WorldWideScience

Sample records for adhesion dynamics determines

  1. Determination of Water Diffusion Coefficients and Dynamics in Adhesive/ Carbon Fiber Reinforced Epoxy Resin Composite Joints

    Institute of Scientific and Technical Information of China (English)

    WANG Chao; WANG Zhi; WANG Jing; SU Tao

    2007-01-01

    To determinate the water diffusion coefficients and dynamics in adhesive/carbon fiber reinforced epoxy resin composite joints, energy dispersive X-ray spectroscopy analysis(EDX) is used to establish the content change of oxygen in the adhesive in adhesive/carbon fiber reinforced epoxy resin composite joints. As water is made up of oxygen and hydrogen, the water diffusion coefficients and dynamics in adhesive/carbon fiber reinforced epoxy resin composite joints can be obtained from the change in the content of oxygen in the adhesive during humidity aging, via EDX analysis. The authors have calculated the water diffusion coefficients and dynamics in the adhesive/carbon fiber reinforced epoxy resin composite joints with the aid of both energy dispersive X-ray spectroscopy and elemental analysis. The determined results with EDX analysis are almost the same as those determined with elemental analysis and the results also show that the durability of the adhesive/carbon fiber reinforced epoxy resin composite joints subjected to silane coupling agent treatment is better than those subjected to sand paper burnishing treatment and chemical oxidation treatment.

  2. Dynamic analysis of two adhesively bonded rods

    Directory of Open Access Journals (Sweden)

    Kenneth L. Kuttler

    2009-07-01

    Full Text Available This work presents two models for the dynamic analysis of two rods that are adhesively bonded. The first model assumes that the adhesive is an elasto-plastic material and that complete debonding occurs when the stress reaches the yield limit. In the second model the degradation of the adhesive is described by the introduction of material damage. Failure occurs when the material is completely damaged, or the damage reaches a critical floor value. Both models are analyzed and the existence of a weak solution is established for the model with damage. In the quasistatic case, a new condition for adhesion is found as the limit of the adhesive thickness tends to zero.

  3. Adhesion Dynamics in Probing Micro- and Nanoscale Thin Solid Films

    Directory of Open Access Journals (Sweden)

    Xiaoling He

    2008-01-01

    Full Text Available This study focuses on modeling the probe dynamics in scratching and indenting thin solid films at micro- and nanoscales. The model identifies bifurcation conditions that define the stick-slip oscillation patterns of the tip. It is found that the local energy fluctuations as a function of the inelastic deformation, defect formation, material properties, and contact parameters determine the oscillation behavior. The transient variation of the localized function makes the response nonlinear at the adhesion junction. By quantifying the relation between the bifurcation parameters and the oscillation behavior, this model gives a realistic representation of the complex adhesion dynamics. Specifically, the model establishes the link between the stick-slip behavior and the inelastic deformation and the local potentials. This model justifies the experimental observations and the molecular dynamics simulation of the adhesion and friction dynamics in both the micro- and nanoscale contact.

  4. Molecular Dynamics Simulations of Adhesion at Epoxy Interfaces

    Science.gov (United States)

    Frankland, Sarah-Jane V.; Clancy, Thomas C.; Hinkley, J. A.; Gates. T. S.

    2008-01-01

    The effect of moisture on adhesives used in aerospace applications can be modeled with chemically specific techniques such as molecular dynamics simulation. In the present study, the surface energy and work of adhesion are calculated for epoxy surfaces and interfaces, respectively, by using molecular dynamics simulation. Modifications are made to current theory to calculate the work of adhesion at the epoxy-epoxy interface with and without water. Quantitative agreement with experimental values is obtained for the surface energy and work of adhesion at the interface without water. The work of adhesion agrees qualitatively with the experimental values for the interface with water: the magnitude is reduced 15% with respect to the value for the interface without water. A variation of 26% in the magnitude is observed depending on the water configuration at a concentration of 1.6 wt%. The methods and modifications to the method that are employed to obtain these values are expected to be applicable for other epoxy adhesives to determine the effects of moisture uptake on their work of adhesion.

  5. Characteristics of the adhesive determinants of Lactobacillus fermentum 104.

    OpenAIRE

    Henriksson, A; Szewzyk, R.; Conway, P L

    1991-01-01

    The adhesion of Lactobacillus fermentum 104-R and the variant strain 104-S to porcine gastric squamous epithelium was investigated. An epithelium-specific adhesion was detected for strain 104-S; however, strain 104-R expressed enhanced adhesion capacity to the control surfaces of polystyrene and bovine serum albumin. To characterize the adhesive determinants, the bacterial cells were exposed to various treatments. The adhesion pattern of bacterial cells in buffers of pH values ranging from 2 ...

  6. Dynamic mechanical and thermal properties of seven polyurethane adhesives

    Energy Technology Data Exchange (ETDEWEB)

    Hoffman, D.M.

    1981-03-01

    Seven polyurethane adhesives have been developed at Lawrence Livermore National Laboratory (LLNL). These adhesives, designated Halthanes were synthesized because of OSHA restrictions on the use of the curing agent methylene bis(2-chloroaniline). Four of the Halthanes were made from LLNL-developed 4,4'-methylene bis(phenylisocyanate) terminated prepolymers cured with a blend of polyols; three were made from an LLNL-developed prepolymer terminated with Hylene W and cured with aromatic diamines. In this paper the dynamic mechanical and thermal behavior of these seven segmented polyurethanes are discussed. The chemical structure of the hard and soft segments, the concentrations of each block, and the presence of tetrafunctional crosslinker determined the dynamic mechanical and thermal properties of the three types of polyurethane adhesives, 73-, 87-, and 88-series Halthanes studied. Aromatic-aliphatic MDI- butanediol urethane hard segments produce lower modulus (10/sup 6/ Pa) materials in the rubbery region than cyclic unsaturated-aromatic urea hard segments. Incorporation of chemical crosslinks in the hard segments extended the rubbery plateau beyond the hard segment transitions up to temperatures where the polymer begins to degrade. Concentration of hard and soft segments can also be used to control the modulus between the glass transition temperatures of the two blocks.

  7. An adhesion-dependent switch between mechanisms that determine motile cell shape.

    Directory of Open Access Journals (Sweden)

    Erin L Barnhart

    2011-05-01

    Full Text Available Keratocytes are fast-moving cells in which adhesion dynamics are tightly coupled to the actin polymerization motor that drives migration, resulting in highly coordinated cell movement. We have found that modifying the adhesive properties of the underlying substrate has a dramatic effect on keratocyte morphology. Cells crawling at intermediate adhesion strengths resembled stereotypical keratocytes, characterized by a broad, fan-shaped lamellipodium, clearly defined leading and trailing edges, and persistent rates of protrusion and retraction. Cells at low adhesion strength were small and round with highly variable protrusion and retraction rates, and cells at high adhesion strength were large and asymmetrical and, strikingly, exhibited traveling waves of protrusion. To elucidate the mechanisms by which adhesion strength determines cell behavior, we examined the organization of adhesions, myosin II, and the actin network in keratocytes migrating on substrates with different adhesion strengths. On the whole, our results are consistent with a quantitative physical model in which keratocyte shape and migratory behavior emerge from the self-organization of actin, adhesions, and myosin, and quantitative changes in either adhesion strength or myosin contraction can switch keratocytes among qualitatively distinct migration regimes.

  8. INITIAL MICROBIAL ADHESION IS A DETERMINANT FOR THE STRENGTH OF BIOFILM ADHESION

    NARCIS (Netherlands)

    BUSSCHER, HJ; VANDERMEI, HC; Bos, R.R.M.

    1995-01-01

    This paper presents a hypothesis on the importance of initial microbial adhesion in the overall process of biofilm formation. The hypothesis is based on the realization that dynamic shear conditions exist in many environments, such as in the oral cavity, or on rocks and ship hulls. Recognizing that

  9. Adhesive capsulitis and dynamic splinting: a controlled, cohort study

    OpenAIRE

    Willis F Buck; Gaspar Paul D

    2009-01-01

    Abstract Background Adhesive Capsulitis (AC) affects patient of all ages, and stretching protocols are commonly prescribed for this condition. Dynamic splinting has been shown effective in contracture reduction from pathologies including Trismus to plantar fasciitis. The purpose of this study was to examine the efficacy of dynamic splinting on patients with AC. Methods This controlled, cohort study, was conducted at four physical therapy, sports medicine clinics in Texas and California. Sixty...

  10. Dynamic monitoring of changes in endothelial cell-substrate adhesiveness during leukocyte adhesion by microelectrical impedance assay

    Institute of Scientific and Technical Information of China (English)

    Yakun Ge; Tongle Deng; Xiaoxiang Zheng

    2009-01-01

    Adhesion of leukocytes to endothelial cells in inflammation processes leads to changes of endothelial cell-substrate adhesiveness, and understanding of such changes will provide us with important information of inflammation processes. In this study, we used a non-invasive biosensor system referred to as real-time cell electronic sensor (RT-CES) system to monitor the changes in endothelial cell-substrate adhesiveness induced by human monoblastic cell line U937 cell adhesion in a dynamic and quantitative manner. This assay, which is based on cell-substrate impedance readout, is able to monitor transient changes in cell-substrate adhesiveness as a result of U937 cell adhesion. The U937 cell adhesion to endothelial cells was induced by lipopolysaccharide (LPS) in a dose-dependent manner. Although the number of adherent U937 cells to the endothelial cells was verified by a standard assay, the adhesiveness of endothelial cells after addition of U937 cells was monitored by the RT-CES system. Furthermore, focal adhesion kinase protein decrease and F-actin rearrangement in endothelial cells were observed after addition of U937 cells. Our results indicated that the adhesion of U937 cells to LPS-treated endothelial cells reduced the cell adhesiveness to the substrate, and such reduction might facilitate infiltration of leukocytes.

  11. Manipulation of Microobjects Based on Dynamic Adhesion Control

    Directory of Open Access Journals (Sweden)

    Tao Chen

    2012-09-01

    Full Text Available Due to scale effects, microoperation, especially the releasing of microobjects, has been a long‐standing challenge in micromanipulation applications. In this paper a micromanipulation method is presented based on dynamic adhesion control with compound vibration. This adhesion control technique employs inertia force to overcome adhesion force achieving 100% repeatability with releasing accuracy of 4± 0.5μm, which was experimentally quantified through the manipulation of 20‐100μm polystyrene spheres under an optical microscope. The micromanipulation system consists of a microgripper and a piezoelectric ceramics module. The compound vibration comes from the electrostatic actuator and the piezoelectrically driven actuator. Surface and bulk micromachining technology is employed to fabricate the microgripper used in the system from a single crystal silicon wafer. Experimental results confirmed that this adhesion control technique is independent of substrate. Theoretical analyses were conducted to understand the picking up and releasing mechanism. Based on this preliminary study, the micromanipulation system proved to be an effective solution for active picking up and releasing of micromanipulation.

  12. Accurate Method for Determining Adhesion of Cantilever Beams

    Energy Technology Data Exchange (ETDEWEB)

    Michalske, T.A.; de Boer, M.P.

    1999-01-08

    Using surface micromachined samples, we demonstrate the accurate measurement of cantilever beam adhesion by using test structures which are adhered over long attachment lengths. We show that this configuration has a deep energy well, such that a fracture equilibrium is easily reached. When compared to the commonly used method of determining the shortest attached beam, the present method is much less sensitive to variations in surface topography or to details of capillary drying.

  13. Adhesive capsulitis and dynamic splinting: a controlled, cohort study

    Directory of Open Access Journals (Sweden)

    Willis F Buck

    2009-09-01

    Full Text Available Abstract Background Adhesive Capsulitis (AC affects patient of all ages, and stretching protocols are commonly prescribed for this condition. Dynamic splinting has been shown effective in contracture reduction from pathologies including Trismus to plantar fasciitis. The purpose of this study was to examine the efficacy of dynamic splinting on patients with AC. Methods This controlled, cohort study, was conducted at four physical therapy, sports medicine clinics in Texas and California. Sixty-two patients diagnosed with Stage II Adhesive Capsulitis were grouped by intervention. The intervention categories were as follows: Group I (Control; Group II (Physical Therapy exclusively with standardized protocols; Group III; (Shoulder Dynasplint system exclusively; Group IV (Combined treatment with Shoulder Dynasplint and standardized Physical Therapy. The duration of this study was 90 days for all groups, and the main outcome measures were change in active, external rotation. Results Significant difference was found for all treatment groups (p Conclusion The difference for the combined treatment group was attributed to patients' receiving the best PT combined with structured "home therapy" that contributed an additional 90 hours of end-range stretching. This adjunct should be included in the standard of care for adhesive Capsulitis. Trial Registration Trial Number: NCT00873158

  14. Adhesion

    Science.gov (United States)

    As the body moves, tissues or organs inside are normally able to shift around each other. This is because these tissues have ... occur if the adhesions cause an organ or body part to: Twist Pull ... unable to move normally The risk of forming adhesions is high ...

  15. Statics and dynamics of adhesion between two soap bubbles.

    Science.gov (United States)

    Besson, S; Debrégeas, G

    2007-10-01

    An original set-up is used to study the adhesive properties of two hemispherical soap bubbles put into contact. The contact angle at the line connecting the three films is extracted by image analysis of the bubbles profiles. After the initial contact, the angle rapidly reaches a static value slightly larger than the standard 120 degrees angle expected from Plateau rule. This deviation is consistent with previous experimental and theoretical studies: it can be quantitatively predicted by taking into account the finite size of the Plateau border (the liquid volume trapped at the vertex) in the free energy minimization. The visco-elastic adhesion properties of the bubbles are further explored by measuring the deviation Delta theta (d)(t) of the contact angle from the static value as the distance between the two bubbles supports is sinusoidally modulated. It is found to linearly increase with Delta r(c) / r(c) , where r(c) is the radius of the central film and Delta r(c) the amplitude of modulation of this length induced by the displacement of the supports. The in-phase and out-of-phase components of Delta theta (d)(t) with the imposed modulation frequency are systematically probed, which reveals a transition from a viscous to an elastic response of the system with a crossover pulsation of the order 1rad x s(-1). Independent interfacial rheological measurements, obtained from an oscillating bubble experiment, allow us to develop a model of dynamic adhesion which is confronted to our experimental results. The relevance of such adhesive dynamic properties to the rheology of foams is briefly discussed using a perturbative approach to the Princen 2D model of foams. PMID:17955165

  16. Analysis of Adhesive Characteristics of Asphalt Based on Atomic Force Microscopy and Molecular Dynamics Simulation.

    Science.gov (United States)

    Xu, Meng; Yi, Junyan; Feng, Decheng; Huang, Yudong; Wang, Dongsheng

    2016-05-18

    Asphalt binder is a very important building material in infrastructure construction; it is commonly mixed with mineral aggregate and used to produce asphalt concrete. Owing to the large differences in physical and chemical properties between asphalt and aggregate, adhesive bonds play an important role in determining the performance of asphalt concrete. Although many types of adhesive bonding mechanisms have been proposed to explain the interaction forces between asphalt binder and mineral aggregate, few have been confirmed and characterized. In comparison with chemical interactions, physical adsorption has been considered to play a more important role in adhesive bonding between asphalt and mineral aggregate. In this study, the silicon tip of an atomic force microscope was used to represent silicate minerals in aggregate, and a nanoscale analysis of the characteristics of adhesive bonding between asphalt binder and the silicon tip was conducted via an atomic force microscopy (AFM) test and molecular dynamics (MD) simulations. The results of the measurements and simulations could help in better understanding of the bonding and debonding procedures in asphalt-aggregate mixtures during hot mixing and under traffic loading. MD simulations on a single molecule of a component of asphalt and monocrystalline silicon demonstrate that molecules with a higher atomic density and planar structure, such as three types of asphaltene molecules, can provide greater adhesive strength. However, regarding the real components of asphalt binder, both the MD simulations and AFM test indicate that the colloidal structural behavior of asphalt also has a large influence on the adhesion behavior between asphalt and silicon. A schematic model of the interaction between asphalt and silicon is presented, which can explain the effect of aging on the adhesion behavior of asphalt. PMID:27115043

  17. Non-destructive method of determination of elastic properties and adhesion coefficient of different coating materials

    Directory of Open Access Journals (Sweden)

    M. Kubisztal

    2010-12-01

    Full Text Available Purpose: The paper presents a non-destructive method of determination of Young’s modulus and adhesion coefficient of different coating materials (metallic coatings, polymer, composite etc.. Some of the results obtained by applying this method are discussed in detail.Design/methodology/approach: The presented method consists in measuring the dynamic response of the examined material in the form of a flat rectangular bar subjected to external periodic mechanical stress i.e. the so called vibrating reed technique. General equations describing elastic properties of the sample consisting of a substrate and a deposited coating are derived and discussed in detail.Findings: It was shown that the application of the proposed approach to the metallic, polymeric and composite coatings allowed to obtain a quantitative data concerning the change of both the elastic properties and the adhesion coefficient with a change of: coating thickness, measurement temperature, chemical composition of coating, surface preparation or in the case of epoxy resin coatings with a change of curing time or curing temperature.Research limitations/implications: The proposed method can be applied in many scientific problems in the field of coating materials (e.g. elastic properties of porous coating, crystallization of amorphous coating, adhesion of different polymeric coatings.Practical implications: It was shown that the described method can be successfully used in optimisation of some technological processes of deposition of different coatings on metallic substrate.Originality/value: The paper presents methodology of a non-destructive approach to determination of elastic properties and adhesion coefficient of coating materials with an overview of some applications already publish and also the new ones. Especially interesting are the results concerning the influence of surface preparation on adhesion coefficient which are published for the first time.

  18. Stimuli-Responsive Reversible Two-Level Adhesion from a Structurally Dynamic Shape-Memory Polymer.

    Science.gov (United States)

    Michal, Brian T; Spencer, Emily J; Rowan, Stuart J

    2016-05-01

    A shape-memory adhesive has been prepared that exhibits two levels of reversible adhesion. The adhesive is a semicrystalline cross-linked polymer that contains dynamic disulfide bonds. Melting of the crystalline regions via heat causes a drop in the modulus of the material facilitating wetting of the substrate as well as enhancing the surface contact area with the substrate, which result in the formation of an adhesive bond. Exposure to higher heat or UV light results in dynamic exchange of the disulfide bonds, which yields a further drop in the modulus/viscosity that improves surface wetting/contact and strengthens the adhesive bond. This improvement in adhesion is shown to apply over different substrates, contact forces, and deformation modes. Furthermore, the adhesive acts as a thermal shape-memory material and can be used to create joints that can reposition themselves upon application of heat.

  19. Cellular adhesome screen identifies critical modulators of focal adhesion dynamics, cellular traction forces and cell migration behaviour.

    Science.gov (United States)

    Fokkelman, Michiel; Balcıoğlu, Hayri E; Klip, Janna E; Yan, Kuan; Verbeek, Fons J; Danen, Erik H J; van de Water, Bob

    2016-01-01

    Cancer cells migrate from the primary tumour into surrounding tissue in order to form metastasis. Cell migration is a highly complex process, which requires continuous remodelling and re-organization of the cytoskeleton and cell-matrix adhesions. Here, we aimed to identify genes controlling aspects of tumour cell migration, including the dynamic organization of cell-matrix adhesions and cellular traction forces. In a siRNA screen targeting most cell adhesion-related genes we identified 200+ genes that regulate size and/or dynamics of cell-matrix adhesions in MCF7 breast cancer cells. In a subsequent secondary screen, the 64 most effective genes were evaluated for growth factor-induced cell migration and validated by tertiary RNAi pool deconvolution experiments. Four validated hits showed significantly enlarged adhesions accompanied by reduced cell migration upon siRNA-mediated knockdown. Furthermore, loss of PPP1R12B, HIPK3 or RAC2 caused cells to exert higher traction forces, as determined by traction force microscopy with elastomeric micropillar post arrays, and led to considerably reduced force turnover. Altogether, we identified genes that co-regulate cell-matrix adhesion dynamics and traction force turnover, thereby modulating overall motility behaviour. PMID:27531518

  20. Dynamic force spectroscopy to probe adhesion strength of living cells

    OpenAIRE

    Prechtel, K.; Bausch, A. R.; Marchi-Artzner, V.; Kantlehner, M.; Kessler, H; Merkel, R

    2002-01-01

    We studied the mechanical strength of the adhesion of living cells to model membranes. The latter contained a RGD lipopeptide which is a high affinity binding site for a cell adhesion molecule (integrin alpha(V)beta(3)). Cells adhered specifically to the vesicles. We used micropipette aspiration for breaking this adhesion with well defined forces. Systematic variation of the rate of force application revealed pronounced kinetic effects. The dependence of the detachment forces on the loading r...

  1. Determination of mode of fracture of adhesive restorative materials. An invitro study.

    OpenAIRE

    Nayak Ullal; Suasha P

    2002-01-01

    In the present invitro study, four adhesive restorative materials were evaluated for the determination of mode of fracture. The four materials chosen were TPH composite resin, Dyract, Fuji II LC and Fuji II. The mode of fracture was determined at a magnification of 10X. The TPH composite resin and Dyract showed adhesive fracture whereas the glass ionomer group showed cohesive fracture.

  2. Dynamic interplay between adhesive and lateral E-cadherin dimers

    DEFF Research Database (Denmark)

    Klingelhöfer, Jörg; Laur, Oscar Y; Troyanovsky, Regina B;

    2002-01-01

    M. The disappearance of adhesive dimers was counterbalanced by an increase in Trp156-dependent lateral dimers. Increasing the calcium concentration to a normal level rapidly restored the original balance between adhesive and lateral dimers. We also present evidence that E-cadherin dimers in vivo have a short lifetime...

  3. Dynamic cell adhesion and migration on nanoscale grooved substrates.

    Science.gov (United States)

    Lamers, E; te Riet, J; Domanski, M; Luttge, R; Figdor, C G; Gardeniers, J G E; Walboomers, X F; Jansen, J A

    2012-01-01

    Organised nanotopography mimicking the natural extracellular matrix can be used to control morphology, cell motility, and differentiation. However, it is still unknown how specific cell types react with specific patterns. Both initial adhesion and preferential cell migration may be important to initiate and increase cell locomotion and coverage with cells, and thus achieve an enhanced wound healing response around an implantable material. Therefore, the aim of this study was to evaluate how MC3T3-E1 osteoblast initial adhesion and directional migration are influenced by nanogrooves with pitches ranging from 150 nm up to 1000 nm. In this study, we used a multi-patterned substrate with five different groove patterns and a smooth area with either a concentric or radial orientation. Initial cell adhesion measurements after 10 s were performed using atomic force spectroscopy-assisted single-cell force spectroscopy, and demonstrated that nascent cell adhesion was highly induced by a 600 nm pitch and reduced by a 150 nm pitch. Addition of RGD peptide significantly reduced adhesion, indicating that integrins and cell adhesive proteins (e.g. fibronectin or vitronectin) are key factors in specific cell adhesion on nanogrooved substrates. Also, cell migration was highly dependent on the groove pitch; the highest directional migration parallel to the grooves was observed on a 600 nm pitch, whereas a 150 nm pitch restrained directional cell migration. From this study, we conclude that grooves with a pitch of 600 nm may be favourable to enhance fast wound closure, thereby promoting tissue regeneration.

  4. State diagram for adhesion dynamics of deformable capsules under shear flow.

    Science.gov (United States)

    Luo, Zheng Yuan; Bai, Bo Feng

    2016-08-17

    Due to the significance of understanding the underlying mechanisms of cell adhesion in biological processes and cell capture in biomedical applications, we numerically investigate the adhesion dynamics of deformable capsules under shear flow by using a three-dimensional computational fluid dynamic model. This model is based on the coupling of the front tracking-finite element method for elastic mechanics of the capsule membrane and the adhesion kinetics simulation for adhesive interactions between capsules and functionalized surfaces. Using this model, three distinct adhesion dynamic states are predicted, such as detachment, rolling and firm-adhesion. Specifically, the effects of capsule deformability quantified by the capillary number on the transitions of these three dynamic states are investigated by developing an adhesion dynamic state diagram for the first time. At low capillary numbers (e.g. Ca numbers (e.g. 0.0075 number exceeds a critical value (e.g. Ca = 0.0175), the rolling state no longer appears, since capsules exhibit large deviation from the spherical shape. PMID:27492192

  5. Local 3D matrix microenvironment regulates cell migration through spatiotemporal dynamics of contractility-dependent adhesions

    Science.gov (United States)

    Doyle, Andrew D.; Carvajal, Nicole; Jin, Albert; Matsumoto, Kazue; Yamada, Kenneth M.

    2015-11-01

    The physical properties of two-dimensional (2D) extracellular matrices (ECMs) modulate cell adhesion dynamics and motility, but little is known about the roles of local microenvironmental differences in three-dimensional (3D) ECMs. Here we generate 3D collagen gels of varying matrix microarchitectures to characterize their regulation of 3D adhesion dynamics and cell migration. ECMs containing bundled fibrils demonstrate enhanced local adhesion-scale stiffness and increased adhesion stability through balanced ECM/adhesion coupling, whereas highly pliable reticular matrices promote adhesion retraction. 3D adhesion dynamics are locally regulated by ECM rigidity together with integrin/ECM association and myosin II contractility. Unlike 2D migration, abrogating contractility stalls 3D migration regardless of ECM pore size. We find force is not required for clustering of activated integrins on 3D native collagen fibrils. We propose that efficient 3D migration requires local balancing of contractility with ECM stiffness to stabilize adhesions, which facilitates the detachment of activated integrins from ECM fibrils.

  6. Comparative dynamics of retrograde actin flow and focal adhesions: formation of nascent adhesions triggers transition from fast to slow flow.

