer, Melinda J.

    2018-02-01

    Nanomaterials are interesting for a variety of applications, such as optoelectronics and photovoltaics. However, they often have spatial heterogeneity, i.e. composition change or physical change in the topography or structure, which can lead to varying properties that would influence their applications. New techniques must be developed to understand and correlate spatial heterogeneity with changes in electronic properties. Here we highlight the technique of surface photovoltage-Kelvin probe force microscopy (SPV-KFM), which is a modified version of non-contact atomic force microscopy capable of imaging not only the topography and surface potential, but also the surface photovoltage on the nanoscale. We demonstrate its utility in probing monolayer WSe2-MoS2 lateral heterostructures, which form an ultrathin p-n junction promising for photovoltaic and optoelectronic applications. We show surface photovoltage maps highlighting the different photoresponse of the two material regions as a result of the effective charge separation across this junction. Additionally, we study the variations between different heterostructure flakes and emphasize the importance of controlling the synthesis and transfer of these materials to obtain consistent properties and measurements.

  17. Surface water and groundwater interaction in Marala - Khanki area, Punjab

    International Nuclear Information System (INIS)

    Akram, W.; Ahmad, M.; Latif, Z.; Tariq, J.A.; Malik, M.R.

    2011-07-01

    Isotope hydrological investigations were carried out in two selected areas of Indus Basin viz. Haripur Area and Chashma- Taunsa Area for elucidating various aspects of surface water and groundwater interaction. Groundwater samples were collected on seasonal basis (low and high river discharge periods) while surface water samples were collected more frequently (weekly or monthly basis). Isotopic data suggested that there is no contribution of surface water to groundwater recharge in Haripur Area and rain is the prevailing source of groundwater recharge. The data further revealed that isotopic values of the Haripur pocket of Tarbela Lake are higher than those of Main Lake / Indus River meaning that there is a significant contribution of base flow in this pocket. Indus River appeared to be the dominant source of groundwater recharge at most of the locations in Chashma- Taunsa Area. Isotopic data of Indus River showed an increase at Taunsa as compared to Chashma in low flow period indicating the high contribution of base flow at this point in time. Stable isotopes were successfully used to quantify the base flow contribution. (author)

  18. Evolvement of cell-substrate interaction over time for cells cultivated on a 3-aminopropyltriethoxysilane (γ-APTES) modified silicon dioxide (SiO2) surface

    Science.gov (United States)

    Hsu, Chung-Ping; Hsu, Po-Yen; Wu, You-Lin; Hsu, Wan-Yun; Lin, Jing-Jenn

    2012-09-01

    Since cell-substrate interaction is directly related to the traction force of the cell, the cell property can be judged from the imprint it leaves on the soft substrate surface onto which the cell is cultured. In this letter, the evolvement of the cell-substrate interaction over time was observed by cultivating cells on a 3-aminopropyltriethoxysilane (γ-APTES) modified silicon dioxide (SiO2) surface for different periods of time. The cell-substrate interaction property as a function of time can then be found from the post-cell-removal surface morphology profiles determined by atomic force microscopy (AFM). Different surface morphology profiles were found between normal cells and cancer cells. It was found that the cancer cells tend to form deeper trenches along the circumference of the imprints, while the normal cells do not. In addition, our results indicated that normal cells involve cell-substrate interaction mechanisms that are different from those for cancer cells.

  19. Analysis of bit-rock interaction during stick-slip vibrations using PDC cutting force model

    Energy Technology Data Exchange (ETDEWEB)

    Patil, P.A.; Teodoriu, C. [Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany). ITE

    2013-08-01

    Drillstring vibration is one of the limiting factors maximizing the drilling performance and also causes premature failure of drillstring components. Polycrystalline diamond compact (PDC) bit enhances the overall drilling performance giving the best rate of penetrations with less cost per foot but the PDC bits are more susceptible to the stick slip phenomena which results in high fluctuations of bit rotational speed. Based on the torsional drillstring model developed using Matlab/Simulink for analyzing the parametric influence on stick-slip vibrations due to drilling parameters and drillstring properties, the study of relations between weight on bit, torque on bit, bit speed, rate of penetration and friction coefficient have been analyzed. While drilling with the PDC bits, the bit-rock interaction has been characterized by cutting forces and the frictional forces. The torque on bit and the weight on bit have both the cutting component and the frictional component when resolved in horizontal and vertical direction. The paper considers that the bit is undergoing stick-slip vibrations while analyzing the bit-rock interaction of the PDC bit. The Matlab/Simulink bit-rock interaction model has been developed which gives the average cutting torque, T{sub c}, and friction torque, T{sub f}, values on cutters as well as corresponding average weight transferred by the cutting face, W{sub c}, and the wear flat face, W{sub f}, of the cutters value due to friction.

  20. Dynamics of gas-surface interactions atomic-level understanding of scattering processes at surfaces

    CERN Document Server

    Díez Muniño, Ricardo

    2013-01-01

    This book gives a representative survey of the state of the art of research on gas-surface interactions. It provides an overview of the current understanding of gas surface dynamics and, in particular, of the reactive and non-reactive processes of atoms and small molecules at surfaces. Leading scientists in the field, both from the theoretical and the experimental sides, write in this book about their most recent advances. Surface science grew as an interdisciplinary research area over the last decades, mostly because of new experimental technologies (ultra-high vacuum, for instance), as well as because of a novel paradigm, the ‘surface science’ approach. The book describes the second transformation which is now taking place pushed by the availability of powerful quantum-mechanical theoretical methods implemented numerically. In the book, experiment and theory progress hand in hand with an unprecedented degree of accuracy and control. The book presents how modern surface science targets the atomic-level u...

  1. Specific interactions of functionalised gold surfaces with ammonium perchlorate or starch; towards a chemical cartography of their mixture

    Energy Technology Data Exchange (ETDEWEB)

    Mercier, D. [CNRS, UMR CNRS 7609, Laboratoire de Reactivite de Surface, Paris (France); Universite Pierre et Marie Curie - UPMC Paris VI, Laboratoire de Reactivite de Surface, 4 place Jussieu, 75252 Paris Cedex 05 (France); Laboratoire de recherche conventionne CEA/UPMC n Degree-Sign 1, Paris (France); Mercader, C.; Quere, S.; Hairault, L. [CEA, DAM, Le Ripault, F-37260 Monts (France); Laboratoire de recherche conventionne CEA/UPMC n Degree-Sign 1, Paris (France); Methivier, C. [CNRS, UMR CNRS 7609, Laboratoire de Reactivite de Surface, Paris (France); Universite Pierre et Marie Curie - UPMC Paris VI, Laboratoire de Reactivite de Surface, 4 place Jussieu, 75252 Paris Cedex 05 (France); Laboratoire de recherche conventionne CEA/UPMC n Degree-Sign 1, Paris (France); Pradier, C.M., E-mail: claire-Marie.pradier@upmc.fr [CNRS, UMR CNRS 7609, Laboratoire de Reactivite de Surface, Paris (France); Universite Pierre et Marie Curie - UPMC Paris VI, Laboratoire de Reactivite de Surface, 4 place Jussieu, 75252 Paris Cedex 05 (France); Laboratoire de recherche conventionne CEA/UPMC n Degree-Sign 1, Paris (France)

    2012-10-01

    Highlights: Black-Right-Pointing-Pointer Measurements of interactions by Quartz Crystal Microbalance. Black-Right-Pointing-Pointer AFM and CFM measurements, tip functionalisation. Black-Right-Pointing-Pointer Surface nano-imaging. - Abstract: By functionalising gold samples, planar wafers or AFM tips, with an acid- or an amino acid-terminated thiols, mercaptoundecanoic acid (MUA) and homocystein (H-Cyst) respectively, we were able to differentiate the interactions with ammonium perchlorate (AP) and starch (S), two components of a nanocomposition mixture. To do so, the interaction between gold functionalized surfaces and the two targeted compounds have been characterized and quantified by several complementary techniques. Polarisation modulation-infrared spectroscopy (PM-IRRAS), and X-ray photoelectron spectroscopy (XPS), providing chemical analyses of gold surfaces after contacting S or AP, proved that both compounds were retained on MUA or H-Cyst-modified surfaces, but to various extents. Quartz crystal microbalance on-line measurements enabled to monitor the kinetics of interaction and showed distinct differences in the behaviour of MUA and H-Cyst-surfaces towards the two compounds. Having observed that only H-Cyst-modified surfaces enables to get a contrast on the chemical force microscopy (CFM) images, this new result could be well explained by examining the data obtained by combining the above-mentioned surface characterisation techniques.

  2. The Influence of Long-Range Surface Forces on the Contact Angle of Nanometric Droplets and Bubbles.

    Science.gov (United States)

    Stocco, Antonio; Möhwald, Helmuth

    2015-11-03

    For a droplet or a bubble of dimensions below 100 nm, long-range surface forces such as long-range van der Waals forces can compete with capillarity, which leads to a size dependence of the contact angle. This is discussed in this work, where we also show that the effect cannot simply be described by a normalized line tension. We calculate interfacial profiles for typical values of van der Waals forces and discuss the role of long-range surface forces on the contact angle of nanobubbles and nanodrops.

  3. Multiparametric Kelvin Probe Force Microscopy for the Simultaneous Mapping of Surface Potential and Nanomechanical Properties.

    Science.gov (United States)

    Xie, Hui; Zhang, Hao; Hussain, Danish; Meng, Xianghe; Song, Jianmin; Sun, Lining

    2017-03-21

    We report high-resolution multiparametric kelvin probe force microscopy (MP-KPFM) measurements for the simultaneous quantitative mapping of the contact potential difference (CPD) and nanomechanical properties of the sample in single-pass mode. This method combines functionalities of the force-distance-based atomic force microscopy and amplitude-modulation (AM) KPFM to perform measurements in single-pass mode. During the tip-sample approach-and-retract cycle, nanomechanical measurements are performed for the retract part of nanoindentation, and the CPD is measured by the lifted probe with a constant tip-sample distance. We compare the performance of the proposed method with the conventional KPFMs by mapping the CPD of multilayer graphene deposited on n-doped silicon, and the results demonstrate that MP-KPFM has comparable performance to AM-KPFM. In addition, the experimental results of a custom-fabricated polymer grating with heterogeneous surfaces validate the multiparametric imaging capability of the MP-KPFM. This method can have potential applications in finding the inherent link between nanomechanical properties and the surface potential of the materials, such as the quantification of the electromechanical response of the deformed piezoelectric materials.

  4. Sensitivity of Horn of Africa Rainfall to Regional Sea Surface Temperature Forcing

    Directory of Open Access Journals (Sweden)

    Zewdu T. Segele

    2015-05-01

    Full Text Available The Abdus Salam International Center for Theoretical Physics (ICTP version 4.4 Regional Climate Model (RegCM4 is used to investigate the rainfall response to cooler/warmer sea surface temperature anomaly (SSTA forcing in the Indian and Atlantic Oceans. The effect of SSTA forcing in a specific ocean basin is identified by ensemble, averaging 10 individual simulations in which a constant or linearly zonally varying SSTA is prescribed in individual basins while specifying the 1971–2000 monthly varying climatological sea surface temperature (SST across the remaining model domain. The nonlinear rainfall response to SSTA amplitude also is investigated by separately specifying +1K, +2K, and +4K SSTA forcing in the Atlantic and Indian Oceans. The simulation results show that warm SSTs over the entire Indian Ocean produce drier conditions across the larger Blue Nile catchment, whereas warming ≥ +2K generates large positive rainfall anomalies exceeding 10 mm·day−1 over drought prone regions of Northeastern Ethiopia. However, the June–September rainy season tends to be wetter (drier when the SST warming (cooling is limited to either the Northern or Southern Indian Ocean. Wet rainy seasons generally are characterized by deepening of the monsoon trough, east of 40°E, intensification of the Mascarene high, strengthening of the Somali low level jet and the tropical easterly jet, enhanced zonal and meridional vertically integrated moisture fluxes, and steeply vertically decreasing moist static energy. The opposite conditions hold for dry monsoon seasons.

  5. An interaction network perspective on the relation between patterns of sea surface temperature variability and global mean surface temperature

    NARCIS (Netherlands)

    Tantet, A.J.J.; Dijkstra, H.A.

    2014-01-01

    On interannual- to multidecadal timescales variability in sea surface temperature appears to be organized in large-scale spatiotemporal patterns. In this paper, we investigate these patterns by studying the community structure of interaction networks constructed from sea surface temperature

  6. Do climate simulations from models forced by averaged sea surface temperatures represent actual dynamics?

    Directory of Open Access Journals (Sweden)

    P. J. Roebber

    1997-01-01

    Full Text Available Recently atmospheric general circulation models (AGCMs forced by observed sea surface temperatures (SSTs have offered the possibility of studying climate variability over periods ranging from years to decades. Such models represent and alternative to fully coupled asynchronous atmosphere ocean models whose long term integration remains problematic. Here, the degree of the approximation represented by this approach is investigated from a conceptual point of view by comparing the dynamical properties of a low order coupled atmosphere-ocean model to those of the atmospheric component of the same model when forced with monthly values of SST derived from the fully coupled simulation. The low order modelling approach is undertaken with the expectation that it may reveal general principles concerning the dynamical behaviour of the forced versus coupled systems; it is not expected that such an approach will determine the details of these differences, for which higher order modelling studies will be required. We discover that even though attractor (global averages may be similar, local dynamics and the resultant variability and predictability characteristics differ substantially. These results suggest that conclusions concerning regional climatic variability (in time as well as space drawn from forced modelling approaches may be contaminated by an inherently unquantifiable error. It is therefore recommended that this possibility be carefully investigated using state-of-the-art coupled AGCMs.

  7. Revised model for the radiation force exerted by standing surface acoustic waves on a rigid cylinder

    Science.gov (United States)

    Liang, Shen; Chaohui, Wang

    2018-03-01

    In this paper, a model for the radiation force exerted by standing surface acoustic waves (SSAWs) on a rigid cylinder in inviscid fluids is extended to account for the dependence on the Rayleigh angle. The conventional model for the radiation force used in the SSAW-based applications is developed in plane standing waves, which fails to predict the movement of the cylinder in the SSAW. Our revised model reveals that, in the direction normal to the piezoelectric substrate on which the SSAW is generated, acoustic radiation force can be large enough to drive the cylinder even in the long-wavelength limit. Furthermore, the force in this direction can not only push the cylinder away, but also pull it back toward the substrate. In the direction parallel to the substrate, the equilibrium positions for particles can be actively tuned by changing Rayleigh angle. As an example considered in the paper, with the reduction of Rayleigh angle the equilibrium positions for steel cylinders in water change from pressure nodes to pressure antinodes. The model can thus be used in the design of SSAWs for particle manipulations.

