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Sample records for adhesive potential electrostatic

  1. Innovative Electrostatic Adhesion Technologies

    NASA Technical Reports Server (NTRS)

    Bryan, Tom; Macleod, Todd; Gagliano, Larry; Williams, Scott; McCoy, Brian

    2015-01-01

    Developing specialized Electro-Static grippers (commercially used in Semiconductor Manufacturing and in package handling) will allow gentle and secure Capture, Soft Docking, and Handling of a wide variety of materials and shapes (such as upper-stages, satellites, arrays, and possibly asteroids) without requiring physical features or cavities for a pincher or probe or using harpoons or nets. Combined with new rigid boom mechanisms or small agile chaser vehicles, flexible, high speed Electro-Static Grippers can enable compliant capture of spinning objects starting from a safe stand-off distance. Electroadhesion (EA) can enable lightweight, ultra-low-power, compliant attachment in space by using an electrostatic force to adhere similar and dissimilar surfaces. A typical EA enabled device is composed of compliant space-rated materials, such as copper-clad polyimide encapsulated by polymers. Attachment is induced by strong electrostatic forces between any substrate material, such as an exterior satellite panel and a compliant EA gripper pad surface. When alternate positive and negative charges are induced in adjacent planar electrodes in an EA surface, the electric fields set up opposite charges on the substrate and cause an electrostatic adhesion between the electrodes and the induced charges on the substrate. Since the electrodes and the polymer are compliant and can conform to uneven or rough surfaces, the electrodes can remain intimately close to the entire surface, enabling high clamping pressures. Clamping pressures of more than 3 N/cm2 in shear can be achieved on a variety of substrates with ultra-low holding power consumption (measured values are less than 20 microW/Newton weight held). A single EA surface geometry can be used to clamp both dielectric and conductive substrates, with slightly different physical mechanisms. Furthermore EA clamping requires no normal force be placed on the substrate, as conventional docking requires. Internally funded research and

  2. Innovative Electrostatic Adhesion Technologies

    NASA Astrophysics Data System (ADS)

    Gagliano, L.; Bryan, T.; Williams, S.; McCoy, B.; MacLeod, T.

    Developing specialized Electro-Static grippers (commercially used in Semiconductor Manufacturing and in package handling) will allow gentle and secure Capture, Soft Docking, and Handling of a wide variety of materials and shapes (such as upper-stages, satellites, arrays, and possibly asteroids) without requiring physical features or cavities for a pincher or probe or using harpoons or nets. Combined with new rigid boom mechanisms or small agile chaser vehicles, flexible, high speed Electro-Static Grippers can enable compliant capture of spinning objects starting from a safe stand-off distance. Electroadhesion (EA) can enable lightweight, ultra-low-power, compliant attachment in space by using an electrostatic force to adhere similar and dissimilar surfaces. A typical EA enabled device is composed of compliant space-rated materials, such as copper-clad polyimide encapsulated by polymers. Attachment is induced by strong electrostatic forces between any substrate material, such as an exterior satellite panel and a compliant EA surface. When alternate positive and negative charges are induced in adjacent planar electrodes in an EA surface, the electric fields set up opposite charges on the substrate and cause an electrostatic adhesion between the electrodes and the induced charges on the substrate. Since the electrodes and the polymer are compliant and can conform to uneven or rough surfaces, the electrodes can remain intimately close to the entire surface, enabling high clamping pressures. Clamping pressures of more than 3 N/cm2 in shear can be achieved on a variety of substrates with ultra-low holding power consumption (measured values are less than 20 microW/Newton weight held). A single EA surface geometry can be used to clamp both dielectric and conductive substrates, with slightly different physical mechanisms. Furthermore EA clamping requires no normal force be placed on the substrate, as conventional docking requires. Internally funded research and development

  3. Optimization and experimental validation of electrostatic adhesive geometry

    NASA Astrophysics Data System (ADS)

    Ruffatto, D.; Shah, J.; Spenko, M.

    This paper introduces a method to optimize the electrode geometry of electrostatic adhesives for robotic gripping, attachment, and manipulation applications. Electrostatic adhesion is achieved by applying a high voltage potential, on the order of kV, to a set of electrodes, which generates an electric field. The electric field polarizes the substrate material and creates an adhesion force. Previous attempts at creating electro-static adhesives have shown them to be effective, but researchers have made no effort to optimize the electrode configuration and geometry. We have shown that by optimizing the geometry of the electrode configuration, the electric field strength, and therefore the adhesion force, is enhanced. To accomplish this, Comsol Multiphysics was utilized to evaluate the average electric field generated by a given electrode geometry. Several electrode patterns were evaluated, including parallel conductors, concentric circles, Hilbert curves (a fractal geometry) and spirals. The arrangement of the electrodes in concentric circles with varying electrode widths proved to be the most effective. The most effective sizing was to use the smallest gap spacing allowable coupled with a variable electrode width. These results were experimentally validated on several different surfaces including drywall, wood, tile, glass, and steel. A new manufacturing process allowing for the fabrication of thin, conformal electro-static adhesive pads was utilized. By combining the optimized electrode geometry with the new fabrication process we are able to demonstrate a marked improvement of up to 500% in shear pressure when compared to previously published values.

  4. Integrating electrostatic adhesion to composite structures

    NASA Astrophysics Data System (ADS)

    Heath, Callum J. C.; Bond, Ian P.; Potter, Kevin D.

    2015-04-01

    Additional functionality within load bearing components holds potential for adding value to a structure, design or product. We consider the adaptation of an established technology, electrostatic adhesion or electroadhesion, for application in glass fibre reinforced polymer (GFRP) composite materials. Electroadhesion uses high potential difference (~2-3 kV) between co-planar electrodes to generate temporary holding forces to both electrically conductive and nonconductive contact surfaces. Using a combination of established fabrication techniques, electroadhesive elements are co-cured within a composite host structure during manufacture. This provides an almost symbiotic relationship between the electroadhesive and the composite structure, with the electroadhesive providing an additional functionality, whilst the epoxy matrix material of the composite acts as a dielectric for the high voltage electrodes of the device. Silicone rubber coated devices have been shown to offer high shear load (85kPa) capability for GFRP components held together using this technique. Through careful control of the connection interface, we consider the incorporation of these devices within complete composite structures for additional functionality. The ability to vary the internal connectivity of structural elements could allow for incremental changes in connectivity between discrete sub-structures, potentially introducing variable stiffness to the global structure.

  5. The Role of the Electrostatic Force in Spore Adhesion

    SciTech Connect

    Chung, Eunhyea; Yiacoumi, Sotira; Lee, Ida; Tsouris, Costas

    2010-01-01

    Electrostatic force is investigated as one of the components of the adhesion force between Bacillus thuringiensis (Bt) spores and planar surfaces. The surface potentials of a Bt spore and a mica surface are experimentally obtained using a combined atomic force microscopy (AFM)-scanning surface potential microscopy technique. On the basis of experimental information, the surface charge density of the spores is estimated at 0.03 {micro}C/cm{sup 2} at 20% relative humidity and decreases with increasing humidity. The Coulombic force is introduced for the spore-mica system (both charged, nonconductive surfaces), and an electrostatic image force is introduced to the spore-gold system because gold is electrically conductive. The Coulombic force for spore-mica is repulsive because the components are similarly charged, while the image force for the spore-gold system is attractive. The magnitude of both forces decreases with increasing humidity. The electrostatic forces are added to other force components, e.g., van der Waals and capillary forces, to obtain the adhesion force for each system. The adhesion forces measured by AFM are compared to the estimated values. It is shown that the electrostatic (Coulombic and image) forces play a significant role in the adhesion force between spores and planar surfaces.

  6. Electrostatic adhesion for added functionality of composite structures

    NASA Astrophysics Data System (ADS)

    Heath, Callum J. C.; Bond, Ian P.; Potter, Kevin D.

    2016-02-01

    Electrostatic adhesion can be used as a means of reversible attachment. The incorporation of electrostatic adhesion into fibre reinforced polymer (FRP) composite structures could provide significant value added functionality. Imparting large potential differences (∼2 kV) across electrodes generates an attractive force, thus providing a means of attachment. This could be used as a reversible latching mechanism or as a means of controllable internal connectivity. Varying the connectivity for discrete elements of a substructure of a given design allows for control of internal load paths and moment of area of the cross section. This could facilitate variable stiffness (both in bending and torsion). Using a combination of existing fabrication techniques, functional electrodes have been integrated within a FRP. Copper polyimide thin film laminate material has been both co-cured with carbon fibre reinforced epoxy and bonded to PVC closed cell foam core material to provide a range of structural configurations with integrated electrodes. The ability of such integrated devices to confer variations in global bending stiffness of basic beam structures is investigated. Through the application of 4 kV across integrated electrostatic adhesive devices, a 112% increase in flexural stiffness has been demonstrated for a composite sandwich structure.

  7. Electrostatic adhesion of multiple non-uniformly charged dielectric particles

    NASA Astrophysics Data System (ADS)

    Kemp, B. A.; Whitney, J. G.

    2013-01-01

    Charged particle adhesion measurements can be as much as one order of magnitude higher than theoretical calculations. This discrepancy has ignited a debate as to the nature of the physics occurring with microscopic particle adhesion. Attempts to bring calculations closer to measured results have produced models that include multiple particle interactions, dielectric polarization, and non-uniform charge. Individually, each of these models can only produce a 2× to 5× enhancement in predicted adhesion force over simple Coulombic attraction. In this correspondence, an analytical model of electrostatic particle forces is developed, which allows for independent assignment of dielectric constant and non-uniform surface charge distribution to an arbitrary number of particles. Because the model can include an image plane, it is ideal for electrostatic adhesion calculations. Application to a monolayer of printed toner particles predicts nearly an order of magnitude increase in adhesion force over Coulombic attraction. These results are the first analytical results to place predictions of charged particle adhesion on the same order of magnitude with measurements.

  8. Role of contact electrification and electrostatic interactions in gecko adhesion.

    PubMed

    Izadi, Hadi; Stewart, Katherine M E; Penlidis, Alexander

    2014-09-06

    Geckos, which are capable of walking on walls and hanging from ceilings with the help of micro-/nano-scale hierarchical fibrils (setae) on their toe pads, have become the main prototype in the design and fabrication of fibrillar dry adhesives. As the unique fibrillar feature of the toe pads of geckos allows them to develop an intimate contact with the substrate the animal is walking on or clinging to, it is expected that the toe setae exchange significant numbers of electric charges with the contacted substrate via the contact electrification (CE) phenomenon. Even so, the possibility of the occurrence of CE and the contribution of the resulting electrostatic interactions to the dry adhesion of geckos have been overlooked for several decades. In this study, by measuring the magnitude of the electric charges, together with the adhesion forces, that gecko foot pads develop in contact with different materials, we have clarified for the first time that CE does contribute effectively to gecko adhesion. More importantly, we have demonstrated that it is the CE-driven electrostatic interactions which dictate the strength of gecko adhesion, and not the van der Waals or capillary forces which are conventionally considered as the main source of gecko adhesion.

  9. Epithelial Microvilli Establish an Electrostatic Barrier to Microbial Adhesion

    PubMed Central

    Bennett, Kaila M.; Walker, Sharon L.

    2014-01-01

    Microvilli are membrane extensions on the apical surface of polarized epithelia, such as intestinal enterocytes and tubule and duct epithelia. One notable exception in mucosal epithelia is M cells, which are specialized for capturing luminal microbial particles; M cells display a unique apical membrane lacking microvilli. Based on studies of M cell uptake under different ionic conditions, we hypothesized that microvilli may augment the mucosal barrier by providing an increased surface charge density from the increased membrane surface and associated glycoproteins. Thus, electrostatic charges may repel microbes from epithelial cells bearing microvilli, while M cells are more susceptible to microbial adhesion. To test the role of microvilli in bacterial adhesion and uptake, we developed polarized intestinal epithelial cells with reduced microvilli (“microvillus-minus,” or MVM) but retaining normal tight junctions. When tested for interactions with microbial particles in suspension, MVM cells showed greatly enhanced adhesion and uptake of particles compared to microvillus-positive cells. This preference showed a linear relationship to bacterial surface charge, suggesting that microvilli resist binding of microbes by using electrostatic repulsion. Moreover, this predicts that pathogen modification of electrostatic forces may contribute directly to virulence. Accordingly, the effacement effector protein Tir from enterohemorrhagic Escherichia coli O157:H7 expressed in epithelial cells induced a loss of microvilli with consequent enhanced microbial binding. These results provide a new context for microvillus function in the host-pathogen relationship, based on electrostatic interactions. PMID:24778113

  10. Improving controllable adhesion on both rough and smooth surfaces with a hybrid electrostatic/gecko-like adhesive

    PubMed Central

    Ruffatto, Donald; Parness, Aaron; Spenko, Matthew

    2014-01-01

    This paper describes a novel, controllable adhesive that combines the benefits of electrostatic adhesives with gecko-like directional dry adhesives. When working in combination, the two technologies create a positive feedback cycle whose adhesion, depending on the surface type, is often greater than the sum of its parts. The directional dry adhesive brings the electrostatic adhesive closer to the surface, increasing its effect. Similarly, the electrostatic adhesion helps engage more of the directional dry adhesive fibrillar structures, particularly on rough surfaces. This paper presents the new hybrid adhesive's manufacturing process and compares its performance to three other adhesive technologies manufactured using a similar process: reinforced PDMS, electrostatic and directional dry adhesion. Tests were performed on a set of ceramic tiles with varying roughness to quantify its effect on shear adhesive force. The relative effectiveness of the hybrid adhesive increases as the surface roughness is increased. Experimental data are also presented for different substrate materials to demonstrate the enhanced performance achieved with the hybrid adhesive. Results show that the hybrid adhesive provides up to 5.1× greater adhesion than the electrostatic adhesive or directional dry adhesive technologies alone. PMID:24451392

  11. Molecular electrostatic potential as a graph.

    PubMed

    Daza, Edgar E; Maza, Julio; Torres, Raul

    2013-06-01

    We present several procedures to represent molecular electrostatic potential as a graph, based on the pattern of critical points and their neighborhood relations. This representation is used for the molecular electrostatic comparison, which is reduced to a comparison of tree-type graphs. Several methods to compare trees are also presented. The applications of this algorithm to compare and classify molecules through their electrostatic potential are illustrated.

  12. Electrostatic potential map modelling with COSY Infinity

    NASA Astrophysics Data System (ADS)

    Maloney, J. A.; Baartman, R.; Planche, T.; Saminathan, S.

    2016-06-01

    COSY Infinity (Makino and Berz, 2005) is a differential-algebra based simulation code which allows accurate calculation of transfer maps to arbitrary order. COSY's existing internal procedures were modified to allow electrostatic elements to be specified using an array of field potential data from the midplane. Additionally, a new procedure was created allowing electrostatic elements and their fringe fields to be specified by an analytic function. This allows greater flexibility in accurately modelling electrostatic elements and their fringe fields. Applied examples of these new procedures are presented including the modelling of a shunted electrostatic multipole designed with OPERA, a spherical electrostatic bender, and the effects of different shaped apertures in an electrostatic beam line.

  13. Electrostatic patch potentials in Casimir force measurements

    NASA Astrophysics Data System (ADS)

    Garrett, Joseph; Somers, David; Munday, Jeremy

    2015-03-01

    Measurements of the Casimir force require the elimination of the electrostatic force between interacting surfaces. The force can be minimized by applying a potential to one of the two surfaces. However, electrostatic patch potentials remain and contribute an additional force which can obscure the Casimir force signal. We will discuss recent measurements of patch potentials made with Heterodyne Amplitude-Modulated Kelvin Probe Force Microscopy that suggest patches could be responsible for >1% of the signal in some Casimir force measurements, and thus make the distinction between different theoretical models of the Casimir force (e.g. a Drude-model or a plasma-model for the dielectric response) difficult to discern.

  14. The role of electrostatic charge in the adhesion of spherical particles onto planar surfaces in atmospheric systems

    SciTech Connect

    Kweon, Hyojin; Yiacoumi, Sotira Z.; Tsouris, Costas

    2015-06-19

    In this study, the influence of electrostatic charge on the adhesive force between spherical particles and planar surfaces in atmospheric systems was studied using atomic force microscopy. Electrical bias was applied to modify the surface charge, and it was found that application of a stronger positive bias to a particle induces a stronger total adhesive force. The sensitivity of the system to changes in the bias depended on the surface charge density. For larger-size particles, the contribution of the electrostatic force decreased, and the capillary force became the major contributor to the total adhesive force. The influence of water adsorption on the total adhesive force and, specifically, on the contribution of the electrostatic force depended on the hydrophobicity of interacting surfaces. For a hydrophilic surface, water adsorption either attenuated the surface charge or screened the effect of surface potential. An excessive amount of adsorbed water provided a path to surface charge leakage, which might cancel out the electrostatic force, leading to a reduction in the adhesive force. Theoretically calculated forces were comparable with measured adhesive forces except for mica which has a highly localized surface potential. The results of this study provide information on the behavior of charged colloidal particles in atmospheric systems.

  15. The role of electrostatic charge in the adhesion of spherical particles onto planar surfaces in atmospheric systems

    DOE PAGES

    Kweon, Hyojin; Yiacoumi, Sotira Z.; Tsouris, Costas

    2015-06-19

    In this study, the influence of electrostatic charge on the adhesive force between spherical particles and planar surfaces in atmospheric systems was studied using atomic force microscopy. Electrical bias was applied to modify the surface charge, and it was found that application of a stronger positive bias to a particle induces a stronger total adhesive force. The sensitivity of the system to changes in the bias depended on the surface charge density. For larger-size particles, the contribution of the electrostatic force decreased, and the capillary force became the major contributor to the total adhesive force. The influence of water adsorptionmore » on the total adhesive force and, specifically, on the contribution of the electrostatic force depended on the hydrophobicity of interacting surfaces. For a hydrophilic surface, water adsorption either attenuated the surface charge or screened the effect of surface potential. An excessive amount of adsorbed water provided a path to surface charge leakage, which might cancel out the electrostatic force, leading to a reduction in the adhesive force. Theoretically calculated forces were comparable with measured adhesive forces except for mica which has a highly localized surface potential. The results of this study provide information on the behavior of charged colloidal particles in atmospheric systems.« less

  16. Measurement and control of electrostatic patch potentials

    NASA Astrophysics Data System (ADS)

    Garrett, Joseph L.; Munday, Jeremy N.

    Electrostatic patch potentials hinder many precision measurements, particularly measurements of the Casimir force. Despite the improved force sensitivity achieved over the last decade, only recently have attempts been made to measure and quantify the effects of patch potentials. Here we present an analysis of patch potentials measured by Kelvin probe force microscopy (KPFM) and discuss methods to control these potentials (e.g. humidity, material choice, etc).

  17. Microgravity Experiments to Evaluate Electrostatic Forces in Controlling Cohesion and Adhesion of Granular Materials

    NASA Technical Reports Server (NTRS)

    Marshall, J.; Weislogel, M.; Jacobson, T.

    1999-01-01

    , are pervasive and probably affect, at some level, everything from astrophysical-scale granular systems such as interstellar nebulae, protoplanetary dust and debris disks, planetary-scale systems such as debris palls from meteorite impact, volcanic eruptions, and aeolian dust storms, all the way to industrial-scale systems in mining, powder and grain processing, pharmaceuticals, and smoke-stack technologies. NASA must concern itself with the electrostatic behavior of dust and sand on Mars because of its potentially critical importance to human exploration. The motion and adhesion of martian surface materials will affect the design and performance of spacesuits, habitats, processing plants, solar panels, and any externally exposed equipment such as surface rovers or communication and weather stations. Additionally, the adhesion of dust and sand could greatly enhance contact with the potentially toxic components of the martian soil.

  18. Electrostatic Potential of Specific Mineral Faces

    SciTech Connect

    Zarzycki, Piotr P.; Chatman, Shawn ME; Preocanin, Tajana; Rosso, Kevin M.

    2011-07-05

    Reaction rates of environmental processes occurring at hydrated mineral surfaces are primarily controlled by the electrostatic potential that develops at the interface. This potential depends on the structure of exposed crystal faces, as well as the pH and the type of ions and their interactions with these faces. Despite its importance, experimental methods for determining fundamental electrostatic properties of specific crystal faces such as the point of zero charge are few. Here we show that this information may be obtained from simple, cyclic potentiometric titration using a well characterized single-crystal electrode exposing the face of interest. The method exploits the presence of a hysteresis loop in the titration measurements that allows extraction of key electrostatic descriptors using the Maxwell construction. The approach is demonstrated for hematite (α-Fe2O3) (001), and a thermodynamic proof is provided for the resulting estimate of its point of zero charge. Insight gained from this method will aid in predicting the fate of migrating contaminants, mineral growth/dissolution processes, mineral-microbiological interactions, and in testing surface complexation theories.

  19. Deppdb--DNA electrostatic potential properties database: electrostatic properties of genome DNA.

    PubMed

    Osypov, Alexander A; Krutinin, Gleb G; Kamzolova, Svetlana G

    2010-06-01

    The electrostatic properties of genome DNA influence its interactions with different proteins, in particular, the regulation of transcription by RNA-polymerases. DEPPDB--DNA Electrostatic Potential Properties Database--was developed to hold and provide all available information on the electrostatic properties of genome DNA combined with its sequence and annotation of biological and structural properties of genome elements and whole genomes. Genomes in DEPPDB are organized on a taxonomical basis. Currently, the database contains all the completely sequenced bacterial and viral genomes according to NCBI RefSeq. General properties of the genome DNA electrostatic potential profile and principles of its formation are revealed. This potential correlates with the GC content but does not correspond to it exactly and strongly depends on both the sequence arrangement and its context (flanking regions). Analysis of the promoter regions for bacterial and viral RNA polymerases revealed a correspondence between the scale of these proteins' physical properties and electrostatic profile patterns. We also discovered a direct correlation between the potential value and the binding frequency of RNA polymerase to DNA, supporting the idea of the role of electrostatics in these interactions. This matches a pronounced tendency of the promoter regions to possess higher values of the electrostatic potential.

  20. DEPPDB - DNA electrostatic potential properties database. Electrostatic properties of genome DNA elements.

    PubMed

    Osypov, Alexander A; Krutinin, Gleb G; Krutinina, Eugenia A; Kamzolova, Svetlana G

    2012-04-01

    Electrostatic properties of genome DNA are important to its interactions with different proteins, in particular, related to transcription. DEPPDB - DNA Electrostatic Potential (and other Physical) Properties Database - provides information on the electrostatic and other physical properties of genome DNA combined with its sequence and annotation of biological and structural properties of genomes and their elements. Genomes are organized on taxonomical basis, supporting comparative and evolutionary studies. Currently, DEPPDB contains all completely sequenced bacterial, viral, mitochondrial, and plastids genomes according to the NCBI RefSeq, and some model eukaryotic genomes. Data for promoters, regulation sites, binding proteins, etc., are incorporated from established DBs and literature. The database is complemented by analytical tools. User sequences calculations are available. Case studies discovered electrostatics complementing DNA bending in E.coli plasmid BNT2 promoter functioning, possibly affecting host-environment metabolic switch. Transcription factors binding sites gravitate to high potential regions, confirming the electrostatics universal importance in protein-DNA interactions beyond the classical promoter-RNA polymerase recognition and regulation. Other genome elements, such as terminators, also show electrostatic peculiarities. Most intriguing are gene starts, exhibiting taxonomic correlations. The necessity of the genome electrostatic properties studies is discussed.

  1. The Calculation of the Electrostatic Potential of Infinite Charge Distributions

    ERIC Educational Resources Information Center

    Redzic, Dragan V.

    2012-01-01

    We discuss some interesting aspects in the calculation of the electrostatic potential of charge distributions extending to infinity. The presentation is suitable for the advanced undergraduate level. (Contains 3 footnotes.)

  2. The Contribution of Surface Potential to Diverse Problems in Electrostatics

    NASA Astrophysics Data System (ADS)

    Horenstein, M.

    2015-10-01

    Electrostatics spans many different subject areas. Some comprise “good electrostatics,” where charge is used for desirable purposes. Such areas include industrial manufacturing, electrophotography, surface modification, precipitators, aerosol control, and MEMS. Other areas comprise “bad electrostatics,” where charge is undesirable. Such areas include hazardous discharges, ESD, health effects, nuisance triboelectrification, particle contamination, and lightning. Conference proceedings such as this one inevitably include papers grouped around these topics. One common thread throughout is the surface potential developed when charge resides on an insulator surface. Often, the charged insulator will be in intimate contact with a ground plane. At other times, the charged insulator will be isolated. In either case, the resulting surface potential is important to such processes as propagating brush discharges, charge along a moving web, electrostatic biasing effects in MEMS, non-contacting voltmeters, field-effect transistor sensors, and the maximum possible charge on a woven fabric.

  3. Potential Polymeric Sphere Construction Materials for a Spacecraft Electrostatic Shield

    NASA Technical Reports Server (NTRS)

    Smith, Joseph G., Jr.; Smith, Trent; Williams, Martha; Youngquist, Robert; Mendell, Wendell

    2006-01-01

    An electrostatic shielding concept for spacecraft radiation protection under NASA s Exploration Systems Research and Technology Program was evaluated for its effectiveness and feasibility. The proposed shield design is reminiscent of a classic quadrupole with positively and negatively charged spheres surrounding the spacecraft. The project addressed materials, shield configuration, power supply, and compared its effectiveness to that of a passive shield. The report herein concerns the identification of commercially available materials that could be used in sphere fabrication. It was found that several materials were needed to potentially construct the spheres for an electrostatic shield operating at 300 MV.

  4. Deriving static atomic multipoles from the electrostatic potential.

    PubMed

    Kramer, Christian; Bereau, Tristan; Spinn, Alexander; Liedl, Klaus R; Gedeck, Peter; Meuwly, Markus

    2013-12-23

    The description of molecular systems using multipolar electrostatics calls for automated methods to fit the necessary parameters. In this paper, we describe an open-source software package that allows fitting atomic multipoles (MTPs) from the ab initio electrostatic potential by adequate atom typing and judicious assignment of the local axis system. By enabling the simultaneous fit of several molecules and/or conformations, the package addresses issues of parameter transferability and lack of sampling for buried atoms. We illustrate the method by studying a series of small alcohol molecules, as well as various conformations of protonated butylamine.

  5. Scanning Surface Potential Microscopy of Spore Adhesion on Surfaces

    SciTech Connect

    Lee, Ida; Chung, Eunhyea; Kweon, Hyojin; Yiacoumi, Sotira; Tsouris, Costas

    2012-01-01

    The adhesion of spores of Bacillus anthracis - the cause of anthrax and a likely biological threat - to solid surfaces is an important consideration in cleanup after an accidental or deliberate release. However, because of safety concerns, directly studying B. anthracis spores with advanced instrumentation is problematic. As a first step, we are examining the electrostatic potential of Bacillus thuringiensis (Bt), which is a closely related species that is often used as a simulant to study B. anthracis. Scanning surface potential microscopy (SSPM), also known as Kelvin probe force microscopy (KPFM), was used to investigate the influence of relative humidity (RH) on the surface electrostatic potential of Bt that had adhered to silica, mica, or gold substrates. AFM/SSPM side-by-side images were obtained separately in air, at various values of RH, after an aqueous droplet with spores was applied on each surface and allowed to dry before measurements. In the SSPM images, a negative potential on the surface of the spores was observed compared with that of the substrates. The surface potential decreased as the humidity increased. Spores were unable to adhere to a surface with an extremely negative potential, such as mica.

  6. Numerical study on the adhesion and reentrainment of nondeformable particles on surfaces: the role of surface roughness and electrostatic forces.

    PubMed

    Henry, Christophe; Minier, Jean-Pierre; Lefèvre, Grégory

    2012-01-10

    In this paper, the reentrainment of nanosized and microsized particles from rough walls under various electrostatic conditions and various hydrodynamic conditions (either in air or aqueous media) is numerically investigated. This issue arises in the general context of particulate fouling in industrial applications, which involves (among other phenomena) particle deposition and particle reentrainment. The deposition phenomenon has been studied previously and, in the present work, we focus our attention on resuspension. Once particles are deposited on a surface, the balance between hydrodynamic forces (which tend to move particles away from the surface) and adhesion forces (which maintain particles on the surface) can lead to particle removal. Adhesion forces are generally described using van der Waals attractive forces, but the limit of these models is that any dependence of adhesion forces on electrostatic forces (due to variations in pH or ionic strength) cannot be reproduced numerically. For this purpose, we develop a model of adhesion forces that is based on the DLVO (Derjaguin and Landau, Verwey and Overbeek) theory and which includes also the effect of surface roughness through the use of hemispherical asperities on the surface. We first highlight the effect of the curvature radius on adhesion forces. Then some numerical predictions of adhesion forces or adhesion energies are compared to experimental data. Finally, the overall effects of surface roughness and electrostatic forces are demonstrated with some applications of the complete reentrainment model in some simple test cases.

  7. Microgravity Experiments to Evaluate Electrostatic Forces in Controlling Cohesion and Adhesion of Granular Materials

    NASA Technical Reports Server (NTRS)

    Marshall, J.; Weislogel, M.; Jacobson, T.

    1999-01-01

    The bulk behavior of dispersed, fluidized, or undispersed stationary granular systems cannot be fully understood in terms of adhesive/cohesive properties without understanding the role of electrostatic forces acting at the level of the grains themselves. When grains adhere to a surface, or come in contact with one another in a stationary bulk mass, it is difficult to measure the forces acting on the grains, and the forces themselves that induced the cohesion and adhesion are changed. Even if a single grain were to be scrutinized in the laboratory, it might be difficult, perhaps impossible, to define the distribution and character of surface charging and the three-dimensional relationship that charges (electrons, holes) have to one another. The hypothesis that we propose to test in microgravity (for dielectric materials) is that adhesion and cohesion of granular matter are mediated primarily by dipole forces that do not require the presence of a net charge; in fact, nominally electrically neutral materials should express adhesive and cohesive behavior when the neutrality results from a balance of positive and negative charge carriers. Moreover, the use of net charge alone as a measure of the electrical nature of grain-to-grain relationships within a granular mass may be misleading. We believe that the dipole forces arise from the presence of randomly-distributed positive and negative fixed charge carriers on grains that give rise to a resultant dipole moment. These dipole forces have long-range attraction. Random charges are created whenever there is triboelectrical activity of a granular mass, that is, whenever the grains experience contact/separation sequences or friction.

  8. Quantum mechanics/molecular mechanics restrained electrostatic potential fitting.

    PubMed

    Burger, Steven K; Schofield, Jeremy; Ayers, Paul W

    2013-12-05

    We present a quantum mechanics/molecular mechanics (QM/MM) method to evaluate the partial charges of amino acid residues for use in MM potentials based on their protein environment. For each residue of interest, the nearby residues are included in the QM system while the rest of the protein is treated at the MM level of theory. After a short structural optimization, the partial charges of the central residue are fit to the electrostatic potential using the restrained electrostatic potential (RESP) method. The resulting charges and electrostatic potential account for the individual environment of the residue, although they lack the transferable nature of library partial charges. To evaluate the quality of the QM/MM RESP charges, thermodynamic integration is used to measure the pKa shift of the aspartic acid residues in three different proteins, turkey egg lysozyme, beta-cryptogein, and Thioredoxin. Compared to the AMBER ff99SB library values, the QM/MM RESP charges show better agreement between the calculated and experimental pK(a) values for almost all of the residues considered.

  9. NMR studies of electrostatic potential distribution around biologically important molecules.

    PubMed Central

    Likhtenshtein, G I; Adin, I; Novoselsky, A; Shames, A; Vaisbuch, I; Glaser, R

    1999-01-01

    A new experimental approach has been developed to study the distribution of local electrostatic potential around specific protons in biologically important molecules. The approach is the development of a method denoted as "spin label/spin probe," which was proposed by one of us (. Mol. Biol. 6:498-507). The proposed method is based upon the quantitative measurement of the contribution of differently charged nitroxide probes to the spin lattice relaxation rate (1/T1) of protons in the molecule of interest, followed by calculation of local electrostatic potential using the classical Debye equation. In parallel, the theoretical calculation of potential distribution with the use of the MacSpartan Plus 1.0 program has been performed. Application of the method to solutions of simple organic molecules (aliphatic and aromatic alcohols, aliphatic carboxylates (propionate anion), and protonated ethyl amine and imidazole) allowed us to estimate the effective potential around the molecules under investigation. These were found to be in good agreement with theoretically expected values. This technique was then applied to zwitterionic amino acids bearing neutral and charged side chains (glycine, lysine, histidine, and aspartic acid). The reliability of the general approach is proved by the data presented in this paper. Application of this new methodology can afford insight into the biochemical significance of electrostatic effects in biological systems. PMID:10388770

  10. Electrostatics

    SciTech Connect

    Wallace, John P.; Wallace, Michael J.

    2015-12-04

    Quantum mechanics should be able to generate the basic properties of a particle. One of the most basic properties are charge and the associated electrostatic electric field. Electrostatic force is a fundamental characteristics of a charged fermion and should have its nature described by the fermion’s structure. To produce the particle properties require two spaces that define both their dynamics and their base structure. Relativity and the conservation of energy dictate how these two separate spaces are connected and the differential equations that describe behavior within these two spaces. The main static characteristic of an elementary fermion are mass and charge. Mass represents a scale measure of the fermion and it appears that charge results from the detailed structure of the fermion, which must merge into the electric field description of Maxwell. Coulomb’s law is a good approximation for large distances, but it is a poor approximation at dimension on the order of a particle’s Compton wavelength. The relativistic description of the fermion in its own frame of reference contains the information required for producing the electrostatic field over all space without a singularity as a source. With this description it is possible to understand the first order correction to the ionization energy of hydrogen. The role of nuclear effects on ionization energies can now be better defined for nuclei heavier than hydrogen.

  11. Automatic search for maximum similarity between molecular electrostatic potential distributions

    NASA Astrophysics Data System (ADS)

    Manaut, Francesc; Sanz, Ferran; José, Jaume; Milesi, Massimo

    1991-08-01

    A new computer program has been developed to automatically obtain the relative position of two molecules in which the similarity between molecular electrostatic-potential distributions is greatest. These distributions are considered in a volume around the molecules, and the similarity is measured by the Spearman rank coefficient. The program has been tested using several pairs of molecules: water vs. water; phenylethylamine and phenylpropylamine vs. benzylamine; and methotrexate vs. dihydrofolic acid.

  12. Atom-partitioned multipole expansions for electrostatic potential boundary conditions

    NASA Astrophysics Data System (ADS)

    Lee, M.; Leiter, K.; Eisner, C.; Knap, J.

    2017-01-01

    Applications such as grid-based real-space density functional theory (DFT) use the Poisson equation to compute electrostatics. However, the expected long tail of the electrostatic potential requires either the use of a large and costly outer domain or Dirichlet boundary conditions estimated via multipole expansion. We find that the oft-used single-center spherical multipole expansion is only appropriate for isotropic mesh domains such as spheres and cubes. In this work, we introduce a method suitable for high aspect ratio meshes whereby the charge density is partitioned into atomic domains and multipoles are computed for each domain. While this approach is moderately more expensive than a single-center expansion, it is numerically stable and still a small fraction of the overall cost of a DFT calculation. The net result is that when high aspect ratio systems are being studied, form-fitted meshes can now be used in lieu of cubic meshes to gain computational speedup.

  13. Multilevel Summation of Electrostatic Potentials Using Graphics Processing Units*

    PubMed Central

    Hardy, David J.; Stone, John E.; Schulten, Klaus

    2009-01-01

    Physical and engineering practicalities involved in microprocessor design have resulted in flat performance growth for traditional single-core microprocessors. The urgent need for continuing increases in the performance of scientific applications requires the use of many-core processors and accelerators such as graphics processing units (GPUs). This paper discusses GPU acceleration of the multilevel summation method for computing electrostatic potentials and forces for a system of charged atoms, which is a problem of paramount importance in biomolecular modeling applications. We present and test a new GPU algorithm for the long-range part of the potentials that computes a cutoff pair potential between lattice points, essentially convolving a fixed 3-D lattice of “weights” over all sub-cubes of a much larger lattice. The implementation exploits the different memory subsystems provided on the GPU to stream optimally sized data sets through the multiprocessors. We demonstrate for the full multilevel summation calculation speedups of up to 26 using a single GPU and 46 using multiple GPUs, enabling the computation of a high-resolution map of the electrostatic potential for a system of 1.5 million atoms in under 12 seconds. PMID:20161132

  14. Silicon addition to hydroxyapatite increases nanoscale electrostatic, van der Waals, and adhesive interactions.

    PubMed

    Vandiver, Jennifer; Dean, Delphine; Patel, Nelesh; Botelho, Claudia; Best, Serena; Santos, José D; Lopes, Maria A; Bonfield, William; Ortiz, Christine

    2006-08-01

    The normal intersurface forces between nanosized probe tips functionalized with COO(-)-terminated alkanethiol self-assembling monolayers and dense, polycrystalline silicon-substituted synthetic hydroxyapatite (SiHA) and phase pure hydroxyapatite (HA) were measured via a nanomechanical technique called chemically specific high-resolution force spectroscopy. A significantly larger van der Waals interaction was observed for the SiHA compared to HA; Hamaker constants (A) were found to be A(SiHA) = 35 +/- 27 zJ and A(HA) = 13 +/- 12 zJ. Using the Derjaguin-Landau-Verwey-Overbeek approximation, which assumes linear additivity of the electrostatic double layer and van der Waals components, and the nonlinear Poisson-Boltzmann surface charge model for electrostatic double-layer forces, the surface charge per unit area, sigma (C/m(2)), was calculated as a function of position for specific nanosized areas within individual grains. SiHA was observed to be more negatively charged than HA with sigma(SiHA) = -0.024 +/- 0.013 C/m(2), two times greater than sigma(HA) = -0.011 +/- 0.006 C/m(2). Additionally, SiHA was found to have increased surface adhesion (0.7 +/- 0.3 nN) compared to HA (0.5 +/- 0.3 nN). The characterization of the nanoscale variations in surface forces of SiHA and HA will enable an improved understanding of the initial stages of bone-biomaterial bonding.

  15. Reconstruction of electrostatic force microscopy image for nanoscale potential distributions with potential steps

    NASA Astrophysics Data System (ADS)

    Ding, X. D.; Gao, P. F.; Zhao, L. B.; Lin, G. C.

    2017-04-01

    Given the stray capacitance between the probe and sample surface, electrostatic force microscopy (EFM) suffers from the probe averaging effect of electrostatic signals for measuring nanoscale potential distributions. A method for reconstructing an EFM image is presented by using the step response function (SRF) as the system transfer function. The SRF is constructed numerically by conducting finite element method simulations and reconsidering both the probe shape and tip-sample distance. The deconvolution of the probe averaging effect for the electrostatic image is demonstrated using an elaborated sample of graphene ribbons that are used as nanoscale surface potential steps. The lateral resolution of the electrostatic image is improved via deconvolution. The results present a powerful tool for explaining the EFM image to reduce the probe averaging effect effectively, especially for the sample with nanoscale potential steps.

  16. Analytic model of aurorally coupled magnetospheric and ionospheric electrostatic potentials

    NASA Technical Reports Server (NTRS)

    Cornwall, J. M.

    1994-01-01

    This paper describes modest but significant improvements on earlier studies of electrostatic potential structure in the auroral region using the adiabatic auroral arc model. This model has crucial nonlinearities (connected, for example. with aurorally produced ionization) which have hampered analysis; earlier work has either been linear, which I will show is a poor approximation or, if nonlinear, either numerical or too specialized to study parametric dependencies. With certain simplifying assumptions I find new analytic nonlinear solutions fully exhibiting the parametric dependence of potentials on magnetospheric (e.g.. cross-tail potential) and ionospheric (e.g., recombination rate) parameters. No purely phenomenological parameters are introduced. The results are in reasonable agreement with observed average auroral potential drops, inverted-V scale sizes, and dissipation rates. The dissipation rate is quite comparable to tail energization and transport rates and should have a major effect on tail and magnetospheric dynamics. This paper gives various relations between the cross-tail potential and auroral parameters (e.g., total parallel currents and potential drops) which can be studied with existing data sets.

  17. Scattering and confinement dynamics of Dirac particles in external electrostatic and Lorentz scalar potentials

    NASA Astrophysics Data System (ADS)

    M, Haritha; P, Durganandini

    2015-06-01

    We study the scattering and confinement of Dirac particles in external electrostatic and Lorentz scalar potentials. We use a numerical finite difference time -domain method to solve the equation and obtain the particle dynamics. We find qualitatively different dynamical behavior for electrostatic and Lorentz scalar potentials. Electrostatic potentials lead to Klein tunneling and do not exhibit confinement, while Lorentz scalar potentials inhibit Klein tunneling and exhibit confinement.

  18. Footprinting molecular electrostatic potential surfaces for calculation of solvation energies.

    PubMed

    Calero, Christian Solis; Farwer, Jochen; Gardiner, Eleanor J; Hunter, Christopher A; Mackey, Mark; Scuderi, Serena; Thompson, Stuart; Vinter, Jeremy G

    2013-11-07

    A liquid is composed of an ensemble of molecules that populate a large number of different states, so calculation of the solvation energy of a molecule in solution requires a method for summing the interactions with the environment over all of these states. The surface site interaction model for the properties of liquids at equilibrium (SSIMPLE) simplifies the surface of a molecule to a discrete number of specific interaction sites (SSIPs). The thermodynamic properties of these interaction sites can be characterised experimentally, for example, through measurement of association constants for the formation of simple complexes that feature a single H-bonding interaction. Correlation of experimentally determined solution phase H-bond parameters with gas phase ab initio calculations of maxima and minima on molecular electrostatic potential surfaces (MEPS) provides a method for converting gas phase calculations on isolated molecules to parameters that can be used to estimate solution phase interaction free energies. This approach has been generalised using a footprinting technique that converts an MEPS into a discrete set of SSIPs (each described by a polar interaction parameter, εi). These SSIPs represent the molecular recognition properties of the entire surface of the molecule. For example, water is described by four SSIPs, two H-bond donor sites and two H-bond acceptor sites. A liquid mixture is described as an ensemble of SSIPs that represent the components of the mixture at appropriate concentrations. Individual SSIPs are assumed to be independent, so speciation of SSIP contacts can be calculated based on properties of the individual SSIP interactions, which are given by the sum of a polar (εiεj) and a non-polar (E(vdW)) interaction term. Results are presented for calculation the free energies of transfer of a range of organic molecules from the pure liquid into water, from the pure liquid into n-hexadecane, from n-hexadecane into water, from n-octanol into

  19. Electrostatic potentials for metal-oxide surfaces and interfaces

    NASA Astrophysics Data System (ADS)

    Streitz, F. H.; Mintmire, J. W.

    1994-10-01

    As most technologically important metals will form oxides readily, any complete study of adhesion at real metal surfaces must include the metal-oxide interface. The role of this ubiquitous oxide layer cannot be overlooked, as the adhesive properties of the oxide or oxide-metal system can be expected to differ profoundly from the adhesive properties of a bare metal surface. We report on the development of a computational method for molecular-dynamics simulations, which explicitly includes variable charge transfer between anions and cations. This method is found to be capable of describing the elastic properties, surface energies, and surface relaxation of crystalline metal oxides accurately. We discuss in detail results using this method for α-alumina and several of its low-index faces.

  20. Combined depletion and electrostatic forces in polymer-induced membrane adhesion: A theoretical model

    NASA Astrophysics Data System (ADS)

    Raudino, Antonio; Pannuzzo, Martina; Karttunen, Mikko

    2012-02-01

    We develop a semi-quantitative analytical theory to describe adhesion between two identical planar charged surfaces embedded in a polymer-containing electrolyte solution. Polymer chains are uncharged and differ from the solvent by their lower dielectric permittivity. The solution mimics physiological fluids: It contains 0.1 M of monovalent ions and a small number of divalent cations that form tight bonds with the headgroups of charged lipids. The components have heterogeneous spatial distributions. The model was derived self-consistently by combining: (a) a Poisson-Boltzmann like equation for the charge densities, (b) a continuum mean-field theory for the polymer profile, (c) a solvation energy forcing the ions toward the polymer-poor regions, and (d) surface interactions of polymers and electrolytes. We validated the theory via extensive coarse-grained Molecular Dynamics (MD) simulations. The results confirm our analytical model and reveal interesting details not detected by the theory. At high surface charges, polymer chains are mainly excluded from the gap region, while the concentration of ions increases. The model shows a strong coupling between osmotic forces, surface potential and salting-out effects of the slightly polar polymer chains. It highlights some of the key differences in the behaviour of monomeric and polymeric mixed solvents and their responses to Coulomb interactions. Our main findings are: (a) the onset of long-ranged ion-induced polymer depletion force that increases with surface charge density and (b) a polymer-modified repulsive Coulomb force that increases with surface charge density. Overall, the system exhibits homeostatic behaviour, resulting in robustness against variations in the amount of charges. Applications and extensions of the model are briefly discussed.

  1. Tunable Adsorption and Film Formation of Mussel Adhesive Protein by Potential Control.

    PubMed

    Zhang, Fan; Xie, Guoxin; Pan, Jinshan

    2017-01-23

    Mussel adhesive proteins are of great interest in many applications because of their outstanding adhesive property and film-forming ability. Understanding and controlling the film formation and its performance is crucial for the effective use of such proteins. In this study, we focus on the potential controlled film formation and compaction of one mussel adhesive protein, Mefp-1. The adsorption and film-forming behavior of Mefp-1 on a platinum (Pt) substrate under applied potentials were investigated by cyclic voltammetry, potential-controlled electrochemical impedance spectroscopy (EIS), and quartz crystal microbalance with dissipation monitoring (QCM-D). Moreover, microfriction measurements were performed to evaluate the mechanical properties of the Mefp-1 films formed at selected potentials. The results led to the conclusion that Mefp-1 adsorbs on the Pt substrate through both electrostatic and nonelectrostatic interactions and shows an effective blocking effect for the electroactive sites on the substrate. The properties of the adsorbed Mefp-1 film vary with the applied potential, and the compactness of the adsorbed Mefp-1 film can be reversibly tuned by the applied potential.

  2. Amplification of a fast wave by extracting both the kinetic energy and electrostatic potential energy of a large-orbit relativistic electron beam in a coaxial electrostatic wiggler

    SciTech Connect

    Zhang Shichang

    2010-05-15

    Nonlinear model and simulation technique of the interaction and energy transfer between a fast wave and a large-orbit relativistic electron beam in a coaxial electrostatic wiggler are presented. Unlike the situations in a magnetostatic-wiggler free-electron laser (MWFEL) and in an electron cyclotron maser (ECM), the electrostatic potential of the electrons plays an important role and participates in the energy exchange between the wave and the electron beam. Compared to MWFEL and ECM, the coaxial electrostatic-wiggler configuration has a distinguishing peculiarity that besides the electron-beam's kinetic energy, its electrostatic potential energy can be effectively transferred to the fast wave. Simulation shows that wave could be amplified with ultrahigh gain by extracting both the kinetic energy and electrostatic potential energy of the electron beam.

  3. Adhesion of dry and wet electrostatic capture silk of uloborid spider

    NASA Astrophysics Data System (ADS)

    Elettro, Hervé; Neukirch, Sébastien; Antkowiak, Arnaud; Vollrath, Fritz

    2015-08-01

    We demonstrate the impressive adhesive qualities of uloborid spider orb-web capture when dry, which are lost when the nano-filament threads are wetted. A force sensor with a 50 nN-1 mN detection sensitively allowed us to measure quantitatively the stress-strain characteristics of native silk threads in both the original dry state and after wetting by controlled application of water mist with droplet sizes ranging between 3 and 5 μm and densities ranging between 104 and 105 per mm3. Stress forces of between 1 and 5 μN/μm2 in the native, dry multifilament thread puffs were reduced to between 0.1 and 0.5 μN/μm2 in the wetted collapsed state, with strain displacements reducing from between 2 and 5 mm in the dry to 0.10-0.12 mm in the wetted states. We conclude that wetting cribellate threads reduce their van der Waals adhesion with implications on the thread's adhesive strength under tension. This should be considered when discussing the evolutionary transitions of capture silks from the ancestral dry-state nano-filaments of the cribellate spider taxa to the wet-state glue-droplets of the ecribellate taxa.

  4. A new infusion pathway monitoring system utilizing electrostatic induced potential.

    PubMed

    Maki, Hiromichi; Yonezawa, Yoshiharu; Ogawa, Hidekuni; Ninomiya, Ishio; Sada, Kouji; Hamada, Shingo; Hahn, Alien W; Caldwell, W Morton

    2006-01-01

    We have developed a new infusion pathway monitoring system employing linear integrated circuits and a low-power 8-bit single chip microcomputer. The system is available for hospital and home use and it constantly monitors the intactness of the pathway. The sensor is an electro-conductive polymer electrode wrapped around the infusion polyvinyl chloride infusion tube. This records an AC (alternating current) voltage induced on the patient's body by electrostatic coupling from the normal 100 volt, 60 Hz AC power line wiring field in the patient's room. If the injection needle or infusion tube becomes detached, then the system detects changes in the induced AC voltage and alerts the nursing station, via the nurse call system or PHS (personal handy phone System).

  5. Electrostatic Forces: Formulas for the First Derivatives of a Polarizable, Anisotropic Electrostatic Potential Energy Function Based on Machine Learning.

    PubMed

    Mills, Matthew J L; Popelier, Paul L A

    2014-09-09

    Explicit formulas are derived analytically for the first derivatives of a (i) polarizable, (ii) high-rank multipolar electrostatic potential energy function for (iii) flexible molecules. The potential energy function uses a machine learning method called Kriging to predict the local-frame multipole moments of atoms defined via the Quantum Chemical Topology (QCT) approach. These atomic multipole moments then interact via an interaction tensor based on spherical harmonics. Atom-centered local coordinate frames are used, constructed from the internal geometry of the molecular system. The forces involve derivatives of both this geometric dependence and of the trained kriging models. In the near future, these analytical forces will enable molecular dynamics and geometry optimization calculations as part of the QCT force field.

  6. Adhesion properties of potentially probiotic Lactobacillus kefiri to gastrointestinal mucus.

    PubMed

    Carasi, Paula; Ambrosis, Nicolás M; De Antoni, Graciela L; Bressollier, Philippe; Urdaci, María C; Serradell, María de los Angeles

    2014-02-01

    We investigated the mucus-binding properties of aggregating and non-aggregating potentially probiotic strains of kefir-isolated Lactobacillus kefiri, using different substrates. All the strains were able to adhere to commercial gastric mucin (MUCIN) and extracted mucus from small intestine (SIM) and colon (CM). The extraction of surface proteins from bacteria using LiCl or NaOH significantly reduced the adhesion of three selected strains (CIDCA 8348, CIDCA 83115 and JCM 5818); although a significant proportion (up to 50%) of S-layer proteins were not completely eliminated after treatments. The surface (S-layer) protein extracts from all the strains of Lb. kefiri were capable of binding to MUCIN, SIM or CM, and no differences were observed among them. The addition of their own surface protein extract increased adhesion of CIDCA 8348 and 83115 to MUCIN and SIM, meanwhile no changes in adhesion were observed for JCM 5818. None of the seven sugars tested had the ability to inhibit the adhesion of whole bacteria to the three mucus extracts. Noteworthy, the degree of bacterial adhesion reached in the presence of their own surface protein (S-layer) extract decreased to basal levels in the presence of some sugars, suggesting an interaction between the added sugar and the surface proteins. In conclusion, the ability of these food-isolated bacteria to adhere to gastrointestinal mucus becomes an essential issue regarding the biotechnological potentiality of Lb. kefiri for the food industry.

  7. The effect of surface conductivity and adhesivity on the electrostatic manipulation condition for dielectric microparticles using a single probe

    NASA Astrophysics Data System (ADS)

    Fujiwara, Ryo; Hemthavy, Pasomphone; Takahashi, Kunio; Saito, Shigeki

    2016-05-01

    By clarifying the effect of surface conductivity and adhesivity on the electrostatic manipulation condition, a dielectric particle made of any material can be manipulated with surface conductivity. The manipulation system consists of three elements: a conductive probe as a manipulator, a conductive plate as a substrate, and a dielectric particle as the target object for manipulation. The particle can be successfully picked up/placed if a rectangular pulse voltage is applied between the probe and the plate. Four kinds of particle materials are used in the experiment: silica, soda-lime glass, polymethyl methacrylate coated by conductive polymer, and polystyrene coated by surfactant. The radius of each particle is 15 μm. A first-order resistor-capacitor (RC) circuit model is adopted to describe the effect of surface conductivity and adhesivity on the manipulation condition. The manipulation system is modeled as a series circuit consisting of a resistor and a capacitor by considering the surface conductivity. A detachment voltage is defined as the capacitance voltage to detach the particle adhered to the plate or probe. Parameters of the RC model, surface resistance, surface capacitance and detachment voltage are identified by a simulation and measurements. To verify the RC model, the particle’s behavior is observed by a high-speed camera, and the electrical current is measured by an electrometer. A manipulation experiment is demonstrated to show the effectiveness of the model. The particle reaction is observed for each duration and magnitude of the pulse voltage for the manipulation. The optimum pulse voltage for successful manipulation is determined by the parameters of the RC model as the standard. This knowledge is expected to expand the possibility of micro-fabrication technology.

  8. Confusing Aspects in the Calculation of the Electrostatic Potential of an Infinite Line of Charge

    ERIC Educational Resources Information Center

    Jimenez, J. L.; Campos, I.; Roa-Neri, J. A. E.

    2012-01-01

    In this work we discuss the trick of eliminating infinite potential of reference arguing that it corresponds to a constant of integration, in the problem of determining the electrostatic potential of an infinite line of charge with uniform density, and show how the problem must be tackled properly. The usual procedure is confusing for most…

  9. Atomic Charges and the Electrostatic Potential Are Ill-Defined in Degenerate Ground States.

    PubMed

    Bultinck, Patrick; Cardenas, Carlos; Fuentealba, Patricio; Johnson, Paul A; Ayers, Paul W

    2013-11-12

    A system in a spatially degenerate ground state responds in a qualitatively different way to positive and negative point charges. This means that the molecular electrostatic potential is ill-defined for degenerate ground states due to the ill-defined nature of the electron density. It also means that it is impossible, in practice, to define fixed atomic charges for molecular mechanics simulations of molecules with (quasi-)degenerate ground states. Atomic-polarizability-based models and electronegativity-equalization-type models for molecular polarization also fail to capture this effect. We demonstrate the ambiguity in the electrostatic potential using several molecules of different degree of degeneracy, quasi-degeneracy, and symmetry.

  10. Solvation structure of coumarin 1 in acetonitrile: role of the electrostatic solute solvent potential

    NASA Astrophysics Data System (ADS)

    Diraison, M.; Millie, P.; Pommeret, S.; Gustavsson, T.; Mialocq, J.-Cl

    1998-01-01

    A molecular dynamics simulation study of a coumarin 1 molecule solvated in acetonitrile, in its S 0 and S 1 electronic states, is presented. Three solute-solvent interaction potentials, all containing the same Lennard-Jones component but different electrostatic interactions, have been considered. The structure of the solvent around the large dye solute strongly depends on the electrostatic solute-solvent potential, illustrating the crucial role of the local electric field. An accurate description of the charge distribution of the solute is therefore necessary to describe correctly the solute-solvent structure and the solvation energy.

  11. Split-illumination electron holography for improved evaluation of electrostatic potential associated with electrophotography

    SciTech Connect

    Tanigaki, Toshiaki Aizawa, Shinji; Soon Park, Hyun; Sato, Kuniaki; Akase, Zentaro; Matsuda, Tsuyoshi; Murakami, Yasukazu; Shindo, Daisuke; Kawase, Hiromitsu

    2014-03-31

    Precise evaluation of the electrostatic potential distributions of and around samples with multiple charges using electron holography has long been a problem due to unknown perturbation of the reference wave. Here, we report the first practical application of split-illumination electron holography (SIEH) to tackle this problem. This method enables the use of a non-perturbed reference wave distant from the sample. SIEH revealed the electrostatic potential distributions at interfaces of the charged particles used for development in electrophotography and should lead to dramatic improvements in electrophotography.

  12. Free-energy functionals of the electrostatic potential for Poisson-Boltzmann theory.

    PubMed

    Jadhao, Vikram; Solis, Francisco J; de la Cruz, Monica Olvera

    2013-08-01

    In simulating charged systems, it is often useful to treat some ionic components of the system at the mean-field level and solve the Poisson-Boltzmann (PB) equation to get their respective density profiles. The numerically intensive task of solving the PB equation at each step of the simulation can be bypassed using variational methods that treat the electrostatic potential as a dynamic variable. But such approaches require the access to a true free-energy functional: a functional that not only provides the correct solution of the PB equation upon extremization, but also evaluates to the true free energy of the system at its minimum. Moreover, the numerical efficiency of such procedures is further enhanced if the free-energy functional is local and is expressed in terms of the electrostatic potential. Existing PB functionals of the electrostatic potential, while possessing the local structure, are not free-energy functionals. We present a variational formulation with a local free-energy functional of the potential. In addition, we also construct a nonlocal free-energy functional of the electrostatic potential. These functionals are suited for employment in simulation schemes based on the ideas of dynamical optimization.

  13. On the structures and mapping of auroral electrostatic potentials

    NASA Technical Reports Server (NTRS)

    Chiu, Y. T.; Newman, A. L.; Cornwall, J. M.

    1981-01-01

    The mapping of magnetospheric and ionospheric electric fields in a kinetic model of magnetospheric-ionospheric electrodynamic coupling proposed for the aurora is examined. One feature is the generalization of the kinetic current-potential relationship to the return current region (identified as a region where the parallel drop from magnetosphere to ionosphere is positive); such a return current always exists unless the ionosphere is electrically charged to grossly unphysical values. A coherent phenomenological picture of both the low energy return current and the high energy precipitation of an inverted-V is given. The mapping between magnetospheric and ionospheric electric fields is phrased in terms of a Green's function which acts as a filter, emphasizing magnetospheric latitudinal spatial scales of order (when mapped to the ionosphere) 50 to 150 km. This same length, when multiplied by electric fields just above the ionosphere, sets the scale for potential drops between the ionosphere and equatorial magnetosphere.

  14. Determination of a PAF antagonist pharmacophore using combined Molecular Electrostatic Potential and Molecular Lipophilicity Potential.

    PubMed

    Le Solleu, H; Langlois, M H; Kummer, E; Dubost, J P

    1994-11-01

    PAF is a potent lipid mediator involved in many pathological disorders, such as platelet aggregation, immuno-inflammatory reactions, vascular disorders, septic shock and bronchoconstriction. We chose to study the electronic and lipophilic properties of eleven PAF antagonists, comprising five tetrahydrofuran derivatives, four hetrazepines, the ginkgolide BN-52021 and the pyrrolo-thiazole derivative RP-59227. A Molecular Electrostatic Potential (MEP) contour drawn at -25 kCal/Mol shows three electronegative areas in most compounds. Two areas can be considered as analogous to those described in the so-called "Cache-Oreille" (Earmuff) Model. Molecular Lipophilicity Potential (MLP) analysis allows us to characterise one hydrophilic area, localised at the same place as one of the electronegative areas, and two lipophilic areas, of which the biggest draws a typical "sock" contour. These three areas represent the minimal requirements for a high affinity to the PAF receptor. MEP and MLP results are here combined to propose a pharmacophore for PAF antagonists, including two lipophilic areas, two hydrophilic and electronegative areas and an electronegative zone with no particular hydrophilic behaviour.

  15. Student Reasoning about Electrostatic and Gravitational Potential Energy: An Exploratory Study with Interdisciplinary Consequences

    ERIC Educational Resources Information Center

    Lindsey, Beth A.

    2014-01-01

    This paper describes an investigation into student reasoning about potential energy in the context of introductory electrostatics. Similar incorrect reasoning patterns emerged both in written questions administered after relevant instruction and in one-on-one interviews. These reasoning patterns are also prevalent in responses to questions posed…

  16. Accelerating electrostatic surface potential calculation with multi-scale approximation on graphics processing units.

    PubMed

    Anandakrishnan, Ramu; Scogland, Tom R W; Fenley, Andrew T; Gordon, John C; Feng, Wu-chun; Onufriev, Alexey V

    2010-06-01

    Tools that compute and visualize biomolecular electrostatic surface potential have been used extensively for studying biomolecular function. However, determining the surface potential for large biomolecules on a typical desktop computer can take days or longer using currently available tools and methods. Two commonly used techniques to speed-up these types of electrostatic computations are approximations based on multi-scale coarse-graining and parallelization across multiple processors. This paper demonstrates that for the computation of electrostatic surface potential, these two techniques can be combined to deliver significantly greater speed-up than either one separately, something that is in general not always possible. Specifically, the electrostatic potential computation, using an analytical linearized Poisson-Boltzmann (ALPB) method, is approximated using the hierarchical charge partitioning (HCP) multi-scale method, and parallelized on an ATI Radeon 4870 graphical processing unit (GPU). The implementation delivers a combined 934-fold speed-up for a 476,040 atom viral capsid, compared to an equivalent non-parallel implementation on an Intel E6550 CPU without the approximation. This speed-up is significantly greater than the 42-fold speed-up for the HCP approximation alone or the 182-fold speed-up for the GPU alone.

  17. Textbook Treatments of Electrostatic Potential Maps in General and Organic Chemistry

    ERIC Educational Resources Information Center

    Hinze, Scott R.; Williamson, Vickie M.; Deslongchamps, Ghislain; Shultz, Mary Jane; Williamson, Kenneth C.; Rapp, David N.

    2013-01-01

    Electrostatic potential maps (EPMs) allow for representation of key molecular-level information in a relatively simple and inexpensive format. As these visualizations become more prevalent in instruction, it is important to determine how students are exposed to them and supported in their use. A systematic review of current general and organic…

  18. Accelerating Electrostatic Surface Potential Calculation with Multiscale Approximation on Graphics Processing Units

    PubMed Central

    Anandakrishnan, Ramu; Scogland, Tom R. W.; Fenley, Andrew T.; Gordon, John C.; Feng, Wu-chun; Onufriev, Alexey V.

    2010-01-01

    Tools that compute and visualize biomolecular electrostatic surface potential have been used extensively for studying biomolecular function. However, determining the surface potential for large biomolecules on a typical desktop computer can take days or longer using currently available tools and methods. Two commonly used techniques to speed up these types of electrostatic computations are approximations based on multi-scale coarse-graining and parallelization across multiple processors. This paper demonstrates that for the computation of electrostatic surface potential, these two techniques can be combined to deliver significantly greater speed-up than either one separately, something that is in general not always possible. Specifically, the electrostatic potential computation, using an analytical linearized Poisson Boltzmann (ALPB) method, is approximated using the hierarchical charge partitioning (HCP) multiscale method, and parallelized on an ATI Radeon 4870 graphical processing unit (GPU). The implementation delivers a combined 934-fold speed-up for a 476,040 atom viral capsid, compared to an equivalent non-parallel implementation on an Intel E6550 CPU without the approximation. This speed-up is significantly greater than the 42-fold speed-up for the HCP approximation alone or the 182-fold speed-up for the GPU alone. PMID:20452792

  19. Potentialities of ultrasounds for the nondestructive evaluation of cell adhesion.

    PubMed

    Myrdycz, A; Lefebvre, F; Ouaftouh, M; Monchau, F; Callens, D; Hildebrand, H F

    1999-08-01

    The aim of this paper is to present the potentialities of ultrasounds to investigate the mechanical properties of a cell/substrate interface. The adhesion process plays a major role in the development of osteoblastic cells on various substrates used in orthopedic applications such as metals, bioceramics, etc. Particularly, cell adherence appears to be a critical factor in the colonization process. High-frequency and low-power ultrasounds seem to be an appropriate tool for a nondestructive evaluation of interface properties. First, we present the results obtained with bulk longitudinal and shear waves under an arbitrary incidence over an aluminum-adhesive interface. This study was performed for an industrial application of bonding. The results clearly show the sensitivity of shear waves for the evaluation of the adhesion quality owing to the shear solicitations at the interface they induce. A model of ultrasound interactions with a boundary subject to varying degrees of adhesion has been developed and compared to the experiments. Second, we investigated osteoblastic cell cultures with a high-frequency acoustic microscope working at 50 MHz. The images obtained in the shear mode reveal a better contrast than those obtained in the longitudinal mode. For the time being, these results are qualitative, and theoretical models have to be developed according to the point of view of biologists.

  20. Negative electrostatic surface potential of protein sites specific for anionic ligands.

    PubMed Central

    Ledvina, P S; Yao, N; Choudhary, A; Quiocho, F A

    1996-01-01

    Determination of the crystal structure of an "open" unliganded active mutant (T141D) form of the Escherichia coli phosphate receptor for active transport has allowed calculation of the electrostatic surface potential for it and two other comparably modeled receptor structures (wild type and D137N). A discovery of considerable implication is the intensely negative potential of the phosphate-binding cleft. We report similar findings for a sulfate transport receptor, a DNA-binding protein, and, even more dramatically, redox proteins. Evidently, for proteins such as these, which rely almost exclusively on hydrogen bonding for anion interactions and electrostatic balance, a noncomplementary surface potential is not a barrier to binding. Moreover, experimental results show that the exquisite specificity and high affinity of the phosphate and sulfate receptors for unions are insensitive to modulations of charge potential, but extremely sensitive to conditions that leave a hydrogen bond donor or acceptor unpaired. Images Fig. 1 Fig. 2 Fig. 3 PMID:8692896

  1. Negative electrostatic surface potential of protein sites specific for anionic ligands.

    PubMed

    Ledvina, P S; Yao, N; Choudhary, A; Quiocho, F A

    1996-06-25

    Determination of the crystal structure of an "open" unliganded active mutant (T141D) form of the Escherichia coli phosphate receptor for active transport has allowed calculation of the electrostatic surface potential for it and two other comparably modeled receptor structures (wild type and D137N). A discovery of considerable implication is the intensely negative potential of the phosphate-binding cleft. We report similar findings for a sulfate transport receptor, a DNA-binding protein, and, even more dramatically, redox proteins. Evidently, for proteins such as these, which rely almost exclusively on hydrogen bonding for anion interactions and electrostatic balance, a noncomplementary surface potential is not a barrier to binding. Moreover, experimental results show that the exquisite specificity and high affinity of the phosphate and sulfate receptors for unions are insensitive to modulations of charge potential, but extremely sensitive to conditions that leave a hydrogen bond donor or acceptor unpaired.

  2. Visualizing the Positive-Negative Interface of Molecular Electrostatic Potentials as an Educational Tool for Assigning Chemical Polarity

    ERIC Educational Resources Information Center

    Schonborn, Konrad; Host, Gunnar; Palmerius, Karljohan

    2010-01-01

    To help in interpreting the polarity of a molecule, charge separation can be visualized by mapping the electrostatic potential at the van der Waals surface using a color gradient or by indicating positive and negative regions of the electrostatic potential using different colored isosurfaces. Although these visualizations capture the molecular…

  3. Theory, experiment and computer simulation of the electrostatic potential at crystal/electrolyte interfaces

    SciTech Connect

    Zarzycki, Piotr P.; Rosso, Kevin M.; Chatman, Shawn ME; Preocanin, Tajana; Kallay, Nikola; Piasecki, Wojciech

    2010-10-01

    In this feature article we discuss recent advances and challenges in measuring, analyzing and interpreting the electrostatic potential development at crystal/electrolyte interfaces. We highlight progress toward fundamental understanding of historically difficult aspects, including point of zero potential estimation for single faces of single crystals, the non-equilibrium pH titration hysteresis loop, and the origin of nonlinearities in the titration response. It has been already reported that the electrostatic potential is strongly affected by many second order type phenomena such as: surface heterogeneity, (sub)surface transformations, charge transfer reactions, and additional potential jumps at crystal face edges and/or Schottky barriers. Single-crystal electrode potentials seem particularly sensitive to these phenomena, which makes interpretation of experimental observations complicated. We hope that recent theory developments in our research group including an analytical model of titration hysteresis, a perturbative surface potential expansion, and a new surface complexation model that incorporates charge transfer processes will help experimental data analysis, and provide unique insights into the electrostatic response of nonpolarizable single-crystal electrodes.

  4. Applying a potential across a biomembrane: electrostatic contribution to the bending rigidity and membrane instability.