    Directory of Open Access Journals (Sweden)

    Antonina Y Alexandrova

    Full Text Available Dynamic actin network at the leading edge of the cell is linked to the extracellular matrix through focal adhesions (FAs, and at the same time it undergoes retrograde flow with different dynamics in two distinct zones: the lamellipodium (peripheral zone of fast flow, and the lamellum (zone of slow flow located between the lamellipodium and the cell body. Cell migration involves expansion of both the lamellipodium and the lamellum, as well as formation of new FAs, but it is largely unknown how the position of the boundary between the two flow zones is defined, and how FAs and actin flow mutually influence each other. We investigated dynamic relationship between focal adhesions and the boundary between the two flow zones in spreading cells. Nascent FAs first appeared in the lamellipodium. Within seconds after the formation of new FAs, the rate of actin flow decreased locally, and the lamellipodium/lamellum boundary advanced towards the new FAs. Blocking fast actin flow with cytochalasin D resulted in rapid dissolution of nascent FAs. In the absence of FAs (spreading on poly-L-lysine-coated surfaces retrograde flow was uniform and the velocity transition was not observed. We conclude that formation of FAs depends on actin dynamics, and in its turn, affects the dynamics of actin flow by triggering transition from fast to slow flow. Extension of the cell edge thus proceeds through a cycle of lamellipodium protrusion, formation of new FAs, advance of the lamellum, and protrusion of the lamellipodium from the new base.

  7. Comparative dynamics of retrograde actin flow and focal adhesions: formation of nascent adhesions triggers transition from fast to slow flow.

    Science.gov (United States)

    Alexandrova, Antonina Y; Arnold, Katya; Schaub, Sébastien; Vasiliev, Jury M; Meister, Jean-Jacques; Bershadsky, Alexander D; Verkhovsky, Alexander B

    2008-01-01

    Dynamic actin network at the leading edge of the cell is linked to the extracellular matrix through focal adhesions (FAs), and at the same time it undergoes retrograde flow with different dynamics in two distinct zones: the lamellipodium (peripheral zone of fast flow), and the lamellum (zone of slow flow located between the lamellipodium and the cell body). Cell migration involves expansion of both the lamellipodium and the lamellum, as well as formation of new FAs, but it is largely unknown how the position of the boundary between the two flow zones is defined, and how FAs and actin flow mutually influence each other. We investigated dynamic relationship between focal adhesions and the boundary between the two flow zones in spreading cells. Nascent FAs first appeared in the lamellipodium. Within seconds after the formation of new FAs, the rate of actin flow decreased locally, and the lamellipodium/lamellum boundary advanced towards the new FAs. Blocking fast actin flow with cytochalasin D resulted in rapid dissolution of nascent FAs. In the absence of FAs (spreading on poly-L-lysine-coated surfaces) retrograde flow was uniform and the velocity transition was not observed. We conclude that formation of FAs depends on actin dynamics, and in its turn, affects the dynamics of actin flow by triggering transition from fast to slow flow. Extension of the cell edge thus proceeds through a cycle of lamellipodium protrusion, formation of new FAs, advance of the lamellum, and protrusion of the lamellipodium from the new base. PMID:18800171

  8. Dynamic cell adhesion and migration on nanoscale grooved substrates

    Directory of Open Access Journals (Sweden)

    E Lamers

    2012-03-01

    Full Text Available Organised nanotopography mimicking the natural extracellular matrix can be used to control morphology, cell motility, and differentiation. However, it is still unknown how specific cell types react with specific patterns. Both initial adhesion and preferential cell migration may be important to initiate and increase cell locomotion and coverage with cells, and thus achieve an enhanced wound healing response around an implantable material. Therefore, the aim of this study was to evaluate how MC3T3-E1 osteoblast initial adhesion and directional migration are influenced by nanogrooves with pitches ranging from 150 nm up to 1000 nm. In this study, we used a multi-patterned substrate with five different groove patterns and a smooth area with either a concentric or radial orientation. Initial cell adhesion measurements after 10 s were performed using atomic force spectroscopy-assisted single-cell force spectroscopy, and demonstrated that nascent cell adhesion was highly induced by a 600 nm pitch and reduced by a 150 nm pitch. Addition of RGD peptide significantly reduced adhesion, indicating that integrins and cell adhesive proteins (e.g. fibronectin or vitronectin are key factors in specific cell adhesion on nanogrooved substrates. Also, cell migration was highly dependent on the groove pitch; the highest directional migration parallel to the grooves was observed on a 600 nm pitch, whereas a 150 nm pitch restrained directional cell migration. From this study, we conclude that grooves with a pitch of 600 nm may be favourable to enhance fast wound closure, thereby promoting tissue regeneration.

  9. Dynamic Cell Adhesion and Migration on Nanoscale Grooved Substrates

    NARCIS (Netherlands)

    Lamers, E.; Riet, te J.; Domanski, M.; Luttge, R.; Figdor, C.G.; Gardeniers, J.G.E.; Walboomers, X.F.; Jansen, J.A.

    2012-01-01

    Organised nanotopography mimicking the natural extracellular matrix can be used to control morphology, cell motility, and differentiation. However, it is still unknown how specific cell types react with specific patterns. Both initial adhesion and preferential cell migration may be important to init

  10. Dynamic cell adhesion and migration on nanoscale grooved substrates.

    NARCIS (Netherlands)

    Lamers, E.; Riet, J. te; Domanski, M.; Luttge, R.; Figdor, C.G.; Gardeniers, J.G.E.; Walboomers, X.F.; Jansen, J.B.M.J.

    2012-01-01

    Organised nanotopography mimicking the natural extracellular matrix can be used to control morphology, cell motility, and differentiation. However, it is still unknown how specific cell types react with specific patterns. Both initial adhesion and preferential cell migration may be important to init

  11. Effects of adhesion dynamics and substrate compliance on the shape and motility of crawling cells.

    Directory of Open Access Journals (Sweden)

    Falko Ziebert

    Full Text Available Computational modeling of eukaryotic cells moving on substrates is an extraordinarily complex task: many physical processes, such as actin polymerization, action of motors, formation of adhesive contacts concomitant with both substrate deformation and recruitment of actin etc., as well as regulatory pathways are intertwined. Moreover, highly nontrivial cell responses emerge when the substrate becomes deformable and/or heterogeneous. Here we extended a computational model for motile cell fragments, based on an earlier developed phase field approach, to account for explicit dynamics of adhesion site formation, as well as for substrate compliance via an effective elastic spring. Our model displays steady motion vs. stick-slip transitions with concomitant shape oscillations as a function of the actin protrusion rate, the substrate stiffness, and the rates of adhesion. Implementing a step in the substrate's elastic modulus, as well as periodic patterned surfaces exemplified by alternating stripes of high and low adhesiveness, we were able to reproduce the correct motility modes and shape phenomenology found experimentally. We also predict the following nontrivial behavior: the direction of motion of cells can switch from parallel to perpendicular to the stripes as a function of both the adhesion strength and the width ratio of adhesive to non-adhesive stripes.

  12. Dynamic testing of adhesive joints using a shock testing machine

    NARCIS (Netherlands)

    Aanhold, J.E. van; Weersink, A.F.J.; Ludolphy, J.W.L.

    1998-01-01

    A light-weight shock testing machine, designed for type approval testing of naval equipment up to 300 kg mass, has been modified into a dynamic tensile test rig. This enables to test structural details for high rate dynamic tensile loadings such as occur during underwater shock. The maximum capacity

  13. Lateral shear forces applied to cells with single elastic micropillars to influence focal adhesion dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Heil, Patrick; Spatz, Joachim P, E-mail: spatz@mf.mpg.d [Department of New Materials and Biosystems, Max Planck Institute for Metals Research, Heisenbergstrasse 3, D-70569 Stuttgart (Germany); Department of Biophysical Chemistry, University of Heidelberg, Heisenbergstrasse 3, D-70569 Stuttgart (Germany)

    2010-05-19

    Focal adhesions (FAs) are important adhesion sites between eukaryotic cells and the extracellular matrix, their size depending on the locally applied force. To quantitatively study the mechanosensitivity of FAs, we induce their growth and disassembly by varying the distribution of intracellular stress. We present a novel method for micromanipulation of living cells to explore the dynamics of focal adhesion (FA) assembly under force. Fibroblasts are sheared laterally to their adhesion surface with single PDMS micropillars in order to apply laterally stretch or compression to focal adhesions. This allows for measuring the shear force exerted by the micropillar and correlates it with FA length and growth velocity. Furthermore, we analyze the resulting dynamics of FA molecules (paxillin) and compare intensity profiles along FAs before and after the application of external force. The responses of stretched and relaxed FAs differ fundamentally: relaxed and compressed FAs disassemble isotropically and show no length variation while stretched FAs grow unisotropically in the direction of the applied force and show protein influx only at their front.

  14. Light-melt adhesive based on dynamic carbon frameworks in a columnar liquid-crystal phase

    Science.gov (United States)

    Saito, Shohei; Nobusue, Shunpei; Tsuzaka, Eri; Yuan, Chunxue; Mori, Chigusa; Hara, Mitsuo; Seki, Takahiro; Camacho, Cristopher; Irle, Stephan; Yamaguchi, Shigehiro

    2016-07-01

    Liquid crystal (LC) provides a suitable platform to exploit structural motions of molecules in a condensed phase. Amplification of the structural changes enables a variety of technologies not only in LC displays but also in other applications. Until very recently, however, a practical use of LCs for removable adhesives has not been explored, although a spontaneous disorganization of LC materials can be easily triggered by light-induced isomerization of photoactive components. The difficulty of such application derives from the requirements for simultaneous implementation of sufficient bonding strength and its rapid disappearance by photoirradiation. Here we report a dynamic molecular LC material that meets these requirements. Columnar-stacked V-shaped carbon frameworks display sufficient bonding strength even during heating conditions, while its bonding ability is immediately lost by a light-induced self-melting function. The light-melt adhesive is reusable and its fluorescence colour reversibly changes during the cycle, visualizing the bonding/nonbonding phases of the adhesive.

  15. A simplified model for dynamics of cell rolling and cell-surface adhesion

    Energy Technology Data Exchange (ETDEWEB)

    Cimrák, Ivan, E-mail: ivan.cimrak@fri.uniza.sk [Cell-in-fluid Research Group, http://cell-in-fluid.fri.uniza.sk Faculty of Management Science and Informatics, University of Žilina Univerzitná 8215/1, 010 26 Žilina (Slovakia)

    2015-03-10

    We propose a three dimensional model for the adhesion and rolling of biological cells on surfaces. We study cells moving in shear flow above a wall to which they can adhere via specific receptor-ligand bonds based on receptors from selectin as well as integrin family. The computational fluid dynamics are governed by the lattice-Boltzmann method. The movement and the deformation of the cells is described by the immersed boundary method. Both methods are fully coupled by implementing a two-way fluid-structure interaction. The adhesion mechanism is modelled by adhesive bonds including stochastic rules for their creation and rupture. We explore a simplified model with dissociation rate independent of the length of the bonds. We demonstrate that this model is able to resemble the mesoscopic properties, such as velocity of rolling cells.

  16. Assessment of Fevicol (adhesive Drying Process through Dynamic Speckle Techniques

    Directory of Open Access Journals (Sweden)

    Mohammad Z. Ansari

    2015-04-01

    Full Text Available Dynamic laser speckle (or biospeckle analysis is a useful measurement tool to analyze micro-motion on a sample surface via temporal statistics based on a sequence of speckle images. The aim of this work was to evaluate the use of dynamic speckles as an alternative tool to monitoring Fevicol drying process. Experimental demonstration of intensity-based algorithm to monitor Fevicol drying process is reported. The experiment was explored with the technique called Inertia Moment of co-occurrence matrix. The results allowed verifying the drying process and it was possible to observe different activity stages during the drying process. Statistical Tukey test at 5% significance level allowed differentiating different stages of drying. In conclusion, speckle activity, measured by the Inertia Moment, can be used to monitor drying processes of the Fevicol.

  17. Dynamic Regulation of Activated Leukocyte Cell Adhesion Molecule–mediated Homotypic Cell Adhesion through the Actin CytoskeletonV⃞

    OpenAIRE

    Nelissen, Judith M. D. T.; Peters, Inge M.; de Grooth, Bart G.; Van Kooyk, Yvette; Figdor, Carl G.

    2000-01-01

    Restricted expression of activated leukocyte cell adhesion molecule (ALCAM) by hematopoietic cells suggests an important role in the immune system and hematopoiesis. To get insight into the mechanisms that control ALCAM-mediated adhesion we have investigated homotypic ALCAM–ALCAM interactions. Here, we demonstrate that the cytoskeleton regulates ALCAM-mediated cell adhesion because inhibition of actin polymerization by cytochalasin D (CytD) strongly induces homotypic ALCAM–ALCAM interactions....

  18. Conformational Dynamics of the Focal Adhesion Targeting Domain Control Specific Functions of Focal Adhesion Kinase in Cells

    KAUST Repository

    Kadaré, Gress

    2015-01-02

    Focal adhesion (FA) kinase (FAK) regulates cell survival and motility by transducing signals from membrane receptors. The C-terminal FA targeting (FAT) domain of FAK fulfils multiple functions, including recruitment to FAs through paxillin binding. Phosphorylation of FAT on Tyr925 facilitates FA disassembly and connects to the MAPK pathway through Grb2 association, but requires dissociation of the first helix (H1) of the four-helix bundle of FAT. We investigated the importance of H1 opening in cells by comparing the properties of FAK molecules containing wild-type or mutated FAT with impaired or facilitated H1 openings. These mutations did not alter the activation of FAK, but selectively affected its cellular functions, including self-association, Tyr925 phosphorylation, paxillin binding, and FA targeting and turnover. Phosphorylation of Tyr861, located between the kinase and FAT domains, was also enhanced by the mutation that opened the FAT bundle. Similarly phosphorylation of Ser910 by ERK in response to bombesin was increased by FAT opening. Although FAK molecules with the mutation favoring FAT opening were poorly recruited at FAs, they efficiently restored FA turnover and cell shape in FAK-deficient cells. In contrast, the mutation preventing H1 opening markedly impaired FAK function. Our data support the biological importance of conformational dynamics of the FAT domain and its functional interactions with other parts of the molecule.

  19. Dynamic Switch Between Two Adhesion Phenotypes in Colorectal Cancer Cells.

    Science.gov (United States)

    Geng, Yue; Chandrasekaran, Siddarth; Agastin, Sivaprakash; Li, Jiahe; King, Michael R

    2014-01-01

    The hematogenous metastatic cascade is mediated by the interaction of cancer cells and the endothelial cell lining of blood vessels. In this work, we examine the colon cancer cell line COLO 205, which grows simultaneously in both adherent and suspended states in culture and can serve as a good model for studying tumor heterogeneity. The two subpopulations of cells have different molecular characteristics despite being from the same parent cell line. We found that the ratio of adherent to suspended cells in culture is maintained at 7:3 (equilibrium ratio). The ratio was maintained even when we separate the two populations and culture them separately. After 8 h in culture the equilibrium was achieved only from either adherent or suspended population. The adherent cells were found to express less E-selectin binding glycans and demonstrated significantly weaker interaction with E-selectin under flow than the suspended cells. Manipulation of the epithelial-mesenchymal transition (EMT) markers β-catenin and E-cadherin expression, either by siRNA knockdown of β-catenin or incubation with E-cadherin antibody-coated microbeads, shifted the ratio of adherent to suspended cells to 9:1. Interestingly, human plasma supplemented media shifted the ratio of adherent to suspended cells in the opposite direction to 1:9, favoring the suspended state. The dynamic COLO 205 population switch presents unique differential phenotypes of their subpopulations and could serve as a good model for studying cell heterogeneity and the EMT process in vitro. PMID:24575161

  20. Metastable states and activated dynamics in thin-film adhesion to patterned surfaces

    OpenAIRE

    Lindström, Stefan B.; Johansson, Lars; Karlsson, Nils R.

    2014-01-01

    We consider adhesion due to London–van der Waals attraction between a thin film and a patterned surface with nanometer asperities. Depending on the surface topography and the stiffness of the film, three regimes of adhesion are identified: complete contact adhesion, partial contact adhesion, and glassy adhesion. For complete contact adhesion, the film conforms to the undulations of the surface, whereas for partial contact and glassy adhesion, the adhesive interface breaks down into microscopi...

  1. Changes in membrane sphingolipid composition modulate dynamics and adhesion of integrin nanoclusters.

    Science.gov (United States)

    Eich, Christina; Manzo, Carlo; de Keijzer, Sandra; Bakker, Gert-Jan; Reinieren-Beeren, Inge; García-Parajo, Maria F; Cambi, Alessandra

    2016-01-01

    Sphingolipids are essential constituents of the plasma membrane (PM) and play an important role in signal transduction by modulating clustering and dynamics of membrane receptors. Changes in lipid composition are therefore likely to influence receptor organisation and function, but how this precisely occurs is difficult to address given the intricacy of the PM lipid-network. Here, we combined biochemical assays and single molecule dynamic approaches to demonstrate that the local lipid environment regulates adhesion of integrin receptors by impacting on their lateral mobility. Induction of sphingomyelinase (SMase) activity reduced sphingomyelin (SM) levels by conversion to ceramide (Cer), resulting in impaired integrin adhesion and reduced integrin mobility. Dual-colour imaging of cortical actin in combination with single molecule tracking of integrins showed that this reduced mobility results from increased coupling to the actin cytoskeleton brought about by Cer formation. As such, our data emphasizes a critical role for the PM local lipid composition in regulating the lateral mobility of integrins and their ability to dynamically increase receptor density for efficient ligand binding in the process of cell adhesion. PMID:26869100

  2. Adhesion kinetics of human primary monocytes, dendritic cells, and macrophages: Dynamic cell adhesion measurements with a label-free optical biosensor and their comparison with end-point assays.

    Science.gov (United States)

    Orgovan, Norbert; Ungai-Salánki, Rita; Lukácsi, Szilvia; Sándor, Noémi; Bajtay, Zsuzsa; Erdei, Anna; Szabó, Bálint; Horvath, Robert

    2016-01-01

    Monocytes, dendritic cells (DCs), and macrophages (MFs) are closely related immune cells that differ in their main functions. These specific functions are, to a considerable degree, determined by the differences in the adhesion behavior of the cells. To study the inherently and essentially dynamic aspects of the adhesion of monocytes, DCs, and MFs, dynamic cell adhesion assays were performed with a high-throughput label-free optical biosensor [Epic BenchTop (BT)] on surfaces coated with either fibrinogen (Fgn) or the biomimetic copolymer PLL-g-PEG-RGD. Cell adhesion profiles typically reached their maximum at ∼60 min after cell seeding, which was followed by a monotonic signal decrease, indicating gradually weakening cell adhesion. According to the biosensor response, cell types could be ordered by increasing adherence as monocytes, MFs, and DCs. Notably, all three cell types induced a larger biosensor signal on Fgn than on PLL-g-PEG-RGD. To interpret this result, the molecular layers were characterized by further exploiting the potentials of the biosensor: by measuring the adsorption signal induced during the surface coating procedure, the authors could estimate the surface density of adsorbed molecules and, thus, the number of binding sites potentially presented for the adhesion receptors. Surfaces coated with PLL-g-PEG-RGD presented less RGD sites, but was less efficient in promoting cell spreading than those coated with Fgn; hence, other binding sites in Fgn played a more decisive role in determining cell adherence. To support the cell adhesion data obtained with the biosensor, cell adherence on Fgn-coated surfaces 30-60 min after cell seeding was measured with three complementary techniques, i.e., with (1) a fluorescence-based classical adherence assay, (2) a shear flow chamber applying hydrodynamic shear stress to wash cells away, and (3) an automated micropipette using vacuum-generated fluid flow to lift cells up. These techniques confirmed the results

  3. In vitro adhesion of staphylococci to diamond-like carbon polymer hybrids under dynamic flow conditions.

    Science.gov (United States)

    Soininen, Antti; Levon, Jaakko; Katsikogianni, Maria; Myllymaa, Katja; Lappalainen, Reijo; Konttinen, Yrjö T; Kinnari, Teemu J; Tiainen, Veli-Matti; Missirlis, Yannis

    2011-03-01

    This study compares the ability of selected materials to inhibit adhesion of two bacterial strains commonly implicated in implant-related infections. These two strains are Staphylococcus aureus (S-15981) and Staphylococcus epidermidis (ATCC 35984). In experiments we tested six different materials, three conventional implant metals: titanium, tantalum and chromium, and three diamond-like carbon (DLC) coatings: DLC, DLC-polydimethylsiloxane hybrid (DLC-PDMS-h) and DLC-polytetrafluoroethylene hybrid (DLC-PTFE-h) coatings. DLC coating represents extremely hard material whereas DLC hybrids represent novel nanocomposite coatings. The two DLC polymer hybrid films were chosen for testing due to their hardness, corrosion resistance and extremely good non-stick (hydrophobic and oleophobic) properties. Bacterial adhesion assay tests were performed under dynamic flow conditions by using parallel plate flow chambers (PPFC). The results show that adhesion of S. aureus to DLC-PTFE-h and to tantalum was significantly (P coating showed as low susceptibility to S. aureus adhesion as all the tested conventional implant metals. The adherence of S. epidermidis to biomaterials was not significantly (P coating without increasing the risk of implant-related infections. PMID:21243516

  4. Influence of Copolyester Composition on Adhesion to Soda-Lime Glass via Molecular Dynamics Simulations.

    Science.gov (United States)

    Hanson, Ben; Hofmann, John; Pasquinelli, Melissa A

    2016-06-01

    Copolyesters are a subset of polymers that have the desirable properties of strength and clarity while retaining chemical resistance, and are thus potential candidates for enhancing the impact resistance of soda-lime glass. Adhesion between the polymer and the glass relates to the impact performance of the system, as well as the longevity of the bond between the polymer and the glass under various conditions. Modifying the types of diols and diacids present in the copolyester provides a method for fine-tuning the physical properties of the polymer. In this study, we used molecular dynamics (MD) simulations to examine the influence of the chemical composition of the polymers on adhesion of polymer film laminates to two soda-lime glass surfaces, one tin-rich and one oxygen-rich. By calculating properties such as adhesion energies and contact angles, these results provide insights into how the polymer-glass interaction is impacted by the polymer composition, temperature, and other factors such as the presence of free volume or pi stacking. These results can be used to optimize the adhesion of copolyester films to glass surfaces. PMID:27206103

  5. Neutrophil surface adhesion molecule and toll like receptor dynamics in crossbred cows suffering from Staphylococcus aureus subclinical and clinical mastitis

    Directory of Open Access Journals (Sweden)

    Dilip Kumar Swain

    2016-06-01

    Conclusion: Host elicits stage specific expression of surface adhesion molecules and TLR2 and TLR4 as dynamic host innate immune response against Staphylococcal mastitis. [J Adv Vet Anim Res 2016; 3(2.000: 99-105

  6. Alterations in ovarian cancer cell adhesion drive taxol resistance by increasing microtubule dynamics in a FAK-dependent manner.

    Science.gov (United States)

    McGrail, Daniel J; Khambhati, Niti N; Qi, Mark X; Patel, Krishan S; Ravikumar, Nithin; Brandenburg, Chandler P; Dawson, Michelle R

    2015-04-17

    Chemorefractory ovarian cancer patients show extremely poor prognosis. Microtubule-stabilizing Taxol (paclitaxel) is a first-line treatment against ovarian cancer. Despite the close interplay between microtubules and cell adhesion, it remains unknown if chemoresistance alters the way cells adhere to their extracellular environment, a process critical for cancer metastasis. To investigate this, we isolated Taxol-resistant populations of OVCAR3 and SKOV3 ovarian cancer cell lines. Though Taxol-resistant cells neither effluxed more drug nor gained resistance to other chemotherapeutics, they did display increased microtubule dynamics. These changes in microtubule dynamics coincided with faster attachment rates and decreased adhesion strength, which correlated with increased surface β1-integrin expression and decreased focal adhesion formation, respectively. Adhesion strength correlated best with Taxol-sensitivity, and was found to be independent of microtubule polymerization but dependent on focal adhesion kinase (FAK), which was up-regulated in Taxol-resistant cells. FAK inhibition also decreased microtubule dynamics to equal levels in both populations, indicating alterations in adhesive signaling are up-stream of microtubule dynamics. Taken together, this work demonstrates that Taxol-resistance dramatically alters how ovarian cancer cells adhere to their extracellular environment causing down-stream increases in microtubule dynamics, providing a therapeutic target that may improve prognosis by not only recovering drug sensitivity, but also decreasing metastasis.

  7. Angiogenin enhances cell migration by regulating stress fiber assembly and focal adhesion dynamics.

    Directory of Open Access Journals (Sweden)

    Saisai Wei

    Full Text Available Angiogenin (ANG acts on both vascular endothelial cells and cancer cells, but the underlying mechanism remains elusive. In this study, we carried out a co-immunoprecipitation assay in HeLa cells and identified 14 potential ANG-interacting proteins. Among these proteins, β-actin, α-actinin 4, and non-muscle myosin heavy chain 9 are stress fiber components and involved in cytoskeleton organization and movement, which prompted us to investigate the mechanism of action of ANG in cell migration. Upon confirmation of the interactions between ANG and the three proteins, further studies revealed that ANG co-localized with β-actin and α-actinin 4 at the leading edge of migrating cells. Down-regulation of ANG resulted in fewer but thicker stress fibers with less dynamics, which was associated with the enlargements of focal adhesions. The focal adhesion kinase activity and cell migration capacity were significantly decreased in ANG-deficient cells. Taken together, our data demonstrated that the existence of ANG in the cytoplasm optimizes stress fiber assembly and focal adhesion formation to accommodate cell migration. The finding that ANG promoted cancer cell migration might provide new clues for tumor metastasis research.