  8. Modeling of the interaction between grip force and vibration transmissibility of a finger.

    Science.gov (United States)

    Wu, John Z; Welcome, Daniel E; McDowell, Thomas W; Xu, Xueyan S; Dong, Ren G

    2017-07-01

    It is known that the vibration characteristics of the fingers and hand and the level of grip action interacts when operating a power tool. In the current study, we developed a hybrid finger model to simulate the vibrations of the hand-finger system when gripping a vibrating handle covered with soft materials. The hybrid finger model combines the characteristics of conventional finite element (FE) models, multi-body musculoskeletal models, and lumped mass models. The distal, middle, and proximal finger segments were constructed using FE models, the finger segments were connected via three flexible joint linkages (i.e., distal interphalangeal joint (DIP), proximal interphalangeal joint (PIP), and metacarpophalangeal (MCP) joint), and the MCP joint was connected to the ground and handle via lumped parameter elements. The effects of the active muscle forces were accounted for via the joint moments. The bone, nail, and hard connective tissues were assumed to be linearly elastic whereas the soft tissues, which include the skin and subcutaneous tissues, were considered as hyperelastic and viscoelastic. The general trends of the model predictions agree well with the previous experimental measurements in that the resonant frequency increased from proximal to the middle and to the distal finger segments for the same grip force, that the resonant frequency tends to increase with increasing grip force for the same finger segment, especially for the distal segment, and that the magnitude of vibration transmissibility tends to increase with increasing grip force, especially for the proximal segment. The advantage of the proposed model over the traditional vibration models is that it can predict the local vibration behavior of the finger to a tissue level, while taking into account the effects of the active musculoskeletal force, the effects of the contact conditions on vibrations, the global vibration characteristics. Published by Elsevier Ltd.

  9. Cross-Surface: Workshop on Interacting with Multi-Device Ecologies in the Wild

    DEFF Research Database (Denmark)

    Houben, Steven; Vermeulen, Jo; Klokmose, Clemens Nylandsted

    2015-01-01

    In this workshop, we will review and discuss opportunities, technical challenges and problems with cross-device interactions in interactive multi-surface and multi-device ecologies. We aim to bring together researchers and practitioners currently working on novel techniques for cross......-surface interactions, identify application domains and enabling technologies for cross-surface interactions in the wild, and establish a research community to develop effective strategies for successful design of cross-device interactions....

  10. Molecular dynamics simulations of the DNA interaction with metallic nanoparticles and TiO2 surfaces

    International Nuclear Information System (INIS)

    Kholmurodov, Kh.T.; Krasavin, E.A.; Dushanov, E.B.; Hassan, H.K.; Galal, A.; ElHabashy, H.A.; Sweilam, N.H.; Yasuoka, K.

    2013-01-01

    The understanding of the mechanism of DNA interactions and binding with metallic nanoparticles (NPs) and surfaces represents a great interest in today's medicine applications due to diagnostic and treatment of oncology diseases. Recent experimental and simulation studies involve the DNA interaction with highly localized proton beams or metallic NPs (such as Ag, Au, etc.), aimed at targeted cancer therapy through the injection of metal micro- or nanoparticles into the tumor tissue with consequent local microwave or laser heating. The effects of mutational structure changes in DNA and protein structures could result in destroying of native chemical (hydrogen) bonds or, on the contrary, creating of new bonds that do not normally exist there. The cause of such changes might be the alteration of one or several nucleotides (in DNA) or the substitution of specific amino acid residues (in proteins) that can lead to the essential structural destabilization or unfolding. At the atomic or molecular level, the replacement of one nucleotide by another (in DNA double helices) or replacement of one amino acid residue by another (in proteins) cause essential modifications of the molecular force fields of the environment that break locally important hydrogen bonds underlying the structural stability of the biological molecules. In this work, the molecular dynamics(MD) simulations were performed for four DNA models and the flexibilities of the purine and pyrimidine nucleotides during the interaction process with the metallic NPs and TiO 2 surface were clarified

  11. The interaction of two collinear cracks in a rectangular superconductor slab under an electromagnetic force

    International Nuclear Information System (INIS)

    Gao Zhiwen; Zhou Youhe; Lee, Kang Yong

    2010-01-01

    The interaction of two collinear cracks is obtained for a type-II superconducting under electromagnetic force. Fracture analysis is performed by means of finite element method and the magnetic behavior of superconductor is described by the critical-state Bean model. The stress intensity factors at the crack tips can be obtained and discussed for decreasing field after zero-field cooling. It is revealed that the stress intensity factor decreases as applied field increases. The crack-tip stress intensity factors decrease when the distance between the two collinear cracks increases and the superconductors with smaller crack has more remarkable shielding effect than those with larger cracks.

  12. Direct visualization of ligand-protein interactions using atomic force microscopy

    OpenAIRE

    Neish, Calum S; Martin, Ian L; Henderson, Robert M; Edwardson, J Michael

    2002-01-01

    Streptavidin is a 60-kDa tetramer which binds four molecules of biotin with extremely high affinity (KA∼1014 M−1). We have used atomic force microscopy (AFM) to visualize this ligand-protein interaction directly.Biotin was tagged with a short (152-basepair; 50-nm) DNA rod and incubated with streptavidin. The resulting complexes were then imaged by AFM. The molecular volume of streptavidin calculated from the dimensions of the protein particles (105±3 nm3) was in close agreement with the value...

  13. Synthesis of ZnS nanoparticles on a solid surface: Atomic force microscopy study

    International Nuclear Information System (INIS)

    Yuan Huizhen; Lian Wenping; Song Yonghai; Chen Shouhui; Chen Lili; Wang Li

    2010-01-01

    In this work, zinc sulfide (ZnS) nanoparticles had been synthesized on DNA network/mica and mica surface, respectively. The synthesis was carried out by first dropping a mixture of zinc acetate and DNA on a mica surface for the formation of the DNA networks or zinc acetate solution on a mica surface, and subsequently transferring the sample into a heated thiourea solution. The Zn 2+ adsorbed on DNA network/mica or mica surface would react with S 2- produced from thiourea and form ZnS nanoparticles on these surfaces. X-ray diffraction and atomic force microscopy (AFM) were used to characterize the ZnS nanoparticles in detail. AFM results showed that ZnS nanoparticles distributed uniformly on the mica surface and deposited preferentially on DNA networks. It was also found that the size and density of ZnS nanoparticles could be effectively controlled by adjusting reaction temperature and the concentration of Zn 2+ or DNA. The possible growth mechanisms have been discussed in detail.

  14. Effect of particle-particle interactions on the acoustic radiation force in an ultrasonic standing wave

    Energy Technology Data Exchange (ETDEWEB)

    Lipkens, Bart, E-mail: blipkens@wne.edu [Mechanical Engineering, Western New England University, Springfield, Massachusetts, 01119 (United States); Ilinskii, Yurii A., E-mail: ilinskii@gmail.com; Zabolotskaya, Evgenia A., E-mail: zheniazabolotskaya@gmail.com [Applied Research Laboratories, The University of Texas at Austin, Austin, Texas 78713–8029 (United States)

    2015-10-28

    Ultrasonic standing waves are widely used for separation applications. In MEMS applications, a half wavelength standing wave field is generated perpendicular to a laminar flow. The acoustic radiation force exerted on the particle drives the particle to the center of the MEMS channel, where concentrated particles are harvested. In macro-scale applications, the ultrasonic standing wave spans multiple wavelengths. Examples of such applications are oil/water emulsion splitting [1], and blood/lipid separation [2]. In macro-scale applications, particles are typically trapped in the standing wave, resulting in clumping or coalescence of particles/droplets. Subsequent gravitational settling results in separation of the secondary phase. An often used expression for the radiation force on a particle is that derived by Gorkov [3]. The assumptions are that the particle size is small relative to the wavelength, and therefore, only monopole and dipole scattering contributions are used to calculate the radiation force. This framework seems satisfactory for MEMS scale applications where each particle is treated separately by the standing wave, and concentrations are typically low. In macro-scale applications, particle concentration is high, and particle clumping or droplet coalescence results in particle sizes not necessarily small relative to the wavelength. Ilinskii et al. developed a framework for calculation of the acoustic radiation force valid for any size particle [4]. However, this model does not take into account particle to particle effects, which can become important as particle concentration increases. It is known that an acoustic radiation force on a particle or a droplet is determined by the local field. An acoustic radiation force expression is developed that includes the effect of particle to particle interaction. The case of two neighboring particles is considered. The approach is based on sound scattering by the particles. The acoustic field at the location of

  15. Multi-Finger Interaction and Synergies in Finger Flexion and Extension Force Production

    Directory of Open Access Journals (Sweden)

    Jaebum Park

    2017-06-01

    Full Text Available The aim of this study was to discover finger interaction indices during single-finger ramp tasks and multi-finger coordination during a steady state force production in two directions, flexion, and extension. Furthermore, the indices of anticipatory adjustment of elemental variables (i.e., finger forces prior to a quick pulse force production were quantified. It is currently unknown whether the organization and anticipatory modulation of stability properties are affected by force directions and strengths of in multi-finger actions. We expected to observe a smaller finger independency and larger indices of multi-finger coordination during extension than during flexion due to both neural and peripheral differences between the finger flexion and extension actions. We also examined the indices of the anticipatory adjustment between different force direction conditions. The anticipatory adjustment could be a neural process, which may be affected by the properties of the muscles and by the direction of the motions. The maximal voluntary contraction (MVC force was larger for flexion than for extension, which confirmed the fact that the strength of finger flexor muscles (e.g., flexor digitorum profundus was larger than that of finger extensor (e.g., extensor digitorum. The analysis within the uncontrolled manifold (UCM hypothesis was used to quantify the motor synergy of elemental variables by decomposing two sources of variances across repetitive trials, which identifies the variances in the uncontrolled manifold (VUCM and that are orthogonal to the UCM (VORT. The presence of motor synergy and its strength were quantified by the relative amount of VUCM and VORT. The strength of motor synergies at the steady state was larger in the extension condition, which suggests that the stability property (i.e., multi-finger synergies may be a direction specific quantity. However, the results for the existence of anticipatory adjustment; however, no difference

  16. Roll Damping Derivatives from Generalized Lifting-Surface Theory and Wind Tunnel Forced-Oscillation Tests

    Science.gov (United States)

    Pototzky, Anthony S; Murphy, Patrick C.

    2014-01-01

    Improving aerodynamic models for adverse loss-of-control conditions in flight is an area being researched under the NASA Aviation Safety Program. Aerodynamic models appropriate for loss of control conditions require a more general mathematical representation to predict nonlinear unsteady behaviors. As more general aerodynamic models are studied that include nonlinear higher order effects, the possibility of measurements that confound aerodynamic and structural responses are probable. In this study an initial step is taken to look at including structural flexibility in analysis of rigid-body forced-oscillation testing that accounts for dynamic rig, sting and balance flexibility. Because of the significant testing required and associated costs in a general study, it makes sense to capitalize on low cost analytical methods where possible, especially where structural flexibility can be accounted for by a low cost method. This paper provides an initial look at using linear lifting surface theory applied to rigid-body aircraft roll forced-oscillation tests.

  17. Multi-scale cell/surface interaction on modified titanium aluminum vanadium surfaces

    Science.gov (United States)

    Chen, Jianbo

    This dissertation presents a series of experimental studies of the effects of multi-scale cell/surface interactions on modified Ti-6Al-4V surfaces. These include laser-grooved surfaces; porous structures and RGD-coated laser-grooved surfaces. A nano-second DPSS UV lasers with a Gaussian pulse energy profile was used to introduce the desired micro-groove geometries onto Ti-6Al-4V surfaces. This was done without inducing micro-cracks or significant changes in surface chemistry within the heat affected zones. The desired 8-12 mum groove depths and widths were achieved by the control of pulse frequency, scan speed, and the lens focal length that controls spot size. The interactions between human osteosarcoma (HOS) cells and laser-grooved Ti-6Al-4V surfaces were investigated after 48 hours of cell culture. The cell behavior, including cell spreading, alignment and adhesion, was elucidated using scanning electronic microscopy (SEM), immuno-fluorescence staining and enzymatic detachment. Contact guidance was shown to increase as grooved spacing decreased. For the range of micro-groove geometries studied, micro-grooves with groove spacings of 20 mum provided the best combination of cell orientation and adhesion. Short-term adhesion experiments (15 mins to 1 day) also revealed that there is a positive correlation between cell orientation and cell adhesion. Contact guidance on the micro-grooved surfaces is shown to be enhanced by nano- and micro-scale asperities that provide sites for the attachment of lamellopodia during cell locomotion and spreading. Contact guidance is also promoted by the geometrical confinement provided by laser grooves. An experimental study of initial cell spreading and ingrowth into Ti-6Al-4V porous structures was also carried out on porous structures with different pore sizes and geometries. A combination of SEM, the tetrazolium salt (MTT) colorimetric assay and enzymatic detachment were used to study cell spreading and adhesion. The extent of cell

  18. Response of tropical sea surface temperature, precipitation, and tropical cyclone-related variables to changes in global and local forcing

    Science.gov (United States)

    Emanuel, Kerry; Sobel, Adam

    2013-06-01

    A single-column model is used to estimate the equilibrium response of sea surface temperature (SST), precipitation, and several variables related to tropical cyclone (TC) activity to changes in both local and global forcing. Response to local forcing is estimated using the weak temperature gradient (WTG) approximation. The surface temperature is calculated using a thin slab ocean so as to maintain surface energy balance. Forcing is varied by changing the solar constant, atmospheric CO2 concentration, surface wind speed, and the convergence of upper ocean heat flux. These experiments show that precipitation and variables related to TC activity are not unique functions of SST on time scales long enough for surface energy balance to be maintained. Precipitation varies inversely with SST in experiments in which the surface wind speed is varied. At low wind speed, the WTG experiments reveal a regime of high relative SST and low precipitation, which is maintained by increased transmission of longwave radiation from the surface directly to space through a dry troposphere. In general, TC potential intensity and genesis potential vary much more rapidly with SST in response to varying surface wind speed than in response to other forcings. Local changes in TC potential intensity are highly correlated with local changes in SST, showing that relative SST is a good proxy for potential intensity when forcing is strictly local, but it cannot capture potentially important changes in potential intensity that arise from global-scale changes in forcing.

  19. SELMA: a mission to study lunar environment and surface interaction

    Science.gov (United States)

    Barabash, Stas; Futaana, Yoshifumi

    2017-04-01

    SELMA (Surface, Environment, and Lunar Magnetic Anomalies) proposed for the ESA M5 mission opportunity is a mission to study how the Moon environment and surface interact. SELMA addresses four overarching science questions: (1) What is the origin of water on the Moon? (2) How do the "volatile cycles" on the Moon work? (3) How do the lunar mini-magnetospheres work? (4) What is the influence of dust on the lunar environment and surface? SELMA uses a unique combination of remote sensing via UV, IR, and energetic neutral atoms and local measurements of plasma, fields, waves, exospheric gasses, and dust. It will also conduct an impact experiment to investigate volatile content in the soil of the permanently shadowed area of the Shakleton crater. SELMA carries an impact probe to sound the Reiner-Gamma mini-magnetosphere and its interaction with the lunar regolith from the SELMA orbit down to the surface. The SELMA science objectives include: - Establish the role of the solar wind and exosphere in the formation of the water bearing materials; - Determine the water content in the regolith of the permanently shadowed region and its isotope composition; - Establish variability, sources and sinks of the lunar exosphere and its relations to impact events; - Investigate a mini-magnetosphere interaction with the solar wind; - Investigate the long-term effects of mini-magnetospheres on the local surface; - Investigate how the impact events affect the lunar dust environments; - Investigate how the plasma effects result in lofting the lunar dust; SELMA is a flexible and short (15 months) mission including the following elements SELMA orbiter, SELMA Impact Probe for Magnetic Anomalies (SIP-MA), passive Impactor, and Relaying CubeSat (RCS). SELMA is placed on quasi-frozen polar orbit 30 km x 200 km with the pericenter over the South Pole. Approximately 9 months after the launch SELMA releases SIP-MA to sound the Reiner-Gamma magnetic anomaly with very high time resolution 10 sec

  20. Ultrasound-Stimulated Mutual Interaction Forces between Optically Configured Micro-Bubble Pairs

    Science.gov (United States)

    Prentice, Paul A.; Campbell, Paul A.