    PubMed

    Ambjörnsson, Tobias; Lomholt, Michael A; Hansen, Per Lyngs

    2007-05-01

    We investigate the effect on biomembrane mechanical properties due to the presence an external potential for a nonconductive incompressible membrane surrounded by different electrolytes. By solving the Debye-Hückel and Laplace equations for the electrostatic potential and using the relevant stress-tensor we find (1) in the small screening length limit, where the Debye screening length is smaller than the distance between the electrodes, the screening certifies that all electrostatic interactions are short range and the major effect of the applied potential is to decrease the membrane tension and increase the bending rigidity; explicit expressions for electrostatic contribution to the tension and bending rigidity are derived as a function of the applied potential, the Debye screening lengths, and the dielectric constants of the membrane and the solvents. For sufficiently large voltages the negative contribution to the tension is expected to cause a membrane stretching instability. (2) For the dielectric limit, i.e., no salt (and small wave vectors compared to the distance between the electrodes), when the dielectric constant on the two sides are different the applied potential induces an effective (unscreened) membrane charge density, whose long-range interaction is expected to lead to a membrane undulation instability.

  5. Adhesions

    MedlinePlus

    Adhesions are bands of scar-like tissue. Normally, internal tissues and organs have slippery surfaces so they can shift easily as the body moves. Adhesions cause tissues and organs to stick together. They ...

  6. Adhesion

    MedlinePlus

    ... the intestines, adhesions can cause partial or complete bowel obstruction . Adhesions inside the uterine cavity, called Asherman syndrome , ... 1. Read More Appendicitis Asherman syndrome Glaucoma Infertility Intestinal obstruction Review Date 4/5/2016 Updated by: Irina ...

  7. Stigmatellin probes the electrostatic potential in the QB site of the photosynthetic reaction center.

    PubMed

    Gerencsér, László; Boros, Bogáta; Derrien, Valerie; Hanson, Deborah K; Wraight, Colin A; Sebban, Pierre; Maróti, Péter

    2015-01-20

    The electrostatic potential in the secondary quinone (QB) binding site of the reaction center (RC) of the photosynthetic bacterium Rhodobacter sphaeroides determines the rate and free energy change (driving force) of electron transfer to QB. It is controlled by the ionization states of residues in a strongly interacting cluster around the QB site. Reduction of the QB induces change of the ionization states of residues and binding of protons from the bulk. Stigmatellin, an inhibitor of the mitochondrial and photosynthetic respiratory chain, has been proven to be a unique voltage probe of the QB binding pocket. It binds to the QB site with high affinity, and the pK value of its phenolic group monitors the local electrostatic potential with high sensitivity. Investigations with different types of detergent as a model system of isolated RC revealed that the pK of stigmatellin was controlled overwhelmingly by electrostatic and slightly by hydrophobic interactions. Measurements showed a high pK value (>11) of stigmatellin in the QB pocket of the dark-state wild-type RC, indicating substantial negative potential. When the local electrostatics of the QB site was modulated by a single mutation, L213Asp → Ala, or double mutations, L213Asp-L212Glu → Ala-Ala (AA), the pK of stigmatellin dropped to 7.5 and 7.4, respectively, which corresponds to a >210 mV increase in the electrostatic potential relative to the wild-type RC. This significant pK drop (ΔpK > 3.5) decreased dramatically to (ΔpK > 0.75) in the RC of the compensatory mutant (AA+M44Asn → AA+M44Asp). Our results indicate that the L213Asp is the most important actor in the control of the electrostatic potential in the QB site of the dark-state wild-type RC, in good accordance with conclusions of former studies using theoretical calculations or light-induced charge recombination assay.

  8. Charged patchy particle models in explicit salt: Ion distributions, electrostatic potentials, and effective interactions

    SciTech Connect

    Yigit, Cemil; Dzubiella, Joachim; Heyda, Jan

    2015-08-14

    We introduce a set of charged patchy particle models (CPPMs) in order to systematically study the influence of electrostatic charge patchiness and multipolarity on macromolecular interactions by means of implicit-solvent, explicit-ion Langevin dynamics simulations employing the Gromacs software. We consider well-defined zero-, one-, and two-patched spherical globules each of the same net charge and (nanometer) size which are composed of discrete atoms. The studied mono- and multipole moments of the CPPMs are comparable to those of globular proteins with similar size. We first characterize ion distributions and electrostatic potentials around a single CPPM. Although angle-resolved radial distribution functions reveal the expected local accumulation and depletion of counter- and co-ions around the patches, respectively, the orientation-averaged electrostatic potential shows only a small variation among the various CPPMs due to space charge cancellations. Furthermore, we study the orientation-averaged potential of mean force (PMF), the number of accumulated ions on the patches, as well as the CPPM orientations along the center-to-center distance of a pair of CPPMs. We compare the PMFs to the classical Derjaguin-Verwey-Landau-Overbeek theory and previously introduced orientation-averaged Debye-Hückel pair potentials including dipolar interactions. Our simulations confirm the adequacy of the theories in their respective regimes of validity, while low salt concentrations and large multipolar interactions remain a challenge for tractable theoretical descriptions.

  9. Mutantelec: An In Silico mutation simulation platform for comparative electrostatic potential profiling of proteins.

    PubMed

    Valdebenito-Maturana, Braulio; Reyes-Suarez, Jose Antonio; Henriquez, Jaime; Holmes, David S; Quatrini, Raquel; Pohl, Ehmke; Arenas-Salinas, Mauricio

    2017-03-15

    The electrostatic potential plays a key role in many biological processes like determining the affinity of a ligand to a given protein target, and they are responsible for the catalytic activity of many enzymes. Understanding the effect that amino acid mutations will have on the electrostatic potential of a protein, will allow a thorough understanding of which residues are the most important in a protein. MutantElec, is a friendly web application for in silico generation of site-directed mutagenesis of proteins and the comparison of electrostatic potential between the wild type protein and the mutant(s), based on the three-dimensional structure of the protein. The effect of the mutation is evaluated using different approach to the traditional surface map. MutantElec provides a graphical display of the results that allows the visualization of changes occurring at close distance from the mutation and thus uncovers the local and global impact of a specific change. © 2017 Wiley Periodicals, Inc.

  10. A simple derivation for amplitude and time period of charged particles in an electrostatic bathtub potential

    NASA Astrophysics Data System (ADS)

    Prathap Reddy, K.

    2016-11-01

    An ‘electrostatic bathtub potential’ is defined and analytical expressions for the time period and amplitude of charged particles in this potential are obtained and compared with simulations. These kinds of potentials are encountered in linear electrostatic ion traps, where the potential along the axis appears like a bathtub. Ion traps are used in basic physics research and mass spectrometry to store ions; these stored ions make oscillatory motion within the confined volume of the trap. Usually these traps are designed and studied using ion optical software, but in this work the bathtub potential is reproduced by making two simple modifications to the harmonic oscillator potential. The addition of a linear ‘k 1|x|’ potential makes the simple harmonic potential curve steeper with a sharper turn at the origin, while the introduction of a finite-length zero potential region at the centre reproduces the flat region of the bathtub curve. This whole exercise of modelling a practical experimental situation in terms of a well-known simple physics problem may generate interest among readers.

  11. Determining polarizable force fields with electrostatic potentials from quantum mechanical linear response theory

    NASA Astrophysics Data System (ADS)

    Wang, Hao; Yang, Weitao

    2016-06-01

    We developed a new method to calculate the atomic polarizabilities by fitting to the electrostatic potentials (ESPs) obtained from quantum mechanical (QM) calculations within the linear response theory. This parallels the conventional approach of fitting atomic charges based on electrostatic potentials from the electron density. Our ESP fitting is combined with the induced dipole model under the perturbation of uniform external electric fields of all orientations. QM calculations for the linear response to the external electric fields are used as input, fully consistent with the induced dipole model, which itself is a linear response model. The orientation of the uniform external electric fields is integrated in all directions. The integration of orientation and QM linear response calculations together makes the fitting results independent of the orientations and magnitudes of the uniform external electric fields applied. Another advantage of our method is that QM calculation is only needed once, in contrast to the conventional approach, where many QM calculations are needed for many different applied electric fields. The molecular polarizabilities obtained from our method show comparable accuracy with those from fitting directly to the experimental or theoretical molecular polarizabilities. Since ESP is directly fitted, atomic polarizabilities obtained from our method are expected to reproduce the electrostatic interactions better. Our method was used to calculate both transferable atomic polarizabilities for polarizable molecular mechanics' force fields and nontransferable molecule-specific atomic polarizabilities.

  12. Charge density distributions derived from smoothed electrostatic potential functions: design of protein reduced point charge models.

    PubMed

    Leherte, Laurence; Vercauteren, Daniel P

    2011-10-01

    To generate reduced point charge models of proteins, we developed an original approach to hierarchically locate extrema in charge density distribution functions built from the Poisson equation applied to smoothed molecular electrostatic potential (MEP) functions. A charge fitting program was used to assign charge values to the so-obtained reduced representations. In continuation to a previous work, the Amber99 force field was selected. To easily generate reduced point charge models for protein structures, a library of amino acid templates was designed. Applications to four small peptides, a set of 53 protein structures, and four KcsA ion channel models, are presented. Electrostatic potential and solvation free energy values generated by the reduced models are compared with the corresponding values obtained using the original set of atomic charges. Results are in closer agreement with the original all-atom electrostatic properties than those obtained with a previous reduced model that was directly built from the smoothed MEP functions [Leherte and Vercauteren in J Chem Theory Comput 5:3279-3298, 2009].

  13. Gay-Berne and electrostatic multipole based coarse-grain potential in implicit solvent

    NASA Astrophysics Data System (ADS)

    Wu, Johnny; Zhen, Xia; Shen, Hujun; Li, Guohui; Ren, Pengyu

    2011-10-01

    A general, transferable coarse-grain (CG) framework based on the Gay-Berne potential and electrostatic point multipole expansion is presented for polypeptide simulations. The solvent effect is described by the Generalized Kirkwood theory. The CG model is calibrated using the results of all-atom simulations of model compounds in solution. Instead of matching the overall effective forces produced by atomic models, the fundamental intermolecular forces such as electrostatic, repulsion-dispersion, and solvation are represented explicitly at a CG level. We demonstrate that the CG alanine dipeptide model is able to reproduce quantitatively the conformational energy of all-atom force fields in both gas and solution phases, including the electrostatic and solvation components. Replica exchange molecular dynamics and microsecond dynamic simulations of polyalanine of 5 and 12 residues reveal that the CG polyalanines fold into "alpha helix" and "beta sheet" structures. The 5-residue polyalanine displays a substantial increase in the "beta strand" fraction relative to the 12-residue polyalanine. The detailed conformational distribution is compared with those reported from recent all-atom simulations and experiments. The results suggest that the new coarse-graining approach presented in this study has the potential to offer both accuracy and efficiency for biomolecular modeling.

  14. Determining polarizable force fields with electrostatic potentials from quantum mechanical linear response theory.

    PubMed

    Wang, Hao; Yang, Weitao

    2016-06-14

    We developed a new method to calculate the atomic polarizabilities by fitting to the electrostatic potentials (ESPs) obtained from quantum mechanical (QM) calculations within the linear response theory. This parallels the conventional approach of fitting atomic charges based on electrostatic potentials from the electron density. Our ESP fitting is combined with the induced dipole model under the perturbation of uniform external electric fields of all orientations. QM calculations for the linear response to the external electric fields are used as input, fully consistent with the induced dipole model, which itself is a linear response model. The orientation of the uniform external electric fields is integrated in all directions. The integration of orientation and QM linear response calculations together makes the fitting results independent of the orientations and magnitudes of the uniform external electric fields applied. Another advantage of our method is that QM calculation is only needed once, in contrast to the conventional approach, where many QM calculations are needed for many different applied electric fields. The molecular polarizabilities obtained from our method show comparable accuracy with those from fitting directly to the experimental or theoretical molecular polarizabilities. Since ESP is directly fitted, atomic polarizabilities obtained from our method are expected to reproduce the electrostatic interactions better. Our method was used to calculate both transferable atomic polarizabilities for polarizable molecular mechanics' force fields and nontransferable molecule-specific atomic polarizabilities.

  15. Assessing potential peptide targeting ligands by quantification of cellular adhesion of model nanoparticles under flow conditions.

    PubMed

    Broda, Ellen; Mickler, Frauke Martina; Lächelt, Ulrich; Morys, Stephan; Wagner, Ernst; Bräuchle, Christoph

    2015-09-10

    Sophisticated drug delivery systems are coated with targeting ligands to improve the specific adhesion to surface receptors on diseased cells. In our study, we developed a method with which we assessed the potential of peptide ligands to specifically bind to receptor overexpressing target cells. Therefore, a microfluidic setup was used where the cellular adhesion of nanoparticles with ligand and of control nanoparticles was observed in parallel under the same experimental conditions. The effect of the ligand on cellular binding was quantified by counting the number of adhered nanoparticles with ligand and differently labeled control nanoparticles on single cells after incubation under flow conditions. To provide easy-to-synthesize, stable and reproducible nanoparticles which mimic the surface characteristics of drug delivery systems and meet the requirements for quantitative analysis, latex beads based on amine-modified polystyrene were used as model nanoparticles. Two short peptides were tested to serve as targeting ligand on the beads by increasing the specific binding to HuH7 cells. The c-Met binding peptide cMBP2 was used for hepatocyte growth factor receptor (c-Met) targeting and the peptide B6 for transferrin receptor (TfR) targeting. The impact of the targeting peptide on binding was investigated by comparing the beads with ligand to different internal control beads: 1) without ligand and tailored surface charge (electrostatic control) and 2) with scrambled peptide and similar surface charge, but a different amino acid sequence (specificity control). Our results demonstrate that the method is very useful to select suitable targeting ligands for specific nanoparticle binding to receptor overexpressing tumor cells. We show that the cMBP2 ligand specifically enhances nanoparticle adhesion to target cells, whereas the B6 peptide mediates binding to tumor cells mainly by nonspecific interactions. All together, we suggest that cMBP2 is a suitable choice for

  16. Atomic resolution electrostatic potential mapping of graphene sheets by off-axis electron holography

    SciTech Connect

    Cooper, David; Pan, Cheng-Ta; Haigh, Sarah

    2014-06-21

    Off-axis electron holography has been performed at atomic resolution with the microscope operated at 80 kV to provide electrostatic potential maps from single, double, and triple layer graphene. These electron holograms have been reconstructed in order to obtain information about atomically resolved and mean inner potentials. We propose that off-axis electron holography can now be used to measure the electrical properties in a range of two-dimensional semiconductor materials and three dimensional devices comprising stacked layers of films to provide important information about their electrical properties.

  17. On the origin of the electrostatic surface potential of Aspergillus niger spores in acidic environments.

    PubMed

    Wargenau, Andreas; Fleissner, André; Bolten, Christoph Josef; Rohde, Manfred; Kampen, Ingo; Kwade, Arno

    2011-12-01

    The electrostatic surface potential of fungal spores is generally regarded as potentially influencing spore aggregation and pellet formation in submerged cultures of filamentous fungi. Spores of Aspergillus niger are typically characterized by negative zeta potentials over a wide range of pH values. In this study, this particular behavior is ascribed to the presence of an extensive melanin coating. It is proposed on the basis of zeta potential and pigment extraction experiments that this outermost layer affects the pH-dependent surface potential in two manners: (i) by the addition of negative charges to the spore surface and (ii) by the pH-dependent release of melanin pigment. Chemical analyses revealed that deprotonation of melanin-bound carboxyl groups is most probably responsible for pigment release under acidic conditions. These findings were incorporated into a simple model which has the ability to qualitatively explain the results of zeta potential experiments and, moreover, to provide the basis for quantitative investigations on the role of electrostatics in spore aggregation.

  18. Packing constraints and electrostatic surface potentials determine transmembrane asymmetry of phosphatidylethanol.

    PubMed Central

    Victorov, A V; Janes, N; Taraschi, T F; Hoek, J B

    1997-01-01

    The energetic determinants of the distribution of anionic phospholipids across a phosphatidylcholine (PtdCho) bilayer with different packing constraints in the two leaflets were studied, using (13)CH2-ethyl-labeled phosphatidylethanol (PtdEth) as a (13)C NMR membrane probe. PtdEth is unique in exhibiting a split (13)CH2-ethyl resonance in sonicated vesicles, the two components originating from the inner and outer leaflets, thus permitting the determination of the PtdEth concentration in each leaflet. Small and large unilamellar PtdEth-PtdCho vesicles were prepared in solutions of different ionic strengths. A quantitative expression for the transbilayer distribution of PtdEth, based on the balance between steric and electrostatic factors, was derived. The transbilayer difference in packing constraints was obtained from the magnitude of the PtdEth signal splitting. The electrostatic contribution could be satisfactorily described by the transmembrane difference in Gouy-Chapman surface potentials. At low (0.1-0.25%) PtdEth levels and high (up to 500 mM) salt concentrations, PtdEth had a marked fivefold preference for the inner leaflet, presumably because of its small headgroup, which favors tighter packing. At higher PtdEth content (4.8-9.1%) and low salt concentrations, where electrostatic repulsion becomes a dominant factor, the asymmetry was markedly reduced and an almost even distribution across the bilayer was obtained. In less curved, large vesicles, where packing constraints in the two leaflets are approximately the same, the PtdEth distribution was almost symmetrical. This study is the first quantitative analysis of the balance between steric and electrostatic factors that determines the equilibrium transbilayer distribution of charged membrane constituents. PMID:9168034

  19. Electrostatic-Force-Assisted Dispensing Printing to Construct High-Aspect-Ratio of 0.79 Electrodes on a Textured Surface with Improved Adhesion and Contact Resistivity

    PubMed Central

    Shin, Dong-Youn; Yoo, Sung-Soo; Song, Hee-eun; Tak, Hyowon; Byun, Doyoung

    2015-01-01

    As a novel route to construct fine and abnormally high-aspect-ratio electrodes with excellent adhesion and reduced contact resistivity on a textured surface, an electrostatic-force-assisted dispensing printing technique is reported and compared with conventional dispensing and electrohydrodynamic jet printing techniques. The electrostatic force applied between a silver paste and the textured surface of a crystalline silicon solar cell wafer significantly improves the physical adhesion of the electrodes, whereas those fabricated using a conventional dispensing printing technique peel off with a silver paste containing 2 wt% of a fluorosurfactant. Moreover, the contact resistivity and dimensionless deviation of total resistance are significantly reduced from 2.19 ± 1.53 mΩ·cm2 to 0.98 ± 0.92 mΩ·cm2 and from 0.10 to 0.03, respectively. By utilizing electrodes with an abnormally high-aspect-ratio of 0.79 (the measured thickness and width are 30.4 μm and 38.3 μm, respectively), the cell efficiency is 17.2% on a polycrystalline silicon solar cell with an emitter sheet resistance of 60 Ω/sq. This cell efficiency is considerably higher than previously reported values obtained using a conventional electrohydrodynamic jet printing technique, by +0.48–3.5%p. PMID:26576857

  20. Electrostatic-Force-Assisted Dispensing Printing to Construct High-Aspect-Ratio of 0.79 Electrodes on a Textured Surface with Improved Adhesion and Contact Resistivity.

    PubMed

    Shin, Dong-Youn; Yoo, Sung-Soo; Song, Hee-eun; Tak, Hyowon; Byun, Doyoung

    2015-11-18

    As a novel route to construct fine and abnormally high-aspect-ratio electrodes with excellent adhesion and reduced contact resistivity on a textured surface, an electrostatic-force-assisted dispensing printing technique is reported and compared with conventional dispensing and electrohydrodynamic jet printing techniques. The electrostatic force applied between a silver paste and the textured surface of a crystalline silicon solar cell wafer significantly improves the physical adhesion of the electrodes, whereas those fabricated using a conventional dispensing printing technique peel off with a silver paste containing 2 wt% of a fluorosurfactant. Moreover, the contact resistivity and dimensionless deviation of total resistance are significantly reduced from 2.19 ± 1.53 mΩ · cm(2) to 0.98 ± 0.92 mΩ · cm(2) and from 0.10 to 0.03, respectively. By utilizing electrodes with an abnormally high-aspect-ratio of 0.79 (the measured thickness and width are 30.4 μm and 38.3 μm, respectively), the cell efficiency is 17.2% on a polycrystalline silicon solar cell with an emitter sheet resistance of 60 Ω/sq. This cell efficiency is considerably higher than previously reported values obtained using a conventional electrohydrodynamic jet printing technique, by +0.48-3.5%p.

  1. Electrostatic-Force-Assisted Dispensing Printing to Construct High-Aspect-Ratio of 0.79 Electrodes on a Textured Surface with Improved Adhesion and Contact Resistivity

    NASA Astrophysics Data System (ADS)

    Shin, Dong-Youn; Yoo, Sung-Soo; Song, Hee-Eun; Tak, Hyowon; Byun, Doyoung

    2015-11-01

    As a novel route to construct fine and abnormally high-aspect-ratio electrodes with excellent adhesion and reduced contact resistivity on a textured surface, an electrostatic-force-assisted dispensing printing technique is reported and compared with conventional dispensing and electrohydrodynamic jet printing techniques. The electrostatic force applied between a silver paste and the textured surface of a crystalline silicon solar cell wafer significantly improves the physical adhesion of the electrodes, whereas those fabricated using a conventional dispensing printing technique peel off with a silver paste containing 2 wt% of a fluorosurfactant. Moreover, the contact resistivity and dimensionless deviation of total resistance are significantly reduced from 2.19 ± 1.53 mΩ·cm2 to 0.98 ± 0.92 mΩ·cm2 and from 0.10 to 0.03, respectively. By utilizing electrodes with an abnormally high-aspect-ratio of 0.79 (the measured thickness and width are 30.4 μm and 38.3 μm, respectively), the cell efficiency is 17.2% on a polycrystalline silicon solar cell with an emitter sheet resistance of 60 Ω/sq. This cell efficiency is considerably higher than previously reported values obtained using a conventional electrohydrodynamic jet printing technique, by +0.48-3.5%p.

  2. Self-consistent electrostatic potential due to trapped plasma in the magnetosphere

    NASA Technical Reports Server (NTRS)

    Miller, Ronald H.; Khazanov, George V.

    1993-01-01

    A steady state solution for the self-consistent electrostatic potential due to a plasma confined in a magnetic flux tube is considered. A steady state distribution function is constructed for the trapped particles from the constants of the motion, in the absence of waves and collisions. Using Liouville's theorem, the particle density along the geomagnetic field is determined and found to depend on the local magnetic field, self-consistent electric potential, and the equatorial plasma distribution function. A hot anisotropic magnetospheric plasma in steady state is modeled by a bi-Maxwellian at the equator. The self-consistent electric potential along the magnetic field is calculated assuming quasineutrality, and the potential drop is found to be approximately equal to the average kinetic energy of the equatorially trapped plasma. The potential is compared with that obtained by Alfven and Faelthammar (1963).

  3. An analytical approach to computing biomolecular electrostatic potential. II. Validation and applications

    NASA Astrophysics Data System (ADS)

    Gordon, John C.; Fenley, Andrew T.; Onufriev, Alexey

    2008-08-01

    An ability to efficiently compute the electrostatic potential produced by molecular charge distributions under realistic solvation conditions is essential for a variety of applications. Here, the simple closed-form analytical approximation to the Poisson equation rigorously derived in Part I for idealized spherical geometry is tested on realistic shapes. The effects of mobile ions are included at the Debye-Hückel level. The accuracy of the resulting closed-form expressions for electrostatic potential is assessed through comparisons with numerical Poisson-Boltzmann (NPB) reference solutions on a test set of 580 representative biomolecular structures under typical conditions of aqueous solvation. For each structure, the deviation from the reference is computed for a large number of test points placed near the dielectric boundary (molecular surface). The accuracy of the approximation, averaged over all test points in each structure, is within 0.6 kcal/mol/|e|~kT per unit charge for all structures in the test set. For 91.5% of the individual test points, the deviation from the NPB potential is within 0.6 kcal/mol/|e|. The deviations from the reference decrease with increasing distance from the dielectric boundary: The approximation is asymptotically exact far away from the source charges. Deviation of the overall shape of a structure from ideal spherical does not, by itself, appear to necessitate decreased accuracy of the approximation. The largest deviations from the NPB reference are found inside very deep and narrow indentations that occur on the dielectric boundaries of some structures. The dimensions of these pockets of locally highly negative curvature are comparable to the size of a water molecule; the applicability of a continuum dielectric models in these regions is discussed. The maximum deviations from the NPB are reduced substantially when the boundary is smoothed by using a larger probe radius (3 A˚) to generate the molecular surface. A detailed accuracy

  4. First-principles electrostatic potentials for reliable alignment at interfaces and defects.

    PubMed

    Sundararaman, Ravishankar; Ping, Yuan

    2017-03-14

    The alignment of electrostatic potential between different atomic configurations is necessary for first-principles calculations of band offsets across interfaces and formation energies of charged defects. However, strong oscillations of this potential at the atomic scale make alignment challenging, especially when atomic geometries change considerably from bulk to the vicinity of defects and interfaces. We introduce a method to suppress these strong oscillations by eliminating the deep wells in the potential at each atom. We demonstrate that this method considerably improves the system-size convergence of a wide range of first-principles predictions that depend on the alignment of electrostatic potentials, including band offsets at solid-liquid interfaces, and formation energies of charged vacancies in solids and at solid surfaces in vacuum. Finally, we use this method in conjunction with continuum solvation theories to investigate energetics of charged vacancies at solid-liquid interfaces. We find that for the example of an NaCl (001) surface in water, solvation reduces the formation energy of charged vacancies by 0.5 eV: calculation of this important effect was previously impractical due to the computational cost in molecular-dynamics methods.

  5. Electrostatic contributions in the increased compatibility of polymer blends.

    PubMed

    Linares, Elisângela M; Jannuzzi, Sergio A V; Galembeck, Fernando

    2011-12-20

    Successful blending of different polymers to make a structural or functional material requires overcoming limitations due to immiscibility and/or incompatibility that arise from large polymer-polymer interfacial tensions. In the case of latex blends, the combination of capillary adhesion during the blended dispersion drying stage with electrostatic adhesion in the final product is an effective strategy to avoid these limitations, which has been extended to a number of polymer blends and composites. This work shows that adhesion of polymer domains in blends made with natural rubber and synthetic latexes is enhanced by electrostatic adhesion that is in turn enhanced by ion migration, according to the results from scanning electric potential microscopy. The additional attractive force between domains improves blend stability and mechanical properties, broadening the possibilities and scope of latex blends, in consonance with the "green chemistry" paradigm. This novel approach based on electrostatic adhesion can be easily extended to multicomponent systems, including nonpolymers.

  6. Quantitative analysis of molecular surfaces: areas, volumes, electrostatic potentials and average local ionization energies.

    PubMed

    Bulat, Felipe A; Toro-Labbé, Alejandro; Brinck, Tore; Murray, Jane S; Politzer, Peter

    2010-11-01

    We describe a procedure for performing quantitative analyses of fields f(r) on molecular surfaces, including statistical quantities and locating and evaluating their local extrema. Our approach avoids the need for explicit mathematical representation of the surface and can be implemented easily in existing graphical software, as it is based on the very popular representation of a surface as collection of polygons. We discuss applications involving the volumes, surface areas and molecular surface electrostatic potentials, and local ionization energies of a group of 11 molecules.

  7. Ab initio molecular electrostatic potential of hexanuclear Cu, Ag, and Au clusters

    NASA Astrophysics Data System (ADS)

    Posada-Amarillas, Alvaro

    DFT calculations of electrostatic potential (ESP) are carried out under the PBE/SDD theory level. Planar initial structures are given as input to perform DFT optimization with the aim of obtaining ground state structures. ESP is thus calculated and results show the existence of both, nucleophilic and electrophilic sites. In each case, the latter are located over the cluster planes while the former are observed in cluster vertices. Binding energy is provided, as well as structural parameters of ground state structures. CONACyT-México is acknowledged for funding Project No. 180424.

  8. Bohm potential effect on the propagation of electrostatic surface wave in semi-bounded quantum plasmas

    NASA Astrophysics Data System (ADS)

    Lee, Myoung-Jae; Jung, Young-Dae

    2017-02-01

    High frequency electrostatic wave propagation in a dense and semi-bounded electron quantum plasma is investigated with consideration of the Bohm potential. The dispersion relation for the surface mode of quantum plasma is derived and numerically analyzed. We found that the quantum effect enhances the frequency of the wave especially in the high wave number regime. However, the frequency of surface wave is found to be always lower than that of the bulk wave for the same quantum wave number. The group velocity of the surface wave for various quantum wave number is also obtained.

  9. Intrinsic Electrostatic Potential in the BK Channel Pore: Role in Determining Single Channel Conductance and Block

    PubMed Central

    Carvacho, Ingrid; Gonzalez, Wendy; Torres, Yolima P.; Brauchi, Sebastian; Alvarez, Osvaldo; Gonzalez-Nilo, Fernando D.; Latorre, Ramon

    2008-01-01

    The internal vestibule of large-conductance Ca2+ voltage-activated K+ (BK) channels contains a ring of eight negative charges not present in K+ channels of lower conductance (Glu386 and Glu389 in hSlo) that modulates channel conductance through an electrostatic mechanism (Brelidze, T.I., X. Niu, and K.L. Magleby. 2003. Proc. Natl. Acad. Sci. USA. 100:9017–9022). In BK channels there are also two acidic amino acid residues in an extracellular loop (Asp326 and Glu329 in hSlo). To determine the electrostatic influence of these charges on channel conductance, we expressed wild-type BK channels and mutants E386N/E389N, D326N, E329Q, and D326N/E329Q channels on Xenopus laevis oocytes, and measured the expressed currents under patch clamp. Contribution of E329 to the conductance is negligible and single channel conductance of D326N/E329Q channels measured at 0 mV in symmetrical 110 mM K+ was 18% lower than the control. Current–voltage curves displayed weak outward rectification for D326N and the double mutant. The conductance differences between the mutants and wild-type BK were caused by an electrostatic effect since they were enhanced at low K+ (30 mM) and vanished at high K+ (1 M K+). We determine the electrostatic potential change, Δφ, caused by the charge neutralization using TEA+ block for the extracellular charges and Ba2+ for intracellular charges. We measured 13 ± 2 mV for Δφ at the TEA+ site when turning off the extracellular charges, and 17 ± 2 mV for the Δφ at the Ba2+ site when the intracellular charges were turned off. To understand the electrostatic effect of charge neutralizations, we determined Δφ using a BK channel molecular model embedded in a lipid bilayer and solving the Poisson-Boltzmann equation. The model explains the experimental results adequately and, in particular, gives an economical explanation to the differential effect on the conductance of the neutralization of charges D326 and E329. PMID:18227273

  10. Biobriefcase electrostatic aerosol collector

    DOEpatents

    Bell, Perry M.; Christian, Allen T.; Bailey, Christopher G.; Willis, Ladona; Masquelier, Donald A.; Nasarabadi, Shanavaz L.

    2009-03-17

    A system for sampling air and collecting particles entrained in the air comprising a receiving surface, a liquid input that directs liquid to the receiving surface and produces a liquid surface, an air input that directs the air so that the air with particles entrained in the air impact the liquid surface, and an electrostatic contact connected to the liquid that imparts an electric charge to the liquid. The particles potentially including bioagents become captured in the liquid by the air with particles entrained in the air impacting the liquid surface. Collection efficiency is improved by the electrostatic contact electrically charging the liquid. The effects of impaction and adhesion due to electrically charging the liquid allows a unique combination in a particle capture medium that has a low fluid consumption rate while maintaining high efficiency.

  11. Electrostatic forces for personnel restraints

    NASA Technical Reports Server (NTRS)

    Ashby, N.; Ciciora, J.; Gardner, R.; Porter, K.

    1977-01-01

    The feasibility of utilizing electrostatic forces for personnel retention devices on exterior spacecraft surfaces was analyzed. The investigation covered: (1) determination of the state of the art; (2) analysis of potential adhesion surfaces; (3) safety considerations for personnel; (4) electromagnetic force field determination and its effect on spacecraft instrumentation; and (5) proposed advances to current technology based on documentation review, analyses, and experimental test data.

  12. Modeling lipophilicity from the distribution of electrostatic potential on a molecular surface

    NASA Astrophysics Data System (ADS)

    Du, Qishi; Arteca, Gustavo A.

    1996-04-01

    Molecular lipophilicity L is represented as a function of four surface electrostatic potential descriptors: L=f(BF +,BF -,BR +,BR -). Each B descriptor is computed from the products of elements of molecular surface area, Δsi, and the molecular electrostatic potential (MEP), V( r i), at the center of an area element: B = ∑i Δi V(ri). Octanol-water partition coefficients (Pow) are correlated with these four surface-MEP descriptors: log Pow=c0+c1BF ++c2BF -+c3BR ++c4BR -. Good correlations are obtained for homologous series of aliphatic alcohols, amines and acids, as well as for a set of aromatic compounds with various functional groups. Within this approach, we find that the molecular fragment contributions of surface-MEP descriptors to log P are approximately additive. We have computed the values for the following fragments:-CH2-,-CH3,-COOH,-OH and-NH2. These contributions can be used to estimate the molecular lipophilicity and partition coefficients of new compounds, without additional quantum-mechanical calculations. The proposed approach provides a reasonably accurate tool that can be useful in quantitative structure-activity relations for computer-aided rational drug design. More importantly, the correlation model is conceptually simpler than previous work in the literature and can be improved systematically.

  13. Comparison of treecodes for computing electrostatic potentials in charged particle systems with disjoint targets and sources.

    PubMed

    Boateng, Henry A; Krasny, Robert

    2013-09-30

    In molecular simulations, it is sometimes necessary to compute the electrostatic potential at M target sites due to a disjoint set of N charged source particles. Direct summation requires O(MN) operations, which is prohibitively expensive when M and N are large. Here, we consider two alternative tree-based methods that reduce the cost. The standard particle-cluster treecode partitions the N sources into an octree and applies a far-field approximation, whereas a recently developed cluster-particle treecode instead partitions the M targets into an octree and applies a near-field approximation. We compare the two treecodes with direct summation and document their accuracy, CPU run time, and memory usage. We find that the particle-cluster treecode is faster when N > M, that is, when the sources outnumber the targets, and conversely, the cluster-particle treecode is faster when M > N, that is, when the targets outnumber the sources. Hence, the two treecodes provide useful tools for computing electrostatic potentials in charged particle systems with disjoint targets and sources.

  14. Theoretical studies of the mechanism of the action of the neurohypophyseal hormones. I. Molecular electrostatic potential (MEP) and molecular electrostatic field (MEF) maps of some vasopressin analogues

    NASA Astrophysics Data System (ADS)

    Liwo, Adam; Tempczyk, Anna; Grzonka, Zbigniew

    1989-09-01

    Continuing our theoretical studies of the oxytocin and vasopressin analogues, we have analysed the molecular electrostatic potential (MEP) and the norm of the molecular electrostatic field (MEF) of [1- β-mercaptopropionic acid]-arginine-vasopressin ([Mpa1]-AVP), [1-( β-mercapto- β,β-cyclopentamethylene)propionic acid]-arginine-vasopressin ([Cpp']-AVP), and [1-thiosalicylic acid]-arginine-vasopressin ([Ths']-AVP) whose low-energy conformations were calculated in our previous work. These compounds are known from experiment to exhibit different biological activity. The scalar fields mentioned determine the energy of interaction with either charged (MEP) or polar (MEF) species, the energy being in the second case either optimal or Boltzmann-averaged over all the possible orientations of the dipole moment versus the electrostatic field. The electrostatic interactions slowly vanish with distance and can therefore be considered to be the factor determining the molecular shape at greater distances, which can help in both predicting the interactions with the receptor at the stage of remote recognition and in finding the preferred directions of solvation by a polar solvent. In the analysis of the fields three techniques have been used: (i) the construction of maps in certain planes; (ii) the construction of maps on spheres centered in the charge center of the molecule under study and of poles chosen according to the main axes of the quadrupole moment; and (iii) the construction of surfaces corresponding to a given value of potential. The results obtained show that the shapes of both MEP and MEF are similar in the case of [Mpa1]-AVP and [Cpp1-AVP (biologically active), while some differences emerge when comparing these compounds with [Ths1]-AVP (inactive). It has also been found that both MEP and MEF depend even more strongly on conformation.

  15. Dirac gap-induced graphene quantum dot in an electrostatic potential

    NASA Astrophysics Data System (ADS)

    Giavaras, G.; Nori, Franco

    2011-04-01

    A spatially modulated Dirac gap in a graphene sheet leads to charge confinement, thus enabling a graphene quantum dot to be formed without the application of external electric and magnetic fields [G. Giavaras and F. Nori, Appl. Phys. Lett. 97, 243106 (2010)]. This can be achieved provided the Dirac gap has a local minimum in which the states become localized. In this work, the physics of such a gap-induced dot is investigated in the continuum limit by solving the Dirac equation. It is shown that gap-induced confined states couple to the states introduced by an electrostatic quantum well potential. Hence the region in which the resulting hybridized states are localized can be tuned with the potential strength, an effect which involves Klein tunneling. The proposed quantum dot may be used to probe quasirelativistic effects in graphene, while the induced confined states may be useful for graphene-based nanostructures.

  16. Design of [2]rotaxane through image threshold segmentation of electrostatic potential image.

    PubMed

    Liu, Pingying; Chen, Qiufeng; Ma, Jing

    2016-09-15

    An electrostatic potential (ESP)-based image segmentation method has been used to estimate the ability of proton donation and acceptance involved in ring-rod recognition. The relative binding strength of [2]rotaxane has also been further estimated from the difference of the characteristic image-segmentation derived ESP between proton donor and proton acceptor. The size and electrostatic compatibility criteria are introduced to guide the design of interlocked [2]rotaxane. A library of 75 thermodynamically stable [2]rotaxane candidates has been generated, including 16 experimentally known systems. The theoretical results for 16 experimentally known [2]rotaxanes are in good agreement with both the experimental association constants and density functional theory-calculated binding energies. Our ESP-based image segmentation model is also applicable to the tristable [2]rotaxane molecular shuttle as well as [1]rotaxane with self-inclusion function, indicating this simple method is generic in the field of constructing other supramolecular architectures formed with donor/acceptor molecular recognition. © 2016 Wiley Periodicals, Inc.

  17. Relation between molecular electrostatic potential, several electronic properties and antibacterial activity of some synthetic furane derivatives

    NASA Astrophysics Data System (ADS)

    Monasterios, Melina; Avendaño, Milagros; Amaro, María Isabel; Infante, Wilson; Charris, Jaime

    2006-10-01

    The present work reports the preliminary evaluation of the antibacterial activity, molecular electrostatic potential (MEP) determination and relevant electronic properties for their behavior as one electron acceptor, of a serial of compounds, active and inactive analogues, derived form furan, that were previously synthesized within our investigation group, with the purpose of establishing the existence of a valid correlation between their antibacterial activity and those electrostatic and electronic properties. According to the balance between the positive and negative areas in combination with the size of the MEP's area it was determined that these derivatives exhibit activity against Gram-positive and Gram-negative bacteria or only against Gram-positive ones. We found no valid correlation between the single point energy, the energy associated to the lowest unoccupied molecular orbital (LUMO); LUMO's density, nucleophilic susceptibility, Log P and the dipole moment, with the experimental activity determined for them. This could be because this is an homologous serial where the properties derived from the electronic distribution just change between those molecules that have a nitro group (active) in contrast with those wherein this group is absent (inactive).

  18. Visualization of the electrostatic potential distribution in both polar ionospheres using multiple satellite measurements

    NASA Technical Reports Server (NTRS)

    Hairston, Marc R.; Heelis, Roderick A.; Rich, Frederick J.

    1995-01-01

    During the time from December 1991 through March 1992, there were four operational DMSP satellites in polar orbit. All four satellites carried the Special Sensor-Ions, Electrons, Scintillation (SSIES) plasma package which included an ion drift meter. Data from the drift meter, combined with the magnetic field data, allowed the calculation of the electrostatic potential in the ionosphere along the satellite's path. Simultaneous polar coverage by four satellites was unprecedented, providing researchers with almost continuous monitoring of the potential distribution in both hemispheres for the four month period. Combining the magnitude and location of the potential data from each of the four satellites in order to examine the varying potential distribution pattern in both hemispheres presented a major challenge in data visualization. The problem was solved by developing a three-dimensional presentation of the data where the potentials are color coded and represented by the vertical dimension. This paper presents examples from a computer animation of several days of data demonstrating evolution of the size and shape of the potential distribution, along with how these changes correspond to variations in other geophysical parameters, such as the IMF orientation and the K(sub p) index.

  19. Analysis of the radial potential structure and neutron production rate in the spherical inertial electrostatic confinement fusion devices

    NASA Astrophysics Data System (ADS)

    Ramzanpour, M. A.; Pahlavani, M. R.

    2017-01-01

    The radial dependent potential and neutron production rate in spherical inertial electrostatic confinement fusion (IECF) devices is investigated. The electrostatic potential is determined by solving the Poisson equation for various deuteron and electron distribution functions. The fusion reaction rates are determined using energy distribution function. Also, dependence of potential structure and neutron production rate on some important parameters as the ion and electron convergence, working pressure, kinetic energy of the secondary electrons emitted from the cathode and the fraction of secondary electrons drawn inside the cathode are studied. Total produced neutrons as a function of input power at different working conditions are also obtained.

  20. Evaluation of an electrostatic dust removal system with potential application in next-step fusion devices

    SciTech Connect

    Friesen, F. Q. L.; John, B.; Skinner, C. H.; Roquemore, A. L.; Calle, C. I.

    2011-05-15

    The ability to manage inventories of carbon, tritium, and high-Z elements in fusion plasmas depends on means for effective dust removal. A dust conveyor, based on a moving electrostatic potential well, was tested with particles of tungsten, carbon, glass, and sand. A digital microscope imaged a representative portion of the conveyor, and dust particle size and volume distributions were derived before and after operation. About 10 mm{sup 3} volume of carbon and tungsten particles were moved in under 5 s. The highest driving amplitude tested of 3 kV was the most effective. The optimal driving frequency was 210 Hz (maximum tested) for tungsten particles, decreasing to below 60 Hz for the larger sand particles. Measurements of particle size and volume distributions after 10 and 100 cycles show the breaking apart of agglomerated carbon and the change in particle distribution over short timescales (<1 s).

  1. Patterning of plasmonic nanoparticles into multiplexed one-dimensional arrays based on spatially modulated electrostatic potential.

    PubMed

    Jiang, Lin; Sun, Yinghui; Nowak, Christoph; Kibrom, Asmorom; Zou, Changji; Ma, Jan; Fuchs, Harald; Li, Shuzhou; Chi, Lifeng; Chen, Xiaodong

    2011-10-25

    We report a new strategy to pattern plasmonic nanoparticles into multiplexed one-dimensional arrays based on the spatially modulated electrostatic potential. The 32 nm Au nanoparticles can be simultaneously deposited on one chip with tunable interparticle distance by solely adjusting the width of the grooves. Furthermore, 32 and 13 nm Au nanoparticles can be selectively deposited in grooves of different widths on one chip. As a result, the surface plasmon absorption bands on the chip can be tuned depending on the interparticle distance or the particle size of multiplex 1D arrays, which could enhance the Raman scattering cross section of the adsorbed molecules and result in multiplex surface-enhanced Raman scattering (SERS) response on the chip. This strategy provides a general method to fabricate 1D multiplex arrays with different particle sizes and interparticle distances on one chip.

  2. Evaluation of an Electrostatic Dust Removal System with Potential Application in Next-Step Fusion Devices

    SciTech Connect

    Friesen, F. Q.L.; John, B.; Skinner, C. H.; Roquemore, A. L.; Calle, C. I.

    2011-01-20

    The ability to manage inventories of carbon, tritium, and high-Z elements in fusion plasmas depends on means for effective dust removal. A dust conveyor, based on a moving electrostatic potential well, was tested with particles of tungsten, carbon, glass and sand. A digital microscope imaged a representative portion of the conveyor, and dust particle size and volume distributions were derived before and after operation. About 10 mm3 volume of carbon and tungsten particles were moved in under 5 seconds. The highest driving amplitude tested of 3 kV was the most effective. The optimal driving frequency was 210 Hz (maximum tested) for tungsten particles, decreasing to below 60 Hz for the larger sand particles. Measurements of particle size and volume distributions after 10 and 100 cycles show the breaking apart of agglomerated carbon, and the change in particle distribution over short timescales (<1 s).

  3. Evaluation of an Electrostatic Dust Removal System with Potential Application in Next-Step Fusion Devices

    SciTech Connect

    Friesen, F. Q.L.

    2011-01-01

    The ability to manage inventories of carbon, tritium, and high-Z elements in fusion plasmas depends on means for effective dust removal. A dust conveyor, based on a moving electrostatic potential well, was tested with particles of tungsten, carbon, glass and sand. A digital microscope imaged a representative portion of the conveyor, and dust particle size and volume distributions were derived before and after operation. About 10 mm3 volume of carbon and tungsten particles were moved in under 5 seconds. The highest driving amplitude tested of 3 kV was the most effective. The optimal driving frequency was 210 Hz (maximum tested) for tungsten particles, decreasing to below 60 Hz for the larger sand particles. Measurements of particle size and volume distributions after 10 and 100 cycles show the breaking apart of agglomerated carbon, and the change in particle distribution over short timescales (<1 s).

  4. Evaluation of an Electrostatic Dust Removal System with Potential Application in Next-Step Fusion Devices

    NASA Technical Reports Server (NTRS)

    Friesen, F. Q. L.; John, B.; Skinner, C. H.; Roquemore, A. L.; Calle, C. I.

    2011-01-01

    The ability to manage inventories of carbon, tritium, and high-Z elements in fusion plasmas depends on means for effective dust removal. A dust conveyor, based on a moving electrostatic potential well, was tested with particles of tungsten, carbon, glass and sand. A digital microscope imaged a representative portion of the conveyor, and dust particle size and volume distributions were derived before and after operation. About 10 cu mm volume of carbon and tungsten particles were moved in under 5 seconds. The highest driving amplitude tested of 3 kV was the most effective. The optimal driving frequency was 210 Hz (maximum tested) for tungsten particles, decreasing to below 60 Hz for the larger sand particles. Measurements of particle size and volume distributions after 10 and 100 cycles show the breaking apart of agglomerated carbon, and the change in particle distribution over short timescales 1 s).

  5. Empirical and accurate method for the three-dimensional electrostatic potential (EM-ESP) of biomolecules.

    PubMed

    Du, Qi-Shi; Wang, Cheng-Hua; Wang, Yu-Ting; Huang, Ri-Bo

    2010-04-01

    The electrostatic potential (ESP) is an important property of interactions within and between macromolecules, including those of importance in the life sciences. Semiempirical quantum chemical methods and classical Coulomb calculations fail to provide even qualitative ESP for many of these biomolecules. A new empirical ESP calculation method, namely, EM-ESP, is developed in this study, in which the traditional approach of point atomic charges and the classical Coulomb equation is discarded. In its place, the EM-ESP generates a three-dimensional electrostatic potential V(EM)(r) in molecular space that is the sum of contributions from all component atoms. The contribution of an atom k is formulated as a Gaussian function g(r(k);alpha(k),beta(k)) = alpha(k)/r(k)(betak) with two parameters (alpha(k) and beta(k)). The benchmark for the parameter optimization is the ESP obtained by using higher-level quantum chemical approaches (e.g., CCSD/TZVP). A set of atom-based parameters is optimized in a training set of common organic molecules. Calculated examples demonstrate that the EM-ESP approach is a vast improvement over the Coulombic approach in producing the molecular ESP contours that are comparable to the results obtained with higher-level quantum chemical methods. The atom-based parameters are shown to be transferrable between one part of closely related aromatic molecules. The atom-based ESP formulization and parametrization strategy can be extended to biological macromolecules, such as proteins, DNA, and RNA molecules. Since ESP is frequently used to rationalize and predict intermolecular interactions, we expect that the EM-ESP method will have important applications for studies of protein-ligand and protein-protein interactions in numerous areas of chemistry, molecular biology, and other life sciences.

  6. Physical model of granule adhesion to the belt-electrodes of a tribo-aero-electrostatic separator

    NASA Astrophysics Data System (ADS)

    Li, Jia; Dascalescu, Lucian; Miloudi, Mohamed; Bilici, Mihai; Xu, Zhenming

    2013-03-01

    Recent studies have demonstrated the effectiveness of tribo-aero-electrostatic separation technologies, which consist in the selective sorting of mixed granular insulating materials in a fluidized bed affected by an electric field orthogonally oriented to the direction of the fluidization air. The aim of the present paper is to put the theoretical bases for the optimization of this process, i. e. maximize the total mass of the granules collected at the two electrodes that generate the electric field. The various forces that drive a granule of given mass and electric charge through the electric field and make it stick to an electrode are expressed as functions of the several input variables and parameters of the process, such as the applied high-voltage or the surface roughness, the size and the position of the electrodes. The concepts of "critical electrostatic field" and "virtual climbing distance" are introduced. The prediction of the theoretical model are confirmed by the results of three sets of experiments, carried out on samples of a granular mixture consisting of 50% Acrylonitrile Butadiene Styrene (ABS) and 50% High Impact Polystyrene (HIPS), originating from the recycling of waste electric and electronic equipment. Higher separation efficiency was obtained when the electric field in the active zone was intensified by the use of an additional electrode connected to the ground and when the collecting electrodes were covered by a thin insulating layer.

  7. Potential electrostatic interactions in multiple regions affect human metapneumovirus F-mediated membrane fusion.

    PubMed

    Chang, Andres; Hackett, Brent A; Winter, Christine C; Buchholz, Ursula J; Dutch, Rebecca Ellis

    2012-09-01

    The recently identified human metapneumovirus (HMPV) is a worldwide respiratory virus affecting all age groups and causing pneumonia and bronchiolitis in severe cases. Despite its clinical significance, no specific antiviral agents have been approved for treatment of HMPV infection. Unlike the case for most paramyxoviruses, the fusion proteins (F) of a number of strains, including the clinical isolate CAN97-83, can be triggered by low pH. We recently reported that residue H435 in the HRB linker domain acts as a pH sensor for HMPV CAN97-83 F, likely through electrostatic repulsion forces between a protonated H435 and its surrounding basic residues, K295, R396, and K438, at low pH. Through site-directed mutagenesis, we demonstrated that a positive charge at position 435 is required but not sufficient for F-mediated membrane fusion. Arginine or lysine substitution at position 435 resulted in a hyperfusogenic F protein, while replacement with aspartate or glutamate abolished fusion activity. Studies with recombinant viruses carrying mutations in this region confirmed its importance. Furthermore, a second region within the F(2) domain identified as being rich in charged residues was found to modulate fusion activity of HMPV F. Loss of charge at residues E51, D54, and E56 altered local folding and overall stability of the F protein, with dramatic consequences for fusion activity. As a whole, these studies implicate charged residues and potential electrostatic interactions in function, pH sensing, and overall stability of HMPV F.

  8. Imaging alpha-hemolysin with molecular dynamics: ionic conductance, osmotic permeability, and the electrostatic potential map.

    PubMed

    Aksimentiev, Aleksij; Schulten, Klaus

    2005-06-01

    alpha-Hemolysin of Staphylococcus aureus is a self-assembling toxin that forms a water-filled transmembrane channel upon oligomerization in a lipid membrane. Apart from being one of the best-studied toxins of bacterial origin, alpha-hemolysin is the principal component in several biotechnological applications, including systems for controlled delivery of small solutes across lipid membranes, stochastic sensors for small solutes, and an alternative to conventional technology for DNA sequencing. Through large-scale molecular dynamics simulations, we studied the permeability of the alpha-hemolysin/lipid bilayer complex for water and ions. The studied system, composed of approximately 300,000 atoms, included one copy of the protein, a patch of a DPPC lipid bilayer, and a 1 M water solution of KCl. Monitoring the fluctuations of the pore structure revealed an asymmetric, on average, cross section of the alpha-hemolysin stem. Applying external electrostatic fields produced a transmembrane ionic current; repeating simulations at several voltage biases yielded a current/voltage curve of alpha-hemolysin and a set of electrostatic potential maps. The selectivity of alpha-hemolysin to Cl(-) was found to depend on the direction and the magnitude of the applied voltage bias. The results of our simulations are in excellent quantitative agreement with available experimental data. Analyzing trajectories of all water molecule, we computed the alpha-hemolysin's osmotic permeability for water as well as its electroosmotic effect, and characterized the permeability of its seven side channels. The side channels were found to connect seven His-144 residues surrounding the stem of the protein to the bulk solution; the protonation of these residues was observed to affect the ion conductance, suggesting the seven His-144 to comprise the pH sensor that gates conductance of the alpha-hemolysin channel.

  9. Properties of liquid water from a systematic refinement of a high-rank multipolar electrostatic potential.

    PubMed

    Shaik, Majeed S; Liem, Steven Y; Popelier, Paul L A

    2010-05-07

    We build on previous work [S. Y. Liem and P. L. A. Popelier, J. Chem. Theory Comput. 4, 353 (2008)], where for the first time, a high-rank multipolar electrostatic potential was used in molecular dynamics simulations of liquid water at a wide range of pressures and temperatures, and using a multipolar Ewald summation. Water is represented as a rigid body, with atomic multipole moments defined by quantum chemical topology partitioning its gas phase electron density. The effect of the level of theory on the local structure of liquid water is systematically addressed. Values for Lennard-Jones (LJ) parameters are optimized, for both oxygen and hydrogen atoms, against bulk properties. The best LJ parameters were then used in a set of simulations at 30 different temperatures (1 atm) and another set at 11 different pressures (at 298 K). Inclusion of the hydrogen LJ parameters significantly increases the self-diffusion coefficient. The behavior of bulk properties was studied and the local water structure analyzed by both radial and spatial distribution functions. Comparisons with familiar point-charge potentials, such as TIP3P, TIP4P, TIP5P, and simple point charge, show the benefits of multipole moments.

  10. Role of electrostatic potential in the in silico prediction of molecular bioactivation and mutagenesis.

    PubMed

    Ford, Kevin A

    2013-04-01

    Electrostatic potential (ESP) is a useful physicochemical property of a molecule that provides insights into inter- and intramolecular associations, as well as prediction of likely sites of electrophilic and nucleophilic metabolic attack. Knowledge of sites of metabolic attack is of paramount importance in DMPK research since drugs frequently fail in clinical trials due to the formation of bioactivated metabolites which are often difficult to measure experimentally due to their reactive nature and relatively short half-lives. Computational chemistry methods have proven invaluable in recent years as a means to predict and study bioactivated metabolites without the need for chemical syntheses, or testing on experimental animals. Additional molecular properties (heat of formation, heat of solvation and E(LUMO) - E(HOMO)) are discussed in this paper as complementary indicators of the behavior of metabolites in vivo. Five diverse examples are presented (acetaminophen, aniline/phenylamines, imidacloprid, nefazodone and vinyl chloride) which illustrate the utility of this multidimensional approach in predicting bioactivation, and in each case the predicted data agreed with experimental data described in the scientific literature. A further example of the usefulness of calculating ESP, in combination with the molecular properties mentioned above, is provided by an examination of the use of these parameters in providing an explanation for the sites of nucleophilic attack of the nucleic acid cytosine. Exploration of sites of nucleophilic attack of nucleic acids is important as adducts of DNA have the potential to result in mutagenesis.

  11. Identifying Student Use of Ball-and-Stick Images versus Electrostatic Potential Map Images via Eye Tracking

    ERIC Educational Resources Information Center

    Williamson, Vickie M.; Hegarty, Mary; Deslongchamps, Ghislain; Williamson, Kenneth C., III

    2013-01-01

    This pilot study examined students' use of ball-and-stick images versus electrostatic potential maps when asked questions about electron density, positive charge, proton attack, and hydroxide attack with six different molecules (two alcohols, two carboxylic acids, and two hydroxycarboxylic acids). Students' viewing of these dual images…

  12. Electrostatic Toys.

    ERIC Educational Resources Information Center

    Greenslade, Thomas B., Jr.

    1982-01-01

    Describes typical electrostatic toys which may be used to show students phenomena associated with sparks, sudden drops in potential, induction, and forces between bodies of like and opposite charges. Many of these demonstrations are suitable for student projects. (Author/JN)

  13. Adhesion of Escherichia coli under flow conditions reveals potential novel effects of FimH mutations.

    PubMed

    Feenstra, T; Thøgersen, M S; Wieser, E; Peschel, A; Ball, M J; Brandes, R; Satchell, S C; Stockner, T; Aarestrup, F M; Rees, A J; Kain, R

    2017-03-01

    FimH-mediated adhesion of Escherichia coli to bladder epithelium is a prerequisite for urinary tract infections. FimH is also essential for blood-borne bacterial dissemination, but the mechanisms are poorly understood. The purpose of this study was to assess the influence of different FimH mutations on bacterial adhesion using a novel adhesion assay, which models the physiological flow conditions bacteria are exposed to. We introduced 12 different point mutations in the mannose binding pocket of FimH in an E. coli strain expressing type 1 fimbriae only (MSC95-FimH). We compared the bacterial adhesion of each mutant across several commonly used adhesion assays, including agglutination of yeast, adhesion to mono- and tri-mannosylated substrates, and static adhesion to bladder epithelial and endothelial cells. We performed a comparison of these assays to a novel method that we developed to study bacterial adhesion to mammalian cells under flow conditions. We showed that E. coli MSC95-FimH adheres more efficiently to microvascular endothelium than to bladder epithelium, and that only endothelium supports adhesion at physiological shear stress. The results confirmed that mannose binding pocket mutations abrogated adhesion. We demonstrated that FimH residues E50 and T53 are crucial for adhesion under flow conditions. The coating of endothelial cells on biochips and modelling of physiological flow conditions enabled us to identify FimH residues crucial for adhesion. These results provide novel insights into screening methods to determine the effect of FimH mutants and potentially FimH antagonists.

  14. Different electrostatic potentials define ETGE and DLG motifs as hinge and latch in oxidative stress response.

    PubMed

    Tong, Kit I; Padmanabhan, Balasundaram; Kobayashi, Akira; Shang, Chengwei; Hirotsu, Yosuke; Yokoyama, Shigeyuki; Yamamoto, Masayuki

    2007-11-01

    Nrf2 is the regulator of the oxidative/electrophilic stress response. Its turnover is maintained by Keap1-mediated proteasomal degradation via a two-site substrate recognition mechanism in which two Nrf2-Keap1 binding sites form a hinge and latch. The E3 ligase adaptor Keap1 recognizes Nrf2 through its conserved ETGE and DLG motifs. In this study, we examined how the ETGE and DLG motifs bind to Keap1 in a very similar fashion but with different binding affinities by comparing the crystal complex of a Keap1-DC domain-DLG peptide with that of a Keap1-DC domain-ETGE peptide. We found that these two motifs interact with the same basic surface of either Keap1-DC domain of the Keap1 homodimer. The DLG motif works to correctly position the lysines within the Nrf2 Neh2 domain for efficient ubiquitination. Together with the results from calorimetric and functional studies, we conclude that different electrostatic potentials primarily define the ETGE and DLG motifs as a hinge and latch that senses the oxidative/electrophilic stress.

  15. Estimation of Molecular Acidity via Electrostatic Potential at the Nucleus and Valence Natural Atomic Orbitals

    PubMed Central

    Liu, Shubin; Pedersen, Lee G.

    2009-01-01

    An effective approach of estimating molecular pKa values from simple density functional calculations is proposed in this work. Both the molecular electrostatic potential (MEP) at the nucleus of the acidic atom and the sum of valence natural atomic orbitals are employed for three categories of compounds, amines and anilines, carbonyl acids and alcohols, and sulfonic acids and thiols. A strong correlation between experimental pKa values and each of these two quantities for each of the three categories has been discovered. Moreover, if the MEP is subtracted by the isolated atomic MEP for each category of compounds, we observe a single unique linear relationship between the resultant MEP difference and experimental pKa data of amines, anilines, carbonyl acids, alcohols, sulfonic acids, thiols, and their substituents. These results can generally be utilized to simultaneously estimate pKa values at multiple sites with a single calculation for either relatively small molecules in drug design or amino acids in proteins and macromolecules. PMID:19317439

  16. Segmental analysis of molecular surface electrostatic potentials: application to enzyme inhibition.

    PubMed

    Brinck, Tore; Jin, Ping; Ma, Yuguang; Murray, Jane S; Politzer, Peter

    2003-04-01

    We have recently shown that the anti-HIV activities of reverse transcriptase inhibitors can be related quantitatively to properties of the electrostatic potentials on their molecular surfaces. We now introduce the technique of using only segments of the drug molecules in developing such expressions. If an improved correlation is obtained for a given family of compounds, it would suggest that the segment being used plays a key role in the interaction. We demonstrate the procedure for three groups of drugs, two acting on reverse transcriptase and one on HIV protease. Segmental analysis is found to be definitely beneficial in one case, less markedly so in another, and to have a negative effect in the third. The last result indicates that major portions of the molecular surfaces are involved in the interactions and that the entire molecules need to be considered, in contrast to the first two examples, in which certain segments appear to be of primary importance. This initial exploratory study shows that segmental analysis can provide insight into the nature of the process being investigated, as well as possibly enhancing the predictive capability.

  17. Topological analysis of aromatic halogen/hydrogen bonds by electron charge density and electrostatic potentials.

    PubMed

    Duarte, Darío J R; de las Vallejos, Margarita M; Peruchena, Nélida M

    2010-04-01

    In this work, the intermolecular distribution of the electronic charge density in the aromatic hydrogen/halogen bonds is studied within the framework of the atoms in molecules (AIM) theory and the molecular electrostatic potentials (MEP) analysis. The study is carried out in nine complexes formed between benzene and simple lineal molecules, where hydrogen, fluorine and chlorine atoms act as bridge atoms. All the results are obtained at MP2 level theory using cc-pVTZ basis set. Attention is focused on topological features observed at the intermolecular region such as bond, ring and cage critical points of the electron density, as well as the bond path, the gradient of the density maps, molecular graphs and interatomic surfaces. The strength of the interaction increases in the following order: F[Symbol: see text]pi < Cl[Symbol: see text]pi < H[Symbol: see text]pi. Our results show that the fluorine atom has the capability to interact with the pi-cloud to form an aromatic halogen bond, as long as the donor group is highly electron withdrawing. The Laplacian topology allows us to state that the halogen atoms can act as nucleophiles as well as electrophiles, showing clearly their dual character.

  18. Chemical reactivity trends of ergotamine and butenolide from electrostatic potentials and charge sensitivities

    SciTech Connect

    Mrozek, J.; Michalak, A.

    1995-12-05

    A set of reactivity indices, including maps of the electrostatic potential and local and condensed Fukui function (FF) indices in the atomic resolution, are reported for two vasoconstricting mycotoxins: butenolide and ergotamine; both the finite difference approach of Parr and Yan as well as charge sensitivity analysis, determining the charge responses via the inversion of the hardness tensor, have been used to generate the FF data. These two routes of arriving at the atomic FF indices provide an opportunity to evaluate the available parametrizations of the semiempirical NDDO-type of methods which have been used to determine the input charge distribution; namely, the best parametrization should generate consistent FF predictions resulting from both approaches. For butenolide, the MNDO parametrization was found to fulfill this consistency requirement. The chemical reactivity information has been used to trace possible similarities in reactivity trends of the butenolide molecule and the related fragment of ergotamine, toward hypothetical nucleophilic, electrophilic, and radical attacks. These predictions have been compared to experimental data available for other unsaturated lactones. 13 refs., 18 figs., 1 tab.

  19. Designing metal hydride complexes for water splitting reactions: a molecular electrostatic potential approach.

    PubMed

    Sandhya, K S; Suresh, Cherumuttathu H

    2014-08-28

    The hydridic character of octahedral metal hydride complexes of groups VI, VII and VIII has been systematically studied using molecular electrostatic potential (MESP) topography. The absolute minimum of MESP at the hydride ligand (Vmin) and the MESP value at the hydride nucleus (VH) are found to be very good measures of the hydridic character of the hydride ligand. The increasing/decreasing electron donating feature of the ligand environment is clearly reflected in the increasing/decreasing negative character of Vmin and VH. The formation of an outer sphere metal hydride-water complex showing the HH dihydrogen interaction is supported by the location and the value of Vmin near the hydride ligand. A higher negative MESP suggested lower activation energy for H2 elimination. Thus, MESP features provided a way to fine-tune the ligand environment of a metal-hydride complex to achieve high hydridicity for the hydride ligand. The applicability of an MESP based hydridic descriptor in designing water splitting reactions is tested for group VI metal hydride model complexes of tungsten.

  20. Electronic coupling calculations with transition charges, dipoles, and quadrupoles derived from electrostatic potential fitting

    SciTech Connect

    Fujimoto, Kazuhiro J.

    2014-12-07

    A transition charge, dipole, and quadrupole from electrostatic potential (TrESP-CDQ) method for electronic coupling calculations is proposed. The TrESP method is based on the classical description of electronic Coulomb interaction between transition densities for individual molecules. In the original TrESP method, only the transition charge interactions were considered as the electronic coupling. In the present study, the TrESP method is extended to include the contributions from the transition dipoles and quadrupoles as well as the transition charges. Hence, the self-consistent transition density is employed in the ESP fitting procedure. To check the accuracy of the present approach, several test calculations are performed to a helium dimer, a methane dimer, and an ethylene dimer. As a result, the TrESP-CDQ method gives a much improved description of the electronic coupling, compared with the original TrESP method. The calculated results also show that the self-consistent treatment to the transition densities contributes significantly to the accuracy of the electronic coupling calculations. Based on the successful description of the electronic coupling, the contributions to the electronic coupling are also analyzed. This analysis clearly shows a negligible contribution of the transition charge interaction to the electronic coupling. Hence, the distribution of the transition density is found to strongly influence the magnitudes of the transition charges, dipoles, and quadrupoles. The present approach is useful for analyzing and understanding the mechanism of excitation-energy transfer.

  1. Double layer adhesive silicone dressing as a potential dermal drug delivery film in scar treatment.

    PubMed

    Mojsiewicz-Pieńkowska, Krystyna; Jamrógiewicz, Marzena; Żebrowska, Maria; Mikolaszek, Barbara; Sznitowska, Małgorzata

    2015-03-15

    The present studies focused on the evaluation of design of an adhesive silicone film intended for scar treatment. Developed silicone double layer film was examined in terms of its future relevance to therapy and applicability on the human skin considering properties which included in vitro permeability of water vapor and oxygen. In order to adapt the patches for medical use in the future there were tested such properties as in vitro adhesion and occlusion related to in vivo hydration. From the silicone rubbers double layer silicone film was prepared: a non-adhesive elastomer as a drug carrier (the matrix for active substances - enoxaparin sodium - low molecular weight heparin) and an adhesive elastomer, applied on the surface of the matrix. The novel adhesive silicone film was found to possess optimal properties in comparison to commercially available silicone dressing: adhesion in vivo, adhesion in vitro - 11.79N, occlusion F=85% and water vapor permeability in vitro - WVP=105g/m(2)/24h, hydration of stratum corneum in vivoH=61-89 (RSD=1.6-0.9%), oxygen permeation in vitro - 119-391 cm(3)/m(2)/24 (RSD=0.17%). In vitro release studies indicated sufficient LMWH release rate from silicone matrix. Developed novel adhesive silicone films were considered an effective treatment of scars and keloids and a potential drug carrier able to improve the effectiveness of therapy.

  2. Electrostatic potential within the free volume space of imidazole-based solvents: insights into gas absorption selectivity.

    PubMed

    Liu, Haining; Zhang, Zhongtao; Bara, Jason E; Turner, C Heath

    2014-01-09

    In this work, a variety of molecular simulation tools are used to help characterize the selective absorption of CO2 and CH4 in imidazole-based solvents. We focus our efforts on a series of 1-n-alkyl-2-methyl-imidazoles and ether-functionalized imidazoles, over a temperature range from 293 to 353 K, and we perform detailed analysis of the free volume. We find that the electrostatic potential within the solvent free volume cavities provides a useful indication of the selective absorption of CO2 and CH4. The electrostatic potential calculation is significantly faster than the direct calculation of the chemical potential, and tests with the 1-n-alkyl-2-methyl-imidazoles and the ether-functionalized imidazoles indicate that this may be a useful screening tool for other solvents.