  8. Decipher the dynamic coordination between enzymatic activity and structural modulation at focal adhesions in living cells

    Science.gov (United States)

    Lu, Shaoying; Seong, Jihye; Wang, Yi; Chang, Shiou-Chi; Eichorst, John Paul; Ouyang, Mingxing; Li, Julie Y.-S.; Chien, Shu; Wang, Yingxiao

    2014-07-01

    Focal adhesions (FAs) are dynamic subcellular structures crucial for cell adhesion, migration and differentiation. It remains an enigma how enzymatic activities in these local complexes regulate their structural remodeling in live cells. Utilizing biosensors based on fluorescence resonance energy transfer (FRET), we developed a correlative FRET imaging microscopy (CFIM) approach to quantitatively analyze the subcellular coordination between the enzymatic Src activation and the structural FA disassembly. CFIM reveals that the Src kinase activity only within the microdomain of lipid rafts at the plasma membrane is coupled with FA dynamics. FA disassembly at cell periphery was linearly dependent on this raft-localized Src activity, although cells displayed heterogeneous levels of response to stimulation. Within lipid rafts, the time delay between Src activation and FA disassembly was 1.2 min in cells seeded on low fibronectin concentration ([FN]) and 4.3 min in cells on high [FN]. CFIM further showed that the level of Src-FA coupling, as well as the time delay, was regulated by cell-matrix interactions, as a tight enzyme-structure coupling occurred in FA populations mediated by integrin αvβ3, but not in those by integrin α5β1. Therefore, different FA subpopulations have distinctive regulation mechanisms between their local kinase activity and structural FA dynamics.

  9. Determining dynamical equations is hard

    CERN Document Server

    Cubitt, Toby S; Wolf, Michael M

    2010-01-01

    The behaviour of any physical system is governed by its underlying dynamical equations--the differential equations describing how the system evolves with time--and much of physics is ultimately concerned with discovering these dynamical equations and understanding their consequences. At the end of the day, any such dynamical law is identified by making measurements at different times, and computing the dynamical equation consistent with the acquired data. In this work, we show that, remarkably, this process is a provably computationally intractable problem (technically, it is NP-hard). That is, even for a moderately complex system, no matter how accurately we have specified the data, discovering its dynamical equations can take an infeasibly long time (unless P=NP). As such, we find a complexity-theoretic solution to both the quantum and the classical embedding problems; the classical version is a long-standing open problem, dating from 1937, which we finally lay to rest.

  10. Mapping the dynamics and nanoscale organization of synaptic adhesion proteins using monomeric streptavidin

    Science.gov (United States)

    Chamma, Ingrid; Letellier, Mathieu; Butler, Corey; Tessier, Béatrice; Lim, Kok-Hong; Gauthereau, Isabel; Choquet, Daniel; Sibarita, Jean-Baptiste; Park, Sheldon; Sainlos, Matthieu; Thoumine, Olivier

    2016-01-01

    The advent of super-resolution imaging (SRI) has created a need for optimized labelling strategies. We present a new method relying on fluorophore-conjugated monomeric streptavidin (mSA) to label membrane proteins carrying a short, enzymatically biotinylated tag, compatible with SRI techniques including uPAINT, STED and dSTORM. We demonstrate efficient and specific labelling of target proteins in confined intercellular and organotypic tissues, with reduced steric hindrance and no crosslinking compared with multivalent probes. We use mSA to decipher the dynamics and nanoscale organization of the synaptic adhesion molecules neurexin-1β, neuroligin-1 (Nlg1) and leucine-rich-repeat transmembrane protein 2 (LRRTM2) in a dual-colour configuration with GFP nanobody, and show that these proteins are diffusionally trapped at synapses where they form apposed trans-synaptic adhesive structures. Furthermore, Nlg1 is dynamic, disperse and sensitive to synaptic stimulation, whereas LRRTM2 is organized in compact and stable nanodomains. Thus, mSA is a versatile tool to image membrane proteins at high resolution in complex live environments, providing novel information about the nano-organization of biological structures. PMID:26979420

  11. Two new methods to determine the adhesion by means of internal friction in materials covered with films; Dos nuevos metodos para determinar la adhesion mediante friccion interna en materiales recubiertos con peliculas

    Energy Technology Data Exchange (ETDEWEB)

    Colorado, H. A.; Ghilarducci, A. A.; Salva, H. R.

    2006-07-01

    Two new models are proposed to determine the adhesion energy be means of the internal friction technique (IF) in thin films layered materials. for the first method is necessary to determine enthalpy by means of the IF technique, for which the adhesion work has been determined with experimental data. In the second method are necessary to perform IF tests at constant temperature. (Author)

  12. The Integrated Role of Wnt/β-Catenin, N-Glycosylation, and E-Cadherin-Mediated Adhesion in Network Dynamics.

    Science.gov (United States)

    Vargas, Diego A; Sun, Meng; Sadykov, Khikmet; Kukuruzinska, Maria A; Zaman, Muhammad H

    2016-07-01

    The cellular network composed of the evolutionarily conserved metabolic pathways of protein N-glycosylation, Wnt/β-catenin signaling pathway, and E-cadherin-mediated cell-cell adhesion plays pivotal roles in determining the balance between cell proliferation and intercellular adhesion during development and in maintaining homeostasis in differentiated tissues. These pathways share a highly conserved regulatory molecule, β-catenin, which functions as both a structural component of E-cadherin junctions and as a co-transcriptional activator of the Wnt/β-catenin signaling pathway, whose target is the N-glycosylation-regulating gene, DPAGT1. Whereas these pathways have been studied independently, little is known about the dynamics of their interaction. Here we present the first numerical model of this network in MDCK cells. Since the network comprises a large number of molecules with varying cell context and time-dependent levels of expression, it can give rise to a wide range of plausible cellular states that are difficult to track. Using known kinetic parameters for individual reactions in the component pathways, we have developed a theoretical framework and gained new insights into cellular regulation of the network. Specifically, we developed a mathematical model to quantify the fold-change in concentration of any molecule included in the mathematical representation of the network in response to a simulated activation of the Wnt/ β-catenin pathway with Wnt3a under different conditions. We quantified the importance of protein N-glycosylation and synthesis of the DPAGT1 encoded enzyme, GPT, in determining the abundance of cytoplasmic β-catenin. We confirmed the role of axin in β-catenin degradation. Finally, our data suggest that cell-cell adhesion is insensitive to E-cadherin recycling in the cell. We validate the model by inhibiting β-catenin-mediated activation of DPAGT1 expression and predicting changes in cytoplasmic β-catenin concentration and stability

  13. A role for the juxtamembrane cytoplasm in the molecular dynamics of focal adhesions.

    Directory of Open Access Journals (Sweden)

    Haguy Wolfenson

    Full Text Available Focal adhesions (FAs are specialized membrane-associated multi-protein complexes that link the cell to the extracellular matrix and play crucial roles in cell-matrix sensing. Considerable information is available on the complex molecular composition of these sites, yet the regulation of FA dynamics is largely unknown. Based on a combination of FRAP studies in live cells, with in silico simulations and mathematical modeling, we show that the FA plaque proteins paxillin and vinculin exist in four dynamic states: an immobile FA-bound fraction, an FA-associated fraction undergoing exchange, a juxtamembrane fraction experiencing attenuated diffusion, and a fast-diffusing cytoplasmic pool. The juxtamembrane region surrounding FAs displays a gradient of FA plaque proteins with respect to both concentration and dynamics. Based on these findings, we propose a new model for the regulation of FA dynamics in which this juxtamembrane domain acts as an intermediary layer, enabling an efficient regulation of FA formation and reorganization.

  14. Determination of carbon fiber adhesion to thermoplastic polymers using the single fiber/matrix tensile test

    Science.gov (United States)

    Bascom, W. D.; Cordner, L. W.; Hinkley, J. L.; Johnston, N. J.

    1986-01-01

    The single fiber adhesion shear test has been adapted to testing the adhesion between carbon fiber and thermoplastic polymers. Tests of three thermoplastics, polycarbonate, polyphenylene oxide and polyetherimide indicate the shear adhesion strength is significantly less than of an epoxy polymer to the same carbon fiber.

  15. Circulating cytokines, chemokines and adhesion molecules in normal pregnancy and preeclampsia determined by multiplex suspension array

    Directory of Open Access Journals (Sweden)

    Bekő Gabriella

    2010-12-01

    Full Text Available Abstract Background Preeclampsia is a severe complication of pregnancy characterized by an excessive maternal systemic inflammatory response with activation of both the innate and adaptive arms of the immune system. Cytokines, chemokines and adhesion molecules are central to innate and adaptive immune processes. The purpose of this study was to determine circulating levels of cytokines, chemokines and adhesion molecules in normal pregnancy and preeclampsia in a comprehensive manner, and to investigate their relationship to the clinical features and laboratory parameters of the study participants, including markers of overall inflammation (C-reactive protein, endothelial activation (von Willebrand factor antigen and endothelial injury (fibronectin, oxidative stress (malondialdehyde and trophoblast debris (cell-free fetal DNA. Results Serum levels of interleukin (IL-1beta, IL-1 receptor antagonist (IL-1ra, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12p40, IL-12p70, IL-18, interferon (IFN-gamma, tumor necrosis factor (TNF-alpha, transforming growth factor (TGF-beta1, interferon-gamma-inducible protein (IP-10, monocyte chemotactic protein (MCP-1, intercellular adhesion molecule (ICAM-1 and vascular cell adhesion molecule (VCAM-1 were measured in 60 preeclamptic patients, 60 healthy pregnant women and 59 healthy non-pregnant women by multiplex suspension array and ELISA. In normal pregnancy, the relative abundance of circulating IL-18 over IL-12p70 and the relative deficiency of the bioactive IL-12p70 in relation to IL-12p40 might favour Th2-type immunity. Although decreased IL-1ra, TNF-alpha and MCP-1 concentrations of healthy pregnant relative to non-pregnant women reflect anti-inflammatory changes in circulating cytokine profile, their decreased serum IL-10 and increased IP-10 levels might drive pro-inflammatory responses. In addition to a shift towards Th1-type immunity (expressed by the increased IL-2/IL-4 and IFN-gamma/IL-4 ratios, circulating levels of

  16. Interactions between MUC1 and p120 catenin regulate dynamic features of cell adhesion, motility and metastasis

    Science.gov (United States)

    Liu, Xiang; Yi, Chunhui; Wen, Yunfei; Radhakrishnan, Prakash; Tremayne, Jarrod R.; Dao, Thongtan; Johnson, Keith R.; Hollingsworth, Michael A.

    2014-01-01

    The mechanisms by which MUC1 and p120 catenin contribute to progression of cancers from early transformation to metastasis are poorly understood. Here we show that p120 catenin ARM domains 1, 3–5 and 8 mediate interactions between p120 catenin and MUC1, and that these interactions modulate dynamic properties of cell adhesion, motility and metastasis of pancreatic cancer cells. We also show that different isoforms of p120 catenin when co-expressed with MUC1 create cells that exhibit distinct patterns of motility in culture (motility independent of cell adhesion, motility within a monolayer while exchanging contacts with other cells, and unified motility while maintaining static epithelial contacts) and patterns of metastasis. The results provide new insight into the dynamic interplay between cell adhesion and motility and the relationship of these to the metastatic process. PMID:24371222

  17. Adhesion in hydrogel contacts

    Science.gov (United States)

    Torres, J. R.; Jay, G. D.; Kim, K.-S.; Bothun, G. D.

    2016-05-01

    A generalized thermomechanical model for adhesion was developed to elucidate the mechanisms of dissipation within the viscoelastic bulk of a hyperelastic hydrogel. Results show that in addition to the expected energy release rate of interface formation, as well as the viscous flow dissipation, the bulk composition exhibits dissipation due to phase inhomogeneity morphological changes. The mixing thermodynamics of the matrix and solvent determines the dynamics of the phase inhomogeneities, which can enhance or disrupt adhesion. The model also accounts for the time-dependent behaviour. A parameter is proposed to discern the dominant dissipation mechanism in hydrogel contact detachment.

  18. Simultaneous determination of protein structure and dynamics

    DEFF Research Database (Denmark)

    Lindorff-Larsen, Kresten; Best, Robert B.; DePristo, M. A.;

    2005-01-01

    We present a protocol for the experimental determination of ensembles of protein conformations that represent simultaneously the native structure and its associated dynamics. The procedure combines the strengths of nuclear magnetic resonance spectroscopy-for obtaining experimental information at...

  19. Influence of nitric laser (ultraviolet) on dynamics of adhesion formation in peritoneum

    International Nuclear Information System (INIS)

    The investigation of adhesion formation in peritoneums after ultraviolet laser irradiation was carried out by morphological methods. It was revealed that ultraviolet laser irradiation prevents the adhesion formation, because this laser decreases the rate of the proliferation of mesotheliomas. This phenomenon may be used for the prophylaxis of adhesions formation. (author)

  20. Pulse voltage determination for electrostatic micro manipulation considering surface conductivity and adhesion of glass particle

    Directory of Open Access Journals (Sweden)

    Ryo Fujiwara

    2015-05-01

    Full Text Available A model with surface conductivity and adhesional force is proposed to investigate the mechanism for electrostatic micro manipulation of a dielectric object using a single probe. 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. The reliability of the picking up/placing operation is improved by applying a pulse voltage that is determined by a theoretical model considering surface conductivity and adhesion. To verify the theoretical prediction, manipulation experiment is conducted using soda-lime glass particles with radii of 20 μm and 40 μm.

  1. Determining the Resistance to Delamination of Wood Adhesives using a Vacuum Pressure Impregnation Method

    OpenAIRE

    Mills, Christopher

    2013-01-01

    The thesis was completed for the Research and Development (R&D) laboratory at Kiilto Oy. The purpose of the thesis was to study the delamination of glued solid timber and glulam, glued with moisture cured one component polyurethane adhesives (1K PUR) and an emulsion polymer isocyanate adhesive (EPI) using the new easyQ DLA appliance. Delamination is the failure of the adhesive layer between wood lamellae, used to produce glued solid timber and glued laminated timber (glulam). Delamination ...

  2. Characterization of cohesion, adhesion and creep-properties of dynamically loaded coatings through the impact tester

    Energy Technology Data Exchange (ETDEWEB)

    Bouzakis, K.D.; Michailidis, N.; Lontos, A.; Siganos, A.; Hadjiyiannis, S.; Giannopoulos, G.; Maliaris, G. [Aristoteles Univ., Thessaloniki (Greece). Lab. for Machine Tools and Mfg. Engineering; Erkens, G. [CemeCon GmbH, Wuerselen (Germany)

    2001-10-01

    The coating impact test, in combination with finite elements method (FEM) simulation, is successfully used to characterize the fatigue performance of coatings. Critical values for stress components, responsible for distinctive fatigue failure modes of the coating, are obtained and the fatigue limits of various coatings are illustrated in form of generally applicable Smith and Woehler diagrams, determined through a developed evaluation software. This software takes into account the impact test experimental data, as well as coating and substrate constitutive laws. Herewith coating adhesive and cohesive failure modes are elucidated and a cutting performance prediction of coated tools can be carried out. On the other hand, creep phenomena of plasma sprayed coatings are quantitatively interpreted. (orig.)

  3. Dynamics of spider glue adhesion: effect of surface energy and contact area

    Science.gov (United States)

    Amarpuri, Gaurav; Chen, Yizhou; Blackledge, Todd; Dhinojwala, Ali

    Spider glue is a unique biological adhesive which is humidity responsive such that the adhesion continues to increase upto 100% relative humidity (RH) for some species. This is unlike synthetic adhesives that significantly drop in adhesion with an increase in humidity. However, most of adhesion data reported in literature have used clean hydrophilic glass substrate, unlike the hydrophobic, and charged insect cuticle surface that adheres to spider glue in nature. Previously, we have reported that the spider glue viscosity changes over five orders of magnitude with humidity. Here, we vary the surface energy and surface charge of the substrate to test the change in Larnioides cornutus spider glue adhesion with humidity. We find that an increase in both surface energy and surface charge density increases the droplet spreading and there exists an optimum droplet contact area where adhesion is maximized. Moreover, spider glue droplets act as reusable adhesive for low energy hydrophobic surface at the optimum humidity. These results explain why certain prey are caught more efficiently by spiders in their habitat. The mechanism by which spider species tune its glue adhesion for local prey capture can inspire new generation smart adhesives.

  4. An Ultrasonic Technique to Determine the Residual Strength of Adhesive Bonds

    Science.gov (United States)

    Achenbach, J. D.; Tang, Z.

    1999-01-01

    In this work, ultrasonic techniques to nondestructively evaluate adhesive bond degradation have been studied. The key to the present approach is the introduction of an external factor which pulls the adhesive bond in the nonlinear range, simultaneously with the application of an ultrasonic technique. With the aid of an external static tensile loading, a superimposed longitudinal wave has.been used to obtain the slopes of the stress-strain curve of an adhesive bond at a series of load levels. The critical load, at which a reduction of the slope is detected by the superimposed longitudinal wave, is an indication of the onset of nonlinear behavior of the adhesive bond, and therefore of bond degradation. This approach has been applied to the detection of adhesive bond degradation induced by cyclic fatigue loading. Analogously to the longitudinal wave case, a superimposed shear wave has been used to obtain the effective shear modulus of adhesive layers at different shear load levels. The onset of the nonlinear behavior of an adhesive bond under shear loading has been detected by the use of a superimposed shear wave. Experiments show that a longitudinal wave can also detect the nonlinear behavior when an adhesive bond is subjected to shear loading. An optimal combination of ultrasonic testing and mechanical loading methods for the detection of degradation related nonlinear behavior of adhesive bonds has been discussed. For the purpose of a practical application, an ultrasonic technique that uses a temperature increase as an alternative to static loading has also been investigated. A general strain-temperature correspondence principle that relates a mechanical strain to a temperature has been presented. Explicit strain-temperature correspondence relations for both the tension and shear cases have been derived. An important parameter which quantifies the relation between the wave velocity and temperature has been defined. This parameter, which is indicative of adhesive

  5. Universal relationships to determine adhesion energy from vesicle-substrate interactions

    CERN Document Server

    Irajizad, Ehsan

    2016-01-01

    Adhesion molecules play an integral role in diverse biological functions ranging from cellular growth to transport. Estimation of their binding affinity, therefore, becomes important to quantify their biophysical impact on these phenomena. In this paper, we use curvature elasticity to present non-intuitive, yet remarkably simple, universal relationships to tease out adhesion energy from vesicle-substrate experiments. Our study reveals that the inverse of the height, exponential of the contact area, and the force required to detach the vesicle from the substrate vary linearly with the square root of the adhesion energy. We validate the modeling predictions with experimental data from two previous studies.

  6. Using engineered single-chain antibodies to correlate molecular binding properties and nanoparticle adhesion dynamics.

    Science.gov (United States)

    Haun, Jered B; Pepper, Lauren R; Boder, Eric T; Hammer, Daniel A

    2011-11-15

    Elucidation of the relationship between targeting molecule binding properties and the adhesive behavior of therapeutic or diagnostic nanocarriers would aid in the design of optimized vectors and lead to improved efficacy. We measured the adhesion of 200-nm-diameter particles under fluid flow that was mediated by a diverse array of molecular interactions, including recombinant single-chain antibodies (scFvs), full antibodies, and the avidin/biotin interaction. Within the panel of scFvs, we used a family of mutants that display a spectrum of binding kinetics, allowing us to compare nanoparticle adhesion to bond chemistry. In addition, we explored the effect of molecular size by inserting a protein linker into the scFv fusion construct and by employing scFvs that are specific for targets with vastly different sizes. Using computational models, we extracted multivalent kinetic rate constants for particle attachment and detachment from the adhesion data and correlated the results to molecular binding properties. Our results indicate that the factors that increase encounter probability, such as adhesion molecule valency and size, directly enhance the rate of nanoparticle attachment. Bond kinetics had no influence on scFv-mediated nanoparticle attachment within the kinetic range tested, however, but did appear to affect antibody/antigen and avidin/biotin mediated adhesion. We attribute this finding to a combination of multivalent binding and differences in bond mechanical strength between recombinant scFvs and the other adhesion molecules. Nanoparticle detachment probability correlated directly with adhesion molecule valency and size, as well as the logarithm of the affinity for all molecules tested. On the basis of this work, scFvs can serve as viable targeting receptors for nanoparticles, but improvements to their bond mechanical strength would likely be required to fully exploit their tunable kinetic properties and maximize the adhesion efficiency of nanoparticles that

  7. A short-time scale colloidal system reveals early bacterial adhesion dynamics.

    Directory of Open Access Journals (Sweden)

    Christophe Beloin

    2008-07-01

    Full Text Available The development of bacteria on abiotic surfaces has important public health and sanitary consequences. However, despite several decades of study of bacterial adhesion to inert surfaces, the biophysical mechanisms governing this process remain poorly understood, due, in particular, to the lack of methodologies covering the appropriate time scale. Using micrometric colloidal surface particles and flow cytometry analysis, we developed a rapid multiparametric approach to studying early events in adhesion of the bacterium Escherichia coli. This approach simultaneously describes the kinetics and amplitude of early steps in adhesion, changes in physicochemical surface properties within the first few seconds of adhesion, and the self-association state of attached and free-floating cells. Examination of the role of three well-characterized E. coli surface adhesion factors upon attachment to colloidal surfaces--curli fimbriae, F-conjugative pilus, and Ag43 adhesin--showed clear-cut differences in the very initial phases of surface colonization for cell-bearing surface structures, all known to promote biofilm development. Our multiparametric analysis revealed a correlation in the adhesion phase with cell-to-cell aggregation properties and demonstrated that this phenomenon amplified surface colonization once initial cell-surface attachment was achieved. Monitoring of real-time physico-chemical particle surface properties showed that surface-active molecules of bacterial origin quickly modified surface properties, providing new insight into the intricate relations connecting abiotic surface physicochemical properties and bacterial adhesion. Hence, the biophysical analytical method described here provides a new and relevant approach to quantitatively and kinetically investigating bacterial adhesion and biofilm development.

  8. Crowdfunding : Determinants of success and funding dynamics

    OpenAIRE

    CROSETTO, Paolo; Regner, Tobias

    2014-01-01

    Over the past years crowdfunding emerged as an alternative funding channel for entrepreneurs. In contrast to traditional financiers (banks, venture capital firms or angel investors), crowdfunding allows individuals to fund entrepreneurs directly even with small amounts. We received individual- level data from Startnext, the biggest crowdfunding platform in Germany, enabling us to investigate funding dynamics, explore pledgers' motivations and analyze projects' success determinants. We find su...

  9. Weak scale: Dynamical determination versus accidental stabilization

    OpenAIRE

    Triantaphyllou, George

    2001-01-01

    Is it a mere accident that the weak scale is exactly so much smaller than the Planck scale, and at the same time exactly so much larger than the QCD scale? Or are the experimentally-measured values of the corresponding gauge couplings enough to help us determine dynamically these energy scales? And if nature has indeed offered us the possibility of such a determination, why dismiss it and fix these scales instead by means of arbitrary parameters within a multitude of jejune theoretical framew...

  10. Determination of interfacial adhesion strength between oxide scale and substrate for metallic SOFC interconnects

    Science.gov (United States)

    Sun, X.; Liu, W. N.; Stephens, E.; Khaleel, M. A.

    The interfacial adhesion strength between the oxide scale and the substrate is crucial to the reliability and durability of metallic interconnects in solid oxide fuel cell (SOFC) operating environments. It is necessary, therefore, to establish a methodology to quantify the interfacial adhesion strength between the oxide scale and the metallic interconnect substrate, and furthermore to design and optimize the interconnect material as well as the coating materials to meet the design life of an SOFC system. In this paper, we present an integrated experimental/analytical methodology for quantifying the interfacial adhesion strength between the oxide scale and a ferritic stainless steel interconnect. Stair-stepping indentation tests are used in conjunction with subsequent finite element analyses to predict the interfacial strength between the oxide scale and Crofer 22 APU substrate.

  11. Receptor-mediated membrane adhesion of lipid-polymer hybrid (LPH) nanoparticles studied by dissipative particle dynamics simulations

    Science.gov (United States)

    Li, Zhenlong; Gorfe, Alemayehu A.

    2014-12-01

    Lipid-polymer hybrid (LPH) nanoparticles represent a novel class of targeted drug delivery platforms that combine the advantages of liposomes and biodegradable polymeric nanoparticles. However, the molecular details of the interaction between LPHs and their target cell membranes remain poorly understood. We have investigated the receptor-mediated membrane adhesion process of a ligand-tethered LPH nanoparticle using extensive dissipative particle dynamics (DPD) simulations. We found that the spontaneous adhesion process follows a first-order kinetics characterized by two distinct stages: a rapid nanoparticle-membrane engagement, followed by a slow growth in the number of ligand-receptor pairs coupled with structural re-organization of both the nanoparticle and the membrane. The number of ligand-receptor pairs increases with the dynamic segregation of ligands and receptors toward the adhesion zone causing an out-of-plane deformation of the membrane. Moreover, the fluidity of the lipid shell allows for strong nanoparticle-membrane interactions to occur even when the ligand density is low. The LPH-membrane avidity is enhanced by the increased stability of each receptor-ligand pair due to the geometric confinement and the cooperative effect arising from multiple binding events. Thus, our results reveal the unique advantages of LPH nanoparticles as active cell-targeting nanocarriers and provide some general principles governing nanoparticle-cell interactions that may aid future design of LPHs with improved affinity and specificity for a given target of interest.