    2007-05-01

    The mutual interaction between two oscillating encapsulated microbubbles was investigated using a novel optical trapping arrangement. This approach facilitated the development of an arbitrary, stable, initial spatial configuration for a two-bubble system. Critically, exercising optical control over such a binary bubble system meant that it could be isolated from the resident population of microbubbles during exposure to ultrasound. This ensured that any early stage dynamical evolution of the system was dominated by the mutual interaction of the two bubbles in view, rather than any extraneous influence arising from `crosstalk' with the rest of the bubble population. We observed, using high speed microphotography at 4×105 frames per second, that the action of secondary radiation forces leads to mutual bubble attraction. Phenomena such as coalescence and `bounce' were observed. Estimates of the microbubble [Sonovue™] compressibility could also be made, and tally well with published values obtained for other shelled contrast agents.

  1. Robot Physical Interaction through the combination of Vision, Tactile and Force Feedback Applications to Assistive Robotics

    CERN Document Server

    Prats, Mario; Sanz, Pedro J

    2013-01-01

    Robot manipulation is a great challenge; it encompasses versatility -adaptation to different situations-, autonomy -independent robot operation-, and dependability -for success under modeling or sensing errors. A complete manipulation task involves, first, a suitable grasp or contact configuration, and the subsequent motion required by the task. This monograph presents a unified framework by introducing task-related aspects into the knowledge-based grasp concept, leading to task-oriented grasps. Similarly, grasp-related issues are also considered during the execution of a task, leading to grasp-oriented tasks which is called framework for physical interaction (FPI). The book presents the theoretical framework for the versatile specification of physical interaction tasks, as well as the problem of autonomous planning of these tasks. A further focus is on sensor-based dependable execution combining three different types of sensors: force, vision and tactile. The FPI approach allows to perform a wide range of ro...

  2. Epitaxial growth of pentacene on alkali halide surfaces studied by Kelvin probe force microscopy.

    Science.gov (United States)

    Neff, Julia L; Milde, Peter; León, Carmen Pérez; Kundrat, Matthew D; Eng, Lukas M; Jacob, Christoph R; Hoffmann-Vogel, Regina

    2014-04-22

    In the field of molecular electronics, thin films of molecules adsorbed on insulating surfaces are used as the functional building blocks of electronic devices. Control of the structural and electronic properties of the thin films is required for reliably operating devices. Here, noncontact atomic force and Kelvin probe force microscopies have been used to investigate the growth and electrostatic landscape of pentacene on KBr(001) and KCl(001) surfaces. We have found that, together with molecular islands of upright standing pentacene, a new phase of tilted molecules appears near step edges on KBr. Local contact potential differences (LCPD) have been studied with both Kelvin experiments and density functional theory calculations. Our images reveal that differently oriented molecules display different LCPD and that their value is independent of the number of molecular layers. These results point to the formation of an interface dipole, which may be explained by a partial charge transfer from the pentacene to the surface. Moreover, the monitoring of the evolution of the pentacene islands shows that they are strongly affected by dewetting: Multilayers build up at the expense of monolayers, and in the Kelvin images, previously unknown line defects appear, which reveal the epitaxial growth of pentacene crystals.

  3. The influence of tool path strategies on cutting force and surface texture during ball end milling of low curvature convex surfaces.

    Science.gov (United States)

    Shajari, Shaghayegh; Sadeghi, Mohammad Hossein; Hassanpour, Hamed

    2014-01-01

    Advancement in machining technology of curved surfaces for various engineering applications is increasing. Various methodologies and computer tools have been developed by the manufacturers to improve efficiency of freeform surface machining. Selection of the right sets of cutter path strategies and appropriate cutting conditions is extremely important in ensuring high productivity rate, meeting the better quality level, and lower cutting forces. In this paper, cutting force as a new decision criterion for the best selection of tool paths on convex surfaces is presented. Therefore, this work aims at studying and analyzing different finishing strategies to assess their influence on surface texture, cutting forces, and machining time. Design and analysis of experiments are performed by means of Taguchi technique and analysis of variance. In addition, the significant parameters affecting the cutting force in each strategy are introduced. Machining strategies employed include raster, 3D-offset, radial, and spiral. The cutting parameters were feed rate, cutting speed, and step over. The experiments were carried out on low curvature convex surfaces of stainless steel 1.4903. The conclusion is that radial strategy provokes the best surface texture and the lowest cutting forces and spiral strategy signifies the worst surface texture and the highest cutting forces.

  4. Nanoparticle-nanoparticle interactions in biological media by Atomic Force Microscopy

    Science.gov (United States)

    Pyrgiotakis, Georgios; Blattmann, Christoph O.; Pratsinis, Sotiris; Demokritou, Philip

    2015-01-01

    Particle-particle interactions in physiological media are important determinants for nanoparticle fate and transport. Herein, such interactions are assessed by a novel Atomic Force Microscopy (AFM) based platform. Industry-relevant CeO2, Fe2O3, and SiO2 nanoparticles of various diameters were made by the flame spray pyrolysis (FSP) based Harvard Versatile Engineering Nanomaterials Generation System (Harvard VENGES). The nanoparticles were fully characterized structurally and morphologically and their properties in water and biological media were also assessed. The nanoparticles were attached on AFM tips and deposited on Si substrates to measure particle–particle interactions. The corresponding force was measured in air, water and biological media that are widely used in toxicological studies. The presented AFM based approach can be used to assess the agglomeration potential of nanoparticles in physiological fluids. The agglomeration potential of CeO2 nanoparticles in water and RPMI 1640 (Roswell Park Memorial Institute formulation 1640) was inversely proportional to their primary particle (PP) diameter, but for Fe2O3 nanoparticles, that potential is independent of PP diameter in these media. Moreover, in RPMI+10% Fetal Bovine Serum (FBS) the corona thickness and dispersibility of the CeO2 is independent of PP diameter while for Fe2O3, the corona thickness and dispersibility were inversely proportional to PP diameter. The present method can be combined with (dynamic light scattering (DLS), proteomics, and computer simulations to understand the nano-bio interactions, with emphasis on the agglomeration potential of nanoparticles and their transport in physiological media. PMID:23978039

  5. Optodynamics: dynamic aspects of laser beam-surface interaction

    International Nuclear Information System (INIS)

    Možina, J; Diaci, J

    2012-01-01

    This paper presents a synthesis of the results of our original research in the area of laser-material interaction and pulsed laser material processing with a special emphasis on the dynamic aspects of laser beam-surface interaction, which include the links between the laser material removal and the resulting material motion. In view of laser material processing, a laser beam is not only considered as a tool but also as a generator of information about the material transformation. The information is retained and conveyed by different kinds of optically induced mechanical waves. Several generation/detection schemes have been developed to extract this information, especially in the field of non-destructive material evaluation. Blast and acoustic waves, which propagate in the air surrounding the work-piece, have been studied using microphone detection as well as various setups of the laser beam deflection probe. Stress waves propagating through the work-piece have been studied using piezoelectric transducers and laser interferometers.

  6. Lateral interactions and non-equilibrium in surface kinetics

    Science.gov (United States)

    Menzel, Dietrich

    2016-08-01

    Work modelling reactions between surface species frequently use Langmuir kinetics, assuming that the layer is in internal equilibrium, and that the chemical potential of adsorbates corresponds to that of an ideal gas. Coverage dependences of reacting species and of site blocking are usually treated with simple power law coverage dependences (linear in the simplest case), neglecting that lateral interactions are strong in adsorbate and co-adsorbate layers which may influence kinetics considerably. My research group has in the past investigated many co-adsorbate systems and simple reactions in them. We have collected a number of examples where strong deviations from simple coverage dependences exist, in blocking, promoting, and selecting reactions. Interactions can range from those between next neighbors to larger distances, and can be quite complex. In addition, internal equilibrium in the layer as well as equilibrium distributions over product degrees of freedom can be violated. The latter effect leads to non-equipartition of energy over molecular degrees of freedom (for products) or non-equal response to those of reactants. While such behavior can usually be described by dynamic or kinetic models, the deeper reasons require detailed theoretical analysis. Here, a selection of such cases is reviewed to exemplify these points.

  7. The shear-force/ultrasonic near-field microscope: a nanometrology tool for surface science and technology

    Science.gov (United States)

    La Rosa, A.; Li, N.; Asante, K.

    2005-11-01

    This paper describes recent results obtained with the Ultrasonic/Shear-Force Microscope (SUNM), an analytical tool suitable for investigating the quite different dynamic displayed by fluid-like films when subjected to mesoscopic confinement and while in intimate contact with two sliding solid boundaries. The SUNM uses two sensory modules to concurrently but independently monitor the effects that fluid-mediated interactions exert on two sliding bodies: the microscope's sharp probe (attached to a piezoelectric sensor) and the analyzed sample (attached to an ultrasonic transducer). This dual capability allows correlating the fluid-like film's viscoelastic properties with changes in the probe's resonance frequency and the generation of sound. A detailed monitoring of sliding friction by ultrasonic means and with nanometer resolution is unprecedented, which opens potential uses of the versatile microscope as a surface and subsurface material characterization tool. As a surface metrology tool, the SUNM presents a potential impact in diverse areas ranging from fundamental studies of nanotribology, confinement-driven solid to liquid phase transformation of polymer films, characterization of industrial lubricants, and the study of elastic properties of bio-membranes. As a sub-surface metrology tool, the SUNM can be used in the investigation of the elastic properties of low- and high-k dielectric materials, piezoelectric and ferroelectric films, as well as quality control in the construction of micro- and nano-fluidics devices.

  8. A study of structure and properties of molecularly thin methanol film using the modified surface forces apparatus.

    Science.gov (United States)

    Zhao, Gutian; Cai, Di; Wu, Gensheng; Tan, Qiyan; Xiang, Li; Zhang, Yin; Xiang, Nan

    2014-11-01

    A novel approach for studying the adsorption and evaporation processes of molecularly thin methanol film by the modified surface forces apparatus (M-SFA) is reported. This method can be used precisely to measure the thickness, morphology, and mechanical properties of the film confined between two mica surfaces in a real-time manner at gas atmosphere. By observing the adsorption and evaporation processes of the methanol molecule, it is found that the first adsorbed layer of the methanol film on the mica surface behaves as a solid-like structure. The thickness of this layer is measured to be about 3.2 Å, approximately equal to the diameter of a methanol molecule. Besides, this first adsorbed layer can carry normalized loads of more than 5.6 atm due to the carrying capacity conserved by the bond of mica-OH. The outer layers of the methanol film are further adsorbed with the increase of the exposure time, which are liquid-like and can be easily eliminated out from the substrate. The present study suggests that the interacting mode between hydroxy and mica is of great potential in material science and biomedical systems. © 2014 Wiley Periodicals, Inc.

  9. Covalent and density-controlled surface immobilization of E-cadherin for adhesion force spectroscopy.

    Directory of Open Access Journals (Sweden)

    Dagmar Fichtner

    Full Text Available E-cadherin is a key cell-cell adhesion molecule but the impact of receptor density and the precise contribution of individual cadherin ectodomains in promoting cell adhesion are only incompletely understood. Investigating these mechanisms would benefit from artificial adhesion substrates carrying different cadherin ectodomains at defined surface density. We therefore developed a quantitative E-cadherin surface immobilization protocol based on the SNAP-tag technique. Extracellular (EC fragments of E-cadherin fused to the SNAP-tag were covalently bound to self-assembled monolayers (SAM of thiols carrying benzylguanine (BG head groups. The adhesive functionality of the different E-cadherin surfaces was then assessed using cell spreading assays and single-cell (SCSF and single-molecule (SMSF force spectroscopy. We demonstrate that an E-cadherin construct containing only the first and second outmost EC domain (E1-2 is not sufficient for mediating cell adhesion and yields only low single cadherin-cadherin adhesion forces. In contrast, a construct containing all five EC domains (E1-5 efficiently promotes cell spreading and generates strong single cadherin and cell adhesion forces. By varying the concentration of BG head groups within the SAM we determined a lateral distance of 5-11 nm for optimal E-cadherin functionality. Integrating the results from SCMS and SMSF experiments furthermore demonstrated that the dissolution of E-cadherin adhesion contacts involves a sequential unbinding of individual cadherin receptors rather than the sudden rupture of larger cadherin receptor clusters. Our method of covalent, oriented and density-controlled E-cadherin immobilization thus provides a novel and versatile platform to study molecular mechanisms underlying cadherin-mediated cell adhesion under defined experimental conditions.