  3. Electrostatic potential of mean force between two curved surfaces in the presence of counterion connectivity

    NASA Astrophysics Data System (ADS)

    Zhou, Shiqi

    2015-11-01

    In this paper, we investigate effects of counterion connectivity (i.e., association of the counterions into a chain molecule) on the electrostatic potential of mean force (EPMF) between two similarly charged cylinder rods in a primitive model electrolyte solution by solving a classical density functional theory. The main findings include the following: (i) The counterion connectivity helps in inducing a like-charge-attractionlike (LCA-like) phenomenology even in a monovalent counterion solution wherein the LCA-like observation generally does not occur without the counterion connectivity. (ii) For divalent counterion solutions, the counterion connectivity can reinforce or weaken the LCA-like observation depending on the chain length N , and simply increases the equilibrium nearest surface separation of the rods corresponding to the minimum EPMF to nearly three times the counterion site diameter, whether N is large or small. (iii) If N is large enough, the LCA-like strength tends to be negatively correlated with the electrolyte concentration c over the entire range of the rod surface charge magnitude | σ*| considered; whereas if N drops, the correlation tends to become positive with decrease of the | σ*| value, and particularly for modest | σ*| values, the correlation relationship exhibits an extreme value phenomenon. (iv) In the case of a 1:1 electrolyte, the EPMF effects of the diameters of counterion and coion sites are similar in both situations with and without the counterion connectivity. All of these findings can be explained self-consistently by a recently proposed hydrogen-bonding style mechanism reinforced by one additional concept: flexibility of the counterion chain and the factors affecting it, like N and counterion site valence.

  4. Partial Charges in Periodic Systems: Improving Electrostatic Potential (ESP) Fitting via Total Dipole Fluctuations and Multiframe Approaches.

    PubMed

    Gabrieli, Andrea; Sant, Marco; Demontis, Pierfranco; Suffritti, Giuseppe B

    2015-08-11

    Two major improvements to the state-of-the-art Repeating Electrostatic Potential Extracted Atomic (REPEAT) method, for generating accurate partial charges for molecular simulations of periodic structures, are here developed. The first, D-REPEAT, consists in the simultaneous fit of the electrostatic potential (ESP), together with the total dipole fluctuations (TDF) of the framework. The second, M-REPEAT, allows the fit of multiple ESP configurations at once. When both techniques are fused into one, DM-REPEAT method, the resulting charges become remarkably stable over a large set of fitting regions, giving a robust and physically sound solution to the buried atoms problem. The method capabilities are extensively studied in ZIF-8 framework, and subsequently applied to IRMOF-1 and ITQ-29 crystal structures. To our knowledge, this is the first time that this approach is proposed in the context of periodic systems.

  5. Optimization of cutting schemes for the evaluation of molecular electrostatic potentials in proteins via Moving-Domain QM/MM.

    PubMed

    Menikarachchi, Lochana C; Gascón, José A

    2008-06-01

    This work presents new developments of the moving-domain QM/MM (MoD-QM/MM) method for modeling protein electrostatic potentials. The underlying goal of the method is to map the electronic density of a specific protein configuration into a point-charge distribution. Important modifications of the general strategy of the MoD-QM/MM method involve new partitioning and fitting schemes and the incorporation of dynamic effects via a single-step free energy perturbation approach (FEP). Selection of moderately sized QM domains partitioned between C (alpha) and C (from C=O), with incorporation of delocalization of electrons over neighboring domains, results in a marked improvement of the calculated molecular electrostatic potential (MEP). More importantly, we show that the evaluation of the electrostatic potential can be carried out on a dynamic framework by evaluating the free energy difference between a non-polarized MEP and a polarized MEP. A simplified form of the potassium ion channel protein Gramicidin-A from Bacillus brevis is used as the model system for the calculation of MEP.

  6. Study of electrostatic potential surface distribution of wild-type plastocyanin Synechocystis solution structure determined by homonuclear NMR.

    PubMed

    Monleón, Daniel; Celda, Bernardo

    2003-10-01

    Plastocyanin is a small (approximately 10 kDa), type I blue copper protein that works as an electron donor to photosystem I from cytochrome f in both chloroplast systems and in some strains of cyanobacteria. Comparative studies of the kinetic mechanisms of plastocyanins in different organisms show that the electron transfer from photosystem I happens by simple collision in cyanobacteria but through a intermediate transition complex in green algae and superior plants. Previous work has proved that this effect cannot be explained by structural variations across the different plastocyanins but it can be explained by differences in the electrostatic potential distribution at the protein surface. In that case, minor conformational errors at the amino acid side chain level may imply an important effect in the electrostatic potential distribution calculation. In this work we present a high resolution study of side chain conformation by homonuclear NMR for the reduced wild-type plastocyanin Synechocystis using intensity ratios for 2D-NOESY and 2D-H,H-TOCSY cross peaks at different mixing times. We also present the corresponding comparison with different plastocyanin structures and the effect in the electrostatic potential distribution at the protein surface. We discuss the importance of indirect J-coupling information from TOCSY-type experiments as complement for intraresidue distances derived from NOESY experiments in the determination of side chain orientation and stereo-specific assignments.

  7. Role of surface layer collagen binding protein from indigenous Lactobacillus plantarum 91 in adhesion and its anti-adhesion potential against gut pathogen.

    PubMed

    Yadav, Ashok Kumar; Tyagi, Ashish; Kaushik, Jai Kumar; Saklani, Asha Chandola; Grover, Sunita; Batish, Virender Kumar

    2013-12-14

    Human feacal isolates were ascertain as genus Lactobacillus using specific primer LbLMA1/R16-1 and further identified as Lactobacillus plantarum with species specific primers Lpl-3/Lpl-2. 25 L. plantarum strains were further assessed for hydrophobicity following the microbial adhesion to hydrocarbons (MATH) method and colonization potentials based on their adherence to immobilized human collagen type-1. Surface proteins were isolated from selected L. plantarum 91(Lp91) strain. The purified collagen binding protein (Cbp) protein was assessed for its anti-adhesion activity against enteric Escherichia coli 0157:H7 pathogen on immobilized collagen. Four L. plantarum strains displayed high degree of hydrophobicity and significant adhesion to collagen. A 72 kDa protein was purified which reduced 59.71% adhesion of E. coli 0157:H7 on immobilized collagen as compared to control well during adhesion assay. Cbp protein is the major influencing factor in inhibition of E. coli 0157:H7 adhesion with extracellular matrix (ECM) components. Hydrophobicity and adhesion potential are closely linked attributes precipitating in better colonization potential of the lactobacillus strains. Cbp is substantiated as a crucial surface protein contributing in adhesion of lactobacillus strains. The study can very well be the platform for commercialization of indigenous probiotic strain once their functional attributes are clinically explored.

  8. Electrostatic Charge on Flying Hummingbirds and Its Potential Role in Pollination

    PubMed Central

    von Rabenau, Lisa; Smiley, Ashley; Dudley, Robert

    2015-01-01

    Electrostatic phenomena are known to enhance both wind- and insect-mediated pollination, but have not yet been described for nectar-feeding vertebrates. Here we demonstrate that wild Anna's Hummingbirds (Calypte anna) can carry positive charges up to 800 pC while in flight (mean ± s.d.: 66 ± 129 pC). Triboelectric charging obtained by rubbing an isolated hummingbird wing against various plant structures generated charges up to 700 pC. A metal hummingbird model charged to 400 pC induced bending of floral stamens in four plants (Nicotiana, Hemerocallis, Penstemon, and Aloe spp.), and also attracted falling Lycopodium spores at distances of < 2 mm. Electrostatic forces may therefore influence pollen transfer onto nectar-feeding birds. PMID:26421845

  9. Electron holographic tomography for mapping the three-dimensional distribution of electrostatic potential in III-V semiconductor nanowires

    NASA Astrophysics Data System (ADS)

    Wolf, D.; Lichte, H.; Pozzi, G.; Prete, P.; Lovergine, N.

    2011-06-01

    Electron holographic tomography (EHT), the combination of off-axis electron holography with electron tomography, is a technique, which can be applied to the quantitative 3-dimensional (3D) mapping of electrostatic potential at the nanoscale. Here, we show the results obtained in the EHT investigation of GaAs and GaAs-AlGaAs core-shell nanowires grown by Au-catalysed metalorganic vapor phase epitaxy. The unique ability of EHT of disentangling the materials mean inner potential (MIP) from the specimen projected thickness allows reconstruction of the nanowire 3D morphology and inner compositional structure as well as the measurement of the MIP.

  10. Electron holographic tomography for mapping the three-dimensional distribution of electrostatic potential in III-V semiconductor nanowires

    SciTech Connect

    Wolf, D.; Lichte, H.; Pozzi, G.; Lovergine, N.

    2011-06-27

    Electron holographic tomography (EHT), the combination of off-axis electron holography with electron tomography, is a technique, which can be applied to the quantitative 3-dimensional (3D) mapping of electrostatic potential at the nanoscale. Here, we show the results obtained in the EHT investigation of GaAs and GaAs-AlGaAs core-shell nanowires grown by Au-catalysed metalorganic vapor phase epitaxy. The unique ability of EHT of disentangling the materials mean inner potential (MIP) from the specimen projected thickness allows reconstruction of the nanowire 3D morphology and inner compositional structure as well as the measurement of the MIP.

  11. Effect of surface potential on epithelial cell adhesion, proliferation and morphology.

    PubMed

    Chang, Hsun-Yun; Kao, Wei-Lun; You, Yun-Wen; Chu, Yi-Hsuan; Chu, Kuo-Jui; Chen, Peng-Jen; Wu, Chen-Yi; Lee, Yu-Hsuan; Shyue, Jing-Jong

    2016-05-01

    Cell adhesion is the basis of individual cell survival, division and motility. Hence, understanding the effects that the surface properties have on cell adhesion, proliferation and morphology are crucial. In particular, surface charge/potential has been identified as an important factor that affects cell behavior. However, how cells respond to incremental changes in surface potential remains unclear. By using binary self-assembled monolayer (SAM) modified Au surfaces that are similar in mechanical/chemical properties and provide a series of surface potentials, the effect of surface potential on the behavior of cells can be studied. In this work, the effect of surface potential on epithelial cells, including human embryonic kidney (HEK293T) and human hepatocellular carcinoma (HepG2), were examined. The results showed that the adhesion density of epithelial cells increased with increasing surface potential, which is similar to but varied more significantly compared with fibroblasts. The proliferation rate is found to be independent of surface potential in both cell types. Furthermore, epithelial cells show no morphological change with respect to surface potential, whereas the morphology of the fibroblasts clearly changed with the surface potential. These differences between the cell types were rationalized by considering the difference in extracellular matrix composition. Laminin-dominant epithelial cells showed higher adhesion density and less morphological change than did fibronectin-dominant fibroblasts because the more significant adsorption of positively charged laminin on the surface enhanced the adhesion of epithelial cells. In contrast, due to the dominance of negatively charged fibronectin that adsorbed weakly on the surface, fibroblasts had to change their morphology to fit the inhomogeneous fibronectin-adsorbed area.

  12. Origins of electrostatic potential wells at dislocations in polycrystalline Cu(In,Ga)Se{sub 2} thin films

    SciTech Connect

    Dietrich, J.; Abou-Ras, D. Schmidt, S. S.; Rissom, T.; Unold, T.; Cojocaru-Mirédin, O.; Niermann, T.; Lehmann, M.; Koch, C. T.; Boit, C.

    2014-03-14

    Thin-film solar cells based on Cu(In,Ga)Se{sub 2} (CIGSe) reach high power-conversion efficiencies in spite of large dislocation densities of up to 10{sup 10}–10{sup 11} cm{sup −2}. The present work gives insight into the structural and compositional properties of dislocations in CIGSe thin films, which are embedded in a complete solar cell stack. These properties are related to the average electrical potential distributions obtained by means of inline electron holography. At a part of the dislocations studied, the average electrostatic potential shows local minima, all with depths of about −1.4 V. The measured average electrostatic potential distributions were modeled in order to reveal possible influences from strain fields, excess charge, and also compositional changes at the dislocation core. Cu depletion around the dislocation core, as evidenced by atom-probe tomography, explains best the measured potential wells. Their influences of the strain field around the dislocation core and of excess charge at the dislocation core are small. A structural model of dislocations in CIGSe thin films is provided which includes a Cu-depleted region around the dislocation core and gives a possible explanation for why decent photovoltaic performances are possible in the presence of rather large dislocation densities.

  13. Origins of electrostatic potential wells at dislocations in polycrystalline Cu(In,Ga)Se2 thin films

    NASA Astrophysics Data System (ADS)

    Dietrich, J.; Abou-Ras, D.; Schmidt, S. S.; Rissom, T.; Unold, T.; Cojocaru-Mirédin, O.; Niermann, T.; Lehmann, M.; Koch, C. T.; Boit, C.

    2014-03-01

    Thin-film solar cells based on Cu(In,Ga)Se2 (CIGSe) reach high power-conversion efficiencies in spite of large dislocation densities of up to 1010-1011 cm-2. The present work gives insight into the structural and compositional properties of dislocations in CIGSe thin films, which are embedded in a complete solar cell stack. These properties are related to the average electrical potential distributions obtained by means of inline electron holography. At a part of the dislocations studied, the average electrostatic potential shows local minima, all with depths of about -1.4 V. The measured average electrostatic potential distributions were modeled in order to reveal possible influences from strain fields, excess charge, and also compositional changes at the dislocation core. Cu depletion around the dislocation core, as evidenced by atom-probe tomography, explains best the measured potential wells. Their influences of the strain field around the dislocation core and of excess charge at the dislocation core are small. A structural model of dislocations in CIGSe thin films is provided which includes a Cu-depleted region around the dislocation core and gives a possible explanation for why decent photovoltaic performances are possible in the presence of rather large dislocation densities.

  14. Protein Recovery from Secondary Paper Sludge and Its Potential Use as Wood Adhesive

    NASA Astrophysics Data System (ADS)

    Pervaiz, Muhammad

    cross-linking, the synergy of adhesive blends was evaluated through classical rule-of-mixture. The findings of this study warrants further investigation concerning other potential uses of recovered sludge protein, especially as food supplements and economic implications.

  15. A divide and conquer real-space approach for all-electron molecular electrostatic potentials and interaction energies

    NASA Astrophysics Data System (ADS)

    Losilla, S. A.; Sundholm, D.

    2012-06-01

    A computational scheme to perform accurate numerical calculations of electrostatic potentials and interaction energies for molecular systems has been developed and implemented. Molecular electron and energy densities are divided into overlapping atom-centered atomic contributions and a three-dimensional molecular remainder. The steep nuclear cusps are included in the atom-centered functions making the three-dimensional remainder smooth enough to be accurately represented with a tractable amount of grid points. The one-dimensional radial functions of the atom-centered contributions as well as the three-dimensional remainder are expanded using finite element functions. The electrostatic potential is calculated by integrating the Coulomb potential for each separate density contribution, using our tensorial finite element method for the three-dimensional remainder. We also provide algorithms to compute accurate electron-electron and electron-nuclear interactions numerically using the proposed partitioning. The methods have been tested on all-electron densities of 18 reasonable large molecules containing elements up to Zn. The accuracy of the calculated Coulomb interaction energies is in the range of 10-3 to 10-6 Eh when using an equidistant grid with a step length of 0.05 a0.

  16. Adhesion Potential of Intestinal Microbes Predicted by Physico-Chemical Characterization Methods

    PubMed Central

    Niederberger, Tobias; Fischer, Peter; Rühs, Patrick Alberto

    2015-01-01

    Bacterial adhesion to epithelial surfaces affects retention time in the human gastro-intestinal tract and therefore significantly contributes to interactions between bacteria and their hosts. Bacterial adhesion among other factors is strongly influenced by physico-chemical factors. The accurate quantification of these physico-chemical factors in adhesion is however limited by the available measuring techniques. We evaluated surface charge, interfacial rheology and tensiometry (interfacial tension) as novel approaches to quantify these interactions and evaluated their biological significance via an adhesion assay using intestinal epithelial surface molecules (IESM) for a set of model organisms present in the human gastrointestinal tract. Strain pairs of Lactobacillus plantarum WCFS1 with its sortase knockout mutant Lb. plantarum NZ7114 and Lb. rhamnosus GG with Lb. rhamnosus DSM 20021T were used with Enterococcus faecalis JH2-2 as control organism. Intra-species comparison revealed significantly higher abilities for Lb. plantarum WCSF1 and Lb. rhamnosus GG vs. Lb. plantarum NZ7114 and Lb. rhamnosus DSM 20021T to dynamically increase interfacial elasticity (10−2 vs. 10−3 Pa*m) and reduce interfacial tension (32 vs. 38 mN/m). This further correlated for Lb. plantarum WCSF1 and Lb. rhamnosus GG vs. Lb. plantarum NZ7114 and Lb. rhamnosus DSM 20021T with the decrease of relative hydrophobicity (80–85% vs. 57–63%), Zeta potential (-2.9 to -4.5 mV vs. -8.0 to -13.8 mV) and higher relative adhesion capacity to IESM (3.0–5.0 vs 1.5–2.2). Highest adhesion to the IESM collagen I and fibronectin was found for Lb. plantarum WCFS1 (5.0) and E. faecalis JH2-2 (4.2) whereas Lb. rhamnosus GG showed highest adhesion to type II mucus (3.8). Significantly reduced adhesion (2 fold) to the tested IESM was observed for Lb. plantarum NZ7114 and Lb. rhamnosus DSM 20021T corresponding with lower relative hydrophobicity, Zeta potential and abilities to modify interfacial

  17. An improved fast multipole method for electrostatic potential calculations in a class of coarse-grained molecular simulations

    SciTech Connect

    Poursina, Mohammad; Anderson, Kurt S.

    2014-08-01

    This paper presents a novel algorithm to approximate the long-range electrostatic potential field in the Cartesian coordinates applicable to 3D coarse-grained simulations of biopolymers. In such models, coarse-grained clusters are formed via treating groups of atoms as rigid and/or flexible bodies connected together via kinematic joints. Therefore, multibody dynamic techniques are used to form and solve the equations of motion of such coarse-grained systems. In this article, the approximations for the potential fields due to the interaction between a highly negatively/positively charged pseudo-atom and charged particles, as well as the interaction between clusters of charged particles, are presented. These approximations are expressed in terms of physical and geometrical properties of the bodies such as the entire charge, the location of the center of charge, and the pseudo-inertia tensor about the center of charge of the clusters. Further, a novel substructuring scheme is introduced to implement the presented far-field potential evaluations in a binary tree framework as opposed to the existing quadtree and octree strategies of implementing fast multipole method. Using the presented Lagrangian grids, the electrostatic potential is recursively calculated via sweeping two passes: assembly and disassembly. In the assembly pass, adjacent charged bodies are combined together to form new clusters. Then, the potential field of each cluster due to its interaction with faraway resulting clusters is recursively calculated in the disassembly pass. The method is highly compatible with multibody dynamic schemes to model coarse-grained biopolymers. Since the proposed method takes advantage of constant physical and geometrical properties of rigid clusters, improvement in the overall computational cost is observed comparing to the tradition application of fast multipole method.

  18. Two-spacecraft charged particle observations interpreted in terms of electrostatic potential drops along polar cap field lines

    NASA Astrophysics Data System (ADS)

    Pollock, C. J.; Chappell, C. R.; Horwitz, J. L.; Winningham, J. D.

    We are studying the possible occurrence and magnitude of field-aligned electrostatic potential drops over the ionospheric polar caps. For this purpose, signatures in upgoing and downgoing photoelectrons, obtained in the topside ionosphere using the low altitude plasma instrument (LAPI) on the Dynamics Explorer 2 (DE 2), spacecraft are analyzed [Winningham and Gurgiolo, 1982]. These data are compared with positive ion data obtained at high altitude using the retarding ion mass spectrometer (RIMS) on the DE 1 spacecraft. Data were selected from intervals when DE 1 and DE 2 were approximately connected along polar cap magnetic field lines and when upflowing 0+ beams were observed in the RIMS data. We present here one case in which the comparison of data from the two DE spacecraft is quite favorable regarding its interpretation in terms of a field-aligned potential drop.

  19. Self-consistent treatment of the local dielectric permittivity and electrostatic potential in solution for polarizable macromolecular force fields

    PubMed Central

    Hassan, Sergio A.

    2012-01-01

    A self-consistent method is presented for the calculation of the local dielectric permittivity and electrostatic potential generated by a solute of arbitrary shape and charge distribution in a polar and polarizable liquid. The structure and dynamics behavior of the liquid at the solute/liquid interface determine the spatial variations of the density and the dielectric response. Emphasis here is on the treatment of the interface. The method is an extension of conventional methods used in continuum protein electrostatics, and can be used to estimate changes in the static dielectric response of the liquid as it adapts to charge redistribution within the solute. This is most relevant in the context of polarizable force fields, during electron structure optimization in quantum chemical calculations, or upon charge transfer. The method is computationally efficient and well suited for code parallelization, and can be used for on-the-fly calculations of the local permittivity in dynamics simulations of systems with large and heterogeneous charge distributions, such as proteins, nucleic acids, and polyelectrolytes. Numerical calculation of the system free energy is discussed for the general case of a liquid with field-dependent dielectric response. PMID:22920098

  20. The potential of sarcospan in adhesion complex replacement therapeutics for the treatment of muscular dystrophy.

    PubMed

    Marshall, Jamie L; Kwok, Yukwah; McMorran, Brian J; Baum, Linda G; Crosbie-Watson, Rachelle H

    2013-09-01

    Three adhesion complexes span the sarcolemma and facilitate critical connections between the extracellular matrix and the actin cytoskeleton: the dystrophin- and utrophin-glycoprotein complexes and α7β1 integrin. Loss of individual protein components results in a loss of the entire protein complex and muscular dystrophy. Muscular dystrophy is a progressive, lethal wasting disease characterized by repetitive cycles of myofiber degeneration and regeneration. Protein-replacement therapy offers a promising approach for the treatment of muscular dystrophy. Recently, we demonstrated that sarcospan facilitates protein-protein interactions amongst the adhesion complexes and is an important potential therapeutic target. Here, we review current protein-replacement strategies, discuss the potential benefits of sarcospan expression, and identify important experiments that must be addressed for sarcospan to move to the clinic.

  1. Auto-Adhesion Potential of Extraocular Aqp0 during Teleost Development

    PubMed Central

    Chauvigné, François; Fjelldal, Per Gunnar; Cerdà, Joan; Finn, Roderick Nigel

    2016-01-01

    AQP0 water channels are the most abundant proteins expressed in the mammalian lens fiber membranes where they are essential for lens development and transparency. Unlike other aquaporin paralogs, mammalian AQP0 has a low intrinsic water permeability, but can form cell-to-cell junctions between the lens fibers. It is not known whether the adhesive properties of AQP0 is a derived feature found only in mammals, or exists as a conserved ancestral trait in non-mammalian vertebrates. Here we show that a tetraploid teleost, the Atlantic salmon, expresses four Aqp0 paralogs in the developing lens, but also expresses significant levels of aqp0 mRNAs and proteins in the epithelia of the pronephros, presumptive enterocytes, gill filament and epidermis. Quantitative PCR reveals that aqp0 mRNA titres increase by three orders of magnitude between the onset of somitogenesis and pigmentation of the eye. Using in situ hybridization and specific antisera, we show that at least two of the channels (Aqp0a1, -0b1 and/or -0b2) are localized in the extraocular basolateral and apical membranes, while Aqp0a2 is lens-specific. Heterologous expression of the Aqp0 paralogs in adhesion-deficient mouse fibolast L-cells reveals that, as for human AQP0, each intact salmon channel retains cell-to-cell adhesive properties. The strongest Aqp0 interactions are auto-adhesion, suggesting that homo-octamers likely form the intercellular junctions of the developing lens and epithelial tissues. The present data are thus the first to show the adhesion potential of Aqp0 channels in a non-mammalian vertebrate, and further uncover a novel extraocular role of the channels during vertebrate development. PMID:27153052

  2. Helical modulation of the electrostatic plasma potential due to edge magnetic islands induced by resonant magnetic perturbation fields at TEXTOR

    SciTech Connect

    Ciaccio, G. Spizzo, G.; Schmitz, O. Frerichs, H.; Abdullaev, S. S.; Evans, T. E.; White, R. B.

    2015-10-15

    The electrostatic response of the edge plasma to a magnetic island induced by resonant magnetic perturbations to the plasma edge of the circular limiter tokamak TEXTOR is analyzed. Measurements of plasma potential are interpreted by simulations with the Hamiltonian guiding center code ORBIT. We find a strong correlation between the magnetic field topology and the poloidal modulation of the measured plasma potential. The ion and electron drifts yield a predominantly electron driven radial diffusion when approaching the island X-point while ion diffusivities are generally an order of magnitude smaller. This causes a strong radial electric field structure pointing outward from the island O-point. The good agreement found between measured and modeled plasma potential connected to the enhanced radial particle diffusivities supports that a magnetic island in the edge of a tokamak plasma can act as convective cell. We show in detail that the particular, non-ambipolar drifts of electrons and ions in a 3D magnetic topology account for these effects. An analytical model for the plasma potential is implemented in the code ORBIT, and analyses of ion and electron radial diffusion show that both ion- and electron-dominated transport regimes can exist, which are known as ion and electron root solutions in stellarators. This finding and comparison with reversed field pinch studies and stellarator literature suggest that the role of magnetic islands as convective cells and hence as major radial particle transport drivers could be a generic mechanism in 3D plasma boundary layers.

  3. Detailed plasma potential measurements in a radio-frequency expanding plasma obtained from various electrostatic probes

    SciTech Connect

    Lafleur, T.; Charles, C.; Boswell, R. W.

    2009-04-15

    On-axis plasma potential measurements have been made with an emissive probe in a low pressure (0.044 Pa) rf expanding plasma containing an ion beam. The beam is detected with a retarding field energy analyzer (RFEA), and is seen to disappear at high pressure (0.39 Pa). The emissive probe measurements are in very good agreement with corresponding measurements made with two separate RFEAs, and the results indicate that the floating potential of the strongly emitting probe gives an accurate measure of the plasma potential under the present conditions.

  4. Sweating the small stuff: Glycoproteins in human sweat and their unexplored potential for microbial adhesion.

    PubMed

    Peterson, Robyn A; Gueniche, Audrey; Adam de Beaumais, Ségolène; Breton, Lionel; Dalko-Csiba, Maria; Packer, Nicolle H

    2016-03-01

    There is increasing evidence that secretory fluids such as tears, saliva and milk play an important role in protecting the human body from infection via a washing mechanism involving glycan-mediated adhesion of potential pathogens to secretory glycoproteins. Interaction of sweat with bacteria is well established as the cause of sweat-associated malodor. However, the role of sweat glycoproteins in microbial attachment has received little, if any, research interest in the past. In this review, we demonstrate how recent published studies involving high-throughput proteomic analysis have inadvertently, and fortuitously, exposed an abundance of glycoproteins in sweat, many of which have also been identified in other secretory fluids. We bring together research demonstrating microbial adhesion to these secretory glycoproteins in tears, saliva and milk and suggest a similar role of the sweat glycoproteins in mediating microbial attachment to sweat and/or skin. The contribution of glycan-mediated microbial adhesion to sweat glycoproteins, and the associated impact on sweat derived malodor and pathogenic skin infections are unchartered new research areas that we are beginning to explore.

  5. Relative contribution of combined kinetic and exchange energy terms vs the electronic component of molecular electrostatic potential in hardness potential derivatives.

    PubMed

    Bhattacharjee, Rituparna; Roy, Ram Kinkar

    2013-11-14

    The relative contribution of the sum of kinetic [(10/9)CFρ(r)2/3] and exchange energy [(4/9)CXρ(r)1/3] terms to that of the electronic part of the molecular electrostatic potential [Vel(r)] in the variants of hardness potential is investigated to assess the proposed definition of Δ+h(k) = −[VelN+1(k) – VelN(k)] and Δ–h(k) = −[VelN(k) – VelN–1(k)] (Saha; et al. J. Comput. Chem. 2013, 34, 662). Some substituted benzenes and polycyclic aromatic hydrocarbons (PAHs) (undergoing electrophilic aromatic substitution), carboxylic acids, and their derivatives are chosen to carry out the theoretical investigation as stated above. Intra- and intermolecular reactivity trends generated by Δ+h(k) and Δ–h(k) are found to be satisfactory and are correlated reasonably well with experimental results.

  6. HEATING OF SIMPLE SOLUTIONS AND EMULSIONS EXPOSED TO HIGH FREQUENCY HIGH POTENTIAL ELECTROSTATIC FIELDS

    PubMed Central

    Marshall, W. H.

    1930-01-01

    1. It is shown that the absorption in liquid dielectrics is a function of potential gradient (field intensity) as well as frequency and that for values of potential gradient above, at least 70 volts per millimeter, the rate of rise of temperature-frequency curve increases rapidly with frequency. 2. The presence of ions in measurable quantity considerably changes the absorption characteristics and apparently causes the values to remain constant, whereas the values for water drop about 40 per cent, during exposure. The absorption also changes rapidly with the concentration of the electrolyte. 3. Very high absorption values are found for an emulsion of cotton-seed oil in 1 per cent sodium oleate. It is shown that the absorption is due to the colloidal structure (with the possibility that the energy is dissipated at the phase boundaries). PMID:19872553

  7. Electrostatic potential fluctuation induced by charge discreteness in a nanoscale trench

    SciTech Connect

    Lee, Taesang; Kim, S. S.; Jho, Y. S.; Park, Gunyoung; Chang, C. S.

    2007-10-15

    A simplified two-dimensional Monte Carlo simulation is performed to estimate the charging potential fluctuations caused by strong binary Coulomb interactions between discrete charged particles in nanometer scale trenches. It is found that the discrete charge effect can be an important part of the nanoscale trench research, inducing scattering of ion trajectories in a nanoscale trench by a fluctuating electric field. The effect can enhance the ion deposition on the side walls and disperse the material contact energy of the incident ions, among others.

  8. Electrostatic Field Invisibility Cloak

    PubMed Central

    Lan, Chuwen; Yang, Yuping; Geng, Zhaoxin; Li, Bo; Zhou, Ji

    2015-01-01

    The invisibility cloak has been drawing much attention due to its new concept for manipulating many physical fields, from oscillating wave fields (electromagnetic, acoustic and elastic) to static magnetic fields, dc electric fields, and diffusive fields. Here, an electrostatic field invisibility cloak has been theoretically investigated and experimentally demonstrated to perfectly hide two dimensional objects without disturbing their external electrostatic fields. The desired cloaking effect has been achieved via both cancelling technology and transformation optics (TO). This study demonstrates a novel way for manipulating electrostatic fields, which shows promise for a wide range of potential applications. PMID:26552343

  9. Protein adsorption on dopamine-melanin films: role of electrostatic interactions inferred from zeta-potential measurements versus chemisorption.

    PubMed

    Bernsmann, Falk; Frisch, Benoît; Ringwald, Christian; Ball, Vincent

    2010-04-01

    We recently showed the possibility to build dopamine-melanin films of controlled thickness by successive immersions of a substrate in alkaline solutions of dopamine [F. Bernsmann, A. Ponche, C. Ringwald, J. Hemmerlé, J. Raya, B. Bechinger, J.-C. Voegel, P. Schaaf, V. Ball, J. Phys. Chem. C 113 (2009) 8234-8242]. In this work the structure and properties of such films are further explored. The zeta-potential of dopamine-melanin films is measured as a function of the total immersion time to build the film. It appears that the film bears a constant zeta-potential of (-39+/-3) mV after 12 immersion steps. These data are used to calculate the surface density of charged groups of the dopamine-melanin films at pH 8.5 that are mostly catechol or quinone imine chemical groups. Furthermore the zeta-potential is used to explain the adsorption of three model proteins (lysozyme, myoglobin, alpha-lactalbumin), which is monitored by quartz crystal microbalance. We come to the conclusion that protein adsorption on dopamine-melanin is not only determined by possible covalent binding between amino groups of the proteins and catechol groups of dopamine-melanin but that electrostatic interactions contribute to protein binding. Part of the adsorbed proteins can be desorbed by sodium dodecylsulfate solutions at the critical micellar concentration. The fraction of weakly bound proteins decreases with their isoelectric point. Additionally the number of available sites for covalent binding of amino groups on melanin grains is quantified.

  10. Xeroderma pigmentosum complementation group A protein is driven to nucleotide excision repair sites by the electrostatic potential of distorted DNA.

    PubMed

    Camenisch, Ulrike; Dip, Ramiro; Vitanescu, Mirela; Naegeli, Hanspeter

    2007-12-01

    The presumed DNA-binding cleft of xeroderma pigmentosum group A (XPA) protein, a key regulatory subunit of the eukaryotic nucleotide excision repair complex, displays a distinctive array of 6 positively charged amino acid side chains. Here, the molecular function of these closely spaced electropositive residues has been tested by systematic site-directed mutagenesis. After the introduction of single amino acid substitutions, the mutants were probed for protein-DNA interactions in electrophoretic mobility shift and photochemical crosslinking assays. This analysis led to the identification of a critical hot-spot for DNA substrate recognition composed of two neighboring lysines at codons 141 and 179 of the human XPA sequence. The replacement of other basic side chains in the DNA interaction domain conferred more moderate defects of substrate binding. When the function of XPA was tested as a fusion product with either mCherry or green-fluorescent protein, a glutamate substitution of one of the positively charged residues at positions 141 and 179 was sufficient to decrease DNA repair activity in human fibroblasts. Thus, the removal of a single cationic side chain abolished DNA-binding activity and significant excision repair defects could be induced by single charge inversions on the XPA surface, indicating that this molecular sensor participates in substrate recognition by monitoring the electrostatic potential of distorted DNA repair sites.

  11. Involvement of flocculin in negative potential-applied ITO electrode adhesion of yeast cells

    PubMed Central

    Koyama, Sumihiro; Tsubouchi, Taishi; Usui, Keiko; Uematsu, Katsuyuki; Tame, Akihiro; Nogi, Yuichi; Ohta, Yukari; Hatada, Yuji; Kato, Chiaki; Miwa, Tetsuya; Toyofuku, Takashi; Nagahama, Takehiko; Konishi, Masaaki; Nagano, Yuriko; Abe, Fumiyoshi

    2015-01-01

    The purpose of this study was to develop novel methods for attachment and cultivation of specifically positioned single yeast cells on a microelectrode surface with the application of a weak electrical potential. Saccharomyces cerevisiae diploid strains attached to an indium tin oxide/glass (ITO) electrode to which a negative potential between −0.2 and −0.4 V vs. Ag/AgCl was applied, while they did not adhere to a gallium-doped zinc oxide/glass electrode surface. The yeast cells attached to the negative potential-applied ITO electrodes showed normal cell proliferation. We found that the flocculin FLO10 gene-disrupted diploid BY4743 mutant strain (flo10Δ /flo10Δ) almost completely lost the ability to adhere to the negative potential-applied ITO electrode. Our results indicate that the mechanisms of diploid BY4743 S. cerevisiae adhesion involve interaction between the negative potential-applied ITO electrode and the Flo10 protein on the cell wall surface. A combination of micropatterning techniques of living single yeast cell on the ITO electrode and omics technologies holds potential of novel, highly parallelized, microchip-based single-cell analysis that will contribute to new screening concepts and applications. PMID:26187908

  12. A self-consistent, microenvironment modulated screened coulomb potential approximation to calculate pH-dependent electrostatic effects in proteins.

    PubMed Central

    Mehler, E L; Guarnieri, F

    1999-01-01

    An improved approach is presented for calculating pH-dependent electrostatic effects in proteins using sigmoidally screened Coulomb potentials (SCP). It is hypothesized that a key determinant of seemingly aberrant behavior in pKa shifts is due to the properties of the unique microenvironment around each residue. To help demonstrate this proposal, an approach is developed to characterize the microenvironments using the local hydrophobicity/hydrophilicity around each residue of the protein. The quantitative characterization of the microenvironments shows that the protein is a complex mosaic of differing dielectric regions that provides a physical basis for modifying the dielectric screening functions: in more hydrophobic microenvironments the screening decreases whereas the converse applies to more hydrophilic regions. The approach was applied to seven proteins providing more than 100 measured pKa values and yielded a root mean square deviation of 0.5 between calculated and experimental values. The incorporation of the local hydrophobicity characteristics into the algorithm allowed the resolution of some of the more intractable problems in the calculation of pKa. Thus, the divergent shifts of the pKa of Glu-35 and Asp-66 in hen egg white lysozyme, which are both about 90% buried, was correctly predicted. Mechanistically, the divergence occurs because Glu-35 is in a hydrophobic microenvironment, while Asp-66 is in a hydrophilic microenvironment. Furthermore, because the calculation of the microenvironmental effects takes very little CPU time, the computational speed of the SCP formulation is conserved. Finally, results from different crystal structures of a given protein were compared, and it is shown that the reliability of the calculated pKa values is sufficient to allow identification of conformations that may be more relevant for the solution structure. PMID:10388736

  13. Effects of electronic coupling and electrostatic potential on charge transport in carbon-based molecular electronic junctions

    PubMed Central

    2016-01-01

    Summary Molecular junctions consisting of 2–20 nm thick layers of organic oligomers oriented between a conducting carbon substrate and a carbon/gold top contact have proven to be reproducible and reliable, and will soon enter commercial production in audio processing circuits. The covalent, conjugated bond between one or both sp2-hybridized carbon contacts and an aromatic molecular layer is distinct from the more common metal/molecule or silicon/molecule structures in many reported molecular junctions. Theoretical observations based on density functional theory are presented here, which model carbon-based molecular junctions as single molecules and oligomers between fragments of graphene. Electronic coupling between the molecules and the contacts is demonstrated by the formation of hybrid orbitals in the model structure, which have significant electron density on both the graphene and the molecule. The energies of such hybrid orbitals correlate with tunneling barriers determined experimentally, and electronic coupling between the two graphene fragments in the model correlates with experimentally observed attenuation of transport with molecular layer thickness. Electronic coupling is affected significantly by the dihedral angle between the planes of the graphene and the molecular π-systems, but is absent only when the two planes are orthogonal. Coupling also results in partial charge transfer between the graphene contacts and the molecular layer, which results in a shift in electrostatic potential which affects the observed tunneling barrier. Although the degree of partial charge transfer is difficult to calculate accurately, it does provide a basis for the “vacuum level shift” observed in many experiments, including transport and ultraviolet photoelectron spectroscopy of molecular layers on conductors. PMID:26925350

  14. Ab initio study of the electrostatic multipole nature of torsional potentials in CH3SSCH3, CH3SSH, and HOOH

    NASA Technical Reports Server (NTRS)

    Sokalski, W. A.; Lai, J.; Luo, N.; Sun, S.; Shibata, M.; Ornstein, R.; Rein, R.

    1991-01-01

    The origin of torsional potentials in H3CSSCH3, H3CSSH, and HOOH and the anisotropy of the local charge distribution has been analyzed in terms of atomic multipoles calculated from the ab initio LCAO-MO-SCF wave function in the 6-31G* basis set. The results indicate that for longer -S-S-bonds the major contribution to these torsional barriers are electrostatic interactions of the atomic multipoles located on two atoms forming the rotated bond. This finding demonstrates the important role of electrostatic 1-2 interatomic interactions, usually neglected in conformational studies. It also opens the possibility to derive directly from accurate ab initio wave functions a simple nonempirical torsional potential involving atomic multipoles of two bonded atoms defining the torsional angle. For shorter -O-O- bonds, use of more precise models and inclusion of 1-3 interactions seems to be necessary.

  15. Electrostatic potentials of the S-locus F-box proteins contribute to the pollen S specificity in self-incompatibility in Petunia hybrida.

    PubMed

    Li, Junhui; Zhang, Yue; Song, Yanzhai; Zhang, Hui; Fan, Jiangbo; Li, Qun; Zhang, Dongfen; Xue, Yongbiao

    2017-01-01

    Self-incompatibility (SI) is a self/non-self discrimination system found widely in angiosperms and, in many species, is controlled by a single polymorphic S-locus. In the Solanaceae, Rosaceae and Plantaginaceae, the S-locus encodes a single S-RNase and a cluster of S-locus F-box (SLF) proteins to control the pistil and pollen expression of SI, respectively. Previous studies have shown that their cytosolic interactions determine their recognition specificity, but the physical force between their interactions remains unclear. In this study, we show that the electrostatic potentials of SLF contribute to the pollen S specificity through a physical mechanism of 'like charges repel and unlike charges attract' between SLFs and S-RNases in Petunia hybrida. Strikingly, the alteration of a single C-terminal amino acid of SLF reversed its surface electrostatic potentials and subsequently the pollen S specificity. Collectively, our results reveal that the electrostatic potentials act as a major physical force between cytosolic SLFs and S-RNases, providing a mechanistic insight into the self/non-self discrimination between cytosolic proteins in angiosperms.

  16. Focal Adhesion Kinase as a Potential Target in AML and MDS.

    PubMed

    Carter, Bing Z; Mak, Po Yee; Wang, Xiangmeng; Yang, Hui; Garcia-Manero, Guillermo; Mak, Duncan; Mu, Hong; Ruvolo, Vivian; Qiu, Yihua; Coombes, Kevin; Zhang, Nianxiang; Ragon, Brittany; Weaver, David T; Pachter, Jonathan A; Kornblau, Steven; Andreeff, Michael

    2017-03-07

    Although overexpression/activation of focal adhesion kinase (FAK) is widely known in solid tumors to control cell growth, survival, invasion, metastasis, gene expression, and stem cell self-renewal, its expression and function in myeloid leukemia are not well investigated. Using reverse-phase protein arrays in large cohorts of newly diagnosed acute myeloid leukemia (AML) and myeloid dysplastic syndrome (MDS) samples, we found that high FAK expression was associated with unfavorable cytogenetics (P = 2 x 10-4) and relapse (P = 0.02) in AML. FAK expression was significantly lower in patients with FLT3-ITD (P = 0.0024) or RAS (P = 0.05) mutations and strongly correlated with p-SRC and integrinβ3 levels. FAK protein levels were significantly higher in CD34+ (P = 5.42 x 10-20) and CD34+ CD38- MDS (P = 7.62 x 10-9) cells compared to normal CD34+ cells. MDS patients with higher FAK in CD34+ cells tended to have better OS (P = 0.05). FAK expression was significantly higher in MDS patients who later transformed to compared with not transformed to AML and in AML patients who transformed from MDS compared with those with de novo AML. Co-culture with mesenchymal stromal cells (MSCs) increased FAK expression in AML cells. Inhibition of FAK decreased MSC-mediated adhesion/migration and viability of AML cells and prolonged survival in an AML xenograft murine model. Our results suggest that FAK regulates leukemia-stromal interactions and supports leukemia cell survival; hence FAK is a potential therapeutic target in myeloid leukemia.

  17. Design and calibration of a scanning force microscope for friction, adhesion, and contact potential studies

    NASA Astrophysics Data System (ADS)

    Koleske, D. D.; Lee, G. U.; Gans, B. I.; Lee, K. P.; DiLella, D. P.; Wahl, K. J.; Barger, W. R.; Whitman, L. J.; Colton, R. J.

    1995-09-01

    We present the design and calibration of a scanning force microscope which can be used to study friction, adhesion, and contact potential differences between the cantilever tip and surface. The microscope uses a modular design where the laser, cantilever/sample holder, reflecting mirror, and detector are mounted directly on an optical table. The laser, reflecting mirror, and detector are mounted on translation and rotation stages. With this design the components can be rearranged to calibrate the Z piezo motion as a function of applied voltage. Using the detector micrometers, the detector response (voltage-to-distance relationship) can be determined after each series of measurements. The cantilever/sample holder is constructed such that the components are material matched and thermally compensated from a common reference point. This design feature minimizes thermal drift of the instrument. The instrument can be used in a contact scanning mode where both normal and lateral deflections of the cantilever are measured. In addition, the instrument can be used in frictional force studies, force curve mapping of the surface, and contact potential measurements. We present examples of each, including a detailed account of the instrument design and calibration.

  18. Electrostatics at the nanoscale.

    PubMed

    Walker, David A; Kowalczyk, Bartlomiej; de la Cruz, Monica Olvera; Grzybowski, Bartosz A

    2011-04-01

    Electrostatic forces are amongst the most versatile interactions to mediate the assembly of nanostructured materials. Depending on experimental conditions, these forces can be long- or short-ranged, can be either attractive or repulsive, and their directionality can be controlled by the shapes of the charged nano-objects. This Review is intended to serve as a primer for experimentalists curious about the fundamentals of nanoscale electrostatics and for theorists wishing to learn about recent experimental advances in the field. Accordingly, the first portion introduces the theoretical models of electrostatic double layers and derives electrostatic interaction potentials applicable to particles of different sizes and/or shapes and under different experimental conditions. This discussion is followed by the review of the key experimental systems in which electrostatic interactions are operative. Examples include electroactive and "switchable" nanoparticles, mixtures of charged nanoparticles, nanoparticle chains, sheets, coatings, crystals, and crystals-within-crystals. Applications of these and other structures in chemical sensing and amplification are also illustrated.

  19. Large electrostatic accelerators

    SciTech Connect

    Jones, C.M.

    1984-01-01

    The increasing importance of energetic heavy ion beams in the study of atomic physics, nuclear physics, and materials science has partially or wholly motivated the construction of a new generation of large electrostatic accelerators designed to operate at terminal potentials of 20 MV or above. In this paper, the author briefly discusses the status of these new accelerators and also discusses several recent technological advances which may be expected to further improve their performance. The paper is divided into four parts: (1) a discussion of the motivation for the construction of large electrostatic accelerators, (2) a description and discussion of several large electrostatic accelerators which have been recently completed or are under construction, (3) a description of several recent innovations which may be expected to improve the performance of large electrostatic accelerators in the future, and (4) a description of an innovative new large electrostatic accelerator whose construction is scheduled to begin next year. Due to time and space constraints, discussion is restricted to consideration of only tandem accelerators.

  20. Spectroscopic and DFT studies of second-sphere variants of the type 1 copper site in azurin: covalent and nonlocal electrostatic contributions to reduction potentials.

    PubMed

    Hadt, Ryan G; Sun, Ning; Marshall, Nicholas M; Hodgson, Keith O; Hedman, Britt; Lu, Yi; Solomon, Edward I

    2012-10-10

    The reduction potentials (E(0)) of type 1 (T1) or blue copper (BC) sites in proteins and enzymes with identical first coordination spheres around the redox active copper ion can vary by ~400 mV. Here, we use a combination of low-temperature electronic absorption and magnetic circular dichroism, electron paramagnetic resonance, resonance Raman, and S K-edge X-ray absorption spectroscopies to investigate a series of second-sphere variants--F114P, N47S, and F114N in Pseudomonas aeruginosa azurin--which modulate hydrogen bonding to and protein-derived dipoles nearby the Cu-S(Cys) bond. Density functional theory calculations correlated to the experimental data allow for the fractionation of the contributions to tuning E(0) into covalent and nonlocal electrostatic components. These are found to be significant, comparable in magnitude, and additive for active H-bonds, while passive H-bonds are mostly nonlocal electrostatic in nature. For dipoles, these terms can be additive to or oppose one another. This study provides a methodology for uncoupling covalency from nonlocal electrostatics, which, when coupled to X-ray crystallographic data, distinguishes specific local interactions from more long-range protein/active interactions, while affording further insight into the second-sphere mechanisms available to the protein to tune the E(0) of electron-transfer sites in biology.

  1. Spectroscopic and DFT Studies of Second Sphere Variants of the Type 1 Copper Site in Azurin: Covalent and Non-Local Electrostatic Contributions to Reduction Potentials

    PubMed Central

    Hadt, Ryan G.; Sun, Ning; Marshall, Nicholas M.; Hodgson, Keith O.; Hedman, Britt; Lu, Yi; Solomon, Edward I.

    2012-01-01

    The reduction potentials (E0) of type 1 (T1) or blue copper (BC) sites in proteins and enzymes with identical first coordination spheres around the redox active copper ion can vary by ~400 mV. Here, we use a combination of low temperature electronic absorption and magnetic circular dichroism, electron paramagnetic resonance, resonance Raman, and S K-edge X-ray absorption spectroscopies to investigate a series of second sphere variants—F114P, N47S, and F114N in Pseudomonas aeruginosa azurin (Az)—which modulate hydrogen bonding to and protein derived dipoles nearby the Cu-S(Cys) bond. Density functional theory (DFT) calculations correlated to the experimental data allow for the fractionation of the contributions to tuning E0 into covalent and non-local electrostatic components. These are found to be significant, comparable in magnitude, and additive for active H-bonds, while passive H-bonds are mostly non-local electrostatic in nature. For dipoles, these terms can be additive to or oppose one another. This study provides a methodology for uncoupling covalency from non-local electrostatics, which, when coupled to X-ray crystallographic data, distinguishes specific local interactions from more long range protein/active interactions, while affording further insight into the second sphere mechanisms available to the protein to tune the E0 of electron transfer sites in biology. PMID:22985400

  2. Electrostatic potential distribution of the gene V protein from Ff phage facilitates cooperative DNA binding: a model of the GVP-ssDNA complex.

    PubMed Central

    Guan, Y.; Zhang, H.; Wang, A. H.

    1995-01-01

    The crystal structure of the gene V protein (GVP) from the Ff filamentous phages (M13, fl, fd) has been solved for the wild-type and two mutant (Y41F and Y41H) proteins at high resolution. The Y41H mutant crystal structure revealed crystal packing interactions, which suggested a plausible scheme for constructing the polymeric protein shell of the GVP-single-stranded DNA (ssDNA) complex (Guan Y, et al., 1994, Biochemistry 33:7768-7778). The electrostatic potentials of the isolated and the cooperatively formed protein shell have been calculated using the program GRASP and they revealed a highly asymmetric pattern of the electrostatic charge distribution. The inner surface of the putative DNA-binding channel is positively charged, whereas the opposite outer surface is nearly neutral. The electrostatic calculation further demonstrated that the formation of the helical protein shell enhanced the asymmetry of the electrostatic distribution. A model of the GVP-ssDNA complex with the n = 4 DNA-binding mode could be built with only minor conformational perturbation to the GVP protein shell. The model is consistent with existing biochemical and biophysical data and provides clues to the properties of GVP, including the high cooperatively of the protein binding to ssDNA. The two antiparallel ssDNA strands form a helical ribbon with the sugar-phosphate backbones at the middle and the bases pointing away from each other. The bases are stacked and the Phe 73 residue is intercalated between two bases. The optimum binding to a tetranucleotide unit requires the participation of four GVP dimers, which may explain the cooperativity of the GVP binding to DNA. PMID:7757008

  3. A comparative study on carbon, boron-nitride, boron-phosphide and silicon-carbide nanotubes based on surface electrostatic potentials and average local ionization energies.

    PubMed

    Esrafili, Mehdi D; Behzadi, Hadi

    2013-06-01

    A density functional theory study was carried out to predict the electrostatic potentials as well as average local ionization energies on both the outer and the inner surfaces of carbon, boron-nitride (BN), boron-phosphide (BP) and silicon-carbide (SiC) single-walled nanotubes. For each nanotube, the effect of tube radius on the surface potentials and calculated average local ionization energies was investigated. It is found that SiC and BN nanotubes have much stronger and more variable surface potentials than do carbon and BP nanotubes. For the SiC, BN and BP nanotubes, there are characteristic patterns of positive and negative sites on the outer lateral surfaces. On the other hand, a general feature of all of the systems studied is that stronger potentials are associated with regions of higher curvature. According to the evaluated surface electrostatic potentials, it is concluded that, for the narrowest tubes, the water solubility of BN tubes is slightly greater than that of SiC followed by carbon and BP nanotubes.

  4. Complex coacervates as a foundation for synthetic underwater adhesives.

    PubMed

    Stewart, Russell J; Wang, Ching Shuen; Shao, Hui

    2011-09-14

    Complex coacervation was proposed to play a role in the formation of the underwater bioadhesive of the Sandcastle worm (Phragmatopoma californica) based on the polyacidic and polybasic nature of the glue proteins and the balance of opposite charges at physiological pH. Morphological studies of the secretory system suggested that the natural process does not involve complex coacervation as commonly defined. The distinction may not be important because electrostatic interactions likely play an important role in the formation of the sandcastle glue. Complex coacervation has also been invoked in the formation of adhesive underwater silk fibers of caddisfly larvae and the adhesive plaques of mussels. A process similar to complex coacervation, that is, condensation and dehydration of biopolyelectrolytes through electrostatic associations, seems plausible for the caddisfly silk. This much is clear, the sandcastle glue complex coacervation model provided a valuable blueprint for the synthesis of a biomimetic, water-borne, underwater adhesive with demonstrated potential for repair of wet tissue.

  5. Electrostatic monitoring

    DOEpatents

    Orr, Christopher Henry; Luff, Craig Janson; Dockray, Thomas; Macarthur, Duncan Whittemore

    2001-01-01

    The apparatus and method provide a technique for more simply measuring alpha and/or beta emissions arising from items or locations. The technique uses indirect monitoring of the emissions by detecting ions generated by the emissions, the ions being attracted electrostatically to electrodes for discharge of collection. The apparatus and method employ a chamber which is sealed around the item or location during monitoring with no air being drawn into or expelled from the chamber during the monitoring process. A simplified structure and operations arises as a result, but without impairing the efficiency and accuracy of the detection technique.

  6. Antibacterial and cell-adhesive polypeptide and poly(ethylene glycol) hydrogel as a potential scaffold for wound healing.

    PubMed

    Song, Airong; Rane, Aboli A; Christman, Karen L

    2012-01-01

    The ideal wound-healing scaffold should provide the appropriate physical and mechanical properties to prevent secondary infection, as well as an excellent physiological environment to facilitate cell adhesion, proliferation and/or differentiation. Therefore, we developed a synthetic cell-adhesive polypeptide hydrogel with inherent antibacterial activity. A series of polypeptides, poly(Lys)(x)(Ala)(y) (x+y=100), with varied hydrophobicity via metal-free ring-opening polymerization of NCA-Lys(Boc) and NCA-Ala monomers (NCA=N-carboxylic anhydride) mediated by hexamethyldisilazane (HMDS) were synthesized. These polypeptides were cross-linked with 6-arm polyethylene glycol (PEG)-amide succinimidyl glutarate (ASG) (M(w)=10K) to form hydrogels with a gelation time of five minutes and a storage modulus (G') of 1400-3000 Pa as characterized by rheometry. The hydrogel formed by cross-linking of poly(Lys)(60)(Ala)(40) (5 wt.%) and 6-arm PEG-ASG (16 wt.%) (Gel-III) exhibited cell adhesion and cell proliferation activities superior to other polypeptide hydrogels. In addition, Gel-III displays significant antibacterial activity against Escherichia coli JM109 and Staphylococcus aureus ATCC25923. Thus, we have developed a novel, cell-adhesive hydrogel with inherent antibacterial activity as a potential scaffold for cutaneous wound healing.

  7. Antibacterial and Cell-adhesive Polypeptide and Poly(ethylene glycol) Hydrogel as a Potential Scaffold for Wound Healing

    PubMed Central

    Song, Airong; Rane, Aboli A.; Christman, Karen L.

    2011-01-01

    The ideal wound healing scaffold should provide the appropriate physical and mechanical properties to prevent secondary infection, as well as an excellent physiological environment to facilitate cell adhesion, proliferation and/or differentiation. Therefore, we developed a synthetic cell-adhesive polypeptide hydrogel with inherent antibacterial activity. A series of polypeptides, poly(Lys)x(Ala)y (x+y=100) with varied hydrophobicity via metal-free ring-opening polymerization of NCA-Lys(Boc) and NCA-Ala monomers (NCA = N-carboxylic anhydride) mediated by hexamethyldisilazane (HMDS) were synthesized. These polypeptides were cross-linked with 6-arm PEG-amide succinimidyl glutarate (ASG) (Mw = 10K) to form hydrogels with a gelation time of five minutes and a storage modulus (G') of 1400–3000 Pa as characterized by rheometry. The hydrogel formed by cross-linking of poly(Lys)60(Ala)40 (5 wt%) and 6-arm PEG-ASG (16 wt%) (Gel-III) exhibited cell adhesion and cell proliferation activities superior to other polypeptide hydrogels. In addition, Gel-III displays significant antibacterial activity against E. coli JM109 and S. aureus ATCC25923. Thus, we have developed a novel, cell-adhesive hydrogel with inherent antibacterial activity as a potential scaffold for cutaneous wound healing. PMID:22023748

  8. Electrostatic Potential Determined Magnetic Dynamics Observed in Two Mononuclear β-Diketone Dysprosium(III) Single-Molecule Magnets.

    PubMed

    Cen, Pei-Pei; Zhang, Sheng; Liu, Xiang-Yu; Song, Wei-Ming; Zhang, Yi-Quan; Xie, Gang; Chen, San-Ping

    2017-03-20

    Two β-diketone mononuclear Dy(III) compounds, formulated as Dy(BTFA)3(H2O)2 (1) and Dy(BTFA)3(bpy) (2) (BTFA = 3-benzoyl-1,1,1-trifluoroacetone, bpy = 2,2'-bipyridine), were prepared. Compound 1 can be identified to transform to 2 in the attendance of bpy coligand, when the local geometry symmetry of eight-coordinated Dy(III) ion changes from a dodecahedron (D2d) in 1 to a square antiprism (D4d) in 2. Fine-tuning structure aroused by auxiliary ligand has dramatical impact on magnetic properties of compounds 1 and 2. Magnetic investigations demonstrate that both 1 and 2 display dynamic magnetic relaxation of single-molecule magnets (SMMs) behavior with different effective barriers (ΔE/kB) of 93.09 K for 1 under zero direct-current (DC) field as well as 296.50 K for 1 and 151.01 K for 2 under 1200 Oe DC field, respectively. As noticed, compound 1 possesses higher effective barrier than 2, despite 1 exhibiting a lower geometrical symmetry of the Dy(III) ion. Ab initio studies reveal that the Kramers doublet ground state is predominantly axial with the gz tensors of two compounds matching the Ising-limit factor of 20 anticipated for the pure MJ = ±15/2 state. Electrostatic analysis confirms the uniaxial anisotropy directions, highlighting that the proper electrostatic distribution of the coordination sphere around Ln(III) center is the critical factor to improve the magnetic anisotropy and determine the dynamic behaviors of SMMs.

  9. Micromachined silicon electrostatic chuck

    SciTech Connect

    Anderson, R.A.; Seager, C.H.

    1994-12-31

    In the field of microelectronics, and in particular the fabrication of microelectronics during plasma etching processes, electrostatic chucks have been used to hold silicon wafers during the plasma etching process. Current electrostatic chucks that operate by the {open_quotes}Johnson-Rahbek Effect{close_quotes} consist of a metallic base plate that is typically coated with a thick layer of slightly conductive dielectric material. A silicon wafer of approximately the same size as the chuck is placed on top of the chuck and a potential difference of several hundred volts is applied between the silicon and the base plate of the electrostatic chuck. This causes an electrostatic attraction proportional to the square of the electric field in the gap between the silicon wafer and the chuck face. When the chuck is used in a plasma filled chamber the electric potential of the wafer tends to be fixed by the effective potential of the plasma. The purpose of the dielectric layer on the chuck is to prevent the silicon wafer from coming into direct electrical contact with the metallic part of the chuck and shorting out the potential difference. On the other hand, a small amount of conductivity appears to be desirable in the dielectric coating so that much of its free surface between points of contact with the silicon wafer is maintained near the potential of the metallic base plate; otherwise, a much larger potential difference would be needed to produce a sufficiently large electric field in the vacuum gap between the wafer and chuck. Typically, the face of the chuck has a pattern of grooves in which about 10 torr pressure of helium gas is maintained. This gas provides cooling (thermal contact) between the wafer and the chuck. A pressure of 10 torr is equivalent to about 0.2 psi.

  10. Effect of the electrostatic surface potential on the oligomerization of full-length human recombinant prion protein at single-molecule level

    NASA Astrophysics Data System (ADS)

    Wang, Bin; Lou, Zhichao; Zhang, Haiqian; Xu, Bingqian

    2016-03-01

    The electrostatic surface potential (ESP) of prion oligomers has critical influences on the aggregating processes of the prion molecules. The atomic force microscopy (AFM) and structural simulation were combined to investigate the molecular basis of the full-length human recombinant prion oligomerization on mica surfaces. The high resolution non-intrusive AFM images showed that the prion oligomers formed different patterns on mica surfaces at different buffer pH values. The basic binding units for the large oligomers were determined to be prion momoners (Ms), dimers (Ds), and trimers (Ts). The forming of the D and T units happened through the binding of hydrophobic β-sheets of the M units. In contrast, the α-helices of these M, D, and T units were the binding areas for the formation of large oligomers. At pH 4.5, the binding units M, D, and T showed clear polarized ESP distributions on the surface domains, while at pH 7.0, they showed more evenly distributed ESPs. Based on the conformations of oligomers observed from AFM images, the D and T units were more abundantly on mica surface at pH 4.5 because the ESP re-distribution of M units helped to stabilize these larger oligomers. The amino acid side chains involved in the binding interfaces were stabilized by hydrogen bonds and electrostatic interactions. The detailed analysis of the charged side chains at pH 4.5 indicated that the polarized ESPs induced the aggregations among M, D, and T to form larger oligomers. Therefore, the hydrogen bonds and electrostatic interactions worked together to form the stabilized prion oligomers.

  11. Genipin-crosslinked fibrin hydrogels as a potential adhesive to augment intervertebral disc annulus repair.

    PubMed

    Schek, R M; Michalek, A J; Iatridis, J C

    2011-04-18

    Treatment of damaged intervertebral discs is a significant clinical problem and, despite advances in the repair and replacement of the nucleus pulposus, there are few effective strategies to restore defects in the annulus fibrosus. An annular repair material should meet three specifications: have a modulus similar to the native annulus tissue, support the growth of disc cells, and maintain adhesion to tissue under physiological strain levels. We hypothesized that a genipin crosslinked fibrin gel could meet these requirements. Our mechanical results showed that genipin crosslinked fibrin gels could be created with a modulus in the range of native annular tissue. We also demonstrated that this material is compatible with the in vitro growth of human disc cells, when genipin:fibrin ratios were 0.25:1 or less, although cell proliferation was slower and cell morphology more rounded than for fibrin alone. Finally, lap tests were performed to evaluate adhesion between fibrin gels and pieces of annular tissue. Specimens created without genipin had poor handling properties and readily delaminated, while genipin crosslinked fibrin gels remained adhered to the tissue pieces at strains exceeding physiological levels and failed at 15-30%. This study demonstrated that genipin crosslinked fibrin gels show promise as a gap-filling adhesive biomaterial with tunable material properties, yet the slow cell proliferation suggests this biomaterial may be best suited as a sealant for small annulus fibrosus defects or as an adhesive to augment large annulus repairs. Future studies will evaluate degradation rate, fatigue behaviors, and long-term biocompatibility.

  12. Computational chemistry study of 3D-structure-function relationships for enzymes based on Markov models for protein electrostatic, HINT, and van der Waals potentials.

    PubMed

    Concu, Riccardo; Podda, Gianni; Uriarte, Eugenio; González-Díaz, Humberto

    2009-07-15

    In a significant work, Dobson and Doig (J Mol Biol 2003, 330, 771) illustrated protein prediction as enzymatic or not from spatial structure without resorting to alignments. They used 52 protein features and a nonlinear support vector machine model to classify more than 1000 proteins collected from the PDB with a 77% overall accuracy. The most useful features were: the secondary-structure content, the amino acid frequencies, the number of disulphide bonds, and the largest cleft size. Working on the same dataset used by D&D, in this article we reported a good and simple model, based on the Markov chain models (MCM), to classify protein 3D structures as enzymatic or not, taking into consideration the spatial structure without resorting to alignments. Here we define, for the first time, a general MCM to calculate the electrostatic potential, molecular vibrations, van der Waals (vdw) interactions, and hydrophobic interactions (HINT) and use them in comparative studies of potential fields and/or protein function prediction. The dataset is composed of 1371 proteins divided into 689 enzymes and 682 nonenzymes, all proteins were collected from the PDB. The best model we found was a linear model carried out with the linear discriminant analysis; it was able to classify 74.18% of the proteins using only two electrostatic potentials. In the work described here, we define 3D-HINT potentials (mu(k)) and use them for the first time to derive a classifier for protein enzymes. We analyzed ROC curves, domain of applicability, parametric assumptions, desirability maps, and also tested other nonlinear artificial neural network models which did not improve the linear model. In closing, this MCM allows a fast calculation and comparison of different potentials deriving into accurate protein 3D structure-function relationships, notably simpler than the previous.

  13. Adhesion of oil to kaolinite in water.

    PubMed

    Lebedeva, Evgenia V; Fogden, Andrew

    2010-12-15

    Uniform coats of kaolinite particles on a flat glass substrate were prepared to be sufficiently smooth and thin to allow reliable measurement of contact angles of captive crude oil drops in a range of salt solutions, without any particle removal. The contact angle hysteresis was used to infer the extent of oil adhesion via rupture of the intervening water film and anchoring of charged groups to kaolinite. For sodium chloride solutions, adhesion decreases monotonically with pH and/or salinity, with strong adhesion only manifested under acidic conditions with salinity at most 0.1 M. Calcium chloride solutions at pH around 6 switch from strong adhesion in the range 0.001-0.01 M to weak adhesion at higher concentrations. For all mixtures of sodium and calcium chlorides investigated, a total ionic strength above 0.1 M guarantees a weak adhesion of oil to kaolinite. Results are qualitatively consistent with theoretical expectations of electrostatic interactions, with H(+) and Ca(2+) being potential-determining ions for both interfaces.

  14. Spectroscopy (FT-IR, FT-Raman), hydrogen bonding, electrostatic potential and HOMO-LUMO analysis of tioxolone based on DFT calculations

    NASA Astrophysics Data System (ADS)

    Tao, Yaping; Li, Xiaofeng; Han, Ligang; Zhang, Weiying; Liu, Zhaojun

    2016-10-01

    Tioxolone possess antipsoriatic and antibacterial properties. Therefore, it has been used in treating various skin and scalp disorders for many years. Spectroscopic analysis of tioxolone was presented by using density functional theory (DFT) calculations and experiments (FT-IR, FT-Raman and UV-Vis). Molecular geometry and vibrational wavenumbers of tioxolone were investigated by using B3LYP method with aug-cc-pVTZ basis set. A complete vibrational spectra was made to analyze the potential energy distributions (PED). In addition, analysis of frontier molecular orbitals, electrostatic potential (ESP) and thermodynamic properties (heat capacity, entropy, enthalpy and Gibbs free energy) was presented with the same basis-set. Furthermore, the nature of molecular association through hydrogen bonding were discussed using atoms in molecules (AIM) and reduced density gradient (RDG) methods.

  15. Determination of the electrostatic potential distribution in Pt/Fe:SrTiO₃/Nb:SrTiO₃ thin-film structures by electron holography.

    PubMed

    Marchewka, Astrid; Cooper, David; Lenser, Christian; Menzel, Stephan; Du, Hongchu; Dittmann, Regina; Dunin-Borkowski, Rafal E; Waser, Rainer

    2014-11-10

    We determined the electrostatic potential distribution in pristine Pt/Fe:SrTiO3/Nb:SrTiO3 structures by electron holography experiments, revealing the existence of a depletion layer extending into the Nb-doped bottom electrode. Simulations of potential profiles in metal-insulator-metal structures were conducted assuming different types and distributions of dopants. It is found that the presence of acceptor-type dopant concentrations at the Fe:SrTiO3/Nb:SrTiO3 interface with a donor-doped insulating layer provides a good match to the measured profile. Such acceptor-type interface concentrations may be associated with Sr vacancies on the Nb:SrTiO3 side of the bottom interface.

  16. TSOL18/HP6-Tsol, an immunogenic Taenia solium oncospheral adhesion protein and potential protective antigen.

    PubMed

    Parkhouse, R Michael E; Bonay, Pedro; González, Luis Miguel; Ferrer, Elizabeth; Gárate, Teresa; Aguilar, Cruz M; Cortez A, Milagros M; Harrison, Leslie J S

    2008-04-01

    In this study, we employed Taenia solium mRNA extracted from a tapeworm of Venezuelan origin to clone express and test the recombinant protein of the T. solium homologue of the 18-kDa oncospheral adhesion molecule of Taenia saginata (HP6-Tsag/TSA18). We first confirm the conserved nature of the sequence of the T. solium homologue (TSOL18/HP6-Tsol) and demonstrate that the recombinant protein, which, as with its T. saginata homologue, is characterised by a fibronectin type III homology region, functions as an adhesion molecule. This emphasises the possible importance of TSOL18/HP6-Tsol in tissue invasion, thus providing a rational explanation for its efficacy as a vaccine. As protection against Taenia spp., oncospheres is antibody mediated, logically, therefore, TSOL18/HP6-Tsol may also serve as a diagnostic antigen, as is indeed the case for recombinant HP6-Tsag/TSA18.

  17. GENIPIN-CROSSLINKED FIBRIN HYDROGELS AS A POTENTIAL ADHESIVE TO AUGMENT INTERVERTEBRAL DISC ANNULUS REPAIR

    PubMed Central

    Schek, R.M.; Michalek, A.J.; Iatridis, J.C.