  12. Modeling keratinocyte wound healing dynamics: Cell-cell adhesion promotes sustained collective migration.

    Science.gov (United States)

    Nardini, John T; Chapnick, Douglas A; Liu, Xuedong; Bortz, David M

    2016-07-01

    The in vitro migration of keratinocyte cell sheets displays behavioral and biochemical similarities to the in vivo wound healing response of keratinocytes in animal model systems. In both cases, ligand-dependent Epidermal Growth Factor Receptor (EGFR) activation is sufficient to elicit collective cell migration into the wound. Previous mathematical modeling studies of in vitro wound healing assays assume that physical connections between cells have a hindering effect on cell migration, but biological literature suggests a more complicated story. By combining mathematical modeling and experimental observations of collectively migrating sheets of keratinocytes, we investigate the role of cell-cell adhesion during in vitro keratinocyte wound healing assays. We develop and compare two nonlinear diffusion models of the wound healing process in which cell-cell adhesion either hinders or promotes migration. Both models can accurately fit the leading edge propagation of cell sheets during wound healing when using a time-dependent rate of cell-cell adhesion strength. The model that assumes a positive role of cell-cell adhesion on migration, however, is robust to changes in the leading edge definition and yields a qualitatively accurate density profile. Using RNAi for the critical adherens junction protein, α-catenin, we demonstrate that cell sheets with wild type cell-cell adhesion expression maintain migration into the wound longer than cell sheets with decreased cell-cell adhesion expression, which fails to exhibit collective migration. Our modeling and experimental data thus suggest that cell-cell adhesion promotes sustained migration as cells pull neighboring cells into the wound during wound healing. PMID:27105673

  13. Modeling keratinocyte wound healing dynamics: Cell-cell adhesion promotes sustained collective migration.

    Science.gov (United States)

    Nardini, John T; Chapnick, Douglas A; Liu, Xuedong; Bortz, David M

    2016-07-01

    The in vitro migration of keratinocyte cell sheets displays behavioral and biochemical similarities to the in vivo wound healing response of keratinocytes in animal model systems. In both cases, ligand-dependent Epidermal Growth Factor Receptor (EGFR) activation is sufficient to elicit collective cell migration into the wound. Previous mathematical modeling studies of in vitro wound healing assays assume that physical connections between cells have a hindering effect on cell migration, but biological literature suggests a more complicated story. By combining mathematical modeling and experimental observations of collectively migrating sheets of keratinocytes, we investigate the role of cell-cell adhesion during in vitro keratinocyte wound healing assays. We develop and compare two nonlinear diffusion models of the wound healing process in which cell-cell adhesion either hinders or promotes migration. Both models can accurately fit the leading edge propagation of cell sheets during wound healing when using a time-dependent rate of cell-cell adhesion strength. The model that assumes a positive role of cell-cell adhesion on migration, however, is robust to changes in the leading edge definition and yields a qualitatively accurate density profile. Using RNAi for the critical adherens junction protein, α-catenin, we demonstrate that cell sheets with wild type cell-cell adhesion expression maintain migration into the wound longer than cell sheets with decreased cell-cell adhesion expression, which fails to exhibit collective migration. Our modeling and experimental data thus suggest that cell-cell adhesion promotes sustained migration as cells pull neighboring cells into the wound during wound healing.

  14. Dot assay for determining adhesive interactions between yeasts and bacteria under controlled hydrodynamic conditions

    NARCIS (Netherlands)

    Millsap, KW; Van der Mei, HC; Busscher, HJ; Bos, R.R.M.

    2000-01-01

    Candida belongs to the normal human microflora and are found adhering to a number of human body tissues as well as to a variety of biomaterials implants. Often, yeasts adhere in association with bacteria, but to date there is no definitive assay to investigate adhesive interactions between yeasts an

  15. Dynamic bio-adhesion of polymer nanoparticles on MDCK epithelial cells and its impact on bio-membranes, endocytosis and paracytosis

    Science.gov (United States)

    He, Bing; Yuan, Lan; Dai, Wenbing; Gao, Wei; Zhang, Hua; Wang, Xueqing; Fang, Weigang; Zhang, Qiang

    2016-03-01

    Nowadays, concern about the use of nanotechnology for biomedical application is unprecedentedly increasing. In fact, nanosystems applied for various potential clinical uses always have to cross the primary biological barrier consisting of epithelial cells. However, little is really known currently in terms of the influence of the dynamic bio-adhesion of nanosystems on bio-membranes as well as on endocytosis and transcytosis. This was investigated here using polymer nanoparticles (PNs) and MDCK epithelial cells as the models. Firstly, the adhesion of PNs on cell membranes was found to be time-dependent with a shift of both location and dispersion pattern, from the lateral adhesion of mainly mono-dispersed PNs initially to the apical coverage of the PN aggregate later. Then, it was interesting to observe in this study that the dynamic bio-adhesion of PNs only affected their endocytosis but not their transcytosis. It was important to find that the endocytosis of PNs was not a constant process. A GM1 dependent CDE (caveolae dependent endocytosis) pathway was dominant in the preliminary stage, followed by the co-existence of a CME (clathrin-mediated endocytosis) pathway for the PN aggregate at a later stage, in accordance with the adhesion features of PNs, suggesting the modification of PN adhesion patterns on the endocytosis pathways. Next, the PN adhesion was noticed to affect the structure of cell junctions, via altering the extra- and intra-cellular calcium levels, leading to the enhanced paracellular transport of small molecules, but not favorably enough for the obviously increased passing of PNs themselves. Finally, FRAP and other techniques all demonstrated the obvious impact of PN adhesion on the membrane confirmation, independent of the adhesion location and time, which might lower the threshold for the internalization of PNs, even their aggregates. Generally, these findings confirm that the transport pathway mechanism of PNs through epithelial cells is rather

  16. [Adhesive cutaneous pharmaceutical forms].

    Science.gov (United States)

    Gafiţanu, E; Matei, I; Mungiu, O C; Pavelescu, M; Mîndreci, I; Apostol, I; Ionescu, G

    1989-01-01

    The adhesive cutaneous pharmaceutical forms aimed to local action release the drug substance in view of a dermatological, traumatological, antirheumatic, cosmetic action. Two such preparations were obtained and their stability, consistency and pH were determined. The "in vitro" tests of their bioavailability revealed the dynamics of calcium ions release according to the associations of each preparation. The bioavailability determined by evaluating the pharmacological response demonstrated the antiinflammatory action obtained by the association of calcium ions with the components extracted from poplar muds. The therapeutical efficiency of the studied preparations has proved in the treatment of some sport injuries.

  17. Determinants of Welfare Dynamics in Rural Nicaragua

    DEFF Research Database (Denmark)

    Jakobsen, Kristian Thor

    2011-01-01

    This article explores the determinants of poverty movements in rural Nicaragua by introducing a bivariate probate model, making it possible to treat the initial state of poverty as endogenous and thus avoiding introducing selection bias. The results indicate that this is relevant when exploring...... welfare dynamics in rural Nicaragua, as initially poor households face a higher probability of being poor in the subsequent period compared with non-poor households. It is also found that household composition, access to non-agriculture wage income and ownership of productive assets are important factors...

  18. The scratch test - Different critical load determination techniques. [adhesive strength of thin hard coatings

    Science.gov (United States)

    Sekler, J.; Hintermann, H. E.; Steinmann, P. A.

    1988-01-01

    Different critical load determination techniques such as microscopy, acoustic emission, normal, tangential, and lateral forces used for scratch test evaluation of complex or multilayer coatings are investigated. The applicability of the scratch test to newly developed coating techniques, systems, and applications is discussed. Among the methods based on the use of a physical measurement, acoustic emission detection is the most effective. The dynamics ratio between the signals below and above the critical load for the acoustic emission (much greater than 100) is well above that obtained with the normal, tangential, and lateral forces. The present commercial instruments are limited in load application performance. A scratch tester able to apply accurate loads as low as 0.01 N would probably overcome most of the actual limitations and would be expected to extend the scratch testing technique to different application fields such as optics and microelectronics.

  19. 40 CFR Appendix A to Subpart Pppp... - Determination of Weight Volatile Matter Content and Weight Solids Content of Reactive Adhesives

    Science.gov (United States)

    2010-07-01

    ... Content and Weight Solids Content of Reactive Adhesives A Appendix A to Subpart PPPP of Part 63 Protection... Reactive Adhesives 1.0Applicability and Principle 1.1Applicability: This method applies to the... reactive adhesives. Reactive adhesives are composed, in large part, of monomers that react during...

  20. Determining gastric cancer resectability by dynamic MDCT

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Zilai; Zhang, Huan; Du, Lianjun; Ding, Bei; Song, Qi; Ling, Huawei; Huang, Baisong; Chen, Kemin [Jiaotong University, Department of Radiology, Shanghai (China); Yan, Chao [Jiaotong University, Department of Surgery, Shanghai (China)

    2010-03-15

    Multi-detector row CT (MDCT) has been widely used to detect primary lesions and to evaluate TNM staging. In this study we evaluated the accuracy of dynamic MDCT in the preoperative determination of the resectability of gastric cancer. MDCT was used to image 350 cases of gastric cancer diagnosed by biopsy before surgery. MDCT findings regarding TNM staging and resectability were correlated with surgical and pathological findings. The accuracy of MDCT for staging gastric cancer was high, especially for tumour stage T1 (94.3%), lymph node stage N2 (87.3%), and for predicting distant metastases (>96.6%). When resectability was considered to be the outcome, the total accuracy of MDCT was 87.4%, sensitivity was 89.7% and specificity was 76.7%. Results showed high sensitivity for identifying peritoneal seeding (90.0%) and for predicting liver metastasis (80.0%). Dynamic enhanced MDCT is useful for TNM staging of gastric cancers and for predicting tumour respectability preoperatively. (orig.)

  1. Dynamic characteristics determination using noise analysis

    International Nuclear Information System (INIS)

    Using noise analysis techniques dynamical reference properties of selected variables were investigated for 250 kW TRIGA Mark II reactor during normal operation. Reference power spectra of neutron noise of the percent power channel were computed in the frequency band from 0,01 Hz to 100 Hz and operational power dependence was determined. Detailed analyses of neutron noise at very low frequencies between 0,0004 Hz and 0,2 Hz led to the conclusion that using noise analyses characteristical time constants of TRIGA reactor operating at powers from 10 kW to 250 kW can be extracted. For interpreting the experimental results a new stochastical model was developed on the basis of a nonlinear model of the TRIGA reactor. The model enabled simulation of operation at powers from 10 kW to 250 kW during small reactivity insertions. (author)

  2. A method to determine Young's modulus of soft gels for cell adhesion

    Institute of Scientific and Technical Information of China (English)

    Xiaoling Peng; Jianyong Huang; Lei Qin; Chunyang Xiong; Jing Fang

    2009-01-01

    A convenient technique is reported in this note for measuring elastic modulus of extremely soft material for cellular adhesion. Specimens of bending cylinder under gravity are used to avoid contact problem between testing device and sample, and a beam model is presented for evaluating the curvatures of gel beams with large elastic deformation. A self-adaptive algorithm is also proposed to search for the best estimation of gels' elastic moduli by comparing the experimental bending curvatures with those computed from the beam model with preestimated moduli. Application to the measurement of the property of polyacrylamide gels indicates that the material compliance varies with the concentrations of bis-acrylamide, and the gels become softer after being immersed in a culture medium for a period of time, no matter to what extent they are polymerized.

  3. Ovarian Cancer Cell Adhesion/Migration Dynamics on Micro-Structured Laminin Gradients Fabricated by Multiphoton Excited Photochemistry

    Directory of Open Access Journals (Sweden)

    Ruei-Yu He

    2015-07-01

    Full Text Available Haptotaxis, i.e., cell migration in response to adhesive gradients, has been previously implicated in cancer metastasis. A better understanding of cell migration dynamics and their regulation could ultimately lead to new drug targets, especially for cancers with poor prognoses, such as ovarian cancer. Haptotaxis has not been well-studied due to the lack of biomimetic, biocompatible models, where, for example, microcontact printing and microfluidics approaches are primarily limited to 2D surfaces and cannot produce the 3D submicron features to which cells respond. Here we used multiphoton excited (MPE phototochemistry to fabricate nano/microstructured gradients of laminin (LN as 2.5D models of the ovarian basal lamina to study the haptotaxis dynamics of a series of ovarian cancer cells. Using these models, we found that increased LN concentration increased migration speed and also alignment of the overall cell morphology and their cytoskeleton along the linear axis of the gradients. Both these metrics were enhanced on LN compared to BSA gradients of the same design, demonstrating the importance of both topographic and ECM cues on the adhesion/migration dynamics. Using two different gradient designs, we addressed the question of the roles of local concentration and slope and found that the specific haptotactic response depends on the cell phenotype and not simply the gradient design. Moreover, small changes in concentration strongly affected the migration properties. This work is a necessary step in studying haptotaxis in more complete 3D models of the tumor microenvironment for ovarian and other cancers.

  4. Abdominal Adhesions

    Science.gov (United States)

    ... adhesions? Abdominal adhesions can cause intestinal obstruction and female infertility—the inability to become pregnant after a year of trying. Abdominal adhesions can lead to female infertility by preventing fertilized eggs from reaching the uterus, ...

  5. Dynamic and Static Interactions between p120 Catenin and E-Cadherin Regulate the Stability of Cell-Cell Adhesion

    Energy Technology Data Exchange (ETDEWEB)

    Ishiyama, Noboru; Lee, Seung-Hye; Liu, Shuang; Li, Guang-Yao; Smith, Matthew J.; Reichardt, Louis F.; Ikura, Mitsuhiko (OCI); (UCSF)

    2010-04-26

    The association of p120 catenin (p120) with the juxtamembrane domain (JMD) of the cadherin cytoplasmic tail is critical for the surface stability of cadherin-catenin cell-cell adhesion complexes. Here, we present the crystal structure of p120 isoform 4A in complex with the JMD core region (JMD{sub core}) of E-cadherin. The p120 armadillo repeat domain contains modular binding pockets that are complementary to electrostatic and hydrophobic properties of the JMD{sub core}. Single-residue mutations within the JMD{sub core}-binding site of p120 abolished its interaction with E- and N-cadherins in vitro and in cultured cells. These mutations of p120 enabled us to clearly differentiate between N-cadherin-dependent and -independent steps of neuronal dendritic spine morphogenesis crucial for synapse development. NMR studies revealed that p120 regulates the stability of cadherin-mediated cell-cell adhesion by associating with the majority of the JMD, including residues implicated in clathrin-mediated endocytosis and Hakai-dependent ubiquitination of E-cadherin, through its discrete dynamic and static binding sites.

  6. Method of determining dynamic retention of mesh phase separator

    OpenAIRE

    Давыдов, Сергей Александрович

    2010-01-01

    In given work the engineering design procedure of dynamic retention of mesh phase’s delimiters is presented. This allows to determine functionability of means fuel continuity support in dynamic conditions at a stage of outline designing.

  7. Measurement of particle trajectories, dynamics, surface adhesion and detachment in near-wall shear flows using 3D velocimetry

    Science.gov (United States)

    Guasto, Jeffrey; Schmidt, Brian; Lawrence, Michael; Breuer, Kenneth

    2007-11-01

    Three-dimensional total internal reflection velocimetry (3D-TIRV) is used to measure the trajectories of fluorescent tracer particles within 200 nm of a wall. Diffusion and shear-induced motion can result in mean velocity measurement errors, and by taking measurements using different particle sizes and sampling times, we quantify these effects and compare with theory. We also use 3D-TIRV to observe and characterize the adhesion, surface rolling and release dynamics of particles that can adhere to the surface through the action of biological binding proteins. Particles coated with P-Selectin are allowed to adhere to and detach from a PSGL-1-coated microchannel surface, modeling the interaction between leukocytes (white blood cells) and blood vessels, respectively. Binding affinities, bond strengths and hydrodynamic interactions are inferred from the trajectory data.

  8. Cell adhesion and cortex contractility determine cell patterning in the Drosophila retina.

    Science.gov (United States)

    Käfer, Jos; Hayashi, Takashi; Marée, Athanasius F M; Carthew, Richard W; Graner, François

    2007-11-20

    Because of the resemblance of many epithelial tissues to densely packed soap bubbles, it has been suggested that surface minimization, which drives soap bubble packing, could be governing cell packing as well. We test this by modeling the shape of the cells in a Drosophila retina ommatidium. We use the observed configurations and shapes in wild-type flies, as well as in flies with different numbers of cells per ommatidia, and mutants with cells where E- or N-cadherin is either deleted or misexpressed. We find that surface minimization is insufficient to model the experimentally observed shapes and packing of the cells based on their cadherin expression. We then consider a model in which adhesion leads to a surface increase, balanced by cell cortex contraction. Using the experimentally observed distributions of E- and N-cadherin, we simulate the packing and cell shapes in the wild-type eye. Furthermore, by changing only the corresponding parameters, this model can describe the mutants with different numbers of cells or changes in cadherin expression. PMID:18003929

  9. Antiobesity Action of ACAM by Modulating the Dynamics of Cell Adhesion and Actin Polymerization in Adipocytes.

    Science.gov (United States)

    Murakami, Kazutoshi; Eguchi, Jun; Hida, Kazuyuki; Nakatsuka, Atsuko; Katayama, Akihiro; Sakurai, Miwa; Choshi, Haruki; Furutani, Masumi; Ogawa, Daisuke; Takei, Kohji; Otsuka, Fumio; Wada, Jun

    2016-05-01

    Coxsackie virus and adenovirus receptor-like membrane protein (CLMP) was identified as the tight junction-associated transmembrane protein of epithelial cells with homophilic binding activities. CLMP is also recognized as adipocyte adhesion molecule (ACAM), and it is upregulated in mature adipocytes in rodents and humans with obesity. Here, we present that aP2 promoter-driven ACAM transgenic mice are protected from obesity and diabetes with the prominent reduction of adipose tissue mass and smaller size of adipocytes. ACAM is abundantly expressed on plasma membrane of mature adipocytes and associated with formation of phalloidin-positive polymerized form of cortical actin (F-actin). By electron microscopy, the structure of zonula adherens with an intercellular space of ∼10-20 nm was observed with strict parallelism of the adjoining cell membranes over distances of 1-20 μm, where ACAM and γ-actin are abundantly expressed. The formation of zonula adherens may increase the mechanical strength, inhibit the adipocyte hypertrophy, and improve the insulin sensitivity. PMID:26956488

  10. Changes in membrane sphingolipid composition modulate dynamics and adhesion of integrin nanoclusters

    NARCIS (Netherlands)

    C. Eich (Christina); C. Manzo (Carlo); S. de Keijzer (Sandra); G.J. Bakker (Gert-Jan); I. Reinieren-Beeren (Inge); M.F. García-Parajo (Maria); A. Cambi (Alessandra)

    2016-01-01

    textabstractSphingolipids are essential constituents of the plasma membrane (PM) and play an important role in signal transduction by modulating clustering and dynamics of membrane receptors. Changes in lipid composition are therefore likely to influence receptor organisation and function, but how t

  11. A Semi-Analytical Method for Determining the Energy Release Rate of Cracks in Adhesively-Bonded Single-Lap Composite Joints

    Science.gov (United States)

    Yang, Charles; Sun, Wenjun; Tomblin, John S.; Smeltzer, Stanley S., III

    2007-01-01

    A semi-analytical method for determining the strain energy release rate due to a prescribed interface crack in an adhesively-bonded, single-lap composite joint subjected to axial tension is presented. The field equations in terms of displacements within the joint are formulated by using first-order shear deformable, laminated plate theory together with kinematic relations and force equilibrium conditions. The stress distributions for the adherends and adhesive are determined after the appropriate boundary and loading conditions are applied and the equations for the field displacements are solved. Based on the adhesive stress distributions, the forces at the crack tip are obtained and the strain energy release rate of the crack is determined by using the virtual crack closure technique (VCCT). Additionally, the test specimen geometry from both the ASTM D3165 and D1002 test standards are utilized during the derivation of the field equations in order to correlate analytical models with future test results. The system of second-order differential field equations is solved to provide the adherend and adhesive stress response using the symbolic computation tool, Maple 9. Finite element analyses using J-integral as well as VCCT were performed to verify the developed analytical model. The finite element analyses were conducted using the commercial finite element analysis software ABAQUS. The results determined using the analytical method correlated well with the results from the finite element analyses.

  12. Adhesive Categories

    DEFF Research Database (Denmark)

    Lack, Stephen; Sobocinski, Pawel

    2003-01-01

    We introduce adhesive categories, which are categories with structure ensuring that pushouts along monomorphisms are well-behaved. Many types of graphical structures used in computer science are shown to be examples of adhesive categories. Double-pushout graph rewriting generalises well...... to rewriting on arbitrary adhesive categories....

  13. Adhesive Categories

    DEFF Research Database (Denmark)

    Lack, Stephen; Sobocinski, Pawel

    2004-01-01

    We introduce adhesive categories, which are categories with structure ensuring that pushouts along monomorphisms are well-behaved. Many types of graphical structures used in computer science are shown to be examples of adhesive categories. Double-pushout graph rewriting generalises well...... to rewriting on arbitrary adhesive categories....

  14. Large-Scale Gas Dynamics in the Adhesion Model: Implications for Massive Galaxy Formation

    CERN Document Server

    Domínguez-Tenreiro, R; Martínez-Serrano, F; Serna, A

    2010-01-01

    The mass assembly and star formation histories of massive galaxies identified at low redshift z in different cosmological hydrodynamical simulations, have been studied through a detailed follow-up backwards in time of their constituent mass elements (sampled by particles) of different types. Then, the configurations they depict at progressively higher zs have been analysed. The analyses show that these histories share common generic patterns, irrespective of particular circumstances. In any case, the results we have found are different depending on the particle type. The most outstanding differences follow. We have found that by z ~ 3.5 - 6, mass elements identified as stellar particles at z=0 exhibit a gaseous cosmic-web-like morphology with scales of ~ 1 physical Mpc, where the densest mass elements have already turned into stars by z ~ 6. These settings are in fact the densest pieces of the cosmic web, where no hot particles show up, and dynamically organized as a hierarchy of flow convergence regions, tha...

  15. Dry-Surface Simulation Method for the Determination of the Work of Adhesion of Solid-Liquid Interfaces.

    Science.gov (United States)

    Leroy, Frédéric; Müller-Plathe, Florian

    2015-08-01

    We introduce a methodology, referred to as the dry-surface method, to calculate the work of adhesion of heterogeneous solid-liquid interfaces by molecular simulation. This method employs a straightforward thermodynamic integration approach to calculate the work of adhesion as the reversible work to turn off the attractive part of the actual solid-liquid interaction potential. It is formulated in such a way that it may be used either to evaluate the ability of force fields to reproduce reference values of the work of adhesion or to optimize force-field parameters with reference values of the work of adhesion as target quantities. The methodology is tested in the case of water on a generic model of nonpolar substrates with the structure of gold. It is validated through a quantitative comparison to phantom-wall calculations and against a previous characterization of the thermodynamics of the gold-water interface. It is found that the work of adhesion of water on nonpolar substrates is a nonlinear function of the microscopic solid-liquid interaction energy parameter. We also comment on the ability of mean-field approaches to predict the work of adhesion of water on nonpolar substrates. In addition, we discuss in detail the information on the solid-liquid interfacial thermodynamics delivered by the phantom-wall approach. We show that phantom-wall calculations yield the solid-liquid interfacial tension relative to the solid surface tension rather than the absolute solid-liquid interfacial tension as previously believed.

  16. Strong adhesion and friction coupling in hierarchical carbon nanotube arrays for dry adhesive applications.

    Science.gov (United States)

    Hu, Shihao; Xia, Zhenhai; Gao, Xiaosheng

    2012-04-01

    The adhesion and friction coupling of hierarchical carbon nanotube arrays was investigated with a hierarchical multiscale modeling approach. At device level, vertically aligned carbon nanotube (VA-CNT) arrays with laterally distributed segments on top were analyzed via finite element methods to determine the macroscopic adhesion and friction force coupling. At the nanoscale, molecular dynamics simulation was performed to explore the origin of the adhesion enhancement due to the existence of the laterally distributed CNTs. The results show interfacial adhesion force is drastically promoted by interfacial friction force when a single lateral CNT is being peeled from an amorphous carbon substrate. By fitting with experiments, we find that under shearing loadings the maximum interfacial adhesion force is increased by a factor of ~5, compared to that under normal loadings. Pre-existing surface asperities of the substrate have proven to be the source of generating large interfacial friction, which in turn results in an enhanced adhesion. The critical peeling angles derived from the continuum and nano- levels are comparable to those of geckos and other synthetic adhesives. Our analysis indicates that the adhesion enhancement factor of the hierarchically structured VA-CNT arrays could be further increased by uniformly orienting the laterally distributed CNTs on top. Most importantly, a significant buckling of the lateral CNT at peeling front is captured on the molecular level, which provides a basis for the fundamental understanding of local deformation, and failure mechanisms of nanofibrillar structures. This work gives an insight into the durability issues that prevent the success of artificial dry adhesives.