  10. Nanoscale fabrication and characterization of chemically modified silicon surfaces using conductive atomic force microscopy in liquids

    Science.gov (United States)

    Kinser, Christopher Reagan

    This dissertation examines the modification and characterization of hydrogen-terminated silicon surfaces in organic liquids. Conductive atomic force microscope (cAFM) lithography is used to fabricate structures with sub-100 nm line width on H:Si(111) in n-alkanes, 1-alkenes, and 1-alkanes. Nanopatterning is accomplished by applying a positive (n-alkanes and 1-alkenes) or a negative (1-alkanes) voltage pulse to the silicon substrate with the cAFM tip connected to ground. The chemical and kinetic behavior of the patterned features is characterized using AFM, lateral force microscopy, time-of-flight secondary ion mass spectroscopy (TOF SIMS), and chemical etching. Features patterned in hexadecane, 1-octadecene, and undecylenic acid methyl ester exhibited chemical and kinetic behavior consistent with AFM field induced oxidation. The oxide features are formed due to capillary condensation of a water meniscus at the AFM tip-sample junction. A space-charge limited growth model is proposed to explain the observed growth kinetics. Surface modifications produced in the presence of neat 1-dodecyne and 1-octadecyne exhibited a reduced lateral force compared to the background H:Si(111) substrate and were resistant to a hydrofluoric acid etch, characteristics which indicate that the patterned features are not due to field induced oxidation and which are consistent with the presence of the methyl-terminated 1-alkyne bound directly to the silicon surface through silicon-carbon bonds. In addition to the cAFM patterned surfaces, full monolayers of undecylenic acid methyl ester (SAM-1) and undec-10-enoic acid 2-bromoethyl ester (SAM-2) were grown on H:Si(111) substrates using ultraviolet light. The structure and chemistry of the monolayers were characterized using AFM, TOF SIMS, X-ray photoelectron spectroscopy (XPS), X-ray reflectivity (XRR), X-ray standing waves (XSW), and X-ray fluorescence (XRF). These combined analyses provide evidence that SAM-1 and SAM-2 form dense monolayers

  11. Interaction and dynamics of ambient water adlayers on graphite probed using AFM voltage nanolithography and electrostatic force microscopy

    International Nuclear Information System (INIS)

    Gowthami, T; Raina, Gargi; Kurra, Narendra

    2014-01-01

    In this work, we report the impact of the interaction and dynamics of increasing ambient water adlayers on etch patterns on a hydrophobic highly oriented pyrolytic graphite (HOPG) surface obtained using atomic force microscopy (AFM) voltage nanolithography in contact mode by applying a positive bias to the sample. The changes in the dimensions of the etch patterns were investigated as a function of the increasing number of water adlayers present on the HOPG, which is varied by changing the time interval since HOPG cleavage. Changes in the width of the etch patterns and the surrounding water droplets were monitored with time, using intermittent-contact-mode AFM. Electrostatic force microscopy (EFM) has been employed to study the charged nature of the etch patterns and the neighboring water film with time. The width of the etch patterns made on freshly cleaved HOPG shows an increase of ∼33% over 48 h, whereas nine-day-old cleaved HOPG shows a 79% increase over the same period. No changes in the dimensions are observed while imaging in a nitrogen atmosphere soon after lithography. In ambient conditions, the EFM phase shift of the patterns shows a large change of ∼84–88% over 30 h. This study demonstrates the effect of the stored electrostatic energy of a polarized ice-like water adlayer, resulting in changes in the dimensions of the etch patterns long after lithography, whereas liquid-like water droplets do not affect the etch patterns. (paper)

  12. Surface topography characterization using an atomic force microscope mounted on a coordinate measuring machine

    DEFF Research Database (Denmark)

    De Chiffre, Leonardo; Hansen, H.N; Kofod, N

    1999-01-01

    The paper describes the construction, testing and use of an integrated system for topographic characterization of fine surfaces on parts having relatively big dimensions. An atomic force microscope (AFM) was mounted on a manual three-coordinate measuring machine (CMM) achieving free positioning...... of the AFM probe in space. This means that the limited measuring range of the AFM (40 mu m x 40 mu m x 2.7 um) can be extended by positioning the AFM probe using the movements of the CMM axes (400 mm x 100 mm x 75 mm). Evaluation of the background noise by determining the Sa value of an optical fiat gave...

  13. Characterization of local hydrophobicity on sapphire (0001) surfaces in aqueous environment by colloidal probe atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wada, Tomoya; Yamazaki, Kenji; Isono, Toshinari; Ogino, Toshio, E-mail: ogino-toshio-rx@ynu.ac.jp

    2017-02-28

    Highlights: • Local hydrophobicity of phase-separated sapphire (0001) surfaces was investigated. • These surfaces are featured by coexistence of hydrophilic and hydrophobic domains. • Each domain was characterized by colloidal probe atomic force microscopy in water. • Both domains can be distinguished by adhesive forces of the probe to the surfaces. • Characterization in aqueous environment is important in bio-applications of sapphire. - Abstract: Sapphire (0001) surfaces exhibit a phase-separation into hydrophobic and hydrophilic domains upon high-temperature annealing, which were previously distinguished by the thickness of adsorbed water layers in air using atomic force microscopy (AFM). To characterize their local surface hydrophobicity in aqueous environment, we used AFM equipped with a colloidal probe and measured the local adhesive force between each sapphire domain and a hydrophilic SiO{sub 2} probe surface, or a hydrophobic polystyrene one. Two data acquisition modes for statistical analyses were used: one is force measurements at different positions of the surface and the other repeated measurement at a fixed position. We found that adhesive force measurements using the polystyrene probe allow us to distinctly separate the hydrophilic and hydrophobic domains. The dispersion in the force measurement data at different positions of the surface is larger than that in the repeated measurements at a fixed position. It indicates that the adhesive force measurement is repeatable although their data dispersion for the measurement positions is relatively large. From these results, we can conclude that the hydrophilic and hydrophobic domains on the sapphire (0001) surfaces are distinguished by a difference in their hydration degrees.

  14. Surface field of forces and protein adsorption behavior of poly(hydroxyethylmethacrylate) films deposited from plasma.

    Science.gov (United States)

    Morra, M; Cassinelli, C

    1995-01-01

    Polymeric films were deposited from hydroxyethylmethacrylate (HEMA) plasma on non-woven poly(butyleneterephtalate) (PBT) filter materials. To test the effect of deposition conditions on surface properties, film were deposited using a constant monomer flow rate and a discharge power ranging from 40-100 W. Surface composition and surface energetics were evaluated by Electron Spectroscopy for Chemical Analysis (ESCA) and contact angle measurement, respectively. Albumin (Alb) and fibrinogen (Fg) adsorption from single protein solutions to the plasma-coated filters was measured. Results illustrate the marked effects of the deposition condition on the surface composition, the surface field of forces, and the protein adsorption behavior. The latter is modeled by the application of the Good-van Oss-Chaudhury theory of Lewis acid-base contribution to interfacial energetics. Materials endowed with widely different properties are obtained from the same monomer and different deposition conditions, a result that must be taken into account both in the production step, to assure constant quality, and in the development of specifically tailored materials.

  15. In situ nanoscale observations of metatorbernite surfaces interacted with aqueous solutions.

    Science.gov (United States)

    Astilleros, José Manuel; Pinto, André Jorge; Gonçalves, Mário A; Sánchez-Pastor, Nuria; Fernández-Díaz, Lurdes

    2013-03-19

    Metatorbernite (Cu(UO(2))(2)(PO(4))(2)·8H(2)O) has been identified in contaminated sediments as a phase controlling the fate of U. Here, we applied atomic force microscopy (AFM) to observe in situ the interaction between metatorbernite cleavage surfaces and flowing aqueous solutions (residence time = 1 min) with different pHs. In contact with deionized water the features of (001) surfaces barely modify. However, changes are remarkable both under acidic and basic conditions. In acidic solutions (pH = 2.5) metatorbernite surface develops a rough altered layer and large pits nucleate on it. The altered layer shows a low adhesion and is removed by the AFM tip during the scanning. The large pits spread rapidly, at few tens of nm/s, indicating a collapse of the structure. The combination of dissolution and the presence of defects in the metatorbernite structure can explain both the collapse process and the alteration of the surfaces under acidic conditions. Other mechanisms such as ion exchange reactions remain speculative. In NaOH solutions (pH = 11.5) metatorbernite dissolves by formation of etch pits bounded by steps parallel to [100], the direction of the most straight periodic bond chains (PBCs) in metatorbernite structure. These steps retreat at ∼0.15 nm/s. Under these conditions dissolution is promoted by the formation of stable uranyl carbonate complexes in solution.

  16. Extraction of user's navigation commands from upper body force interaction in walker assisted gait

    Directory of Open Access Journals (Sweden)

    Pons José L

    2010-08-01

    Full Text Available Abstract Background The advances in technology make possible the incorporation of sensors and actuators in rollators, building safer robots and extending the use of walkers to a more diverse population. This paper presents a new method for the extraction of navigation related components from upper-body force interaction data in walker assisted gait. A filtering architecture is designed to cancel: (i the high-frequency noise caused by vibrations on the walker's structure due to irregularities on the terrain or walker's wheels and (ii the cadence related force components caused by user's trunk oscillations during gait. As a result, a third component related to user's navigation commands is distinguished. Results For the cancelation of high-frequency noise, a Benedict-Bordner g-h filter was designed presenting very low values for Kinematic Tracking Error ((2.035 ± 0.358·10-2 kgf and delay ((1.897 ± 0.3697·101ms. A Fourier Linear Combiner filtering architecture was implemented for the adaptive attenuation of about 80% of the cadence related components' energy from force data. This was done without compromising the information contained in the frequencies close to such notch filters. Conclusions The presented methodology offers an effective cancelation of the undesired components from force data, allowing the system to extract in real-time voluntary user's navigation commands. Based on this real-time identification of voluntary user's commands, a classical approach to the control architecture of the robotic walker is being developed, in order to obtain stable and safe user assisted locomotion.

  17. Tip-Sample Interactions as a Function of Distance on Insulating Surfaces

    Science.gov (United States)

    Hoffmann, Regina

    Recent advances in the measurement methods of scanning force microscopy (SFM) in the dynamic mode allow experimental access to site-specific short range forces. Either the tip is moved to a particular site, or the full three-dimensional frequency shift field of the oscillating tip is recorded while scanning a small surface area. Then the frequency shift is converted to force, and the long-range forces are fit by models and subtracted. The remaining short-range forces measured on a well- known surface CaF2 (111) can be used to learn more about the tip structure and chemical composition. On NaCl (001)-type crystal surfaces, where there is a complete symmetry of the local distribution of the positive and negative charge, the measurement of the force as a function of distance allows to unambiguously identify the positively and negatively charged sublattices on the surface. If additionally, the full three-dimensional force field is measured, information about the chemical nature of the tip-terminating cluster and about lateral forces are obtained. SFM measurements of site-specific force-distance curves further allow a deeper insight into mechanisms of energy dissipation at tips and surfaces.

  18. Experimental Research and Mathematical Modeling of Parameters Effecting on Cutting Force and SurfaceRoughness in CNC Turning Process

    Science.gov (United States)

    Zeqiri, F.; Alkan, M.; Kaya, B.; Toros, S.

    2018-01-01

    In this paper, the effects of cutting parameters on cutting forces and surface roughness based on Taguchi experimental design method are determined. Taguchi L9 orthogonal array is used to investigate the effects of machining parameters. Optimal cutting conditions are determined using the signal/noise (S/N) ratio which is calculated by average surface roughness and cutting force. Using results of analysis, effects of parameters on both average surface roughness and cutting forces are calculated on Minitab 17 using ANOVA method. The material that was investigated is Inconel 625 steel for two cases with heat treatment and without heat treatment. The predicted and calculated values with measurement are very close to each other. Confirmation test of results showed that the Taguchi method was very successful in the optimization of machining parameters for maximum surface roughness and cutting forces in the CNC turning process.

  19. Fabrication Localized Surface Plasmon Resonance sensor chip of gold nanoparticles and detection lipase–osmolytes interaction

    Energy Technology Data Exchange (ETDEWEB)

    Ghodselahi, T., E-mail: t_ghodselahi@yahoo.com [Nano Mabna Iranian Inc., PO Box 1676664116, Tehran (Iran, Islamic Republic of); School of Physics, Institute for Research in Fundamental Sciences, PO Box 19395-5531, Tehran (Iran, Islamic Republic of); Hoornam, S. [Nano Mabna Iranian Inc., PO Box 1676664116, Tehran (Iran, Islamic Republic of); School of Physics, Institute for Research in Fundamental Sciences, PO Box 19395-5531, Tehran (Iran, Islamic Republic of); Department of Science, Central Tehran Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Vesaghi, M.A. [Department of Physics, Sharif University of Technology, PO Box 11365-9161, Tehran (Iran, Islamic Republic of); Ranjbar, B.; Azizi, A. [Department of Biophysics, Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Mobasheri, H. [Laboratory of Membrane Biophysics, Institute of Biochemistry and Biophysics, University of Tehran, PO Box 13145-1384, Tehran (Iran, Islamic Republic of); Biomaterials Research Institute (BRC), University of Tehran, Tehran (Iran, Islamic Republic of)

    2014-09-30

    Highlights: • We synthesized localized surface plasmon resonance sensor of gold nanoparticles by RF-sputtering and RF-PECVD. • LSPR sensor was characterized by TEM, XPS, AFM. • LSPR sensor was utilized to detect interaction between sorbitol and trehalose, with Pesudomonace Cepacia Lipase (PCL). • Unlike to trehalose, sorbitol interacts with the PCL. • Refractive index of PCL was obtained by Mie theory modeling. - Abstract: Co-deposition of RF-sputtering and RF-PECVD from acetylene gas and Au target were used to prepare sensor chip of gold nanoparticles (Au NPs). Deposition conditions were optimized to reach a Localized Surface Plasmon Resonance (LSPR) sensor chip of Au NPs with particle size less than 10 nm. The RF power was set at 180 W and the initial gas pressure was set at 0.035 mbar. Transmission Electron Microscopy (TEM) images and Atomic Force Microscopy (AFM) data were used to investigate particles size and surface morphology of LSPR sensor chip. The Au and C content of the LSPR sensor chip of Au NPs was obtained from X-ray photoelectron spectroscopy (XPS). The hydrogenated amorphous carbon (a-C:H) thin film was used as intermediate material to immobilize Au NPs on the SiO{sub 2} substrate. The interaction between two types of osmolytes, i.e. sorbitol and trehalose, with Pseudomonas cepacia lipase (PCL) were detected by the prepared LSPR biosensor chip. The detection mechanism is based on LSPR spectroscopy in which the wavelength of absorption peak is sensitive to the refractive index of the environment of the Au NPs. This mechanism eliminates the use of a probe or immobilization of PCL on the Au NPs of LSPR sensor chip. The interaction between PCL and osmolytes can change refractive index of the mixture or solution. We found that unlike to trehalose, sorbitol interacts with the PCL. This interaction increases refractive index of the PCL and sorbitol mixture. Refractive index of PCL in the presence of different concentration of sorbitol was

  20. Micro and nanostructural characterization of surfaces and interfaces of Portland cement mortars using atomic force microscopy

    International Nuclear Information System (INIS)

    Barreto, M.F.O.; Brandao, P.R.G.

    2014-01-01

    The characterization of Portland cement mortars is very important in the study the interfaces and surfaces that make up the system grout/ceramic block. In this sense, scanning electron microscopy and energy-dispersive (X-ray) spectrometer are important tools in investigating the morphology and chemical aspects. However, more detailed topographic information can be necessary in the characterization process. In this work, the aim was to characterize topographically surfaces and interfaces of mortars applied onto ceramic blocks. This has been accomplished by using the atomic force microscope (AFM) - MFP-3D-SA Asylum Research. To date, the results obtained from this research show that the characterization of cementitious materials with the help of AFM has an important contribution in the investigation and differentiation of hydrated calcium silicates (CSH), calcium hydroxide (Ca(OH)2, ettringite and calcium carbonate by providing morphological and micro topographical data, which are extremely important and reliable for the understanding of cementitious materials. (author)

  1. Surface morphology study on CdZnTe crystals by atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Azoulay, M.; George, M.A.; Burger, A.; Collins, W.E.; Silberman, E. [Fisk Univ., Nashville, TN (United States)

    1993-03-01

    The study of the crystal surface morphology of CdZnTe is important for the understanding of the fundamentals of crystal growth in order to improve the crystal quality which is essential in applications such as substrates for epitaxy or performance of devices, i.e., room temperature nuclear spectrometers. We present a first atomic force microscopy study on CdZnTe. Cleaved (110) surfaces were imaged in the ambient and an atomic layer step structure was revealed. The effects of thermal annealing on the atomic steps together with Te precipitation along these steps are discussed in terms of deformation due to stress relief and the diffusion of tellurium precipitates. 12 refs., 3 figs.