    2011-01-01

    Treatment of damaged intervertebral discs is a significant clinical problem and, despite advances in the repair and replacement of the nucleus pulposus, there are few effective strategies to restore defects in the annulus fibrosus. An annular repair material should meet three specifications: have a modulus similar to the native annulus tissue, support the growth of disc cells, and maintain adhesion to tissue under physiological strain levels. We hypothesized that a genipin crosslinked fibrin gel could meet these requirements. Our mechanical results showed that genipin crosslinked fibrin gels could be created with a modulus in the range of native annular tissue. We also demonstrated that this material is compatible with the in vitro growth of human disc cells, when genipin:fibrin ratios were 0.25:1 or less, although cell proliferation was slower and cell morphology more rounded than for fibrin alone. Finally, lap tests were performed to evaluate adhesion between fibrin gels and pieces of annular tissue. Specimens created without genipin had poor handling properties and readily delaminated, while genipin crosslinked fibrin gels remained adhered to the tissue pieces at strains exceeding physiological levels and failed at 15–30%. This study demonstrated that genipin crosslinked fibrin gels show promise as a gap-filling adhesive biomaterial with tunable material properties, yet the slow cell proliferation suggests this biomaterial may be best suited as a sealant for small annulus fibrosus defects or as an adhesive to augment large annulus repairs. Future studies will evaluate degradation rate, fatigue behaviors, and long-term biocompatibility. PMID:21503869

  18. Development of Electrostatically Clean Solar Array Panels

    NASA Technical Reports Server (NTRS)

    Stern, Theodore G.

    2000-01-01

    Certain missions require Electrostatically Clean Solar Array (ECSA) panels to establish a favorable environment for the operation of sensitive scientific instruments. The objective of this program was to demonstrate the feasibility of an ECSA panel that minimizes panel surface potential below 100mV in LEO and GEO charged particle environments, prevents exposure of solar cell voltage and panel insulating surfaces to the ambient environment, and provides an equipotential, grounded structure surrounding the entire panel. An ECSA panel design was developed that uses a Front Side Aperture-Shield (FSA) that covers all inter-cell areas with a single graphite composite laminate, composite edge clips for connecting the FSA to the panel substrate, and built-in tabs that interconnect the FSA to conductive coated coverglasses using a conductive adhesive. Analysis indicated the ability of the design to meet the ECSA requirements. Qualification coupons and a 0.5m x 0.5m prototype panel were fabricated and tested for photovoltaic performance and electrical grounding before and after exposure to acoustic and thermal cycling environments. The results show the feasibility of achieving electrostatic cleanliness with a small penalty in mass, photovoltaic performance and cost, with a design is structurally robust and compatible with a wide range of current solar panel technologies.

  19. Adhesion of perfume-filled microcapsules to model fabric surfaces.

    PubMed

    He, Yanping; Bowen, James; Andrews, James W; Liu, Min; Smets, Johan; Zhang, Zhibing

    2014-01-01

    The retention and adhesion of melamine formaldehyde (MF) microcapsules on a model fabric surface in aqueous solution were investigated using a customised flow chamber technique and atomic force microscopy (AFM). A cellulose film was employed as a model fabric surface. Modification of the cellulose with chitosan was found to increase the retention and adhesion of microcapsules on the model fabric surface. The AFM force-displacement data reveal that bridging forces resulting from the extension of cellulose chains dominate the adhesion between the microcapsule and the unmodified cellulose film, whereas electrostatic attraction helps the microcapsules adhere to the chitosan-modified cellulose film. The correlation between results obtained using these two complementary techniques suggests that the flow chamber device can be potentially used for rapid screening of the effect of chemical modification on the adhesion of microparticles to surfaces, reducing the time required to achieve an optimal formulation.

  20. On the potential for fibronectin/phosphorylcholine coatings on PTFE substrates to jointly modulate endothelial cell adhesion and hemocompatibility properties

    PubMed Central

    Montaño-Machado, Vanessa; Chevallier, Pascale; Mantovani, Diego; Pauthe, Emmanuel

    2015-01-01

    The use of biomolecules as coatings on biomaterials is recognized to constitute a promising approach to modulate the biological response of the host. In this work, we propose a coating composed by 2 biomolecules susceptible to provide complementary properties for cardiovascular applications: fibronectin (FN) to enhance endothelialization, and phosphorylcholine (PRC) for its non thrombogenic properties. Polytetrafluoroethylene (PTFE) was selected as model substrate mainly because it is largely used in cardiovascular applications. Two approaches were investigated: 1) a sequential adsorption of the 2 biomolecules and 2) an adsorption of the protein followed by the grafting of phosphorylcholine via chemical activation. All coatings were characterized by immunofluorescence staining, X-Ray Photoelectron Spectroscopy and Scanning Electron Microscopy analyses. Assays with endothelial cells showed improvement on cell adhesion, spreading and metabolic activity on FN-PRC coatings compared with the uncoated PTFE. Platelets adhesion and activation were both reduced on the coated surfaces when compared with uncoated PTFE. Moreover, clotting time tests exhibited better hemocompatibility properties of the surfaces after a sequential adsorption of FN and PRC. In conclusion, FN-PRC coating improves cell adhesion and non-thrombogenic properties, thus revealing a certain potential for the development of this combined deposition strategy in cardiovascular applications. PMID:25785369

  1. On the potential for fibronectin/phosphorylcholine coatings on PTFE substrates to jointly modulate endothelial cell adhesion and hemocompatibility properties.

    PubMed

    Montaño-Machado, Vanessa; Chevallier, Pascale; Mantovani, Diego; Pauthe, Emmanuel

    2015-01-01

    The use of biomolecules as coatings on biomaterials is recognized to constitute a promising approach to modulate the biological response of the host. In this work, we propose a coating composed by 2 biomolecules susceptible to provide complementary properties for cardiovascular applications: fibronectin (FN) to enhance endothelialization, and phosphorylcholine (PRC) for its non thrombogenic properties. Polytetrafluoroethylene (PTFE) was selected as model substrate mainly because it is largely used in cardiovascular applications. Two approaches were investigated: 1) a sequential adsorption of the 2 biomolecules and 2) an adsorption of the protein followed by the grafting of phosphorylcholine via chemical activation. All coatings were characterized by immunofluorescence staining, X-Ray Photoelectron Spectroscopy and Scanning Electron Microscopy analyses. Assays with endothelial cells showed improvement on cell adhesion, spreading and metabolic activity on FN-PRC coatings compared with the uncoated PTFE. Platelets adhesion and activation were both reduced on the coated surfaces when compared with uncoated PTFE. Moreover, clotting time tests exhibited better hemocompatibility properties of the surfaces after a sequential adsorption of FN and PRC. In conclusion, FN-PRC coating improves cell adhesion and non-thrombogenic properties, thus revealing a certain potential for the development of this combined deposition strategy in cardiovascular applications.

  2. Some molecular/crystalline factors that affect the sensitivities of energetic materials: molecular surface electrostatic potentials, lattice free space and maximum heat of detonation per unit volume.

    PubMed

    Politzer, Peter; Murray, Jane S

    2015-02-01

    We discuss three molecular/crystalline properties that we believe to be among the factors that influence the impact/shock sensitivities of energetic materials (i.e., their vulnerabilities to unintended detonation due to impact or shock). These properties are (a) the anomalously strong positive electrostatic potentials in the central regions of their molecular surfaces, (b) the free space per molecule in their crystal lattices, and (c) their maximum heats of detonation per unit volume. Overall, sensitivity tends to become greater as these properties increase; however these are general trends, not correlations. Nitramines are exceptions in that their sensitivities show little or no variation with free space in the lattice and heat of detonation per unit volume. We outline some of the events involved in detonation initiation and show how the three properties are related to different ones of these events.

  3. InfiniCharges: A tool for generating partial charges via the simultaneous fit of multiframe electrostatic potential (ESP) and total dipole fluctuations (TDF)

    NASA Astrophysics Data System (ADS)

    Sant, Marco; Gabrieli, Andrea; Demontis, Pierfranco; Suffritti, Giuseppe B.

    2016-03-01

    The InfiniCharges computer program, for generating reliable partial charges for molecular simulations in periodic systems, is here presented. This tool is an efficient implementation of the recently developed DM-REPEAT method, where the stability of the resulting charges, over a large set of fitting regions, is obtained through the simultaneous fit of multiple electrostatic potential (ESP) configurations together with the total dipole fluctuations (TDF). Besides DM-REPEAT, the program can also perform standard REPEAT fit and its multiframe extension (M-REPEAT), with the possibility to restrain the charges to an arbitrary value. Finally, the code is employed to generate partial charges for ZIF-90, a microporous material of the metal organic frameworks (MOFs) family, and an extensive analysis of the results is carried out.

  4. eF-seek: prediction of the functional sites of proteins by searching for similar electrostatic potential and molecular surface shape

    PubMed Central

    Kinoshita, Kengo; Murakami, Yoichi; Nakamura, Haruki

    2007-01-01

    We have developed a method to predict ligand-binding sites in a new protein structure by searching for similar binding sites in the Protein Data Bank (PDB). The similarities are measured according to the shapes of the molecular surfaces and their electrostatic potentials. A new web server, eF-seek, provides an interface to our search method. It simply requires a coordinate file in the PDB format, and generates a prediction result as a virtual complex structure, with the putative ligands in a PDB format file as the output. In addition, the predicted interacting interface is displayed to facilitate the examination of the virtual complex structure on our own applet viewer with the web browser (URL: http://eF-site.hgc.jp/eF-seek). PMID:17567616

  5. Receptor site topographies for phencyclidine-like and sigma drugs: predictions from quantitative conformational, electrostatic potential, and radioreceptor analyses.

    PubMed

    Manallack, D T; Wong, M G; Costa, M; Andrews, P R; Beart, P M

    1988-12-01

    Computer-assisted molecular modelling techniques and electrostatic analyses of a wide range of phenycyclidine (PCP) and sigma ligands, in conjunction with radioreceptor studies, were used to determine the topographies of the PCP and sigma receptors. The PCP receptor model was defined using key molecules from the arylcyclohexylamine, benzomorphan, bridged benz[f]isoquinoline, and dibenzocycloalkenimine drug classes. Hypothetical receptor points (R1, R2) were constructed onto the aromatic ring of each compound to represent hydrophobic interactions with the receptor, along with an additional receptor point (R3) representing a hydrogen bond between the nitrogen atom and the receptor. The superimposition of these key molecules gave the coordinates of the receptor points and nitrogen defining the primary PCP pharmacophore as follows: R1 (0.00, 3.50, 0.00), R2 (0.00, -3.50, 0.00), R3 (6.66, -1.13, 0.00), and N (3.90, -1.46, -0.32). Additional analyses were used to describe secondary binding sites for an additional hydrogen bonding site and two lipophilic clefts. Similarly, the sigma receptor model was constructed from ligands of the benzomorphan, octahydrobenzo[f]quinoline, phenylpiperidine, and diphenylguanidine drug classes. Coordinates for the primary sigma pharmacophore are as follows: R1 (0.00, 3.50, 0.00), R2 (0.00, -3.50, 0.00), R3 (6.09, 2.09, 0.00), and N (4.9, -0.12, -1.25). Secondary binding sites for sigma ligands were proposed for the interaction of aromatic ring substituents and large N-substituted lipophilic groups with the receptor. The sigma receptor model differs from the PCP model in the position of nitrogen atom, direction of the nitrogen lone pair vector, and secondary sigma binding sites. This study has thus demonstrated that the differing quantitative structure-activity relationships of PCP and sigma ligands allow the definition of discrete receptors. These models may be used in conjunction with rational drug design techniques to design novel PCP

  6. Electrostatic Enhancement of Coagulation in Protoplanetary Nebulae

    NASA Technical Reports Server (NTRS)

    Marshall, J.; Cuzzi, J.

    2001-01-01

    Microgravity experiments suggest that electrostatic forces (overwhelmed by normal Earth gravity) could greatly enhance cohesive strength of preplanetary aggregates. Cohesive forces may be 103 times larger than those for van der Waals adhesion. Additional information is contained in the original extended abstract.

  7. The comparative tea staining potential of phenolic, chlorhexidine and anti-adhesive mouthrinses.

    PubMed

    Addy, M; Moran, J; Newcombe, R; Warren, P

    1995-12-01

    Staining of teeth and mucous membranes is a well-known side-effect with chlorhexidine mouthrinses in which dietary chromogens play an important rôle. The purpose of this study was to determine whether a co-polymer anti-adhesive agent would prevent staining by a low concentration chlorhexidine solution. Additionally, the possibility that an essential oil/phenolic rinse product may cause staining was investigated. The rinses studied were the anti-adhesive alone and combined with 0.02% chlorhexidine and the essential oil/phenolic rinse. These were positioned against a positive control rise, 0.2% chlorhexidine, and a negative control rinse, water. The study was a single blind 5-treatment, randomised Latin square cross-over design, incorporating balance for carry-over effects. 15 volunteers participated and on Day 1 of each study period were rendered stain free by scaling and polishing of the teeth. Oral hygiene was suspended and 8 x per day subjects rinsed under supervision, firstly with the allocated formulation and then with 10 ml of warm black tea. On Day 4, tooth and tongue staining was scored by area and intensity (colour). A washout period of at least 3 1/2 days was permitted between treatment periods when oral hygiene was resumed. Before the study and during washouts, volunteers practised tongue brushing. Tooth and tongue staining was significantly increased with 0.2% chlorhexidine compared to the essential oil/phenolic rinse which in turn was significantly increased compared to the other 3 rinses. The antiadhesive/chlorhexidine rinse produced no more staining than the anti-adhesive or water rise. However, the parallel plaque regrowth study suggests this inhibition of staining resulted from the vitiation of the chlorhexidine activity by the antiadhesive. The methodology would appear a simple and quick way of assessing the propensity of mouthrinses to cause extrinsic staining.

  8. Electrostatic Return of Contaminants

    NASA Technical Reports Server (NTRS)

    Rantanen, R.; Gordon, T.

    2003-01-01

    A Model has been developed capable of calculating the electrostatic return of spacecraft-emitted molecules that are ionized and attracted back to the spacecraft by the spacecraft electric potential on its surfaces. The return of ionized contaminant molecules to charged spacecraft surfaces is very important to all altitudes. It is especially important at geosynchronous and interplanetary environments, since it may be the only mechanism by which contaminants can degrade a surface. This model is applicable to all altitudes and spacecraft geometries. In addition to results of the model will be completed to cover a wide range of potential space systems.

  9. Comparative analysis of the electrostatic potentials of some structural analogues of 2,3,7,8-tetrachlorodibenzo-p-dioxin and of related aromatic systems

    SciTech Connect

    Murray, J.S.; Evans, P.; Politzer, P.

    1990-01-01

    An ab initio STO-5G computational analysis of the electrostatic potentials of four structural analogs of the highly toxic 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and four related aromatic systems (benzo(a)pyrene, benz(a)anthracene and two isomeric benzoflavones) was carried out. The systems, to varying degrees, induce aryl hydrocarbon hydroxylase activity and are believed to interact with the same cytosolic receptor in initiating their biochemical responses. It was found that a high degree of activity appears to require negative potentials that are non-overlapping above all or most of the lateral regions, with an observed optimum range of magnitudes. In systems with central oxygens, it is required that the negative oxygen potentials be small and weak; however, oxygen negative regions in the molecule are not necessary for high activity. The observed differences between the potential patterns of the four aromatic systems and those of TCDD and its active analogs may reflect an inherent dissimilarity in the nature of their interactions with the cytosolic receptor.

  10. Electrostatic modulation of periodic potentials in a two-dimensional electron gas: From antidot lattice to quantum dot lattice

    SciTech Connect

    Goswami, Srijit; Aamir, Mohammed Ali; Shamim, Saquib; Ghosh, Arindam; Siegert, Christoph; Farrer, Ian; Ritchie, David A.; Pepper, Michael

    2013-12-04

    We use a dual gated device structure to introduce a gate-tuneable periodic potential in a GaAs/AlGaAs two dimensional electron gas (2DEG). Using only a suitable choice of gate voltages we can controllably alter the potential landscape of the bare 2DEG, inducing either a periodic array of antidots or quantum dots. Antidots are artificial scattering centers, and therefore allow for a study of electron dynamics. In particular, we show that the thermovoltage of an antidot lattice is particularly sensitive to the relative positions of the Fermi level and the antidot potential. A quantum dot lattice, on the other hand, provides the opportunity to study correlated electron physics. We find that its current-voltage characteristics display a voltage threshold, as well as a power law scaling, indicative of collective Coulomb blockade in a disordered background.

  11. Electrostatic interaction of neutral semi-permeable membranes

    NASA Astrophysics Data System (ADS)

    Vinogradova, Olga I.; Bocquet, Lyderic; Bogdanov, Artem N.; Tsekov, Roumen; Lobaskin, Vladimir

    2012-01-01

    We consider an osmotic equilibrium between bulk solutions of polyelectrolyte bounded by semi-permeable membranes and separated by a thin film of salt-free liquid. Although the membranes are neutral, the counter-ions of the polyelectrolyte molecules permeate into the gap and lead to a steric charge separation. This gives rise to a distance-dependent membrane potential, which translates into a repulsive electrostatic disjoining pressure. From the solution of the nonlinear Poisson-Boltzmann equation, we obtain the distribution of the potential and of ions. We then derive an explicit formula for the pressure exerted on the membranes and show that it deviates from the classical van't Hoff expression for the osmotic pressure. This difference is interpreted in terms of a repulsive electrostatic disjoining pressure originating from the overlap of counterion clouds inside the gap. We also develop a simplified theory based on a linearized Poisson-Boltzmann approach. A comparison with simulation of a primitive model for the electrolyte is provided and does confirm the validity of the theoretical predictions. Beyond the fundamental result that the neutral surfaces can repel, this mechanism not only helps to control the adhesion and long-range interactions of living cells, bacteria, and vesicles, but also allows us to argue that electrostatic interactions should play enormous role in determining behavior and functions of systems bounded by semi-permeable membranes.

  12. α6-Integrin is required for the adhesion and vasculogenic potential of hemangioma stem cells.

    PubMed

    Smadja, David M; Guerin, Coralie L; Boscolo, Elisa; Bieche, Ivan; Mulliken, John B; Bischoff, Joyce

    2014-03-01

    Infantile hemangioma (IH) is the most common tumor of infancy. Hemangioma stem cells (HemSC) are a mesenchymal subpopulation isolated from IH CD133+ cells. HemSC can differentiate into endothelial and pericyte/smooth muscle cells and form vascular networks when injected in immune-deficient mice. α6-Integrin subunit has been implicated in the tumorgenicity of glioblastoma stem cells and the homing properties of hematopoietic, endothelial, and mesenchymal progenitor cells. Therefore, we investigated the possible function(s) of α6-integrin in HemSC. We documented α6-integrin expression in IH tumor specimens and HemSC by RT-qPCR and flow cytometry. We examined the effect of blocking or silencing α6-integrin on the adhesive and proliferative properties of HemSC in vitro and the vasculogenic and homing properties of HemSC in vivo. Targeting α6-integrin in cultured HemSC inhibited adhesion to laminin but had no effect on proliferation. Vessel-forming ability in Matrigel implants and hepatic homing after i.v. delivery were significantly decreased in α6-integrin siRNA-transfected HemSC. In conclusion, α6-integrin is required for HemSC adherence to laminin, vessel formation in vivo, and for homing to the liver. Thus, we uncovered an important role for α6 integrin in the vasculogenic properties of HemSC. Our results suggest that α6-integrin expression on HemSC could be a new target for antihemangioma therapy.

  13. Soluble vascular cell adhesion molecular-1 is a potential biological indicator of hemophilic arthropathy

    PubMed Central

    Tseng, Yu-Hsin; Chiou, Shyh-Shin; Zeng, Yu-Sheng; Tsai, Shih-Pien; Chen, Chun-Shih; Liao, Yu-Mei; Lin, Pei-Chin

    2016-01-01

    Abstract Hemophilic arthropathy is the most common chronic complication in patients with hemophilia. The pathogenesis of hemophilic arthropathy involves the inflammatory processes associated with rheumatoid arthritis (RA). Determining the severity and/or progression of joint damage is crucial when evaluating the effect of treatment modalities. Identifying reliable biomarkers in the peripheral blood of patients with hemophilic arthropathy may be beneficial in clinical practice. Circulating soluble vascular cell adhesion molecule-1 (sVCAM-1), E-selectin, and P-selectin levels are elevated in patients with RA. Our study investigated whether these soluble adhesion molecules can be used as biological indicators in the course of joint damage in patients with hemophilia A. Patients with hemophilia A (mild, moderate, and severe) were enrolled. The plasma levels of sVCAM-1, E-selectin, and P-selectin in patients with hemophilia A and control were measured using specific enzyme-linked immunosorbent assay kits. Joint damages were evaluated using Pettersson scores. No statistically significant differences were observed in E-selectin and P-selectin levels between patients and controls. The sVCAM-1 level was significantly higher in patients with hemophilia A than in controls. The differences remained significant in patients with severe hemophilia A but not in patients with mild or moderate hemophilia A. The degree of hemophilic arthropathy was evaluated using Pettersson scores, and a score higher than 5 indicated marked arthropathy. Patients with more than 1 joint with marked arthropathy showed significantly higher sVCAM-1 levels. sVCAM-1 levels in patients with hemophilia A are associated with the severity of hemophilic arthropathy. PMID:27861372

  14. Nonlinear response of the surface electrostatic potential formed at metal oxide/electrolyte interfaces. A Monte Carlo simulation study

    SciTech Connect

    Zarzycki, Piotr P.; Rosso, Kevin M.

    2010-01-01

    An analysis of surface potential nonlinearity at metal oxide/electrolyte interfaces is presented. By using Grand Canonical Monte Carlo simulations of a simple lattice model of an interface, we show a correlation exists between ionic strength as well as surface site densities and the non-Nernstian response of a metal oxide electrode. We propose two approaches to deal with the 0-nonlinearity: one based on perturbative expansion of the Gibbs free energy and another based on assumption of the pH-dependence of surface potential slope. The theoretical anal ysis based on our new potential form gives excellent performance at extreme pH regions, where classical formulae based on the Poisson-Boltzmann equation fail. The new formula is general and independent of any underlying assumptions. For this reason, it can be directly applied to experimental surface potential measurements, including those for individual surfaces of single crystals, as we present for data reported by Kallay and Preocanin [Kallay, Preocanin J. Colloid and Interface20 Sci. 318 (2008) 290].

  15. Computer-generated formulas for three-center nuclear-attraction integrals (electrostatic potential) for Slater-type orbitals

    NASA Technical Reports Server (NTRS)

    Jones, H. W.

    1984-01-01

    The computer-assisted C-matrix, Loewdin-alpha-function, single-center expansion method in spherical harmonics has been applied to the three-center nuclear-attraction integral (potential due to the product of separated Slater-type orbitals). Exact formulas are produced for 13 terms of an infinite series that permits evaluation to ten decimal digits of an example using 1s orbitals.

  16. Micromachined, Electrostatically Deformable Reflectors

    NASA Technical Reports Server (NTRS)

    Bartman, Randall K.; Wang, Paul K. C.; Miller, Linda M.; Kenny, Thomas W.; Kaiser, William J.; Hadaegh, Fred Y.; Agronin, Michael L.

    1995-01-01

    Micromachined, closed-loop, electrostatically actuated reflectors (microCLEARs) provide relatively simple and inexpensive alternatives to large, complex, expensive adaptive optics used to control wavefronts of beams of light in astronomy and in experimental laser weapons. Micromachining used to make deformable mirror, supporting structure, and actuation circuitry. Development of microCLEARs may not only overcome some of disadvantages and limitations of older adaptive optics but may also satisfy demands of potential market for small, inexpensive deformable mirrors in electronically controlled film cameras, video cameras, and other commercial optoelectronic instruments.

  17. Platelet activation, adhesion, inflammation, and aggregation potential are altered in the presence of electronic cigarette extracts of variable nicotine concentrations.

    PubMed

    Hom, Sarah; Chen, Li; Wang, Tony; Ghebrehiwet, Berhane; Yin, Wei; Rubenstein, David A

    2016-11-01

    Tobacco smoke extracts prepared from both mainstream and sidestream smoking have been associated with heightened platelet activation, aggregation, adhesion, and inflammation. Conversely, it has been shown that pure nicotine inhibits similar platelet functions. In this work, we 1) evaluated the effects of e-cigarette extracts on platelet activities and 2) elucidated the differences between the nicotine-dependent and non-nicotine dependent (e.g. fine particulate matter or toxic compounds) effects of tobacco and e-cigarette products on platelet activities. To accomplish these goals, platelets from healthy volunteers (n = 50) were exposed to tobacco smoke extracts, e-cigarette vapor extracts, and pure nicotine and changes in platelet activation, adhesion, aggregation, and inflammation were evaluated, using optical aggregation, flow cytometry, and ELISA methods. Interestingly, the exposure of platelets to e-vapor extracts induced a significant up-regulation in the expression of the pro-inflammatory gC1qR and cC1qR and induced a marked increase in the deposition of C3b as compared with traditional tobacco smoke extracts. Similarly, platelet activation, as measured by a prothrombinase based assay, and platelet aggregation were also significantly enhanced after exposure to e-vapor extracts. Finally, platelet adhesion potential toward fibrinogen, von Willebrand factor, and other platelets was also enhanced after exposure to e-cigarette vapor extracts. In the presence of pure nicotine, platelet functions were observed to be inhibited, which further suggests that other constituents of tobacco smoke and electronic vapor can antagonize platelet functions, however, the presence of nicotine in extracts somewhat perpetuated the platelet functional changes in a dose-dependent manner.

  18. Synthesis, vibrational, electrostatic potential and NMR studies of (E and Z) 1-(4-chloro-3-nitrophenyl)-3-(2-methoxyphenyl)triazene: Combined experimental and DFT approaches

    NASA Astrophysics Data System (ADS)

    Rofouei, Mohammad Kazem; Soleymani, Reza; Aghaei, Abolfazl; Mirzaei, Mahmoud

    2016-12-01

    Using new experimental methods, 1-(4-chloro-3-nitrophenyl)-3-(2-methoxyphenyl) triazene, (CNPMPT) structure was synthesized in the laboratory. The structure has two E and Z conformational states that E is a more stable state than the Z. After synthesis of the structure, crystallization process was carried out and its chemical properties were investigated using experimental and theoretical methods. The structure has orthorhombic crystal system with space group equal to Pbca and its unit cell parameters comprise a = 7.0723 (9), b = 7.5333 (9), and c = 13.7138 (15). To further study and identify the structure, in addition to X-Ray diffraction, NMR and FT-IR analyses were also done on the structure. Then, the structure was discussed and studied using density functional theory (DFT) at the theory level B3LYP, B3PW91 and PBEPBE. The structural and thermodynamic parameters, electrostatic potential, corresponding Hirshfield surface, electrophilicity (ω), chemical potential (μ), chemical hardness (η) and max amount of electronic charge transfer (ΔNmax) were examined for this structure. The results showed that the experimental and theoretical results were very consistent.

  19. Search for Effects of an Electrostatic Potential on Clocks in the Frame of Reference of a Charged Particle

    NASA Technical Reports Server (NTRS)

    Ringermacher, Harry I.; Conradi, Mark S.; Cassenti, Brice

    2005-01-01

    Results of experiments to confirm a theory that links classical electromagnetism with the geometry of spacetime are described. The theory, based on the introduction of a Torsion tensor into Einstein s equations and following the approach of Schroedinger, predicts effects on clocks attached to charged particles, subject to intense electric fields, analogous to the effects on clocks in a gravitational field. We show that in order to interpret this theory, one must re-interpret all clock changes, both gravitational and electromagnetic, as arising from changes in potential energy and not merely potential. The clock is provided naturally by proton spins in hydrogen atoms subject to Nuclear Magnetic Resonance trials. No frequency change of clocks was observed to a resolution of 6310(exp -9). A new "Clock Principle" was postulated to explain the null result. There are two possible implications of the experiments: (a) The Clock Principle is invalid and, in fact, no metric theory incorporating electromagnetism is possible; (b) The Clock Principle is valid and it follows that a negative rest mass cannot exist.

  20. Phosphoproteomic Analysis Identifies Focal Adhesion Kinase 2 (FAK2) as a Potential Therapeutic Target for Tamoxifen Resistance in Breast Cancer.

    PubMed

    Wu, Xinyan; Zahari, Muhammad Saddiq; Renuse, Santosh; Nirujogi, Raja Sekhar; Kim, Min-Sik; Manda, Srikanth S; Stearns, Vered; Gabrielson, Edward; Sukumar, Saraswati; Pandey, Akhilesh

    2015-11-01

    Tamoxifen, an estrogen receptor-α (ER) antagonist, is an important agent for the treatment of breast cancer. However, this therapy is complicated by the fact that a substantial number of patients exhibit either de novo or acquired resistance. To characterize the signaling mechanisms underlying this resistance, we treated the MCF7 breast cancer cell line with tamoxifen for over six months and showed that this cell line acquired resistance to tamoxifen in vitro and in vivo. We performed SILAC-based quantitative phosphoproteomic profiling on the tamoxifen resistant and vehicle-treated sensitive cell lines to quantify the phosphorylation alterations associated with tamoxifen resistance. From >5600 unique phosphopeptides identified, 1529 peptides exhibited hyperphosphorylation and 409 peptides showed hypophosphorylation in the tamoxifen resistant cells. Gene set enrichment analysis revealed that focal adhesion pathway was one of the most enriched signaling pathways activated in tamoxifen resistant cells. Significantly, we showed that the focal adhesion kinase FAK2 was not only hyperphosphorylated but also transcriptionally up-regulated in tamoxifen resistant cells. FAK2 suppression by specific siRNA knockdown or a small molecule inhibitor repressed cellular proliferation in vitro and tumor formation in vivo. More importantly, our survival analysis revealed that high expression of FAK2 is significantly associated with shorter metastasis-free survival in estrogen receptor-positive breast cancer patients treated with tamoxifen. Our studies suggest that FAK2 is a potential therapeutic target for the management of hormone-refractory breast cancers.

  1. Differences in Electrostatic Potential Around DNA Fragments Containing Adenine and 8-oxo-Adenine. An Analysis Based on Regular Cylindrical Projection

    SciTech Connect

    Haranczyk, Maciej; Miller, John H; Gutowski, Maciej S

    2007-07-01

    Changes of electrostatic potential (EP) around the DNA molecule resulting from chemical modifications of nucleotides may play a role in enzymatic recognition of damaged sites. Effects of chemical modifications of nucleotides on the structure of DNA have been characterized through large scale density functional theory computations. Quantum mechanical structural optimizations of DNA fragments with three pairs of nucleotides and accompanying counteractions were performed with a B3LYP exchange-correlation functional and 6-31G** basis sets. The “intact” DNA fragment contained adenine in the middle layer, while the “damaged” fragment had the adenine replaced with 8-oxo-adenine. The electrostatic potential around these DNA fragments was projected on a cylindrical surface around the double helix. The two-dimensional maps of EP of the intact and damaged DNA fragments were analyzed to identify these modifications of EP that result from the occurrence of 8-oxo-adenine (8oA). It was found that distortions of a phosphate group neighboring 8oA and displacements of the accompanying countercation are clearly reflected in the EP maps. Helpful discussions Michel Dupuis are gratefully acknowledged. Authors wish to thank Marcel Swart for directing us to a compilation of van der Waals radii. This work was supported by the: (i) US DOE Office of Biological and Environmental Research, Low Dose Radiation Research Program (M.G. and M.H.), (ii) the Office of Science (BER), U. S. Department of Energy, Grant No. DE-FG03-02ER63470 (JHM), (iii) Polish State Committee for Scientific Research (KBN) Grant DS/8221-4-0140-6 (MG), (iv) European Social Funds (EFS) ZPORR/2.22/II/2.6/ARP/U/2/05 (M.H.). M.H. holds the Foundation for Polish Science (FNP) award for young scientists. The calculations were performed at the Academic Computer Center in Gdansk (TASK) and at the Molecular Science Computing Facility (MSCF) in the William R. Wiley Environmental Molecular Sciences Laboratory, a national

  2. Electrostatically screened, voltage-controlled electrostatic chuck

    DOEpatents

    Klebanoff, Leonard Elliott

    2001-01-01

    Employing an electrostatically screened, voltage-controlled electrostatic chuck particularly suited for holding wafers and masks in sub-atmospheric operations will significantly reduce the likelihood of contaminant deposition on the substrates. The electrostatic chuck includes (1) an insulator block having a outer perimeter and a planar surface adapted to support the substrate and comprising at least one electrode (typically a pair of electrodes that are embedded in the insulator block), (2) a source of voltage that is connected to the at least one electrode, (3) a support base to which the insulator block is attached, and (4) a primary electrostatic shield ring member that is positioned around the outer perimeter of the insulator block. The electrostatic chuck permits control of the voltage of the lithographic substrate; in addition, it provides electrostatic shielding of the stray electric fields issuing from the sides of the electrostatic chuck. The shielding effectively prevents electric fields from wrapping around to the upper or front surface of the substrate, thereby eliminating electrostatic particle deposition.

  3. Toward the description of electrostatic interactions between globular proteins: Potential of mean force in the primitive model

    NASA Astrophysics Data System (ADS)

    Dahirel, Vincent; Jardat, Marie; Dufrêche, Jean-François; Turq, Pierre

    2007-09-01

    Monte Carlo simulations are used to calculate the exact potential of mean force between charged globular proteins in aqueous solution. The aim of the present paper is to study the influence of the ions of the added salt on the effective interaction between these nanoparticles. The charges of the model proteins, either identical or opposite, are either central or distributed on a discrete pattern. Contrarily to Poisson-Boltzmann predictions, attractive, and repulsive direct forces between proteins are not screened similarly. Moreover, it has been shown that the relative orientations of the charge patterns strongly influence salt-mediated interactions. More precisely, for short distances between the proteins, ions enhance the difference of the effective forces between (i) like-charged and oppositely charged proteins, (ii) attractive and repulsive relative orientations of the proteins, which may affect the selectivity of protein/protein recognition. Finally, such results observed with the simplest models are applied to a more elaborate one to demonstrate their generality.

  4. Vibrational spectroscopic (FT-IR and FT-Raman) studies, natural bond orbital analysis and molecular electrostatic potential surface of 3-hydroxy-6-methyl-2-nitropyridine

    NASA Astrophysics Data System (ADS)

    Karnan, M.; Balachandran, V.; Murugan, M.

    2012-10-01

    The optimized molecular structure and corresponding vibrational assignments of 3-hydroxy-6-methyl-2-nitropyridine have been investigated using density functional theory (DFT) B3LYP method with 6-311++G(d,p), 6-311++G(2d,2p) and 6-311++G(3d,3p) basis sets. Investigation of the relative orientation of the hydroxyl group with respect to the nitro group has shown that two conformers (O-cis) and (O-trans) exist. The vibrational analysis of the stable conformer of the title compound is performed by means of infrared absorption and Raman spectroscopy in combination with theoretical simulations. The molecular stability and bond strength were investigated by applying the natural bond orbital (NBO) analysis. Information about the size, shape, charge density distribution and site of chemical reactivity of the molecule has been obtained by mapping electron density isosurface with electrostatic potential (ESP). The isotropic chemical shift computed by 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the HMNP calculated using the gauge invariant atomic orbital (GIAO) method also shows good agreement with experimental observations.

  5. Change of electrostatic potential of mean force between two curved surfaces due to different salt composition, ion valence and size under certain ionic strength

    NASA Astrophysics Data System (ADS)

    Zhou, Shiqi

    2016-02-01

    Change of an electrostatic potential of mean force (EPMF) between two cylindrical rod surfaces with salt composition, ion valence, and ion size at a constant ionic strength of 0.3 M is studied by a classical density functional theory (CDFT) in a primitive model electrolyte solution. Several novel observations are made: (i) strength of a so-called like charge attraction (LCA) reduces in an invariable manner with the salt solution changing from single 2:1 electrolyte to mixture of 2:1 and 1:1 type electrolytes of varying concentration ratios; the change is even over entire range of the composition variation under low surface charge strength, and tends to be insensitive to the composition variation in the presence of the divalent counter-ion, and more and more drastic at a critical point the divalent counter-ion disappears, respectively, as the surface charge strength becomes big enough. (ii) Both monovalent counter-ion and co-ion diameters have only a marginal effect on both the LCA strength and equilibrium distance, and the former "abnormally" affects less than the latter. (iii) Depending on the surface charge strength considered, the divalent counter-ion diameter influences the LCA strength in solution comprised of 2:1 type and 1:1 type electrolytes, monotonously or non-monotonously. All of these findings provide forceful support for a recently proposed hydrogen-bonding style mechanism explaining the LCA.

  6. Assessment of the potential utility of different regions of Streptococcus uberis adhesion molecule (SUAM) for mastitis subunit vaccine development.

    PubMed

    Perrig, Melina Soledad; Veaute, Carolina; Renna, María Sol; Pujato, Nazarena; Calvinho, Luis; Marcipar, Iván; Barbagelata, María Sol

    2017-03-01

    Streptococcus uberis is one of the most prevalent pathogens causing clinical and subclinical mastitis worldwide. Among bacterial factors involved in intramammary infections caused by this organism, S. uberis adhesion molecule (SUAM) is one of the main virulence factors identified. This molecule is involved in S. uberis internalization to mammary epithelial cells through lactoferrin (Lf) binding. The objective of this study was to evaluate SUAM properties as a potential subunit vaccine component for prevention of S. uberis mastitis. B epitope prediction analysis of SUAM sequence was used to identify potentially immunogenic regions. Since these regions were detected all along the gene, this criterion did not allow selecting a specific region as a potential immunogen. Hence, four fractions of SUAM (-1fr, 2fr, 3fr and 4fr), comprising most of the protein, were cloned and expressed. Every fraction elicited a humoral immune response in mice as predicted by bioinformatics analysis. SUAM-1fr generated antibodies with the highest recognition ability towards SUAM native protein. Moreover, antibodies against SUAM-1fr produced the highest proportion of internalization inhibition of S. uberis to mammary epithelial cells. In conclusion, SUAM immunogenic and functionally relevant regions were identified and allowed to propose SUAM-1fr as a potential candidate for a subunit vaccine for S. uberis mastitis prevention.

  7. Using Programmable Calculators to Solve Electrostatics Problems.

    ERIC Educational Resources Information Center

    Yerian, Stephen C.; Denker, Dennis A.

    1985-01-01

    Provides a simple routine which allows first-year physics students to use programmable calculators to solve otherwise complex electrostatic problems. These problems involve finding electrostatic potential and electric field on the axis of a uniformly charged ring. Modest programing skills are required of students. (DH)

  8. Versatile electrostatic trap

    SciTech Connect

    Veldhoven, Jacqueline van; Bethlem, Hendrick L.; Schnell, Melanie; Meijer, Gerard

    2006-06-15

    A four electrode electrostatic trap geometry is demonstrated that can be used to combine a dipole, quadrupole, and hexapole field. A cold packet of {sup 15}ND{sub 3} molecules is confined in both a purely quadrupolar and hexapolar trapping field and additionally, a dipole field is added to a hexapole field to create either a double-well or a donut-shaped trapping field. The profile of the {sup 15}ND{sub 3} packet in each of these four trapping potentials is measured, and the dependence of the well-separation and barrier height of the double-well and donut potential on the hexapole and dipole term are discussed.

  9. Electrostatics at the molecular level

    NASA Astrophysics Data System (ADS)

    Zürcher, Ulrich

    2017-01-01

    In molecular systems, positive and negative charges are separated, making them ideal systems to examine electrostatic interactions. The attractive force between positive and negative charges is balanced by repulsive ‘forces’ that are quantum-mechanical in origin. We introduce an ‘effective’ potential energy that captures the repulsion; it allows us to obtain fairly accurate estimates of the bonding properties of molecular systems. We use units (e.g., kcal mol-1 for energy) that emphasize the relevance of electrostatics to macroscopic behavior.

  10. Compact electrostatic comb actuator

    DOEpatents

    Rodgers, M. Steven; Burg, Michael S.; Jensen, Brian D.; Miller, Samuel L.; Barnes, Stephen M.

    2000-01-01

    A compact electrostatic comb actuator is disclosed for microelectromechanical (MEM) applications. The actuator is based upon a plurality of meshed electrostatic combs, some of which are stationary and others of which are moveable. One or more restoring springs are fabricated within an outline of the electrostatic combs (i.e. superposed with the moveable electrostatic combs) to considerably reduce the space required for the actuator. Additionally, a truss structure is provided to support the moveable electrostatic combs and prevent bending or distortion of these combs due to unbalanced electrostatic forces or external loading. The truss structure formed about the moveable electrostatic combs allows the spacing between the interdigitated fingers of the combs to be reduced to about one micron or less, thereby substantially increasing the number of active fingers which can be provided in a given area. Finally, electrostatic shields can be used in the actuator to substantially reduce unwanted electrostatic fields to further improve performance of the device. As a result, the compact electrostatic comb actuator of the present invention occupies only a fraction of the space required for conventional electrostatic comb actuators, while providing a substantial increase in the available drive force (up to one-hundred times).

  11. Nanoscale quantitative measurement of the potential of charged nanostructures by electrostatic and Kelvin probe force microscopy: unraveling electronic processes in complex materials.

    PubMed

    Liscio, Andrea; Palermo, Vincenzo; Samorì, Paolo

    2010-04-20

    In microelectronics and biology, many fundamental processes involve the exchange of charges between small objects, such as nanocrystals in photovoltaic blends or individual proteins in photosynthetic reactions. Because these nanoscale electronic processes strongly depend on the structure of the electroactive assemblies, a detailed understanding of these phenomena requires unraveling the relationship between the structure of the nano-object and its electronic function. Because of the fragility of the structures involved and the dynamic variance of the electric potential of each nanostructure during the charge generation and transport processes, understanding this structure-function relationship represents a great challenge. This Account discusses how our group and others have exploited scanning probe microscopy based approaches beyond imaging, particularly Kelvin probe force microscopy (KPFM), to map the potential of different nanostructures with a spatial and voltage resolution of a few nanometers and millivolts, respectively. We describe in detail how these techniques can provide researchers several types of chemical information. First, KPFM allows researchers to visualize the photogeneration and splitting of several unitary charges between well-defined nano-objects having complementary electron-acceptor and -donor properties. In addition, this method maps charge injection and transport in thin layers of polycrystalline materials. Finally, KPFM can monitor the activity of immobilized chemical components of natural photosynthetic systems. In particular, researchers can use KPFM to measure the electric potential without physical contact between the tip and the nanostructure studied. These measurements exploit long-range electrostatic interactions between the scanning probe and the sample, which scale with the square of the probe-sample distance, d. While allowing minimal perturbation, these long-range interactions limit the resolution attainable in the measurement

  12. PREFACE: Electrostatics 2015

    NASA Astrophysics Data System (ADS)

    Matthews, James

    2015-10-01

    Electrostatics 2015, supported by the Institute of Physics, was held in the Sir James Matthews building at Southampton Solent University, UK between 12th and 16th April 2015. Southampton is a historic city on the South Coast of England with a strong military and maritime history. Southampton is home to two Universities: Solent University, which hosted the conference, and the University of Southampton, where much work is undertaken related to electrostatics. 37 oral and 44 poster presentations were accepted for the conference, and 60 papers were submitted and accepted for the proceedings. The Bill Bright Memorial Lecture was delivered this year by Professor Mark Horenstein from Boston University who was, until recently, Editor-in-Chief of the Journal of Electrostatics. He spoke on The contribution of surface potential to diverse problems in electrostatics and his thorough knowledge of the subject of electrostatics was evident in the presentation. The first session was chaired by the Conference Chair, Dr Keith Davies, whose experience in the field showed through his frequent contributions to the discussions throughout the conference. Hazards and Electrostatic Discharge have formed a strong core to Electrostatics conferences for many years, and this conference contained sessions on both Hazards and on ESD, including an invited talk from Dr Jeremy Smallwood on ESD in Industry - Present and Future. Another strong theme to emerge from this year's programme was Non-Thermal Plasmas, which was covered in two sessions. There were two invited talks on this subject: Professor Masaaki Okubo gave a talk on Development of super-clean diesel engine and combustor using nonthermal plasma hybrid after treatment and Dr David Go presented a talk on Atmospheric-pressure ionization processes: New approaches and applications for plasmas in contact with liquids. A new innovation to the conference this year was the opportunity for conference sponsors to present to the delegates a technical

  13. Biocompatible Adhesives

    DTIC Science & Technology

    1991-03-01

    pressure sensitive elastomer, polyisobutylene. with water soluble adhesives such as carboxy methyl ceiiulose, pectin and gelatin for adhesion to... cellulose and nylon films, were most often used in 180 peel adhesion tests on the adhesives. Films were cast on one substrate and the other was moistened...irritation. 4. Peel adhesion to hydrated cellulose , nylon and cotton cloth substrates was satisfactory. So too was the peel adhesion as a function of

  14. Effects of heterocyclic aromatic substituents on binding affinities at two distinct sites of somatostatin receptors. Correlation with the electrostatic potential of the substituents.

    PubMed

    Prasad, Vidya; Birzin, Elizabeth T; McVaugh, Cheryl T; Van Rijn, Rachel D; Rohrer, Susan P; Chicchi, Gary; Underwood, Dennis J; Thornton, Edward R; Smith, Amos B; Hirschmann, Ralph

    2003-05-08

    In our continuing program exploring glucose-based peptidomimetics of somatostatin (SRIF-14), we sought to improve the water solubility of our glycosides. This led to insights into the nature of the ligand binding sites at the SRIF receptor. Replacement of the C4 benzyl substituent in glucoside (+)-2 with pyridinylmethyl or pyrazin-2-ylmethyl congeners increased water solubility and enhanced affinity for the human SRIF subtype receptor 4 (sst4). We attribute this effect to hydrogen bond formation. The pyridin-3-ylmethyl substituent at C4, when combined with the imidazol-4-ylmethyl group at C2, generated (-)-19, which has the highest affinity of a glucose-based peptidomimetic at a human SRIF receptor to date (K(i) 53 +/- 23 nM, n = 6 at sst4). The C4 heterocyclic congeners of glucosides bearing a 1-methoxy substituent rather than an indole side chain at the anomeric carbon, such as (+)-16, also provided information about the Trp(8) binding pocket. We correlated the SARs at both the C4 and the Trp(8) binding pockets with calculations of the electrostatic potentials of the diverse C4 aromatic substituents using Spartan 3-21G(*) MO analysis. These calculations provide an approximate analysis of a molecule's ability to interact within a receptor binding site. Our binding studies show that benzene and indole rings, but not pyridinylmethyl nor pyrazin-2-ylmethyl rings, can bind the hydrophobic Trp(8) binding pocket of sst4. The Spartan 3-21G(*) MO analysis reveals significant negative electrostatic potential in the region of the pi-clouds for the benzene and indole rings but not for the pyridinylmethyl or pyrazin-2-ylmethyl congeners. Our data further demonstrate that the replacement of benzene or indole side chains by heterocyclic aromatic rings typified by pyridine and pyrazine not only enhances water solubility and hydrogen bonding capacity as expected, but can also profoundly diminish the ability of the pi-cloud of the aromatic substituent to interact with side chains

  15. Modeling biophysical and biological properties from the characteristics of the molecular electron density, electron localization and delocalization matrices, and the electrostatic potential.

    PubMed

    Matta, Chérif F

    2014-06-15

    The electron density and the electrostatic potential are fundamentally related to the molecular hamiltonian, and hence are the ultimate source of all properties in the ground- and excited-states. The advantages of using molecular descriptors derived from these fundamental scalar fields, both accessible from theory and from experiment, in the formulation of quantitative structure-to-activity and structure-to-property relationships, collectively abbreviated as QSAR, are discussed. A few such descriptors encode for a wide variety of properties including, for example, electronic transition energies, pK(a)'s, rates of ester hydrolysis, NMR chemical shifts, DNA dimers binding energies, π-stacking energies, toxicological indices, cytotoxicities, hepatotoxicities, carcinogenicities, partial molar volumes, partition coefficients (log P), hydrogen bond donor capacities, enzyme-substrate complementarities, bioisosterism, and regularities in the genetic code. Electronic fingerprinting from the topological analysis of the electron density is shown to be comparable and possibly superior to Hammett constants and can be used in conjunction with traditional bulk and liposolubility descriptors to accurately predict biological activities. A new class of descriptors obtained from the quantum theory of atoms in molecules' (QTAIM) localization and delocalization indices and bond properties, cast in matrix format, is shown to quantify transferability and molecular similarity meaningfully. Properties such as "interacting quantum atoms (IQA)" energies which are expressible into an interaction matrix of two body terms (and diagonal one body "self" terms, as IQA energies) can be used in the same manner. The proposed QSAR-type studies based on similarity distances derived from such matrix representatives of molecular structure necessitate extensive investigation before their utility is unequivocally established.

  16. Modeling Biophysical and Biological Properties From the Characteristics of the Molecular Electron Density, Electron Localization and Delocalization Matrices, and the Electrostatic Potential

    PubMed Central

    Matta*, Chérif F

    2014-01-01

    The electron density and the electrostatic potential are fundamentally related to the molecular hamiltonian, and hence are the ultimate source of all properties in the ground- and excited-states. The advantages of using molecular descriptors derived from these fundamental scalar fields, both accessible from theory and from experiment, in the formulation of quantitative structure-to-activity and structure-to-property relationships, collectively abbreviated as QSAR, are discussed. A few such descriptors encode for a wide variety of properties including, for example, electronic transition energies, pKa's, rates of ester hydrolysis, NMR chemical shifts, DNA dimers binding energies, π-stacking energies, toxicological indices, cytotoxicities, hepatotoxicities, carcinogenicities, partial molar volumes, partition coefficients (log P), hydrogen bond donor capacities, enzyme–substrate complementarities, bioisosterism, and regularities in the genetic code. Electronic fingerprinting from the topological analysis of the electron density is shown to be comparable and possibly superior to Hammett constants and can be used in conjunction with traditional bulk and liposolubility descriptors to accurately predict biological activities. A new class of descriptors obtained from the quantum theory of atoms in molecules' (QTAIM) localization and delocalization indices and bond properties, cast in matrix format, is shown to quantify transferability and molecular similarity meaningfully. Properties such as “interacting quantum atoms (IQA)” energies which are expressible into an interaction matrix of two body terms (and diagonal one body “self” terms, as IQA energies) can be used in the same manner. The proposed QSAR-type studies based on similarity distances derived from such matrix representatives of molecular structure necessitate extensive investigation before their utility is unequivocally established. © 2014 The Author and the Journal of Computational Chemistry Published

  17. Particle adhesion in powder coating

    SciTech Connect

    Mazumder, M.K.; Wankum, D.L.; Knutson, M.; Williams, S.; Banerjee, S.

    1996-12-31

    Electrostatic powder coating is a widely used industrial painting process. It has three major advantages: (1) it provides high quality durable finish, (2) the process is environmentally friendly and does not require the use of organic solvents, and (3) it is economically competitive. The adhesion of electrostatically deposited polymer paint particles on the grounded conducting substrate depends upon many parameters: (a) particle size and shape distributions, (b) electrostatic charge distributions, (c) electrical resistivity, (d) dielectric strength of the particles, (e) thickness of the powder film, (f) presence and severity of the back corona, and (g) the conductivity and surface properties of the substrate. The authors present a model on the forces of deposition and adhesion of corona charged particles on conducting substrates.

  18. Adhesion to Carbon Nanotube Conductive Scaffolds Forces Action-Potential Appearance in Immature Rat Spinal Neurons

    PubMed Central

    Toma, Francesca Maria; Calura, Enrica; Rizzetto, Lisa; Carrieri, Claudia; Roncaglia, Paola; Martinelli, Valentina; Scaini, Denis; Masten, Lara; Turco, Antonio; Gustincich, Stefano; Prato, Maurizio; Ballerini, Laura

    2013-01-01

    In the last decade, carbon nanotube growth substrates have been used to investigate neurons and neuronal networks formation in vitro when guided by artificial nano-scaled cues. Besides, nanotube-based interfaces are being developed, such as prosthesis for monitoring brain activity. We recently described how carbon nanotube substrates alter the electrophysiological and synaptic responses of hippocampal neurons in culture. This observation highlighted the exceptional ability of this material in interfering with nerve tissue growth. Here we test the hypothesis that carbon nanotube scaffolds promote the development of immature neurons isolated from the neonatal rat spinal cord, and maintained in vitro. To address this issue we performed electrophysiological studies associated to gene expression analysis. Our results indicate that spinal neurons plated on electro-conductive carbon nanotubes show a facilitated development. Spinal neurons anticipate the expression of functional markers of maturation, such as the generation of voltage dependent currents or action potentials. These changes are accompanied by a selective modulation of gene expression, involving neuronal and non-neuronal components. Our microarray experiments suggest that carbon nanotube platforms trigger reparative activities involving microglia, in the absence of reactive gliosis. Hence, future tissue scaffolds blended with conductive nanotubes may be exploited to promote cell differentiation and reparative pathways in neural regeneration strategies. PMID:23951361

  19. Adhesion to carbon nanotube conductive scaffolds forces action-potential appearance in immature rat spinal neurons.

    PubMed

    Fabbro, Alessandra; Sucapane, Antonietta; Toma, Francesca Maria; Calura, Enrica; Rizzetto, Lisa; Carrieri, Claudia; Roncaglia, Paola; Martinelli, Valentina; Scaini, Denis; Masten, Lara; Turco, Antonio; Gustincich, Stefano; Prato, Maurizio; Ballerini, Laura

    2013-01-01

    In the last decade, carbon nanotube growth substrates have been used to investigate neurons and neuronal networks formation in vitro when guided by artificial nano-scaled cues. Besides, nanotube-based interfaces are being developed, such as prosthesis for monitoring brain activity. We recently described how carbon nanotube substrates alter the electrophysiological and synaptic responses of hippocampal neurons in culture. This observation highlighted the exceptional ability of this material in interfering with nerve tissue growth. Here we test the hypothesis that carbon nanotube scaffolds promote the development of immature neurons isolated from the neonatal rat spinal cord, and maintained in vitro. To address this issue we performed electrophysiological studies associated to gene expression analysis. Our results indicate that spinal neurons plated on electro-conductive carbon nanotubes show a facilitated development. Spinal neurons anticipate the expression of functional markers of maturation, such as the generation of voltage dependent currents or action potentials. These changes are accompanied by a selective modulation of gene expression, involving neuronal and non-neuronal components. Our microarray experiments suggest that carbon nanotube platforms trigger reparative activities involving microglia, in the absence of reactive gliosis. Hence, future tissue scaffolds blended with conductive nanotubes may be exploited to promote cell differentiation and reparative pathways in neural regeneration strategies.

  20. Electrostatic Levitator Electrodes

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Electrostatic levitation system inside Electrostatic Levitator (ESL) vacuum chamber. The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

  1. Intrinsic electrostatic effects in nanostructured ceramics

    SciTech Connect

    Uberuaga, Blas Pedro; Stanek, Chris R; Nerikar, Pankaj V

    2009-01-01

    Using empirical potentials, we have found that electrostatic dipoles can be created at grain boundaries formed from non-polar surfaces of fluorite-structured materials. In particular, the {Sigma}5(310)/[001] symmetric tilt grain boundary reconstructs to break the symmetry in the atomic structure at the boundary, forming the dipole. This dipole results in an abrupt change in electrostatic potential across the boundary. In multilayered ceramics composed of stacks of grain boundaries, the change in electrostatic potential at the boundary results in profound electrostatic effects within the crystalline layers, the nature of which depends on the electrostatic boundary conditions. For open-circuit boundary conditions, layers with either high or low electrostatic potential are formed. By contrast, for short-circuit boundary conditions, electric fields can be created within each layer, the strength of which then depends on the thickness of the layers. These electrostatic effects may have important consequences for the behavior of defects and dopants within these materials and offer the possibility of interesting technological applications.

  2. ELECTROSTATIC POWER GENERATOR.

    DTIC Science & Technology

    ELECTROSTATIC GENERATORS , POWER EQUIPMENT, ELECTRIC GOVERNORS, CIRCUITS, VACUUM SEALS, ELECTRICAL INSULATION, VACUUM, ELECTRODES, FINISHES, SURFACE...FINISHING, SURFACE PROPERTIES, HARDNESS, PULSE GENERATORS , TRANSFORMERS, FIELD EMISSION.

  3. ELECTROSTATIC POWER GENERATOR.

    DTIC Science & Technology

    ELECTROSTATIC GENERATORS , POWER EQUIPMENT, ELECTRICAL INSULATION, FIELD EMISSION, ELECTRODES, VACUUM, SURFACE PROPERTIES, ANODES, CATHODES, POLISHES...DIELECTRICS, COATINGS, PRESSURE, HARDNESS, PULSE GENERATORS , TRANSFORMERS, VACUUM SEALS, EQUATIONS.

  4. Electrostatic interaction in atomic force microscopy

    PubMed Central

    Butt, Hans-Jüurgen

    1991-01-01

    In atomic force microscopy, the stylus experiences an electrostatic force when imaging in aqueous medium above a charged surface. This force has been calculated numerically with continuum theory for a silicon nitrite or silicon oxide stylus. For comparison, the Van der Waals force was also calculated. In contrast to the Van der Waals attraction, the electrostatic force is repulsive. At a distance of 0.5 nm the electrostatic force is typically 10-12-10-10 N and thus comparable in strength to the Van der Waals force. The electrostatic force increases with increasing surface charge density and decreases roughly exponentially with distance. It can be reduced by imaging in high salt concentrations. Below surface potentials of ≈50 mV, a simple analytical approximation of the electrostatic force is described. PMID:19431803

  5. pH-dependent cross-linking of catechols through oxidation via Fe(3+) and potential implications for mussel adhesion.

    PubMed

    Fullenkamp, Dominic E; Barrett, Devin G; Miller, Dusty R; Kurutz, Josh W; Messersmith, Phillip B

    2014-01-01

    The mussel byssus is a remarkable attachment structure that is formed by injection molding and rapid in-situ hardening of concentrated solutions of proteins enriched in the catecholic amino acid 3,4-dihydroxy-L-phenylalanine (DOPA). Fe(3+), found in high concentrations in the byssus, has been speculated to participate in redox reactions with DOPA that lead to protein polymerization, however direct evidence to support this hypothesis has been lacking. Using small molecule catechols, DOPA-containing peptides, and native mussel foot proteins, we report the first direct observation of catechol oxidation and polymerization accompanied by reduction of Fe(3+) to Fe(2+). In the case of the small molecule catechol, we identified two dominant dimer species and characterized their connectivities by nuclear magnetic resonance (NMR), with the C6-C6 and C5-C6 linked species as the major and minor products, respectively. For the DOPA-containing peptide, we studied the pH dependence of the reaction and demonstrated that catechol polymerization occurs readily at low pH, but is increasingly diminished in favor of metal-catechol coordination interactions at higher pH. Finally, we demonstrate that Fe(3+) can induce cross-links in native byssal mussel proteins mefp-1 and mcfp-1 at acidic pH. Based on these findings, we discuss the potential implications to the chemistry of mussel adhesion.

  6. The N-linking glycosylation system from Actinobacillus pleuropneumoniae is required for adhesion and has potential use in glycoengineering

    PubMed Central

    Bossé, Janine T.; Abouelhadid, Sherif; Li, Yanwen; Lin, Chia-Wei; Vohra, Prerna; Tucker, Alexander W.; Rycroft, Andrew N.; Maskell, Duncan J.; Aebi, Markus; Langford, Paul R.

    2017-01-01

    Actinobacillus pleuropneumoniae is a mucosal respiratory pathogen causing contagious porcine pleuropneumonia. Pathogenesis studies have demonstrated a major role for the capsule, exotoxins and outer membrane proteins. Actinobacillus pleuropneumoniae can also glycosylate proteins, using a cytoplasmic N-linked glycosylating enzyme designated NGT, but its transcriptional arrangement and role in virulence remains unknown. We investigated the NGT locus and demonstrated that the putative transcriptional unit consists of rimO, ngt and a glycosyltransferase termed agt. From this information we used the A. pleuropneumoniae glycosylation locus to decorate an acceptor protein, within Escherichia coli, with a hexose polymer that reacted with an anti-dextran antibody. Mass spectrometry analysis of a truncated protein revealed that this operon could add up to 29 repeat units to the appropriate sequon. We demonstrated the importance of NGT in virulence, by creating deletion mutants and testing them in a novel respiratory cell line adhesion model. This study demonstrates the importance of the NGT glycosylation system for pathogenesis and its potential biotechnological application for glycoengineering. PMID:28077594

  7. Expression of metadherin/AEG-1 gene is positively related to orientation chemotaxis and adhesion of human hepatocellular carcinoma cell lines of different metastatic potentials.

    PubMed

    Zhou, Zhenzhen; Deng, Huan; Yan, Wei; Huang, Huanjun; Deng, Yueling; Li, Yuan; Tian, De'an

    2012-06-01

    Metastasis contributes to the poor prognosis of hepatocellular carcinoma (HCC). However, the mechanism through which a primary HCC cell develops into a metastatic phenotype is not well understood. The purpose of this study was to examine the correlation between metadherin (MTDH)/astrocyte elevated gene-1 (AEG-1) expression in HCC cell lines of different metastatic potentials and such metastatic phenotypes as orientation chemotaxis and adhesion. MTDH/AEG-1 expression was detected by RT-PCR and western blotting in HCC cell lines (HepG2, Huh7, Sk-HEP-1, MHCC-97H). Distribution of MTDH/AEG-1 was observed by immunofluorescence staining and confocal laser scanning microscopy. The abilities of orientation chemotaxis and adhesion and the index of interaction between HCC cell lines and microvascular endothelial cell lines (MVECs, including HUVECs and HPMECs) were measured by chemotaxis assay and adhesion assay, respectively. The results showed that MTDH/AEG-1 protein expression was significantly higher in high metastatic potential cancer cell lines (Sk-HEP-1, MHCC-97H) than in low metastatic potential cell lines (HepG2, Huh7) (P<0.05). The MTDH/AEG-1 protein was localized in the perinuclear region of HCC cells. Furthermore, the abilities of orientation chemotaxis and adhesion of HCC cells to HPMECs were increased as compared with those of HCC cells to HUVECs (P<0.05). The abilities of orientation chemotaxis and adhesion were much stronger in Sk-HEP-1 and MHCC-97H cells with MTDH/AEG-1 highly expressed than in HepG2 and Huh7 cells with MTDH/AEG-1 lowly expressed (P<0.05). These results suggested that the expression of MTDH/AEG-1 gene in HCC cell lines of different metastatic potentials was closely positively related to the abilities of orientation chemotaxis and adhesion of HCC cells. It was deduced that MTDH/AEG-1 might play a pivotal role in the lung-specific metastasis of HCC, which may be mediated through orientation chemotaxis and adhesion abilities of HCC cells. MTDH

  8. Supramolecular architectures in luminescent Zn(II) and Cd(II) complexes containing imidazole derivatives: Crystal structures, vibrational and thermal properties, Hirshfeld surface analysis and electrostatic potentials

    NASA Astrophysics Data System (ADS)

    Di Santo, Alejandro; Echeverría, Gustavo A.; Piro, Oscar E.; Pérez, Hiram; Ben Altabef, Aida; Gil, Diego M.

    2017-04-01

    the crucial importance of weak interactions in building different supramolecular architectures. Furthermore, molecular electrostatic potentials for visualizing and quantifying the attractive character of interactions were calculated.

  9. Electrostatic Levitator (ESL)

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Dr. Rulison of Space System LORAl working with the Electrostatic Levitation (ESL) prior to the donation. Space System/LORAL donated the electrostatic containerless processing system to NASA's Marshall Space Flight Center (MSFC). The official hand over took place in July 1998.

  10. Edutainment Science: Electrostatics

    ERIC Educational Resources Information Center

    Ahlers, Carl

    2009-01-01

    Electrostatics should find a special place in all primary school science curricula. It is a great learning area that reinforces the basics that underpin electricity and atomic structure. Furthermore, it has many well documented hands-on activities. Unfortunately, the "traditional" electrostatics equipment such as PVC rods, woollen cloths, rabbit…

  11. New UPLC coupled to mass spectrometry approaches for screening of non-volatile compounds as potential migrants from adhesives used in food packaging materials.

    PubMed

    Canellas, E; Nerín, C; Moore, R; Silcock, P

    2010-05-07

    The objective of this study was to identify the non-volatile compounds as potential migrants from adhesives used in food packaging. A number of the current acrylic adhesive formulations were extracted and prepared for analysis. The extracts were screened using ultra-performance liquid chromatography coupled to a time-of-flight mass spectrometer detector (UPLC-TOF-MS). This approach allowed the identification of several components by a combination of exact mass and in-source collision induced dissociation (CID). Due to the lack of freely available information on adhesive formulations further analyses were undertaken using ultra-performance liquid chromatography coupled to high definition mass spectrometry (UPLC-HDMS). Using the Mass Fragment tool to interrogate fragmentation data, a wide series of compounds were identified, demonstrating the usefulness and importance of these tools for difficult problems. Moreover, using several packaging materials containing adhesives, qualitative migration tests were performed with Tenax as a food simulant. Several non-volatile compounds were identified as well in the Tenax which emphasizes the importance of this work and demonstrates that even the non-volatile compounds have the potential to migrate into food which is in contact with packaging materials. The main characteristics of the screening study and the results obtained are shown and discussed.

  12. Parallel Control over Surface Charge and Wettability Using Polyelectrolyte Architecture: Effect on Protein Adsorption and Cell Adhesion.

    PubMed

    Guo, Shanshan; Zhu, Xiaoying; Li, Min; Shi, Liya; Ong, June Lay Ting; Jańczewski, Dominik; Neoh, Koon Gee

    2016-11-09

    Surface charge and wettability, the two prominent physical factors governing protein adsorption and cell adhesion, have been extensively investigated in the literature. However, a comparison between these driving forces in terms of their independent and cooperative effects in affecting adhesion is rarely explored on a systematic and quantitative level. Herein, we formulate a protocol that features two-dimensional control over both surface charge and wettability with limited cross-parameter influence. This strategy is implemented by controlling both the polyion charge density in the layer-by-layer (LbL) assembly process and the polyion side-chain chemical structures. The 2D property matrix spans surface isoelectric points ranging from 5 to 9 and water contact angles from 35 to 70°, with other interferential factors (e.g., roughness) eliminated. The interplay between these two surface variables influences protein (bovine serum albumin, lysozyme) adsorption and 3T3 fibroblast cell adhesion. For proteins, we observe the presence of thresholds for surface wettability and electrostatic driving forces necessary to affect adhesion. Beyond these thresholds, the individual effects of electrostatic forces and wettability are observed. For fibroblast, both surface charge and wettability have an effect on its adhesion. The combined effects of positive charge and hydrophilicity lead to the highest cell adhesion, whereas negative charge and hydrophobicity lead to the lowest cell adhesion. Our design strategy can potentially form the basis for studying the distinct behaviors of electrostatic force or wettability driven interfacial phenomena and serve as a reference in future studies assessing protein adsorption and cell adhesion to surfaces with known charge and wettability within the property range studied here.

  13. Application of a collagen-based membrane and chondroitin sulfate-based hydrogel adhesive for the potential repair of severe ocular surface injuries.

    PubMed

    Chae, Jemin J; Mulreany, Daniel G; Guo, Qiongyu; Lu, Qiaozhi; Choi, Joseph S; Strehin, Iossif; Espinoza, Freddy A; Schein, Oliver; Trexler, Morgana M; Bower, Kraig S; Elisseeff, Jennifer H

    2014-06-01

    This study was performed to evaluate the potential of a chondroitin sulfate-polyethylene glycol (CS-PEG) adhesive and collagen-based membrane (collagen vitrigel, CV) combination as a method to treat penetrating ocular injuries on the battlefield and to improve this method with two technologies: an antibiotic releasing CS-PEG adhesive and a corneal shaped CV. Burst testing using porcine cadaveric eyes, high-performance liquid chromatography, the Kirby-Bauer bacterial inhibition test, and CV implantations on the live and cadaveric rabbit eyes were performed. The ocular burst test showed CS-PEG adhesive could successfully repair 5-mm to 6-mm length wounds in the corneal and corneoscleral regions but would require CS-PEG + CV to treat larger wounds similar to those seen on the battlefield. In addition, high performance liquid chromatography and the Kirby-Bauer bacterial inhibition test presented evidence suggesting the vancomycin incorporated CS-PEG could inhibit Staphylococcus infection for 9 days. Furthermore, the curved CV showed an advantage by matching the corneal contour without any wrinkle formation. Although this pilot study showed a limited range of possible applications, we demonstrated that the combination of CS-PEG adhesive + CV is a promising method and the 2 technologies improve their applicability to the special demands of the battlefield.