  17. A stochastic phase-field model determined from molecular dynamics

    KAUST Repository

    von Schwerin, Erik

    2010-03-17

    The dynamics of dendritic growth of a crystal in an undercooled melt is determined by macroscopic diffusion-convection of heat and by capillary forces acting on the nanometer scale of the solid-liquid interface width. Its modelling is useful for instance in processing techniques based on casting. The phase-field method is widely used to study evolution of such microstructural phase transformations on a continuum level; it couples the energy equation to a phenomenological Allen-Cahn/Ginzburg-Landau equation modelling the dynamics of an order parameter determining the solid and liquid phases, including also stochastic fluctuations to obtain the qualitatively correct result of dendritic side branching. This work presents a method to determine stochastic phase-field models from atomistic formulations by coarse-graining molecular dynamics. It has three steps: (1) a precise quantitative atomistic definition of the phase-field variable, based on the local potential energy; (2) derivation of its coarse-grained dynamics model, from microscopic Smoluchowski molecular dynamics (that is Brownian or over damped Langevin dynamics); and (3) numerical computation of the coarse-grained model functions. The coarse-grained model approximates Gibbs ensemble averages of the atomistic phase-field, by choosing coarse-grained drift and diffusion functions that minimize the approximation error of observables in this ensemble average. © EDP Sciences, SMAI, 2010.

  18. IGF-1 Receptor and adhesion signaling: an important axis in determining cancer cell phenotype and therapy resistance.

    Directory of Open Access Journals (Sweden)

    Orla T Cox

    2015-07-01

    Full Text Available IGF-1R expression and activation levels generally cannot be correlated in cancer cells, suggesting that cellular proteins may modulate IGF-1R activity. Strong candidates for such modulation are found in cell-matrix and cell-cell adhesion signaling complexes. Activated IGF-1R is present at focal adhesions, where it can stabilize β1 integrin and participate in signaling complexes that promote invasiveness associated with epithelial mesenchymal transition (EMT, and resistance to therapy. Whether IGF-1R contributes to EMT or to non-invasive tumor growth may be strongly influenced by the degree of ECM engagement and the presence or absence of key proteins in IGF-1R-cell adhesion complexes. One such protein is PDLIM2, which promotes both cell polarization and EMT by regulating the stability of transcription factors including NFκB, STATs and beta catenin. PDLIM2 exhibits tumor suppressor activity, but is also highly expressed in certain invasive cancers. It is likely that distinct adhesion complex proteins modulate IGF-1R signaling during cancer progression or adaptive responses to therapy. Thus, identifying the key modulators will be important for developing effective therapeutic strategies and predictive biomarkers.

  19. Differential Dynamics of α5 Integrin, Paxillin, and α-Actinin during Formation and Disassembly of Adhesions in Migrating Cells

    OpenAIRE

    Laukaitis, Christina M; Webb, Donna J.; Donais, Karen; Horwitz, Alan F.

    2001-01-01

    To investigate the mechanisms by which adhesions form and disperse in migrating cells, we expressed α5 integrin, α-actinin, and paxillin as green fluorescent protein (GFP) fusions. All localized with their endogenous counterparts and did not perturb migration when expressed at moderate levels. α5-GFP also rescued the adhesive defects in CHO B2 cells, which are α5 integrin deficient. In ruffling cells, α5-GFP and α-actinin–GFP localized prominently at the leading edge in membrane protrusions. ...

  20. Pivotal Role of AKAP12 in the Regulation of Cellular Adhesion Dynamics: Control of Cytoskeletal Architecture, Cell Migration, and Mitogenic Signaling

    Directory of Open Access Journals (Sweden)

    Shin Akakura

    2012-01-01

    Full Text Available Cellular dynamics are controlled by key signaling molecules such as cAMP-dependent protein kinase (PKA and protein kinase C (PKC. AKAP12/SSeCKS/Gravin (AKAP12 is a scaffold protein for PKA and PKC which controls actin-cytoskeleton reorganization in a spatiotemporal manner. AKAP12 also acts as a tumor suppressor which regulates cell-cycle progression and inhibits Src-mediated oncogenic signaling and cytoskeletal pathways. Reexpression of AKAP12 causes cell flattening, reorganization of the actin cytoskeleton, and the production of normalized focal adhesion structures. Downregulation of AKAP12 induces the formation of thickened, longitudinal stress fibers and the proliferation of adhesion complexes. AKAP12-null mouse embryonic fibroblasts exhibit hyperactivation of PKC, premature cellular senescence, and defects in cytokinesis, relating to the loss of PKC scaffolding activity by AKAP12. AKAP12-null mice exhibit increased cell senescence and increased susceptibility to carcinogen-induced oncogenesis. The paper describes the regulatory and scaffolding functions of AKAP12 and how it regulates cell adhesion, signaling, and oncogenic suppression.

  1. Platelet adhesion: structural and functional diversity of short dystrophin and utrophins in the formation of dystrophin-associated-protein complexes related to actin dynamics.

    Science.gov (United States)

    Cerecedo, Doris; Martínez-Rojas, Dalila; Chávez, Oscar; Martínez-Pérez, Francisco; García-Sierra, Francisco; Rendon, Alvaro; Mornet, Dominique; Mondragón, Ricardo

    2005-12-01

    Platelets are dynamic cell fragments that modify their shape during activation. Utrophin and dystrophins are minor actin-binding proteins present in muscle and non-muscle cytoskeleton. In the present study, we characterised the pattern of Dp71 isoforms and utrophin gene products by immunoblot in human platelets. Two new dystrophin isoforms were found, Dp71f and Dp71 d, as well as the Up71 isoform and the dystrophin-associated proteins, alpha and beta -dystrobrevins. Distribution of Dp71d/Dp71delta110m, Up400/Up71 and dystrophin-associated proteins in relation to the actin cytoskeleton was evaluated by confocal microscopy in both resting and platelets adhered on glass. Formation of two dystrophin-associated protein complexes (Dp71d/Dp71delta110m approximately DAPC and Up400/Up71 approximately DAPC) was demonstrated by co-immunoprecipitation and their distribution in relation to the actin cytoskeleton was characterised during platelet adhesion. The Dp71d/Dp71delta100m approximately DAPC is maintained mainly at the granulomere and is associated with dynamic structures during activation by adhesion to thrombin-coated surfaces. Participation of both Dp71d/Dp71delta110m approximately DAPC and Up400/Up71 approximately DAPC in the biological roles of the platelets is discussed.

  2. INDIRECT DETERMINATION METHOD OF DYNAMIC FORCEBY USING CEPSTRUM ANALYSIS

    Institute of Scientific and Technical Information of China (English)

    吴淼; 魏任之

    1996-01-01

    The dynamic load spectrum is one of the most important basis of design and dynamic characteristics analysis of machines. But it is difficult to measure it on many occasions, especially for mining machines, due to their bad working circumstances and high cost of measurements. For such situation, the load spectrum has to be obtained by indirect determination methods. A new method to identify the load spectrum, cepstrum analysis method, was presented in this paper.This method can be used to eliminate the filtering influence of transfer function to the response signals so that the load spectrum can be determined indirectly. The experimental and engineering actual examples indicates that this method has the advantages that the calculation is simple and the measurement is easy.

  3. A system dynamics model to determine products mix

    OpenAIRE

    Mahtab Hajghasem; Payam Makvandi; Seyed Shahrooz Seyedi Hosseininia

    2014-01-01

    This paper presents an implementation of system dynamics model to determine appropriate product mix by considering various factors such as labor, materials, overhead, etc. for an Iranian producer of cosmetic and sanitary products. The proposed model of this paper considers three hypotheses including the relationship between product mix and profitability, optimum production capacity and having minimum amount of storage to take advantage of low cost production. The implementation of system dyna...

  4. The neural cell adhesion molecule

    DEFF Research Database (Denmark)

    Berezin, V; Bock, E; Poulsen, F M

    2000-01-01

    During the past year, the understanding of the structure and function of neural cell adhesion has advanced considerably. The three-dimensional structures of several of the individual modules of the neural cell adhesion molecule (NCAM) have been determined, as well as the structure of the complex...... between two identical fragments of the NCAM. Also during the past year, a link between homophilic cell adhesion and several signal transduction pathways has been proposed, connecting the event of cell surface adhesion to cellular responses such as neurite outgrowth. Finally, the stimulation of neurite...

  5. Stretchable, adhesion-tunable dry adhesive by surface wrinkling.

    Science.gov (United States)

    Jeong, Hoon Eui; Kwak, Moon Kyu; Suh, Kahp Y

    2010-02-16

    We introduce a simple yet robust method of fabricating a stretchable, adhesion-tunable dry adhesive by combining replica molding and surface wrinkling. By utilizing a thin, wrinkled polydimethyl siloxane (PDMS) sheet with a thickness of 1 mm with built-in micropillars, active, dynamic control of normal and shear adhesion was achieved. Relatively strong normal (approximately 10.8 N/cm(2)) and shear adhesion (approximately 14.7 N/cm(2)) forces could be obtained for a fully extended (strained) PDMS sheet (prestrain of approximately 3%), whereas the forces could be rapidly reduced to nearly zero once the prestrain was released (prestrain of approximately 0.5%). Moreover, durability tests demonstrated that the adhesion strength in both the normal and shear directions was maintained over more than 100 cycles of attachment and detachment.

  6. Stretchable, Adhesion-Tunable Dry Adhesive by Surface Wrinkling

    KAUST Repository

    Jeong, Hoon Eui

    2010-02-16

    We introduce a simple yet robust method of fabricating a stretchable, adhesion-tunable dry adhesive by combining replica molding and surface wrinkling. By utilizing a thin, wrinkled polydimethyl siloxane (PDMS) sheet with a thickness of 1 mm with built-in micropillars, active, dynamic control of normal and shear adhesion was achieved. Relatively strong normal (∼10.8 N/cm2) and shear adhesion (∼14.7 N/cm2) forces could be obtained for a fully extended (strained) PDMS sheet (prestrain of∼3%), whereas the forces could be rapidly reduced to nearly zero once the prestrain was released (prestrain of ∼0.5%). Moreover, durability tests demonstrated that the adhesion strength in both the normal and shear directions was maintained over more than 100 cycles of attachment and detachment. © 2010 American Chemical Society.

  7. [Simultaneous determination of 23 ester compounds in cigarette water-borne adhesives by liquid-liquid extraction and gas chromatography-mass spectrometry].

    Science.gov (United States)

    Gong, Shuguo; Kong, Bo; Tuo, Suxing; Dai, Yunhui; Wu, Mingjian; Tan, Liquan; Liu, Wei

    2013-10-01

    A method of gas chromatography-mass spectrometry (GC-MS) with liquid-liquid extraction has been developed for the simultaneous determination of 23 ester compounds including acetate esters, acrylic esters, metacrylic acid esters and phthalate acid esters in cigarette water-borne adhesives. After dispersed in water, the sample was extracted by n-hexane solution containing phenyl ethyl propionate as internal standard substance. Then, the solution was centrifuged and filtrated through a 0.45 microm organic membrane filter. Finally, the solution was separated on a DB-WAXETR column (60 m x 0.25 mm x 0.25 microm), and detected with MS in selected ion monitoring mode, and quantified by internal standard method. The results showed a good linear correlation in the range of 0.4-50.0 mg/L. The recoveries of the ester compounds spiked in the sample were 81.8%-109.1%, and the relative standard deviations (RSDs, n = 5) were less than 4%. The limits of detection (LODs) and limits of quantification (LOQs were in the ranges of 0.02-0.76 mg/kg and 0.04-2.52 mg/kg, respectively. The method is simple, time-saving, and has high sensitivity and good reproducibility. It can be applied to the determination of the 23 ester compounds in cigarette water-borne adhesives.

  8. A system dynamics model to determine products mix

    Directory of Open Access Journals (Sweden)

    Mahtab Hajghasem

    2014-02-01

    Full Text Available This paper presents an implementation of system dynamics model to determine appropriate product mix by considering various factors such as labor, materials, overhead, etc. for an Iranian producer of cosmetic and sanitary products. The proposed model of this paper considers three hypotheses including the relationship between product mix and profitability, optimum production capacity and having minimum amount of storage to take advantage of low cost production. The implementation of system dynamics on VENSIM software package has confirmed all three hypotheses of the survey and suggested that in order to reach better mix product, it is necessary to reach optimum production planning, take advantage of all available production capacities and use inventory management techniques.

  9. Clustering determines the dynamics of complex contagions in multiplex networks

    CERN Document Server

    Zhuang, Yong; Yağan, Osman

    2016-01-01

    We present the mathematical analysis of generalized complex contagions in clustered multiplex networks for susceptible-infected-recovered (SIR)-like dynamics. The model is intended to understand diffusion of influence, or any other spreading process implying a threshold dynamics, in setups of interconnected networks with significant clustering. The contagion is assumed to be general enough to account for a content-dependent linear threshold model, where each link type has a different weight (for spreading influence) that may depend on the content (e.g., product, rumor, political view) that is being spread. Using the generating functions formalism, we determine the conditions, probability, and expected size of the emergent global cascades. This analysis provides a generalization of previous approaches and is specially useful in problems related to spreading and percolation. The results present non trivial dependencies between the clustering coefficient of the networks and its average degree. In particular, sev...

  10. Plekhh2, a novel podocyte protein downregulated in human focal segmental glomerulosclerosis, is involved in matrix adhesion and actin dynamics.

    Science.gov (United States)

    Perisic, Ljubica; Lal, Mark; Hulkko, Jenny; Hultenby, Kjell; Önfelt, Björn; Sun, Ying; Dunér, Fredrik; Patrakka, Jaakko; Betsholtz, Christer; Uhlen, Mathias; Brismar, Hjalmar; Tryggvason, Karl; Wernerson, Annika; Pikkarainen, Timo

    2012-11-01

    Pleckstrin homology domain-containing, family H (with MyTH4 domain), member 2 (Plekhh2) is a 1491-residue intracellular protein highly enriched in renal glomerular podocytes for which no function has been ascribed. Analysis of renal biopsies from patients with focal segmental glomerulosclerosis revealed a significant reduction in total podocyte Plekhh2 expression compared to controls. Sequence analysis indicated a putative α-helical coiled-coil segment as the only recognizable domain within the N-terminal half of the polypeptide, while the C-terminal half contains two PH, a MyTH4, and a FERM domain. We identified a phosphatidylinositol-3-phosphate consensus-binding site in the PH1 domain required for Plekhh2 localization to peripheral regions of cell lamellipodia. The N-terminal half of Plekkh2 is not necessary for lamellipodial targeting but mediates self-association. Yeast two-hybrid screening showed that Plekhh2 directly interacts through its FERM domain with the focal adhesion protein Hic-5 and actin. Plekhh2 and Hic-5 coprecipitated and colocalized at the soles of podocyte foot processes in situ and Hic-5 partially relocated from focal adhesions to lamellipodia in Plekhh2-expressing podocytes. In addition, Plekhh2 stabilizes the cortical actin cytoskeleton by attenuating actin depolymerization. Our findings suggest a structural and functional role for Plekhh2 in the podocyte foot processes. PMID:22832517

  11. Bacterial Adhesion & Blocking Bacterial Adhesion

    DEFF Research Database (Denmark)

    Vejborg, Rebecca Munk

    2008-01-01

    tract to the microbial flocs in waste water treatment facilities. Microbial biofilms may however also cause a wide range of industrial and medical problems, and have been implicated in a wide range of persistent infectious diseases, including implantassociated microbial infections. Bacterial adhesion...... is the first committing step in biofilm formation, and has therefore been intensely scrutinized. Much however, still remains elusive. Bacterial adhesion is a highly complex process, which is influenced by a variety of factors. In this thesis, a range of physico-chemical, molecular and environmental parameters......, which influence the transition from a planktonic lifestyle to a sessile lifestyle, have been studied. Protein conditioning film formation was found to influence bacterial adhesion and subsequent biofilm formation considerable, and an aqueous extract of fish muscle tissue was shown to significantly...

  12. Dynamic change of Adamalysin 19 (ADAM19) in human placentas and its effects on cell invasion and adhesion in human trophoblastic cells

    Institute of Scientific and Technical Information of China (English)

    SANG; QingXiang; Amy

    2009-01-01

    Human ADAM19 is a recently identified member of the ADAM family.It is highly expressed in human placentas,but its dynamic change and function at the human feto-maternal interface during placentation remain to be elucidated.In this present study,the spatial and temporal expression and cellular localization of ADAM19 in normal human placentas were first demonstrated,and the effects of ADAM19 on trophoblast cell adhesion and invasion were further investigated by using a human choriocarcinoma cell line(JEG-3) as an in vitro model.The data demonstrated that ADAM19 was widely distributed in villous cytotrophoblast cells,syncytiotrophoblast cells,column trophoblasts,and villous capillary endothelial cells during early pregnancy.The mRNA and protein level of ADAM19 in placentas was high at gestational weeks 8-9,but diminished significantly at mid-and term pregnancy.In JEG-3 cells,the overexpression of ADAM19 led to diminished cell invasion,as well as increases in cell adhesiveness and the expression of E-cadherin,with no changes in β-catenin expression observed.These data indicate that ADAM19 may participate in the coordinated regulation of human trophoblast cell behaviors during the process of placentation.

  13. An improved layer-by-layer self-assembly technique to generate biointerfaces for platelet adhesion studies: Dynamic LbL

    Science.gov (United States)

    Lopez, Juan Manuel

    sequentially at selected surface locations to generate a composite overlap of presumed platelet adhesion as a function of fibrinogen distribution. The method was unable to distinguish the surface from the adhered cells. The surface inhomogeneity and porosity retained a large amount of acridine orange stain, even in the absence of platelets, and components in the platelet-rich plasma (PRP) were found to fix acridine orange in a mode that fluoresced in the FITC imaging FM. Both of these problems obfuscated the platelet adhesion FM results when using s-LbL surfaces and acridine orange staining of platelets. A dynamic process (d-LbL) was developed in which a solution of the molecule to be layered was constantly washed over the surface, and was constantly mixed to maintain a more homogeneous distribution of solute relative to the surface during the layering process. The d-LbL surfaces were tested as described above, and found to reduce the size and number of regions of anomalous acridine orange pooling trapped by the surface, providing a greater consistency and reliability in identifying platelets. The improved surface was then used in a series of platelet adhesion experiments under static and dynamic flow conditions, and with and without the chemical additive L-arginine. The complex microcharmel system used in prior studies was replaced with a simpler system involving fewer nuisance variables for these tests. The tests were performed on both collagen and fibrinogen surfaces. Collagen has been used as a thrombogenic surface in multiple studies in the literature, but produces additional variables in thrombogenesis control that are avoided when fibrinogen is used. In these tests, fibrinogen was found to be as thrombogenic as collagen, and platelet coverage of both biointerfaces was reduced by L-arginine in a manner similar to previously reported work. The simpler system differed from the previous microchannel system in important factors: (1) It exposed the platelets to much lower

  14. Three-phase hollow-fiber liquid-phase microextraction combined with HPLC-UV for the determination of isothiazolinone biocides in adhesives used for food packaging materials.

    Science.gov (United States)

    Rosero-Moreano, Milton; Canellas, Elena; Nerín, Cristina

    2014-02-01

    The present study deals with the development of a liquid microextraction procedure for enhancing the sensitivity of the determination of 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one in adhesives. The procedure involves a three-phase hollow-fiber liquid-phase microextraction using a semipermeable polypropylene membrane, which contained 1-octanol as the organic phase in the pores of the membrane. The donor and acceptor phases are aqueous acidic and alkaline media, respectively, and the final liquid phase (acceptor) is analyzed by HPLC coupled with diode array detection. The most appropriate conditions were extraction time 20 min, stirring speed 1400 rpm, extraction temperature 50°C. The quantification limits of the method were 0.123 and 0.490 μg/g for 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one, respectively. Three different adhesive samples were successfully analyzed. The procedure was compared to direct analysis using ultra high pressure liquid chromatography coupled with TOF-MS, where the identification of the compounds and the quantification values were confirmed.

  15. DETERMINATION OF BONDING PERFORMANCES OF MODIFIED POLYVINYLACETATE (PVAc AND KLEBIT 303 (K.303 ADHESIVES IN DIFFERENT HOT-SURROUNDINGS

    Directory of Open Access Journals (Sweden)

    Mustafa ALTINOK

    2004-01-01

    Full Text Available In this study, performances of woods bonded with polyvinylacetate (PVAc and Klebit 303 (K.303 thermoplastics glues and PVAc+UF and K.303+UF thermoset glues that were modified with Urea-fomaldehyde were investiguted at various temperatures. In total, 320 experimental samples were investigated at various temperatures which were prepared from pine wood (Pinus sylvestris L., beech wood (Fagus orientalis L. and were bonded with PVAc, K.303, PVAc+UF, K.303+UF glues. After these experimental samples were held for two hours at 20 °C, 40 °C, 60 °C, 80 °C temperature, tensile test was applied according TS EN 205. It was found that the adhesion performance of unmodified PVAc and K.303 bonded samples decreases when temperature increases, moreover, this retuction is smaller in samples bonded with PVAc+UF and K.303+UF in comparison to unmodified glues and in samples of beech wood in comparison to pine wood.

  16. New method of determination of spot welding-adhesive joint fatigue life using full field strain evolution

    Science.gov (United States)

    Sadowski, T.; Kneć, M.

    2016-04-01

    Fatigue tests were conducted since more than two hundred years ago. Despite this long period, as fatigue phenomena are very complex, assessment of fatigue response of standard materials or composites still requires a long time. Quite precise way to estimate fatigue parameters is to test at least 30 standardized specimens for the analysed material and further statistical post processing is required. In case of structural elements analysis like hybrid joints (Figure 1), the situation is much more complex as more factors influence the fatigue load capacity due to much more complicated structure of the joint in comparison to standard materials specimen, i.e. occurrence of: welded hot spots or rivets, adhesive layers, local notches creating the stress concentrations, etc. In order to shorten testing time some rapid methods are known: Locati's method [1] - step by step load increments up to failure, Prot's method [2] - constant increase of the load amplitude up to failure; Lehr's method [2] - seeking for the point during regular fatigue loading when an increase of temperature or strains become non-linear. The present article proposes new method of the fatigue response assessment - combination of the Locati's and Lehr's method.

  17. Determination of dynamic fracture toughness using a new experimental technique

    Directory of Open Access Journals (Sweden)

    Cady Carl M.

    2015-01-01

    Full Text Available In other studies dynamic fracture toughness has been measured using Charpy impact and modified Hopkinson Bar techniques. In this paper results will be shown for the measurement of fracture toughness using a new test geometry. The crack propagation velocities range from ∼0.15 mm/s to 2.5 m/s. Digital image correlation (DIC will be the technique used to measure both the strain and the crack growth rates. The boundary of the crack is determined using the correlation coefficient generated during image analysis and with interframe timing the crack growth rate and crack opening can be determined. A comparison of static and dynamic loading experiments will be made for brittle polymeric materials. The analysis technique presented by Sammis et al. [1] is a semi-empirical solution, however, additional Linear Elastic Fracture Mechanics analysis of the strain fields generated as part of the DIC analysis allow for the more commonly used method resembling the crack tip opening displacement (CTOD experiment. It should be noted that this technique was developed because limited amounts of material were available and crack growth rates were to fast for a standard CTOD method.

  18. Quantifying the Determinants of Evolutionary Dynamics Leading to Drug Resistance.

    Directory of Open Access Journals (Sweden)

    Guillaume Chevereau

    Full Text Available The emergence of drug resistant pathogens is a serious public health problem. It is a long-standing goal to predict rates of resistance evolution and design optimal treatment strategies accordingly. To this end, it is crucial to reveal the underlying causes of drug-specific differences in the evolutionary dynamics leading to resistance. However, it remains largely unknown why the rates of resistance evolution via spontaneous mutations and the diversity of mutational paths vary substantially between drugs. Here we comprehensively quantify the distribution of fitness effects (DFE of mutations, a key determinant of evolutionary dynamics, in the presence of eight antibiotics representing the main modes of action. Using precise high-throughput fitness measurements for genome-wide Escherichia coli gene deletion strains, we find that the width of the DFE varies dramatically between antibiotics and, contrary to conventional wisdom, for some drugs the DFE width is lower than in the absence of stress. We show that this previously underappreciated divergence in DFE width among antibiotics is largely caused by their distinct drug-specific dose-response characteristics. Unlike the DFE, the magnitude of the changes in tolerated drug concentration resulting from genome-wide mutations is similar for most drugs but exceptionally small for the antibiotic nitrofurantoin, i.e., mutations generally have considerably smaller resistance effects for nitrofurantoin than for other drugs. A population genetics model predicts that resistance evolution for drugs with this property is severely limited and confined to reproducible mutational paths. We tested this prediction in laboratory evolution experiments using the "morbidostat", a device for evolving bacteria in well-controlled drug environments. Nitrofurantoin resistance indeed evolved extremely slowly via reproducible mutations-an almost paradoxical behavior since this drug causes DNA damage and increases the mutation

  19. Determining habitat quality for species that demonstrate dynamic habitat selection.

    Science.gov (United States)

    Beerens, James M; Frederick, Peter C; Noonburg, Erik G; Gawlik, Dale E

    2015-12-01

    Determining habitat quality for wildlife populations requires relating a species' habitat to its survival and reproduction. Within a season, species occurrence and density can be disconnected from measures of habitat quality when resources are highly seasonal, unpredictable over time, and patchy. Here we establish an explicit link among dynamic selection of changing resources, spatio-temporal species distributions, and fitness for predictive abundance and occurrence models that are used for short-term water management and long-term restoration planning. We used the wading bird distribution and evaluation models (WADEM) that estimate (1) daily changes in selection across resource gradients, (2) landscape abundance of flocks and individuals, (3) conspecific foraging aggregation, and (4) resource unit occurrence (at fixed 400 m cells) to quantify habitat quality and its consequences on reproduction for wetland indicator species. We linked maximum annual numbers of nests detected across the study area and nesting success of Great Egrets (Ardea alba), White Ibises (Eudocimus albus), and Wood Storks (Mycteria americana) over a 20-year period to estimated daily dynamics of food resources produced by WADEM over a 7490 km(2) area. For all species, increases in predicted species abundance in March and high abundance in April were strongly linked to breeding responses. Great Egret nesting effort and success were higher when birds also showed greater conspecific foraging aggregation. Synthesis and applications: This study provides the first empirical evidence that dynamic habitat selection processes and distributions of wading birds over environmental gradients are linked with reproductive measures over periods of decades. Further, predictor variables at a variety of temporal (daily-multiannual) resolutions and spatial (400 m to regional) scales effectively explained variation in ecological processes that change habitat quality. The process used here allows managers to

  20. Determination of the dynamic elastic constants of recycled aggregate concrete

    Science.gov (United States)

    Tsoumani, A. A.; Barkoula, N.-M.; Matikas, T. E.