  2. Interaction between Palladium Nanoparticles and Surface-Modified Carbon Nanotubes: Role of Surface Functionalities

    DEFF Research Database (Denmark)

    Zhang, Bingsen; Shao, Lidong; Zhang, Wei

    2014-01-01

    degrees C. We focus on probing the effects of oxygen and nitrogen-containing functional groups on supported palladium nanoparticles (NPs) in the model catalytic system. The stability of palladium NPs supported on CNTs depends strongly on the surface properties of CNTs. Moreover, the oxygen...... feature, instability, and subtle response of the components upon application of an external field. Herein, we use insitu TEM, electron energy loss spectroscopy, and X-ray photoelectron spectroscopy techniques to record the interaction in palladium on carbon nanotubes (CNTs) from room temperature to 600...

  3. Conformational study of protein interactions with hydrogen-passivated amorphous silicon surfaces: Effect of pH

    Science.gov (United States)

    Brahmi, Yamina; Filali, Larbi; Sib, Jamal Dine; Bouhekka, Ahmed; Benlakehal, Djamel; Bouizem, Yahya; Kebab, Aissa; Chahed, Larbi

    2017-11-01

    The adsorption of Bovine Serum Albumin (BSA) proteins on amorphous silicon (a-Si) surfaces was studied with respect to solution pH. Thin films of a-Si were deposited using radio-frequency magnetron sputtering at room temperature and then treated in a hydrogen ambient to form a hydrogenated a-Si surface layer (a-Si:H). The interactions of the as-deposited and hydrogenated surfaces with the proteins at neutral, acidic, and basic environments was probed by means of Fourier transform infrared attenuated total reflection (FTIR-ATR) spectroscopy, Spectroscopic Ellipsometry (SE), and Atomic Force Microscopy (AFM), to study the influence of the charge of proteins on their adsorption and conformation on the a-Si:H surface, compared with the a-Si surface. The results show that the charge of the proteins has a significant effect on their interactions with these two substrates but in dissimilar ways. For the as-deposited substrate, these interactions are predictably coulombic since the surface is charged. For the hydrogenated substrate, the adsorption of the proteins depends on their conformation which is heavily affected by pH, and the size of their footprint (adsorption mode) on the surface.

  4. Probing viscoelastic surfaces with bimodal tapping-mode atomic force microscopy: Underlying physics and observables for a standard linear solid model.

    Science.gov (United States)

    Solares, Santiago D

    2014-01-01

    This paper presents computational simulations of single-mode and bimodal atomic force microscopy (AFM) with particular focus on the viscoelastic interactions occurring during tip-sample impact. The surface is modeled by using a standard linear solid model, which is the simplest system that can reproduce creep compliance and stress relaxation, which are fundamental behaviors exhibited by viscoelastic surfaces. The relaxation of the surface in combination with the complexities of bimodal tip-sample impacts gives rise to unique dynamic behaviors that have important consequences with regards to the acquisition of quantitative relationships between the sample properties and the AFM observables. The physics of the tip-sample interactions and its effect on the observables are illustrated and discussed, and a brief research outlook on viscoelasticity measurement with intermittent-contact AFM is provided.

  5. Black carbon aerosols over the Himalayas: direct and surface albedo forcing

    Directory of Open Access Journals (Sweden)

    Vijayakumar S. Nair

    2013-09-01

    Full Text Available Absorbing aerosols such as black carbon (BC or dust over high-altitude Himalayan regions have potential implications on the regional climate and hydrological cycle over South Asia. Making use of extensive measurements of atmospheric BC from several Himalayan stations, an assessment of radiative forcing due to direct and snow-albedo darkening is examined. Generally, BC concentration in the atmosphere peaks during pre-monsoon season over the Himalayas and the climatological mean of atmospheric BC over Hanle (western Himalayas, 4.5 km msl and Nepal Climate Observatory-Pyramid (central Himalayas, 5 km msl are 106±27 ng m−3 and 190±95 ng m−3, respectively. Based on the optical and physical properties of composite aerosols measured at Hanle, clear sky direct radiative forcing (DRF at the top of the atmosphere is estimated as 1.69 W m−2 over snow surface and −1.54 W m−2 over sandy surface during pre-monsoon season. The estimated amount of BC in the snow varied from 117 to 1.7 µg kg−1 for wide range of dry deposition velocities (0.01–0.054 cm s−1 of BC, snow depth (2–10 cm and snow densities (195–512 kg m−3. Using a size-resolved wet scavenging parametrisation, the amount of BC on snow due to wet scavenging is estimated as 29 µg kg−1 for an accumulated snow depth of 27 cm. For the range of 10–200 µg kg−1 of BC in snow, the diurnally averaged forcing due to snow darkening has been found to vary from 0.87 to 10.2 W m−2 for fresh snow and from 2.6 to 28.1 W m−2 for the aged snow, which is significantly higher than the DRF. The direct and surface albedo radiative forcing could lead to significant warming over the Himalayas during pre-monsoon.

  6. Evaluating interaction forces between BSA and rabbit anti-BSA in sulphathiazole sodium, tylosin and levofloxacin solution by AFM

    Science.gov (United States)

    Wang, Congzhou; Wang, Jianhua; Deng, Linhong

    2011-11-01

    Protein-protein interactions play crucial roles in numerous biological processes. However, it is still challenging to evaluate the protein-protein interactions, such as antigen and antibody, in the presence of drug molecules in physiological liquid. In this study, the interaction between bovine serum albumin (BSA) and rabbit anti-BSA was investigated using atomic force microscopy (AFM) in the presence of various antimicrobial drugs (sulphathiazole sodium, tylosin and levofloxacin) under physiological condition. The results show that increasing the concentration of tylosin decreased the single-molecule-specific force between BSA and rabbit anti-BSA. As for sulphathiazole sodium, it dramatically decreased the specific force at a certain critical concentration, but increased the nonspecific force as its concentration increasing. In addition, the presence of levofloxacin did not greatly influence either the specific or nonspecific force. Collectively, these results suggest that these three drugs may adopt different mechanisms to affect the interaction force between BSA and rabbit anti-BSA. These findings may enhance our understanding of antigen/antibody binding processes in the presence of drug molecules, and hence indicate that AFM could be helpful in the design and screening of drugs-modulating protein-protein interaction processes.

  7. Analysis of surface roughness and cutting force during turning of Ti6Al4V ELI in dry environment

    Directory of Open Access Journals (Sweden)

    V. G. Sargade

    2016-04-01

    Full Text Available This paper investigates the effect of cutting parameters on the surface roughness and cutting force of titanium alloy Ti-6Al-4V ELI when turning using PVD TiAlN coated tool in dry environment. Taguchi L9 orthogonal array design of experiment was used for the turning experiment 2 factors and 3 levels. Turning parameters studied were cutting speed (50, 65, 80 m/min, feed rate (0.08, 0.15, 0.2 mm/rev and depth of cut 0.5 mm constant. Linear and second order model of the surface roughness and cutting force has been developed in terms of cutting speed and feed. The results show that the feed rate was the most impact factor controlling the cutting force and surface roughness produced. MINITAB 17software was used to develop a linear and second order model of surface roughness and cutting force. Optimum condition was at 66.97 m/min of cutting speed, 0.08 mm/rev of feed rate. Surface roughness 0.57μm and cutting force 54.02 N were obtained at the optimum condition. A good agreement between the experimental and predicted surface roughness and cutting force were observed.

  8. Topographical characterization of Ar-bombarded Si(1 1 1) surfaces by atomic force microscopy

    CERN Document Server

    Niebieskikwiat, D G; Pregliasco, G R; Gayone, J E; Grizzi, O; Sanchez, E A

    2002-01-01

    We used atomic force microscopy to study the topographical changes induced on Si(1 1 1) surfaces by 10-22 keV Ar sup + bombardment. The irradiation was carried on normal to the surface with doses in the 1-60x10 sup 1 sup 6 ions/cm sup 2 range. We observed a first generation of blisters at a critical dose around 3x10 sup 1 sup 6 ions/cm sup 2 , which flakes off at 19x10 sup 1 sup 6 ions/cm sup 2 , and a second generation of smaller blisters between 35 and 45x10 sup 1 sup 6 ions/cm sup 2. Measurements of the mean surface height show that at low irradiation doses the surface inflates because of voids produced by Ar sup + implantation. For doses greater than 20x10 sup 1 sup 6 Ar sup + /cm sup 2 the height decreases linearly because of sputtering, with a slope corresponding to a sputtering yield of 1.4. Finally, we present electron spectra produced during grazing proton bombardment of samples whose topography has been modified by Ar irradiation.

  9. Interaction of positron beams with thin silver foils and surfaces

    International Nuclear Information System (INIS)

    Rysholt Poulsen, M.

    1994-01-01

    Experimental investigations of positron interactions with solid silver and the necessary platform to analyse the data have been presented. The main objective was to study Ps formation at a Ag(100) surface. The different ingredients of the scenario, including thermalization and diffusion of positrons and emission of Ps, were analysed and quantified in whatever way appropriate. The scattering and possible thermalization were described. The parametrization of Monte-Carlo simulated implantation profiles for semi-infinite materials were presented and the applicability of such profiles to thin foils assessed. The latter was done in conjunction with an analysis of experimental data on thermalization and diffusion in 1900 Aa Ag(100) foils. The necessity for MC simulated rather than parametrized implantation profiles was argued. The velocity of thermally desorbed Ps from a Ag(100) surface at ∼800 K appeared to obey and one-dimensional Maxwell Boltzmann distribution multiplied by a velocity dependent factor. More experimental investigations are needed before firm conclusions can be made on the nature of the emission process. The velocity distribution, though, was found to be near-thermal and indicative of the sample temperature. It has been shown that positrons can be converted into Ps atoms in the transmission geometry of a thin 1900 Aa Ag(100) foil with a high efficiency. Furthermore, 61% of the emitted Ps will have a mean velocity of v z =1.2x10 5 m/sec and 39% will have a maximum kinetic energy of 1.5 eV (v z =5.1x10 5 m/sec) at a foil temperature of 800 K, all velocities that are suitable for producing a 'dense' Ps gas target. (EG) 12 refs

  10. Surface and interfacial interactions of multilayer graphitic structures with local environment

    Energy Technology Data Exchange (ETDEWEB)

    Mazzocco, R. [Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom); Robinson, B.J., E-mail: b.j.robinson@lancaster.ac.uk [Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom); Rabot, C. [CEA-LETI-Minatec Campus, 17 rue des Martyrs, 38054 Grenoble Cedex 09 (France); Delamoreanu, A. [Microelectronics Technology Laboratory (LTM), Joseph Fourier University, French National Research Center (CNRS), 17 Avenue des Martyrs, 38054 Grenoble Cedex 9 (France); Zenasni, A. [CEA-LETI-Minatec Campus, 17 rue des Martyrs, 38054 Grenoble Cedex 09 (France); Dickinson, J.W.; Boxall, C. [Department of Engineering, Lancaster University, Lancaster LA1 4YR (United Kingdom); Kolosov, O.V. [Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom)

    2015-06-30

    In order to exploit the potential of graphene in next-generation devices, such as supercapacitors, rechargeable batteries, displays and ultrathin sensors, it is crucial to understand the solvent interactions with the graphene surface and interlayers, especially where the latter may be in competition with the former, in the medium of application deployment. In this report, we combine quartz crystal microbalance (QCM) and ultrasonic force microscopy methods to investigate the changes in the film–substrate and film–environment interfaces of graphene and graphene oxide films, produced by diverse scalable routes, in both polar (deionised water) and non-polar (dodecane) liquid and vapour environments. In polar liquid environments, we observe nanobubble adsorption/desorption on the graphene film corresponding to a surface coverage of up to 20%. As no comparable behaviour is observed for non-polar environment, we conclude that nanobubble formation is directly due to the hydrophobic nature of graphene with direct consequences for electrode structures immersed in electrolyte solutions. The amount of water adsorbed by the graphene films was found to vary considerably from 0.012 monolayers of water per monolayer of reduced graphene oxide to 0.231 monolayers of water per monolayer of carbon diffusion growth graphene. This is supported by direct nanomechanical mapping of the films immersed in water where an increased variation of local stiffness suggests water propagation within the film and/or between the film and substrate. Transferred film thickness calculations performed for QCM, atomic force microscopy topography and optical transmission measurements, returns results an order of magnitude larger (46 ± 1 layers) than Raman spectroscopy (1 - 2 graphene layers) on pristine pre-transferred films due to contamination during transfer and possible turbostratic structures of large areas. - Highlights: • Exploring interaction of graphene films with polar and nonpolar liquids

  11. Water on hydrophobic surfaces: Mechanistic modeling of hydrophobic interaction chromatography.

    Science.gov (United States)

    Wang, Gang; Hahn, Tobias; Hubbuch, Jürgen

    2016-09-23

    Mechanistic models are successfully used for protein purification process development as shown for ion-exchange column chromatography (IEX). Modeling and simulation of hydrophobic interaction chromatography (HIC) in the column mode has been seldom reported. As a combination of these two techniques is often encountered in biopharmaceutical purification steps, accurate modeling of protein adsorption in HIC is a core issue for applying holistic model-based process development, especially in the light of the Quality by Design (QbD) approach. In this work, a new mechanistic isotherm model for HIC is derived by consideration of an equilibrium between well-ordered water molecules and bulk-like ordered water molecules on the hydrophobic surfaces of protein and ligand. The model's capability of describing column chromatography experiments is demonstrated with glucose oxidase, bovine serum albumin (BSA), and lysozyme on Capto™ Phenyl (high sub) as model system. After model calibration from chromatograms of bind-and-elute experiments, results were validated with batch isotherms and prediction of further gradient elution chromatograms. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Separation and concentration of natural products by fast forced adsorption using well-dispersed velvet-like graphitic carbon nitride with response surface methodology optimisation.

    Science.gov (United States)

    Ding, Xinru; Zhu, Jun; Zhang, Yue; Xia, Qian; Bi, Wentao; Yang, Xiaodi; Yang, Jinfei

    2016-07-01

    Well-dispersed velvet-like graphitic carbon nitride nanoparticles with a large surface area were prepared and utilized for separation and concentration of bioactive compounds from fruit extracts by fast (20s) forced adsorption. The large surface area, enhanced non-covalent interactions of this nanoparticle with bioactive compounds and good dispersity in different solvents benefited its application as a good sorbent. To evaluate their adsorption capabilities, these carbon nitride nanoparticles were used for separation and concentration of flavonoids from fruit extracts by a forced-adsorption dispersive solid phase extraction method. The combined use of this nanoparticle and our experimental conditions showed excellent precision (3.6-4.7%) and sensitivity (limits of detection (S/N=3): 0.6-3.75ng/mL). This research provides an alternative strategy to prepare suitable sorbents for adsorption, separation and concentration of various compounds from different extracts. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Universal phase and force diagrams for a microbubble or pendant drop in static fluid on a surface

    Science.gov (United States)

    Wei, P. S.; Hsiao, C. C.; Chen, K. Y.