  14. The electrostatic storage tube

    NASA Technical Reports Server (NTRS)

    Rutherford, R. E., Jr.

    1973-01-01

    An electrostatic camera system is discussed which is based on the electrostatic storage tube. The development of the system was begun following a series of experiments which indicated that the device offers signficantly improved performance over currently available devices. The approach used in developing the high performance camera involves: converting the input image to an electron image at low loss, applying a low noise gain process, and storing the resulting charge pattern in a low-loss target. The basic processes and elements of the electrostatic storage tube are illustrated and discussed. Graphs that depict the camera performance characteristics are included.

  15. Intrauterine Adhesions

    MedlinePlus

    ... adhesion formation are infections of the uterine lining (endometritis), removal of fibroids in the cavity of the ... to prevent adhesions from reforming. Hormonal treatment with estrogen and NSAIDs are frequently prescribed after surgery to ...

  16. Asteroid electrostatic instrumentation and modelling

    NASA Astrophysics Data System (ADS)

    Aplin, K. L.; Bowles, N. E.; Urbak, E.; Keane, D.; Sawyer, E. C.

    2011-06-01

    Asteroid surface material is expected to become photoelectrically charged, and is likely to be transported through electrostatic levitation. Understanding any movement of the surface material is relevant to proposed space missions to return samples to Earth for detailed isotopic analysis. Motivated by preparations for the Marco Polo sample return mission, we present electrostatic modelling for a real asteroid, Itokawa, for which detailed shape information is available, and verify that charging effects are likely to be significant at the terminator and at the edges of shadow regions for the Marco Polo baseline asteroid, 1999JU3. We also describe the Asteroid Charge Experiment electric field instrumentation intended for Marco Polo. Finally, we find that the differing asteroid and spacecraft potentials on landing could perturb sample collection for the short landing time of 20min that is currently planned.

  17. Micromachined electrostatic vertical actuator

    DOEpatents

    Lee, Abraham P.; Sommargren, Gary E.; McConaghy, Charles F.; Krulevitch, Peter A.

    1999-10-19

    A micromachined vertical actuator utilizing a levitational force, such as in electrostatic comb drives, provides vertical actuation that is relatively linear in actuation for control, and can be readily combined with parallel plate capacitive position sensing for position control. The micromachined electrostatic vertical actuator provides accurate movement in the sub-micron to micron ranges which is desirable in the phase modulation instrument, such as optical phase shifting. For example, compact, inexpensive, and position controllable micromirrors utilizing an electrostatic vertical actuator can replace the large, expensive, and difficult-to-maintain piezoelectric actuators. A thirty pound piezoelectric actuator with corner cube reflectors, as utilized in a phase shifting diffraction interferometer can be replaced with a micromirror and a lens. For any very precise and small amplitudes of motion` micromachined electrostatic actuation may be used because it is the most compact in size, with low power consumption and has more straightforward sensing and control options.

  18. More Electrostatic Explorations.

    ERIC Educational Resources Information Center

    Stewart, Gay; Gallai, Ditta

    1998-01-01

    Presents worksheet activities that enable students to explore the concept of electrostatic induction and learn the meaning of grounding. Students build two classic devices, the electrophorus and the leaf electroscope. (DDR)

  19. Graphene Electrostatic Microphone

    NASA Astrophysics Data System (ADS)

    Zhou, Qin; Onishi, Seita; Zettl, A.

    2015-03-01

    We demonstrate a wideband electrostatic graphene microphone displaying flat frequency response over the entire human audible region as well as into the ultrasonic regime. Using the microphone, low-level ultrasonic bat calls are successfully recorded. The microphone can be paired with a similarly constructed electrostatic graphene loudspeaker to create a wideband ultrasonic radio. Materials Sciences Division, Lawrence Berkeley National Laboratory Kavli Energy NanoSciences Institute at the University of California - Berkeley.

  20. Electrostatic discharge test apparatus

    NASA Technical Reports Server (NTRS)

    Smith, William Conrad (Inventor)

    1988-01-01

    Electrostatic discharge properties of materials are quantitatively measured and ranked. Samples are rotated on a turntable beneath selectable, co-available electrostatic chargers, one being a corona charging element and the other a sample-engaging triboelectric charging element. Samples then pass under a voltage meter to measure the amount of residual charge on the samples. After charging is discontinued, measurements are continued to record the charge decay history over time.

  1. Electrostatic Levitator in Use

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Metal droplet levitated inside the Electrostatic Levitator (ESL). The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

  2. Electrostatic Levitator Electrode Layout

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Schematic of Electrostatic Levitator (ESL) electrodes and controls system. The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

  3. Electrostatic Levitator Layout

    NASA Technical Reports Server (NTRS)

    1998-01-01

    General oayout of Electrostatic Levitator (ESL). The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

  4. Electrostatic processing of polymers and polymer composites

    NASA Astrophysics Data System (ADS)

    Sanders, Elliot Howard

    2005-11-01

    Polymers are a broad class of molecules whose use in modern life is undeniable ranging from automobile parts to pharmaceuticals. One method applicable to polymer material production is known as electrostatic processing which includes electrospraying, used to produce films or microparticles, and electrospinning, which can be used to produce fibers or non-woven materials. Electrostatic processing typically results in products with droplet or fiber diameters on the micron or nanometer scale. We have sought to develop novel polymeric materials and composites using electrostatic processing. The end uses of these materials were diverse, and included controlled release of drugs, microencapsulation of proteins and enzymes, provision of molecular cues for directed cell growth, hydronium ion transport, and electrically conductive polymer and catalytically active composites. We have successfully demonstrated that electrostatic processing can be used to produce a wide variety of functionally active polymer based materials with significant commercial, medical, and scientific potential.

  5. Electrostatic particle collection in vacuum

    NASA Astrophysics Data System (ADS)

    Afshar-Mohajer, Nima; Damit, Brian; Wu, Chang-Yu; Sorloaica-Hickman, Nicoleta

    2011-09-01

    Lunar grains accumulate charges due to solar-based ionizing radiations, and the repelling action of like-charged particles causes the levitation of lunar dust. The lunar dust deposit on sensitive and costly surfaces of investigative equipment is a serious concern in lunar explorations. Inspired by electrostatic precipitators (ESPs), the Electrostatic Lunar Dust Collector (ELDC) was proposed for collecting already charged lunar dust particles to prevent the lunar dust threat. As the conditions for terrestrial counterparts are not valid in the lunar environment, equations developed for terrestrial devices yield incorrect predictions in lunar application. Hence, a mathematical model was developed for the ELDC operating in vacuum to determine its collection efficiency. The ratios of electrical energy over potential energy, kinetic energy over potential energy and the ratio of ELDC dimensions were identified to be the key dimensionless parameters. Sensitivity analyses of the relevant parameters showed that depending on ELDC orientation, smaller particles would be collected more easily at vertical orientation, whereas larger particles were easier to collect in a horizontal ELDC configuration. In the worst case scenario, the electrostatic field needed to be 10 times stronger in the vertical mode in order to adequately collect larger particles. The collection efficiency was very sensitive to surface potential of lunar dust and it reached the maximum when surface potential was between 30 and 120 V. Except for regions of the lunar day side with surface potential close to zero, providing 1 kV ( E = 20 kV m -1) with the ELDC was more than enough for collecting all the particles in the most critical orientation. The needed field strength was about 4000 times less than that for repelling 1-μm size particles already settled on the surfaces. The analysis shows that the ELDC offers a viable solution for lunar dust control due to its effectiveness, ease of cleaning and low voltage

  6. Electrostatic Dust Control for Planetary Rovers

    NASA Astrophysics Data System (ADS)

    Clark, P. E.; Curtis, S. A.; Farrell, W. M.; Nuth, J. A.; Stubbs, T. J.; Rilee, M. L.

    2005-12-01

    Detailed study of the physical and chemical nature of the fine particulate portion of the regoliths of these bodies is a key to understanding micrometeorite bombardment and the nature of regolith formation. Thus, missions to sample the surfaces of atmosphereless bodies, including the Moon, asteroids, and Mercury, have been identified as crucial components of solar system exploration over the next decades. We have proposed autonomous reconfigurable robotic manual assistants and lander/rovers for such missions. On the other hand, dust poses problems for mechanisms and exposed surfaces on landers/rovers sent to such bodies. Compromise of seals and loss of sample material, as well as mechanical damage to systems and surfaces, occurred after hours of operation during the Apollo missions. Thus both dust mitigation and dust collection are issues which must be addressed for sampling missions. Dust activity on atmosphereless bodies is ubiquitous and induced by complex interactions of fine particulates, environmentally-dependent fields, and charged particles with vehicle surfaces and mechanisms. Dust particles are both abrasive and adhesive as a result of the melting and crushing from micrometeorite bombardment. Thus, dust dynamics result from the interplay between mechanical and electrostatic forces and are a critical environmental factor with which all rover technologies must deal. We have considered various strategies for dust mitigation. Passive ones include the use of conducting surfaces and O-ring sealing of all mechanisms. Several active mechanisms for not only removing but collecting dust are under consideration. Our inter-disciplinary team is investigating the feasibility of an electrostatically based concept for a dust control. Relatively little work has been done on empirically simulating what happens when another surface is introduced into a non-conducting, dusty regolith. We plan to test our concept by performing empirical simulations of the interaction between

  7. Losartan inhibits the adhesion of rat platelets to fibrillar collagen--a potential role of nitric oxide and prostanoids.

    PubMed

    Matys, T; Chabielska, E; Pawlak, R; Kucharewicz, I; Buczko, W

    2000-12-01

    The aim of the study was to evaluate the effect of losartan on rat platelet adhesion to fibrillar collagen. Washed platelets were counted before and after 15 minutes incubation with collagen (50 microg/ml) and the percentage of adhering platelets was calculated as the index of their adhesion. When the platelets were incubated with collagen 40.8 +/- 0.3% of the platelets adhered. Losartan produced a dose dependent decrease in a number of adhering platelets both when the drug was administered to the animals ex vivo at doses of 3, 10 and 30 mg/kg (p < 0.01-0.001) or was added to the preparation of washed platelets in vitro in concentrations of 10(-8)-10(-5) M (p < 0.01-0.001). In the next step of the study we assessed the influence of L-NAME (10 mg/kg ex vivo, 30 microM in vitro) and indomethacin (2.5 mg/kg ex vivo, 30 microM in vitro) on the antiadhesive effect of losartan (10 mg/kg ex vivo, 10(-6) M in vitro). Blockade of nitric oxide synthase with L-NAME partially reversed the antiadhesive effect of losartan both ex vivo and in vitro. Indomethacin diminished the inhibitory effect of losartan on platelet adhesion when administered ex vivo, but it failed to modify this parameter when added to the suspension of platelets in vitro. In conclusion, losartan reduces platelet adhesion to fibrillar collagen in a dose-dependent manner. The observed action of losartan seems to be mediated mainly by endothelium- and platelet-derived nitric oxide.

  8. High potential of adhesion to biotic and abiotic surfaces by opportunistic Staphylococcus aureus strains isolated from orthodontic appliances.

    PubMed

    Merghni, Abderrahmen; Ben Nejma, Mouna; Dallel, Ines; Tobji, Samir; Ben Amor, Adel; Janel, Sébastien; Lafont, Frank; Aouni, Mahjoub; Mastouri, Maha

    2016-02-01

    Orthodontic and other oral appliances act as reservoir of opportunistic pathogens that can easily become resistant to antibiotics and cause systemic infections. The aim of this study was to investigate the ability of Staphylococcus aureus strains isolated from healthy patients with orthodontic appliances, to adhere to biotic (HeLa cells) and abiotic surfaces (polystyrene and dental alloy). Adhesive ability to polystyrene was tested by crystal violet staining and quantitative biofilm production on dental alloy surfaces was evaluated by MTT reduction assay. In addition, the presence of icaA and icaD genes was achieved by polymerase chain reaction (PCR). Qualitative biofilm production revealed that 70.6% of strains were slime producers. The metabolic activity of S. aureus biofilms on dental alloy surfaces was high and did not differ between tested strains. Moreover, all the isolates were adhesive to HeLa cells and 94% of them harbor icaA and icaD genes. Considerable adhesion and internalization capacity to the epithelial HeLa cells and strong biofilm production abilities together, with a high genotypic expression of icaA/icaD genes are an important equipment of S. aureus to colonize orthodontic appliances and eventually to disseminate towards other body areas.

  9. Altering the Electrostatic Potential in the Major Groove: Thermodynamic and Structural Characterization of 7-Deaza-2;#8242;-deoxyadenosine:dT Base Pairing in DNA

    SciTech Connect

    Kowal, Ewa A.; Ganguly, Manjori; Pallan, Pradeep S.; Marky, Luis A.; Gold, Barry; Egli, Martin; Stone, Michael P.

    2012-02-15

    As part of an ongoing effort to explore the effect of major groove electrostatics on the thermodynamic stability and structure of DNA, a 7-deaza-2'-deoxyadenosine:dT (7-deaza-dA:dT) base pair in the Dickerson-Drew dodecamer (DDD) was studied. The removal of the electronegative N7 atom on dA and the replacement with an electropositive C-H in the major groove was expected to have a significant effect on major groove electrostatics. The structure of the 7-deaza-dA:dT base pair was determined at 1.1 {angstrom} resolution in the presence of Mg{sup 2+}. The 7-deaza-dA, which is isosteric for dA, had minimal effect on the base pairing geometry and the conformation of the DDD in the crystalline state. There was no major groove cation association with the 7-deaza-dA heterocycle. In solution, circular dichroism showed a positive Cotton effect centered at 280 nm and a negative Cotton effect centered at 250 nm that were characteristic of a right-handed helix in the B-conformation. However, temperature-dependent NMR studies showed increased exchange between the thymine N3 imino proton of the 7-deaza-dA:dT base pair and water, suggesting reduced stacking interactions and an increased rate of base pair opening. This correlated with the observed thermodynamic destabilization of the 7-deaza-dA modified duplex relative to the DDD. A combination of UV melting and differential scanning calorimetry experiments were conducted to evaluate the relative contributions of enthalpy and entropy in the thermodynamic destabilization of the DDD. The most significant contribution arose from an unfavorable enthalpy term, which probably results from less favorable stacking interactions in the modified duplex, which was accompanied by a significant reduction in the release of water and cations from the 7-deaza-dA modified DNA.

  10. Altering the electrostatic potential in the major groove: thermodynamic and structural characterization of 7-deaza-2'-deoxyadenosine:dT base pairing in DNA.

    PubMed

    Kowal, Ewa A; Ganguly, Manjori; Pallan, Pradeep S; Marky, Luis A; Gold, Barry; Egli, Martin; Stone, Michael P

    2011-12-01

    As part of an ongoing effort to explore the effect of major groove electrostatics on the thermodynamic stability and structure of DNA, a 7-deaza-2'-deoxyadenosine:dT (7-deaza-dA:dT) base pair in the Dickerson-Drew dodecamer (DDD) was studied. The removal of the electronegative N7 atom on dA and the replacement with an electropositive C-H in the major groove was expected to have a significant effect on major groove electrostatics. The structure of the 7-deaza-dA:dT base pair was determined at 1.1 Å resolution in the presence of Mg(2+). The 7-deaza-dA, which is isosteric for dA, had minimal effect on the base pairing geometry and the conformation of the DDD in the crystalline state. There was no major groove cation association with the 7-deaza-dA heterocycle. In solution, circular dichroism showed a positive Cotton effect centered at 280 nm and a negative Cotton effect centered at 250 nm that were characteristic of a right-handed helix in the B-conformation. However, temperature-dependent NMR studies showed increased exchange between the thymine N3 imino proton of the 7-deaza-dA:dT base pair and water, suggesting reduced stacking interactions and an increased rate of base pair opening. This correlated with the observed thermodynamic destabilization of the 7-deaza-dA modified duplex relative to the DDD. A combination of UV melting and differential scanning calorimetry experiments were conducted to evaluate the relative contributions of enthalpy and entropy in the thermodynamic destabilization of the DDD. The most significant contribution arose from an unfavorable enthalpy term, which probably results from less favorable stacking interactions in the modified duplex, which was accompanied by a significant reduction in the release of water and cations from the 7-deaza-dA modified DNA.

  11. Clustering of carboxylated magnetite nanoparticles through polyethylenimine: Covalent versus electrostatic approach

    NASA Astrophysics Data System (ADS)

    Tóth, Ildikó Y.; Nesztor, Dániel; Novák, Levente; Illés, Erzsébet; Szekeres, Márta; Szabó, Tamás; Tombácz, Etelka

    2017-04-01

    Carboxylated magnetite nanoparticles (MNPs) are frequently used to develop materials with enhanced properties for MRI and hyperthermia. The controlled clustering of MNPs via covalent or electrostatic approaches provides opportunity to prepare high quality materials. MNPs were prepared by co-precipitation and coated by poly(acrylic acid-co-maleic acid) (PAM@MNP). The clusters were synthesized from purified PAM@MNPs and polyethylenimine (PEI) solution via electrostatic interaction and covalent bond formation (ES-cluster and CB-cluster, respectively). The electrostatic adhesion (-NH3+ and -COO-) and the formed amide bond were confirmed by ATR-FTIR. The averaged area of CB-clusters was about twice as large as that of ES-cluster, based on TEM. The SAXS results showed that the surface of MNPs was smooth and the nanoparticles were close packed in both clusters. The pH-dependent aggregation state and zeta potential of clusters were characterized by DLS and electrophoresis measurements, the clusters were colloidally stable at pH>5. In hyperthermia experiments, the values of SAR were about two times larger for the chemically bonded cluster. The MRI studies showed exceptionally high transversion relaxivities, the r2 values are 457 mM-1 s-1 and 691 mM-1 s-1 for ES-cluster and CB-cluster, respectively. Based on these results, the chemically clustered product shows greater potential for feasible biomedical applications.

  12. Cell cycle- and cancer-associated gene networks activated by Dsg2: evidence of cystatin A deregulation and a potential role in cell-cell adhesion.

    PubMed

    Gupta, Abhilasha; Nitoiu, Daniela; Brennan-Crispi, Donna; Addya, Sankar; Riobo, Natalia A; Kelsell, David P; Mahoney, Mỹ G

    2015-01-01

    Cell-cell adhesion is paramount in providing and maintaining multicellular structure and signal transmission between cells. In the skin, disruption to desmosomal regulated intercellular connectivity may lead to disorders of keratinization and hyperproliferative disease including cancer. Recently we showed transgenic mice overexpressing desmoglein 2 (Dsg2) in the epidermis develop hyperplasia. Following microarray and gene network analysis, we demonstrate that Dsg2 caused a profound change in the transcriptome of keratinocytes in vivo and altered a number of genes important in epithelial dysplasia including: calcium-binding proteins (S100A8 and S100A9), members of the cyclin protein family, and the cysteine protease inhibitor cystatin A (CSTA). CSTA is deregulated in several skin cancers, including squamous cell carcinomas (SCC) and loss of function mutations lead to recessive skin fragility disorders. The microarray results were confirmed by qPCR, immunoblotting, and immunohistochemistry. CSTA was detected at high level throughout the newborn mouse epidermis but dramatically decreased with development and was detected predominantly in the differentiated layers. In human keratinocytes, knockdown of Dsg2 by siRNA or shRNA reduced CSTA expression. Furthermore, siRNA knockdown of CSTA resulted in cytoplasmic localization of Dsg2, perturbed cytokeratin 14 staining and reduced levels of desmoplakin in response to mechanical stretching. Both knockdown of either Dsg2 or CSTA induced loss of cell adhesion in a dispase-based assay and the effect was synergistic. Our findings here offer a novel pathway of CSTA regulation involving Dsg2 and a potential crosstalk between Dsg2 and CSTA that modulates cell adhesion. These results further support the recent human genetic findings that loss of function mutations in the CSTA gene result in skin fragility due to impaired cell-cell adhesion: autosomal-recessive exfoliative ichthyosis or acral peeling skin syndrome.

  13. Cell Cycle- and Cancer-Associated Gene Networks Activated by Dsg2: Evidence of Cystatin A Deregulation and a Potential Role in Cell-Cell Adhesion

    PubMed Central

    Gupta, Abhilasha; Nitoiu, Daniela; Brennan-Crispi, Donna; Addya, Sankar; Riobo, Natalia A.; Kelsell, David P.; Mahoney, Mỹ G.

    2015-01-01

    Cell-cell adhesion is paramount in providing and maintaining multicellular structure and signal transmission between cells. In the skin, disruption to desmosomal regulated intercellular connectivity may lead to disorders of keratinization and hyperproliferative disease including cancer. Recently we showed transgenic mice overexpressing desmoglein 2 (Dsg2) in the epidermis develop hyperplasia. Following microarray and gene network analysis, we demonstrate that Dsg2 caused a profound change in the transcriptome of keratinocytes in vivo and altered a number of genes important in epithelial dysplasia including: calcium-binding proteins (S100A8 and S100A9), members of the cyclin protein family, and the cysteine protease inhibitor cystatin A (CSTA). CSTA is deregulated in several skin cancers, including squamous cell carcinomas (SCC) and loss of function mutations lead to recessive skin fragility disorders. The microarray results were confirmed by qPCR, immunoblotting, and immunohistochemistry. CSTA was detected at high level throughout the newborn mouse epidermis but dramatically decreased with development and was detected predominantly in the differentiated layers. In human keratinocytes, knockdown of Dsg2 by siRNA or shRNA reduced CSTA expression. Furthermore, siRNA knockdown of CSTA resulted in cytoplasmic localization of Dsg2, perturbed cytokeratin 14 staining and reduced levels of desmoplakin in response to mechanical stretching. Both knockdown of either Dsg2 or CSTA induced loss of cell adhesion in a dispase-based assay and the effect was synergistic. Our findings here offer a novel pathway of CSTA regulation involving Dsg2 and a potential crosstalk between Dsg2 and CSTA that modulates cell adhesion. These results further support the recent human genetic findings that loss of function mutations in the CSTA gene result in skin fragility due to impaired cell-cell adhesion: autosomal-recessive exfoliative ichthyosis or acral peeling skin syndrome. PMID:25785582

  14. Electrostatics of a Family of Conducting Toroids

    ERIC Educational Resources Information Center

    Lekner, John

    2009-01-01

    An exact solution is found for the electrostatic potential of a family of conducting charged toroids. The toroids are characterized by two lengths "a" and "b", with "a" greater than or equal to "2b". They are closed, with no hole in the "doughnut". The results are obtained by considering the potential of two equal charges, displaced from the…

  15. Electrostatic graphene loudspeaker

    NASA Astrophysics Data System (ADS)

    Zhou, Qin; Zettl, A.

    2013-06-01

    Graphene has extremely low mass density and high mechanical strength, and key qualities for efficient wide-frequency-response electrostatic audio speaker design. Low mass ensures good high frequency response, while high strength allows for relatively large free-standing diaphragms necessary for effective low frequency response. Here, we report on construction and testing of a miniaturized graphene-based electrostatic audio transducer. The speaker/earphone is straightforward in design and operation and has excellent frequency response across the entire audio frequency range (20 Hz-20 kHz), with performance matching or surpassing commercially available audio earphones.

  16. Electrostatic Levitator Vacuum Chamber

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Optical ports ring the Electrostatic Levitator (ESL) vacuum chamber to admit light from the heating laser (beam passes through the window at left), positioning lasers (one port is at center), and lamps to allow diagnostic instruments to view the sample. The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

  17. Electrostatic Levitator Inspected

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Larry Savage, Dr. Jan Rogers, Dr. Michael Robinson (All NASA) and Doug Huie (Mevatec) inspect the Electrostatic Levitator (ESL) at NASA's Marshall Space Flight Center (MSFC). The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

  18. Electrostatic Levitator (ESL) Undercooling

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Graph depicting Electrostatic Levitator (ESL) heating and cooling cycle to achieve undercooling of liquid metals. The ESL uses static electricity to suspend an object (about 3-4 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contracting the container or any instruments, conditions that would alter the readings. The electrostatic Levitator is one of several tools used in NASA's microgravity matierials sciences program.

  19. Electrostatic Levitator at Work

    NASA Technical Reports Server (NTRS)

    2000-01-01

    A 3 mm drop of nickel-zirconium, heated to incandescence, hovers between electrically charged plates inside the Electrostatic Levitator (ESL). The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

  20. Novel secreted isoform of adhesion molecule ICAM-4: Potential regulator of membrane-associated ICAM-4 interactions

    SciTech Connect

    Lee, Gloria; Spring, Frances A.; Parons, Stephen F.; Mankelow, Tosti J.; Peters, Luanne L.; Koury, Mark J.; Mohandas, Narla; Anstee, David J.; Chasis, Joel Anne

    2003-02-18

    ICAM-4, a newly characterized adhesion molecule, is expressed early in human erythropoiesis and functions as a ligand for binding a4b1 and aV integrin-expressing cells. Within the bone marrow, erythroblasts surround central macrophages forming erythroblastic islands. Evidence suggests that these islands are highly specialized subcompartments where cell adhesion events, in concert with cytokines, play critical roles in regulating erythropoiesis and apoptosis. Since erythroblasts express a4b1 and ICAM-4 and macrophages exhibit aV, ICAM-4 is an attractive candidate for mediating cellular interactions within erythroblastic islands. To determine whether ICAM-4 binding properties are conserved across species, we first cloned and sequenced the murine homologue. The translated amino acid sequence showed 68 percent overall identity with human ICAM-4. Using recombinant murine ICAM-4 extracellular domains, we discovered that hematopoietic a4b1-expressing HEL cells and non-hematopoietic aV-expressing FLY cells adhered to mouse ICAM-4. Cell adhesion studies showed that FLY and HEL cells bound to mouse and human proteins with similar avidity. These data strongly suggest conservation of integrin-binding properties across species. Importantly, we characterized a novel second splice cDNA that would be predicted to encode an ICAM-4 isoform, lacking the membrane-spanning domain. Erythroblasts express both isoforms of ICAM-4. COS-7 cells transfected with GFP constructs of prototypic or novel ICAM-4 cDNA showed different cellular localization patterns. Moreover, analysis of tissue culture medium revealed that the novel ICAM-4 cDNA encodes a secreted protein. We postulate that secretion of this newly described isoform, ICAM-4S, may modulate binding of membrane-associated ICAM-4 and could thus play a critical regulatory role in erythroblast molecular attachments.

  1. Abdominal Adhesions

    MedlinePlus

    ... Adhesions 1 Ward BC, Panitch A. Abdominal adhesions: current and novel therapies. Journal of Surgical Research. 2011;165(1):91–111. Seek Help for ... and how to participate, visit the NIH Clinical Research Trials and You website ... Foundation for Functional Gastrointestinal Disorders 700 West Virginia ...

  2. Nanoscale Electrostatics in Mitosis

    NASA Astrophysics Data System (ADS)

    Gagliardi, L. John; West, Patrick Michael

    2001-04-01

    Primitive biological cells had to divide with very little biology. This work simulates a physicochemical mechanism, based upon nanoscale electrostatics, which explains the anaphase A poleward motion of chromosomes. In the cytoplasmic medium that exists in biological cells, electrostatic fields are subject to strong attenuation by Debye screening, and therefore decrease rapidly over a distance equal to several Debye lengths. However, the existence of microtubules within cells changes the situation completely. Microtubule dimer subunits are electric dipolar structures, and can act as intermediaries that extend the reach of the electrostatic interaction over cellular distances. Experimental studies have shown that intracellular pH rises to a peak at mitosis, and decreases through cytokinesis. This result, in conjunction with the electric dipole nature of microtubule subunits and the Debye screened electrostatic force is sufficient to explain and unify the basic events during mitosis and cytokinesis: (1) assembly of asters, (2) motion of the asters to poles, (3) poleward motion of chromosomes (anaphase A), (4) cell elongation, and (5) cytokinesis. This paper will focus on a simulation of the dynamics if anaphase A motion based on this comprehensive model. The physicochemical mechanisms utilized by primitive cells could provide important clues regarding our understanding of cell division in modern eukaryotic cells.

  3. Magnetosheath electrostatic turbulence

    NASA Technical Reports Server (NTRS)

    Rodriquez, P.

    1977-01-01

    The spectrum of electrostatic plasma waves in the terrestrial magnetosheath was studied using the plasma wave experiment on the IMP-6 satellite. Electrostatic plasma wave turbulence is almost continuously present throughout the magnetosheath with broadband (20 Hz- 70 kHz) r.m.s. field intensities typically 0.01 - 1.0 millivolts/m. Peak intensities of about 1.0 millivolts/m near the electron plasma frequency (30 - 60 kHz) were detected occasionally. The components usually identified in the spectrum of magnetosheath electrostatic turbulence include a high frequency ( or = 30 kHz) component peaking at the electron plasma frequency f sub pe, a low frequency component with a broad intensity maximum below the nominal ion plasma frequency f sub pi (approximately f sub pe/43), and a less well defined intermediate component in the range f sub pi f f sub pe. The intensity distribution of magnetosheath electrostatic turbulence clearly shows that the low frequency component is associated with the bow shock, suggesting that the ion heating begun at the shock continues into the downstream magnetosheath.

  4. Electrostatics of Rigid Polyelectrolytes

    SciTech Connect

    Wong, G.C.L.

    2009-06-04

    The organization of rigid biological polyelectrolytes by multivalent ions and macroions are important for many fundamental problems in biology and biomedicine, such as cytoskeletal regulation and antimicrobial sequestration in cystic fibrosis. These polyelectrolytes have been used as model systems for understanding electrostatics in complex fluids. Here, we review some recent results in theory, simulations, and experiments.

  5. Amine-Rich Organic Thin Films for Cell Culture: Possible Electrostatic Effects in Cell-Surface Interactions

    NASA Astrophysics Data System (ADS)

    Wertheimer, Michael R.; St-Georges-Robillard, Amélie; Lerouge, Sophie; Mwale, Fackson; Elkin, Bentsian; Oehr, Christian; Wirges, Werner; Gerhard, Reimund

    2012-11-01

    In recent communications from these laboratories, we observed that amine-rich thin organic layers are very efficient surfaces for the adhesion of mammalian cells. We prepare such deposits by plasma polymerization at low pressure, atmospheric pressure, or by vacuum-ultraviolet photo-polymerization. More recently, we have also investigated a commercially available material, Parylene diX AM. In this article we first briefly introduce literature relating to electrostatic interactions between cells, proteins, and charged surfaces. We then present certain selected cell-response results that pertain to applications in orthopedic and cardiovascular medicine: we discuss the influence of surface properties on the observed behaviors of two particular cell lines, human U937 monocytes, and Chinese hamster ovary cells. Particular emphasis is placed on possible electrostatic attractive forces due to positively charged R-NH3+ groups and negatively charged proteins and cells, respectively. Experiments carried out with electrets, polymers with high positive or negative surface potentials are added for comparison.

  6. Arbitrary order permanent Cartesian multipolar electrostatic interactions

    NASA Astrophysics Data System (ADS)

    Boateng, H. A.; Todorov, I. T.

    2015-01-01

    Recently, there has been a concerted effort to implement advanced classical potential energy surfaces by adding higher order multipoles to fixed point charge electrostatics in a bid to increase the accuracy of simulations of condensed phase systems. One major hurdle is the unwieldy nature of the expressions which in part has limited developers mostly to including only dipoles and quadrupoles. In this paper, we present a generalization of the Cartesian formulation of electrostatic multipolar interactions that enables the specification of an arbitrary order of multipoles. Specifically, we derive formulas for arbitrary order implementation of the particle mesh Ewald method and give a closed form formula for the stress tensor in the reciprocal space. In addition, we provide recurrence relations for common electrostatic potentials employed in molecular simulations, which allows for the generalization to arbitrary order and guarantees a computational cost that scales as O(p3) for Cartesian multipole interactions of order p.

  7. A nontransferring dry adhesive with hierarchical polymer nanohairs.

    PubMed

    Jeong, Hoon Eui; Lee, Jin-Kwan; Kim, Hong Nam; Moon, Sang Heup; Suh, Kahp Y

    2009-04-07

    We present a simple yet robust method for fabricating angled, hierarchically patterned high-aspect-ratio polymer nanohairs to generate directionally sensitive dry adhesives. The slanted polymeric nanostructures were molded from an etched polySi substrate containing slanted nanoholes. An angled etching technique was developed to fabricate slanted nanoholes with flat tips by inserting an etch-stop layer of silicon dioxide. This unique etching method was equipped with a Faraday cage system to control the ion-incident angles in the conventional plasma etching system. The polymeric nanohairs were fabricated with tailored leaning angles, sizes, tip shapes, and hierarchical structures. As a result of controlled leaning angle and bulged flat top of the nanohairs, the replicated, slanted nanohairs showed excellent directional adhesion, exhibiting strong shear attachment (approximately 26 N/cm(2) in maximum) in the angled direction and easy detachment (approximately 2.2 N/cm(2)) in the opposite direction, with a hysteresis value of approximately 10. In addition to single scale nanohairs, monolithic, micro-nanoscale combined hierarchical hairs were also fabricated by using a 2-step UV-assisted molding technique. These hierarchical nanoscale patterns maintained their adhesive force even on a rough surface (roughness <20 microm) because of an increase in the contact area by the enhanced height of hierarchy, whereas simple nanohairs lost their adhesion strength. To demonstrate the potential applications of the adhesive patch, the dry adhesive was used to transport a large-area glass (47.5 x 37.5 cm(2), second-generation TFT-LCD glass), which could replace the current electrostatic transport/holding system with further optimization.

  8. Theoretical insight into the binding energy and detonation performance of ε-, γ-, β-CL-20 cocrystals with β-HMX, FOX-7, and DMF in different molar ratios, as well as electrostatic potential.

    PubMed

    Feng, Rui-Zhi; Zhang, Shu-Hai; Ren, Fu-de; Gou, Rui-Jun; Gao, Li

    2016-06-01

    Molecular dynamics method was employed to study the binding energies on the selected crystal planes of the ε-, γ-, β-conformation 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (ε-, γ-, β-CL-20) cocrystal explosives with 1,1-diamino-2,2-dinitroethylene (FOX-7), 1,3,5,7-tetranitro- 1,3,5,7-tetrazacyclooctane with β-conformation (β-HMX) and N,N-dimethylformamide (DMF) in different molar ratios. The oxygen balance, density, detonation velocity, detonation pressure, and surface electrostatic potential were analyzed. The results indicate that the binding energies E b (*) and stabilities are in the order of 1:1 > 2:1 > 3:1 > 5:1 > 8:1 (CL-20:FOX-7/β-HMX/DMF). The values of E b (*) and stabilities of the energetic-nonenergetic CL-20/DMF cocrystals are far larger than those of the energetic-energetic CL-20/FOX-7 and CL-20/β-HMX, and those of CL-20/β-HMX are the smallest. For CL-20/FOX-7 and CL-20/β-HMX, the largest E b (*) appears in the cocrystals with the 1:1, 1:2 or 1:3 molar ratio, and the stabilities of the cocrystals with the excess ratio of CL-20 are weaker than those in the cocrystals with the excess ratio of FOX-7 or β-HMX. In CL-20/FOX-7, CL-20 prefers adopting the γ-form, and ε-CL-20 is the preference in CL-20/β-HMX, and ε-CL-20 and β-CL-20 can be found in CL-20/DMF. The CL-20/FOX-7 and CL-20/β-HMX cocrystals with low molar ratios can meet the requirements of low sensitive high energetic materials. Surface electrostatic potential reveals the nature of the sensitivity change upon the cocrystal formation. Graphical Abstract MD method was employed to study the binding energies on the selected crystal planes in the ε-, γ-, β-CL-20 cocrystals with FOX-7, β-HMX and DMF in different molar ratios. Surface electrostatic potential reveals the nature of the sensitivity change in cocrystals.

  9. Electrostatic particle trap for ion beam sputter deposition

    DOEpatents

    Vernon, Stephen P.; Burkhart, Scott C.

    2002-01-01

    A method and apparatus for the interception and trapping of or reflection of charged particulate matter generated in ion beam sputter deposition. The apparatus involves an electrostatic particle trap which generates electrostatic fields in the vicinity of the substrate on which target material is being deposited. The electrostatic particle trap consists of an array of electrode surfaces, each maintained at an electrostatic potential, and with their surfaces parallel or perpendicular to the surface of the substrate. The method involves interception and trapping of or reflection of charged particles achieved by generating electrostatic fields in the vicinity of the substrate, and configuring the fields to force the charged particulate material away from the substrate. The electrostatic charged particle trap enables prevention of charged particles from being deposited on the substrate thereby enabling the deposition of extremely low defect density films, such as required for reflective masks of an extreme ultraviolet lithography (EUVL) system.

  10. Selective Adhesion Rate Control of Micron-Scale Objects Using NanoPatterned Surfaces

    NASA Astrophysics Data System (ADS)

    Davis, Jeffrey; Santore, Maria; Kalasin, Surachate; Duffadar, Ranojoy; Kozlova, Natalia

    2006-11-01

    Dynamic particle adhesion from flowing solution onto collecting surfaces, heterogeneous at the submicron scale, occurs in important natural scenarios and current technologies. Potential new applications for sensing, separating, and sorting objects in the 200 nm to 5 μm range will stem from our ability to manipulate selectively their dynamic adhesion in flowing conditions. We describe micron-scale particle adhesion from suspensions flowing over surfaces tailored at the 10-50 nm lengthscale. Our collecting surfaces were generally repulsive (electrostatically) towards 500 nm and 1 μm flowing silica particles, but the collectors also contained randomly distributed polymeric or proteinaceous entities that produced spatially fluctuating attractions. With these systems we observed a dependence of the particle capture rate on the density of adhesive groups and, more importantly, an adhesion threshold or lower limit on the feature density that gave rise to a curvature-based selectivity. A semiquantitative fluctuation treatment captures the essential observations, while hydrodynamic simulations also predict the adhesion threshold and particle dynamics near the collecting surfaces.

  11. PXL01 in sodium hyaluronate results in increased PRG4 expression: a potential mechanism for anti-adhesion

    PubMed Central

    Edsfeldt, Sara; Holm, Björn; Mahlapuu, Margit; Reno, Carol; Hart, David A.; Wiig, Monica

    2017-01-01

    Purpose To investigate the anti-adhesive mechanisms of PXL01 in sodium hyaluronate (HA) by using the rabbit lactoferrin peptide, rabPXL01 in HA, in a rabbit model of healing tendons and tendon sheaths. The mechanism of action for PXL01 in HA is interesting since a recent clinical study of the human lactoferrin peptide PXL01 in HA administered around repaired tendons in the hand showed improved digit mobility. Materials and methods On days 1, 3, and 6 after tendon injury and surgical repair, reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) was used to assess mRNA expression levels for genes encoding the mucinous glycoprotein PRG4 (also called lubricin) and a subset of matrix proteins, cytokines, and growth factors involved in flexor tendon repair. RabPXL01 in HA was administered locally around the repaired tendons, and mRNA expression was compared with untreated repaired tendons and tendon sheaths. Results We observed, at all time points, increased expression of PRG4 mRNA in tendons treated with rabPXL01 in HA, but not in tendon sheaths. In addition, treatment with rabPXL01 in HA led to repression of the mRNA levels for the pro-inflammatory mediators interleukin (IL)-1β, IL-6, and IL-8 in tendon sheaths. Conclusions RabPXL01 in HA increased lubricin mRNA production while diminishing mRNA levels of inflammatory mediators, which in turn reduced the gliding resistance and inhibited the adhesion formation after flexor tendon repair. PMID:27658527

  12. Automated Electrostatics Environmental Chamber

    NASA Technical Reports Server (NTRS)

    Calle, Carlos; Lewis, Dean C.; Buchanan, Randy K.; Buchanan, Aubri

    2005-01-01

    The Mars Electrostatics Chamber (MEC) is an environmental chamber designed primarily to create atmospheric conditions like those at the surface of Mars to support experiments on electrostatic effects in the Martian environment. The chamber is equipped with a vacuum system, a cryogenic cooling system, an atmospheric-gas replenishing and analysis system, and a computerized control system that can be programmed by the user and that provides both automation and options for manual control. The control system can be set to maintain steady Mars-like conditions or to impose temperature and pressure variations of a Mars diurnal cycle at any given season and latitude. In addition, the MEC can be used in other areas of research because it can create steady or varying atmospheric conditions anywhere within the wide temperature, pressure, and composition ranges between the extremes of Mars-like and Earth-like conditions.

  13. Electrostatically clean solar array

    NASA Technical Reports Server (NTRS)

    Stern, Theodore Garry (Inventor); Krumweide, Duane Eric (Inventor)

    2004-01-01

    Provided are methods of manufacturing an electrostatically clean solar array panel and the products resulting from the practice of these methods. The preferred method uses an array of solar cells, each with a coverglass where the method includes machining apertures into a flat, electrically conductive sheet so that each aperture is aligned with and undersized with respect to its matched coverglass sheet and thereby fashion a front side shield with apertures (FSA). The undersized portion about each aperture of the bottom side of the FSA shield is bonded to the topside portions nearest the edges of each aperture's matched coverglass. Edge clips are attached to the front side aperture shield edges with the edge clips electrically and mechanically connecting the tops of the coverglasses to the solar panel substrate. The FSA shield, edge clips and substrate edges are bonded so as to produce a conductively grounded electrostatically clean solar array panel.

  14. Electrostatic phenomena in organic semiconductors: fundamentals and implications for photovoltaics

    NASA Astrophysics Data System (ADS)

    D'Avino, Gabriele; Muccioli, Luca; Castet, Frédéric; Poelking, Carl; Andrienko, Denis; Soos, Zoltán G.; Cornil, Jérôme; Beljonne, David

    2016-11-01

    This review summarizes the current understanding of electrostatic phenomena in ordered and disordered organic semiconductors, outlines numerical schemes developed for quantitative evaluation of electrostatic and induction contributions to ionization potentials and electron affinities of organic molecules in a solid state, and illustrates two applications of these techniques: interpretation of photoelectron spectroscopy of thin films and energetics of heterointerfaces in organic solar cells.

  15. Electrostatic Levitator Operations

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Dr. Jan Rogers (left) and Larry Savage (foreground) of the Science Directorate at NASA's Marshall Space Flight Center are joined by Dr. Richard Weber (Center) and April Hixon of Containerless Research Inc. of Evanston, Ill., in conducting an experiment run of the Electrostatic Levitator (ESL) using insulating materials. Materials researchers use unique capability of the facility to levitate and study the properties of various materials important in manufacturing processes.

  16. Theoretical insights into the stabilities, detonation performance, and electrostatic potentials of cocrystals containing α- or β-HMX and TATB, FOX-7, NTO, or DMF in various molar ratios.

    PubMed

    Song, Ken-Peng; Ren, Fu-de; Zhang, Shu-Hai; Shi, Wen-Jing

    2016-10-01

    A molecular dynamics method was employed to study the binding energies associated with the cocrystallization (at selected crystal planes) of either 1,3,5-triamino-2,4,6-trinitro-benzene (TATB), 1,1-diamino-2,2-dinitroethylene, 3-nitro-1,2,4-triazol-5-one (TATB, FOX-7, and NTO, respectively, all of which are explosives), or N,N-dimethylformamide (DMF, a nonenergetic solvent) in various molar ratios with 1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane in its α and β conformations (α-HMX and β-HMX, respectively). The results showed that the cocrystals with low molar ratios (2:1, 1:1, 1:2, and 1:3) were the most stable. The binding energies of HMX/NTO and HMX/DMF were larger than those of HMX/TATB and HMX/FOX-7. According to the calculated stabilities, HMX prefers to adopt its α form in HMX/TATB and its β form in HMX/NTO, whereas the two forms coexist in HMX/FOX-7. For HMX/TATB, HMX/NTO, and α-HMX/FOX-7, increasing the proportion of the cocrystal component with the highest detonation heat (HMX in the first two cases, FOX-7 in the latter) increases the detonation heat, velocity, and pressure of the cocrystal. However, increasing the proportion of the component with the highest detonation heat in β-HMX/FOX-7 and γ-CL-20/FOX-7 increases the detonation heat of the cocrystal but decreases its detonation velocity. An investigation of the surface electrostatic potential revealed how the sensitivity changes upon cocrystal formation. Graphical Abstract Surface electrostatic potential of HMX/TATB.

  17. Electrostatics of Granular Materials

    NASA Technical Reports Server (NTRS)

    Marshall, John

    2004-01-01

    The purpose of the research was to continue developing an understanding of electrostatic phenomena in preparation for any future flight opportunities of the EGM experiment, originally slated for a 2004 Space Station deployment. Work would be based on theoretical assessments, ground-based lab experiments, and reduced-gravity experiments. The ability to examine dipoles in the lab proved to be elusive, and thus, effort was concentrated on monopoles -how materials become charged, the fate of the charge, the role of material type, and so forth. Several significant milestones were achieved in this regard. In regard of the dipoles, experiments were designed in collaboration with the University of Chicago school district who had access to reduced gravity on the KC-135 aircraft. Two experiments were slated to fly last year but were cancelled after the Columbia accident. One of the experiments has been given a second life and will fly sometime in 2005 if the Shuttle flights resume. There remains active interest in the question of electrostatic dipoles within the educational community, and experiments using magnetic dipoles as a substitute are to be examined. The KC-135 experiments will also examine dispersion methods for particles as a verification of possible future techniques in microgravity. Both laboratory and theoretical work established a number of breakthroughs in our understanding of electrostatic phenomena. These breakthroughs are listed in this paper.

  18. Electrostatic Plasma Accelerator (EPA)

    NASA Technical Reports Server (NTRS)

    Brophy, John R.; Aston, Graeme

    1989-01-01

    The Electrostatic Plasma Accelerator (EPA) is a thruster concept which promises specific impulse levels between low power arcjets and those of the ion engine while retaining the relative simplicity of the arcjet. The EPA thruster produces thrust through the electrostatic acceleration of a moderately dense plasma. No accelerating electrodes are used and the specific impulse is a direct function of the applied discharge voltage and the propellant atomic mass. The goal of the present program is to demonstrate feasibility of the EPA thruster concept through experimental and theoretical investigations of the EPA acceleration mechanism and discharge chamber performance. Experimental investigations will include operating the test bed ion (TBI) engine as an EPA thruster and parametrically varying the thruster geometry and operating conditions to quantify the electrostatic plasma acceleration effect. The theoretical investigations will include the development of a discharge chamber model which describes the relationships between the engine size, plasma properties, and overall performance. For the EPA thruster to be a viable propulsion concept, overall thruster efficiencies approaching 30% with specific impulses approaching 1000 s must be achieved.

  19. Electrostatic space radiation shielding

    NASA Astrophysics Data System (ADS)

    Tripathi, Ram K.; Wilson, John W.; Youngquist, Robert C.

    2008-09-01

    For the success of NASA’s new vision for space exploration to Moon, Mars and beyond, exposures from the hazards of severe space radiation in deep space long duration missions is ‘a must solve’ problem. The payload penalty demands a very stringent requirement on the design of the spacecrafts for human deep space missions. The exploration beyond low Earth orbit (LEO) to enable routine access of space will require protection from the hazards of the accumulated exposures of space radiation, Galactic Cosmic Rays (GCR) and Solar Particle Events (SPE), and minimizing the production of secondary radiation is a great advantage. There is a need to look to new horizons for newer technologies. The present investigation revisits electrostatic active radiation shielding and explores the feasibility of using the electrostatic shielding in concert with the state-of-the-art materials shielding and protection technologies. The full space radiation environment has been used, for the first time, to explore the feasibility of electrostatic shielding. The goal is to repel enough positive charge ions so that they miss the spacecraft without attracting thermal electrons. Conclusions are drawn for the future directions of space radiation protection.

  20. Electrostatic supersolitons in three-species plasmas

    SciTech Connect

    Verheest, Frank; Hellberg, Manfred A.; Kourakis, Ioannis

    2013-01-15

    Superficially, electrostatic potential profiles of supersolitons look like those of traditional solitons. However, their electric field profiles are markedly different, having additional extrema on the wings of the standard bipolar structure. This new concept was recently pointed out in the literature for a plasma model with five species. Here, it is shown that electrostatic supersolitons are not an artefact of exotic, complicated plasma models, but can exist even in three-species plasmas and are likely to occur in space plasmas. Further, a methodology is given to delineate their existence domains in a systematic fashion by determining the specific limiting factors.

  1. Kelvin transformation and inverse multipoles in electrostatics

    NASA Astrophysics Data System (ADS)

    Amaral, R. L. P. G.; Ventura, O. S.; Lemos, N. A.

    2017-03-01

    The inversion in the sphere or Kelvin transformation, which exchanges the radial coordinate for its inverse, is used as a guide to relate distinct electrostatic problems with dual features. The exact solution of some nontrivial problems are obtained through the mapping from simple highly symmetric systems. In particular, the concept of multipole expansion is revisited from a point of view opposed to the usual one: the sources are distributed in a region far from the origin while the electrostatic potential is described at points close to it.

  2. Electrostatic effects on hyaluronic acid configuration

    NASA Astrophysics Data System (ADS)

    Berezney, John; Saleh, Omar

    2015-03-01

    In systems of polyelectrolytes, such as solutions of charged biopolymers, the electrostatic repulsion between charged monomers plays a dominant role in determining the molecular conformation. Altering the ionic strength of the solvent thus affects the structure of such a polymer. Capturing this electrostatically-driven structural dependence is important for understanding many biological systems. Here, we use single molecule manipulation experiments to collect force-extension behavior on hyaluronic acid (HA), a polyanion which is a major component of the extracellular matrix in all vertebrates. By measuring HA elasticity in a variety of salt conditions, we are able to directly assess the contribution of electrostatics to the chain's self-avoidance and local stiffness. Similar to recent results from our group on single-stranded nucleic acids, our data indicate that HA behaves as a swollen chain of electrostatic blobs, with blob size proportional to the solution Debye length. Our data indicate that the chain structure within the blob is not worm-like, likely due to long-range electrostatic interactions. We discuss potential models of this effect.

  3. Durability of Adhesively Bonded Structure

    DTIC Science & Technology

    1992-08-11

    frequently. Significant technology improvements have occurred In surface treatment, primers, joint analyses, adhesives and process controls. These have...clearly established the Initial cost savings potential for adhesive bonding. While this approach addresses the adequacy of joints early in service, there...processes with those changes which occur as a result of residual stress or cyclic loading in the adhesive joint 074-2R-bh 1 To fill a small part of this

  4. Adhesion Protein ApfA of Actinobacillus pleuropneumoniae Is Required for Pathogenesis and Is a Potential Target for Vaccine Development

    PubMed Central

    Zhou, Yang; Li, Lu; Chen, Zhaohui; Yuan, Hong; Chen, Huanchun

    2013-01-01

    Actinobacillus pleuropneumoniae is the etiologic agent of porcine pleuropneumonia, which causes serious economic losses in the pig farming industry worldwide. Due to a lack of knowledge of its virulence factors and a lack of effective vaccines able to confer cross-serotype protection, it is difficult to place this disease under control. By analyzing its genome sequences, we found that type IV fimbrial subunit protein ApfA is highly conserved among different serotypes of A. pleuropneumoniae. Our study shows that ApfA is an adhesin since its expression was greatly upregulated (135-fold) upon contact with host cells, while its deletion mutant attenuated its capability of adhesion. The inactivation of apfA dramatically reduced the ability of A. pleuropneumoniae to colonize mouse lung, suggesting that apfA is a virulence factor. Purified recombinant ApfA elicited an elevated humoral immune response and conferred robust protection against challenges with A. pleuropneumoniae serovar 1 strain 4074 and serovar 7 strain WF83 in mice. Importantly, the anti-ApfA serum conferred significant protection against both serovar 1 and serovar 7 in mice. These studies indicate that ApfA promotes virulence through attachment to host cells, and its immunogenicity renders it a promising novel subunit vaccine candidate against infection with A. pleuropneumoniae. PMID:23269417

  5. Folate deficiency and aberrant expression of cell adhesion molecule 1 are potential indicators of prognosis in laryngeal squamous cell carcinoma

    PubMed Central

    Chang, Hao; Ma, Min; Ma, Rui; Zhang, Chao; Zeng, Wei; Xing, Lu Qi

    2016-01-01

    The etiology of laryngeal squamous cell carcinoma (LSCC) has not yet been adequately examined. Therefore, the present study aimed to investigate the association between serum folate deficiency and abnormal expression of the cell adhesion molecule 1 (CADM1) protein in the progression of LSCC. Samples were collected from 60 patients with LSCC and 30 healthy people. Radioimmunoassays and immunohistochemical staining were performed to measure serum folate levels and CADM1 protein expression, respectively. The results demonstrated that CADM1 expression in LSCC specimens was significantly lower than in adjacent normal tissues (χ2=28.229, P<0.001), which was associated with histological differentiation and clinical stage (P=0.010 and 0.020, respectively). Levels of serum folate in patients with LSCC were significantly lower than those observed in healthy individuals (P=0.002). Furthermore, TSLCl expression and serum folate levels were positively correlated in LSCC (r=0.642, P=0.001). Thus, the present study determined that decreased CADM1 protein expression and low levels of serum folate were correlated with an increased severity of LSCC. PMID:28105160

  6. The electrochemical surface forces apparatus: the effect of surface roughness, electrostatic surface potentials, and anodic oxide growth on interaction forces, and friction between dissimilar surfaces in aqueous solutions.

    PubMed

    Valtiner, Markus; Banquy, Xavier; Kristiansen, Kai; Greene, George W; Israelachvili, Jacob N

    2012-09-11

    We present a newly designed electrochemical surface forces apparatus (EC-SFA) that allows control and measurement of surface potentials and interfacial electrochemical reactions with simultaneous measurement of normal interaction forces (with nN resolution), friction forces (with μN resolution), and distances (with Å resolution) between apposing surfaces. We describe three applications of the developed EC-SFA and discuss the wide-range of potential other applications. In particular, we describe measurements of (1) force-distance profiles between smooth and rough gold surfaces and apposing self-assembled monolayer-covered smooth mica surfaces; (2) the effective changing thickness of anodically growing oxide layers with Å-accuracy on rough and smooth surfaces; and (3) friction forces evolving at a metal-ceramic contact, all as a function of the applied electrochemical potential. Interaction forces between atomically smooth surfaces are well-described using DLVO theory and the Hogg-Healy-Fuerstenau approximation for electric double layer interactions between dissimilar surfaces, which unintuitively predicts the possibility of attractive double layer forces between dissimilar surfaces whose surface potentials have similar sign, and repulsive forces between surfaces whose surface potentials have opposite sign. Surface roughness of the gold electrodes leads to an additional exponentially repulsive force in the force-distance profiles that is qualitatively well described by an extended DLVO model that includes repulsive hydration and steric forces. Comparing the measured thickness of the anodic gold oxide layer and the charge consumed for generating this layer allowed the identification of its chemical structure as a hydrated Au(OH)(3) phase formed at the gold surface at high positive potentials. The EC-SFA allows, for the first time, one to look at complex long-term transient effects of dynamic processes (e.g., relaxation times), which are also reflected in friction

  7. Sundew adhesive: a naturally occurring hydrogel

    PubMed Central

    Huang, Yujian; Wang, Yongzhong; Sun, Leming; Agrawal, Richa; Zhang, Mingjun

    2015-01-01

    Bioadhesives have drawn increasing interest in recent years, owing to their eco-friendly, biocompatible and biodegradable nature. As a typical bioadhesive, sticky exudate observed on the stalked glands of sundew plants aids in the capture of insects and this viscoelastic adhesive has triggered extensive interests in revealing the implied adhesion mechanisms. Despite the significant progress that has been made, the structural traits of the sundew adhesive, especially the morphological characteristics in nanoscale, which may give rise to the viscous and elastic properties of this mucilage, remain unclear. Here, we show that the sundew adhesive is a naturally occurring hydrogel, consisting of nano-network architectures assembled with polysaccharides. The assembly process of the polysaccharides in this hydrogel is proposed to be driven by electrostatic interactions mediated with divalent cations. Negatively charged nanoparticles, with an average diameter of 231.9 ± 14.8 nm, are also obtained from this hydrogel and these nanoparticles are presumed to exert vital roles in the assembly of the nano-networks. Further characterization via atomic force microscopy indicates that the stretching deformation of the sundew adhesive is associated with the flexibility of its fibrous architectures. It is also observed that the adhesion strength of the sundew adhesive is susceptible to low temperatures. Both elasticity and adhesion strength of the sundew adhesive reduce in response to lowering the ambient temperature. The feasibility of applying sundew adhesive for tissue engineering is subsequently explored in this study. Results show that the fibrous scaffolds obtained from sundew adhesive are capable of increasing the adhesion of multiple types of cells, including fibroblast cells and smooth muscle cells, a property that results from the enhanced adsorption of serum proteins. In addition, in light of the weak cytotoxic activity exhibited by these scaffolds towards a variety of

  8. Relipidated tissue factor linked to collagen surfaces potentiates platelet adhesion and fibrin formation in a microfluidic model of vessel injury

    PubMed Central

    Colace, Thomas V.; Jobson, Jennielle; Diamond, Scott L.

    2011-01-01

    Microfluidic devices allow for the controlled perfusion of human or mouse blood over defined prothrombotic surfaces at venous and arterial shear rates. To mimic in vivo injuries such a plaque rupture, the need exists to link lipidated tissue factor (TF) to surface bound collagen fibers. Recombinant TF was relipidated in liposomes of phosphatidylserine/phosphatidylcholine/biotin-linked phosphatidylethanolamine (20:79:1 PS:PC:bPE molar ratio). Collagen was patterned in a 250-micron wide stripe and labeled with biotinylated anti-collagen antibody which was then bound with streptavidin, allowing the subsequent capture of the TF liposomes. To verify and detect the TF liposome-collagen assembly, individual molecular complexes of TF-factor VIIa on collagen were visualized using the Proximity Ligation Assay (PLA) to produce discretely localized fluorescent events that were strictly dependent on the presence of factor VIIa and primary antibodies against TF or factor VIIa. Perfusion for 450 sec (wall shear rate, 200 s−1) of corn trypsin inhibitor (CTI, a factor XIIa inhibitor) treated whole blood over the stripe of TF-collagen enhanced platelet adhesion by 30 ± 8% (p < 0.001) and produced measurable fibrin (>50-fold increase) as compared to surfaces lacking TF. PS:PC:bPE liposomes lacking TF resulted in no enhancement of platelet deposition. Essentially no fibrin was formed during perfusion over collagen surfaces or collagen surfaces with liposomes lacking TF despite the robust platelet deposition, indicating a lack of kinetically significant platelet-borne tissue factor in healthy donor blood. This study demonstrates a reliable approach to link functionally-active TF to collagen for microfluidic thrombosis studies. PMID:21902184

  9. Spacecraft Electrostatic Radiation Shielding

    NASA Technical Reports Server (NTRS)

    2008-01-01

    This project analyzed the feasibility of placing an electrostatic field around a spacecraft to provide a shield against radiation. The concept was originally proposed in the 1960s and tested on a spacecraft by the Soviet Union in the 1970s. Such tests and analyses showed that this concept is not only feasible but operational. The problem though is that most of this work was aimed at protection from 10- to 100-MeV radiation. We now appreciate that the real problem is 1- to 2-GeV radiation. So, the question is one of scaling, in both energy and size. Can electrostatic shielding be made to work at these high energy levels and can it protect an entire vehicle? After significant analysis and consideration, an electrostatic shield configuration was proposed. The selected architecture was a torus, charged to a high negative voltage, surrounding the vehicle, and a set of positively charged spheres. Van de Graaff generators were proposed as the mechanism to move charge from the vehicle to the torus to generate the fields necessary to protect the spacecraft. This design minimized complexity, residual charge, and structural forces and resolved several concerns raised during the internal critical review. But, it still is not clear if such a system is costeffective or feasible, even though several studies have indicated usefulness for radiation protection at energies lower than that of the galactic cosmic rays. Constructing such a system will require power supplies that can generate voltages 10 times that of the state of the art. Of more concern is the difficulty of maintaining the proper net charge on the entire structure and ensuring that its interaction with solar wind will not cause rapid discharge. Yet, if these concerns can be resolved, such a scheme may provide significant radiation shielding to future vehicles, without the excessive weight or complexity of other active shielding techniques.

  10. Electrostatically Driven Nanoballoon Actuator.

    PubMed

    Barzegar, Hamid Reza; Yan, Aiming; Coh, Sinisa; Gracia-Espino, Eduardo; Dunn, Gabriel; Wågberg, Thomas; Louie, Steven G; Cohen, Marvin L; Zettl, Alex

    2016-11-09

    We demonstrate an inflatable nanoballoon actuator based on geometrical transitions between the inflated (cylindrical) and collapsed (flattened) forms of a carbon nanotube. In situ transmission electron microscopy experiments employing a nanoelectromechanical manipulator show that a collapsed carbon nanotube can be reinflated by electrically charging the nanotube, thus realizing an electrostatically driven nanoballoon actuator. We find that the tube actuator can be reliably cycled with only modest control voltages (few volts) with no apparent wear or fatigue. A complementary theoretical analysis identifies critical parameters for nanotube nanoballoon actuation.

  11. Antagonistic properties of a natural product - Bicuculline with the gamma-aminobutyric acid receptor: Studied through electrostatic potential mapping, electronic and vibrational spectra using ab initio and density functional theory

    NASA Astrophysics Data System (ADS)

    Srivastava, Anubha; Tandon, Poonam; Jain, Sudha; Asthana, B. P.

    2011-12-01

    (+)-Bicuculline (hereinafter referred to as bicuculline), a phthalide isoquinoline alkaloid is of current interest as an antagonist of gamma-aminobutyric acid (GABA). Its inhibitor properties have been studied through molecular electrostatic potential (MEP) mapping of this molecule and GABA receptor. The hot site on the potential surface of bicuculline, which is also isosteric with GABA receptor, has been used to interpret the inhibitor property. A systematic quantum chemical study of the possible conformations, their relative stabilities, FT-Raman, FT-IR and UV-vis spectroscopic analysis of bicuculline has been reported. The optimized geometries, wavenumber and intensity of the vibrational bands of all the conformers of bicuculline have been calculated using ab initio Hartree-Fock (HF) and density functional theory (DFT) employing B3LYP functional and 6-311G(d,p) basis set. Mulliken atomic charges, HOMO-LUMO gap Δ E, ionization potential, dipole moments and total energy have also been obtained for the optimized geometries of both the molecules. TD-DFT method is used to calculate the electronic absorption parameters in gas phase as well as in solvent environment using integral equation formalism-polarizable continuum model (IEF-PCM) employing 6-31G basis set and the results thus obtained are compared with the UV absorption spectra. The combination of experimental and calculated results provides an insight into the structural and vibrational spectroscopic properties of bicuculline.

  12. Thermoelectric properties of electrostatically tunable antidot lattices

    NASA Astrophysics Data System (ADS)

    Goswami, Srijit; Siegert, Christoph; Shamim, Saquib; Pepper, Michael; Farrer, Ian; Ritchie, David A.; Ghosh, Arindam

    2010-09-01

    We report on the fabrication and characterization of a device which allows the formation of an antidot lattice (ADL) using only electrostatic gating. The antidot potential and Fermi energy of the system can be tuned independently. Well defined commensurability features in magnetoresistance as well as magnetothermopower are observed. We show that the thermopower can be used to efficiently map out the potential landscape of the ADL.

  13. Effect of adsorption time on the adhesion strength between salivary pellicle and human tooth enamel.

    PubMed

    Zhang, Y F; Zheng, J; Zheng, L; Zhou, Z R

    2015-02-01

    Salivary pellicle is a biofilm that is formed by the selective adsorption of salivary proteins. Almost all the functions of the salivary pellicle (lubricating properties, anti-caries properties, etc.) are closely associated with its adhesion strength to tooth surface. The objective of this study was to investigate the effect of adsorption time on the adhesion strength between salivary pellicle and human tooth enamel, aiming to understand what act as the determinant of the interfacial adhesion. In this study, human tooth enamel samples were immersed in human whole saliva in vitro to obtain a salivary pellicle on the surface of enamel. Immersion treatments lasting up to 1, 3, 10 and 60 min were conducted, respectively. Nano-scratch tests were conducted on the surface of enamel after different adsorption times. The wettability of enamel surface was measured through water contact angle. Results showed that the shear energy between salivary pellicle and enamel surface increased exponentially with the adsorption time. The adhesion force between salivary pellicle and bare enamel surface was more than twice that between salivary pellicle and salivary pellicle. It was found that both the wettability and zeta potential of enamel increased obviously after 1 min saliva-adsorption treatment, and then they almost kept stable as the adsorption time further increased. In summary, the adhesion strength between initial salivary pellicle and enamel surface was much higher than that between initial salivary pellicle and outer salivary pellicle. It seemed that electrostatic interaction contributed to the adhesion between the initial salivary pellicle and enamel surface, but not to the adhesion between the initial and outer salivary pellicle. The results would be helpful to extend the understanding of the adhesion mechanism of salivary pellicle and then to develop new artificial saliva and dental restorative materials.

  14. Streptococcus mutans and Streptococcus intermedius adhesion to fibronectin films are oppositely influenced by ionic strength.

    PubMed

    Busscher, Henk J; van de Belt-Gritter, Betsy; Dijkstra, Rene J B; Norde, Willem; van der Mei, Henny C

    2008-10-07

    Bacterial adhesion to protein-coated surfaces is mediated by an interplay of specific and nonspecific interactions. Although nonspecific interactions are ubiquitously present, little is known about the physicochemical mechanisms of specific interactions. The aim of this paper is to determine the influence of ionic strength on the adhesion of two streptococcal strains to fibronectin films. Streptococcus mutans LT11 and Streptococcus intermedius NCTC11324 both possess antigen I/II with the ability to bind fibronectin from solution, but S. intermedius binds approximately 20x less fibronectin than does the S. mutans strain under identical conditions. Both strains as well as fibronectin films are negatively charged in low ionic strength phosphate buffered saline (PBS, 10x diluted), but bacteria appear uncharged in high ionic strength PBS. Physicochemical modeling on the basis of overall cell surface properties (cell surface hydrophobicity and zeta potentials) demonstrates that both strains should favor adhesion to fibronectin films in a high ionic strength environment as compared to in a low ionic strength environment, where electrostatic repulsion between equally charged surfaces is dominant. Adhesion of S. intermedius to fibronectin films in a parallel plate flow chamber was completely in line with this modeling, while in addition atomic force microscopy (AFM) indicated stronger adhesion forces upon retraction between fibronectin-coated tips and the cell surfaces in high ionic strength PBS than in low ionic strength PBS. Thus, the dependence of the interaction on ionic strength is dominated by the overall negative charge on the interacting surfaces. Adhesion of S. mutans to fibronectin films, however, was completely at odds with theoretical modeling, and the strain adhered best in low ionic strength PBS. Moreover, AFM indicated weaker repulsive forces upon approach between fibronectin-coated tips and the cell surfaces in low ionic strength PBS than in high ionic

  15. Undamped electrostatic plasma waves

    SciTech Connect

    Valentini, F.; Perrone, D.; Veltri, P.; Califano, F.; Pegoraro, F.; Morrison, P. J.; O'Neil, T. M.

    2012-09-15

    Electrostatic waves in a collision-free unmagnetized plasma of electrons with fixed ions are investigated for electron equilibrium velocity distribution functions that deviate slightly from Maxwellian. Of interest are undamped waves that are the small amplitude limit of nonlinear excitations, such as electron acoustic waves (EAWs). A deviation consisting of a small plateau, a region with zero velocity derivative over a width that is a very small fraction of the electron thermal speed, is shown to give rise to new undamped modes, which here are named corner modes. The presence of the plateau turns off Landau damping and allows oscillations with phase speeds within the plateau. These undamped waves are obtained in a wide region of the (k,{omega}{sub R}) plane ({omega}{sub R} being the real part of the wave frequency and k the wavenumber), away from the well-known 'thumb curve' for Langmuir waves and EAWs based on the Maxwellian. Results of nonlinear Vlasov-Poisson simulations that corroborate the existence of these modes are described. It is also shown that deviations caused by fattening the tail of the distribution shift roots off of the thumb curve toward lower k-values and chopping the tail shifts them toward higher k-values. In addition, a rule of thumb is obtained for assessing how the existence of a plateau shifts roots off of the thumb curve. Suggestions are made for interpreting experimental observations of electrostatic waves, such as recent ones in nonneutral plasmas.