    2015-03-01

    Nowadays, construction and demolition waste constitutes a major portion of the total solid waste production in the world. Due to both environmental and economical reasons, an increasing interest concerning the use of recycled aggregate to replace aggregate from natural sources is generated. This paper presents an investigation on the properties of recycled aggregate concrete. Concrete mixes are prepared using recycled aggregates at a substitution level between 0 and 100% of the total coarse aggregate. The influence of this replacement on strengthened concrete's properties is being investigated. The properties estimated are: density and dynamic modulus of elasticity at the age of both 7 and 28 days. Also, flexural strength of 28 days specimens is estimated. The determination of the dynamic elastic modulus was made using the ultrasonic pulse velocity method. The results reveal that the existence of recycled aggregates affects the properties of concrete negatively; however, in low levels of substitution the influence of using recycled aggregates is almost negligible. Concluding, the controlled use of recycled aggregates in concrete production may help solve a vital environmental issue apart from being a solution to the problem of inadequate concrete aggregates.

  1. Dynamic determination reserves of the underground gas storage

    Institute of Scientific and Technical Information of China (English)

    谭羽非

    2004-01-01

    One of the key problems in the use of underground gas storage is frequent leakage. It can lead to the actual gas storage amount being less than that accounted for. Combining numerical simulation and parameter auto fit, this paper ascertains the dynamic variation of the pressure in the storage reservoir, adjusts the actual injecting and producing gas to fit the accounted pressure with the tested pressure, obtains the gas leakage of the storage, and then determines the difference between accounted amount and leakage amount. The result is the actual reserves of the storage. The simulation result shows that the method presented can provide a theoretic foundation for estimating the leakage amount, thereby ensuring the actual reserves, searching the leakage route,and reducing leakage by adjusting the storage method.

  2. Determination of Reference Chemical Potential Using Molecular Dynamics Simulations

    Directory of Open Access Journals (Sweden)

    Krishnadeo Jatkar

    2010-01-01

    Full Text Available A new method implementing molecular dynamics (MD simulations for calculating the reference properties of simple gas hydrates has been proposed. The guest molecules affect interaction between adjacent water molecules distorting the hydrate lattice, which requires diverse values of reference properties for different gas hydrates. We performed simulations to validate the experimental data for determining Δ0, the chemical potential difference between water and theoretical empty cavity at the reference state, for structure II type gas hydrates. Simulations have also been used to observe the variation of the hydrate unit cell volume with temperature. All simulations were performed using TIP4P water molecules at the reference temperature and pressure conditions. The values were close to the experimental values obtained by the Lee-Holder model, considering lattice distortion.

  3. Switching stiction and adhesion of a liquid on a solid

    Science.gov (United States)

    Mertens, Stijn F. L.; Hemmi, Adrian; Muff, Stefan; Gröning, Oliver; de Feyter, Steven; Osterwalder, Jürg; Greber, Thomas

    2016-06-01

    When a gecko moves on a ceiling it makes use of adhesion and stiction. Stiction—static friction—is experienced on microscopic and macroscopic scales and is related to adhesion and sliding friction. Although important for most locomotive processes, the concepts of adhesion, stiction and sliding friction are often only empirically correlated. A more detailed understanding of these concepts will, for example, help to improve the design of increasingly smaller devices such as micro- and nanoelectromechanical switches. Here we show how stiction and adhesion are related for a liquid drop on a hexagonal boron nitride monolayer on rhodium, by measuring dynamic contact angles in two distinct states of the solid-liquid interface: a corrugated state in the absence of hydrogen intercalation and an intercalation-induced flat state. Stiction and adhesion can be reversibly switched by applying different electrochemical potentials to the sample, causing atomic hydrogen to be intercalated or not. We ascribe the change in adhesion to a change in lateral electric field of in-plane two-nanometre dipole rings, because it cannot be explained by the change in surface roughness known from the Wenzel model. Although the change in adhesion can be calculated for the system we study, it is not yet possible to determine the stiction at such a solid-liquid interface using ab initio methods. The inorganic hybrid of hexagonal boron nitride and rhodium is very stable and represents a new class of switchable surfaces with the potential for application in the study of adhesion, friction and lubrication.

  4. GPS-Based Reduced Dynamic Orbit Determination Using Accelerometer Data

    Science.gov (United States)

    VanHelleputte, Tom; Visser, Pieter

    2007-01-01

    Currently two gravity field satellite missions, CHAMP and GRACE, are equipped with high sensitivity electrostatic accelerometers, measuring the non-conservative forces acting on the spacecraft in three orthogonal directions. During the gravity field recovery these measurements help to separate gravitational and non-gravitational contributions in the observed orbit perturbations. For precise orbit determination purposes all these missions have a dual-frequency GPS receiver on board. The reduced dynamic technique combines the dense and accurate GPS observations with physical models of the forces acting on the spacecraft, complemented by empirical accelerations, which are stochastic parameters adjusted in the orbit determination process. When the spacecraft carries an accelerometer, these measured accelerations can be used to replace the models of the non-conservative forces, such as air drag and solar radiation pressure. This approach is implemented in a batch least-squares estimator of the GPS High Precision Orbit Determination Software Tools (GHOST), developed at DLR/GSOC and DEOS. It is extensively tested with data of the CHAMP and GRACE satellites. As accelerometer observations typically can be affected by an unknown scale factor and bias in each measurement direction, they require calibration during processing. Therefore the estimated state vector is augmented with six parameters: a scale and bias factor for the three axes. In order to converge efficiently to a good solution, reasonable a priori values for the bias factor are necessary. These are calculated by combining the mean value of the accelerometer observations with the mean value of the non-conservative force models and empirical accelerations, estimated when using these models. When replacing the non-conservative force models with accelerometer observations and still estimating empirical accelerations, a good orbit precision is achieved. 100 days of GRACE B data processing results in a mean orbit fit of

  5. Adhesion and Cohesion

    Directory of Open Access Journals (Sweden)

    J. Anthony von Fraunhofer

    2012-01-01

    Full Text Available 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.

  6. GMT-PP复合材料的界面粘结状况与动态疲劳关系研究%RELATIONSHIPS BETWEEN INTERFACIAL ADHESION AND DYNAMIC FATIGUE OF GMT-PP

    Institute of Scientific and Technical Information of China (English)

    余剑英; 周祖福; 晏石林

    2001-01-01

    The fatigue behaviour of continuous-glass-fibre-mat reinforced polypropylene composites (GMT-PPs) with different interfacial adhesion is investigated by dynamic fatigue tests. The results show that the effect of the interfacial adhesion on the fatigue performance of GMT-PPs is obvious and the improved interfacial adhesion results in an improved fatigue performance. Through the observation of SEM, it is found that the failure modes are different in static tension and dynamic tension for GMT-PPs with strong interfaces. The failure mode of the former is the matrix failure, while that of the latter is the interfacial debonding failure, which means that fatigue loading has a more damaging effect on the interfacial adhesion than on the polymeric matrix. The stronger the interfacial adhesion, the more difficult the interfacial debonding, thus GMT-PPs with well interfacial adhesion has the better the fatigue performance.%采用动态疲劳试验研究了不同界面粘结状况的GMT-PP复合材料的疲劳行为.结果表明:GMT-PP界面粘结状况对其拉伸疲劳性能有明显的影响,界面粘结的改善有利于抗疲劳性的提高.进而通过扫描电镜的观察发现具有良好界面粘结的GMT-PP在静态拉伸时破坏形式为基体破坏,而动态拉伸疲劳破坏则以界面脱粘为主.由于界面粘结强度越高,界面脱粘过程越慢,因而,材料的抗疲劳性越好.

  7. Bond formation and slow heterogeneous dynamics in adhesive spheres with long--ranged repulsion: Quantitative test of Mode Coupling Theory

    OpenAIRE

    Henrich, Oliver; Puertas, Antonio M.; Sperl, Matthias; Baschnagel, Jörg; Fuchs, Matthias

    2007-01-01

    A colloidal system of spheres interacting with both a deep and narrow attractive potential and a shallow long-ranged barrier exhibits a prepeak in the static structure factor. This peak can be related to an additional mesoscopic length scale of clusters and/or voids in the system. Simulation studies of this system have revealed that it vitrifies upon increasing the attraction into a gel-like solid at intermediate densities. The dynamics at the mesoscopic length scale corresponding to the prep...

  8. Dynamic characteristics of rocks and method of their determine

    Directory of Open Access Journals (Sweden)

    Radoslav Schügerl

    2009-01-01

    Full Text Available This paper presents selected problems of the research of the influence of technical vibrations on rocks. The vibrations are the products of the technological procedure, such as mining blasting, ramming of the piles, using of the drilling-equipment or vibration machines. The vibrations could be also evocated by road or train traffic. The most important dynamic characteristics of rocks are dynamic modulus of elasticity Edyn; dynamic modulus of deformation Edef, dyn; dynamic shear-modulus Gdyn; and especially dynamic Poisson´s ratio νdyn. These parameters were obtained by laboratory testing of conglomerate samples.

  9. Determination of the dynamical structure of galaxies using optical spectra

    OpenAIRE

    De Rijcke, S.; Dejonghe, H.

    1998-01-01

    Galaxy spectra are a rich source of kinematical information since the shapes of the absorption lines reflect the movement of stars along the line-of-sight. We present a technique to directly build a dynamical model for a galaxy by fitting model spectra, calculated from a dynamical model, to the observed galaxy spectra. Using synthetic spectra from a known galaxy model we demonstrate that this technique indeed recovers the essential dynamical characteristics of the galaxy model. Moreover, the ...

  10. Mechanisms of adhesion in geckos.

    Science.gov (United States)

    Autumn, Kellar; Peattie, Anne M

    2002-12-01

    The extraordinary adhesive capabilities of geckos have challenged explanation for millennia, since Aristotle first recorded his observations. We have discovered many of the secrets of gecko adhesion, yet the millions of dry, adhesive setae on the toes of geckos continue to generate puzzling new questions and valuable answers. Each epidermally-derived, keratinous seta ends in hundreds of 200 nm spatular tips, permitting intimate contact with rough and smooth surfaces alike. Prior studies suggested that adhesive force in gecko setae was directly proportional to the water droplet contact angle (θ) , an indicator of the free surface energy of a substrate. In contrast, new theory suggests that adhesion energy between a gecko seta and a surface (W(GS)) is in fact proportional to (1 + cosθ), and only for θ > 60°. A reanalysis of prior data, in combination with our recent study, support the van der Waals hypothesis of gecko adhesion, and contradict surface hydrophobicity as a predictor of adhesion force. Previously, we and our collaborators measured the force production of a single seta. Initial efforts to attach a seta failed because of improper 3D orientation. However, by simulating the dynamics of gecko limbs during climbing (based on force plate data) we discovered that, in single setae, a small normal preload, combined with a 5 μm displacement yielded a very large adhesive force of 200 microNewton (μN), 10 times that predicted by whole-animal measurements. 6.5 million setae of a single tokay gecko attached maximally could generate 130 kg force. This raises the question of how geckos manage to detach their feet in just 15 ms. We discovered that simply increasing the angle that the setal shaft makes with the substrate to 30° causes detachment. Understanding how simultaneous attachment and release of millions of setae are controlled will require an approach that integrates levels ranging from molecules to lizards.

  11. Advanced adhesives in electronics

    CERN Document Server

    Bailey, C

    2011-01-01

    Adhesives are widely used in the manufacture of electronic devices to act as passive and active components. Recently there has been considerable interest in the use of conductive adhesives. This book reviews key types of conductive adhesives, processing methods, properties and the way they can be modelled as well as potential applications.$bAdhesives for electronic applications serve important functional and structural purposes in electronic components and packaging, and have developed significantly over the last few decades. Advanced adhesives in electronics reviews recent developments in adhesive joining technology, processing and properties. The book opens with an introduction to adhesive joining technology for electronics. Part one goes on to cover different types of adhesive used in electronic systems, including thermally conductive adhesives, isotropic and anisotropic conductive adhesives and underfill adhesives for flip-chip applications. Part two focuses on the properties and processing of electronic ...

  12. Does the transition to chaos determine the dynamic aperture?

    International Nuclear Information System (INIS)

    We review the important notion of the dynamic aperture of a storage ring with emphasis on its relation to general ideas of dynamical instability, notably the transition to chaos. Practical approaches to the problem are compared. We suggest a somewhat novel quantitative guide to the old problem of choosing machine tunes based on a heuristic blend of KAM theory and resonance selection rules

  13. Bioassay-Guided Isolation and HPLC Determination of Bioactive Compound That Relate to the Antiplatelet Activity (Adhesion, Secretion, and Aggregation from Solanum lycopersicum

    Directory of Open Access Journals (Sweden)

    Eduardo Fuentes

    2012-01-01

    Full Text Available In seeking the functionality of foodstuff applicable to medicine, ripe tomato fruits were found to show an antiplatelet activity. Therefore, the bioactive compound was isolated, structurally identified, and studied for an inhibitory effects on platelet adhesion, secretion, and aggregation. The concentration of adenosine in ripe tomato fruits (pulp and skin extracts and its processing by-products (paste and pomace was determined by reversed-phase high-performance liquid chromatography (HPLC. According to platelet aggregation inhibition induced by ADP, the total extract residual was fractionated by liquid-liquid separation, obtaining aqueous, ethyl acetate and petroleum ether extracts. The aqueous extract was subjected to repeated permeation over sephadex LH-20 and semipreparative TLC. The isolate finally obtained was identified as adenosine on the basis of ESI-MS, 1H NMR, HPLC, and UV spectra. Adenosine concentration dependently (2.3–457 μM platelet aggregation inhibited induced by ADP. Also, adenosine present inhibition of platelet secretion and thrombus formation under flow conditions. The quantitative HPLC analysis revealed significant amounts of adenosine in ripe tomato fruits and its processing by-products. From these results, extracts/fractions of ripe tomato fruits and their processing by-products may be referred to as functional food and functional ingredients containing a compound that inhibits platelet function with a potent preventive effect on thrombus formation, as those that occur in stroke.

  14. Bond formation and slow heterogeneous dynamics in adhesive spheres with long-ranged repulsion: quantitative test of mode coupling theory.

    Science.gov (United States)

    Henrich, O; Puertas, A M; Sperl, M; Baschnagel, J; Fuchs, M

    2007-09-01

    A colloidal system of spheres interacting with both a deep and narrow attractive potential and a shallow long-ranged barrier exhibits a prepeak in the static structure factor. This peak can be related to an additional mesoscopic length scale of clusters and/or voids in the system. Simulation studies of this system have revealed that it vitrifies upon increasing the attraction into a gel-like solid at intermediate densities. The dynamics at the mesoscopic length scale corresponding to the prepeak represents the slowest mode in the system. Using mode coupling theory with all input directly taken from simulations, we reveal the mechanism for glassy arrest in the system at 40% packing fraction. The effects of the low-q peak and of polydispersity are considered in detail. We demonstrate that the local formation of physical bonds is the process whose slowing down causes arrest. It remains largely unaffected by the large-scale heterogeneities, and sets the clock for the slow cluster mode. Results from mode-coupling theory without adjustable parameters agree semiquantitatively with the local density correlators but overestimate the lifetime of the mesoscopic structure (voids). PMID:17930244

  15. Cellular prion protein is required for neuritogenesis: fine-tuning of multiple signaling pathways involved in focal adhesions and actin cytoskeleton dynamics

    Directory of Open Access Journals (Sweden)

    Alleaume-Butaux A

    2013-07-01

    Full Text Available Aurélie Alleaume-Butaux,1,2 Caroline Dakowski,1,2 Mathéa Pietri,1,2 Sophie Mouillet-Richard,1,2 Jean-Marie Launay,3,4 Odile Kellermann,1,2 Benoit Schneider1,2 1INSERM, UMR-S 747, 2Paris Descartes University, Sorbonne Paris Cité, UMR-S 747, 3Public Hospital of Paris, Department of Biochemistry, INSERM UMR-S 942, Lariboisière Hospital, Paris, France; 4Pharma Research Department, Hoffmann La Roche Ltd, Basel, Switzerland Abstract: Neuritogenesis is a dynamic phenomenon associated with neuronal differentiation that allows a rather spherical neuronal stem cell to develop dendrites and axon, a prerequisite for the integration and transmission of signals. The acquisition of neuronal polarity occurs in three steps: (1 neurite sprouting, which consists of the formation of buds emerging from the postmitotic neuronal soma; (2 neurite outgrowth, which represents the conversion of buds into neurites, their elongation and evolution into axon or dendrites; and (3 the stability and plasticity of neuronal polarity. In neuronal stem cells, remodeling and activation of focal adhesions (FAs associated with deep modifications of the actin cytoskeleton is a prerequisite for neurite sprouting and subsequent neurite outgrowth. A multiple set of growth factors and interactors located in the extracellular matrix and the plasma membrane orchestrate neuritogenesis by acting on intracellular signaling effectors, notably small G proteins such as RhoA, Rac, and Cdc42, which are involved in actin turnover and the dynamics of FAs. The cellular prion protein (PrPC, a glycosylphosphatidylinositol (GPI-anchored membrane protein mainly known for its role in a group of fatal neurodegenerative diseases, has emerged as a central player in neuritogenesis. Here, we review the contribution of PrPC to neuronal polarization and detail the current knowledge on the signaling pathways fine-tuned by PrPC to promote neurite sprouting, outgrowth, and maintenance. We emphasize that Pr

  16. Collagen remodeling by phagocytosis is determined by collagen substrate topology and calcium-dependent interactions of gelsolin with nonmuscle myosin IIA in cell adhesions

    OpenAIRE

    Arora, P. D.; Wang, Y.; Bresnick, A.; Dawson, J.; Janmey, P. A.; McCulloch, C. A.

    2013-01-01

    We examine how collagen substrate topography, free intracellular calcium ion concentration ([Ca2+]i, and the association of gelsolin with nonmuscle myosin IIA (NMMIIA) at collagen adhesions are regulated to enable collagen phagocytosis. Fibroblasts plated on planar, collagen-coated substrates show minimal increase of [Ca2+]i, minimal colocalization of gelsolin and NMMIIA in focal adhesions, and minimal intracellular collagen degradation. In fibroblasts plated on collagen-coated latex beads th...

  17. Computational Chemistry of Adhesive Bonds

    Science.gov (United States)

    Phillips, Donald H.

    1999-01-01

    This investigation is intended to determine the electrical mechanical, and chemical properties of adhesive bonds at the molecular level. The initial determinations will be followed by investigations of the effects of environmental effects on the chemistry and properties of the bond layer.

  18. Adhesion in microelectronics

    CERN Document Server

    Mittal, K L

    2014-01-01

    This comprehensive book will provide both fundamental and applied aspects of adhesion pertaining to microelectronics in a single and easily accessible source. Among the topics to be covered include; Various theories or mechanisms of adhesionSurface (physical or chemical) characterization of materials as it pertains to adhesionSurface cleaning as it pertains to adhesionWays to improve adhesionUnraveling of interfacial interactions using an array of pertinent techniquesCharacterization of interfaces / interphasesPolymer-polymer adhesionMetal-polymer adhesion  (metallized polymers)Polymer adhesi

  19. New Dynamic Spin Rig Capabilities Used to Determine Rotating Blade Dynamics

    Science.gov (United States)

    Provenza, Andrew J.

    2004-01-01

    The Dynamic Spin Rig Facility at the NASA Glenn Research Center is used to determine the structural response of rotating engine components without the effects of aerodynamic loading. Recently, this rig's capabilities were enhanced through the replacement of grease-lubricated ball bearings with magnetic bearings. Magnetic bearings offer a number of advantages--the most important here being that they not only fully support the rotor system, but excite it as well. Three magnetic bearings support the rotor and provide five axes of controlled motion: an x- and y-axis translation at each of two radial bearings and a z-axis translation in the vertical or axial direction. Sinusoidal excitation (most commonly used) can be imparted on the rotor through the radial magnetic bearings in either a fixed or rotating frame of reference. This excitation is added directly to the magnetic bearing control output. Since the rotor is fully levitated, large translations and rotations of the rotor system can be achieved. Some of the capabilities of this excitation system were determined and reported. The accelerations obtained at the tip of a titanium flat plate test article versus the swept sine excitation sent to both radial bearings in phase and perpendicular to the plane containing the two blades are shown. Recent tests required the excitation of fundamental bending and torsional blade resonances at rotor speeds up to 10,000 rpm. Successful fixed synchronous rotation of the excitation signal provided the best detectable blade resonant vibrations at excitation frequencies up to 1100 Hz for the particular blades of interest. A noncontacting laser measurement system was used to collect blade-tip motions. From these data, the amplitude and frequency of the motion could be determined as well as the blade damping properties. Damping could be determined using two methods: (1) free decay and (2) curve fitting the vibration amplitude as a function of frequency in and around the resonance of

  20. Calibration of a Computation Model for a Reinforced Concrete Structure Against the Experimentally Determined Dynamic Characteristics

    OpenAIRE

    Gavriloaia, Constantin; Budescu, Mihai; Ţăranu, Nicolae; Hohan, Raluca

    2013-01-01

    The dynamic characteristics of the structures range are depending on their mass and lateral stiffness. In the present paper a method for improving the computation model is proposed, thus creating a link between the dynamic characteristics obtained with the computation model based on the finite element method and the experimentally determined dynamic characteristics. The finite element model was obtained using the program ETABS and the experimental dynamic characteristics were obtained on a lo...

  1. Determination of the Dynamic ITER Energy Confinement Time Scalings

    OpenAIRE

    Sonnino, Giorgio; Sonnino, Alberto; Evslin, Jarah; Steinbrecher, György

    2014-01-01

    We derive the differential equation, which is satisfied by the ITER scalings for the dynamic energy confinement time. We show that this differential equation can also be obtained from the differential equation for the energy confinement time, derived from the energy balance equation, when the plasma is near the steady state. We find that the values of the scaling parameters are linked to the second derivative of the power loss, estimated at the steady state. As an example of an application, t...

  2. Determination of Scaling Parameter and Dynamical Resonances in Complex-Rotated Hamiltonian Ⅱ: Numerical Analysis

    Institute of Scientific and Technical Information of China (English)

    LIU Zong-Liang; ZHAO Fang; LI Shao-Hua; ZHAO Mei-Shan; CHEN Chang-Yong

    2008-01-01

    This paper is concerned with the determination of a unique scaling parameter in complex scaling analysis and with accurate calculation of dynamics resonances. In the preceding paper we have presented a theoretical analysis and provided a formalism for dynamical resonance calculations. In this paper we present accurate numerical results for two non-trivial dynamical processes, namely, models of diatomie molecular predissoeiation and of barrier potential scattering for resonances. The results presented in this paper confirm our theoretical analysis, remove a theoretical ambiguity on determination of the complex scaling parameter, and provide an improved understanding for dynamical resonance calculations in rigged Hilbert space.

  3. Quantitative differences in adhesiveness of type 1 fimbriated Escherichia coli due to structural differences in fimH genes.

    Science.gov (United States)

    Sokurenko, E V; Courtney, H S; Maslow, J; Siitonen, A; Hasty, D L

    1995-01-01

    Type 1 fimbriae are heteropolymeric surface organelles responsible for the D-mannose-sensitive (MS) adhesion of Escherichia coli. We recently reported that variation of receptor specificity of type 1 fimbriae can result solely from minor alterations in the structure of the gene for the FimH adhesin subunit. To further study the relationship between allelic variation of the fimH gene and adhesive properties of type 1 fimbriae, the fimH genes from five additional strains were cloned and used to complement the FimH deletion in E. coli KB18. When the parental and recombinant strains were tested for adhesion to immobilized mannan, a wide quantitative range in the ability of bacteria to adhere was noted. The differences in adhesion do not appear to be due to differences in the levels of fimbriation or relative levels of incorporation of FimH, because these parameters were similar in low-adhesion and high-adhesion strains. The nucleotide sequence for each of the fimH genes was determined. Analysis of deduced FimH sequences allowed identification of two sequence homology groups, based on the presence of Asn-70 and Ser-78 or Ser-70 and Asn-78 residues. The consensus sequences for each group conferred very low adhesion activity, and this low-adhesion phenotype predominated among a group of 43 fecal isolates. Strains isolated from a different host niche, the urinary tract, expressed type 1 fimbriae that conferred an increased level of adhesion. The results presented here strongly suggest that the quantitative variations in MS adhesion are due primarily to structural differences in the FimH adhesin. The observed differences in MS adhesion among populations of E. coli isolated from different host niches call attention to the possibility that phenotypic variants of FimH may play a functional role in populations dynamics. PMID:7601831

  4. The evolution of adhesiveness as a social adaptation.

    Science.gov (United States)

    Garcia, Thomas; Doulcier, Guilhem; De Monte, Silvia

    2015-11-27

    Cellular adhesion is a key ingredient to sustain collective functions of microbial aggregates. Here, we investigate the evolutionary origins of adhesion and the emergence of groups of genealogically unrelated cells with a game-theoretical model. The considered adhesiveness trait is costly, continuous and affects both group formation and group-derived benefits. The formalism of adaptive dynamics reveals two evolutionary stable strategies, at each extreme on the axis of adhesiveness. We show that cohesive groups can evolve by small mutational steps, provided the population is already endowed with a minimum adhesiveness level. Assortment between more adhesive types, and in particular differential propensities to leave a fraction of individuals ungrouped at the end of the aggregation process, can compensate for the cost of increased adhesiveness. We also discuss the change in the social nature of more adhesive mutations along evolutionary trajectories, and find that altruism arises before directly beneficial behavior, despite being the most challenging form of cooperation.