    2008-01-01

    Dimensionless three-dimensional universal phase and lift force diagrams of a microbubble (or pendant drop) in static liquid on a solid surface (or orifice) are presented in this work. Microbubble dynamics has been found to play a vital role in mass, momentum, energy, and concentration transfer rates in contemporary micro- and nanosciences and technologies. In this study, dimensionless phase and force diagrams are introduced by utilizing the analytical solutions of the microbubble shape reported in the literature. It shows that phase and force diagrams can be universally specified by two dimensionless independent parameters, Bond number, and contact angle (or base radius). Based on the presence of an inflection point or neck on the microbubble surface, each diagram exhibits three regions. Growth, detachment, and entrapment of a microbubble can be described by path lines in three regions. The corresponding universal total lift forces include hydrostatic buoyancy, difference in gas, and hydrostatic pressures at the base, capillary pressure, as well as surface tension induced by the variation of circumference, which has not been treated in the literature so far. In the absence of viscous stress and Marangoni force, the total lift force equals surface tension induced by the variation of circumference. The latter can be an attaching or lifting force, depending on whether the state in the distinct regions and contact angle is less than or greater than a critical angle. The critical angle, which is slightly less than the inclination angle at the inflection point, is decreased with increasing Bond number.

  14. The interaction of streptococcal enolase with canine plasminogen: the role of surfaces in complex formation.

    Directory of Open Access Journals (Sweden)

    Vinod Balhara

    Full Text Available The enolase from Streptococcus pyogenes (Str enolase F137L/E363G is a homo-octamer shaped like a donut. Plasminogen (Pgn is a monomeric protein composed of seven discrete separated domains organized into a lock washer. The enolase is known to bind Pgn. In past work we searched for conditions in which the two proteins would bind to one another. The two native proteins in solution would not bind under any of the tried conditions. We found that if the structures were perturbed binding would occur. We stated that only the non-native Str enolase or Pgn would interact such that we could detect binding. We report here the results of a series of dual polarization interferometry (DPI experiments coupled with atomic force microscopy (AFM, isothermal titration calorimetry (ITC, dynamic light scattering (DLS, and fluorescence. We show that the critical condition for forming stable complexes of the two native proteins involves Str enolase binding to a surface. Surfaces that attract Str enolase are a sufficient condition for binding Pgn. Under certain conditions, Pgn adsorbed to a surface will bind Str enolase.

  15. Specific interactions of functionalised gold surfaces with ammonium perchlorate or starch; towards a chemical cartography of their mixture

    Science.gov (United States)

    Mercier, D.; Mercader, C.; Quere, S.; Hairault, L.; Méthivier, C.; Pradier, C. M.

    2012-10-01

    By functionalising gold samples, planar wafers or AFM tips, with an acid- or an amino acid-terminated thiols, mercaptoundecanoic acid (MUA) and homocystein (H-Cyst) respectively, we were able to differentiate the interactions with ammonium perchlorate (AP) and starch (S), two components of a nanocomposition mixture. To do so, the interaction between gold functionalized surfaces and the two targeted compounds have been characterized and quantified by several complementary techniques. Polarisation modulation-infrared spectroscopy (PM-IRRAS), and X-ray photoelectron spectroscopy (XPS), providing chemical analyses of gold surfaces after contacting S or AP, proved that both compounds were retained on MUA or H-Cyst-modified surfaces, but to various extents. Quartz crystal microbalance on-line measurements enabled to monitor the kinetics of interaction and showed distinct differences in the behaviour of MUA and H-Cyst-surfaces towards the two compounds. Having observed that only H-Cyst-modified surfaces enables to get a contrast on the chemical force microscopy (CFM) images, this new result could be well explained by examining the data obtained by combining the above-mentioned surface characterisation techniques.

  16. The influence of local volume forces on surface relaxation of pure metals and alloys: Applications to Ni, Al, Ni3Al

    International Nuclear Information System (INIS)

    Savino, E.J.; Farkas, D.

    1987-11-01

    We present an analysis of the relative influence of the interatomic potential, lattice structure and defect symmetry on the calculated and measured distortion for the free surfaces of alloys and pure metals. In particular, the effect of using local ''volume'' dependent interactions is studied, as opposed to simple pair interatomic forces. The dependence of the relaxation on the lattice structure is examined by comparing pure metals with ordered alloys. A Green function method for surface relaxation is presented and used for the above analysis as well as for studying the influence of different surface symmetries. Examples based on computer simulation of Ni, Al and Ni 3 Al for some surface orientations are presented. (author). 33 refs, 4 figs

  17. Defects in oxide surfaces studied by atomic force and scanning tunneling microscopy

    Directory of Open Access Journals (Sweden)

    Thomas König

    2011-01-01

    Full Text Available Surfaces of thin oxide films were investigated by means of a dual mode NC-AFM/STM. Apart from imaging the surface termination by NC-AFM with atomic resolution, point defects in magnesium oxide on Ag(001 and line defects in aluminum oxide on NiAl(110, respectively, were thoroughly studied. The contact potential was determined by Kelvin probe force microscopy (KPFM and the electronic structure by scanning tunneling spectroscopy (STS. On magnesium oxide, different color centers, i.e., F0, F+, F2+ and divacancies, have different effects on the contact potential. These differences enabled classification and unambiguous differentiation by KPFM. True atomic resolution shows the topography at line defects in aluminum oxide. At these domain boundaries, STS and KPFM verify F2+-like centers, which have been predicted by density functional theory calculations. Thus, by determining the contact potential and the electronic structure with a spatial resolution in the nanometer range, NC-AFM and STM can be successfully applied on thin oxide films beyond imaging the topography of the surface atoms.

  18. Compliment Graphene Oxide Coating on Silk Fiber Surface via Electrostatic Force for Capacitive Humidity Sensor Applications.

    Science.gov (United States)

    Han, Kook In; Kim, Seungdu; Lee, In Gyu; Kim, Jong Pil; Kim, Jung-Ha; Hong, Suck Won; Cho, Byung Jin; Hwang, Wan Sik

    2017-02-19

    Cylindrical silk fiber (SF) was coated with Graphene oxide (GO) for capacitive humidity sensor applications. Negatively charged GO in the solution was attracted to the positively charged SF surface via electrostatic force without any help from adhesive intermediates. The magnitude of the positively charged SF surface was controlled through the static electricity charges created on the SF surface. The GO coating ability on the SF improved as the SF's positive charge increased. The GO-coated SFs at various conditions were characterized using an optical microscope, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Raman spectroscopy, and LCR meter. Unlike the intact SF, the GO-coated SF showed clear response-recovery behavior and well-behaved repeatability when it was exposed to 20% relative humidity (RH) and 90% RH alternatively in a capacitive mode. This approach allows humidity sensors to take advantage of GO's excellent sensing properties and SF's flexibility, expediting the production of flexible, low power consumption devices at relatively low costs.

  19. Compliment Graphene Oxide Coating on Silk Fiber Surface via Electrostatic Force for Capacitive Humidity Sensor Applications

    Directory of Open Access Journals (Sweden)

    Kook In Han

    2017-02-01

    Full Text Available Cylindrical silk fiber (SF was coated with Graphene oxide (GO for capacitive humidity sensor applications. Negatively charged GO in the solution was attracted to the positively charged SF surface via electrostatic force without any help from adhesive intermediates. The magnitude of the positively charged SF surface was controlled through the static electricity charges created on the SF surface. The GO coating ability on the SF improved as the SF’s positive charge increased. The GO-coated SFs at various conditions were characterized using an optical microscope, scanning electron microscopy (SEM, energy-dispersive X-ray spectroscopy (EDS, Raman spectroscopy, and LCR meter. Unlike the intact SF, the GO-coated SF showed clear response-recovery behavior and well-behaved repeatability when it was exposed to 20% relative humidity (RH and 90% RH alternatively in a capacitive mode. This approach allows humidity sensors to take advantage of GO’s excellent sensing properties and SF’s flexibility, expediting the production of flexible, low power consumption devices at relatively low costs.

  20. Probing the surface charge on the basal planes of Kaolinite particles with high resolution Atomic Force Microscopy

    NARCIS (Netherlands)

    Kumar, Naveen; Andersson, M.P.; van den Ende, Henricus T.M.; Mugele, Friedrich Gunther; Sîretanu, Igor

    2017-01-01

    High-resolution atomic force microscopy is used to map the surface charge on the basal planes of kaolinite nanoparticles in an ambient solution of variable pH and NaCl or CaCl2 concentration. Using DLVO theory with charge regulation, we determine from the measured force–distance curves the surface

  1. Curcumin induced nanoscale CD44 molecular redistribution and antigen-antibody interaction on HepG2 cell surface

    Energy Technology Data Exchange (ETDEWEB)

    Wang Mu [Department of Chemistry, Jinan University, 601 Huangpu Road West, Tianhe District, Guangzhou 510632 (China); Ruan Yuxia [Department of Ophthalmology, The First Affiliated Hospital, Jinan University, 601 Huangpu Road West, Tianhe District, Guangzhou 510632 (China); Xing Xiaobo; Chen Qian; Peng, Yuan [Department of Chemistry, Jinan University, 601 Huangpu Road West, Tianhe District, Guangzhou 510632 (China); Cai Jiye, E-mail: tjycai@jnu.edu.cn [Department of Chemistry, Jinan University, 601 Huangpu Road West, Tianhe District, Guangzhou 510632 (China)

    2011-07-04

    Graphical abstract: Highlights: > In this study, we investigate the changes of CD44 expression and distribution on HepG2 cells after curcumin treatment. > We find curcumin is able to change the morphology and ultrastructure of HepG2 cells. > Curcumin can reduce the expression of CD44 molecules and induce the nanoscale molecular redistribution on cell surface. > The binding force between CD44-modified AFM tip and the HepG2 cell surface decreases after curcumin-treatment. - Abstract: The cell surface glycoprotein CD44 was implicated in the progression, metastasis and apoptosis of certain human tumors. In this study, we used atomic force microscope (AFM) to monitor the effect of curcumin on human hepatocellular carcinoma (HepG2) cell surface nanoscale structure. High-resolution imaging revealed that cell morphology and ultrastructure changed a lot after being treated with curcumin. The membrane average roughness increased (10.88 {+-} 4.62 nm to 129.70 {+-} 43.72 nm) and the expression of CD44 decreased (99.79 {+-} 0.16% to 75.14 {+-} 8.37%). Laser scanning confocal microscope (LSCM) imaging showed that CD44 molecules were located on the cell membrane. The florescence intensity in control group was weaker than that in curcumin treated cells. Most of the binding forces between CD44 antibodies and untreated HepG2 cell membrane were around 120-220 pN. After being incubated with curcumin, the major forces focused on 70-150 pN (10 {mu}M curcumin-treated) and 50-120 pN (20 {mu}M curcumin-treated). These results suggested that, as result of nanoscale molecular redistribution, changes of the cell surface were in response to external treatment of curcumin. The combination of AFM and LSCM could be a powerful method to detect the distribution of cell surface molecules and interactions between molecules and their ligands.

  2. HapTip: Displaying Haptic Shear Forces at the Fingertips for Multi-Finger Interaction in Virtual Environments

    Directory of Open Access Journals (Sweden)

    Adrien eGirard

    2016-04-01

    Full Text Available The fingertips are one of the most important and sensitive parts of our body.They are the first stimulated areas of the hand when we interact with our environment.Providing haptic feedback to the fingertips in virtual reality could thus drastically improve perception and interaction with virtual environments.In this paper, we present a modular approach called HapTip to display such haptic sensations at the level of the fingertips.This approach relies on a wearable and compact haptic device able to simulate 2 Degree of Freedom (DoF shear forces on the fingertip with a displacement range of +/- 2 mm. Several modules can be added and used jointly in order to address multi-finger and/or bimanual scenarios in virtual environments.For that purpose, we introduce several haptic rendering techniques to cover different cases of 3D interaction such as touching a rough virtual surface, or feeling the inertia or weight of a virtual object.In order to illustrate the possibilities offered by HapTip, we provide four use cases focused on touching or grasping virtual objects.To validate the efficiency of our approach, we also conducted experiments to assess the tactile perception obtained with HapTip.Our results show that participants can successfully discriminate the directions of the 2 DoF stimulation of our haptic device.We found also that participants could well perceive different weights of virtual objects simulated using two HapTip devices. We believe that HapTip could be used in numerous applications in virtual reality for which 3D manipulation and tactile sensations are often crucial, such as in virtual prototyping or virtual training.

  3. Artificial Intelligence Mechanisms on Interactive Modified Simplex Method with Desirability Function for Optimising Surface Lapping Process

    Directory of Open Access Journals (Sweden)

    Pongchanun Luangpaiboon

    2014-01-01

    Full Text Available A study has been made to optimise the influential parameters of surface lapping process. Lapping time, lapping speed, downward pressure, and charging pressure were chosen from the preliminary studies as parameters to determine process performances in terms of material removal, lap width, and clamp force. The desirability functions of the-nominal-the-best were used to compromise multiple responses into the overall desirability function level or D response. The conventional modified simplex or Nelder-Mead simplex method and the interactive desirability function are performed to optimise online the parameter levels in order to maximise the D response. In order to determine the lapping process parameters effectively, this research then applies two powerful artificial intelligence optimisation mechanisms from harmony search and firefly algorithms. The recommended condition of (lapping time, lapping speed, downward pressure, and charging pressure at (33, 35, 6.0, and 5.0 has been verified by performing confirmation experiments. It showed that the D response level increased to 0.96. When compared with the current operating condition, there is a decrease of the material removal and lap width with the improved process performance indices of 2.01 and 1.14, respectively. Similarly, there is an increase of the clamp force with the improved process performance index of 1.58.