  16. Electrostatic Plasma Accelerator (EPA)

    NASA Technical Reports Server (NTRS)

    Brophy, John R.; Aston, Graeme

    1995-01-01

    The application of electric propulsion to communications satellites, however, has been limited to the use of hydrazine thrusters with electric heaters for thrust and specific impulse augmentation. These electrothermal thrusters operate at specific impulse levels of approximately 300 s with heater powers of about 500 W. Low power arcjets (1-3 kW) are currently being investigated as a way to increase specific impulse levels to approximately 500 s. Ion propulsion systems can easily produce specific impulses of 3000 s or greater, but have yet to be applied to communications satellites. The reasons most often given for not using ion propulsion systems are their high level of overall complexity, low thrust with long burn times, and the difficulty of integrating the propulsion system into existing commercial spacecraft busses. The Electrostatic Plasma Accelerator (EPA) is a thruster concept which promises specific impulse levels between low power arcjets and those of the ion engine while retaining the relative simplicity of the arcjet. The EPA thruster produces thrust through the electrostatic acceleration of a moderately dense plasma. No accelerating electrodes are used and the specific impulse is a direct function of the applied discharge voltage and the propellant atomic mass.

  17. Electrostatic Beneficiation of Coal

    SciTech Connect

    D. Lindquist; K. B. Tennal; M. K. Mazumder

    1998-10-29

    It was suggested in the proposal that small particles, due to low inertia, may not impact on the surfaces of the tribocharger. They would, thus, not receive charge and would not be beneficiated in the electrostatic separation. A milling process was proposed in which the small particles are stirred together with larger carrier beads producing the desired contact charge exchange. A force is necessary for removing the coal particles from the carrier beads. In copying machines electrostatic force is used to pull toner particles away horn iron carrier particles which are held back by magnetic force. Aerodynamic force is used in test instruments for measuring the charge to mass ratio on toners. A similar system of milling and removal is desired for use with the small coal particles. The carrier beads need to be made of copper rather than iron. This complicates the separation process since copper is non-magnetic. We are working on coating of iron beads with a layer of copper. Dr. Robert Engleken of Arkansas State University has supplied us with several test batches of copper-coated iron in the size range of -40 +70 mesh. ` We are currently testing whether the milling process used with the copper coated iron beads produces the desired charge on the coal particles.

  18. High-performance mussel-inspired adhesives of reduced complexity

    PubMed Central

    Ahn, B. Kollbe; Das, Saurabh; Linstadt, Roscoe; Kaufman, Yair; Martinez-Rodriguez, Nadine R.; Mirshafian, Razieh; Kesselman, Ellina; Talmon, Yeshayahu; Lipshutz, Bruce H.; Israelachvili, Jacob N.; Waite, J. Herbert

    2015-01-01

    Despite the recent progress in and demand for wet adhesives, practical underwater adhesion remains limited or non-existent for diverse applications. Translation of mussel-inspired wet adhesion typically entails catechol functionalization of polymers and/or polyelectrolytes, and solution processing of many complex components and steps that require optimization and stabilization. Here we reduced the complexity of a wet adhesive primer to synthetic low-molecular-weight catecholic zwitterionic surfactants that show very strong adhesion (∼50 mJ m−2) and retain the ability to coacervate. This catecholic zwitterion adheres to diverse surfaces and self-assembles into a molecularly smooth, thin (<4 nm) and strong glue layer. The catecholic zwitterion holds particular promise as an adhesive for nanofabrication. This study significantly simplifies bio-inspired themes for wet adhesion by combining catechol with hydrophobic and electrostatic functional groups in a small molecule. PMID:26478273

  19. High-performance mussel-inspired adhesives of reduced complexity.

    PubMed

    Ahn, B Kollbe; Das, Saurabh; Linstadt, Roscoe; Kaufman, Yair; Martinez-Rodriguez, Nadine R; Mirshafian, Razieh; Kesselman, Ellina; Talmon, Yeshayahu; Lipshutz, Bruce H; Israelachvili, Jacob N; Waite, J Herbert

    2015-10-19

    Despite the recent progress in and demand for wet adhesives, practical underwater adhesion remains limited or non-existent for diverse applications. Translation of mussel-inspired wet adhesion typically entails catechol functionalization of polymers and/or polyelectrolytes, and solution processing of many complex components and steps that require optimization and stabilization. Here we reduced the complexity of a wet adhesive primer to synthetic low-molecular-weight catecholic zwitterionic surfactants that show very strong adhesion (∼50 mJ m(-2)) and retain the ability to coacervate. This catecholic zwitterion adheres to diverse surfaces and self-assembles into a molecularly smooth, thin (<4 nm) and strong glue layer. The catecholic zwitterion holds particular promise as an adhesive for nanofabrication. This study significantly simplifies bio-inspired themes for wet adhesion by combining catechol with hydrophobic and electrostatic functional groups in a small molecule.

  20. High-performance mussel-inspired adhesives of reduced complexity

    NASA Astrophysics Data System (ADS)

    Ahn, B. Kollbe; Das, Saurabh; Linstadt, Roscoe; Kaufman, Yair; Martinez-Rodriguez, Nadine R.; Mirshafian, Razieh; Kesselman, Ellina; Talmon, Yeshayahu; Lipshutz, Bruce H.; Israelachvili, Jacob N.; Waite, J. Herbert

    2015-10-01

    Despite the recent progress in and demand for wet adhesives, practical underwater adhesion remains limited or non-existent for diverse applications. Translation of mussel-inspired wet adhesion typically entails catechol functionalization of polymers and/or polyelectrolytes, and solution processing of many complex components and steps that require optimization and stabilization. Here we reduced the complexity of a wet adhesive primer to synthetic low-molecular-weight catecholic zwitterionic surfactants that show very strong adhesion (~50 mJ m-2) and retain the ability to coacervate. This catecholic zwitterion adheres to diverse surfaces and self-assembles into a molecularly smooth, thin (<4 nm) and strong glue layer. The catecholic zwitterion holds particular promise as an adhesive for nanofabrication. This study significantly simplifies bio-inspired themes for wet adhesion by combining catechol with hydrophobic and electrostatic functional groups in a small molecule.

  1. ELECTROSTATIC MEMORY SYSTEM

    DOEpatents

    Chu, J.C.

    1958-09-23

    An improved electrostatic memory system is de scribed fer a digital computer wherein a plarality of storage tubes are adapted to operate in either of two possible modes. According to the present irvention, duplicate storage tubes are provided fur each denominational order of the several binary digits. A single discriminator system is provided between corresponding duplicate tubes to determine the character of the infurmation stored in each. If either tube produces the selected type signal, corresponding to binazy "1" in the preferred embodiment, a "1" is regenerated in both tubes. In one mode of operation each bit of information is stored in two corresponding tubes, while in the other mode of operation each bit is stored in only one tube in the conventional manner.

  2. MEMS electrostatic influence machines

    NASA Astrophysics Data System (ADS)

    Phu Le, Cuong; Halvorsen, Einar

    2016-11-01

    This paper analyses the possibility of MEMS electrostatic influence machines using electromechanical switches like the historical predecessors did two centuries ago. We find that a generator design relying entirely on standard silicon-on-insulator(SOI) micromachining is conceivable and analyze its performance by simulations. The concept appears preferable over comparable diode circuits due to its higher maximum energy, faster charging and low precharging voltage. A full electromechanical lumped-model including parasitic capacitances of the switches is built to capture the dynamic of the generator. Simulation results show that the output voltage can be exponentially bootstrapped from a very low precharging voltage so that otherwise inadequately small voltage differences or charge imbalances can be made useful.

  3. Virulence-related genes, adhesion and invasion of some Yersinia enterocolitica-like strains suggests its pathogenic potential.

    PubMed

    Imori, Priscilla F M; Passaglia, Jaqueline; Souza, Roberto A; Rocha, Lenaldo B; Falcão, Juliana P

    2017-03-01

    Yersina enterocolitica-like species have not been extensively studied regarding its pathogenic potential. This work aimed to assess the pathogenic potential of some Y. enterocolitica-like strains by evaluating the presence of virulence-related genes by PCR and their ability to adhere to and invade Caco-2 and HEp-2 cells. A total of 50 Y. frederiksenii, 55 Y. intermedia and 13 Y. kristensenii strains were studied. The strains contained the following genes: Y. frederiksenii, fepA(44%), fes(44%) and ystB(18%); Y. intermedia, ail(53%), fepA (35%), fepD(2%), fes(97%), hreP(2%), ystB(2%) and tccC(35%); Y. kristensenii, ail(62%), ystB(23%), fepA(77%), fepD(54%), fes(54%) and hreP(77%). Generally, the Y. enterocolitica-like strains had a reduced ability to adhere to and invade mammalian cells compared to the highly pathogenic Y. enterocolitica 8081. However, Y. kristensenii FCF410 and Y. frederiksenii FCF461 presented high invasion potentials in Caco-2 cells after five days of pre-incubation increased by 45- and 7.2-fold compared to Y. enterocolitica 8081, respectively; but, the ail gene was not detected in these strains. The presence of virulence-related genes in some of the Y. enterocolitica-like strains indicated their possible pathogenic potential. Moreover, the results suggest the existence of alternative virulence mechanisms and that the pathogenicity of Y. kristensenii and Y. frederiksenii may be strain-dependent.

  4. Electrostatic sampling of trace DNA from clothing.

    PubMed

    Zieger, Martin; Defaux, Priscille Merciani; Utz, Silvia

    2016-05-01

    During acts of physical aggression, offenders frequently come into contact with clothes of the victim, thereby leaving traces of DNA-bearing biological material on the garments. Since tape-lifting and swabbing, the currently established methods for non-destructive trace DNA sampling from clothing, both have their shortcomings in collection efficiency and handling, we thought about a new collection method for these challenging samples. Testing two readily available electrostatic devices for their potential to sample biological material from garments made of different fabrics, we found one of them, the electrostatic dust print lifter (DPL), to perform comparable to well-established sampling with wet cotton swabs. In simulated aggression scenarios, we had the same success rate for the establishment of single aggressor profiles, suitable for database submission, with both the DPL and wet swabbing. However, we lost a substantial amount of information with electrostatic sampling, since almost no mixed aggressor-victim profiles suitable for database entry could be established, compared to conventional swabbing. This study serves as a proof of principle for electrostatic DNA sampling from items of clothing. The technique still requires optimization before it might be used in real casework. But we are confident that in the future it could be an efficient and convenient contribution to the toolbox of forensic practitioners.

  5. Adhesion of gels by silica particle.

    PubMed

    Abe, Hidekazu; Hara, Yusuke; Maeda, Shingo; Hashimoto, Shuji

    2014-03-06

    In this study, a method for achieving adhesion between two positively charged gels with high mechanical strength was developed. By utilizing a silica particle dispersion as a binder, the gels easily adhered to each other and remained stable for up to 11 days when immersed in aqueous solution. The adhesion force between the two positively charged semi-interpenetrating network gels with the silica particle was measured to be up to approximately 20 kPa, which is around 10 times larger than that with a charged polymer-rich liquid as a cross-linker (approximately 1.5 kPa). It was demonstrated that the adhesion force was a result of two types of interactions: an electrostatic attractive force between the cationic gel surface and hydrogen bonding among the silica particles. In addition, it was shown that the adhesion force was dependent on solution pH, which was attributed to changes in the charge of the silica particles.

  6. Teaching Electrostatics in University Courses

    ERIC Educational Resources Information Center

    Hughes, J. F.

    1974-01-01

    Describes an optional course on applied electrostatics that was offered to electrical engineers in their final year. Topics included the determination of electric fields, nature of the charging process, static electricity in liquids, solid state processes, charged particle applications, and electrostatic ignition. (GS)

  7. Asymmetric electrostatic and hydrophobic-hydrophilic interaction forces between mica surfaces and silicone polymer thin films.

    PubMed

    Donaldson, Stephen H; Das, Saurabh; Gebbie, Matthew A; Rapp, Michael; Jones, Louis C; Roiter, Yuri; Koenig, Peter H; Gizaw, Yonas; Israelachvili, Jacob N

    2013-11-26

    We have synthesized model hydrophobic silicone thin films on gold surfaces by a two-step covalent grafting procedure. An amino-functionalized gold surface reacts with monoepoxy-terminated polydimethylsiloxane (PDMS) via a click reaction, resulting in a covalently attached nanoscale thin film of PDMS, and the click chemistry synthesis route provides great selectivity, reproducibility, and stability in the resulting model hydrophobic silicone thin films. The asymmetric interaction forces between the PDMS thin films and mica surfaces were measured with the surface forces apparatus in aqueous sodium chloride solutions. At an acidic pH of 3, attractive interactions are measured, resulting in instabilities during both approach (jump-in) and separation (jump-out from adhesive contact). Quantitative analysis of the results indicates that the Derjaguin-Landau-Verwey-Overbeek theory alone, i.e., the combination of electrostatic repulsion and van der Waals attraction, cannot fully describe the measured forces and that the additional measured adhesion is likely due to hydrophobic interactions. The surface interactions are highly pH-dependent, and a basic pH of 10 results in fully repulsive interactions at all distances, due to repulsive electrostatic and steric-hydration interactions, indicating that the PDMS is negatively charged at high pH. We describe an interaction potential with a parameter, known as the Hydra parameter, that can account for the extra attraction (low pH) due to hydrophobicity as well as the extra repulsion (high pH) due to hydrophilic (steric-hydration) interactions. The interaction potential is general and provides a quantitative measure of interfacial hydrophobicity/hydrophilicity for any set of interacting surfaces in aqueous solution.

  8. Antioxidative stress effect of epicatechin and catechin induced by Aβ25-35 in rats and use of the electrostatic potential and the Fukui function as a tool to elucidate specific sites of interaction.

    PubMed

    Cruz-González, Trinidad; Cortez-Torres, Estephania; Perez-Severiano, Francisca; Espinosa, Blanca; Guevara, Jorge; Perez-Benitez, Aarón; Melendez, Francisco J; Díaz, Alfonso; Ramírez, Ramsés E

    2016-10-01

    Alzheimer's disease (AD) is a neurodegenerative disorder caused by the aggregation of the amyloid-beta peptide (Aβ) in senile plaques and cerebral vasculature. The Aβ25-35 fraction has shown the most toxicity; its neurotoxic mechanisms are associated with the generation of oxidative stress and reactive astrogliosis that induce neuronal death and memory impairment. Studies indicate that pharmacological treatment with flavonoids reduces the rate of AD, in particular, it has been shown that antioxidants are compounds that could interact with this peptide due to their antioxidant proprieties. In this study, experimental and computational tools were used to calculate the molecular electrostatic potential and the Fukui function with the Gaussian 09 computational program, to predict the most reactive parts of these molecules and make the complex between Aβ25-35 and two flavonoids (catechin and epicatechin) in the absolute gas-phase, where a possible interaction between them was observed. This is important for understanding the Aβ25-35-Flavonoid (A-F) interaction as a therapeutic strategy to inhibit the neurotoxic effects that this peptide causes in AD, which currently is still considered an ambiguous process.

  9. ELECTROSTATICALLY ENHANCED BARRIER FILTER COLLECTION

    SciTech Connect

    John Erjavec; Michael D. Mann; Ryan Z. Knutson; Michael L. Swanson; Michael E. Collings

    2003-06-01

    This work was performed through the University of North Dakota (UND) Chemical Engineering Department with assistance from UND's Energy & Environmental Research Center. This research was undertaken in response to the U.S. Department of Energy Federal Technology Center Program Solicitation No. DE-PS26-99FT40479, Support of Advanced Coal Research at U.S. Universities and Colleges. Specifically, this research was in support of the UCR Core Program and addressees Topic 1, Improved Hot-Gas Contaminant and Particulate Removal Techniques, introducing an advanced design for particulate removal. Integrated gasification combined cycle (IGCC) offers the potential for very high efficiency and clean electric generation. In IGCC, the product gas from the gasifier needs to be cleaned of particulate matter to avoid erosion and high-temperature corrosion difficulties arising with the turbine blades. Current methods involve cooling the gases to {approx}100 C to condense alkalis and remove sulfur and particulates using conventional scrubber technology. This ''cool'' gas is then directed to a turbine for electric generation. While IGCC has the potential to reach efficiencies of over 50%, the current need to cool the product gas for cleaning prior to firing it in a turbine is keeping IGCC from reaching its full potential. The objective of the current project was to develop a highly reliable particulate collector system that can meet the most stringent turbine requirements and emission standards, can operate at temperatures above 1500 F, is applicable for use with all U.S. coals, is compatible with various sorbent injection schemes for sulfur and alkali control, can be integrated into a variety of configurations for both pressurized gasification and combustion, increases allowable face velocity to reduce filter system capital cost, and is cost-competitive with existing technologies. The collector being developed is a new concept in particulate control called electrostatically enhanced

  10. Adhesive plasters

    DOEpatents

    Holcombe, Jr., Cressie E.; Swain, Ronald L.; Banker, John G.; Edwards, Charlene C.

    1978-01-01

    Adhesive plaster compositions are provided by treating particles of Y.sub.2 O.sub.3, Eu.sub.2 O.sub.3, Gd.sub.2 O.sub.3 or Nd.sub.2 O.sub.3 with dilute acid solutions. The resulting compositions have been found to spontaneously harden into rigid reticulated masses resembling plaster of Paris. Upon heating, the hardened material is decomposed into the oxide, yet retains the reticulated rigid structure.

  11. Conservation and Role of Electrostatics in Thymidylate Synthase

    NASA Astrophysics Data System (ADS)

    Garg, Divita; Skouloubris, Stephane; Briffotaux, Julien; Myllykallio, Hannu; Wade, Rebecca C.

    2015-11-01

    Conservation of function across families of orthologous enzymes is generally accompanied by conservation of their active site electrostatic potentials. To study the electrostatic conservation in the highly conserved essential enzyme, thymidylate synthase (TS), we conducted a systematic species-based comparison of the electrostatic potential in the vicinity of its active site. Whereas the electrostatics of the active site of TS are generally well conserved, the TSs from minimal organisms do not conform to the overall trend. Since the genomes of minimal organisms have a high thymidine content compared to other organisms, the observation of non-conserved electrostatics was surprising. Analysis of the symbiotic relationship between minimal organisms and their hosts, and the genetic completeness of the thymidine synthesis pathway suggested that TS from the minimal organism Wigglesworthia glossinidia (W.g.b.) must be active. Four residues in the vicinity of the active site of Escherichia coli TS were mutated individually and simultaneously to mimic the electrostatics of W.g.b TS. The measured activities of the E. coli TS mutants imply that conservation of electrostatics in the region of the active site is important for the activity of TS, and suggest that the W.g.b. TS has the minimal activity necessary to support replication of its reduced genome.

  12. Yes-mediated phosphorylation of focal adhesion kinase at tyrosine 861 increases metastatic potential of prostate cancer cells.

    PubMed

    Chatterji, Tanushree; Varkaris, Andreas S; Parikh, Nila U; Song, Jian H; Cheng, Chien-Jui; Schweppe, Rebecca E; Alexander, Stephanie; Davis, John W; Troncoso, Patricia; Friedl, Peter; Kuang, Jian; Lin, Sue-Hwa; Gallick, Gary E

    2015-04-30

    To study the role of FAK signaling complexes in promoting metastatic properties of prostate cancer (PCa) cells, we selected stable, highly migratory variants, termed PC3 Mig-3 and DU145 Mig-3, from two well-characterized PCa cell lines, PC3 and DU145. These variants were not only increased migration and invasion in vitro, but were also more metastatic to lymph nodes following intraprostatic injection into nude mice. Both PC3 Mig-3 and DU145 Mig-3 were specifically increased in phosphorylation of FAK Y861. We therefore examined potential alterations in Src family kinases responsible for FAK phosphorylation and determined only Yes expression was increased. Overexpression of Yes in PC3 parental cells and src-/-fyn-/-yes-/- fibroblasts selectively increased FAK Y861 phosphorylation, and increased migration. Knockdown of Yes in PC3 Mig-3 cells decreased migration and decreased lymph node metastasis following orthotopic implantation of into nude mice. In human specimens, Yes expression was increased in lymph node metastases relative to paired primary tumors from the same patient, and increased pFAK Y861 expression in lymph node metastases correlated with poor prognosis. These results demonstrate a unique role for Yes in phosphorylation of FAK and in promoting PCa metastasis. Therefore, phosphorylated FAK Y861 and increased Yes expression may be predictive markers for PCa metastasis.

  13. An interpretation of electrostatic density shocks in space plasma

    SciTech Connect

    Shi Jiankui; Zhang Tielong; Torkar, Klaus; Liu Zhenxing

    2005-08-15

    A physical model of electrostatic shocks observed in space plasma is established by deriving the 'Sagdeev potential' from the magnetohydrodynamic equations in a cylindrical coordinate system. The results show that the electrostatic density shock and its corresponding solitary electric-field structure can develop from an ion acoustic wave or an ion cyclotron wave if the Mach number and the initial electric field satisfy some conditions. Some features of the shock wave are discussed. The result can be used to interpret the electrostatic shock observed in geospace plasma.

  14. Micromachined silicon electrostatic chuck

    DOEpatents

    Anderson, Robert A.; Seager, Carleton H.

    1996-01-01

    An electrostatic chuck is faced with a patterned silicon plate 11, created y micromachining a silicon wafer, which is attached to a metallic base plate 13. Direct electrical contact between the chuck face 15 (patterned silicon plate's surface) and the silicon wafer 17 it is intended to hold is prevented by a pattern of flat-topped silicon dioxide islands 19 that protrude less than 5 micrometers from the otherwise flat surface of the chuck face 15. The islands 19 may be formed in any shape. Islands may be about 10 micrometers in diameter or width and spaced about 100 micrometers apart. One or more concentric rings formed around the periphery of the area between the chuck face 15 and wafer 17 contain a low-pressure helium thermal-contact gas used to assist heat removal during plasma etching of a silicon wafer held by the chuck. The islands 19 are tall enough and close enough together to prevent silicon-to-silicon electrical contact in the space between the islands, and the islands occupy only a small fraction of the total area of the chuck face 15, typically 0.5 to 5 percent. The pattern of the islands 19, together with at least one hole 12 bored through the silicon veneer into the base plate, will provide sufficient gas-flow space to allow the distribution of the helium thermal-contact gas.

  15. Micromachined silicon electrostatic chuck

    DOEpatents

    Anderson, R.A.; Seager, C.H.

    1996-12-10

    An electrostatic chuck is faced with a patterned silicon plate, created by micromachining a silicon wafer, which is attached to a metallic base plate. Direct electrical contact between the chuck face (patterned silicon plate`s surface) and the silicon wafer it is intended to hold is prevented by a pattern of flat-topped silicon dioxide islands that protrude less than 5 micrometers from the otherwise flat surface of the chuck face. The islands may be formed in any shape. Islands may be about 10 micrometers in diameter or width and spaced about 100 micrometers apart. One or more concentric rings formed around the periphery of the area between the chuck face and wafer contain a low-pressure helium thermal-contact gas used to assist heat removal during plasma etching of a silicon wafer held by the chuck. The islands are tall enough and close enough together to prevent silicon-to-silicon electrical contact in the space between the islands, and the islands occupy only a small fraction of the total area of the chuck face, typically 0.5 to 5 percent. The pattern of the islands, together with at least one hole bored through the silicon veneer into the base plate, will provide sufficient gas-flow space to allow the distribution of the helium thermal-contact gas. 6 figs.

  16. Electrostatic drops in orbit

    NASA Astrophysics Data System (ADS)

    Rodriguez, Isabel J.; Schmidt, Erin; Weislogel, Mark M.; Pettit, Donald

    2016-11-01

    We present what we think are the first intentional electrostatic orbits in the near-weightless environment of a drop tower. Classical physics problems involving Coulombic forces in orbital mechanics have traditionally been confined to thought experiments due to practical terrestrial experimental limitations, namely, the preponderance of gravity. However, the use of a drop tower as an experimental platform can overcome this challenge for brief periods. We demonstrate methanol-water droplets in orbit around a variety of charged objects- some of which can be used to validate special cases of N-body systems. Footage collected via a high-speed camera is analyzed and orbital trajectories are compared with existing theoretical predictions. Droplets of diameters 0.5 to 2mm in a variety of obits are observed. Due to the repeatability of drop tower initial conditions and effective low-g environment, such experiments may be used to construct empirical analogues and confirm analyses toward the benefit of other fields including space and planetary science. NASA Cooperative Agreement NNX12A047A, Portland State LSAMP, Robert E. McNair Scholars Program.

  17. The Electrostatic Bell

    NASA Astrophysics Data System (ADS)

    Martrou, Guillaume; Leonetti, Marc

    2016-11-01

    An initially static fluid-fluid interface is known to become unstable under a strong electric field leading to jet instability, surface pattern and spout formation. Applying an electric field to an initial dripping mode accelerates the dripping rate and leads to a continuous jet mode. We show that those two different configurations, when applied to dielectric liquids, can lead to the same instability, the formation of an unexpected macroscopic fluid bell-shape of typical size few times the capillary length even if the needle is as small as 200 μm . The instability results from the competition between the dielectric and the gravity forces, reminiscent of the Taylor-Melcher mechanism. The study is performed on several fluids of various densities, permittivity and surface tension on a large range of electric field. We show that the transition is an imperfect subcritical bifurcation with its characteristic bottleneck effect (lag time). Finally, in the case of flow rate, we established a shape diagram with four domains corresponding to dripping, jetting, bridge and electrostatic bell.

  18. Biofilm formation and local electrostatic force characteristics of Escherichia coli O157:H7 observed by electrostatic force microscopy

    NASA Astrophysics Data System (ADS)

    Oh, Y. J.; Jo, W.; Yang, Y.; Park, S.

    2007-04-01

    The authors report growth media dependence of electrostatic force characteristics in Escherichia coli O157:H7 biofilm through local measurement by electrostatic force microscopy (EFM). The difference values of electrostatic interaction between the bacterial surface and the abiotic surface show an exponential decay behavior during biofilm development. In the EFM data, the biofilm in the low nutrient media shows a faster decay than the biofilm in the rich media. The surface potential in the bacterial cells was changed from 957to149mV. Local characterization of extracellular materials extracted from the bacteria reveals the progress of the biofilm formation and functional complexities.

  19. Valorization of solid wastes from chestnut industry processing: Extraction and optimization of polyphenols, tannins and ellagitannins and its potential for adhesives, cosmetic and pharmaceutical industry.

    PubMed

    Aires, Alfredo; Carvalho, Rosa; Saavedra, Maria José

    2016-02-01

    The aim of the current study was to evaluate the potential of chestnut peels to produce pomaces enhanced with tannins to be used in the formulations of wood adhesives, leather tanning or as natural antioxidants in food, cosmetic and pharmaceutical industry. An analytical procedure was planned as 2 factorial design to analyze the influence of solvent (water, Na2SO3 and NaOH at different concentrations of 1, 2, 4, and 8% in water) and extraction time (30, 60, and 120, 240, 480 and 960min) on extraction yield, pH, Stiasny index, and tannins. HPLC-diode array detector equipped with an ionization mass spectrophotometer was used to assess the polyphenol composition. Our results showed that both extraction properties and phytochemicals were significantly affected (P<0.001) by all independent factors. The main tannins identified were the hydrolyzable gallic acid, vescalagin castalagin and ellagic acid, and the condensed epigallocatechin, catechin and epicatechin. The solvent 1% Na2SO3 was more effective to extract the condensed tannins whilst hydrolyzable tannins were extracted efficiently by 1% NaOH. The multivariable analysis and the Pearson's correlation coefficients showed a direct association between Stiasny number and the average levels of condensed tannins.

  20. Stability, Nonlinearity and Reliability of Electrostatically Actuated MEMS Devices

    PubMed Central

    Zhang, Wen-Ming; Meng, Guang; Chen, Di

    2007-01-01

    Electrostatic micro-electro-mechanical system (MEMS) is a special branch with a wide range of applications in sensing and actuating devices in MEMS. This paper provides a survey and analysis of the electrostatic force of importance in MEMS, its physical model, scaling effect, stability, nonlinearity and reliability in detail. It is necessary to understand the effects of electrostatic forces in MEMS and then many phenomena of practical importance, such as pull-in instability and the effects of effective stiffness, dielectric charging, stress gradient, temperature on the pull-in voltage, nonlinear dynamic effects and reliability due to electrostatic forces occurred in MEMS can be explained scientifically, and consequently the great potential of MEMS technology could be explored effectively and utilized optimally. A simplified parallel-plate capacitor model is proposed to investigate the resonance response, inherent nonlinearity, stiffness softened effect and coupled nonlinear effect of the typical electrostatically actuated MEMS devices. Many failure modes and mechanisms and various methods and techniques, including materials selection, reasonable design and extending the controllable travel range used to analyze and reduce the failures are discussed in the electrostatically actuated MEMS devices. Numerical simulations and discussions indicate that the effects of instability, nonlinear characteristics and reliability subjected to electrostatic forces cannot be ignored and are in need of further investigation.

  1. Adhesion effects in contact interaction of solids

    NASA Astrophysics Data System (ADS)

    Goryacheva, Irina; Makhovskaya, Yulya

    2008-01-01

    An approach to solving problems of the interaction of axisymmetric elastic bodies in the presence of adhesion is developed. The different natures of adhesion, i.e. capillary adhesion, or molecular adhesion described by the Lennard-Jones potential are examined. The effect of additional loading of the interacting bodies outside the contact zone is also investigated. The approach is based on the representation of the pressure outside the contact zone arising from adhesion by a step function. The analytical solution is obtained and is used to analyze the influence of the form of the adhesion interaction potential, of the surface energy of interacting bodies or the films covering the bodies, their shapes (parabolic, higher power exponential function), volume of liquid in the meniscus, density of contact spots, of elastic modulus and the Poisson ratio on the characteristics of the interaction of the bodies in the presence of adhesion. To cite this article: I. Goryacheva, Y. Makhovskaya, C. R. Mecanique 336 (2008).

  2. Test progress on the electrostatic membrane reflector

    NASA Technical Reports Server (NTRS)

    Mihora, D. J.

    1981-01-01

    An extemely lightweight type of precision reflector antenna, being developed for potential deployment from the space shuttle, uses electrostatic forces to tension a thin membrane and form it into a concave reflector surface. The typical shuttle-deployed antenna would have a diameter of 100 meters and an RMS surface smoothness of 10 to 1 mm for operation at 1 to 10 GHz. NASA Langley Research Center built and is currently testing a subscale (16 foot diameter) model of the membrane reflector portion of such an antenna. Preliminary test results and principal factors affecting surface quality are addressed. Factors included are the effect of the perimeter boundary, splicing of the membrane, the long-scale smoothness of commercial membranes, and the spatial controllability of the membrane using voltage adjustments to alter the electrostatic pressure. Only readily available commercial membranes are considered.

  3. Electrostatic antenna space environment interaction study

    NASA Technical Reports Server (NTRS)

    Katz, I.

    1981-01-01

    The interactions of the electrostatic antenna with the space environment in both low Earth orbit and geosynchronous orbit are investigated. It is concluded that the electrostatically controlled membrane mirror is a viable concept for space applications. However, great care must be taken to enclose the high voltage electrodes in a Faraday cage structure to separate the high voltage region from the ambient plasma. For this reason, metallized cloth is not acceptable as a membrane material. Conventional spacecraft charging at geosynchronous orbit should not be a problem provided ancillary structures (such as booms) are given nonnegligible conductivity and adequate grounding. Power loss due to plasma electrons entering the high field region is a potentially serious problem. In low earth orbit any opening whatever in the Faraday cage is likely to produce an unacceptable power drain.

  4. Explosion safety in industrial electrostatics

    NASA Astrophysics Data System (ADS)

    Szabó, S. V.; Kiss, I.; Berta, I.

    2011-01-01

    Complicated industrial systems are often endangered by electrostatic hazards, both from atmospheric (lightning phenomenon, primary and secondary lightning protection) and industrial (technological problems caused by static charging and fire and explosion hazards.) According to the classical approach protective methods have to be used in order to remove electrostatic charging and to avoid damages, however no attempt to compute the risk before and after applying the protective method is made, relying instead on well-educated and practiced expertise. The Budapest School of Electrostatics - in close cooperation with industrial partners - develops new suitable solutions for probability based decision support (Static Control Up-to-date Technology, SCOUT) using soft computing methods. This new approach can be used to assess and audit existing systems and - using the predictive power of the models - to design and plan activities in industrial electrostatics.

  5. Computational Methods for Biomolecular Electrostatics

    PubMed Central

    Dong, Feng; Olsen, Brett; Baker, Nathan A.

    2008-01-01

    An understanding of intermolecular interactions is essential for insight into how cells develop, operate, communicate and control their activities. Such interactions include several components: contributions from linear, angular, and torsional forces in covalent bonds, van der Waals forces, as well as electrostatics. Among the various components of molecular interactions, electrostatics are of special importance because of their long range and their influence on polar or charged molecules, including water, aqueous ions, and amino or nucleic acids, which are some of the primary components of living systems. Electrostatics, therefore, play important roles in determining the structure, motion and function of a wide range of biological molecules. This chapter presents a brief overview of electrostatic interactions in cellular systems with a particular focus on how computational tools can be used to investigate these types of interactions. PMID:17964951

  6. Notch-Mediated Cell Adhesion

    PubMed Central

    Murata, Akihiko; Hayashi, Shin-Ichi

    2016-01-01

    Notch family members are generally recognized as signaling molecules that control various cellular responses in metazoan organisms. Early fly studies and our mammalian studies demonstrated that Notch family members are also cell adhesion molecules; however, information on the physiological roles of this function and its origin is limited. In this review, we discuss the potential present and ancestral roles of Notch-mediated cell adhesion in order to explore its origin and the initial roles of Notch family members dating back to metazoan evolution. We hypothesize that Notch family members may have initially emerged as cell adhesion molecules in order to mediate multicellularity in the last common ancestor of metazoan organisms. PMID:26784245

  7. Electrostatic prepregging of thermoplastic matrices

    NASA Technical Reports Server (NTRS)

    Muzzy, John D.; Varughese, Babu; Thammongkol, Vivan; Tincher, Wayne

    1989-01-01

    Thermoplastic towpregs of PEEK/AS-4, PEEK/S-2 glass and LaRC-TPI/AS-4, produced by electrostatic deposition of charged and fluidized polymer powders on spread continuous fiber tows, are described. Processing parameters for combining PEEK 150 powder with unsized 3k AS-4 carbon fiber are presented. The experimental results for PEEK 150/AS-4 reveal that electrostatic fluidized bed coating may be an economically attractive process for producing towpreg.

  8. A review of high-temperature adhesives

    NASA Technical Reports Server (NTRS)

    St.clair, A. K.; St.clair, T. L.

    1981-01-01

    The development of high temperature adhesives and polyphenylquinoxalines (PPQ) is reported. Thermoplastic polyimides and linear PPQ adhesive are shown to have potential for bonding both metals and composite structures. A nadic terminated addition polyimide adhesive, LARC-13, and an acetylene terminated phenylquinoxaline (ATPQ) were developed. Both of the addition type adhesives are shown to be more readily processable than linear materials but less thermooxidatively stable and more brittle. It is found that the addition type adhesives are able to perform, at elevated temperatures up to 595 C where linear systems fail thermoplastically.

  9. Adhesion and Cohesion

    PubMed Central

    von Fraunhofer, J. Anthony

    2012-01-01

    The phenomena of adhesion and cohesion are reviewed and discussed with particular reference to dentistry. This review considers the forces involved in cohesion and adhesion together with the mechanisms of adhesion and the underlying molecular processes involved in bonding of dissimilar materials. The forces involved in surface tension, surface wetting, chemical adhesion, dispersive adhesion, diffusive adhesion, and mechanical adhesion are reviewed in detail and examples relevant to adhesive dentistry and bonding are given. Substrate surface chemistry and its influence on adhesion, together with the properties of adhesive materials, are evaluated. The underlying mechanisms involved in adhesion failure are covered. The relevance of the adhesion zone and its importance with regard to adhesive dentistry and bonding to enamel and dentin is discussed. PMID:22505913

  10. Universal adhesives: the next evolution in adhesive dentistry?

    PubMed

    Alex, Gary

    2015-01-01

    Every so often a new material, technique, or technological breakthrough spurs a paradigm shift in the way dentistry is practiced. The development and evolution of reliable enamel and dentin bonding agents is one such example. Indeed, the so-called "cosmetic revolution" in dentistry blossomed in large part due to dramatic advances in adhesive technology. It is the ability to bond various materials in a reasonably predictable fashion to both enamel and dentin substrates that enables dentists to routinely place porcelain veneers, direct and indirect composites, and a plethora of other restorative and esthetic materials. In fact, the longevity and predictability of many (if not most) current restorative procedures is wholly predicated on the dentist's ability to bond various materials to tooth tissues. Adhesive systems have progressed from the largely ineffective systems of the 1970s and early 1980s to the relatively successful total- and self-etching systems of today. The latest players in the adhesive marketplace are the so-called "universal adhesives." In theory, these systems have the potential to significantly simplify and expedite adhesive protocols and may indeed represent the next evolution in adhesive dentistry. But what defines a universal system, and are all these new systems truly "universal" and everything they are claimed to be? This article will examine the origin, chemistry, strengths, weaknesses, and clinical relevance of this new genre of dental adhesives.

  11. The Electrostatic Environments of Mars and the Moon

    NASA Technical Reports Server (NTRS)

    Calle, Carlos I.

    2011-01-01

    The electrical activity present in the environment near the surfaces of Mars and the moon has very different origins and presents a challenge to manned and robotic planetary exploration missions. Mars is covered with a layer of dust that has been redistributed throughout the entire planet by global dust storms. Dust, levitated by these storms as well as by the frequent dust devils, is expected to be electrostatically charged due to the multiple grain collisions in the dust-laden atmosphere. Dust covering the surface of the moon is expected to be electrostatically charged due to the solar wind, cosmic rays, and the solar radiation itself through the photoelectric effect. Electrostatically charged dust has a large tendency to adhere to surfaces. NASA's Mars exploration rovers have shown that atmospheric dust falling on solar panels can decrease their efficiency to the point of rendering the rover unusable. And as the Apollo missions to the moon showed, lunar dust adhesion can hinder manned and unmanned lunar exploration activities. Taking advantage of the electrical activity on both planetary system bodies, dust removal technologies are now being developed that use electrostatic and dielectrophoretic forces to produce controlled dust motion. This paper presents a short review of the theoretical and semiempirical models that have been developed for the lunar and Martian electrical environments.

  12. Influence of captopril on the cellular uptake and toxic potential of microcystin-LR in non-hepatic adhesive cell lines.

    PubMed

    Teneva, Ivanka; Klaczkowska, Dorota; Batsalova, Tsvetelina; Kostova, Zhivka; Dzhambazov, Balik

    2016-03-01

    Microcystin-LR (MC-LR) is a toxin produced by various cyanobacterial strains. Its cytotoxicity is due to inhibition of the protein phosphatases PP1 and PP2A, resulting in hyperphosphorylation of a number of functional and cytoskeletal proteins. To penetrate through the plasma membrane, MC-LR needs specific transporters such the organic anion-transporting polypeptides (OATP) that are highly expressed on the hepatocytes. Hence, our goal was to investigate the role of the membrane transport proteins for the cytotoxic effect of MC-LR on adhesive cell lines different from hepatocytes. We have used three cell lines--A549 (human lung carcinoma), SK-Hep-1 (human liver adenocarcinoma), FL (human amniotic normal cells), and two inhibitors of the OATP (cyclosporine A and captopril). To examine the cytotoxic effect of MC-LR we applied MTT and Neutral Red assays. In addition, a fluorescent staining of the mitochondria by JC-1 was performed. A dose-dependent cytotoxic effect was observed for the three cell lines, as this effect was most pronounced in A549. No cytotoxicity was detected when the captopril was added 2 h before treatment of the cells with MC-LR. Addition of captopril to the cells 2 h after treatment with MC-LR leads to enhancement of the cytotoxic effect. Reduced mitochondrial membrane potential after treatment with MC-LR was detected in the three cell lines, compared to untreated control cells. Results from the NR-cytotoxicity assay indicated that MC-LR does not affect the lysosomes. Captopril is an effective inhibitor of both OATP influx membrane transport proteins and the P-gp efflux pumps involved in the transport of MC-LR. It protects the cells from toxic effects of the cyanotoxin MC-LR.

  13. Use of nano-sized clay crystallites to restore adhesion among tumor and aging stem cells - a molecular simulations approach

    PubMed Central

    Ahmed, Habib-ur-Rehman; Abduljauwad, Sahel N

    2016-01-01

    Adhesion of cells to the ECM is key to the regulation of cellular morphology, migration, proliferation, survival, and differentiation. The decrease in or loss of the cell’s ability of mutual adhesiveness has been considered as one of the specific abnormalities in the surface properties of malignant cells. A change in the association of plasma membrane with cytoskeletal structures also seems to have a close relation with these abnormalities. Similar to the role of adhesions in tumor cells, stem cells’ self-renewal is also tightly controlled by the concerted action of stem cell-intrinsic factors and signals within the niche. This study has demonstrated through molecular simulations the potential use of smectite (Na-montmorillonite) clay crystallites to create adhesions among tumor and stem cells. High electrostatic energies and cohesive energy densities measured in the simulations after the sorption of clay crystallites on cell-cell and cell-ECM complexes validate the concept of using these crystallites for the purposes. As results of this study are quite promising and clay crystallites could be considered as an option to restore adhesions in tumor and stem cells, other confirmatory tests and live cell culture studies are in process for the final validation. PMID:28078181

  14. Colloid adhesive parameters for chemical heterogeneous porous media

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A simple modeling approach was developed to calculate colloid adhesive parameters for chemically heterogeneous porous media. The area of the zone of electrostatic influence between a colloid and solid-water interface (Az) was discretized into a number of equally sized grid cells to capture chemical...

  15. Engineering scale electrostatic enclosure demonstration

    SciTech Connect

    Meyer, L.C.

    1993-09-01

    This report presents results from an engineering scale electrostatic enclosure demonstration test. The electrostatic enclosure is part of an overall in-depth contamination control strategy for transuranic (TRU) waste recovery operations. TRU contaminants include small particles of plutonium compounds associated with defense-related waste recovery operations. Demonstration test items consisted of an outer Perma-con enclosure, an inner tent enclosure, and a ventilation system test section for testing electrostatic curtain devices. Three interchangeable test fixtures that could remove plutonium from the contaminated dust were tested in the test section. These were an electret filter, a CRT as an electrostatic field source, and an electrically charged parallel plate separator. Enclosure materials tested included polyethylene, anti-static construction fabric, and stainless steel. The soil size distribution was determined using an eight stage cascade impactor. Photographs of particles containing plutonium were obtained with a scanning electron microscope (SEM). The SEM also provided a second method of getting the size distribution. The amount of plutonium removed from the aerosol by the electrostatic devices was determined by radiochemistry from input and output aerosol samplers. The inner and outer enclosures performed adequately for plutonium handling operations and could be used for full scale operations.

  16. Echinoderm adhesive secretions: from experimental characterization to biotechnological applications.

    PubMed

    Flammang, P; Santos, R; Haesaerts, D

    2005-01-01

    Adhesion is a way of life in echinoderms. Indeed, all the species belonging to this phylum use adhesive secretions extensively for various vital functions. According to the species or to the developmental stage considered, different adhesive systems may be recognized. (1) The tube feet or podia are organs involved in attachment to the substratum, locomotion, feeding or burrowing. Their temporary adhesion relies on a duo-gland adhesive system resorting to both adhesive and de-adhesive secretions. (2) The larval adhesive organs allow temporary attachment of larvae during settlement and strong fixation during metamorphosis. (3) The Cuvierian tubules are sticky defence organs occurring in some holothuroid species. Their efficacy is based on the instantaneous release of a quick-setting adhesive. All these systems rely on different types of adhesion and therefore differ in the way they operate, in their structure and in the composition of their adhesive. In addition to fundamental interests in echinoderm bioadhesives, a substantial impetus behind understanding these adhesives are the potential technological applications that can be derived from their knowledge. These applications cover two broad fields of applied research: design of water-resistant adhesives and development of new antifouling strategies. In this context, echinoderm adhesives could offer novel features or performance characteristics for biotechnological applications. For example, the rapidly attaching adhesive of Cuvierian tubules, the releasable adhesive of tube feet or the powerful adhesive of asteroid larvae could each be useful to address particular bioadhesion problems.

  17. Miniature Bipolar Electrostatic Ion Thruster

    NASA Technical Reports Server (NTRS)

    Hartley, Frank T.

    2006-01-01

    The figure presents a concept of a bipolar miniature electrostatic ion thruster for maneuvering a small spacecraft. The ionization device in the proposed thruster would be a 0.1-micron-thick dielectric membrane with metal electrodes on both sides. Small conical holes would be micromachined through the membrane and electrodes. An electric potential of the order of a volt applied between the membrane electrodes would give rise to an electric field of the order of several mega-volts per meter in the submicron gap between the electrodes. An electric field of this magnitude would be sufficient to ionize all the molecules that enter the holes. In a thruster-based on this concept, one or more propellant gases would be introduced into such a membrane ionizer. Unlike in larger prior ion thrusters, all of the propellant molecules would be ionized. This thruster would be capable of bipolar operation. There would be two accelerator grids - one located forward and one located aft of the membrane ionizer. In one mode of operation, which one could denote the forward mode, positive ions leaving the ionizer on the backside would be accelerated to high momentum by an electric field between the ionizer and an accelerator grid. Electrons leaving the ionizer on the front side would be ejected into free space by a smaller accelerating field. The equality of the ion and electron currents would eliminate the need for an additional electron- or ion-emitting device to keep the spacecraft charge-neutral. In another mode of operation, which could denote the reverse mode, the polarities of the voltages applied to the accelerator grids and to the electrodes of the membrane ionizer would be the reverse of those of the forward mode. The reversal of electric fields would cause the ion and electrons to be ejected in the reverse of their forward mode directions, thereby giving rise to thrust in the direction opposite that of the forward mode.

  18. Proteomic dataset of the sea urchin Paracentrotus lividus adhesive organs and secreted adhesive

    PubMed Central

    Lebesgue, Nicolas; da Costa, Gonçalo; Ribeiro, Raquel Mesquita; Ribeiro-Silva, Cristina; Martins, Gabriel G.; Matranga, Valeria; Scholten, Arjen; Cordeiro, Carlos; Heck, Albert J.R.; Santos, Romana

    2016-01-01

    Sea urchins have specialized adhesive organs called tube feet, which mediate strong but reversible adhesion. Tube feet are composed by a disc, producing adhesive and de-adhesive secretions for substratum attachment, and a stem for movement. After detachment the secreted adhesive remains bound to the substratum as a footprint. Recently, a label-free quantitative proteomic approach coupled with the latest mass-spectrometry technology was used to analyze the differential proteome of Paracentrotus lividus adhesive organ, comparing protein expression levels in the tube feet adhesive part (the disc) versus the non-adhesive part (the stem), and also to profile the proteome of the secreted adhesive (glue). This data article contains complementary figures and results related to the research article “Deciphering the molecular mechanisms underlying sea urchin reversible adhesion: a quantitative proteomics approach” (Lebesgue et al., 2016) [1]. Here we provide a dataset of 1384 non-redundant proteins, their fragmented peptides and expression levels, resultant from the analysis of the tube feet differential proteome. Of these, 163 highly over-expressed tube feet disc proteins (>3-fold), likely representing the most relevant proteins for sea urchin reversible adhesion, were further annotated in order to determine the potential functions. In addition, we provide a dataset of 611 non-redundant proteins identified in the secreted adhesive proteome, as well as their functional annotation and grouping in 5 major protein groups related with adhesive exocytosis, and microbial protection. This list was further analyzed to identify the most abundant protein groups and pinpoint putative adhesive proteins, such as Nectin, the most abundant adhesive protein in sea urchin glue. The obtained data uncover the key proteins involved in sea urchins reversible adhesion, representing a step forward to the development of new wet-effective bio-inspired adhesives. PMID:27182547

  19. Proteomic dataset of the sea urchin Paracentrotus lividus adhesive organs and secreted adhesive.

    PubMed

    Lebesgue, Nicolas; da Costa, Gonçalo; Ribeiro, Raquel Mesquita; Ribeiro-Silva, Cristina; Martins, Gabriel G; Matranga, Valeria; Scholten, Arjen; Cordeiro, Carlos; Heck, Albert J R; Santos, Romana

    2016-06-01

    Sea urchins have specialized adhesive organs called tube feet, which mediate strong but reversible adhesion. Tube feet are composed by a disc, producing adhesive and de-adhesive secretions for substratum attachment, and a stem for movement. After detachment the secreted adhesive remains bound to the substratum as a footprint. Recently, a label-free quantitative proteomic approach coupled with the latest mass-spectrometry technology was used to analyze the differential proteome of Paracentrotus lividus adhesive organ, comparing protein expression levels in the tube feet adhesive part (the disc) versus the non-adhesive part (the stem), and also to profile the proteome of the secreted adhesive (glue). This data article contains complementary figures and results related to the research article "Deciphering the molecular mechanisms underlying sea urchin reversible adhesion: a quantitative proteomics approach" (Lebesgue et al., 2016) [1]. Here we provide a dataset of 1384 non-redundant proteins, their fragmented peptides and expression levels, resultant from the analysis of the tube feet differential proteome. Of these, 163 highly over-expressed tube feet disc proteins (>3-fold), likely representing the most relevant proteins for sea urchin reversible adhesion, were further annotated in order to determine the potential functions. In addition, we provide a dataset of 611 non-redundant proteins identified in the secreted adhesive proteome, as well as their functional annotation and grouping in 5 major protein groups related with adhesive exocytosis, and microbial protection. This list was further analyzed to identify the most abundant protein groups and pinpoint putative adhesive proteins, such as Nectin, the most abundant adhesive protein in sea urchin glue. The obtained data uncover the key proteins involved in sea urchins reversible adhesion, representing a step forward to the development of new wet-effective bio-inspired adhesives.

  20. SPARCLE: Electrostatic Tool for Lunar Dust Control

    SciTech Connect

    Clark, P. E.; Curtis, S. A.; Minetto, F.; Cheung, C. Y.; Keller, J. F.; Moore, M.; Calle, C. I.

    2009-03-16

    Successful exploration of most planetary surfaces, with their impact-generated dusty regoliths, will depend on the capabilities to keep surfaces free of the dust which could compromise performance and to collect dust for characterization. Solving the dust problem is essential before we return to the Moon. During the Apollo missions, the discovery was made that regolith fines, or dust, behaved like abrasive velcro, coating surfaces, clogging mechanisms, and making movement progressively more difficult as it was mechanically stirred up during surface operations, and abrading surfaces, including spacesuits, when attempts were made to remove it manually. In addition, some of the astronauts experienced breathing difficulties when exposed to dust that got into the crew compartment. The successful strategy will deal with dust dynamics resulting from interaction between mechanical and electrostatic forces. Here we will describe the surface properties of dust particles, the basis for their behavior, and an electrostatically-based approach and methodology for addressing this issue confirmed by our preliminary results. Our device concept utilizes a focused electron beam to control the electrostatic potential of the surface. A plate of the opposite potential is then used to induce dust migration in the presence of an electrical field. Our goal is a compact device of <5 kg mass and using <5 watts of power to be operational in <5 years with heritage from ionic sweepers for active spacecraft potential control (e.g., on POLAR). Rovers could be fitted with devices that could harness the removal of dust for sampling as part of the extended exploration process on Mercury, Mars, asteroids or outer solar system satellites, as well as the Moon.

  1. Electrostatic Surface Characterization by Scanning Probe Microscopy.

    NASA Astrophysics Data System (ADS)

    Leng, Yaojian

    1995-01-01

    The electrostatic properties of surfaces are important in biological, polymer and semiconductor physics. Several newly developed scanning probe microscopies can provide nanometer scale characterization of these surfaces. In the course of this work, an Electrostatic Force Microscope (EFM) and a Kelvin Probe Force Microscope (KPFM) have been built using interferometric force detection. An EFM is a modified noncontact mode Atomic Force Microscope, capable of simultaneously measuring surface topography, surface charge or surface potential, and capacitance. A KPFM is similar to the classical Kelvin method in measuring surface potential, only in this case, forces are detected instead of currents. A 10^{-4} A/surdHz displacement detection sensitivity has been achieved. A 200 A spatial resolution and a sub-mV electrostatic potential sensitivity have been demonstrated. The capability of the EFM to map charge and dielectric variations on biological and polymeric surfaces has been demonstrated. Studies have been made on red blood cells, modified Teflon FEP films, and contact lens materials. A quantitative method to measure surface charge density on a nanometer scale has been established. The redistribution of mobile surface ions has been visualized for the first time by the EFM on a submicron scale. It has been shown that the drift in the saturation current observed on the open gate field effect transistor is due to the migration of mobile surface ions under lateral fields. Atomic ordering in GaInP, controlled either by growth temperature or by substrate misorientation, has been studied by the KPFM both in cross section and on the growth plane. It is shown that KPFM is capable of distinguishing ordered GaInP from disordered GaInP. The contrast is observed to depend on the applied ac amplitude used in the measurement. The experiments indicate that ordering in GaInP modifies the density and/or lifetime of the surface states.

  2. Electrostatically actuatable light modulating device

    DOEpatents

    Koehler, Dale R.

    1991-01-01

    The electrostatically actuatable light modulator utilizes an opaque substrate plate patterned with an array of aperture cells, the cells comprised of physically positionable dielectric shutters and electrostatic actuators. With incorporation of a light source and a viewing screen, a projection display system is effected. Inclusion of a color filter array aligned with the aperture cells accomplishes a color display. The system is realized in terms of a silicon based manufacturing technology allowing fabrication of a high resolution capability in a physically small device which with the utilization of included magnification optics allows both large and small projection displays.

  3. Polarizable multipolar electrostatics for cholesterol

    NASA Astrophysics Data System (ADS)

    Fletcher, Timothy L.; Popelier, Paul L. A.

    2016-08-01

    FFLUX is a novel force field under development for biomolecular modelling, and is based on topological atoms and the machine learning method kriging. Successful kriging models have been obtained for realistic electrostatics of amino acids, small peptides, and some carbohydrates but here, for the first time, we construct kriging models for a sizeable ligand of great importance, which is cholesterol. Cholesterol's mean total (internal) electrostatic energy prediction error amounts to 3.9 kJ mol-1, which pleasingly falls below the threshold of 1 kcal mol-1 often cited for accurate biomolecular modelling. We present a detailed analysis of the error distributions.

  4. Fabrication of nanoscale electrostatic lenses

    NASA Astrophysics Data System (ADS)

    Sinno, I.; Sanz-Velasco, A.; Kang, S.; Jansen, H.; Olsson, E.; Enoksson, P.; Svensson, K.

    2010-09-01

    The fabrication of cylindrical multi-element electrostatic lenses at the nanoscale presents a challenge; they are high-aspect-ratio structures that should be rotationally symmetric, well aligned and freestanding, with smooth edges and flat, clean surfaces. In this paper, we present the fabrication results of a non-conventional process, which uses a combination of focused gallium ion-beam milling and hydrofluoric acid vapor etching. This process makes it possible to fabricate nanoscale electrostatic lenses down to 140 nm in aperture diameter and 4.2 µm in column length, with a superior control of the geometry as compared to conventional lithography-based techniques.

  5. Charge sniffer for electrostatics demonstrations

    NASA Astrophysics Data System (ADS)

    Dinca, Mihai P.

    2011-02-01

    An electronic electroscope with a special design for demonstrations and experiments on static electricity is described. It operates as an electric charge sniffer by detecting slightly charged objects when they are brought to the front of its sensing electrode. The sniffer has the advantage of combining high directional sensitivity with a logarithmic bar display. It allows for the identification of electric charge polarity during charge separation by friction, peeling, electrostatic induction, batteries, or secondary coils of power transformers. Other experiments in electrostatics, such as observing the electric field of an oscillating dipole and the distance dependence of the electric field generated by simple charge configurations, are also described.

  6. Plasticizers Increase Adhesion of the Deteriogenic Fungus Aureobasidium pullulans to Polyvinyl Chloride

    PubMed Central

    Webb, Jeremy S.; Van der Mei, Henny C.; Nixon, Marianne; Eastwood, Ian M.; Greenhalgh, Malcolm; Read, Simon J.; Robson, Geoffrey D.; Handley, Pauline S.

    1999-01-01

    Initial adhesion of fungi to plasticized polyvinyl chloride (pPVC) may determine subsequent colonization and biodeterioration processes. The deteriogenic fungus Aureobasidium pullulans was used to investigate the physicochemical nature of adhesion to both unplasticized PVC (uPVC) and pPVC containing the plasticizers dioctyl phthalate (DOP) and dioctyl adipate (DOA). A quantitative adhesion assay using image analysis identified fundamental differences in the mechanism of adhesion of A. pullulans blastospores to these substrata. Adhesion to pPVC was greater than that to uPVC by a maximum of 280% after a 4-h incubation with 108 blastospores ml−1. That plasticizers enhance adhesion to PVC was confirmed by incorporating a dispersion of both DOA and DOP into the blastospore suspension. Adhesion to uPVC was increased by up to 308% in the presence of the dispersed plasticizers. Hydrophobic interactions were found to dominate adhesion to uPVC because (i) a strong positive correlation was observed between substratum hydrophobicity (measured by using a dynamic contact angle analyzer) and adhesion to a range of unplasticized polymers including uPVC, and (ii) neither the pH nor the electrolyte concentration of the suspension buffer, both of which influence electrostatic interactions, affected adhesion to uPVC. In contrast, adhesion to pPVC is principally controlled by electrostatic interactions. Enhanced adhesion to pPVC occurred despite a relative reduction of 13° in the water contact angle of pPVC compared to that of uPVC. Furthermore, adhesion to pPVC was strongly dependent on both the pH and electrolyte concentration of the suspension medium, reaching maximum levels at pH 8 and with an electrolyte concentration of 10 mM NaCl. Plasticization with DOP and DOA therefore increases adhesion of A. pullulans blastospores to pPVC through an interaction mediated by electrostatic forces. PMID:10427051

  7. Evaluation of a lipopeptide biosurfactant from Bacillus natto TK-1 as a potential source of anti-adhesive, antimicrobial and antitumor activities

    PubMed Central

    Cao, Xiao-Hong; Liao, Zhen-Yu; Wang, Chun-Ling; Yang, Wen-Yan; Lu, Mei-Fang

    2009-01-01

    A lipopeptide biosurfactant produced by Bacillus natto TK-1 has a strong surface activity. The biosurfactant was found to be an anti-adhesive agent against several bacterial strains, and also showed a broad spectrum of antimicrobial activity. The biosurfactant induced a significant reduction in tumor cells viability in a dose-dependent manner. PMID:24031375

  8. Measurement of exciton correlations using electrostatic lattices

    NASA Astrophysics Data System (ADS)

    Remeika, M.; Leonard, J. R.; Dorow, C. J.; Fogler, M. M.; Butov, L. V.; Hanson, M.; Gossard, A. C.

    2015-09-01

    We present a method for determining correlations in a gas of indirect excitons in a semiconductor quantum well structure. The method involves subjecting the excitons to a periodic electrostatic potential that causes modulations of the exciton density and photoluminescence (PL). Experimentally measured amplitudes of energy and intensity modulations of exciton PL serve as an input to a theoretical estimate of the exciton correlation parameter and temperature. We also present a proof-of-principle demonstration of the method for determining the correlation parameter and discuss how its accuracy can be improved.

  9. Turbulence in electrostatic ion acoustic shocks

    NASA Technical Reports Server (NTRS)

    Means, R. W.; Coroniti, F. V.; Wong, A. Y.; White, R. B.

    1973-01-01

    Three types of collisionless electrostatic ion acoustic shocks are investigated using a double plasma (DP) device: (1) laminar shocks; (2) small amplitude turbulent shocks in which the turbulence is confined to be upstream of the shock potential jump; and (3) large amplitude turbulent shocks in which the wave turbulence occurs throughout the shock transition. The wave turbulence is generated by ions which are reflected from the shock potential; linear theory spatial growth increments agree with experimental values. The experimental relationship between the shock Mach number and the shock potential is shown to be inconsistent with theoretical shock models which assume that the electrons are isothermal. Theoretical calculations which assume a trapped electron equation of a state and a turbulently flattened velocity distrubution function for the reflected ions yields a Mach number vs potential relationship in agreement with experiment.

  10. Ion beam probing of electrostatic fields

    NASA Technical Reports Server (NTRS)

    Persson, H.

    1979-01-01

    The determination of a cylindrically symmetric, time-independent electrostatic potential V in a magnetic field B with the same symmetry by measurements of the deflection of a primary beam of ions is analyzed and substantiated by examples. Special attention is given to the requirements on canonical angular momentum and total energy set by an arbitrary, nonmonotone V, to scaling laws obtained by normalization, and to the analogy with ionospheric sounding. The inversion procedure with the Abel analysis of an equivalent problem with a one-dimensional fictitious potential is used in a numerical experiment with application to the NASA Lewis Modified Penning Discharge. The determination of V from a study of secondary beams of ions with increased charge produced by hot plasma electrons is also analyzed, both from a general point of view and with application to the NASA Lewis SUMMA experiment. Simple formulas and geometrical constructions are given for the minimum energy necessary to reach the axis, the whole plasma, and any point in the magnetic field. The common, simplifying assumption that V is a small perturbation is critically and constructively analyzed; an iteration scheme for successively correcting the orbits and points of ionization for the electrostatic potential is suggested.

  11. Analyzing electrostatic induced damage risk to reticles with an in situ e-reticle system

    NASA Astrophysics Data System (ADS)

    Tu, Richard; Sebald, Thomas

    2009-12-01

    E-Reticle system is an electrostatic field test device, which has the form factor of a conventional six inch quartz production reticle. The E-Reticle was used to assess the ESD damage risks in a mask cleaning tool. Test results indicate that a reticle may see higher than ITRS recommended electrostatic potential specifications when mechanical operations and cold DIW rinse start and in progress, hence seeing increased probability of electrostatic induced damages.

  12. Bridging implicit and explicit solvent approaches for membrane electrostatics.

    PubMed Central

    Lin, Jung-Hsin; Baker, Nathan A; McCammon, J Andrew

    2002-01-01

    Conformations of a zwitterionic bilayer were sampled from a molecular dynamics simulation and their electrostatic properties analyzed by solution of the Poisson equation. These traditionally implicit electrostatic calculations were performed in the presence of varying amounts of explicit solvent to assess the magnitude of error introduced by a uniform dielectric description of water surrounding the bilayer. It was observed that membrane dipole potential calculations in the presence of explicit water were significantly different than wholly implicit solvent calculations with the calculated dipole potential converging to a reasonable value when four or more hydration layers were included explicitly. PMID:12202363

  13. Smart Actuators and Adhesives for Reconfigurable Matter.

    PubMed

    Ko, Hyunhyub; Javey, Ali

    2017-03-06

    based on enhanced solvent diffusion rate through the porous or structured hydrogel materials, electrostatic repulsion between cofacial electrolyte nanosheets, and photothermal actuation are discussed. Second, the ability to reconfigure programmable matters into a variety of complex structures is beneficial for the use of reconfigurable matter in diverse applications. For the reconfiguration of planar 2D structures into complex 3D structures, asymmetric and multidirectional stress should be applied. In this regard, local hinges with stimuli-responsive stiffness, multilayer laminations with different responsiveness in individual layers, and origami and kirigami assembly approaches are reviewed. Third, multistimuli responsiveness will be required for the efficient reconfiguration of complex programmable matter in response to user-defined stimulus under different chemical and physical environments. In addition, with multistimuli responsiveness, the reconfigured shape can be temporarily affixed by one signal and disassembled by another signal at a user-defined location and time. Photoactuation depending on the chirality of carbon nanotubes and composite gels with different responsiveness will be discussed. Finally, the development of smart adhesives with on-demand adhesion strength is critically required to maintain the robust reconfigurable shapes and for the switching on/off of the binding between components or with target objects. Among various connectors and adhesives, thermoresponsive nanowire connectors, octopus-inspired smart adhesives, and elastomeric tiles with soft joints are described due to their potential applications in joints of deformable 3D structures and smart gripping systems.

  14. Resistivity Problems in Electrostatic Precipitation

    ERIC Educational Resources Information Center

    White, Harry J.

    1974-01-01

    The process of electrostatic precipitation has ever-increasing application in more efficient collection of fine particles from industrial air emissions. This article details a large number of new developments in the field. The emphasis is on high resistivity particles which are a common cause of poor precipitator performance. (LS)

  15. Defining protein electrostatic recognition processes

    NASA Astrophysics Data System (ADS)

    Getzoff, Elizabeth D.; Roberts, Victoria A.

    The objective is to elucidate the nature of electrostatic forces controlling protein recognition processes by using a tightly coupled computational and interactive computer graphics approach. The TURNIP program was developed to determine the most favorable precollision orientations for two molecules by systematic search of all orientations and evaluation of the resulting electrostatic interactions. TURNIP was applied to the transient interaction between two electron transfer metalloproteins, plastocyanin and cytochrome c. The results suggest that the productive electron-transfer complex involves interaction of the positive region of cytochrome c with the negative patch of plastocyanin, consistent with experimental data. Application of TURNIP to the formation of the stable complex between the HyHEL-5 antibody and its protein antigen lysozyme showed that long-distance electrostatic forces guide lysozyme toward the HyHEL-5 binding site, but do not fine tune its orientation. Determination of docked antigen/antibody complexes requires including steric as well as electrostatic interactions, as was done for the U10 mutant of the anti-phosphorylcholine antibody S107. The graphics program Flex, a convenient desktop workstation program for visualizing molecular dynamics and normal mode motions, was enhanced. Flex now has a user interface and was rewritten to use standard graphics libraries, so as to run on most desktop workstations.

  16. Electrostatic Precipitator (ESP) TRAINING MANUAL

    EPA Science Inventory

    The manual assists engineers in using a computer program, the ESPVI 4.0W, that models all elements of an electrostatic precipitator (ESP). The program is a product of the Electric Power Research Institute and runs in the Windows environment. Once an ESP is accurately modeled, the...

  17. Thermal Characterization of Adhesive

    NASA Technical Reports Server (NTRS)

    Spomer, Ken A.

    1999-01-01

    The current Space Shuttle Reusable Solid Rocket Motor (RSRM) nozzle adhesive bond system is being replaced due to obsolescence. Down-selection and performance testing of the structural adhesives resulted in the selection of two candidate replacement adhesives, Resin Technology Group's Tiga 321 and 3M's EC2615XLW. This paper describes rocket motor testing of these two adhesives. Four forty-pound charge motors were fabricated in configurations that would allow side by side comparison testing of the candidate replacement adhesives and the current RSRM adhesives. The motors provided an environment where the thermal performance of adhesives in flame surface bondlines was compared. Results of the FPC testing show that: 1) The phenolic char depths on radial bond lines is approximately the same and vary depending on the position in the blast tube regardless of which adhesive was used; 2) The adhesive char depth of the candidate replacement adhesives is less than the char depth of the current adhesives; 3) The heat-affected depth of the candidate replacement adhesives is less than the heat-affected depth of the current adhesives; and 4) The ablation rates for both replacement adhesives are slower than that of the current adhesives.

  18. Electrostatic Charging of the Pathfinder Rover

    NASA Technical Reports Server (NTRS)

    Siebert, Mark W.; Kolecki, Joseph C.

    1996-01-01

    The Mars Pathfinder mission will send a lander and a rover to the martian surface. Because of the extremely dry conditions on Mars, electrostatic charging of the rover is expected to occur as it moves about. Charge accumulation may result in high electrical potentials and discharge through the martian atmosphere. Such discharge could interfere with the operation of electrical elements on the rover. A strategy was sought to mitigate this charge accumulation as a precautionary measure. Ground tests were performed to demonstrate charging in laboratory conditions simulating the surface conditions expected at Mars. Tests showed that a rover wheel, driven at typical rover speeds, will accumulate electrical charge and develop significant electrical potentials (average observed, 110 volts). Measurements were made of wheel electrical potential, and wheel capacitance. From these quantities, the amount of absolute charge was estimated. An engineering solution was developed and recommended to mitigate charge accumulation. That solution has been implemented on the actual rover.

  19. Use of Membrane Collectors in Electrostatic Precipitators.

    PubMed

    Bayless, David J; Pasic, Hajrudin; Alam, M Khairul; Shi, Liming; Haynes, Brian; Cochran, Joe; Khan, Wajahat

    2001-10-01

    Membrane collection surfaces, developed and patented by researchers at Ohio University, were used to replace steel plates in a dry electrostatic precipitator (ESP). Such replacement facilitates tension-based rapping, which shears the adhered particle layer from the collector surface more effectively than hammer-based rapping. Tests were performed to measure the collection efficiency of the membranes and to quantify the potential improvements of this novel cleaning technique with respect to re-entrainment. Results indicate that even semiconductor materials (e.g., carbon fibers) collect ash nearly as efficiently as steel plates, potentially indicating that collection surface resistivity is primarily dictated by the accumulated ash layer and not by the underlying plate conductivity. In addition, virtually all sheared particles separated from the collecting membranes fell within the boundary layer of the membrane, indicating extremely low potential for re-entrainment.