  5. The evolution of adhesiveness as a social adaptation.

    Science.gov (United States)

    Garcia, Thomas; Doulcier, Guilhem; De Monte, Silvia

    2015-01-01

    Cellular adhesion is a key ingredient to sustain collective functions of microbial aggregates. Here, we investigate the evolutionary origins of adhesion and the emergence of groups of genealogically unrelated cells with a game-theoretical model. The considered adhesiveness trait is costly, continuous and affects both group formation and group-derived benefits. The formalism of adaptive dynamics reveals two evolutionary stable strategies, at each extreme on the axis of adhesiveness. We show that cohesive groups can evolve by small mutational steps, provided the population is already endowed with a minimum adhesiveness level. Assortment between more adhesive types, and in particular differential propensities to leave a fraction of individuals ungrouped at the end of the aggregation process, can compensate for the cost of increased adhesiveness. We also discuss the change in the social nature of more adhesive mutations along evolutionary trajectories, and find that altruism arises before directly beneficial behavior, despite being the most challenging form of cooperation. PMID:26613415

  6. PH dependent adhesive peptides

    Science.gov (United States)

    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.

  7. Image analysis of blood platelets adhesion.

    Science.gov (United States)

    Krízová, P; Rysavá, J; Vanícková, M; Cieslar, P; Dyr, J E

    2003-01-01

    Adhesion of blood platelets is one of the major events in haemostatic and thrombotic processes. We studied adhesion of blood platelets on fibrinogen and fibrin dimer sorbed on solid support material (glass, polystyrene). Adhesion was carried on under static and dynamic conditions and measured as percentage of the surface covered with platelets. Within a range of platelet counts in normal and in thrombocytopenic blood we observed a very significant decrease in platelet adhesion on fibrin dimer with bounded active thrombin with decreasing platelet count. Our results show the imperative use of platelet poor blood preparations as control samples in experiments with thrombocytopenic blood. Experiments carried on adhesive surfaces sorbed on polystyrene showed lower relative inaccuracy than on glass. Markedly different behaviour of platelets adhered on the same adhesive surface, which differed only in support material (glass or polystyrene) suggest that adhesion and mainly spreading of platelets depends on physical quality of the surface. While on polystyrene there were no significant differences between fibrin dimer and fibrinogen, adhesion measured on glass support material markedly differed between fibrin dimer and fibrinogen. We compared two methods of thresholding in image analysis of adhered platelets. Results obtained by image analysis of spreaded platelets showed higher relative inaccuracy than results obtained by image analysis of platelets centres and aggregates.

  8. DETERMINATION OF FRACTURE MECHANICS PARAMETERS FOR BODIES GYRATION IN UNSTEADY DYNAMIC PROBLEMS

    Directory of Open Access Journals (Sweden)

    V. A. Bazhenov

    2011-05-01

    Full Text Available On the basis of semi-analytical final elements method data validity research and research of effective determination of fracture mechanics parameters for bodies of revolution in non-stationary dynamics problems were conducted. New method of J-integral calculation and crack approximation under dynamic impact are presented.

  9. Determination of fracture mechanics parameters for bodies gyration in unsteady dynamic problems

    Directory of Open Access Journals (Sweden)

    V. A. Bazhenov

    2011-05-01

    Full Text Available On the basis of semi-analytical final elements method data validity research and research of effective determination of fracture mechanics parameters for bodies of revolution in non-stationary dynamics problems were conducted. New method of J-integral calculation and crack approximation under dynamic impact are presented.

  10. Experimental determination of the dynamics of an acoustically levitated sphere

    Science.gov (United States)

    Pérez, Nicolás; Andrade, Marco A. B.; Canetti, Rafael; Adamowski, Julio C.

    2014-11-01

    Levitation of solids and liquids by ultrasonic standing waves is a promising technique to manipulate materials without contact. When a small particle is introduced in certain areas of a standing wave field, the acoustic radiation force pushes the particle to the pressure node. This movement is followed by oscillations of the levitated particle. Aiming to investigate the particle oscillations in acoustic levitation, this paper presents the experimental and numerical characterization of the dynamic behavior of a levitated sphere. To obtain the experimental response, a small sphere is lifted by the acoustic radiation force. After the sphere lift, it presents a damped oscillatory behavior, which is recorded by a high speed camera. To model this behavior, a mass-spring-damper system is proposed. In this model, the acoustic radiation force that acts on the sphere is theoretically predicted by the Gor'kov theory and the viscous forces are modeled by two damping terms, one term proportional to the square of the velocity and another term proportional to the particle velocity. The proposed model was experimentally verified by using different values of sound pressure amplitude. The comparison between numerical and experimental results shows that the model can accurately describe the oscillatory behavior of the sphere in an acoustic levitator.

  11. Determining tumor blood flow parameters from dynamic image measurements

    Science.gov (United States)

    Libertini, Jessica M.

    2008-11-01

    Many recent cancer treatments focus on preventing angiogenesis, the process by which a tumor promotes the growth of large and efficient capillary beds for the increased nourishment required to support the tumor's rapid growth[l]. To measure the efficacy of these treatments in a timely fashion, there is an interest in using data from dynamic sequences of contrast-enhanced medical imaging, such as MRI and CT, to measure blood flow parameters such as perfusion, permeability-surface-area product, and the relative volumes of the plasma and extracellular-extravascular space. Starting with a two compartment model presented by the radiology community[2], this work challenges the application of a simplification to this problem, which was originally developed to model capillary reuptake[3]. While the primary result of this work is the demonstration of the inaccuracy of this simplification, the remainder of the paper is dedicated to presenting alternative methods for calculating the perfusion and plasma volume coefficients. These methods are applied to model data sets based on real patient data, and preliminary results are presented.

  12. Determining tumor blood flow parameters from dynamic image measurements

    Energy Technology Data Exchange (ETDEWEB)

    Libertini, Jessica M [Division of Applied Mathematics, Brown University, Providence, Rhode Island 02906 (United States)], E-mail: Jessica_Libertini@brown.edu

    2008-11-01

    Many recent cancer treatments focus on preventing angiogenesis, the process by which a tumor promotes the growth of large and efficient capillary beds for the increased nourishment required to support the tumor's rapid growth. To measure the efficacy of these treatments in a timely fashion, there is an interest in using data from dynamic sequences of contrast-enhanced medical imaging, such as MRI and CT, to measure blood flow parameters such as perfusion, permeability-surface-area product, and the relative volumes of the plasma and extracellular-extravascular space. Starting with a two compartment model presented by the radiology community, this work challenges the application of a simplification to this problem, which was originally developed to model capillary reuptake. While the primary result of this work is the demonstration of the inaccuracy of this simplification, the remainder of the paper is dedicated to presenting alternative methods for calculating the perfusion and plasma volume coefficients. These methods are applied to model data sets based on real patient data, and preliminary results are presented.

  13. Experimental determination of the dynamics of an acoustically levitated sphere

    Energy Technology Data Exchange (ETDEWEB)

    Pérez, Nicolás, E-mail: nico@fisica.edu.uy [Centro Universitario de Paysandú, Universidad de la República, Paysandú (Uruguay); Andrade, Marco A. B. [Institute of Physics, University of São Paulo, São Paulo (Brazil); Canetti, Rafael [Facultad de Ingeniería, Universidad de la República, Montevideo (Uruguay); Adamowski, Julio C. [Department of Mechatronics and Mechanical Systems Engineering, Escola Politécnica, University of São Paulo, São Paulo (Brazil)

    2014-11-14

    Levitation of solids and liquids by ultrasonic standing waves is a promising technique to manipulate materials without contact. When a small particle is introduced in certain areas of a standing wave field, the acoustic radiation force pushes the particle to the pressure node. This movement is followed by oscillations of the levitated particle. Aiming to investigate the particle oscillations in acoustic levitation, this paper presents the experimental and numerical characterization of the dynamic behavior of a levitated sphere. To obtain the experimental response, a small sphere is lifted by the acoustic radiation force. After the sphere lift, it presents a damped oscillatory behavior, which is recorded by a high speed camera. To model this behavior, a mass-spring-damper system is proposed. In this model, the acoustic radiation force that acts on the sphere is theoretically predicted by the Gor'kov theory and the viscous forces are modeled by two damping terms, one term proportional to the square of the velocity and another term proportional to the particle velocity. The proposed model was experimentally verified by using different values of sound pressure amplitude. The comparison between numerical and experimental results shows that the model can accurately describe the oscillatory behavior of the sphere in an acoustic levitator.

  14. Prevention of bacterial adhesion

    DEFF Research Database (Denmark)

    Klemm, Per; Vejborg, Rebecca Munk; Hancock, Viktoria

    2010-01-01

    that imposes selection pressure for resistant bacteria. New approaches are urgently needed. Targeting bacterial virulence functions directly is an attractive alternative. An obvious target is bacterial adhesion. Bacterial adhesion to surfaces is the first step in colonization, invasion, and biofilm formation....... As such, adhesion represents the Achilles heel of crucial pathogenic functions. It follows that interference with adhesion can reduce bacterial virulence. Here, we illustrate this important topic with examples of techniques being developed that can inhibit bacterial adhesion. Some of these will become...

  15. Particle adhesion and removal

    CERN Document Server

    Mittal, K L

    2015-01-01

    The book provides a comprehensive and easily accessible reference source covering all important aspects of particle adhesion and removal.  The core objective is to cover both fundamental and applied aspects of particle adhesion and removal with emphasis on recent developments.  Among the topics to be covered include: 1. Fundamentals of surface forces in particle adhesion and removal.2. Mechanisms of particle adhesion and removal.3. Experimental methods (e.g. AFM, SFA,SFM,IFM, etc.) to understand  particle-particle and particle-substrate interactions.4. Mechanics of adhesion of micro- and  n

  16. Photochemically reversible liquefaction and solidification of multiazobenzene sugar-alcohol derivatives and application to reworkable adhesives.

    Science.gov (United States)

    Akiyama, Haruhisa; Kanazawa, Satoshi; Okuyama, Yoko; Yoshida, Masaru; Kihara, Hideyuki; Nagai, Hideki; Norikane, Yasuo; Azumi, Reiko

    2014-05-28

    Multiazobenzene compounds, hexakis-O-[4-(phenylazo)phenoxyalkylcarboxyl]-D-mannitols and hexakis-O-[4-(4-hexylphenylazo)phenoxyalkylcarboxyl]-D-mannitols, exhibit photochemically reversible liquefaction and solidification at room temperature. Their photochemical and thermal phase transitions were investigated in detail through thermal analysis, absorption spectroscopy, and dynamic viscoelasticity measurements, and were compared with those of other sugar-alcohol derivatives. Tensile shear strength tests were performed to determine the adhesions of the compounds sandwiched between two glass slides to determine whether the compounds were suitable for application as adhesives. The adhesions were varied by alternately irradiating the compounds with ultraviolet and visible light to photoinduce phase transitions. The azobenzene hexyl tails, lengths of the methylene spacers, and differences in the sugar-alcohol structures affected the photoresponsive properties of the compounds.

  17. System identification approach for determining flight dynamical characteristics of an airship from flight data

    OpenAIRE

    Kornienko, Andrei

    2006-01-01

    The knowledge of dynamical characteristics of a flight vehicle is necessary for the control system design and realization of high fidelity flight simulators. The development of a flight mechanical model and determination of its basic components, as for example mass properties and the major aerodynamic terms, addresses a complex process involving various analytical, numerical and experimental techniques. The objective of this dissertation is a determination of the basic dynamical character...

  18. Properties of Nano SiO2 Modified PVF Adhesive

    Institute of Scientific and Technical Information of China (English)

    CHEN He-sheng; SUN Zhen-ya; XUE Li-hui

    2004-01-01

    Some properties of nano SiO2 modified PVF adhesive were studied. The experimental results show that nano SiO2 can improve the properties of PVF adhesive very well. Meanwhile the modification mechanism of nano SiO2 to PVF adhesive and the applications of this adhesive in paper-plastic composite, concrete and fireproof paint were discussed by using IR and XRD determination.

  19. Candida albicans Amphotericin B-Tolerant Persister Formation is Closely Related to Surface Adhesion.

    Science.gov (United States)

    Sun, Jing; Li, Zhigang; Chu, Haoyue; Guo, Jing; Jiang, Guangshui; Qi, Qingguo

    2016-02-01

    Candida albicans persisters have so far been observed only in biofilm environment; the biofilm element(s) that trigger(s) persister formation are still unknown. In this study, we tried to further elucidate the possible relationship between C. albicans persisters and the early phases of biofilm formation, especially the surface adhesion phase. Three C. albicans strains were surveyed for the formation of persisters. We tested C. albicans persister formation dynamically at different time points during the process of adhesion and biofilm formation. The number of persister cells was determined based on an assessment of cell viability after amphotericin B treatment and colony-forming unit assay. None of the planktonic cultures contained persisters. Immediately following adhesion of C. albicans cells to the surface, persister cells emerged and the proportion of persisters reached a peak of 0.2-0.69 % in approximately 2-h biofilm. As the biofilm matured, the proportion of persisters decreased and was only 0.01-0.02 % by 24 h, while the number of persisters remained stable with no significant change. Persisters were not detected in the absence of an attachment surface which was pre-coated. Persisters were also absent in biofilms that were scraped to disrupt surface adhesion prior to amphotericin B treatment. These results indicate that C. albicans antifungal-tolerant persisters are produced mainly in surface adhesion phase and surface adhesion is required for the emergence and maintenance of C. albicans persisters.

  20. Adhesion property of epoxidized natural rubber (ENR-based adhesives containing calcium carbonate

    Directory of Open Access Journals (Sweden)

    2008-06-01

    Full Text Available The adhesion property (i.e. viscosity, loop tack and peel strength of epoxidized natural rubber (ENR 25 and ENR 50 grade-based pressure-sensitive adhesive was studied in the presence of calcium carbonate. The range of calcium carbonate loaded was from 10 to 50 parts per hundred parts of rubber (phr. Coumarone-indene resin was used as the tackifier and its concentration was fixed at 80 phr. Toluene was chosen as the solvent throughout the investigation. The substrates (PET film/paper were coated with the adhesive using a SHEEN hand coater at a coating thickness of 60 µm. Viscosity of the adhesive was measured by a HAAKE Rotary Viscometer whereas loop tack and peel strength were determined by a Llyod Adhesion Tester operating at 30 cm/min. Results show that viscosity of ENR-based adhesives increases gradually with increase in calcium carbonate loading due to the concentration effect of the filler. However, for loop tack and peel strength, it passes through a maximum at 30 phr calcium carbonate, an observation which is attributed to the optimum wettability of adhesive on the substrate at this adhesive composition. ENR 25-based adhesive consistently exhibits higher adhesion property than ENR 50 for all calcium carbonate loadings studied.

  1. CFD Based Determination of Dynamic Stability Derivatives in Yaw for a Bird

    Institute of Scientific and Technical Information of China (English)

    M. A. Moelyadi; G. Sachs

    2007-01-01

    Dynamic yaw stability derivatives of a gull bird are determined using Computational Fluid Dynamics(CFD) method. Two kinds of motions are applied for calculating the dynamic yaw stability derivatives CNr and CNβ. The first one relates to a lateral translation and, separately, to a yaw rotation. The second one consists of a combined translational and rotational motion. To determine dynamic yaw stability derivatives, the simulation of an unsteady flow with a bird model showing a harmonic motion is performed. The flow solution for each time step is obtained by solving unsteady Euler equations based on a finite volume approach for a small reduced frequency. Then, an evaluation of unsteady forces and moments for one cycle is conducted using harmonic Fourier analysis. The results of the dynamic yaw stability derivatives for both simulations of the model show a good agreement.

  2. Highly compliant shape memory polymer gels for tunable damping and reversible adhesion

    Science.gov (United States)

    Mrozek, Randy A.; Berg, Michael C.; Gold, Christopher S.; Leighliter, Brad; Morton, Jeffrey T.; Lenhart, Joseph L.

    2016-02-01

    Materials that can dynamically change their properties to better adapt to the local environment have potential utility in robotics, aerospace, and coatings. For some of these applications, most notably robotics, it is advantageous for these responsive materials to be highly compliant in an effort to provide dynamic changes in adhesion and mechanical damping within a broad temperature operational environment. In this report, non-aqueous, highly compliant shape-memory polymer gels are developed by incorporating a low density of chemical cross-links into a physically cross-linked thermoplastic elastomer gel. Chemical cross-linkers were evaluated by varying there size and degree of functionality to determine the impact on the mechanical and adhesive properties. As a result of the chemical cross-linking, the gels exhibit modulus plateaus around room temperature and at elevated temperatures above 100 °C, where the thermoplastic elastomer gel typically melts. The materials were designed so that moduli in the plateaued regions were above and below the Dahlquist criteria of 4 × 104 Pa, respectively, where materials with a modulus below this value typically exhibit an increase in adhesion. The shape memory polymer gels were also integrated into fiber-reinforced composites to determine the temperature-dependent changes in mechanical damping. It is anticipated that this work will provide insight into materials design to provide dynamic changes in adhesion and damping to improve robotic appendage manipulation and platform mobility.

  3. Pathophysiology and prevention of postoperative peritoneal adhesions

    Institute of Scientific and Technical Information of China (English)

    Willy Arung1; Michel Meurisse; Olivier Detry

    2011-01-01

    Peritoneal adhesions represent an important clinical challenge in gastrointestinal surgery. Peritoneal adhesions are a consequence of peritoneal irritation by infection or surgical trauma, and may be considered as the pathological part of healing following any peritoneal injury, particularly due to abdominal surgery. The balance between fibrin deposition and degradation is critical in determining normal peritoneal healing or adhesion formation. Postoperative peritoneal adhesions are a major cause of morbidity resulting in multiple complications, many of which may manifest several years after the initial surgical procedure. In addition to acute small bowel obstruction, peritoneal adhesions may cause pelvic or abdominal pain, and infertility. In this paper, the authors reviewed the epidemiology, pathogenesis and various prevention strategies of adhesion formation, using Medline and PubMed search. Several preventive agents against postoperative peritoneal adhesions have been investigated. Their role aims in activating fibrinolysis, hampering coagulation, diminishing the inflammatory response, inhibiting collagen synthesis or creating a barrier between adjacent wound surfaces. Their results are encouraging but most of them are contradictory and achieved mostly in animal model. Until additional findings from future clinical researches, only a meticulous surgery can be recommended to reduce unnecessary morbidity and mortality rates from these untoward effects of surgery. In the current state of knowledge, pre-clinical or clinical studies are still necessary to evaluate the effectiveness of the several proposed prevention strategies of postoperative peritoneal adhesions.

  4. Comparison of percentage of wood fracture surface analyzed by computer and by ISO 6238 in determining the quality of adhesive bonds

    Directory of Open Access Journals (Sweden)

    Alica Lojen

    2009-06-01

    Full Text Available This paper presents the results of measuring and estimating the percentage of wood fracture surface in testing the quality of adhesive bonds by using two methods. The first method is based on ISO 6238. The estimation was carried out by two estimators so as to show the difference in perception. The second method consists of measuring the percentage of wood fracture surface by analyzing digital photography by computer software. The results prove that there is no statistically significant difference between the measurement of the percentage of fracture surface by analyzing digital photography with computer software and the measurement made by standard process. Computer measurement is, however, more reliable and accurate

  5. Measurement of single-cell adhesion strength using a microfluidic assay.

    Science.gov (United States)

    Christ, Kevin V; Williamson, Kyle B; Masters, Kristyn S; Turner, Kevin T

    2010-06-01

    Despite the importance of cell adhesion in numerous physiological, pathological, and biomaterial-related responses, our understanding of adhesion strength at the cell-substrate interface and its relationship to cell function remains incomplete. One reason for this deficit is a lack of accessible experimental approaches that quantify adhesion strength at the single-cell level and facilitate large numbers of tests. The current work describes the design, fabrication, and use of a microfluidic-based method for single-cell adhesion strength measurements. By applying a monotonically increasing flow rate in a microfluidic channel in combination with video microscopy, the adhesion strength of individual NIH3T3 fibroblasts cultured for 24 h on various surfaces was measured. The small height of the channel allows high shear stresses to be generated under laminar conditions, allowing strength measurements on well-spread, strongly adhered cells that cannot be characterized in most conventional assays. This assay was used to quantify the relationship between morphological characteristics and adhesion strength for individual well-spread cells. Cell adhesion strength was found to be positively correlated with both cell area and circularity. Computational fluid dynamics (CFD) analysis was performed to examine the role of cell geometry in determining the actual stress applied to the cell. Use of this method to examine adhesion at the single-cell level allows the detachment of strongly-adhered cells under a highly-controllable, uniform loading to be directly observed and will enable the characterization of biological events and relationships that cannot currently be achieved using existing methods.

  6. Vascular smooth muscle cell stiffness and adhesion to collagen I modified by vasoactive agonists.

    Directory of Open Access Journals (Sweden)

    Zhongkui Hong

    Full Text Available In vascular smooth muscle cells (VSMCs integrin-mediated adhesion to extracellular matrix (ECM proteins play important roles in sustaining vascular tone and resistance. The main goal of this study was to determine whether VSMCs adhesion to type I collagen (COL-I was altered in parallel with the changes in the VSMCs contractile state induced by vasoconstrictors and vasodilators. VSMCs were isolated from rat cremaster skeletal muscle arterioles and maintained in primary culture without passage. Cell adhesion and cell E-modulus were assessed using atomic force microscopy (AFM by repetitive nano-indentation of the AFM probe on the cell surface at 0.1 Hz sampling frequency and 3200 nm Z-piezo travelling distance (approach and retraction. AFM probes were tipped with a 5 μm diameter microbead functionalized with COL-I (1 mg\\ml. Results showed that the vasoconstrictor angiotensin II (ANG-II; 10-6 significantly increased (p<0.05 VSMC E-modulus and adhesion probability to COL-I by approximately 35% and 33%, respectively. In contrast, the vasodilator adenosine (ADO; 10-4 significantly decreased (p<0.05 VSMC E-modulus and adhesion probability by approximately -33% and -17%, respectively. Similarly, the NO donor (PANOate, 10-6 M, a potent vasodilator, also significantly decreased (p<0.05 the VSMC E-modulus and COL-I adhesion probability by -38% and -35%, respectively. These observations support the hypothesis that integrin-mediated VSMC adhesion to the ECM protein COL-I is dynamically regulated in parallel with VSMC contractile activation. These data suggest that the signal transduction pathways modulating VSMC contractile activation and relaxation, in addition to ECM adhesion, interact during regulation of contractile state.

  7. Nanocapillary Adhesion between Parallel Plates.

    Science.gov (United States)

    Cheng, Shengfeng; Robbins, Mark O

    2016-08-01

    Molecular dynamics simulations are used to study capillary adhesion from a nanometer scale liquid bridge between two parallel flat solid surfaces. The capillary force, Fcap, and the meniscus shape of the bridge are computed as the separation between the solid surfaces, h, is varied. Macroscopic theory predicts the meniscus shape and the contribution of liquid/vapor interfacial tension to Fcap quite accurately for separations as small as two or three molecular diameters (1-2 nm). However, the total capillary force differs in sign and magnitude from macroscopic theory for h ≲ 5 nm (8-10 diameters) because of molecular layering that is not included in macroscopic theory. For these small separations, the pressure tensor in the fluid becomes anisotropic. The components in the plane of the surface vary smoothly and are consistent with theory based on the macroscopic surface tension. Capillary adhesion is affected by only the perpendicular component, which has strong oscillations as the molecular layering changes.

  8. Reversible Thermoset Adhesives

    Science.gov (United States)

    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.

  9. Electro-dry-adhesion.

    Science.gov (United States)

    Krahn, Jeffrey; Menon, Carlo

    2012-03-27

    This work presents novel conductive bioinspired dry adhesives with mushroom caps that enable the use of a synergistic combination of electrostatic and van der Waals forces (electro-dry-adhesion). An increase in shear adhesion bond strength of up to 2046% on a wide range of materials is measured when a maximum electrical field of 36.4 V μm(-1) is applied. A suction effect, due to the shape of the dry adhesive fibers, on overall adhesion was not noted for electro-dry-adhesives when testing was performed at both atmospheric and reduced pressure. Utilization of electrostatics to apply a preloading force to dry adhesive fiber arrays allows increased adhesion even after electrostatic force generation has been halted by ensuring the close contact necessary for van der Waals forces to be effective. A comparison is made between self-preloading of the electro-dry-adhesives and the direct application of a normal preloading pressure resulting in nearly the same shear bond strength with an applied voltage of 3.33 kV on the same sample.

  10. Determinants of International Migration to the OECD in a Three-Way Dynamic Panel Framework

    OpenAIRE

    I. RUYSSEN; G. EVERAERT; G. RAYP

    2011-01-01

    This paper investigates the determinants of bilateral immigrant ows to 19 OECD countries between 1998 and 2007 from both advanced and developing origin countries. We pay particular attention to dynamics by including both the lagged migrant ow and the migrant stock to capture partial adjustment and network effects. To correct for the dynamic panel data bias of the fixed effects estimator we use a bootstrap algorithm. Our results indicate that immigrants are primarily attracted by better income...