  4. Human-Human Interaction Forces and Interlimb Coordination During Side-by-Side Walking With Hand Contact.

    Science.gov (United States)

    Sylos-Labini, Francesca; d'Avella, Andrea; Lacquaniti, Francesco; Ivanenko, Yury

    2018-01-01

    Handholding can naturally occur between two walkers. When people walk side-by-side, either with or without hand contact, they often synchronize their steps. However, despite the importance of haptic interaction in general and the natural use of hand contact between humans during walking, few studies have investigated forces arising from physical interactions. Eight pairs of adult subjects participated in this study. They walked on side-by-side treadmills at 4 km/h independently and with hand contact. Only hand contact-related sensory information was available for unintentional synchronization, while visual and auditory communication was obstructed. Subjects walked at their natural cadences or following a metronome. Limb kinematics, hand contact 3D interaction forces and EMG activity of 12 upper limb muscles were recorded. Overall, unintentional step frequency locking was observed during about 40% of time in 88% of pairs walking with hand contact. On average, the amplitude of contact arm oscillations decreased while the contralateral (free) arm oscillated in the same way as during normal walking. Interestingly, EMG activity of the shoulder muscles of the contact arm did not decrease, and their synergistic pattern remained similar. The amplitude of interaction forces and of trunk oscillations was similar for synchronized and non-synchronized steps, though the synchronized steps were characterized by significantly more regular orientations of interaction forces. Our results further support the notion that gait synchronization during natural walking is common, and that it may occur through interaction forces. Conservation of the proximal muscle activity of the contact (not oscillating) arm is consistent with neural coupling between cervical and lumbosacral pattern generation circuitries ("quadrupedal" arm-leg coordination) during human gait. Overall, the findings suggest that individuals might integrate force interaction cues to communicate and coordinate steps during

  5. Human-Human Interaction Forces and Interlimb Coordination During Side-by-Side Walking With Hand Contact

    Directory of Open Access Journals (Sweden)

    Francesca Sylos-Labini

    2018-03-01

    Full Text Available Handholding can naturally occur between two walkers. When people walk side-by-side, either with or without hand contact, they often synchronize their steps. However, despite the importance of haptic interaction in general and the natural use of hand contact between humans during walking, few studies have investigated forces arising from physical interactions. Eight pairs of adult subjects participated in this study. They walked on side-by-side treadmills at 4 km/h independently and with hand contact. Only hand contact-related sensory information was available for unintentional synchronization, while visual and auditory communication was obstructed. Subjects walked at their natural cadences or following a metronome. Limb kinematics, hand contact 3D interaction forces and EMG activity of 12 upper limb muscles were recorded. Overall, unintentional step frequency locking was observed during about 40% of time in 88% of pairs walking with hand contact. On average, the amplitude of contact arm oscillations decreased while the contralateral (free arm oscillated in the same way as during normal walking. Interestingly, EMG activity of the shoulder muscles of the contact arm did not decrease, and their synergistic pattern remained similar. The amplitude of interaction forces and of trunk oscillations was similar for synchronized and non-synchronized steps, though the synchronized steps were characterized by significantly more regular orientations of interaction forces. Our results further support the notion that gait synchronization during natural walking is common, and that it may occur through interaction forces. Conservation of the proximal muscle activity of the contact (not oscillating arm is consistent with neural coupling between cervical and lumbosacral pattern generation circuitries (“quadrupedal” arm-leg coordination during human gait. Overall, the findings suggest that individuals might integrate force interaction cues to communicate and

  6. Interaction of lectins with membrane receptors on erythrocyte surfaces.

    Science.gov (United States)

    Sung, L A; Kabat, E A; Chien, S

    1985-08-01

    The interactions of human genotype AO erythrocytes (red blood cells) (RBCs) with N-acetylgalactosamine-reactive lectins isolated from Helix pomatia (HPA) and from Dolichos biflorus (DBA) were studied. Binding curves obtained with the use of tritium-labeled lectins showed that the maximal numbers of lectin molecules capable of binding to human genotype AO RBCs were 3.8 X 10(5) and 2.7 X 10(5) molecules/RBC for HPA and DBA, respectively. The binding of one type of lectin may influence the binding of another type. HPA was found to inhibit the binding of DBA, but not vice versa. The binding of HPA was weakly inhibited by a beta-D-galactose-reactive lectin isolated from Ricinus communis (designated RCA1). Limulus polyphemus lectin (LPA), with specificity for N-acetylneuraminic acid, did not influence the binding of HPA but enhanced the binding of DBA. About 80% of LPA receptors (N-acetylneuraminic acid) were removed from RBC surfaces by neuraminidase treatment. Neuraminidase treatment of RBCs resulted in increases of binding of both HPA and DBA, but through different mechanisms. An equal number (7.6 X 10(5) of new HPA sites were generated on genotypes AO and OO RBCs by neuraminidase treatment, and these new sites accounted for the enhancement (AO cells) and appearance (OO cells) of hemagglutinability by HPA. Neuraminidase treatment did not generate new DBA sites, but increased the DBA affinity for the existing receptors; as a result, genotype AO cells increased their hemagglutinability by DBA, while OO cells remained unagglutinable. The use of RBCs of different genotypes in binding assays with 3H-labeled lectins of known specificities provides an experimental system for studying cell-cell recognition and association.

  7. Tribological properties investigation of the thermoplastic elastomers surface with the AFM lateral forces mode

    Science.gov (United States)

    Kuznetsova, T. A.; Zubar, T. I.; Lapitskaya, V. A.; Sudzilouskaya, K. A.; Chizhik, S. A.; Didenko, A. L.; Svetlichnyi, V. M.; Vylegzhanina, M. E.; Kudryavtsev, V. V.; Sukhanova, T. E.

    2017-10-01

    The series of new thermoplastic elastomer films based on copoly(urethane-imide)s (coPUI)s and nanocomposites containing from 1 to 10 wt. % carbon nanofillers of different morphology (single-walled carbon nanotubes, carbon nanofibers, and graphene) as well as WS2 and WSe2 nanoparticles, were prepared and investigated by atomic force microscopy in contact mode. The friction coefficient (Cfr) on the films surfaces under conditions of true slip was determined both in one scan field and with multiple scans (200-400) in one place. The measurements were carried out at room temperature and at a heating up to 120°C. It is shown that at heating up to 75-85°C, the friction coefficient of some coPUI decreases significantly. The same effect can be achieved also after 100 scans during multi-scan testing at 20°C.

  8. Static and kinetic friction force and surface roughness of different archwire-bracket sliding contacts.

    Science.gov (United States)

    Carrion-Vilches, Francisco J; Bermudez, María-Dolores; Fructuoso, Paula

    2015-01-01

    The aim of this study was to determine the static and kinetic friction forces of the contact bracket-archwire with different dental material compositions in order to select those materials with lower resistance to sliding. We carried out sliding friction tests by means of a universal testing machine following an experimental procedure as described in ASTM D1894 standard. We determined the static and kinetic friction forces under dry and lubricating conditions using an artificial saliva solution at 36.5ºC. The bracket-archwire pairs studied were: stainless steel-stainless steel; stainless steel-glass fiber composite; stainless steel-Nitinol 60; sapphire-stainless steel; sapphire-glass fiber composite; and sapphire-Nitinol 60. The best performance is obtained for Nitinol 60 archwire sliding against a stainless steel bracket, both under dry and lubricated conditions. These results are in agreement with the low surface roughness of Nitinol 60 with respect to the glass fiber composite archwire. The results described here contribute to establishing selection criteria for materials for dental archwire-brackets.

  9. Effect of SP-C on surface potential distribution in pulmonary surfactant: Atomic force microscopy and Kelvin probe force microscopy study

    International Nuclear Information System (INIS)

    Hane, Francis; Moores, Brad; Amrein, Matthias; Leonenko, Zoya

    2009-01-01

    The air-lung interface is covered by a molecular film of pulmonary surfactant (PS). The major function of the film is to reduce the surface tension of the lung's air-liquid interface, providing stability to the alveolar structure and reducing the work of breathing. Earlier we have shown that function of bovine lipid extract surfactant (BLES) is related to the specific molecular architecture of surfactant films. Defined molecular arrangement of the lipids and proteins of the surfactant film also give rise to a local highly variable electrical surface potential of the interface. In this work we investigated a simple model of artificial lung surfactant consisting of DPPC, eggPG, and surfactant protein C (SP-C). Effects of surface compression and the presence of SP-C on the monolayer structure and surface potential distribution were investigated using atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM). We show that topography and locally variable surface potential of DPPC-eggPG lipid mixture are similar to those of pulmonary surfactant BLES in the presence of SP-C and differ in surface potential when SP-C is absent.

  10. Spatiotemporal variation of surface shortwave forcing from fire-induced albedo change in interior Alaska

    Science.gov (United States)

    Huang, Shengli; Dahal, Devendra; Liu, Heping; Jin, Suming; Young, Claudia J.; Liu, Shuang; Liu, Shu-Guang

    2015-01-01

    The albedo change caused by both fires and subsequent succession is spatially heterogeneous, leading to the need to assess the spatiotemporal variation of surface shortwave forcing (SSF) as a component to quantify the climate impacts of high-latitude fires. We used an image reconstruction approach to compare postfire albedo with the albedo assuming fires had not occurred. Combining the fire-caused albedo change from the 2001-2010 fires in interior Alaska and the monthly surface incoming solar radiation, we examined the spatiotemporal variation of SSF in the early successional stage of around 10 years. Our results showed that while postfire albedo generally increased in fall, winter, and spring, some burned areas could show an albedo decrease during these seasons. In summer, the albedo increased for several years and then declined again. The spring SSF distribution did not show a latitudinal decrease from south to north as previously reported. The results also indicated that although the SSF is usually largely negative in the early successional years, it may not be significant during the first postfire year. The annual 2005-2010 SSF for the 2004 fire scars was -1.30, -4.40, -3.31, -4.00, -3.42, and -2.47 Wm-2. The integrated annual SSF map showed significant spatial variation with a mean of -3.15 Wm-2 and a standard deviation of 3.26 Wm-2, 16% of burned areas having positive SSF. Our results suggest that boreal deciduous fires would be less positive for climate change than boreal evergreen fires. Future research is needed to comprehensively investigate the spatiotemporal radiative and non-radiative forcings to determine the effect of boreal fires on climate.

  11. Driving forces for the adsorption of a His-tag Chagas antigen. A rational approach to design bio-functional surfaces.

    Science.gov (United States)

    Valenti, Laura E; Smania, Andrea M; De Pauli, Carlos P; Giacomelli, Carla E

    2013-12-01

    In order to rationally design a bio-functional surface based on the adsorption of a His-tag antigen, three requirements have to be considered: the bio-recognition element, the driving forces for the adsorption process and the detection mode of the bio-recognition event. This work is focused on the study of the adsorption mechanism of the His-tag H49 Chagas antigen on Ni(II) modified substrates. In order to construct the bio-functional surface, the gen of the H49 Chagas antigen was modified to incorporate His6 moiety at the N-terminal (His6-H49). Then, its physical adsorption and bio-affinity interaction with the solid substrate was studied by reflectometry. Besides His-Ni(II) bio-affinity interactions, His6-H49 was also physically adsorbed on Ni(II) modified substrates, leading to randomly oriented antigens. These loosely attached bio-molecules were partially removed using conditions of electrostatic repulsion. On the other hand, bio-affinity interactions, resulting in site-oriented molecules on the substrate, were only removable by specific competitors for Ni(II) surface sites. Finally, the surface bio-activity was determined from the peak separations of voltammetry waves due to the change of the electron transfer kinetics of a redox probe through the bio-functional surface (working electrode). Copyright © 2013 Elsevier B.V. All rights reserved.

  12. Modeling South America regional smoke plume: aerosol optical depth variability and shortwave surface forcing

    Science.gov (United States)

    Rosário, N. E.; Longo, K. M.; Freitas, S. R.; Yamasoe, M. A.; Fonseca, R. M.

    2012-07-01

    Amazon Basin produced a radiative forcing efficiency (RFE) of -158 W m-2/AOD550 nm at noon. This value is in between -154 W m-2/AOD550 nm and -187 W m-2/AOD550 nm, the range obtained when spatial varying optical models were considered. The average 24 h surface forcing over the biomass burning season varied from -55 W m-2 close to smoke sources in the southern part of the Amazon Basin and cerrado to -10 W m-2 in remote regions of the Southeast Brazilian coast.

  13. Interacting with the biomolecular solvent accessible surface via a haptic feedback device

    Directory of Open Access Journals (Sweden)

    Hayward Steven

    2009-10-01

    Full Text Available Abstract Background From the 1950s computer based renderings of molecules have been produced to aid researchers in their understanding of biomolecular structure and function. A major consideration for any molecular graphics software is the ability to visualise the three dimensional structure of the molecule. Traditionally, this was accomplished via stereoscopic pairs of images and later realised with three dimensional display technologies. Using a haptic feedback device in combination with molecular graphics has the potential to enhance three dimensional visualisation. Although haptic feedback devices have been used to feel the interaction forces during molecular docking they have not been used explicitly as an aid to visualisation. Results A haptic rendering application for biomolecular visualisation has been developed that allows the user to gain three-dimensional awareness of the shape of a biomolecule. By using a water molecule as the probe, modelled as an oxygen atom having hard-sphere interactions with the biomolecule, the process of exploration has the further benefit of being able to determine regions on the molecular surface that are accessible to the solvent. This gives insight into how awkward it is for a water molecule to gain access to or escape from channels and cavities, indicating possible entropic bottlenecks. In the case of liver alcohol dehydrogenase bound to the inhibitor SAD, it was found that there is a channel just wide enough for a single water molecule to pass through. Placing the probe coincident with crystallographic water molecules suggests that they are sometimes located within small pockets that provide a sterically stable environment irrespective of hydrogen bonding considerations. Conclusion By using the software, named HaptiMol ISAS (available from http://www.haptimol.co.uk, one can explore the accessible surface of biomolecules using a three-dimensional input device to gain insights into the shape and water

  14. Superparamagnetic bead interactions with functionalized surfaces characterized by an immunomicroarray

    DEFF Research Database (Denmark)

    Skottrup, Peter Durand; Hansen, Mikkel Fougt; Moresco, Jacob Lange

    2010-01-01

    an immunomicroarray for systematic studies of the binding properties of 10 different micro-/nano-sized streptavidin-functionalized beads to a biotin substrate immobilized on SiO2 with or without surface modification SiO2 surface cleaning, immobilized substrate concentration and surface blocking conditions were...

  15. Multi-dimensional modelling of electrostatic force distance curve over dielectric surface: Influence of tip geometry and correlation with experiment

    Energy Technology Data Exchange (ETDEWEB)

    Boularas, A., E-mail: boularas@laplace.univ-tlse.fr; Baudoin, F.; Villeneuve-Faure, C. [LAPLACE (Laboratoire Plasma et Conversion d' Energie), Université de Toulouse, UPS, INPT, 118 route de Narbonne, 31062 Toulouse cedex 9 (France); Clain, S. [Universidade do Minho, Centro de Matemática, Campus de Gualtar, 4710 - 057 Braga (Portugal); Université Paul Sabatier, Institut de Mathématiques de Toulouse, 31062 Toulouse (France); Teyssedre, G. [LAPLACE (Laboratoire Plasma et Conversion d' Energie), Université de Toulouse, UPS, INPT, 118 route de Narbonne, 31062 Toulouse cedex 9 (France); CNRS, LAPLACE, F-31071 Toulouse (France)

    2014-08-28

    Electric Force-Distance Curves (EFDC) is one of the ways whereby electrical charges trapped at the surface of dielectric materials can be probed. To reach a quantitative analysis of stored charge quantities, measurements using an Atomic Force Microscope (AFM) must go with an appropriate simulation of electrostatic forces at play in the method. This is the objective of this work, where simulation results for the electrostatic force between an AFM sensor and the dielectric surface are presented for different bias voltages on the tip. The aim is to analyse force-distance curves modification induced by electrostatic charges. The sensor is composed by a cantilever supporting a pyramidal tip terminated by a spherical apex. The contribution to force from cantilever is neglected here. A model of force curve has been developed using the Finite Volume Method. The scheme is based on the Polynomial Reconstruction Operator—PRO-scheme. First results of the computation of electrostatic force for different tip–sample distances (from 0 to 600 nm) and for different DC voltages applied to the tip (6 to 20 V) are shown and compared with experimental data in order to validate our approach.

  16. Interactions between fluvial forces and vegetation size, density and morphology influence plant mortality during experimental floods

    Science.gov (United States)

    Stella, J. C.; Kui, L.; Manners, R.; Wilcox, A. C.; Lightbody, A.; Sklar, L. S.