  20. Use of membrane collectors in electrostatic precipitators.

    PubMed

    Bayless, D J; Pasic, H; Alam, M K; Shi, L; Haynes, B; Cochran, J; Khan, W

    2001-10-01

    Membrane collection surfaces, developed and patented by researchers at Ohio University, were used to replace steel plates in a dry electrostatic precipitator (ESP). Such replacement facilitates tension-based rapping, which shears the adhered particle layer from the collector surface more effectively than hammer-based rapping. Tests were performed to measure the collection efficiency of the membranes and to quantify the potential improvements of this novel cleaning technique with respect to re-entrainment. Results indicate that even semiconductor materials (e.g., carbon fibers) collect ash nearly as efficiently as steel plates, potentially indicating that collection surface resistivity is primarily dictated by the accumulated ash layer and not by the underlying plate conductivity. In addition, virtually all sheared particles separated from the collecting membranes fell within the boundary layer of the membrane, indicating extremely low potential for re-entrainment.

  1. Geometric and electrostatic modeling using molecular rigidity functions

    DOE PAGES

    Mu, Lin; Xia, Kelin; Wei, Guowei

    2017-03-01

    Geometric and electrostatic modeling is an essential component in computational biophysics and molecular biology. Commonly used geometric representations admit geometric singularities such as cusps, tips and self-intersecting facets that lead to computational instabilities in the molecular modeling. Our present work explores the use of flexibility and rigidity index (FRI), which has a proved superiority in protein B-factor prediction, for biomolecular geometric representation and associated electrostatic analysis. FRI rigidity surfaces are free of geometric singularities. We propose a rigidity based Poisson–Boltzmann equation for biomolecular electrostatic analysis. These approaches to surface and electrostatic modeling are validated by a set of 21 proteins.more » Our results are compared with those of established methods. Finally, being smooth and analytically differentiable, FRI rigidity functions offer excellent curvature analysis, which characterizes concave and convex regions on protein surfaces. Polarized curvatures constructed by using the product of minimum curvature and electrostatic potential is shown to predict potential protein–ligand binding sites.« less

  2. Denture Adhesives

    MedlinePlus

    ... bone and give temporary relief from loosening dentures. Zinc and Potential Risk Zinc is a mineral that is an essential ingredient ... in some dietary supplements. However, an excess of zinc in the body can lead to health problems ...

  3. Irrigant divalent cation concentrations influence bacterial adhesion

    PubMed Central

    Dass, Clarissa L.; Walsh, Mary F.; Seo, Sue; Shiratsuchi, Hiroe; Craig, David H.; Basson, Marc D.

    2009-01-01

    Background Surgical wounds are frequently contaminated by microbes, but rarely become infected if the bacterial burden is low, and irrigation is used to reduce contamination. Wound fluids are low in calcium and high in magnesium. We hypothesized that manipulating irrigant divalent cation concentrations might influence bacterial adhesion. Methods Staphylococcus aureus, E. coli, and Pseudomonas aeruginosa were stained with fluorescent Calcein AM before plating onto fibroblast monolayers, collagen I, or uncoated bacteriologic plastic. After one hour, wells were washed with HEPES-buffered pH-balanced sterile water without or with 5mM CaCl2, 5mM MgCl2 or 1mM EDTA+EGTA, and the remaining adherent bacteria were assayed fluorometrically. Results Supplementing the irrigation with magnesium or chelators increased but calcium-supplemented irrigation reduced bacterial adhesion to collagen or fibroblasts. Non-specific electrostatic bacterial adhesion to uncoated plastic was unaffected by calcium. Conclusion Bacterial adhesion to mammalian cells and matrix proteins is influenced by divalent cations, and pathogenic bacteria may be adapted to adhere under the low calcium high magnesium conditions in wounds. Although these results await confirmation for other bacteria, and in vivo validation and safety-testing, they suggest that supplementing wound irrigation with 5mM CaCl2 may reduce bacterial adhesion and subsequent wound infection. PMID:19577252

  4. The development of aerospace polyimide adhesives

    NASA Technical Reports Server (NTRS)

    St.clair, A. K.; St.clair, T. L.

    1983-01-01

    Few materials are available which can be used as aerospace adhesives at temperatures in the range of 300 C. The Materials Division at NASA-Langley Research Center developed several high temperature polyimide adhesives to fulfill the stringent needs of current aerospace programs. These adhesives are the result of a decade of basic research studies on the structure property relationships of both linear and addition aromatic polyimides. The development of both in house and commercially available polyimides is reviewed with regards to their potential for use as aerospace adhesives.

  5. The development of aerospace polyimide adhesives

    NASA Technical Reports Server (NTRS)

    St. Clair, A. K.; St. Clair, T. L.

    1984-01-01

    Few materials are available which can be used as aerospace adhesives at temperatures in the range of 300 C. The Materials Division at NASA-Langley Research Center developed several high temperature polyimide adhesives to fulfill the stringent needs of current aerospace programs. These adhesives are the result of a decade of basic research studies on the structure property relationships of both linear and addition aromatic polyimides. The development of both in house and commercially available polyimides is reviewed with regards to their potential for use as aerospace adhesives.

  6. Functionally Graded Adhesives for Composite Joints

    NASA Technical Reports Server (NTRS)

    Stapleton, Scott E.; Waas, Anthony M.; Arnold, Steven M.

    2012-01-01

    Adhesives with functionally graded material properties are being considered for use in adhesively bonded joints to reduce the peel stress concentrations located near adherend discontinuities. Several practical concerns impede the actual use of such adhesives. These include increased manufacturing complications, alterations to the grading due to adhesive flow during manufacturing, and whether changing the loading conditions significantly impact the effectiveness of the grading. An analytical study is conducted to address these three concerns. An enhanced joint finite element, which uses an analytical formulation to obtain exact shape functions, is used to model the joint. Furthermore, proof of concept testing is conducted to show the potential advantages of functionally graded adhesives. In this study, grading is achieved by strategically placing glass beads within the adhesive layer at different densities along the joint.

  7. Design considerations in the creation and maintenance of electrostatic cleanliness for solar electrically propelled spacecraft

    NASA Technical Reports Server (NTRS)

    Sellen, J. M., Jr.; Fitzgerald, D. J.

    1975-01-01

    Charge build-up on spacecraft surfaces and resulting zones of electrostatic contamination have been examined for electrically active and electrically passive spacecraft with both conducting and dielectric surface materials, illuminated and nonilluminated surface conditions, and for both inclusion and neglect of free charge effects from photocurrents and ambient space plasma particles. Techniques for measurement and reduction of electrostatic contamination zone extent have been developed for spacecraft with charge release capability. Indicated limitations for contamination cleanup are about 1 volt potential variation from spacecraft to ambient plasma. Bandwidths of electrostatic monitoring and clamping devices extend to several hundred kilohertz for both DC and 'broadband' AC electrostatic cleanliness.

  8. Polyimide adhesives for titanium and composite bonding

    NASA Technical Reports Server (NTRS)

    St. Clair, A. K.; St. Clair, T. L.

    1978-01-01

    Approach results in synthesis of addition polyimide adhesives with exceptional high temperature capabilities that show excellent potential for bonding titanium metal, polyimide/graphite composites, and combinations of these materials. Adhesives compatible with materials used in high performance aircraft and spacecraft structures also prove highly desirable in many other applications involving similar adherents.

  9. Adhesive interactions between vesicles in the strong adhesion limit

    PubMed Central

    Ramachandran, Arun; Anderson, Travers H.; Leal, L. Gary; Israelachvili, Jacob N.

    2010-01-01

    We consider the adhesive interaction energy between a pair of vesicles in the strong adhesion limit, in which bending forces play a negligible role in determining vesicle shape compared to forces due to membrane stretching. Although force-distance or energy distance relationships characterizing adhesive interactions between fluid bilayers are routinely measured using the surface forces apparatus, the atomic force microscope and the biomembrane force probe, the interacting bilayers in these methods are supported on surfaces (e.g. mica sheet) and cannot be deformed. However, it is known that in a suspension, vesicles composed of the same bilayer can deform by stretching or bending, and can also undergo changes in volume. Adhesively interacting vesicles can thus form flat regions in the contact zone, which will result in an enhanced interaction energy as compared to rigid vesicles. The focus of this paper is to examine the magnitude of the interaction energy between adhesively interacting, deformed vesicles relative to free, undeformed vesicles as a function of the intervesicle separation. The modification of the intervesicle interaction energy due to vesicle deformability can be calculated knowing the undeformed radius of the vesicles, R0, the bending modulus kb, the area expansion modulus Ka, and the adhesive minimum WP(0) and separation DP(0) in the energy of interaction between two flat bilayers, which can be obtained from the force-distance measurements made using the above supported-bilayer methods. For vesicles with constant volumes, we show that adhesive potentials between non-deforming bilayers such as ∣WP(0)∣∼5×10−4mJ/m2, which are ordinarily considered weak in colloidal physics literature, can result in significantly deep (>10×) energy minima due to increase in vesicle area and flattening in the contact region. If the osmotic expulsion of water across the vesicles driven by the tense, stretched membrane in the presence of an osmotically active

  10. Understanding Marine Mussel Adhesion

    SciTech Connect

    H. G. Silverman; F. F. Roberto

    2007-12-01

    In addition to identifying the proteins that have a role in underwater adhesion by marine mussels, research efforts have focused on identifying the genes responsible for the adhesive proteins, environmental factors that may influence protein production, and strategies for producing natural adhesives similar to the native mussel adhesive proteins. The production-scale availability of recombinant mussel adhesive proteins will enable researchers to formulate adhesives that are waterimpervious and ecologically safe and can bind materials ranging from glass, plastics, metals, and wood to materials, such as bone or teeth, biological organisms, and other chemicals or molecules. Unfortunately, as of yet scientists have been unable to duplicate the processes that marine mussels use to create adhesive structures. This study provides a background on adhesive proteins identified in the blue mussel, Mytilus edulis, and introduces our research interests and discusses the future for continued research related to mussel adhesion.

  11. Understanding Marine Mussel Adhesion

    PubMed Central

    Roberto, Francisco F.

    2007-01-01

    In addition to identifying the proteins that have a role in underwater adhesion by marine mussels, research efforts have focused on identifying the genes responsible for the adhesive proteins, environmental factors that may influence protein production, and strategies for producing natural adhesives similar to the native mussel adhesive proteins. The production-scale availability of recombinant mussel adhesive proteins will enable researchers to formulate adhesives that are water-impervious and ecologically safe and can bind materials ranging from glass, plastics, metals, and wood to materials, such as bone or teeth, biological organisms, and other chemicals or molecules. Unfortunately, as of yet scientists have been unable to duplicate the processes that marine mussels use to create adhesive structures. This study provides a background on adhesive proteins identified in the blue mussel, Mytilus edulis, and introduces our research interests and discusses the future for continued research related to mussel adhesion. PMID:17990038

  12. Quantitative nanoscale electrostatics of viruses

    NASA Astrophysics Data System (ADS)

    Hernando-Pérez, M.; Cartagena-Rivera, A. X.; Lošdorfer Božič, A.; Carrillo, P. J. P.; San Martín, C.; Mateu, M. G.; Raman, A.; Podgornik, R.; de Pablo, P. J.

    2015-10-01

    Electrostatics is one of the fundamental driving forces of the interaction between biomolecules in solution. In particular, the recognition events between viruses and host cells are dominated by both specific and non-specific interactions and the electric charge of viral particles determines the electrostatic force component of the latter. Here we probe the charge of individual viruses in liquid milieu by measuring the electrostatic force between a viral particle and the Atomic Force Microscope tip. The force spectroscopy data of co-adsorbed φ29 bacteriophage proheads and mature virions, adenovirus and minute virus of mice capsids is utilized for obtaining the corresponding density of charge for each virus. The systematic differences of the density of charge between the viral particles are consistent with the theoretical predictions obtained from X-ray structural data. Our results show that the density of charge is a distinguishing characteristic of each virus, depending crucially on the nature of the viral capsid and the presence/absence of the genetic material.Electrostatics is one of the fundamental driving forces of the interaction between biomolecules in solution. In particular, the recognition events between viruses and host cells are dominated by both specific and non-specific interactions and the electric charge of viral particles determines the electrostatic force component of the latter. Here we probe the charge of individual viruses in liquid milieu by measuring the electrostatic force between a viral particle and the Atomic Force Microscope tip. The force spectroscopy data of co-adsorbed φ29 bacteriophage proheads and mature virions, adenovirus and minute virus of mice capsids is utilized for obtaining the corresponding density of charge for each virus. The systematic differences of the density of charge between the viral particles are consistent with the theoretical predictions obtained from X-ray structural data. Our results show that the density of

  13. Electrostatic Gating of Ultrathin Films

    NASA Astrophysics Data System (ADS)

    Goldman, A. M.

    2014-07-01

    Electrostatic gating of ultrathin films can be used to modify electronic and magnetic properties of materials by effecting controlled alterations of carrier concentration while, in principle, not changing the level of disorder. As such, electrostatic gating can facilitate the development of novel devices and can serve as a means of exploring the fundamental properties of materials in a manner far simpler than is possible with the conventional approach of chemical doping. The entire phase diagram of a compound can be traversed by changing the gate voltage. In this review, we survey results involving conventional field effect devices as well as more recent progress, which has involved structures that rely on electrochemical configurations such as electric double-layer transistors. We emphasize progress involving thin films of oxide materials such as high-temperature superconductors, magnetic oxides, and oxides that undergo metal-insulator transitions.

  14. Closed loop electrostatic levitation system

    NASA Technical Reports Server (NTRS)

    Rhim, W. K.; Saffren, M. M.; Elleman, D. D. (Inventor)

    1985-01-01

    An electrostatic levitation system is described, which can closely control the position of objects of appreciable size. A plurality of electrodes surround the desired position of an electrostatically charged object, the position of the objects is monitored, and the voltages applied to the electrodes are varied to hold the object at a desired position. In one system, the object is suspended above a plate-like electrode which has a concave upper face to urge the object toward the vertical axis of the curved plate. An upper electrode that is also curved can be positioned above the object, to assure curvature of the field at any height above the lower plate. In another system, four spherical electrodes are positioned at the points of a tetrahedron, and the voltages applied to the electrodes are varied in accordance with the object position as detected by two sensors.

  15. Electrostatic interactions in molecular materials

    NASA Astrophysics Data System (ADS)

    Painelli, Anna; Terenziani, Francesca

    2004-03-01

    Non-additive collective behavior appears in molecular materials as a result of intermolecular interactions. We present a model for interacting polar and polarizable molecules that applies to different supramolecular architectures of donor-π-acceptor molecules. We follow a bottom-up modeling strategy: the detailed analysis of spectroscopic data of solvated molecules leads to the definition of a simple two-state model for the molecular units. Classical electrostatic interactions are then introduced to model molecular clusters. The molecular properties are strickingly affected by supramolecular interactions, as demonstrated by spectroscopic studies. Brand new phenomena, like phase transitions and multielectron transfer, with no counterpart at the molecular level are observed as direct consequences of electrostatic intermolecular interactions.

  16. Electrostatic Spraying With Conductive Liquids

    NASA Technical Reports Server (NTRS)

    Kosmo, Joseph J.; Dawn, Frederic S.; Erlandson, Robert E.; Atkins, Loren E.

    1989-01-01

    Thin, uniform polymer coatings applied in water base normally impossible to charge. Electrostatic sprayer modified so applies coatings suspended or dissolved in electrically conductive liquids. Nozzle and gun constructed of nonconductive molded plastic. Liquid passageway made long enough electrical leakage through it low. Coaxial hose for liquid built of polytetrafluoroethylene tube, insulating sleeve, and polyurethane jacket. Sprayer provided with insulated seal at gun-to-hose connection, nonconductive airhose, pressure tank electrically isolated from ground, and special nozzle electrode. Supply of atomizing air reduced so particle momentum controlled by electrostatic field more effectively. Developed to apply water-base polyurethane coating to woven, shaped polyester fabric. Coating provides pressure seal for fabric, which is part of spacesuit. Also useful for applying waterproof, decorative, or protective coatings to fabrics for use on Earth.

  17. Fluorescence Reveals Contamination From Adhesives

    NASA Technical Reports Server (NTRS)

    Nikolia, William

    1992-01-01

    Contamination of nearby surfaces from ingredients in some adhesive materials detected by ultraviolet illumination and observation of resulting fluorescence. Identification of contaminants via telltale fluorescence not new; rather, significance lies in method of implementation and potential extension to wider variety of materials and applications.

  18. Electrostatic generator/motor configurations

    DOEpatents

    Post, Richard F

    2014-02-04

    Electrostatic generators/motors designs are provided that generally may include a first cylindrical stator centered about a longitudinal axis; a second cylindrical stator centered about the axis, a first cylindrical rotor centered about the axis and located between the first cylindrical stator and the second cylindrical stator. The first cylindrical stator, the second cylindrical stator and the first cylindrical rotor may be concentrically aligned. A magnetic field having field lines about parallel with the longitudinal axis is provided.

  19. Defining Protein Electrostatic Recognition Processes

    DTIC Science & Technology

    1992-01-01

    electrostatic Interactions, as we have done for the U10 mutant of the antl- phosphorylcholine antibody S107. We have enhanced the graphics program Fla, a...10486 9393-10486 phosphorylcholine -binding antibody S107, (Chign et al., 1989; Behar et al., 1989). This mutant antibody results from a single-site...mutation of Asp 101 to Ala, over 9 A distant from the antigen binding site, which results in a complete loss of phosphorylcholine binding activity. A

  20. Electrostatic actuators for portable microfluidic systems

    NASA Astrophysics Data System (ADS)

    Tice, Joshua

    minimize actuation potentials while eliminating stiction. Two strategies were developed to overcome challenges with electrode screening in the presence of aqueous fluids. First, instead of using the electrostatic actuators to interact directly with aqueous solutions, the actuators were used to regulate pressurized control lines for pneumatic microvalves. Secondly, by adopting a normally-closed architecture, the actuators were converted into microvalves capable of directly interacting with aqueous solutions. The two strategies are complementary, and together should enable sophisticated microfluidic systems for applications ranging from point-of-care diagnostics to portable chemical detection. To conclude the dissertation, I demonstrate a proof-of-principle microfluidic system that contained sixteen independently-operated electrostatic valves, operated with battery-operated electrical ancillaries in a hand-held format.

  1. Monitoring Mars for Electrostatic Disturbances

    NASA Technical Reports Server (NTRS)

    Compton, D.

    2011-01-01

    The DSN radio telescope DSS-13 was used to monitor Mars for electrostatic discharges from 17 February to 11 April, 2010, and from 19 April to 4 May, 2011, over a total of 72 sessions. Of these sessions, few showed noteworthy results and no outstanding electrostatic disturbances were observed on Mars from analyzing the kurtosis of radio emission from Mars. Electrostatic discharges on mars were originally detected in June of 2006 by Ruf et al. using DSS-13. he kurtosis (normalized fourth moment of the electrical field strength) is sensitive to non-thermal radiation. Two frequencies bands, either 2.4 and 8.4 GHz or 8.4 and 32 GHz were used. The non-thermal radiation spectrum should have peaks at the lowest three modes of the theoretical Schumann Resonances of Mars. The telescope was pointed away from Mars every 5 minutes for 45 seconds to confirm if Mars was indeed the sources of any events. It was shown that by including a down-link signal in one channel and by observing when the kurtosis changed as the telescope was pointed away from the source that the procedure can monitor Mars without the need of extra equipment monitoring a control source.

  2. KSC Electrostatic Discharge (ESD) Issues

    NASA Technical Reports Server (NTRS)

    Buhler, Charles

    2008-01-01

    Discussion of key electrostatic issues that have arisen during the past few years at KSC that the Electrostatics Laboratory has studied. The lab has studied in depth the Space Shuttle's Thermal Control System Blankets, the International Space Station Thermal Blanket, the Pan/Tilt Camera Blankets, the Kapton Purge Barrier Curtain, the Aclar Purge Barrier Curtain, the Thrust Vector Controller Blankets, the Tyvek Reaction Control System covers, the AID-PAK and FLU-9 pyro inflatable devices, the Velostat Solid Rocket Booster mats, and the SCAPE suits. In many cases these materials are insulating meaning that they might be a source of unsafe levels of electrostatic discharge (ESD). For each, the lab provided in-depth testing of each material within its current configuration to ensure that it does not cause an ESD concern that may violate the safety of the astronauts, the workers and equipment for NASA. For example the lab provides unique solutions and testing such as Spark Incendivity Testing that checks whether a material is capable of generating a spark strong enough to ignite a flammable gas. The lab makes recommendations to changes in specifications, procedures, and material if necessary. The lab also consults with a variety of non-safety related ESD issues for the agency.

  3. Test instrumentation evaluates electrostatic hazards in fluid system

    NASA Technical Reports Server (NTRS)

    Collins, L. H.; Henry, R.; Krebs, D.

    1967-01-01

    RJ-1 fuel surface potential is measured with a probe to determine the degree of hazard originating from static electricity buildup in the hydraulic fluid. The probe is mounted in contact with the fluid surface and connected to an electrostatic voltmeter.

  4. Two-dimensional electrostatic lattices for indirect excitons

    NASA Astrophysics Data System (ADS)

    Remeika, M.; Fogler, M. M.; Butov, L. V.; Hanson, M.; Gossard, A. C.

    2012-02-01

    We report on a method for the realization of two-dimensional electrostatic lattices for excitons using patterned interdigitated electrodes. Lattice structure is set by the electrode pattern and depth of the lattice potential is controlled by applied voltages. We demonstrate square, hexagonal, and honeycomb lattices created by this method.

  5. Electrostatic interaction between colloidal particles trapped at an electrolyte interface.

    PubMed

    Majee, Arghya; Bier, Markus; Dietrich, S

    2014-04-28

    The electrostatic interaction between colloidal particles trapped at the interface between two immiscible electrolyte solutions is studied in the limit of small inter-particle distances. Within an appropriate model analytic expressions for the electrostatic potential as well as for the surface and line interaction energies are obtained. They demonstrate that the widely used superposition approximation, which is commonly applied to large distances between the colloidal particles, fails qualitatively at small distances, and is quantitatively unreliable even at large distances. Our results contribute to an improved description of the interaction between colloidal particles trapped at fluid interfaces.

  6. Electrostatic effects in macromolecules: fundamental concepts and practical modeling.

    PubMed

    Warshel, A; Papazyan, A

    1998-04-01

    The past few years have seen an exponential growth in the calculations of electrostatic energies of macromolecules and an increased recognition of the crucial role of electrostatic effects. This review considers the current state of the field. Focus is placed on calculations of pKas, redox potentials and binding energies in macromolecules and clarification of the fact that the value of the dielectric 'constant' of a protein depends on its definition and that small dielectric constants should not be used in describing charge-charge interactions by current continuum models.

  7. Analysis of the effect of LRP-1 silencing on the invasive potential of cancer cells by nanomechanical probing and adhesion force measurements using atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Le Cigne, A.; Chièze, L.; Beaussart, A.; El-Kirat-Chatel, S.; Dufrêne, Y. F.; Dedieu, S.; Schneider, C.; Martiny, L.; Devy, J.; Molinari, M.

    2016-03-01

    Low-density lipoprotein receptor-related protein 1 (LRP-1) can internalize proteases involved in cancer progression and is thus considered a promising therapeutic target. However, it has been demonstrated that LRP-1 is also able to regulate the endocytosis of membrane-anchored proteins. Thus, strategies that target LRP-1 to modulate proteolysis could also affect adhesion and cytoskeleton dynamics. Here, we investigated the effect of LRP-1 silencing on parameters reflecting cancer cells' invasiveness by atomic force microscopy (AFM). The results show that LRP-1 silencing induces changes in the cells' adhesion behavior, particularly the dynamics of cell attachment. Clear alterations in morphology, such as more pronounced stress fibers and increased spreading, leading to increased area and circularity, were also observed. The determination of the cells' mechanical properties by AFM showed that these differences are correlated with an increase in Young's modulus. Moreover, the measurements show an overall decrease in cell motility and modifications of directional persistence. An overall increase in the adhesion force between the LRP-1-silenced cells and a gelatin-coated bead was also observed. Ultimately, our AFM-based force spectroscopy data, recorded using an antibody directed against the β1 integrin subunit, provide evidence that LRP-1 silencing modifies the rupture force distribution. Together, our results show that techniques traditionally used for the investigation of cancer cells can be coupled with AFM to gain access to complementary phenotypic parameters that can help discriminate between specific phenotypes associated with different degrees of invasiveness.Low-density lipoprotein receptor-related protein 1 (LRP-1) can internalize proteases involved in cancer progression and is thus considered a promising therapeutic target. However, it has been demonstrated that LRP-1 is also able to regulate the endocytosis of membrane-anchored proteins. Thus, strategies

  8. A model study of sequential enzyme reactions and electrostatic channeling.

    PubMed

    Eun, Changsun; Kekenes-Huskey, Peter M; Metzger, Vincent T; McCammon, J Andrew

    2014-03-14

    We study models of two sequential enzyme-catalyzed reactions as a basic functional building block for coupled biochemical networks. We investigate the influence of enzyme distributions and long-range molecular interactions on reaction kinetics, which have been exploited in biological systems to maximize metabolic efficiency and signaling effects. Specifically, we examine how the maximal rate of product generation in a series of sequential reactions is dependent on the enzyme distribution and the electrostatic composition of its participant enzymes and substrates. We find that close proximity between enzymes does not guarantee optimal reaction rates, as the benefit of decreasing enzyme separation is countered by the volume excluded by adjacent enzymes. We further quantify the extent to which the electrostatic potential increases the efficiency of transferring substrate between enzymes, which supports the existence of electrostatic channeling in nature. Here, a major finding is that the role of attractive electrostatic interactions in confining intermediate substrates in the vicinity of the enzymes can contribute more to net reactive throughput than the directional properties of the electrostatic fields. These findings shed light on the interplay of long-range interactions and enzyme distributions in coupled enzyme-catalyzed reactions, and their influence on signaling in biological systems.

  9. Spatiotemporal distribution of different extracellular polymeric substances and filamentation mediate Xylella fastidiosa adhesion and biofilm formation

    PubMed Central

    Janissen, Richard; Murillo, Duber M.; Niza, Barbara; Sahoo, Prasana K.; Nobrega, Marcelo M.; Cesar, Carlos L.; Temperini, Marcia L. A.; Carvalho, Hernandes F.; de Souza, Alessandra A.; Cotta, Monica A.

    2015-01-01

    Microorganism pathogenicity strongly relies on the generation of multicellular assemblies, called biofilms. Understanding their organization can unveil vulnerabilities leading to potential treatments; spatially and temporally-resolved comprehensive experimental characterization can provide new details of biofilm formation, and possibly new targets for disease control. Here, biofilm formation of economically important phytopathogen Xylella fastidiosa was analyzed at single-cell resolution using nanometer-resolution spectro-microscopy techniques, addressing the role of different types of extracellular polymeric substances (EPS) at each stage of the entire bacterial life cycle. Single cell adhesion is caused by unspecific electrostatic interactions through proteins at the cell polar region, where EPS accumulation is required for more firmly-attached, irreversibly adhered cells. Subsequently, bacteria form clusters, which are embedded in secreted loosely-bound EPS, and bridged by up to ten-fold elongated cells that form the biofilm framework. During biofilm maturation, soluble EPS forms a filamentous matrix that facilitates cell adhesion and provides mechanical support, while the biofilm keeps anchored by few cells. This floating architecture maximizes nutrient distribution while allowing detachment upon larger shear stresses; it thus complies with biological requirements of the bacteria life cycle. Using new approaches, our findings provide insights regarding different aspects of the adhesion process of X. fastidiosa and biofilm formation. PMID:25891045

  10. Spatiotemporal distribution of different extracellular polymeric substances and filamentation mediate Xylella fastidiosa adhesion and biofilm formation.

    PubMed

    Janissen, Richard; Murillo, Duber M; Niza, Barbara; Sahoo, Prasana K; Nobrega, Marcelo M; Cesar, Carlos L; Temperini, Marcia L A; Carvalho, Hernandes F; de Souza, Alessandra A; Cotta, Monica A

    2015-04-20

    Microorganism pathogenicity strongly relies on the generation of multicellular assemblies, called biofilms. Understanding their organization can unveil vulnerabilities leading to potential treatments; spatially and temporally-resolved comprehensive experimental characterization can provide new details of biofilm formation, and possibly new targets for disease control. Here, biofilm formation of economically important phytopathogen Xylella fastidiosa was analyzed at single-cell resolution using nanometer-resolution spectro-microscopy techniques, addressing the role of different types of extracellular polymeric substances (EPS) at each stage of the entire bacterial life cycle. Single cell adhesion is caused by unspecific electrostatic interactions through proteins at the cell polar region, where EPS accumulation is required for more firmly-attached, irreversibly adhered cells. Subsequently, bacteria form clusters, which are embedded in secreted loosely-bound EPS, and bridged by up to ten-fold elongated cells that form the biofilm framework. During biofilm maturation, soluble EPS forms a filamentous matrix that facilitates cell adhesion and provides mechanical support, while the biofilm keeps anchored by few cells. This floating architecture maximizes nutrient distribution while allowing detachment upon larger shear stresses; it thus complies with biological requirements of the bacteria life cycle. Using new approaches, our findings provide insights regarding different aspects of the adhesion process of X. fastidiosa and biofilm formation.

  11. Electrostatic control of thermoelectricity in molecular junctions.

    PubMed

    Kim, Youngsang; Jeong, Wonho; Kim, Kyeongtae; Lee, Woochul; Reddy, Pramod

    2014-11-01

    Molecular junctions hold significant promise for efficient and high-power-output thermoelectric energy conversion. Recent experiments have probed the thermoelectric properties of molecular junctions. However, electrostatic control of thermoelectric properties via a gate electrode has not been possible due to technical challenges in creating temperature differentials in three-terminal devices. Here, we show that extremely large temperature gradients (exceeding 1 × 10(9) K m(-1)) can be established in nanoscale gaps bridged by molecules, while simultaneously controlling their electronic structure via a gate electrode. Using this platform, we study prototypical Au-biphenyl-4,4'-dithiol-Au and Au-fullerene-Au junctions to demonstrate that the Seebeck coefficient and the electrical conductance of molecular junctions can be simultaneously increased by electrostatic control. Moreover, from our studies of fullerene junctions, we show that thermoelectric properties can be significantly enhanced when the dominant transport orbital is located close to the chemical potential (Fermi level) of the electrodes. These results illustrate the intimate relationship between the thermoelectric properties and charge transmission characteristics of molecular junctions and should enable systematic exploration of the recent computational predictions that promise extremely efficient thermoelectric energy conversion in molecular junctions.

  12. Designing and operating electrostatically driven microengines

    SciTech Connect

    Rodgers, M.S.; Sniegowski, J.J.; Miller, S.L.; LaVigne, G.F.

    1998-02-01

    Microelectromechanical engines that convert the linear outputs from dual orthogonal electrostatic actuators to rotary motion were first developed in 1993. Referred to as microengines, these early devices demonstrated the potential of microelectromechanical technology, but, as expected from any first-of-its-kind device, were not yet optimized. Yield was relatively low, and the 10 micronewtons of force generated by the actuators was not always enough to ensure reliable operation. Since initial development, these engines have undergone a continuous series of significant improvements on three separate fronts: design, fabrication, and electrical activation. Although all three areas will be discussed, emphasis will be on aspects related to mechanical design and generation of the electrical waveforms used to drive these devices. Microtransmissions that dramatically increase torque will also be discussed. Electrostatically driven microengines can be operated at hundreds of thousands of revolutions per minute making large gear reduction ratios feasible; overall ratios of 3,000,000:1 have been successfully demonstrated. Today`s microengines have evolved into high endurance (one test device has seen over 7,000,000,000 revolutions), high yield, robust devices that have become the primary actuation source for MicroElectroMechanical Systems (MEMS) at Sandia National Laboratories.

  13. [Adhesion molecules and diabetes mellitus].

    PubMed

    Urso, C; Hopps, E; Caimi, G

    2010-01-01

    Adhesion molecules play a significant role in leukocyte migration across the endothelium and are also involved in regulating immune system. It is shown that diabetic patients have an increase of soluble adhesion molecules (sICAM-1, sICAM-2, sVCAM-1, sE-selectin, sL-selectin, sP-selectin) considered an integral part of inflammatory state. This inflammation is responsible for the increased cardiovascular risk of these patients. There is a close link between hyperglycemia, oxidative stress, coagulopathy and inflammation and between these factors and the vascular damage. Various studies have showed the potential role of adhesion molecules in the pathogenesis of diabetic vasculopathy. They promote leukocyte recruitment, which is one of the initial steps in the genesis of atherosclerotic plaque. Adhesion molecules are also involved in the pathogenesis of diabetes mellitus type 1; sICAM-1 would have a particular immunomodulatory role in the process of destroying beta-cells and could be used as a subclinical marker of insulitis. Plasma levels of soluble adhesion molecules correlate with hyperglycemia, insulin resistance, dyslipidemia and obesity; they are associated with the development of nephropathy, retinopathy, myocardial infarction, stroke and obliterant peripheral arterial disease in diabetic type 1 and 2. Given the role of these molecules in endothelial dysfunction genesis and tissue damage associated with diabetes, they could constitute a therapeutic target for the prevention of genesis and progression of chronic complications of diabetic disease.

  14. Functionally Graded Adhesives

    DTIC Science & Technology

    2009-11-01

    ASTM 907-05. Standard Terminology of Adhesives. West Conshohocken, PA, May 2005. 4. 3M Scotch-Grip Nitrile High Performance Rubber & Gasket Adhesive...distribution is unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT The goal of this project was to increase rubber to metal adhesion in Army materials using...1 Figure 2. Steel and rubber

  15. PH dependent adhesive peptides

    SciTech Connect

    Tomich, John; Iwamoto, Takeo; Shen, Xinchun; Sun, Xiuzhi Susan

    2010-06-29

    A novel peptide adhesive motif is described that requires no receptor or cross-links to achieve maximal adhesive strength. Several peptides with different degrees of adhesive strength have been designed and synthesized using solid phase chemistries. All peptides contain a common hydrophobic core sequence flanked by positively or negatively charged amino acids sequences.

  16. Thermal Characterization of Epoxy Adhesive by Hotfire Testing

    NASA Technical Reports Server (NTRS)

    Spomer, Ken A.; Haddock, M. Reed; McCool, Alex (Technical Monitor)

    2001-01-01

    This paper describes subscale solid-rocket motor hot-fire testing of epoxy adhesives in flame surface bondlines to evaluate heat-affected depth, char depth and ablation rate. Hot-fire testing is part of an adhesive down-selection program on the Space Shuttle Solid Rocket Motor Nozzle to provide additional confidence in the down-selected adhesives. The current nozzle structural adhesive bond system is being replaced due to obsolescence. Prior to hot-fire testing, adhesives were tested for chemical, physical and mechanical properties, which resulted in the selection of two potential replacement adhesives, Resin Technology Group's TIGA 321 and 3M's EC2615XLW. Hot-fire testing consisted of four forty-pound charge (FPC) motors fabricated in configurations that would allow side-by-side comparison testing of the candidate replacement adhesives with the current RSRM adhesives. Results of the FPC motor testing show that: 1) the phenolic char depths on radial bondlines is approximately the same and vary depending on the position in the blast tube regardless of which adhesive was used, 2) the replacement candidate adhesive char depths are equivalent to the char depths of the current adhesives, 3) the heat-affected depths of the candidate and current adhesives are equivalent, and 4) the ablation rates for both replacement adhesives were equivalent to the current adhesives.

  17. In situ ion gun cleaning of surface adsorbates and its effect on electrostatic forces

    NASA Astrophysics Data System (ADS)

    Schafer, Robert; Xu, Jun; Mohideen, Umar

    2016-01-01

    To obtain precise measurements of the Casimir force, it is crucial to take into account the electrostatic interactions that exist between the two boundaries. Two otherwise grounded conductors will continue to have residual electrostatic effects from patch potentials existing on the surfaces. In this paper, we look at the effect of in situ cleaning of adsorbate patches, and the resultant effect on the net electrostatic potential difference between two surfaces. We find a significant reduction in the residual potential due to in situ Ar+ cleaning for the samples used.

  18. A Nonlinear Elasticity Model of Macromolecular Conformational Change Induced by Electrostatic Forces

    PubMed Central

    Zhou, Y. C.; Holst, Michael; McCammon, J. Andrew

    2008-01-01

    In this paper we propose a nonlinear elasticity model of macromolecular conformational change (deformation) induced by electrostatic forces generated by an implicit solvation model. The Poisson-Boltzmann equation for the electrostatic potential is analyzed in a domain varying with the elastic deformation of molecules, and a new continuous model of the electrostatic forces is developed to ensure solvability of the nonlinear elasticity equations. We derive the estimates of electrostatic forces corresponding to four types of perturbations to an electrostatic potential field, and establish the existance of an equilibrium configuration using a fixed-point argument, under the assumption that the change in the ionic strength and charges due to the additional molecules causing the deformation are sufficiently small. The results are valid for elastic models with arbitrarily complex dielectric interfaces and cavities, and can be generalized to large elastic deformation caused by high ionic strength, large charges, and strong external fields by using continuation methods. PMID:19461946

  19. A Nonlinear Elasticity Model of Macromolecular Conformational Change Induced by Electrostatic Forces.

    PubMed

    Zhou, Y C; Holst, Michael; McCammon, J Andrew

    2008-04-01

    In this paper we propose a nonlinear elasticity model of macromolecular conformational change (deformation) induced by electrostatic forces generated by an implicit solvation model. The Poisson-Boltzmann equation for the electrostatic potential is analyzed in a domain varying with the elastic deformation of molecules, and a new continuous model of the electrostatic forces is developed to ensure solvability of the nonlinear elasticity equations. We derive the estimates of electrostatic forces corresponding to four types of perturbations to an electrostatic potential field, and establish the existance of an equilibrium configuration using a fixed-point argument, under the assumption that the change in the ionic strength and charges due to the additional molecules causing the deformation are sufficiently small. The results are valid for elastic models with arbitrarily complex dielectric interfaces and cavities, and can be generalized to large elastic deformation caused by high ionic strength, large charges, and strong external fields by using continuation methods.

  20. Electrostatic dust transport and Apollo 17 LEAM experiment. [Lunar Ejecta And Meteorite

    NASA Technical Reports Server (NTRS)

    Rhee, J. W.; Berg, O. E.; Wolf, H.

    1977-01-01

    The Lunar Ejecta and Meteorite (LEAM) experiment has been in operation since December 1973 when it was deployed in the Taurus-Littrow region of the moon by the Apollo 17 crew. A specialized analysis based on more than twenty-two lunations of the impact data shows that all of the events recorded by the sensors during the terminator passages are essentially lunar surface microparticles carrying a high electrostatic charge. Charged lunar fines held in place by adhesive forces can be ejected into space if the electrostatic stress exceeds the adhesive strength. A simple laboratory test demonstrated that this soil transport can indeed take place at the lunar terminator and in the vicinity of it.

  1. Mini-review: barnacle adhesives and adhesion.

    PubMed

    Kamino, Kei

    2013-01-01

    Barnacles are intriguing, not only with respect to their importance as fouling organisms, but also in terms of the mechanism of underwater adhesion, which provides a platform for biomimetic and bioinspired research. These aspects have prompted questions regarding how adult barnacles attach to surfaces under water. The multidisciplinary and interdisciplinary nature of the studies makes an overview covering all aspects challenging. This mini-review, therefore, attempts to bring together aspects of the adhesion of adult barnacles by looking at the achievements of research focused on both fouling and adhesion. Biological and biochemical studies, which have been motivated mainly by understanding the nature of the adhesion, indicate that the molecular characteristics of barnacle adhesive are unique. However, it is apparent from recent advances in molecular techniques that much remains undiscovered regarding the complex event of underwater attachment. Barnacles attached to silicone-based elastomeric coatings have been studied widely, particularly with respect to fouling-release technology. The fact that barnacles fail to attach tenaciously to silicone coatings, combined with the fact that the mode of attachment to these substrata is different to that for most other materials, indicates that knowledge about the natural mechanism of barnacle attachment is still incomplete. Further research on barnacles will enable a more comprehensive understanding of both the process of attachment and the adhesives used. Results from such studies will have a strong impact on technology aimed at fouling prevention as well as adhesion science and engineering.

  2. Surface modification with poly(sulfobetaine methacrylate-co-acrylic acid) to reduce fibrinogen adsorption, platelet adhesion, and plasma coagulation.

    PubMed

    Kuo, Wei-Hsuan; Wang, Meng-Jiy; Chien, Hsiu-Wen; Wei, Ta-Chin; Lee, Chiapyng; Tsai, Wei-Bor

    2011-12-12

    Zwitterionic sulfobetaine methacrylate (SBMA) polymers were known to possess excellent antifouling properties due to high hydration capacity and neutral charge surface. In this study, copolymers of SBMA and acrylic acid (AA) with a variety of compositions were synthesized and were immobilized onto polymeric substrates with layer-by-layer polyelectrolyte films via electrostatic interaction. The amounts of platelet adhesion and fibrinogen adsorption were determined to evaluate hemocompatibility of poly(SBMA-co-AA)-modified substrates. Among various deposition conditions by modulating SBMA ratio in the copolymers and pH of the deposition solution, poly(SBMA(56)-co-AA(44)) deposited at pH 3.0 possessed the best hemocompatibility. This work demonstrated that poly(SBMA-co-AA) copolymers adsorbed on polyelectrolyte-base films via electrostatic interaction improve hemocompatibility effectively and are applicable for various substrates including TCPS, PU, and PDMS. Furthermore, poly(SBMA-co-AA)-coated substrate possesses great durability under rigorous conditions. The preliminary hemocompatibility tests regarding platelet adhesion, fibrinogen adsorption, and plasma coagulation suggest the potential of this technique for the application to blood-contacting biomedical devices.

  3. Electrostatic effects in collagen fibrillization

    NASA Astrophysics Data System (ADS)

    Morozova, Svetlana; Muthukumar, Murugappan

    2014-03-01

    Using light scattering and AFM techniques, we have measured the kinetics of fibrillization of collagen (pertinent to the vitreous of human eye) as a function of pH and ionic strength. At higher and lower pH, collagen triple-peptides remain stable in solution without fibrillization. At neutral pH, the fibrillization occurs and its growth kinetics is slowed upon either an increase in ionic strength or a decrease in temperature. We present a model, based on polymer crystallization theory, to describe the observed electrostatic nature of collagen assembly.

  4. Cloning of a balanced translocation breakpoint in the DiGeorge syndrome critical region and isolation of a novel potential adhesion receptor gene in its vicinity.

    PubMed

    Demczuk, S; Aledo, R; Zucman, J; Delattre, O; Desmaze, C; Dauphinot, L; Jalbert, P; Rouleau, G A; Thomas, G; Aurias, A

    1995-04-01

    Deletions of the 22q11.2 have been associated with a wide range of developmental defects (notably DiGeorge syndrome, velocardiofacial syndrome, conotruncal anomaly face syndrome and isolated conotruncal cardiac defects) classified under the acronym CATCH 22. A DiGeorge syndrome patient bearing a balanced translocation whose breakpoint maps within the critical region has been previously described. We report the construction of a cosmid contig spanning the translocation breakpoint and the isolation of a gene mapping 10 kb telomeric to the breakpoint. This gene encodes a novel putative adhesion receptor protein, which could play a role in neural crest cells migration, a process which has been proposed to be altered in DiGeorge syndrome.

  5. Invited Review Article: The electrostatic plasma lens

    SciTech Connect

    Goncharov, Alexey

    2013-02-15

    The fundamental principles, experimental results, and potential applications of the electrostatic plasma lens for focusing and manipulating high-current, energetic, heavy ion beams are reviewed. First described almost 50 years ago, this optical beam device provides space charge neutralization of the ion beam within the lens volume, and thus provides an effective and unique tool for focusing high current beams where a high degree of neutralization is essential to prevent beam blow-up. Short and long lenses have been explored, and a lens in which the magnetic field is provided by rare-earth permanent magnets has been demonstrated. Applications include the use of this kind of optical tool for laboratory ion beam manipulation, high dose ion implantation, heavy ion accelerator injection, in heavy ion fusion, and other high technology.

  6. Multifractality in plasma edge electrostatic turbulence

    NASA Astrophysics Data System (ADS)

    Neto, C. Rodrigues; Guimarães-Filho, Z. O.; Caldas, I. L.; Nascimento, I. C.; Kuznetsov, Yu. K.

    2008-08-01

    Plasma edge turbulence in Tokamak Chauffage Alfvén Brésilien (TCABR) [R. M. O. Galvão et al., Plasma Phys. Contr. Fusion 43, 1181 (2001)] is investigated for multifractal properties of the fluctuating floating electrostatic potential measured by Langmuir probes. The multifractality in this signal is characterized by the full multifractal spectra determined by applying the wavelet transform modulus maxima. In this work, the dependence of the multifractal spectrum with the radial position is presented. The multifractality degree inside the plasma increases with the radial position reaching a maximum near the plasma edge and becoming almost constant in the scrape-off layer. Comparisons between these results with those obtained for random test time series with the same Hurst exponents and data length statistically confirm the reported multifractal behavior. Moreover, the persistence of these signals, characterized by their Hurst exponent, present radial profile similar to the deterministic component estimated from analysis based on dynamical recurrences.

  7. Processes and applications of electrostatic fiber formation

    NASA Astrophysics Data System (ADS)

    Rutledge, Gregory C.

    2008-12-01

    'Electrospinning' is an electrohydrodynamic jetting process that enables the production of continuous fibers, tubes and wires with diameters as small as 10 nm. The process itself is dependent upon electrostatic interactions such as charge-charge repulsion and charge-field interaction. The interplay of charge repulsion, viscoelasticity and surface tension gives rise to interesting electrohydrodynamic phenomena that challenge fundamental understanding as well as practical implementation and quality control in the final fibers. The morphology and diameter of these fibers can be understood and controlled through manipulation of fluid properties and operating parameters. The fibers thus produced are illustrative of nanotechnology in a 1-dimensional form, and have inspired considerable activity in the research community into their potential applications. Proposed uses range from high performance filtration media and membranes, to sensors and actuators, to medical devices and drug delivery vehicles. Two examples, tissue scaffold engineering and superhydrophobicity, are illustrated here.

  8. Nonplanar electrostatic shock waves in dense plasmas

    SciTech Connect

    Masood, W.; Rizvi, H.

    2010-02-15

    Two-dimensional quantum ion acoustic shock waves (QIASWs) are studied in an unmagnetized plasma consisting of electrons and ions. In this regard, a nonplanar quantum Kadomtsev-Petviashvili-Burgers (QKPB) equation is derived using the small amplitude perturbation expansion method. Using the tangent hyperbolic method, an analytical solution of the planar QKPB equation is obtained and subsequently used as the initial profile to numerically solve the nonplanar QKPB equation. It is observed that the increasing number density (and correspondingly the quantum Bohm potential) and kinematic viscosity affect the propagation characteristics of the QIASW. The temporal evolution of the nonplanar QIASW is investigated both in Cartesian and polar planes and the results are discussed from the numerical stand point. The results of the present study may be applicable in the study of propagation of small amplitude localized electrostatic shock structures in dense astrophysical environments.

  9. Probe Measurements of Electrostatic Fluctuations in LDX

    NASA Astrophysics Data System (ADS)

    Ortiz, E. E.; Mauel, M. E.; Garnier, D. T.; Hansen, A. K.; Levitt, B. J.; Kesner, J.; Boxer, A.; Ellsworth, J. L.; Karim, I.; Mahar, S.; Roach, A. H.; Zimmermann, M.

    2004-11-01

    Electrostatic fluctuations play an important role in the equilibrium and stability of a high-beta plasma confined in a dipolar magnetic field. Initial plasma experiments in LDX will use movable edge probes to measure plasma potential, plasma characteristics, and plasma mass flow. Three probe systems have been installed: a triple Langmuir probe (constructed of 1 cm long, 0.5 mm dia. tungsten wire probe tips), an emissive probe (constructed of 0.9 cm long, 1 mm dia. thoriated tungsten wire), and a Mach probe (constructed with two 0.7 cm long, 1.5 mm dia. tungsten wires). Each probe is mounted on an adjustable feed-through capable of scanning parameters along a 40 cm cord at the plasma edge. Initial measurements and interpretations from first plasma experiments will be presented.

  10. Electrostatic attraction between overall neutral surfaces.

    PubMed

    Adar, Ram M; Andelman, David; Diamant, Haim

    2016-08-01

    Two overall neutral surfaces with positively and negatively charged domains ("patches") have been shown in recent experiments to exhibit long-range attraction when immersed in an ionic solution. Motivated by the experiments, we calculate analytically the osmotic pressure between such surfaces within the Poisson-Boltzmann framework, using a variational principle for the surface-averaged free energy. The electrostatic potential, calculated beyond the linear Debye-Hückel theory, yields an overall attraction at large intersurface separations, over a wide range of the system's controlled length scales. In particular, the attraction is stronger and occurs at smaller separations for surface patches of larger size and charge density. In this large patch limit, we find that the attraction-repulsion crossover separation is inversely proportional to the square of the patch-charge density and to the Debye screening length.

  11. Quantitative Membrane Electrostatics with the Atomic Force Microscope

    PubMed Central

    Yang, Yi; Mayer, Kathryn M.; Hafner, Jason H.

    2007-01-01

    The atomic force microscope (AFM) is sensitive to electric double layer interactions in electrolyte solutions, but provides only a qualitative view of interfacial electrostatics. We have fully characterized silicon nitride probe tips and other experimental parameters to allow a quantitative electrostatic analysis by AFM, and we have tested the validity of a simple analytical force expression through numerical simulations. As a test sample, we have measured the effective surface charge density of supported zwitterionic dioleoylphosphatidylcholine membranes with a variable fraction of anionic dioleoylphosphatidylserine. The resulting surface charge density and surface potential values are in quantitative agreement with those predicted by the Gouy-Chapman-Stern model of membrane charge regulation, but only when the numerical analysis is employed. In addition, we demonstrate that the AFM can detect double layer forces at a separation of several screening lengths, and that the probe only perturbs the membrane surface potential by <2%. Finally, we demonstrate 50-nm resolution electrostatic mapping on heterogeneous model membranes with the AFM. This novel combination of capabilities demonstrates that the AFM is a unique and powerful probe of membrane electrostatics. PMID:17158563

  12. Discriminatory bio-adhesion over nano-patterned polymer brushes

    NASA Astrophysics Data System (ADS)

    Gon, Saugata

    1000/mum 2) was required for fibrinogen adsorption while a greater density comprised the adhesion threshold for albumin. Surface compositions between these two thresholds discriminated binding of the two proteins. The binding behavior of the two proteins from a mixture was well anticipated by the single- protein binding behaviors of the individual proteins. The mechanism for protein capture was shown to be multivalent: protein adhesion always occurred for averages spacings of the adhesive patches smaller than the dimensions of the protein of interest. For some backfill brush architectures, the spacing between the patches at the threshold for protein capture clearly corresponded to the major dimension of the target protein. For more dense PEG brush backfills however, larger adhesion thresholds were observed, corresponding to greater numbers of patches involved with the adhesion of each protein molecule. . The thesis demonstrates the tuning of the position of the adhesion thresholds, using fibrinogen as a model protein, using variations in brush properties and ionic strength. The directions of the trends indicate that the brushes do indeed exert steric repulsions toward the proteins while the attractions are electrostatic in nature. The surfaces also demonstrated sharp adhesion thresholds for S. Aureus bacteria, at smaller concentrations of adhesive surfaces elements than those needed for the protein capture. The results suggest that bacteria may be captured while proteins are rejected from these surfaces, and there may be potential to discriminate different bacterial types. Such discrimination from protein-containing bacterial suspensions was investigated briefly in this thesis using S. Aureus and fibrinogen as a model mixture. However, due to binding of fibrinogen to the bacterial surface, the separation did not succeed. It is still expected, however, that these surfaces could be used to selectively capture bacteria in the presence of non-interacting proteins. The

  13. Critical length scale controls adhesive wear mechanisms

    PubMed Central

    Aghababaei, Ramin; Warner, Derek H.; Molinari, Jean-Francois

    2016-01-01

    The adhesive wear process remains one of the least understood areas of mechanics. While it has long been established that adhesive wear is a direct result of contacting surface asperities, an agreed upon understanding of how contacting asperities lead to wear debris particle has remained elusive. This has restricted adhesive wear prediction to empirical models with limited transferability. Here we show that discrepant observations and predictions of two distinct adhesive wear mechanisms can be reconciled into a unified framework. Using atomistic simulations with model interatomic potentials, we reveal a transition in the asperity wear mechanism when contact junctions fall below a critical length scale. A simple analytic model is formulated to predict the transition in both the simulation results and experiments. This new understanding may help expand use of computer modelling to explore adhesive wear processes and to advance physics-based wear laws without empirical coefficients. PMID:27264270

  14. Electrostatic properties of graphitic nanostructures

    NASA Astrophysics Data System (ADS)

    Erbahar, Dogan

    2014-03-01

    Carbon nanostructures are considered to be one of the most important candidates of circuit elements for future nanoelectronics. However, being one of the main issues of conventional circuitry used today, charge accumulation on circuit elements can also be expected to have important effects on the performance of the nanoscale devices. In this work we investigated charge accumulation on various graphitic systems by simulated charge doping. We report ab initio density functional theory (DFT) calculations of electrostatically charged multilayered carbon nano structures. We investigate the effect of total and background charge on charge distribution profiles on the systems under consideration varying from multilayered graphene to multiwalled carbon nanotubes. We show that the charge distribution profile on the inner layers are mainly induced from the background charge which is imposed by the code on periodic systems. Our population anaylsis indicates that the outermost two layers effectively shields the inner layers electrostatically. Illuminating the typical skin depth of those systems our results could give important insights for designing the nanocircuit elements.

  15. Electrostatic Tuning of Cellular Excitability

    PubMed Central

    Börjesson, Sara I.; Parkkari, Teija; Hammarström, Sven; Elinder, Fredrik

    2010-01-01

    Abstract Voltage-gated ion channels regulate the electric activity of excitable tissues, such as the heart and brain. Therefore, treatment for conditions of disturbed excitability is often based on drugs that target ion channels. In this study of a voltage-gated K channel, we propose what we believe to be a novel pharmacological mechanism for how to regulate channel activity. Charged lipophilic substances can tune channel opening, and consequently excitability, by an electrostatic interaction with the channel's voltage sensors. The direction of the effect depends on the charge of the substance. This was shown by three compounds sharing an arachidonyl backbone but bearing different charge: arachidonic acid, methyl arachidonate, and arachidonyl amine. Computer simulations of membrane excitability showed that small changes in the voltage dependence of Na and K channels have prominent impact on excitability and the tendency for repetitive firing. For instance, a shift in the voltage dependence of a K channel with −5 or +5 mV corresponds to a threefold increase or decrease in K channel density, respectively. We suggest that electrostatic tuning of ion channel activity constitutes a novel and powerful pharmacological approach with which to affect cellular excitability. PMID:20141752

  16. Breakdown mechanisms in electrostatic deflector

    NASA Astrophysics Data System (ADS)

    Re, M.; Cuttone, G.; Zappalà, E.; Passarello, S.

    2001-12-01

    The Electrostatic Beam Deflectors for the K800 Superconducting Cyclotron are the most critical elements of the beam extraction system. It has been carried out an accurate investigation from the microscopic point of view, leading to a better comprehension of the complex phenomena taking part in the breakdown process. The environmental conditions are high electric field (up to 130 kV/cm), high magnetic field (up to 5 T) in addition with high energy (70 MeV/u) and high power ion beam. It has been found that all the materials constituent the electrostatic deflector, and not only the electrodes, give an important contribute to the mechanism of breakdown that occurs in two main ways: insulator metalization and enhanced electrodes electron emission. These two effects are involved in a positive feedback process which amplifies the effects leading to a fast breakdown. These phenomena are here shown and some possible solutions are at the moment under test using several bulk (Mo, Ti, Cu) and coating materials (TiN, Diamond Like Carbon).

  17. Electrostatic charging of lunar dust

    SciTech Connect

    Walch, Bob; Horanyi, Mihaly; Robertson, Scott

    1998-10-21

    Transient dust clouds suspended above the lunar surface were indicated by the horizon glow observed by the Surveyor spacecrafts and the Lunar Ejecta and Meteorite Experiment (Apollo 17), for example. The theoretical models cannot fully explain these observations, but they all suggest that electrostatic charging of the lunar surface due to exposure to the solar wind plasma and UV radiation could result in levitation, transport and ejection of small grains. We report on our experimental studies of the electrostatic charging properties of an Apollo-17 soil sample and two lunar simulants MLS-1 and JSC-1. We have measured their charge after exposing individual grains to a beam of fast electrons with energies in the range of 20{<=}E{<=}90 eV. Our measurements indicate that the secondary electron emission yield of the Apollo-17 sample is intermediate between MLS-1 and JSC-1, closer to that of MLS-1. We will also discuss our plans to develop a laboratory lunar surface model, where time dependent illumination and plasma bombardment will closely emulate the conditions on the surface of the Moon.

  18. Microencapsulation and Electrostatic Processing Device

    NASA Technical Reports Server (NTRS)

    Morrison, Dennis R. (Inventor); Mosier, Benjamin (Inventor); Cassanto, John M. (Inventor)

    2001-01-01

    A microencapsulation and electrostatic processing (MEP) device is provided for forming microcapsules. In one embodiment, the device comprises a chamber having a filter which separates a first region in the chamber from a second region in the chamber. An aqueous solution is introduced into the first region through an inlet port, and a hydrocarbon/ polymer solution is introduced into the second region through another inlet port. The filter acts to stabilize the interface and suppress mixing between the two immiscible solutions as they are being introduced into their respective regions. After the solutions have been introduced and have become quiescent, the interface is gently separated from the filter. At this point, spontaneous formation of microcapsules at the interface may begin to occur, or some fluid motion may be provided to induce microcapsule formation. In any case, the fluid shear force at the interface is limited to less than 100 dynes/sq cm. This low-shear approach to microcapsule formation yields microcapsules with good sphericity and desirable size distribution. The MEP device is also capable of downstream processing of microcapsules, including rinsing, re-suspension in tertiary fluids, electrostatic deposition of ancillary coatings, and free-fluid electrophoretic separation of charged microcapsules.

  19. Electrostatic properties of aqueous interfaces probed by small solutes

    NASA Astrophysics Data System (ADS)

    Pohorille, Andrew; Wilson, Michael A.; Schweighofer, Karl

    1999-11-01

    The excess chemical potentials of methane and its four fluorinated derivatives across the water-hexane, water-octanol, water-glycerol 1-monooleate and water-1-palmitoyl 2-oleoyl sn-glycero 3-phosphatidylcholine (POPC) interfaces are calculated using the particle insertion method. In all cases, the polar species exhibit interfacial minima indicating that these molecules tend to accumulate in the interfacial region, while the non-polar molecules exhibit no such minimum. The excess chemical potentials are further partitioned into electrostatic and non-electrostatic terms. For polar molecules, the electrostatic term changes nearly linearly over the distance of approximately 10 Å in the interfacial region and appears to depend only weakly on the nature of the interface. Solute molecules are not oriented isotropically at the interface, but tend to align themselves with the excess electric field created by the anisotropic interfacial environment. Using dipoles in a cavity as models, it is further shown that, in the water-POPC system, the electrostatic term changes with the size of the dipole according to the predictions of linear response theory. This approximation does not work as well for the other interfacial systems investigated. This may be an artifact due to the neglect of long-range effects in those simulations. The non-electrostatic term, dominated by the reversible work of cavity formation, shows interfacially induced structure. In particular, it is responsible for a maximum of the excess chemical potential on the dense, water side of the water-POPC interface. The results of this study provide guidance to developing simple but accurate implicit models of interfacial systems.

  20. Strong, reversible underwater adhesion via gecko-inspired hydrophobic fibers.

    PubMed

    Soltannia, Babak; Sameoto, Dan

    2014-12-24

    Strong, reversible underwater adhesion using gecko-inspired surfaces is achievable through the use of a hydrophobic structural material and does not require surface modification or suction cup effects for this adhesion to be effective. Increased surface energy can aid in dry adhesion in an air environment but strongly degrades wet adhesion via reduction of interfacial energy underwater. A direct comparison of structurally identical but chemically different mushroom shaped fibers shows that strong, reversible adhesion, even in a fully wetted, stable state, is feasible underwater if the structural material of the fibers is hydrophobic and the mating surface is not strongly hydrophilic. The exact adhesion strength will be a function of the underwater interfacial energy between surfaces and the specific failure modes of individual fibers. This underwater adhesion has been calculated to be potentially greater than the dry adhesion for specific combinations of hydrophobic surfaces.

  1. Electrostatic atomization: Effect of electrode materials on electrostatic atomizer performance

    NASA Astrophysics Data System (ADS)

    Sankaran, Abhilash; Staszel, Christopher; Kashir, Babak; Perri, Anthony; Mashayek, Farzad; Yarin, Alexander

    2016-11-01

    Electrostatic atomization was studied experimentally with a pointed electrode in a converging nozzle. Experiments were carried out on poorly conductive canola oil where it was observed that electrode material may affect charge transfer. This points at the possible faradaic reactions that can occur at the surfaces of the electrodes. The supply voltage is applied to the sharp electrode and the grounded nozzle body constitutes the counter-electrode. The charge transfer is controlled by the electrochemical reactions on both the electrodes. The electrical performance study of the atomizer issuing a charged oil jet was conducted using three different nozzle body materials - brass, copper and stainless steel. Also, two sharp electrode materials - brass and stainless steel - were tested. The experimental results revealed that both the nozzle body material, as well as the sharp electrode material affected the spray and leak currents. Moreover, the effect of the sharp electrode material is quite significant. This research is supported by NSF Grant 1505276.

  2. The direct approach to gravitation and electrostatics method for periodic systems.

    PubMed

    Losilla, S A; Sundholm, D; Jusélius, J

    2010-01-14

    The direct approach to gravitation and electrostatics (DAGE) algorithm is an accurate, efficient, and flexible method for calculating electrostatic potentials. In this paper, we show that the algorithm can be easily extended to consider systems with many different kinds of periodicities, such as crystal lattices, surfaces, or wires. The accuracy and performance are nearly the same for periodic and aperiodic systems. The electrostatic potential for semiperiodic systems, namely defects in crystal lattices, can be obtained by combining periodic and aperiodic calculations. The method has been applied to an ionic model system mimicking NaCl, and to a corresponding covalent model system.

  3. The calculation of electrostatic interactions and their role in determining the energies and geometries of explosive molecular crystals

    SciTech Connect

    Ritchie, J.P.; Kober, E.M.; Copenhaver, A.S.

    1993-01-01

    Three different procedures were used to calculate electrostatic interactions in explosive molecular crystals. The use of Potential Derived Charges (PDC's) and atom-centered multipole expansions (ACME's) provides reasonable fits of the molecular electrostatic potential. The ability of these approaches to reproduce observed crystal structures was also evaluated.

  4. A small-gap electrostatic micro-actuator for large deflections

    PubMed Central

    Conrad, Holger; Schenk, Harald; Kaiser, Bert; Langa, Sergiu; Gaudet, Matthieu; Schimmanz, Klaus; Stolz, Michael; Lenz, Miriam

    2015-01-01

    Common quasi-static electrostatic micro actuators have significant limitations in deflection due to electrode separation and unstable drive regions. State-of-the-art electrostatic actuators achieve maximum deflections of approximately one third of the electrode separation. Large electrode separation and high driving voltages are normally required to achieve large actuator movements. Here we report on an electrostatic actuator class, fabricated in a CMOS-compatible process, which allows high deflections with small electrode separation. The concept presented makes the huge electrostatic forces within nanometre small electrode separation accessible for large deflections. Electrostatic actuations that are larger than the electrode separation were measured. An analytical theory is compared with measurement and simulation results and enables closer understanding of these actuators. The scaling behaviour discussed indicates significant future improvement on actuator deflection. The presented driving concept enables the investigation and development of novel micro systems with a high potential for improved device and system performance. PMID:26655557

  5. A small-gap electrostatic micro-actuator for large deflections.

    PubMed

    Conrad, Holger; Schenk, Harald; Kaiser, Bert; Langa, Sergiu; Gaudet, Matthieu; Schimmanz, Klaus; Stolz, Michael; Lenz, Miriam

    2015-12-11

    Common quasi-static electrostatic micro actuators have significant limitations in deflection due to electrode separation and unstable drive regions. State-of-the-art electrostatic actuators achieve maximum deflections of approximately one third of the electrode separation. Large electrode separation and high driving voltages are normally required to achieve large actuator movements. Here we report on an electrostatic actuator class, fabricated in a CMOS-compatible process, which allows high deflections with small electrode separation. The concept presented makes the huge electrostatic forces within nanometre small electrode separation accessible for large deflections. Electrostatic actuations that are larger than the electrode separation were measured. An analytical theory is compared with measurement and simulation results and enables closer understanding of these actuators. The scaling behaviour discussed indicates significant future improvement on actuator deflection. The presented driving concept enables the investigation and development of novel micro systems with a high potential for improved device and system performance.

  6. Sticky Matrix: Adhesion Mechanism of the Staphylococcal Polysaccharide Intercellular Adhesin.

    PubMed

    Formosa-Dague, Cécile; Feuillie, Cécile; Beaussart, Audrey; Derclaye, Sylvie; Kucharíková, Soňa; Lasa, Iñigo; Van Dijck, Patrick; Dufrêne, Yves F

    2016-03-22

    The development of bacterial biofilms on surfaces leads to hospital-acquired infections that are difficult to fight. In Staphylococci, the cationic polysaccharide intercellular adhesin (PIA) forms an extracellular matrix that connects the cells together during biofilm formation, but the molecular forces involved are unknown. Here, we use advanced force nanoscopy techniques to unravel the mechanism of PIA-mediated adhesion in a clinically relevant methicillin-resistant Staphylococcus aureus (MRSA) strain. Nanoscale multiparametric imaging of the structure, adhesion, and elasticity of bacteria expressing PIA shows that the cells are surrounded by a soft and adhesive matrix of extracellular polymers. Cell surface softness and adhesion are dramatically reduced in mutant cells deficient for the synthesis of PIA or under unfavorable growth conditions. Single-cell force spectroscopy demonstrates that PIA promotes cell-cell adhesion via the multivalent electrostatic interaction with polyanionic teichoic acids on the S. aureus cell surface. This binding mechanism rationalizes, at the nanoscale, the well-known ability of PIA to strengthen intercellular adhesion in staphylococcal biofilms. Force nanoscopy offers promising prospects for understanding the fundamental forces in antibiotic-resistant biofilms and for designing anti-adhesion compounds targeting matrix polymers.

  7. New Blocking Antibodies Impede Adhesion, Migration and Survival of Ovarian Cancer Cells, Highlighting MFGE8 as a Potential Therapeutic Target of Human Ovarian Carcinoma

    PubMed Central

    Tibaldi, Lorenzo; Notebaert, Sofie; Dewulf, Melissa; Ngo, Thu Hoa; Zuany-Amorim, Claudia; Amzallag, Nathalie; Bernard-Pierrot, Isabelle; Sastre-Garau, Xavier; Théry, Clotilde

    2013-01-01

    Milk Fat Globule – EGF – factor VIII (MFGE8), also called lactadherin, is a secreted protein, which binds extracellularly to phosphatidylserine and to αvβ3 and αvβ5 integrins. On human and mouse cells expressing these integrins, such as endothelial cells, phagocytes and some tumors, MFGE8/lactadherin has been shown to promote survival, epithelial to mesenchymal transition and phagocytosis. A protumoral function of MFGE8 has consequently been documented for a few types of human cancers, including melanoma, a subtype of breast cancers, and bladder carcinoma. Inhibiting the functions of MFGE8 could thus represent a new type of therapy for human cancers. Here, we show by immunohistochemistry on a collection of human ovarian cancers that MFGE8 is overexpressed in 45% of these tumors, and we confirm that it is specifically overexpressed in the triple-negative subtype of human breast cancers. We have established new in vitro assays to measure the effect of MFGE8 on survival, adhesion and migration of human ovarian and triple-negative breast cancer cell lines. Using these assays, we could identify new MFGE8-specific monoclonal antibodies, which efficiently blocked these three tumor-promoting effects of MFGE8. Our results suggest future use of MFGE8-blocking antibodies as new anti-cancer therapeutics in subgroups of ovarian carcinoma, and triple-negative breast carcinoma patients. PMID:23977342

  8. A Triboelectric Sensor Array for Electrostatic Studies on the Lunar Surface

    NASA Technical Reports Server (NTRS)

    Johansen, Michael R.; Mackey, Paul J.; Calle, C. I.