    2015-12-01

    Introduction and methods Fluvial disturbance is a key driver of riparian vegetation dynamics in river corridors. Despite an increasing understanding of ecohydraulic interactions between plants and fluvial forces, the interactive influences of plant morphology and sediment supply on plant mortality, a key demographic factor, are largely unknown. To better understand these processes, we designed and conducted a series of flume experiments to: (1) quantify effects of plant traits that interact with flow and sediment transport on plant loss to scour during floods; and (2) predict plant dislodgement for different species across a range of plant sizes, patch densities, and sediment condition (equilibrium transport versus sediment deficit). We ran ten experimental floods in a 28 m long × 0.6 m wide × 0.71 m tall flume, using live, 1-3 year-old tamarisk and cottonwood seedlings with contrasting morphologies with varied combinations of size and density. Results and discussion Both sediment supply and plant traits (morphology and composition) have significant impacts on plant vulnerability during floods. Sediment deficit resulted in bed degradation and a 35% greater risk of plant loss compared to equilibrium sediment conditions. The probability of plant dislodgement in sparse patches was 4.5 times greater than in dense patches. Tamarisk plants and patches had greater frontal area, basal diameter and longer roots compared to cottonwood across all seedling heights. These traits, as well as its lower crown position reduced tamarisk's vulnerability to scour by 75%. Compared with cottonwood, tamarisk exhibits better resistance to floods, due to its greater root biomass and longer roots that stabilize soil, and its greater frontal area and lower crown that effectively trap sediment. These traits likely contribute to riverscape-scale changes in channel morphology that are evident where tamarisk has invaded native riparian communities, and explain the persistence of tamarisk

  17. Groundwater–surface water interactions in wetlands for integrated water resources management (preface)

    NARCIS (Netherlands)

    Schot, P.P.; Winter, T.C.

    2006-01-01

    Groundwater–surface water interactions constitute an important link between wetlands and the surrounding catchment. Wetlands may develop in topographic lows where groundwater exfiltrates. This water has its functions for ecological processes within the wetland, while surface water outflow from

  18. The surface chemistry of metal-oxygen interactions

    DEFF Research Database (Denmark)

    Stokbro, Kurt; Baroni, Stefano

    1997-01-01

    We report on a computational study of the clean and oxygen-covered Rh(110) surface, based on density-functional theory within the local-density approximation. We have used plane-wave basis sets and Vanderbilt ultra-soft pseudopotentials. For the clean surface, we present results for the equilibrium...... structure, surface energy and surface stress of the unreconstructed and (1 x 2) reconstructed structures. For the oxygen-covered surface we have performed a geometry optimization at 0.5, 1, and 2 monolayer oxygen coverages, and we present results for the equilibrium configurations, workfunctions and oxygen...

  19. Hydrogen interactions with polycrystalline and with deposited titanium surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Azoulay, A. [Ben-Gurion Univ. of the Negev, Beersheba (Israel); Shamir, N. [Nuclear Research Center-Negev, PO Box 9001, Beer Sheva (Israel); Fromm, E. [Max-Planck Institute fuer Metallforschung, Stuttgart (Germany); Szokefalvi-Nagy, A. [Max-Planck Institute fuer Metallforschung, Stuttgart (Germany); Mintz, M.H. [Ben-Gurion Univ. of the Negev, Beersheba (Israel)]|[Nuclear Research Center-Negev, PO Box 9001, Beer Sheva (Israel)

    1997-02-15

    The room temperature kinetics of hydrogen chemisorption and adsorption on polycrystalline and on deposited (sputter-deposited and evaporation-deposited) titanium surfaces were studied. Measurements of hydrogen surface accumulation were performed in a combined surface analyses system incorporating direct recoils spectrometry and Auger electron spectroscopy (AES). There, three different types of surface cleaning procedure were applied: heat-flashing, sputtering and sputter-deposition of titanium on a polycrystalline titanium substrate. The surface chemisorption kinetics obtained for the deposited samples were compared with the total kinetics of the gas phase consumption, performed in a volumetric Wagener system. From this comparison it was possible to distinguish between topmost surface chemisorption and subsurface (or bulk) absorption kinetics. It was concluded that, for all types of surface studied, hydrogen chemisorbed according to a Langmuir-type random two-sites chemisorption model, with high (close to unity) zero-coverage sticking probabilities. The only difference between these surfaces was in their roughness factors, which increased going from the heat-flashed, through the sputtered, to the deposited surfaces. Following the initial stage of a chemisorbed surface layer formation, constant-rate absorption of hydrogen proceeded over a very wide range of exposures (greater than 10{sup 4} Langmuirs). The accommodation probability of hydrogen during this linear stage was about 10{sup -2}. It is possible that this absorption process is controlled by the chemisorption of the H{sub 2} on the surface hydride phase, formed by the earlier hydrogen chemisorption. (orig.)

  20. Fabrication of robot head module using contact resistance force sensor for human robot interaction and its evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dong Ki; Kim, Jong Ho [Korea Reserch Institute of Standards and Science, Daejeon (Korea, Republic of); Kwon, Hyun Joon [Univ. of Maryland, Maryland (United States); Kwon, Young Ha [Kyung Hee Univ., Gyunggi Do (Korea, Republic of)

    2012-10-15

    This paper presents a design of a robot head module with touch sensing algorithms that can simultaneously detect contact force and location. The module is constructed with a hemisphere and three sensor units that are fabricated using contact resistance force sensors. The surface part is designed with the hemisphere that measures 300 mm in diameter and 150 mm in height. Placed at the bottom of the robot head module are three sensor units fabricated using a simple screen printing technique. The contact force and the location of the model are evaluated through the calibration setup. The experiment showed that the calculated contact positions almost coincided with the applied load points as the contact location changed with a location error of about {+-}8.67 mm. The force responses of the module were evaluated at two points under loading and unloading conditions from 0 N to 5 N. The robot head module showed almost the same force responses at the two points.

  1. Distribution and direct radiative forcing of carbonaceous and sulfate aerosols in an interactive size-resolving aerosol-climate model

    Science.gov (United States)

    Kim, Dongchul; Wang, Chien; Ekman, Annica M. L.; Barth, Mary C.; Rasch, Phil J.

    2008-08-01

    A multimode, two-moment aerosol model has been incorporated in the NCAR CAM3 to develop an interactive aerosol-climate model and to study the impact of anthropogenic aerosols on the global climate system. Currently, seven aerosol modes, namely three for external sulfate and one each for external black carbon (BC), external organic carbon (OC), sulfate/BC mixture (MBS; with BC core coated by sulfate shell), and sulfate/OC mixture (MOS; a uniform mixture of OC and sulfate) are included in the model. Both mass and number concentrations of each aerosol mode, as well as the mass of carbonaceous species in the mixed modes, are predicted by the model so that the chemical, physical, and radiative processes of various aerosols can be formulated depending on aerosol's size, chemical composition, and mixing state. Comparisons of modeled surface and vertical aerosol concentrations, as well as the optical depth of aerosols with available observations and previous model estimates, are in general agreement. However, some discrepancies do exist, likely caused by the coarse model resolution or the constant rates of anthropogenic emissions used to test the model. Comparing to the widely used mass-only method with prescribed geometric size of particles (one-moment scheme), the use of prognostic size distributions of aerosols based on a two-moment scheme in our model leads to a significant reduction in optical depth and thus the radiative forcing at the top of the atmosphere (TOA) of particularly external sulfate aerosols. The inclusion of two types of mixed aerosols alters the mass partitioning of carbonaceous and sulfate aerosol constituents: about 35.5%, 48.5%, and 32.2% of BC, OC, and sulfate mass, respectively, are found in the mixed aerosols. This also brings in competing effects in aerosol radiative forcing including a reduction in atmospheric abundance of BC and OC due to the shorter lifetime of internal mixtures (cooling), a mass loss of external sulfate to mixtures (warming

  2. Dynamics of dissipative self-assembly of particles interacting through oscillatory forces.

    Science.gov (United States)

    Tagliazucchi, M; Szleifer, I

    2016-01-01

    Dissipative self-assembly is the formation of ordered structures far from equilibrium, which continuously uptake energy and dissipate it into the environment. Due to its dynamical nature, dissipative self-assembly can lead to new phenomena and possibilities of self-organization that are unavailable to equilibrium systems. Understanding the dynamics of dissipative self-assembly is required in order to direct the assembly to structures of interest. In the present work, Brownian dynamics simulations and analytical theory were used to study the dynamics of self-assembly of a mixture of particles coated with weak acids and bases under continuous oscillations of the pH. The pH of the system modulates the charge of the particles and, therefore, the interparticle forces oscillate in time. This system produces a variety of self-assembled structures, including colloidal molecules, fibers and different types of crystalline lattices. The most important conclusions of our study are: (i) in the limit of fast oscillations, the whole dynamics (and not only those at the non-equilibrium steady state) of a system of particles interacting through time-oscillating interparticle forces can be described by an effective potential that is the time average of the time-dependent potential over one oscillation period; (ii) the oscillation period is critical to determine the order of the system. In some cases the order is favored by very fast oscillations while in others small oscillation frequencies increase the order. In the latter case, it is shown that slow oscillations remove kinetic traps and, thus, allow the system to evolve towards the most stable non-equilibrium steady state.

  3. Forces of Tool-Tissue Interaction to Assess Surgical Skill Level.

    Science.gov (United States)

    Sugiyama, Taku; Lama, Sanju; Gan, Liu Shi; Maddahi, Yaser; Zareinia, Kourosh; Sutherland, Garnette R

    2017-11-15

    The application of optimal forces between surgical instruments and tissue is fundamental to surgical performance and learning. To date, this force has not been measured clinically during the performance of microsurgery. To establish a normative catalog of force profiles during the performance of surgery, to compare force variables among surgeons with different skill levels, and to evaluate whether such a force-based metric determines or differentiates skill level. Through installation of strain gauge sensors, a force-sensing bipolar forceps was developed, and force data were obtained from predetermined surgical tasks at the Foothills Medical Centre, University of Calgary, a tertiary care center that serves Southern Alberta, Canada. Sixteen neurosurgeons (3 groups: novice, intermediate, and experienced) performed surgery on 26 neurosurgical patients with various conditions. Normative baseline force ranges were obtained using the force profiles (mean and maximum forces and force variability) from the experienced surgeons. Standardized force profiles and force errors (high force error [HFE], low force error [LFE], and force variability error [FVE]) were analyzed and compared among surgeons with different skill levels. Each trial of the forceps use was termed successful or unsuccessful. The force profiles and force errors were analyzed and compared. This study included 26 patients (10 [38%] male and 16 [62%] female; mean [SD] age, 43 [15] years) undergoing neurosurgery by 16 surgeons (6 in the novice group, 5 in the intermediate group, and 5 in the experienced group). Unsuccessful trial-incomplete significantly correlated with LFE and FVE, and unsuccessful trial-bleeding correlated with HFE and FVE. The force strengths exerted by novice surgeons were significantly higher than those of experienced surgeons (mean force, 0.74N vs 0.00N; P intermediate (mean force, 0.28N) to experienced (mean force, 0.00N) surgeons; however, these differences varied among surgical tasks

  4. Evaluation of cutting force and surface roughness in high-speed milling of compacted graphite iron

    Directory of Open Access Journals (Sweden)

    Azlan Suhaimi Mohd

    2017-01-01

    Full Text Available Compacted Graphite Iron, (CGI is known to have outstanding mechanical strength and weight-to-strength ratio as compared to conventional grey cast iron, (CI. The outstanding characteristics of CGI is due to its graphite particle shape, which is presented as compacted vermicular particle. The graphite is interconnected with random orientation and round edges, which results in higher mechanical strength. Whereas, graphite in the CI consists of a smooth-surfaced flakes that easily propagates cracks which results in weaker and brittle properties as compared to CGI. Owing to its improved properties, CGI is considered as the best candidate material in substituting grey cast iron that has been used in engine block applications for years. However, the smooth implementation of replacing CI with CGI has been hindered due to the poor machinability of CGI especially at high cutting speed. The tool life is decreased by 20 times when comparing CGI with CI under the same cutting condition. This study investigates the effect of using cryogenic cooling and minimum quantity lubrication (MQL during high-speed milling of CGI (grade 450. Results showed that, the combination of internal cryogenic cooling and enhanced MQL improved the tool life, cutting force and surface quality as compared to the conventional flood coolant strategy during high-speed milling of CGI.

  5. Impact of particle size on interaction forces between ettringite and dispersing comb-polymers in various electrolyte solutions.

    Science.gov (United States)

    Ferrari, Lucia; Kaufmann, Josef; Winnefeld, Frank; Plank, Johann

    2014-04-01

    The inter-particle forces play a fundamental role for the flow properties of a particle suspension in response to shear stresses. In concrete applications, cement admixtures based on comb-polymers like polycarboxylate-ether-based superplasticizer (PCE) are used to control the rheological behavior of the fresh mixtures, as it is negatively impacted by certain early hydration products, like the mineral ettringite. In this work, dispersion forces due to PCE were measured directly at the surface of ettringite crystals in different electrolyte solutions by the means of atomic force microscopy (AFM) applying spherical and sharp silicon dioxide tips. Results show an effective repulsion between ettringite surface and AFM tips for solutions above the IEP of ettringite (pH∼12) and significant attraction in solution at lower pH. The addition of polyelectrolytes in solution provides dispersion forces exclusively between the sharp tips (radius ≈ 10 nm) and the ettringite surface, whereas the polymer layer at the ettringite surface results to be unable to disperse large colloidal probes (radius ≈ 10 μm). A simple modeling of the inter-particle forces explains that, for large particles, the steric hindrance of the studied PCE molecules is not high enough to compensate for the Van der Waals and the attractive electrostatic contributions. Therefore, in cement suspensions the impact of ettringite on rheology is probably not only related to the particle charge, but also related to the involved particle sizes. Copyright © 2013 Elsevier Inc. All rights reserved.

  6. Modification of a force plate system for equine gait analysis on hard road surfaces: a technical note.

    Science.gov (United States)

    Wilson, A M; Pardoe, C H

    2001-04-01

    Studies on horseshoe materials have been limited to the analysis of kinematic data to determine slip times and distances, since equine force plate analysis is traditionally undertaken on a rubber-surfaced force plate. The purpose of this study was to modify a force plate for measuring ground reaction forces on a road surface and report preliminary data from the system. A steel-reinforced concrete top plate of 18 mm thickness and mass 23 kg, and a 12 mm thick top plate of 6 mm bituminous macadam wear coat (road surface) contained in a tray constructed of 2 mm thick steel, mass 21 kg, were constructed. The top plates were bolted to a forceplate and resonance frequency of the force plate top plate combinations were 278 Hz (concrete) and 218 Hz (roadway), respectively. Simultaneous kinetic and kinematic data were collected while a horse, shod in steel horseshoes, was trotted over the concrete-topped force plate until 8 foot placements were recorded. The foot slipped for mean +/- s.d. 35 +/- 7 mm in 29 +/- 8 ms after impact and both Fy and Fz increased during foot slip. The ratio of Fy/Fz during slip was relatively constant at 0.56 +/- 0.05. The top plates have proved resilient in use and have withstood a variety of horseshoe designs and tungsten-capped stud nails with minimal damage. They enable measurement of ground reaction forces on hard surfaces and the calculation of the energy dissipated via foot slippage by integration of the craniocaudal force-foot position data after impact.

  7. Highly Oriented Nanowire Thin Films with Anisotropic Optical Properties Driven by the Simultaneous Influence of Surface Templating and Shear Forces.

    Science.gov (United States)

    Probst, Patrick T; Sekar, Sribharani; König, Tobias A F; Formanek, Petr; Decher, Gero; Fery, Andreas; Pauly, Matthias

    2018-01-24

    The fu