    2015-01-01

    The moons electrostatic environment requires careful consideration in the development of future lunar landers. Electrostatically charged dust was well documented during the Apollo missions to cause thermal control, mechanical, and visibility issues. The fine dust particles that make up the surface are electrostatically charged as a result of numerous charging mechanisms. The relatively dry conditions on the moon creates a prime tribocharging environment during surface operations. The photoelectric effect is dominant for lunar day static charging, while plasma electrons are the main contributor for lunar night electrostatic effects. Electrostatic charging is also dependent on solar intensity, Earth-moon relative positions, and cosmic ray flux. This leads to a very complex and dynamic electrostatic environment that must be studied for the success of long term lunar missions.In order to better understand the electrostatic environment of planetary bodies, Kennedy Space Center, in previous collaboration with the Jet Propulsion Laboratory, has developed an electrostatic sensor suite. One of the instruments included in this package is the triboelectric sensor array. It is comprised of strategically selected materials that span the triboelectric series and that also have previous spaceflight history. In this presentation, we discuss detailed testing with the triboelectric sensor array performed at Kennedy Space Center. We will discuss potential benefits and use cases of this low mass, low cost sensor package, both for science and for mission success.

  9. Modeling of a high force density fishbone shaped electrostatic comb drive microactuator.

    PubMed

    Megat Hasnan, Megat Muhammad Ikhsan; Mohd Sabri, Mohd Faizul; Mohd Said, Suhana; Nik Ghazali, Nik Nazri

    2014-01-01

    This paper presents the design and evaluation of a high force density fishbone shaped electrostatic comb drive actuator. This comb drive actuator has a branched structure similar to a fishbone, which is intended to increase the capacitance of the electrodes and hence increase the electrostatic actuation force. Two-dimensional finite element analysis was used to simulate the motion of the fishbone shaped electrostatic comb drive actuator and compared against the performance of a straight sided electrostatic comb drive actuator. Performances of both designs are evaluated by comparison of displacement and electrostatic force. For both cases, the active area and the minimum gap distance between the two electrodes were constant. An active area of 800 × 300 μm, which contained 16 fingers of fishbone shaped actuators and 40 fingers of straight sided actuators, respectively, was used. Through simulation, improvement of drive force of the fishbone shaped electrostatic comb driver is approximately 485% higher than conventional electrostatic comb driver. These results indicate that the fishbone actuator design provides good potential for applications as high force density electrostatic microactuator in MEMS systems.

  10. Desmosomal adhesion in vivo.

    PubMed

    Berika, Mohamed; Garrod, David

    2014-02-01

    Desmosomes are intercellular junctions that provide strong adhesion or hyper-adhesion in tissues. Here, we discuss the molecular and structural basis of this with particular reference to the desmosomal cadherins (DCs), their isoforms and evolution. We also assess the role of DCs as regulators of epithelial differentiation. New data on the role of desmosomes in development and human disease, especially wound healing and pemphigus, are briefly discussed, and the importance of regulation of the adhesiveness of desmosomes in tissue dynamics is considered.

  11. Electrostatic analysis of nanoelectromechanical systems

    NASA Astrophysics Data System (ADS)

    Xu, Yang

    We present a multiscale method, seamlessly combining semiclassical, effective-mass Schrodinger (EMS), and tight-binding (TB) theories proposed for electrostatic analysis of silicon nanoelectromechanical systems (NEMS). By using appropriate criteria, we identify the physical models that are accurate in each local region. If the local physical model is semiclassical, the charge density is directly computed by the semiclassical theory. If the local physical model is quantum-mechanical (EMS or TB model), the charge density is calculated by using the theory of local density of states (LDOS). The LDOS is efficiently calculated from Green's function by using Haydock's recursion method where the Green's function is expressed as a continued fraction based on the local Hamiltonian. Once the charge density is determined, a Poisson equation is solved self-consistently to determine the electronic properties. The accuracy and efficiency of the multiscale method are demonstrated by considering several NEMS examples. The multiscale method can be used to compute the effect of surface and interior defects such as vacancies and broken bonds on the performance of microelectromechanical systems (MEMS). By combining multiscale electrostatic analysis with mechanical analysis, we compute the capacitance-voltage and pull-in/pull-out voltages of MEMS switches in the presence of defects in the dielectric oxide layer. Our results indicate that both surface and interior defects can change the pull-in/pull-out voltages significantly. These voltage offsets can lead to an eventual failure of the MEMS switches. The self-consistent TB method is used to investigate carbon nanotube (CNT)-based sensors. We compute the screening effects of semiconducting and metallic single-wall carbon nanotubes (SWNTs) when water molecules and various ions pass through the nanotubes. The trajectories of ions and water molecules are obtained from molecular dynamics (MD) simulations. It is shown that metallic SWNTs have

  12. Portable liquid collection electrostatic precipitator

    DOEpatents

    Carlson, Duane C.; DeGange, John J.; Halverson, Justin E.

    2005-10-18

    A portable liquid collection electrostatic collection precipitator for analyzing air is provided which is a relatively small, self-contained device. The device has a tubular collection electrode, a reservoir for a liquid, and a pump. The pump pumps the liquid into the collection electrode such that the liquid flows down the exterior of the collection electrode and is recirculated to the reservoir. An air intake is provided such that air to be analyzed flows through an ionization section to ionize analytes in the air, and then flows near the collection electrode where ionized analytes are collected. A portable power source is connected to the air intake and the collection electrode. Ionizable constituents in the air are ionized, attracted to the collection electrode, and precipitated in the liquid. The precipitator may also have an analyzer for the liquid and may have a transceiver allowing remote operation and data collection.

  13. Microencapsulation and Electrostatic Processing Method

    NASA Technical Reports Server (NTRS)

    Morrison, Dennis R. (Inventor); Mosier, Benjamin (Inventor)

    2000-01-01

    Methods are provided for forming spherical multilamellar microcapsules having alternating hydrophilic and hydrophobic liquid layers, surrounded by flexible, semi-permeable hydrophobic or hydrophilic outer membranes which can be tailored specifically to control the diffusion rate. The methods of the invention rely on low shear mixing and liquid-liquid diffusion process and are particularly well suited for forming microcapsules containing both hydrophilic and hydrophobic drugs. These methods can be carried out in the absence of gravity and do not rely on density-driven phase separation, mechanical mixing or solvent evaporation phases. The methods include the process of forming, washing and filtering microcapsules. In addition, the methods contemplate coating microcapsules with ancillary coatings using an electrostatic field and free fluid electrophoresis of the microcapsules. The microcapsules produced by such methods are particularly useful in the delivery of pharmaceutical compositions.

  14. Large Aperture Electrostatic Dust Detector

    SciTech Connect

    C.H. Skinner, R. Hensley, and A.L Roquemore

    2007-10-09

    Diagnosis and management of dust inventories generated in next-step magnetic fusion devices is necessary for their safe operation. A novel electrostatic dust detector, based on a fine grid of interlocking circuit traces biased to 30 or 50 ν has been developed for the detection of dust particles on remote surfaces in air and vacuum environments. Impinging dust particles create a temporary short circuit and the resulting current pulse is recorded by counting electronics. Up to 90% of the particles are ejected from the grid or vaporized suggesting the device may be useful for controlling dust inventories. We report measurements of the sensitivity of a large area (5x5 cm) detector to microgram quantities of dust particles and review its applications to contemporary tokamaks and ITER.

  15. Reversible Thermoset Adhesives

    NASA Technical Reports Server (NTRS)

    Mac Murray, Benjamin C. (Inventor); Tong, Tat H. (Inventor); Hreha, Richard D. (Inventor)

    2016-01-01

    Embodiments of a reversible thermoset adhesive formed by incorporating thermally-reversible cross-linking units and a method for making the reversible thermoset adhesive are provided. One approach to formulating reversible thermoset adhesives includes incorporating dienes, such as furans, and dienophiles, such as maleimides, into a polymer network as reversible covalent cross-links using Diels Alder cross-link formation between the diene and dienophile. The chemical components may be selected based on their compatibility with adhesive chemistry as well as their ability to undergo controlled, reversible cross-linking chemistry.

  16. Adhesion at metal interfaces

    NASA Technical Reports Server (NTRS)

    Banerjea, Amitava; Ferrante, John; Smith, John R.

    1991-01-01

    A basic adhesion process is defined, the theory of the properties influencing metallic adhesion is outlined, and theoretical approaches to the interface problem are presented, with emphasis on first-principle calculations as well as jellium-model calculations. The computation of the energies of adhesion as a function of the interfacial separation is performed; fully three-dimensional calculations are presented, and universality in the shapes of the binding energy curves is considered. An embedded-atom method and equivalent-crystal theory are covered in the framework of issues involved in practical adhesion.

  17. Adhesives, silver amalgam.

    PubMed

    1995-09-01

    The most recent advancement in silver amalgam is use of resin formulations to bond metal to tooth both chemically &/or physically, Since, historically, amalgam has been used successfully without adhesion to tooth, obvious clinical question is: Why is bonding now desirable? Two major clinical reasons to bond are: (1) Adhesive can increase fracture resistance of amalgam restored teeth & decrease cusp fractures; & (2) Seal provided by adhesive can greatly decrease, & often eliminate post-operative sensitivity. Following report summarizes CRA laboratory study of shear bond strength & sealing capability of 23 commercial adhesives used to bond 2 types of silver amalgam to tooth structure.

  18. Review on the modeling of electrostatic MEMS.

    PubMed

    Chuang, Wan-Chun; Lee, Hsin-Li; Chang, Pei-Zen; Hu, Yuh-Chung

    2010-01-01

    Electrostatic-driven microelectromechanical systems devices, in most cases, consist of couplings of such energy domains as electromechanics, optical electricity, thermoelectricity, and electromagnetism. Their nonlinear working state makes their analysis complex and complicated. This article introduces the physical model of pull-in voltage, dynamic characteristic analysis, air damping effect, reliability, numerical modeling method, and application of electrostatic-driven MEMS devices.

  19. Electrostatics experiments with sharp metal points

    NASA Astrophysics Data System (ADS)

    Ivanov, Dragia; Nikolov, Stefan

    2016-11-01

    In this paper we examine the phenomena that arise around an electrically charged sharp metal spike and present numerous experiments that can be used in the teaching of electrostatics. The experiments are quite spectacular and attention-grabbing while being relatively simple and easy to perform in any decently supplied physics education laboratory that is equipped with an electrostatic machine (like a Wimshurst machine).

  20. Preliminary tests of the electrostatic plasma accelerator

    NASA Technical Reports Server (NTRS)

    Aston, G.; Acker, T.

    1990-01-01

    This report describes the results of a program to verify an electrostatic plasma acceleration concept and to identify those parameters most important in optimizing an Electrostatic Plasma Accelerator (EPA) thruster based upon this thrust mechanism. Preliminary performance measurements of thrust, specific impulse and efficiency were obtained using a unique plasma exhaust momentum probe. Reliable EPA thruster operation was achieved using one power supply.

  1. Ionic electrostatic excitations along biological membranes

    NASA Astrophysics Data System (ADS)

    Moradi, Afshin

    2011-02-01

    A theoretical analysis of ionic electrostatic excitations of a charged biological membrane is presented within the framework of the fluid theory for surface ions inside and outside the cell, in conjunction with the Poisson's equation. General expressions of dispersion relations are obtained for electrostatic oscillations of intrinsic cellular with different shapes and symmetries.

  2. Electrostatics with Computer-Interfaced Charge Sensors

    ERIC Educational Resources Information Center

    Morse, Robert A.

    2006-01-01

    Computer interfaced electrostatic charge sensors allow both qualitative and quantitative measurements of electrostatic charge but are quite sensitive to charges accumulating on modern synthetic materials. They need to be used with care so that students can correctly interpret their measurements. This paper describes the operation of the sensors,…

  3. Variability of the Influence of Physicochemical Factors Affecting Bacterial Adhesion to Polystyrene Substrata

    PubMed Central

    McEldowney, Sharron; Fletcher, Madilyn

    1986-01-01

    The role of electrostatic and hydrophobic interactions and solid and liquid surface tensions in the adhesion of four bacterial species (Pseudomonas fluorescens, Enterobacter cloacae, Chromobacterium sp., and Flexibacter sp.) to hydrophobic polystyrene petri dishes and to more hydrophilic polystyrene tissue culture dishes was investigated. The effect of electrostatic interactions was investigated by determining the effects of different electrolyte solutions on attachment to and of different electrolyte and pH solutions on detachment from the polystyrene substrate. The significance of solid and liquid surface tensions and hydrophobic interactions was investigated by measuring the effects of different surfactants (including a concentration series of dimethyl sulfoxide) on adhesion and detachment. Adhesion varied with bacterial species, substratum, and electrolyte type and concentration, with no apparent correlation between adhesion and electrolyte valence or concentration. The influence of different pH and detergent solutions on bacterial detachment also varied with species, substratum, pH, and detergent type; however, the greatest degree of detachment of all strains from the surfaces was produced by detergent treatment. The results suggest that adhesion cannot be attributed to any one type of adhesive interaction. There was some evidence for both electrostatic and hydrophobic interactions, but neither interaction could wholly account for the data. PMID:16347145

  4. Using 2,6-dichlorobenzamide (BAM) degrading Aminobacter sp. MSH1 in flow through biofilters--initial adhesion and BAM degradation potentials.

    PubMed

    Albers, Christian Nyrop; Jacobsen, Ole Stig; Aamand, Jens

    2014-01-01

    Micropollutants in groundwater are given significant attention by water companies and authorities due to an increasing awareness that they might be present even above the legal threshold values. As part of our investigations of the possibility to remove the common groundwater pollutant 2,6-dichlorobenzamide (BAM) by introducing the efficient BAM degrader Aminobacter sp. MSH1 into biologically active sand filters, we investigated if the strain adheres to filters containing various filter materials and if the initial adherence and subsequent degradation of BAM could be optimized. We found that most of the inoculated MSH1 cells adhered fast and that parameters like pH and ionic strength had only a minor influence on the adhesion despite huge influence on cell surface hydrophobicity. At the given growth protocol, the MSH1 strain apparently developed a subpopulation that had lost its ability to adhere to the filter materials, which was supported by attempted reinoculation of non-adhered cells. Analysis by quantitative PCR showed that most cells adhered in the top of the filters and that some of these were lost from the filters during initial operation, while insignificant losses occurred after 1 day of operation. The inoculated filters were found to degrade 2.7 μg/L BAM to below 0.1 μg/L at a 1.1-h residence time with insignificant formation of known degradation products. In conclusion, most filter materials and water types should be feasible for inoculation with the MSH1 strain, while more research into degradation at low concentrations and temperatures is needed before this technology is ready for use at actual waterworks.

  5. Control of electrostatic damage to electronic circuits

    SciTech Connect

    Kirk, W.J. Jr.

    1980-03-01

    Static is caused by the flow of materials and people within an environment. The static voltages generated by these movements can degrade or destroy many solid state devices currently being used in sophisticated electronic equipment. Discharge of static voltages through these sensitive devices during assembly operations can lead to a nonfunctional assembly fabricated from parts which previously were acceptable or to later failure of an assembly which was functional after fabrication. Sources of electrostatic charges, equipment and methods for minimizing the generation of electrostatic voltages during the production, assembly and packaging of solid state electronic equipment, and the sensitivity of solid state devices to electrostatic damage are discussed. It is concluded that static awareness is the key to an effective electrostatic damage (ESD) control program, and that production facilities must incorporate electrostatic protection facilities, materials, and processes so that workers can concentrate on producing a high-quality product without having to be overly concerned about ESD procedures. (LCL)

  6. Electrostatic thin film chemical and biological sensor

    DOEpatents

    Prelas, Mark A.; Ghosh, Tushar K.; Tompson, Jr., Robert V.; Viswanath, Dabir; Loyalka, Sudarshan K.

    2010-01-19

    A chemical and biological agent sensor includes an electrostatic thin film supported by a substrate. The film includes an electrostatic charged surface to attract predetermined biological and chemical agents of interest. A charge collector associated with said electrostatic thin film collects charge associated with surface defects in the electrostatic film induced by the predetermined biological and chemical agents of interest. A preferred sensing system includes a charge based deep level transient spectroscopy system to read out charges from the film and match responses to data sets regarding the agents of interest. A method for sensing biological and chemical agents includes providing a thin sensing film having a predetermined electrostatic charge. The film is exposed to an environment suspected of containing the biological and chemical agents. Quantum surface effects on the film are measured. Biological and/or chemical agents can be detected, identified and quantified based on the measured quantum surface effects.

  7. CATALOG OF MATERIALS AS POTENTIAL SOURCES OF INDOOR AIR EMISSIONS - VOLUME 1. INSULATION, WALLCOVERINGS, RESI- LIENT FLOOR COVERINGS, CARPET, ADHESIVES, SEALANTS AND CAULKS, AND PESTICIDES

    EPA Science Inventory

    The report discusses and presents data on constituents and emissions from products that have the potential to impact the indoor air environment. t is a tool to be used by researchers to help organize the study of materials as potential sources of indoor air emissions. ncluded are...

  8. Electrostatic twisted modes in multi-component dusty plasmas

    SciTech Connect

    Ayub, M. K.; Ali, S.; Ikram, M.

    2016-01-15

    Various electrostatic twisted modes are re-investigated with finite orbital angular momentum in an unmagnetized collisionless multi-component dusty plasma, consisting of positive/negative charged dust particles, ions, and electrons. For this purpose, hydrodynamical equations are employed to obtain paraxial equations in terms of density perturbations, while assuming the Gaussian and Laguerre-Gaussian (LG) beam solutions. Specifically, approximated solutions for potential problem are studied by using the paraxial approximation and expressed the electric field components in terms of LG functions. The energy fluxes associated with these modes are computed and corresponding expressions for orbital angular momenta are derived. Numerical analyses reveal that radial/angular mode numbers as well as dust number density and dust charging states strongly modify the LG potential profiles attributed to different electrostatic modes. Our results are important for understanding particle transport and energy transfer due to wave excitations in multi-component dusty plasmas.

  9. 3D RISM theory with fast reciprocal-space electrostatics

    SciTech Connect

    Heil, Jochen; Kast, Stefan M.

    2015-03-21

    The calculation of electrostatic solute-solvent interactions in 3D RISM (“three-dimensional reference interaction site model”) integral equation theory is recast in a form that allows for a computational treatment analogous to the “particle-mesh Ewald” formalism as used for molecular simulations. In addition, relations that connect 3D RISM correlation functions and interaction potentials with thermodynamic quantities such as the chemical potential and average solute-solvent interaction energy are reformulated in a way that calculations of expensive real-space electrostatic terms on the 3D grid are completely avoided. These methodical enhancements allow for both, a significant speedup particularly for large solute systems and a smoother convergence of predicted thermodynamic quantities with respect to box size, as illustrated for several benchmark systems.

  10. Atomistic simulations of liquid water using Lekner electrostatics

    NASA Astrophysics Data System (ADS)

    English, Niall J.; MacElroy, J. M. D.

    Equilibrium molecular dynamics simulations have been performed for liquid water using three different potential models in the NVT and NPT ensembles. The flexible SPC model, the rigid TIP4P model and the rigid/polarizable TIP4P-FQ potential were studied. The Lekner method was used to handle long range electrostatic interactions, and an efficient trivariate cubic spline interpolation method was devised for this purpose. A partitioning of the electrostatic interactions into medium and long range parts was performed, and the concomitant use of multiple timestep techniques led to substantially enhanced computation speeds. The simulations were carried out using 256 molecules in the NVT ensemble at 25°C and 997kgm-3 and in the NPT ensemble at 25°C and 1 bar. Various dynamic, structural, dielectric, rotational and thermodynamic properties were calculated, and it was found that the simulation methodologies performed satisfactorily vis-à-vis previous simulation results and experimental observations.

  11. Use of thermal cycling to reduce adhesion of OTS coated coated MEMS cantilevers

    NASA Astrophysics Data System (ADS)

    Ali, Shaikh M.; Phinney, Leslie M.

    2003-01-01

    °Microelectromechanical systems (MEMS) have enormous potential to contribute in diverse fields such as automotive, health care, aerospace, consumer products, and biotechnology, but successful commercial applications of MEMS are still small in number. Reliability of MEMS is a major impediment to the commercialization of laboratory prototypes. Due to the multitude of MEMS applications and the numerous processing and packaging steps, MEMS are exposed to a variety of environmental conditions, making the prediction of operational reliability difficult. In this paper, we investigate the effects of operating temperature on the in-use adhesive failure of electrostatically actuated MEMS microcantilevers coated with octadecyltrichlorosilane (OTS) films. The cantilevers are subjected to repeated temperature cycles and electrostatically actuated at temperatures between 25°C and 300°C in ambient air. The experimental results indicate that temperature cycling of the OTS coated cantilevers in air reduces the sticking probability of the microcantilevers. The sticking probability of OTS coated cantilevers was highest during heating, which decreased during cooling, and was lowest during reheating. Modifications to the OTS release method to increase its yield are also discussed.

  12. Electrostatic attraction between ionic reverse micelles with dielectric discontinuity

    NASA Astrophysics Data System (ADS)

    Chen, Peilong

    2002-11-01

    We have calculated the thermally-averaged electrostatic attractive potential between two spherical ionic reverse micelles in a medium of a different dielectric constant. Specifically the attractions between the charge density fluctuations in one micelle and interface polarizations on the other are computed. For water-in-oil microemulsions, we find that these contributions completely overwhelm those from correlated fluctuations in charge densities between two micelles.

  13. Instant acting adhesive system

    NASA Technical Reports Server (NTRS)

    Davis, T. R.; Haines, R. C.

    1971-01-01

    Adhesive developes 80 percent of minimum bond strength of 250 psi less than 30 sec after activation is required. Adhesive is stable, handles easily, is a low toxic hazard, and is useful in industrial and domestic prototype bonding and clamping operations.

  14. Bacterial adhesion to glass and metal-oxide surfaces.

    PubMed

    Li, Baikun; Logan, Bruce E

    2004-07-15

    Metal oxides can increase the adhesion of negatively-charged bacteria to surfaces primarily due to their positive charge. However, the hydrophobicity of a metal-oxide surface can also increase adhesion of bacteria. In order to understand the relative contribution of charge and hydrophobicity to bacterial adhesion, we measured the adhesion of 8 strains of bacteria, under conditions of low and high-ionic strength (1 and 100 mM, respectively) to 11 different surfaces and examined adhesion as a function of charge, hydrophobicity (water contact angle) and surface energy. Inorganic surfaces included three uncoated glass surfaces and eight metal-oxide thin films prepared on the upper (non-tin-exposed) side of float glass by chemical vapor deposition. The Gram-negative bacteria differed in lengths of lipopolysaccharides on their outer surface (three Escherichia coli strains), the amounts of exopolysaccharides (two Pseudomonas aeruginosa strains), and their known relative adhesion to sand grains (two Burkholderia cepacia strains). One Gram positive bacterium was also used that had a lower adhesion to glass than these other bacteria (Bacillus subtilis). For all eight bacteria, there was a consistent increase in adhesion between with the type of inorganic surface in the order: float glass exposed to tin (coded here as Si-Sn), glass microscope slide (Si-m), uncoated air-side float glass surface (Si-a), followed by thin films of (Co(1-y-z)Fe(y)Cr(z))3O4, Ti/Fe/O, TiO2, SnO2, SnO2:F, SnO2:Sb, A1(2)O3, and Fe2O3 (the colon indicates metal doping, a slash indicates that the metal is a major component, while the dash is used to distinguish surfaces). Increasing the ionic strength from 1 to 100 mM increased adhesion by a factor of 2.0 +/- 0.6 (73% of the sample results were within the 95% CI) showing electrostatic charge was important in adhesion. However, adhesion was not significantly correlated with bacterial charge and contact angle. Adhesion (A) of the eight strains was

  15. Quantitative and economical assessment of effectiveness of electrostatic pesticide spraying

    NASA Astrophysics Data System (ADS)

    Nishimura, Ryo; Fujita, Satoko; Michihara, Shota; Masuoka, Takashi; Kimura, Toshihiro; Yatsuzuka, Shinji; Anaguchi, Shinobu

    2013-03-01

    Electrostatic pesticide spraying (EPS) improves the adhesion characteristics of the pesticide solution to agricultural crops. If the adhesion characteristics are improved, the requisite amount of the pesticide to be sprayed can be reduced in comparison with the conventional spraying method that uses non-charged pesticide. In this research, disease (rust) control experiments were carried out to substantiate the effectiveness of the EPS from a statistical point of view. We sprayed pesticide to potted Japanese pear trees under calm condition. The numbers of the rust lesions on the pear leaves were counted at fixed intervals after spraying to investigate the difference of the results of the disease control. The t-tests were carried out for the populations of the various spraying times and applied voltages. It was statistically-derived that EPS can reduce the amounts of pesticide to be sprayed by 50 % in comparison with the non-EPS method. It is also estimated from the results that about 55,000 kL year-1 of pesticides can be reduced for the Japanese pear cultivation in Tottori prefecture. Also, this means that the expense of the pear cultivation can be reduced by about 240 million yen (3 million USD) every year in Tottori prefecture by introducing EPS.

  16. Strategies to Minimize Adhesion Formation After Surgery

    PubMed Central

    Lazarou, George; Mondesir, Carlene; Wei, Kai; Khullar, Poonan; Ogden, Lorna

    2011-01-01

    Objectives: To compare the potential for postoperative laparoscopic adhesion formation utilizing either monopolar cautery or ultrasonic energy and to determine whether there is added benefit with the addition of a suspension of hyaluronate/carboxymethylcellulose in saline versus saline alone. Methods: Injuries were induced in rabbits by using monopolar cautery on 1 uterine horn and adjacent sidewall and ultrasonic energy on the opposite. Hyaluronate/ carboxymethylcellulose or saline was added to every other animal. Autopsies were performed after 3 weeks. Clinical and pathologic scoring of adhesions was performed by blinded investigators. Results: A very significant difference occurred in pathologic adhesion scores favoring the ultrasonic scalpel when the animals were treated with saline. However, a borderline significant difference was found in pathologic scores favoring the ultrasonic scalpel compared to the monopolar cautery. There was no significant difference in clinical adhesion scores between the 2 modalities. No significant difference in either score was found with the addition of hyaluronate/carboxymethylcellulose or saline with either instrument. Conclusion: No benefit was found for adhesion prevention with hyaluronate/carboxymethylcellulose. Although no reduction was achieved in clinical adhesions, the ultrasonic scalpel resulted in fewer histologic signs of tissue inflammation in the early postoperative period, suggesting that further clinical adhesions might develop over time with cautery. PMID:21985723

  17. LARC-13 adhesive development

    NASA Technical Reports Server (NTRS)

    Hill, S. G.; Sheppard, C. H.; Johnson, J. C.

    1980-01-01

    A LARC-13 type adhesive system was developed and property data obtained that demonstrated improved thermomechanical properties superior to base LARC-13 adhesive. An improved adhesive for 589 K (600 F) use was developed by physical or chemical modification of LARC-13. The adhesive was optimized for titanium and composite bonding, and a compatible surface preparation for titanium and composite substrates was identified. The data obtained with the improved adhesive system indicated it would meet the 589 K (600 F) properties desired for application on space shuttle components. Average titanium lap shear data were: (1) 21.1 MPa (3355 psi) at RT, (2) 13.0 MPa (1881 psi) at 600 F, and (3) 16.4 MPa (2335) after aging 125 hours at 600 F and tested at 600 F.

  18. Electrostatic field between non-concentric cylinders

    SciTech Connect

    Garcia, M

    2000-01-10

    This report describes a closed-form solution to the electrostatic potential, and the electric field, between non-concentric cylinders, with the inner cylinder charged and the outer cylinder grounded. This problem is an abstraction of the situation of an electron beam within a drift tube. Capacitive and surface current probes on the inner wall of the outer cylinder are used to detect the asymmetry of the field when the beam is off center. The solution of this problem allows for a quantitative relationship between probe-array signals and beam deflection. probe-arrays of this type are called ''beam bugs'' at LLNL. The solution described here is suggested by the analysis presented in [3]. The essential point is that the 2D potential for a line source decreases along a radius as the logarithm of the distance. The non-concentric cylinder problem has a unique profile of this type for each ray from ({rho}, {sigma}) linking the inner cylinder at equipotential V{sub 2}, and the outer cylinder at equipotential 0.

  19. Electrostatic acceleration of helicon plasma using a cusped magnetic field

    SciTech Connect

    Harada, S.; Baba, T.; Uchigashima, A.; Iwakawa, A.; Sasoh, A.; Yokota, S.; Yamazaki, T.; Shimizu, H.

    2014-11-10

    The electrostatic acceleration of helicon plasma is investigated using an electrostatic potential exerted between the ring anode at the helicon source exit and an off-axis hollow cathode in the downstream region. In the downstream region, the magnetic field for the helicon source, which is generated by a solenoid coil, is modified using permanent magnets and a yoke, forming an almost magnetic field-free region surrounded by an annular cusp field. Using a retarding potential analyzer, two primary ion energy peaks, where the lower peak corresponds to the space potential and the higher one to the ion beam, are detected in the field-free region. Using argon as the working gas with a helicon power of 1.5 kW and a mass flow rate of 0.21 mg/s, the ion beam energy is on the order of the applied acceleration voltage. In particular, with an acceleration voltage lower than 150 V, the ion beam energy even exceeds the applied acceleration voltage by an amount on the order of the electron thermal energy at the exit of the helicon plasma source. The ion beam energy profile strongly depends on the helicon power and the applied acceleration voltage. Since by this method the whole working gas from the helicon plasma source can, in principle, be accelerated, this device can be applied as a noble electrostatic thruster for space propulsion.

  20. Electrostatic-free piezoresponse force microscopy

    NASA Astrophysics Data System (ADS)

    Kim, Sungho; Seol, Daehee; Lu, Xiaoli; Alexe, Marin; Kim, Yunseok

    2017-01-01

    Contact and non-contact based atomic force microscopy (AFM) approaches have been extensively utilized to explore various nanoscale surface properties. In most AFM-based measurements, a concurrent electrostatic effect between the AFM tip/cantilever and sample surface can occur. This electrostatic effect often hinders accurate measurements. Thus, it is very important to quantify as well as remove the impact of the electrostatic effect on AFM-based measurements. In this study, we examine the impact of the electrostatic effect on the electromechanical (EM) response in piezoresponse force microscopy as a model AFM mode. We quantitatively studied the effects of increasing the external electric field and reducing the spring constant of a cantilever. Further, we explored ways to minimize the electrostatic effect. The results provide broad guidelines for quantitatively analyzing the EM response as well as, eventually, for obtaining the electrostatic-free EM response. The conclusions can be applied to other AFM-based measurements that are subject to a strong electrostatic effect between the AFM tip/cantilever and sample surface, regardless of contact and non-contact modes.

  1. Electrostatic-free piezoresponse force microscopy

    PubMed Central

    Kim, Sungho; Seol, Daehee; Lu, Xiaoli; Alexe, Marin; Kim, Yunseok

    2017-01-01

    Contact and non-contact based atomic force microscopy (AFM) approaches have been extensively utilized to explore various nanoscale surface properties. In most AFM-based measurements, a concurrent electrostatic effect between the AFM tip/cantilever and sample surface can occur. This electrostatic effect often hinders accurate measurements. Thus, it is very important to quantify as well as remove the impact of the electrostatic effect on AFM-based measurements. In this study, we examine the impact of the electrostatic effect on the electromechanical (EM) response in piezoresponse force microscopy as a model AFM mode. We quantitatively studied the effects of increasing the external electric field and reducing the spring constant of a cantilever. Further, we explored ways to minimize the electrostatic effect. The results provide broad guidelines for quantitatively analyzing the EM response as well as, eventually, for obtaining the electrostatic-free EM response. The conclusions can be applied to other AFM-based measurements that are subject to a strong electrostatic effect between the AFM tip/cantilever and sample surface, regardless of contact and non-contact modes. PMID:28139715

  2. Prevention of peritoneal adhesions: A promising role for gene therapy

    PubMed Central

    Atta, Hussein M

    2011-01-01

    Adhesions are the most frequent complication of abdominopelvic surgery, yet the extent of the problem, and its serious consequences, has not been adequately recognized. Adhesions evolved as a life-saving mechanism to limit the spread of intraperitoneal inflammatory conditions. Three different pathophysiological mechanisms can independently trigger adhesion formation. Mesothelial cell injury and loss during operations, tissue hypoxia and inflammation each promotes adhesion formation separately, and potentiate the effect of each other. Studies have repeatedly demonstrated that interruption of a single pathway does not completely prevent adhesion formation. This review summarizes the pathogenesis of adhesion formation and the results of single gene therapy interventions. It explores the promising role of combinatorial gene therapy and vector modifications for the prevention of adhesion formation in order to stimulate new ideas and encourage rapid advancements in this field. PMID:22171139

  3. DNA/chitosan electrostatic complex.

    PubMed

    Bravo-Anaya, Lourdes Mónica; Soltero, J F Armando; Rinaudo, Marguerite

    2016-07-01

    Up to now, chitosan and DNA have been investigated for gene delivery due to chitosan advantages. It is recognized that chitosan is a biocompatible and biodegradable non-viral vector that does not produce immunological reactions, contrary to viral vectors. Chitosan has also been used and studied for its ability to protect DNA against nuclease degradation and to transfect DNA into several kinds of cells. In this work, high molecular weight DNA is compacted with chitosan. DNA-chitosan complex stoichiometry, net charge, dimensions, conformation and thermal stability are determined and discussed. The influence of external salt and chitosan molecular weight on the stoichiometry is also discussed. The isoelectric point of the complexes was found to be directly related to the protonation degree of chitosan. It is clearly demonstrated that the net charge of DNA-chitosan complex can be expressed in terms of the ratio [NH3(+)]/[P(-)], showing that the electrostatic interactions between DNA and chitosan are the main phenomena taking place in the solution. Compaction of DNA long chain complexed with low molar mass chitosan gives nanoparticles with an average radius around 150nm. Stable nanoparticles are obtained for a partial neutralization of phosphate ionic sites (i.e.: [NH3(+)]/[P(-)] fraction between 0.35 and 0.80).

  4. Electrostatic evaluation of isosteric analogues

    NASA Astrophysics Data System (ADS)

    Sayle, Roger; Nicholls, Anthony

    2006-04-01

    A method is presented for enumerating a large number of isosteric analogues of a ligand from a known protein-ligand complex structure and then rapidly calculating an estimate of their binding energies. This approach takes full advantage of the observed crystal structure, by reusing the atomic co-ordinates determined experimentally for one ligand, to approximate those of similar compounds that have approximately the same shape. By assuming that compounds with similar shapes adopt similar binding poses, and that entropic and protein flexibility effects are approximately constant across such an isosteric series ("the frozen ligand approximation"), it is possible to order their binding affinities relatively accurately. Additionally, the constraint that the atomic coordinates are invariant allows for a dramatic simplification in the Poisson-Boltzmann method used to calculation the electrostatic component of the binding energy. This algorithmic improvement allows for the calculation of tens of thousands of binding energies per second for drug-like molecules, enabling this technique to be used in screening large virtual libraries of isosteric analogues. Most significantly, this procedure is shown to be able to reproduce SAR effects of subtle medicinal chemistry substitutions. Finally, this paper reports the results of the proposed methodology on␣seven model systems; dihydrofolate reductase, Lck␣kinase, ribosome inactivating protein, l-arabinose binding protein, neuraminidase, HIV-1 reverse transcriptase and COX-2.

  5. Electrostatic disturbance forces on a 3-axis drag-free sensor. [for earth satellite accelerometry

    NASA Technical Reports Server (NTRS)

    Hagstrom, T.; Sonnabend, D.; Vijayaraghavan, A.

    1982-01-01

    The electrostatic analysis of a multiple-capacitance 3-axis drag-free sensor is presented in this paper. The instrument consists of a proof-mass (a dense metallic ball) floating freely inside a spherical cavity enclosed by the sensor plates and the shield. Since the ball and the cavity are not necessarily concentric, the problem in three-dimensional potential theory for electrostatics is solved by the method of boundary perturbations and specifically in terms of spherical harmonics. The capacitance outputs of the instrument and the electrostatic forces acting on the system are derived as non-linear functions of the ball position, ball charge and the sensor plate potentials. The instrument sensitivity and cross-coupling effects are discussed. The analysis may also be useful for electrostatic gyros and suspensions.

  6. Adhesion of Spores of Bacillus thuringiensis on a Planar Surface

    SciTech Connect

    Chung, Eunhyea; Kweon, Hyojin; Yiacoumi, Sotira; Lee, Ida; Joy, David Charles; Palumbo, Anthony Vito; Tsouris, Costas

    2010-01-01

    Adhesion of spores of Bacillus thuringiensis (Bt) and spherical silica particles on surfaces was experimentally and theoretically investigated in this study. Topography analysis via atomic force microscopy (AFM) and electron microscopy indicates that Bt spores are rod shaped, {approx}1.3 {mu}m in length and {approx}0.8 {mu}m in diameter. The adhesion force of Bt spores and silica particles on gold-coated glass was measured at various relative humidity (RH) levels by AFM. It was expected that the adhesion force would vary with RH because the individual force components contributing to the adhesion force depend on RH. The adhesion force between a particle and a planar surface in atmospheric environments was modeled as the contribution of three major force components: capillary, van der Waals, and electrostatic interaction forces. Adhesion force measurements for Bt spore (silica particle) and the gold surface system were comparable with calculations. Modeling results show that there is a critical RH value, which depends on the hydrophobicity of the materials involved, below which the water meniscus does not form and the contribution of the capillary force is zero. As RH increases, the van der Waals force decreases while the capillary force increases to a maximum value.

  7. Cyanoacrylate Adhesives in Eye Wounds.

    DTIC Science & Technology

    EYE, *WOUNDS AND INJURIES), (*ADHESIVES, EYE), (*ACRYLIC RESINS, ADHESIVES), CORNEA , HEALING, TISSUES(BIOLOGY), TOLERANCES(PHYSIOLOGY), NECROSIS, SURGICAL SUPPLIES, STRENGTH(PHYSIOLOGY), SURGERY, THERAPY

  8. Electrostatic coating enhances bioavailability of insecticides and breaks pyrethroid resistance in mosquitoes

    PubMed Central

    Andriessen, Rob; Snetselaar, Janneke; Suer, Remco A.; Osinga, Anne J.; Deschietere, Johan; Lyimo, Issa N.; Mnyone, Ladslaus L.; Brooke, Basil D.; Ranson, Hilary; Knols, Bart G. J.; Farenhorst, Marit

    2015-01-01

    Insecticide resistance poses a significant and increasing threat to the control of malaria and other mosquito-borne diseases. We present a novel method of insecticide application based on netting treated with an electrostatic coating that binds insecticidal particles through polarity. Electrostatic netting can hold small amounts of insecticides effectively and results in enhanced bioavailability upon contact by the insect. Six pyrethroid-resistant Anopheles mosquito strains from across Africa were exposed to similar concentrations of deltamethrin on electrostatic netting or a standard long-lasting deltamethrin-coated bednet (PermaNet 2.0). Standard WHO exposure bioassays showed that electrostatic netting induced significantly higher mortality rates than the PermaNet, thereby effectively breaking mosquito resistance. Electrostatic netting also induced high mortality in resistant mosquito strains when a 15-fold lower dose of deltamethrin was applied and when the exposure time was reduced to only 5 s. Because different types of particles adhere to electrostatic netting, it is also possible to apply nonpyrethroid insecticides. Three insecticide classes were effective against strains of Aedes and Culex mosquitoes, demonstrating that electrostatic netting can be used to deploy a wide range of active insecticides against all major groups of disease-transmitting mosquitoes. Promising applications include the use of electrostatic coating on walls or eave curtains and in trapping/contamination devices. We conclude that application of electrostatically adhered particles boosts the efficacy of WHO-recommended insecticides even against resistant mosquitoes. This innovative technique has potential to support the use of unconventional insecticide classes or combinations thereof, potentially offering a significant step forward in managing insecticide resistance in vector-control operations. PMID:26324912

  9. Electrostatic Stabilization Of Growing Protein Crystals

    NASA Technical Reports Server (NTRS)

    Shlichta, Paul J.

    1991-01-01

    Proposed technique produces large crystals in compact, economical apparatus. Report presents concept for supporting protein crystals during growth in microgravity. Yields crystals larger and more-nearly perfect than those grown on Earth. Combines best features of sandwich-drop and electrostatic-levitation methods of support. Drop of protein solution inserted between pair of glass or plastic plates, as in sandwich-drop-support method. Electrostatically charged ring confines drop laterally and shapes it, as in electrostatic technique. Apparatus also made to accommodate several drops simultaneously between same pair of supporting plates. Drops can be inserted and crystals removed through ducts in plates.

  10. Advances in the Pathogenesis of Adhesion Development

    PubMed Central

    Awonuga, Awoniyi O.; Belotte, Jimmy; Abuanzeh, Suleiman; Fletcher, Nicole M.; Diamond, Michael P.

    2014-01-01

    Over the past several years, there has been increasing recognition that pathogenesis of adhesion development includes significant contributions of hypoxia induced at the site of surgery, the resulting oxidative stress, and the subsequent free radical production. Mitochondrial dysfunction generated by surgically induced tissue hypoxia and inflammation can lead to the production of reactive oxygen and nitrogen species as well as antioxidant enzymes such as superoxide dismutase, catalase, and glutathione peroxidase which when optimal have the potential to abrogate mitochondrial dysfunction and oxidative stress, preventing the cascade of events leading to the development of adhesions in injured peritoneum. There is a significant cross talk between the several processes leading to whether or not adhesions would eventually develop. Several of these processes present avenues for the development of measures that can help in abrogating adhesion formation or reformation after intraabdominal surgery. PMID:24520085

  11. Cytotoxicity of denture adhesives.

    PubMed

    de Gomes, Pedro Sousa; Figueiral, Maria Helena; Fernandes, Maria Helena R; Scully, Crispian

    2011-12-01

    Ten commercially available denture adhesives, nine soluble formulations (six creams, three powders) and one insoluble product (pad), were analyzed regarding the cytotoxicity profile in direct and indirect assays using L929 fibroblast cells. In the direct assay, fibroblasts were seeded over the surface of a thick adhesive gel (5%, creams; 2.5%, powders and pad). In the indirect assay, cells were cultured in the presence of adhesive extracts prepared in static and dynamic conditions (0.5-2%, creams; 0.25-1%, powders and pad). Cell toxicity was assessed for cell viability/proliferation (MTT assay) and cell morphology (observation of the F-actin cytoskeleton organization by confocal laser scanning microscopy). Direct contact of the L929 fibroblasts with the thick adhesive gels caused no, or only a slight, decrease in cell viability/proliferation. The adhesive extracts (especially those prepared in dynamic conditions) caused significantly higher growth inhibition of fibroblasts and, in addition, caused dose- and time-dependent effects, throughout the 6-72 h exposure time. Also, dose-dependent effects on cell morphology, with evident disruption of the F-actin cytoskeleton organization, were seen in the presence of most adhesives. In conclusion, the adhesives possessed different degrees of cytotoxicity, but similar dose- and time-dependent biological profiles.

  12. New Distributed Multipole Methods for Accurate Electrostatics for Large-Scale Biomolecular Simultations

    NASA Astrophysics Data System (ADS)

    Sagui, Celeste

    2006-03-01

    An accurate and numerically efficient treatment of electrostatics is essential for biomolecular simulations, as this stabilizes much of the delicate 3-d structure associated with biomolecules. Currently, force fields such as AMBER and CHARMM assign ``partial charges'' to every atom in a simulation in order to model the interatomic electrostatic forces, so that the calculation of the electrostatics rapidly becomes the computational bottleneck in large-scale simulations. There are two main issues associated with the current treatment of classical electrostatics: (i) how does one eliminate the artifacts associated with the point-charges (e.g., the underdetermined nature of the current RESP fitting procedure for large, flexible molecules) used in the force fields in a physically meaningful way? (ii) how does one efficiently simulate the very costly long-range electrostatic interactions? Recently, we have dealt with both of these challenges as follows. In order to improve the description of the molecular electrostatic potentials (MEPs), a new distributed multipole analysis based on localized functions -- Wannier, Boys, and Edminston-Ruedenberg -- was introduced, which allows for a first principles calculation of the partial charges and multipoles. Through a suitable generalization of the particle mesh Ewald (PME) and multigrid method, one can treat electrostatic multipoles all the way to hexadecapoles all without prohibitive extra costs. The importance of these methods for large-scale simulations will be discussed, and examplified by simulations from polarizable DNA models.

  13. Parallel-plate and spherical capacitors in Born-Infeld electrostatics: An analytical study

    NASA Astrophysics Data System (ADS)

    Moayedi, S. K.; Shafabakhsh, M.

    2016-03-01

    In 1934, Max Born and Leopold Infeld suggested and developed a nonlinear modification of Maxwell electrodynamics, in which the electrostatic self-energy of an electron was a finite value. In this paper, after a brief introduction to Lagrangian formulation of Born-Infeld electrodynamics with an external source, the explicit forms of Gauss's law and the electrostatic energy density in Born-Infeld theory are obtained. The capacitance and the stored electrostatic energy for a parallel-plate and spherical capacitors are computed in the framework of Born-Infeld electrostatics. We show that the usual relations U=1/2C_{Maxwell}(triangle φ)2 and U=q2/2C_{Maxwell} are not valid for a capacitor in Born-Infeld electrostatics. Numerical estimations in this research show that the nonlinear corrections to the capacitance and the stored electrostatic energy for a capacitor in Born-Infeld electrostatics are considerable when the potential difference between the plates of a capacitor is very large.

  14. Electrostatic interaction of two charged macroparticles in an equilibrium plasma

    NASA Astrophysics Data System (ADS)

    Filippov, A. V.; Pal', A. F.; Starostin, A. N.

    2015-11-01

    This article is a critical review of publications devoted to studying the electrostatic interaction of two charged macroparticles in an equilibrium plasma. It is shown from an analysis of the force of interaction based on the Maxwell stress tensor that two macroparticles with identical charges in the Poisson-Boltzmann model always repel each other both in isothermal and nonisothermal plasmas. At distances between macroparticles for which the Boltzmann exponents can be linearized, the interaction between macroparticles is completely described by the Debye-Hückel model. The correction to free energy due to the electrostatic interaction in the system of two macroparticles is determined by integrating the correction to the internal energy and by direct calculation of the correction for entropy. It is shown that the free energy coincides with the Yukawa potential. The coincidence of the interaction energy obtained by integrating the force of interaction with the free energy leads to the conclusion about the potential nature of the force of interaction between two macroparticles in an equilibrium plasma. The effect of the outer boundary on the electrostatic interaction force is analyzed; it is shown that the type of interaction depends on the choice of the boundary conditions at the outer boundary. It is also shown that the accumulation of space charge near the outer boundary can lead to the attraction of similarly charged particles at distances comparable with the radius of the outer boundary.

  15. Electrostatic interaction of two charged macroparticles in an equilibrium plasma

    SciTech Connect

    Filippov, A. V. Pal’, A. F.; Starostin, A. N.

    2015-11-15

    This article is a critical review of publications devoted to studying the electrostatic interaction of two charged macroparticles in an equilibrium plasma. It is shown from an analysis of the force of interaction based on the Maxwell stress tensor that two macroparticles with identical charges in the Poisson–Boltzmann model always repel each other both in isothermal and nonisothermal plasmas. At distances between macroparticles for which the Boltzmann exponents can be linearized, the interaction between macroparticles is completely described by the Debye–Hückel model. The correction to free energy due to the electrostatic interaction in the system of two macroparticles is determined by integrating the correction to the internal energy and by direct calculation of the correction for entropy. It is shown that the free energy coincides with the Yukawa potential. The coincidence of the interaction energy obtained by integrating the force of interaction with the free energy leads to the conclusion about the potential nature of the force of interaction between two macroparticles in an equilibrium plasma. The effect of the outer boundary on the electrostatic interaction force is analyzed; it is shown that the type of interaction depends on the choice of the boundary conditions at the outer boundary. It is also shown that the accumulation of space charge near the outer boundary can lead to the attraction of similarly charged particles at distances comparable with the radius of the outer boundary.

  16. Adhesive Contact Sweeper

    NASA Technical Reports Server (NTRS)

    Patterson, Jonathan D.

    1993-01-01

    Adhesive contact sweeper removes hair and particles vacuum cleaner leaves behind, without stirring up dust. Also cleans loose rugs. Sweeper holds commercially available spools of inverted adhesive tape. Suitable for use in environments in which air kept free of dust; optics laboratories, computer rooms, and areas inhabited by people allergic to dust. For carpets, best used in tandem with vacuum cleaner; first pass with vacuum cleaner removes coarse particles, and second pass with sweeper extracts fine particles. This practice extends useful life of adhesive spools.

  17. Focal adhesions in osteoneogenesis

    PubMed Central

    Biggs, M.J.P; Dalby, M.J

    2010-01-01

    As materials technology and the field of tissue engineering advances, the role of cellular adhesive mechanisms, in particular the interactions with implantable devices, becomes more relevant in both research and clinical practice. A key tenet of medical device technology is to use the exquisite ability of biological systems to respond to the material surface or chemical stimuli in order to help develop next-generation biomaterials. The focus of this review is on recent studies and developments concerning focal adhesion formation in osteoneogenesis, with an emphasis on the influence of synthetic constructs on integrin mediated cellular adhesion and function. PMID:21287830

  18. [Endothelial cell adhesion molecules].

    PubMed

    Ivanov, A N; Norkin, I A; Puchin'ian, D M; Shirokov, V Iu; Zhdanova, O Iu

    2014-01-01

    The review presents current data concerning the functional role of endothelial cell adhesion molecules belonging to different structural families: integrins, selectins, cadherins, and the immunoglobulin super-family. In this manuscript the regulatory mechanisms and factors of adhesion molecules expression and distribution on the surface of endothelial cells are discussed. The data presented reveal the importance of adhesion molecules in the regulation of structural and functional state of endothelial cells in normal conditions and in pathology. Particular attention is paid to the importance of these molecules in the processes of physiological and pathological angiogenesis, regulation of permeability of the endothelial barrier and cell transmigration.

  19. Adhesion of Polymer Vesicles

    NASA Astrophysics Data System (ADS)

    Lin, John J.; Bates, Frank S.; Hammer, Daniel A.; Silas, James A.

    2005-07-01

    The adhesion and bending modulus of polybutadiene-poly(ethylene oxide) block copolymer vesicles made from a bidisperse mixture of polymers is measured using micropipette aspiration. The adhesion energy between biotinylated vesicles and avidin beads is modeled by incorporating the extension of the adhesive ligands above the surface brush of the vesicle according to the blob model of bidisperse polymer mixtures of Komura and Safran assuming the polymer brush at the surface of the vesicle is compact. The same model accurately reproduces the scaling of the bending modulus with polymer composition.

  20. Adhesive Bonding for Shelters

    DTIC Science & Technology

    1980-12-01

    weru uvaluated, the type of etch bath " sweetener " and the type of rinse\\water used. The type of etch bath " sweetener " was found to have a dramatic effect...EA9601NW Adhesives on 50521134 Bare Adherenas 39 13 Stress-Durability Behavior Sun-mary 40 14 Effect of Ltch Bath Sweetening Alloy on Interracial Durability...34"’ -,,• , •’• •"• " ,,,,, 9 Adhesive/Primer/Adherend Alloy/Surface Preparation Combinations Adherend OFPL Sweetening Rinse Adhesive:Primer Alloy Alloy

  1. Adhesion family of G protein-coupled receptors and cancer.

    PubMed

    Lin, Hsi-Hsien

    2012-01-01

    The adhesion-class G protein-coupled receptors (adhesion-GPCRs) constitute the second largest GPCR sub-family in humans. Adhesion-GPCRs are defined by the chimeric structure of an unusually large extracellular cell-adhesion domain and a GPCR-like seven-pass transmembrane domain. Adhesion-GPCRs are hence expected to display both cellular adhesion and signaling functions in many biological systems. Adhesion-GPCRs are normally expressed in the central nervous, immune, and reproductive systems in a cell type- or tissue-restricted fashion. However, aberrant expression of distinct adhesion-GPCR molecules has been identified in various human cancers with some of the receptors closely associated with cancer development. Tumor-associated adhesion-GPCRs are thought to involve in tumorigenesis by affecting the growth of tumor cells, angiogenesis, tumor cell migration, invasion and metastasis either positively or negatively. Furthermore, some adhesion-GPCRs are considered potential biomarkers for specific types of cancers. In this review article, the expressional characteristics and functional role of cancer-associated adhesion-GPCRs are discussed in depth.

  2. Flexural-Phonon Scattering Induced by Electrostatic Gating in Graphene

    NASA Astrophysics Data System (ADS)

    Gunst, Tue; Kaasbjerg, Kristen; Brandbyge, Mads

    2017-01-01

    Graphene has an extremely high carrier mobility partly due to its planar mirror symmetry inhibiting scattering by the highly occupied acoustic flexural phonons. Electrostatic gating of a graphene device can break the planar mirror symmetry, yielding a coupling mechanism to the flexural phonons. We examine the effect of the gate-induced one-phonon scattering on the mobility for several gate geometries and dielectric environments using first-principles calculations based on density functional theory and the Boltzmann equation. We demonstrate that this scattering mechanism can be a mobility-limiting factor, and show how the carrier density and temperature scaling of the mobility depends on the electrostatic environment. Our findings may explain the high deformation potential for in-plane acoustic phonons extracted from experiments and, furthermore, suggest a direct relation between device symmetry and resulting mobility.

  3. The GA PEAcH: A Portable Electrostatic Accelerator

    NASA Astrophysics Data System (ADS)

    McClanahan, Patrick; Burch, Ashlyn; Bivins, Quintorious; Garrett, Megan; Jordan, Zachary; Roberts, Rhett; Thomas, Benjamin; Careccia, Sharon; Johnson, Rommie; France, Ralph, III; McGill, K. C., Jr.; Spraker, Mark

    2014-03-01

    In collaboration with the University of North Georgia, we are constructing a portable electrostatic ion accelerator at Georgia College. It will use a model 2JA066280 R.F. ion source from National Electrostatics Corporation to produce ions from gaseous elements and a model AU-100N1 100 kV power supply to produce the accelerating voltage. The linear accelerator will be less than 2 meters in length. The beam energy will be roughly determined by the acceleration voltage. Low energy proton-induced fusion reactions are envisioned for both pure and applied physics research. One potential application is to use the 17 MeV γ-ray from the 7 Li (p , γ)8 Be reaction to help calibrate γ-ray detectors at the Hi γs facility. Supported by the Georgia College Faculty Research Grant Program.

  4. Inertial-Electrostatic Confinement (IEC) Fusion for Space Propulsion

    NASA Technical Reports Server (NTRS)

    Nadler, Jon

    1999-01-01

    An Inertial-Electrostatic Confinement (IEC) device was assembled at the Marshall Space Flight Center (MSFC) Propulsion Research Center (PRC) to study the possibility of using EEC technology for deep space propulsion and power. Inertial-Electrostatic Confinement is capable of containing a nuclear fusion plasma in a series of virtual potential wells. These wells would substantially increase plasma confinement, possibly leading towards a high-gain, breakthrough fusion device. A one-foot in diameter IEC vessel was borrowed from the Fusion Studies Laboratory at the University of Illinois@Urbana-Champaign for the summer. This device was used in initial parameterization studies in order to design a larger, actively cooled device for permanent use at the PRC.

  5. Inertial-Electrostatic Confinement (IEC) Fusion For Space Propulsion

    NASA Technical Reports Server (NTRS)

    Nadler, Jon

    1999-01-01

    An Inertial-Electrostatic Confinement (IEC) device was assembled at the Marshall Space Flight Center (MSFC) Propulsion Research Center (PRC) to study the possibility of using IEC technology for deep space propulsion and power. Inertial-Electrostatic Confinement is capable of containing a nuclear fusion plasma in a series of virtual potential wells. These wells would substantially increase plasma confinement, possibly leading towards a high-gain, breakthrough fusion device. A one-foot in diameter IEC vessel was borrowed from the Fusion Studies Laboratory at the University of Illinois @ Urbana-Champaign for the summer. This device was used in initial parameterization studies in order to design a larger, actively cooled device for permanent use at the PRC.

  6. Charge contribution to patch-charged microparticle adhesion

    NASA Astrophysics Data System (ADS)

    Vallabh, Chaitanya Krishna Prasad; Vahdat, Armin Saeedi; Cetinkaya, Cetin

    2014-11-01

    Microparticle adhesion influenced by electrostatic charge has been a significant research interest for over past three decades or so in a wide spectrum of areas of interest from manufacturing (electrophotography, powder technology, metallurgy, and semi-conductor manufacturing) to natural phenomena (desert sandstorms and northern lights (auroras)). However, over the years, as a result of the strong discrepancies between the experimental adhesion measurements data and theoretical predictions, some key issues regarding the contributors of adhesion forces in charged microparticles and the nature of surface charge distribution still remain unresolved. In the current work, a non-contact ultrasonic approach is presented and employed for understanding the nature of charge distribution on a single microparticle and determining the effect of electrostatic charge on its adhesion in a non-invasive manner. From the vibrational spectra of the charged particle response to the ultrasonic substrate oscillations under various electrostatic loading conditions, three distinct shifting patterns of vibrational (rocking) resonance frequencies are observed for each level of applied substrate surface voltage, implying an un-symmetric force field on the particle, thus depicting non-uniform non-symmetric surface charge distribution on its surface. Also, a simple mathematical model was presented and employed for predicting the equivalent bulk charge on a single microparticle (toner) from resonance frequency shifts. In summary, it is found that the charge levels reported here are consistent with the previously published data, and it is demonstrated that, in a non-invasive manner, non-uniform charge distribution on a single microparticle can be observed and its total charge can be predicted.

  7. Monitoring by Control Technique - Electrostatic Precipitators

    EPA Pesticide Factsheets

    Stationary source emissions monitoring is required to demonstrate that a source is meeting the requirements in Federal or state rules. This page is about electrostatic precipitator control techniques used to reduce pollutant emissions.

  8. The Electrocardiogram as an Example of Electrostatics

    ERIC Educational Resources Information Center

    Hobbie, Russell K.

    1973-01-01

    Develops a simplified electrostatic model of the heart with conduction within the torso neglected to relate electrocardiogram patterns to the charge distribution within the myocardium. Suggests its application to explanation of Coulomb's law in general physics. (CC)

  9. Nonlinear electrostatic drift Kelvin-Helmholtz instability

    NASA Technical Reports Server (NTRS)

    Sharma, Avadhesh C.; Srivastava, Krishna M.

    1993-01-01

    Nonlinear analysis of electrostatic drift Kelvin-Helmholtz instability is performed. It is shown that the analysis leads to the propagation of the weakly nonlinear dispersive waves, and the nonlinear behavior is governed by the nonlinear Burger's equation.

  10. NEW APPROACHES: A novel Kelvin Electrostatic Generator

    NASA Astrophysics Data System (ADS)

    Hill, M.; Jacobs, D. J.

    1997-01-01

    A form of the Kelvin Electrostatic Generator, made from readily available components, is described and an explanation given of how it works. The device described can generate 10 - 12 mm long sparks in air.

  11. Electrostatic discharge control for STDN stations

    NASA Technical Reports Server (NTRS)

    Mckiernan, J.

    1983-01-01

    This manual defines the requirements and control methods necessary to control the effect of electrostatic discharges that damage or destroy electronic equipment components. Test procedures for measuring the effectiveness of the control are included.

  12. Electrostatic correlations near charged planar surfaces

    PubMed Central

    Deng, Mingge; Em Karniadakis, George

    2014-01-01

    Electrostatic correlation effects near charged planar surfaces immersed in a symmetric electrolytes solution are systematically studied by numerically solving the nonlinear six-dimensional electrostatic self-consistent equations. We compare our numerical results with widely accepted mean-field (MF) theory results, and find that the MF theory remains quantitatively accurate only in weakly charged regimes, whereas in strongly charged regimes, the MF predictions deviate drastically due to the electrostatic correlation effects. We also observe a first-order like phase-transition corresponding to the counterion condensation phenomenon in strongly charged regimes, and compute the phase diagram numerically within a wide parameter range. Finally, we investigate the interactions between two likely-charged planar surfaces, which repulse each other as MF theory predicts in weakly charged regimes. However, our results show that they attract each other above a certain distance in strongly charged regimes due to significant electrostatic correlations. PMID:25194382

  13. Under-water adhesion of rigid spheres on soft, charged surfaces

    NASA Astrophysics Data System (ADS)

    Sinha, Shayandev; Das, Siddhartha

    2015-11-01

    Adhesion in a liquid medium is fundamentally important for understanding a myriad of physiological and technological issues such as nanoparticle or bacteria uptake by cells, attachment of viruses on bacterial surfaces, adhesion of a bacteria on a preformed biofilm, biofouling of ships and marine vehicles, and many more. In this paper, we provide a theory to analyze the under-water adhesion of a rigid spherical particle on a soft, charged surface, which is represented as a layer of grafted polyelectrolyte layer (PEL). Our model is based on calculating and minimizing the free energy, appropriately modified to account for the PEL electric double layer (EDL) induced electrostatic energies. The central result of our paper is that the presence of surface charge typically enhances the adhesion, indicated by a larger negative value of the equilibrium free energy and larger value of the equilibrium depth of indentation. Such a behavior can be explained by noting that the lowering of EDL electrostatic energy due to adhesion better balances the increase in elastic energy caused by the adhesion-induced deformation. We anticipate that our theory will provide the hitherto unknown basis of quantifying the effect of surface charge in under-liquid adhesion, which is central to the vast number of phenomena involving charged bio-systems, like cells, bacteria, and viruses.

  14. Electrostatic Beneficiation of Lunar Simulant

    NASA Technical Reports Server (NTRS)

    Trigwell, Steve; Captain, James; Captain, Janine; Arens, Ellen; Quinn, Jacqueline; Calle, Carlos

    2006-01-01

    Electrostatic beneficiation of lunar regolith is a method allowing refinement of specific minerals in the material for processing on the moon. The use of tribocharging the regolith prior to separation was investigated on the lunar simulant MLS-I by passing the dust through static mixers constructed from different materials; aluminum, copper, stainless steel, and polytetrafluoroethylene (PTFE). The amount of charge acquired by the simulant was dependent upon the difference in the work function of the dust and the charging material. XPS and SEM were used to characterize the simulant after it was sieved into five size fractions (> 100 pm, 75-100 pm, 50- 75 pm, 50-25 pm, and < 25 pm), where very little difference in surface composition was observed between the sizes. Samples of the smallest (< 25 pm) and largest (> 100 pm) size fractions were beneficiated through a charge separator using the aluminum (charged the simulant negatively) and PTFE (charged positively) mixers. The mass fractions of the separated simulant revealed that for the larger particle size, significant unipolar charging was observed for both mixers, whereas for the smaller particle sizes, more bipolar charging was observed, probably due to the finer simulant adhering to the inside of the mixers shielding the dust from the charging material. Subsequent XPS analysis of the beneficiated fractions showed the larger particle size fraction having some species differentiation, but very little difference for the smaller.size. Although MLS-1 was made to have similar chemistry to actual lunar dust, its mineralogy is quite different. On-going experiments are using NASA JSC-1 lunar simulant. A vacuum chamber has been constructed, and future experiments are planned in a simulated lunar environment.

  15. Molecular markers of cell adhesion in ameloblastomas. An update

    PubMed Central

    González-González, Rogelio; Molina-Frechero, Nelly; Damian-Matsumura, Pablo

    2014-01-01

    Ameloblastoma is the most common odontogenic tumor of epithelial origin, and though it is of a benign nature, it frequently infiltrates the bone, has a high rate of recurrence and could potentially become malignant. Cellular adhesion potentially plays an important role in the manifestation of these characteristics and in the tumor biology of ameloblastomas. Losses of cell-cell and extracellular matrix adhesion and cohesion are among the first events that occur in the invasion and growth of tumors of epithelial origin. The present review includes a description of the molecules that are involved in cell adhesion as reported for various types of ameloblastomas and discusses the possible roles of these molecules in the biological behaviors of this odontogenic tumor. Knowledge of the complex mechanisms in which these molecules play a role is critical for the research and discovery of future therapeutic targets. Key words:Ameloblastoma, cellular adhesion, molecular markers, cell-cell adhesion, extracellular matrix-cell adhesion. PMID:23986011

  16. Electrostatic camera system functional design study

    NASA Technical Reports Server (NTRS)

    Botticelli, R. A.; Cook, F. J.; Moore, R. F.

    1972-01-01

    A functional design study for an electrostatic camera system for application to planetary missions is presented. The electrostatic camera can produce and store a large number of pictures and provide for transmission of the stored information at arbitrary times after exposure. Preliminary configuration drawings and circuit diagrams for the system are illustrated. The camera system's size, weight, power consumption, and performance are characterized. Tradeoffs between system weight, power, and storage capacity are identified.

  17. Miniature Electrostatic Ion Thruster With Magnet

    NASA Technical Reports Server (NTRS)

    Hartley, Frank T.

    2006-01-01

    A miniature electrostatic ion thruster is proposed that, with one exception, would be based on the same principles as those of the device described in the previous article, "Miniature Bipolar Electrostatic Ion Thruster". The exceptional feature of this thruster would be that, in addition to using electric fields for linear acceleration of ions and electrons, it would use a magnetic field to rotationally accelerate slow electrons into the ion stream to neutralize the ions.

  18. Electrostatic Levitation Furnace for the ISS

    NASA Technical Reports Server (NTRS)

    Murakami, Keiji; Koshikawa, Naokiyo; Shibasaki, Kohichi; Ishikawa, Takehiko; Okada, Junpei; Takada, Tetsuya; Arai, Tatsuya; Fujino, Naoki; Yamaura, Yukiko

    2012-01-01

    JAXA (Japan Aerospace Exploration Agency) has just started the development of Electrostatic Levitation Furnace to be launched in 2014 for the ISS. This furnace can control the sample position with electrostatic force and heat it above 2000 degree Celsius using semiconductor laser from four different directions. The announcement of Opportunity will be issued soon for this furnace. In this paper, we will show the specifications of this furnace and also the development schedule

  19. High-energy capacitance electrostatic micromotors

    NASA Astrophysics Data System (ADS)

    Baginsky, I. L.; Kostsov, E. G.

    2003-03-01

    The design and parameters of a new electrostatic micromotor with high energy output are described. The motor is created by means of microelectronic technology. Its operation is based on the electromechanic energy conversion during the electrostatic rolling of the metallic films (petals) on the ferroelectric film surface. The mathematical simulation of the main characteristics of the rolling process is carried out. The experimentally measured parameters of the petal step micromotors are shown. The motor operation and its efficiency are investigated.

  20. An improved proximity force approximation for electrostatics

    SciTech Connect

    Fosco, Cesar D.; Lombardo, Fernando C.; Mazzitelli, Francisco D.

    2012-08-15

    A quite straightforward approximation for the electrostatic interaction between two perfectly conducting surfaces suggests itself when the distance between them is much smaller than the characteristic lengths associated with their shapes. Indeed, in the so called 'proximity force approximation' the electrostatic force is evaluated by first dividing each surface into a set of small flat patches, and then adding up the forces due two opposite pairs, the contributions of which are approximated as due to pairs of parallel planes. This approximation has been widely and successfully applied in different contexts, ranging from nuclear physics to Casimir effect calculations. We present here an improvement on this approximation, based on a derivative expansion for the electrostatic energy contained between the surfaces. The results obtained could be useful for discussing the geometric dependence of the electrostatic force, and also as a convenient benchmark for numerical analyses of the tip-sample electrostatic interaction in atomic force microscopes. - Highlights: Black-Right-Pointing-Pointer The proximity force approximation (PFA) has been widely used in different areas. Black-Right-Pointing-Pointer The PFA can be improved using a derivative expansion in the shape of the surfaces. Black-Right-Pointing-Pointer We use the improved PFA to compute electrostatic forces between conductors. Black-Right-Pointing-Pointer The results can be used as an analytic benchmark for numerical calculations in AFM. Black-Right-Pointing-Pointer Insight is provided for people who use the PFA to compute nuclear and Casimir forces.