  11. Determinants and dynamics of migration to OECD countries in a three-dimensional panel framework

    OpenAIRE

    Ruyssen, Ilse; Everaert, Gerdie; Rayp, Glenn

    2014-01-01

    This paper investigates the determinants of bilateral immigrant flows to 19 OECD countries between 1998 and 2007 from both advanced and developing origin countries. We pay particular attention to dynamics by including both the lagged migrant flow and the migrant stock to capture partial adjustment and network effects. To correct for the dynamic panel data bias of the fixed effects estimator we use a bootstrap algorithm. Our results indicate that immigrants are primarily attracted by better in...

  12. Testing Object-Oriented Programs using Dynamic Aspects and Non-Determinism

    DEFF Research Database (Denmark)

    Achenbach, Michael; Ostermann, Klaus

    2010-01-01

    decisions exposing private data. We present an approach that both improves the expressiveness of test cases using non-deterministic choice and reduces design modifications using dynamic aspect-oriented programming techniques. Non-deterministic choice facilitates local definitions of multiple executions...... without parameterization or generation of tests. It also eases modelling naturally non-deterministic program features like IO or multi-threading in integration tests. Dynamic AOP facilitates powerful design adaptations without exposing test features, keeping the scope of these adaptations local to each...... test. We also combine non-determinism and dynamic aspects in a new approach to testing multi-threaded programs using co-routines....

  13. The application of virtual prototyping methods to determine the dynamic parameters of mobile robot

    Science.gov (United States)

    Kurc, Krzysztof; Szybicki, Dariusz; Burghardt, Andrzej; Muszyńska, Magdalena

    2016-04-01

    The paper presents methods used to determine the parameters necessary to build a mathematical model of an underwater robot with a crawler drive. The parameters present in the dynamics equation will be determined by means of advanced mechatronic design tools, including: CAD/CAE software andMES modules. The virtual prototyping process is described as well as the various possible uses (design adaptability) depending on the optional accessories added to the vehicle. A mathematical model is presented to show the kinematics and dynamics of the underwater crawler robot, essential for the design stage.

  14. A computational analysis and suitability assessment of cold-gas dynamic spraying of glass-fiber-reinforced poly-amide 6 for use in direct-adhesion polymer metal hybrid components

    Science.gov (United States)

    Grujicic, M.; Pandurangan, B.; Bell, W. C.; Daqaq, M.; Ma, L.; Seyr, Norbert; Erdmann, Marc; Holzleitner, Jochen

    2008-01-01

    SummaryA transient non-linear dynamics computational analysis of cold-gas dynamic spraying (CGDS) of glass-fiber-reinforced poly-amide (nylon) 6 has been carried out using Ansys-Autodyn [Century Dynamics Inc., Ansys-Autodyn Version 11.0, User Documentation, Century Dynamics Inc. (a subsidiary of ANSYS Inc.), 2007] in order to assess the suitability of this spraying technology for coating of metal stampings used in polymer metal hybrid (PMH) load-bearing automotive component applications. In addition, the suitability of the CGDS is assessed with respect to a need for metal stamping surface preparation/treatment, the ability to deposit polymeric material without significant material degradation, the ability to selectively overcoat the metal stamping, the resulting magnitude of the polymer-to-metal adhesion strength, durability of the polymer/metal bond with respect to prolonged exposure to high-temperature/high-humidity and mechanical/thermal fatigue service conditions, and compatibility with the automotive body-in-white ( BIW) manufacturing process chain. The analysis revealed that CGDS can be considered as a viable technology for coating of metal stampings used in PMH load-bearing automotive component applications.

  15. Loss of cofilin 1 disturbs actin dynamics, adhesion between enveloping and deep cell layers and cell movements during gastrulation in zebrafish.

    Directory of Open Access Journals (Sweden)

    Chun-Wei Lin

    Full Text Available During gastrulation, cohesive migration drives associated cell layers to the completion of epiboly in zebrafish. The association of different layers relies on E-cadherin based cellular junctions, whose stability can be affected by actin turnover. Here, we examined the effect of malfunctioning actin turnover on the epibolic movement by knocking down an actin depolymerizing factor, cofilin 1, using antisense morpholino oligos (MO. Knockdown of cfl1 interfered with epibolic movement of deep cell layer (DEL but not in the enveloping layer (EVL and the defect could be specifically rescued by overexpression of cfl1. It appeared that the uncoordinated movements of DEL and EVL were regulated by the differential expression of cfl1 in the DEL, but not EVL as shown by in situ hybridization. The dissociation of DEL and EVL was further evident by the loss of adhesion between layers by using transmission electronic and confocal microscopy analyses. cfl1 morphants also exhibited abnormal convergent extension, cellular migration and actin filaments, but not involution of hypoblast. The cfl1 MO-induced cell migration defect was found to be cell-autonomous in cell transplantation assays. These results suggest that proper actin turnover mediated by Cfl1 is essential for adhesion between DEL and EVL and cell movements during gastrulation in zebrafish.

  16. Resolving fundamental limits of adhesive bonding in microfabrication.

    Energy Technology Data Exchange (ETDEWEB)

    Hall, Jessica S.; Frischknecht, Amalie Lucile; Emerson, John Allen; Adkins, Douglas Ray; Kent, Michael Stuart; Read, Douglas H.; Giunta, Rachel Knudsen; Lamppa, Kerry P.; Kawaguchi, Stacie; Holmes, Melissa A.

    2004-04-01

    As electronic and optical components reach the micro- and nanoscales, efficient assembly and packaging require the use of adhesive bonds. This work focuses on resolving several fundamental issues in the transition from macro- to micro- to nanobonding. A primary issue is that, as bondline thicknesses decrease, knowledge of the stability and dewetting dynamics of thin adhesive films is important to obtain robust, void-free adhesive bonds. While researchers have studied dewetting dynamics of thin films of model, non-polar polymers, little experimental work has been done regarding dewetting dynamics of thin adhesive films, which exhibit much more complex behaviors. In this work, the areas of dispensing small volumes of viscous materials, capillary fluid flow, surface energetics, and wetting have all been investigated. By resolving these adhesive-bonding issues, we are allowing significantly smaller devices to be designed and fabricated. Simultaneously, we are increasing the manufacturability and reliability of these devices.

  17. Tissue adhesives in otorhinolaryngology

    Directory of Open Access Journals (Sweden)

    Schneider, Gerlind

    2009-01-01

    Full Text Available The development of medical tissue adhesives has a long history without finding an all-purpose tissue adhesive for clinical daily routine. This is caused by the specific demands which are made on a tissue adhesive, and the different areas of application. In otorhinolaryngology, on the one hand, this is the mucosal environment as well as the application on bones, cartilage and periphery nerves. On the other hand, there are stressed regions (skin, oral cavity, pharynx, oesophagus, trachea and unstressed regions (middle ear, nose and paranasal sinuses, cranial bones. But due to the facts that adhesives can have considerable advantages in assuring surgery results, prevention of complications and so reduction of medical costs/treatment expenses, the search for new adhesives for use in otorhinolaryngology will be continued intensively. In parallel, appropriate application systems have to be developed for microscopic and endoscopic use.

  18. LOSS FACTOR AND DYNAMIC YOUNG MODULUS DETERMINATION FOR COMPOSITE SANDWICH BARS REINFORCED WITH STEEL FABRIC

    Directory of Open Access Journals (Sweden)

    Cosmin-Mihai MIRIŢOIU

    2015-05-01

    Full Text Available In this paper I have build some composite sandwich bars. For these bars I have determined the dynamic response by recording their free vibrations. These bars have the core made of polypropylene honeycomb with upper and lower layers reinforced with steel wire mesh. For these bars I have determined the the eigenfrequency of the first eigenmode in this way: the bar was embedded at one end and free at the other where there was placed an accelerometer at 10 mm distance from the edge and I applied an initial force at the free end. I have determined the eigenfrequency because I will use its values for the loss factor and dynamic Young modulus determination.

  19. A Unified Approach to Nonlinear Dynamic Inversion Control with Parameter Determination by Eigenvalue Assignment

    Directory of Open Access Journals (Sweden)

    Yu-Chi Wang

    2015-01-01

    Full Text Available This paper presents a unified approach to nonlinear dynamic inversion control algorithm with the parameters for desired dynamics determined by using an eigenvalue assignment method, which may be applied in a very straightforward and convenient way. By using this method, it is not necessary to transform the nonlinear equations into linear equations by feedback linearization before beginning control designs. The applications of this method are not limited to affine nonlinear control systems or limited to minimum phase problems if the eigenvalues of error dynamics are carefully assigned so that the desired dynamics is stable. The control design by using this method is shown to be robust to modeling uncertainties. To validate the theory, the design of a UAV control system is presented as an example. Numerical simulations show the performance of the design to be quite remarkable.

  20. Sex ratio selection and multi-factorial sex determination in the housefly : A dynamic model

    NARCIS (Netherlands)

    Kozielska, M.A.; Pen, I.R.; Beukeboom, L.W.; Weissing, F.J.

    2006-01-01

    Sex determining (SD) mechanisms are highly variable between different taxonomic groups and appear to change relatively quickly during evolution. Sex ratio selection could be a dominant force causing such changes. We investigate theoretically the effect of sex ratio selection on the dynamics of a mul

  1. Role of the first coordination shell in determining the equilibrium structure and dynamics of simple liquids

    DEFF Research Database (Denmark)

    Toxværd, Søren; Dyre, J. C.

    2011-01-01

    The traditional view that the physical properties of a simple liquid are determined primarily by its repulsive forces was recently challenged by Berthier and Tarjus, who showed that in some cases ignoring the attractions leads to large errors in the dynamics [L. Berthier and G. Tarjus, Phys. Rev....

  2. Isolation and biochemical characterization of underwater adhesives from diatoms.

    Science.gov (United States)

    Poulsen, Nicole; Kröger, Nils; Harrington, Matthew J; Brunner, Eike; Paasch, Silvia; Buhmann, Matthias T

    2014-01-01

    Many aquatic organisms are able to colonize surfaces through the secretion of underwater adhesives. Diatoms are unicellular algae that have the capability to colonize any natural and man-made submerged surfaces. There is great technological interest in both mimicking and preventing diatom adhesion, yet the biomolecules responsible have so far remained unidentified. A new method for the isolation of diatom adhesive material is described and its amino acid and carbohydrate composition determined. The adhesive materials from two model diatoms show differences in their amino acid and carbohydrate compositions, but also share characteristic features including a high content of uronic acids, the predominance of hydrophilic amino acid residues, and the presence of 3,4-dihydroxyproline, an extremely rare amino acid. Proteins containing dihydroxyphenylalanine, which mediate underwater adhesion of mussels, are absent. The data on the composition of diatom adhesives are consistent with an adhesion mechanism based on complex coacervation of polyelectrolyte-like biomolecules.

  3. Use of high and low frequency dielectric measurements in the NDE of adhesively bonded composite joints

    Science.gov (United States)

    Pethrick, R. A.; Hayward, D.; McConnell, B. K.; Crane, R. L.

    2005-05-01

    Dielectric spectroscopy has been developed as a non-destructive technique for assessment of moisture content and structural integrity of adhesively bonded joints. Knowledge of these parameters is particularly crucial for the aerospace industry, since environmental degradation of adhesive joints presents a major limit on their utilization. High and low frequency measurements have been carried out on joints assembled from CFRP adherend, and a commercially available adhesive (AF 163-2K). The samples have been aged in deionised water at 75oC to chart the effect water ingress has on bond durability. In addition, some joints have been exposed to cryogenic temperatures to mimic the conditions joints experience whilst an aircraft is in flight. In this way it has been possible to determine the extent of degradation caused by freezing of water within the joint structure. Dielectric behaviour of the joints was studied in both the frequency and in the time domain. Frequency domain analysis allows the amount and effects of moisture ingress in the bondline to be assessed, whereas the time domain highlights the onset of joint defects with increasing exposure time. Mechanical testing of the joints has been carried out to enable correlation between changes in strength and failure mechanism due to moisture ingress, with changes in the dielectric data. In addition, dielectric studies of the neat adhesive have been undertaken, as have gravimetric and dynamic mechanical thermal analysis. These have helped reveal the effects of ageing upon the adhesive layer itself.

  4. Handbook of adhesion

    CERN Document Server

    Packham, D E

    2006-01-01

    This second edition of the successful Handbook of Adhesion provides concise and authoritative articles covering many aspects of the science and technology associated with adhesion and adhesives. It is intended to fill a gap between the necessarily simplified treatment of the student textbook and the full and thorough treatment of the research monograph and review article. The articles are structured in such a way, with internal cross-referencing and external literature references, that the reader can build up a broader and deeper understanding, as their needs require.This second edition includ

  5. [Endothelial cell adhesion molecules].

    Science.gov (United States)

    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.

  6. Lactobacillus Adhesion to Mucus

    Directory of Open Access Journals (Sweden)

    Maxwell L. Van Tassell

    2011-05-01

    Full Text Available Mucus provides protective functions in the gastrointestinal tract and plays an important role in the adhesion of microorganisms to host surfaces. Mucin glycoproteins polymerize, forming a framework to which certain microbial populations can adhere, including probiotic Lactobacillus species. Numerous mechanisms for adhesion to mucus have been discovered in lactobacilli, including partially characterized mucus binding proteins. These mechanisms vary in importance with the in vitro models studied, which could significantly affect the perceived probiotic potential of the organisms. Understanding the nature of mucus-microbe interactions could be the key to elucidating the mechanisms of probiotic adhesion within the host.

  7. Ice adhesions in relation to freeze stress.

    Science.gov (United States)

    Olien, C R; Smith, M N

    1977-10-01

    In freezing, competitive interaction between ice and hydrophilic plant substances causes an energy of adhesion to develop through the interstitial liquid. The thermodynamic basis for the adhesion energy is discussed, with estimates of the energies involved. In this research, effects of adhesion energy were observed microscopically in conjunction with energies of crystallization and frost desiccation. The complex character of ice in intact crown tissue of winter barley (Hordeum vulgare L.) and the problems of sectioning frozen tissue without producing artifacts led to an alternative study of single barley cells in a mesh of ice and cell wall polymers. Adhesions between ice, cell wall polymers, and the plasmalemma form a complexly interacting system in which the pattern of crystallization is a major factor in determination of stress and injury. PMID:16660124

  8. Sticking around: an up-close look at drop adhesion

    CERN Document Server

    Paxson, Adam T

    2013-01-01

    We present a fluid dynamics video showing the adhesion of a drop to a superhydrophobic surface. We use environmental scanning electron microscopy to observe depinning events at the microscale. As the drop moves along the surface, the advancing portion of the contact line simply lies down onto the upcoming roughness features, contributing negligibly to adhesion. After measuring the local receding contact angle of capillary bridges formed on a micropillar array, we find that these depinning events follow the Gibbs depinning criterion. We further extend this technique to two-scale hierarchical structures to reveal a self-similar depinning mechanism in which the adhesion of the entire drop depends only on the pinning at the very smallest level of roughness hierarchy. With this self-similar depinning mechanism we develop a model to predict the adhesion of drops to superhydrophobic surfaces that explains both the low adhesion on sparsely structured surfaces and the surprisingly high adhesion on surfaces whose featu...

  9. The Global Positioning System (GPS) and attitude determination: Applications and activities in the Flight Dynamics Division

    Science.gov (United States)

    Ketchum, Eleanor; Garrick, Joe

    1995-01-01

    The application of GPS to spacecraft attitude determination is a new and growing field. Although the theoretical literature is extensive, space flight testing is currently sparse and inadequate. As an operations organization, the Flight Dynamics Division (FDD) has the responsibility to investigate this new technology, and determine how best to implement the innovation to provide adequate support for future missions. This paper presents some of the current efforts within FDD with regard to GPS attitude determination. This effort specifically addresses institutional capabilities to accommodate a new type of sensor, critically evaluating the literature for recent advancements, and in examining some available -albeit crude- flight data.

  10. Thickness determination in textile material design: dynamic modeling and numerical algorithms

    Science.gov (United States)

    Xu, Dinghua; Ge, Meibao

    2012-03-01

    Textile material design is of paramount importance in the study of functional clothing design. It is therefore important to determine the dynamic heat and moisture transfer characteristics in the human body-clothing-environment system, which directly determine the heat-moisture comfort level of the human body. Based on a model of dynamic heat and moisture transfer with condensation in porous fabric at low temperature, this paper presents a new inverse problem of textile thickness determination (IPTTD). Adopting the idea of the least-squares method, we formulate the IPTTD into a function minimization problem. By means of the finite-difference method, quasi-solution method and direct search method for one-dimensional minimization problems, we construct iterative algorithms of the approximated solution for the IPTTD. Numerical simulation results validate the formulation of the IPTTD and demonstrate the effectiveness of the proposed numerical algorithms.

  11. Friction and adhesion of hierarchical carbon nanotube structures for biomimetic dry adhesives: multiscale modeling.

    Science.gov (United States)

    Hu, Shihao; Jiang, Haodan; Xia, Zhenhai; Gao, Xiaosheng

    2010-09-01

    With unique hierarchical fibrillar structures on their feet, gecko lizards can walk on vertical walls or even ceilings. Recent experiments have shown that strong binding along the shear direction and easy lifting in the normal direction can be achieved by forming unidirectional carbon nanotube array with laterally distributed tips similar to gecko's feet. In this study, a multiscale modeling approach was developed to analyze friction and adhesion behaviors of this hierarchical fibrillar system. Vertically aligned carbon nanotube array with laterally distributed segments at the end was simulated by coarse grained molecular dynamics. The effects of the laterally distributed segments on friction and adhesion strengths were analyzed, and further adopted as cohesive laws used in finite element analysis at device scale. The results show that the laterally distributed segments play an essential role in achieving high force anisotropy between normal and shear directions in the adhesives. Finite element analysis reveals a new friction-enhanced adhesion mechanism of the carbon nanotube array, which also exists in gecko adhesive system. The multiscale modeling provides an approach to bridge the microlevel structures of the carbon nanotube array with its macrolevel adhesive behaviors, and the predictions from this modeling give an insight into the mechanisms of gecko-mimicking dry adhesives.

  12. Leukocyte Adhesion Deficiency (LAD)

    Science.gov (United States)

    ... Content Marketing Share this: Main Content Area Leukocyte Adhesion Deficiency (LAD) LAD is an immune deficiency in ... are slow to heal also may have LAD. Treatment and Research Doctors prescribe antibiotics to prevent and ...

  13. Determination of Mean Inner Potential by Electron Holography Along with Electron Dynamic Simulation

    Institute of Scientific and Technical Information of China (English)

    王岩国; 刘红荣; 杨奇斌; 张泽

    2003-01-01

    Off-axis electron holography in a field-emission-gun transmission electron microscope and electron dynamic simulation is used to determine the mean inner potential of copper. The phase shift of object wave versus specimen thickness is calculated up to 30 nm using electron dynamic formula, and the sample thickness is decided by match of the experimental and calculated phase shift. Based on the measured phase shift, the calculated mean inner potential of Cu is 21.2 V, which agrees with the reported values within the experimental error.

  14. Experimental determination of dynamic characteristics of the VentrAssist implantable rotary blood pump.

    Science.gov (United States)

    Chung, Michael K H; Zhang, Nong; Tansley, Geoff D; Qian, Yi

    2004-12-01

    The VentrAssist implantable rotary blood pump, intended for long-term ventricular assist, is under development and is currently being tested for its rotor-dynamic stability. The pump consists of a shaftless impeller, which also acts as the rotor of the brushless DC motor. The impeller remains passively suspended in the pump cavity by hydrodynamic forces, which result from the small clearances between the outside surfaces of the impeller and the pump cavity. These small clearances range from approximately 50 microm to 230 microm in size in the version of pump reported here. This article presents experimental investigation into the dynamic characteristics of the impeller-bearing-pump housing system of the rotary blood pump for increasing pump speeds at different flow rates. The pump was mounted on a suspension system consisting of a platform and springs, where the natural frequency and damping ratio for the suspension system were determined. Real-time measurements of the impeller's displacement were performed using Hall effect sensors. A vertical disturbance force was exerted onto the pump housing, causing the impeller to be displaced in vertical direction from its dynamic equilibrium position within the pump cavity. The impeller displacement was represented by a decaying sine wave, which indicated the impeller restoring to its equilibrium position. From the decaying sine wave the natural frequency and stiffness coefficient of the system were determined. Furthermore, the logarithmic decrement method was used to determine the damping ratio and eventually the damping coefficient of the system. Results indicate that stiffness and damping coefficients increased as flow rate and pump speed increased, representing an increase in stability with these changing conditions. However, pump speed had a greater influence on the stiffness and damping coefficients than flow rate did, which was evident through dynamic analysis. Overall the experimental method presented in this

  15. Management of adhesive capsulitis

    OpenAIRE

    Neviaser, Andrew

    2015-01-01

    Kristen L Stupay,1 Andrew S Neviaser2 1Tulane University School of Medicine, New Orleans, LA, USA; 2George Washington University Medical Faculty Associates, Washington, DC, USA Abstract: Adhesive capsulitis of the shoulder is a condition of capsular contracture that reduces both active and passive glenohumeral motion. The cause of adhesive capsulitis is not known but it is strongly associated with endocrine abnormalities such as diabetes. Diverse terminology and the absence of definitive cri...

  16. The Value of the Soluable Intercellular Adhesion Molecule-1 Levelsin Matermal Serum for Determination of Occult Chorioamnionitis in Premature Rupture of Membranes

    Institute of Scientific and Technical Information of China (English)

    邹丽; 张会军; 祝建芳; 朱剑文

    2004-01-01

    To compare the diagnostic value of soluble intercellular adhesion molecule 1 (sICAM-1)with that of c-reactive protein (CRP) for detecting chorioamnionitis (CAM) in serum of women with premature rupture of membranes (PROM), 55 pregnant women with PROM, including 18pregnant women with preterm premature rupture of membranes (PPROM) and 20 normal pregnant women at term (TPROM) were studied. Maternal serum were measured by Sandwish enzymelinked immunoabsorbent assay (ELISA) for sICAM. CAM was histologically confirmed after delivery. The results revealed that (1) maternal serum levels of sICAM-1 and CRP were significantly higher in women with PROM than those without it; (2) maternal serum levels of sICAM-1 and CRP were significantly higher in women with CAM than those without it; (3) serum levels of sICAM-1 in PPROM women were similar to those in TPROM women, whereas serum levels of CRP in PPROM women were significantly higher than those in TPROM women; (4) the sensitivity,specificity, positive predictive value, negative predictive value, Kappa index and area under receiver operating characteristic (ROC) curve of maternal serum sICAM-1 (cutoff 104.7 ng/ml) and CRP (cutoff 1.03 mg/dl) for diagnosing CAM were 100 %, 91.2 %, 87.5 %, 100 %, 0.20, 0.995and 81.0 %, 73.5 %, 65.4 %, 86.2 %, 0.13, 0. 811, respectively; (5) among the mild histological CAM group, severe histological CAM group and clinical CAM group, the difference in maternal serum levels of sICAM-1 were significantly (P<0. 001), with the order of concentration from high level to low level corresponding to the severity of CAM. It is concluded that maternal serum level of ICAM-1 is superior to that of CRP as biomarker for diagnosing intraamniotic infection in pregnant women with PROM.

  17. Bioinspired pressure actuated adhesive system

    NARCIS (Netherlands)

    Paretkar, D.R.; Kamperman, M.M.G.; Schneider, A.S.; Martina, D.; Creton, C.; Arzt, E.

    2011-01-01

    We developed a dry synthetic adhesive system inspired by gecko feet adhesion that can switch reversibly from adhesion to non-adhesion with applied pressure as external stimulus. Micropatterned polydimethylsiloxane (PDMS) surfaces with pillars of 30 µm length and 10 µm diameter were fabricated using

  18. Evaluation of polyaryl adhesives in elastomer-stainless steel joints

    Energy Technology Data Exchange (ETDEWEB)

    Miura, M.; Carciello, N.; Sugama, T.; Kukacka, L.E.

    1992-10-01

    Polyaryl thermoplastic adhesives (polyetheretherketone, PEEK, polyphenylene sulfide PPS, polyphenylethersulfone, PES) were evaluated for ability to bond elastomer to metal for use in geothermal environments. Strength of elastomer-to-metal joints adhesives blends (such as in drill pipe or casing protectors) were determined using peel tests. Parameters involved in making the joints were temperature, time and atmosphere, in addition to type of adhesive. Physical chemical analyses have aided endeavors to determine the cause of adhesion failure in the joint: differential thermal analyses, thermal gravimetric analyses, infrared spectroscopy and electron spectroscopy for chemical analysis. Tests showed that joints made of adhesive blends which contained greater than 50% PES survived simulated geothermal conditions (200C, water vapor pressure 200 psi) for weeks without significant decrease in peel strength. Chemical components of the adhesive appear to be highly stable under the conditions required to make the joints and in subsequent exposure to the simulated geothermal environment.

  19. Comparison of Two GC Methods for the Determination of Halogenated Hydrocarbons in Adhesives Method%两种GC法测定胶粘剂中卤代烃的方法比较研究

    Institute of Scientific and Technical Information of China (English)

    张惠; 冷中成; 王强

    2012-01-01

    The hydrogen flame ionization detector and electron capture detector were used to determinate the content of four kinds of halogenated hydrocarbons in adhesives method.By comparison,these two methods were simple,and had accurate results.But the sensitivity of these two methods,the detection limit,the linear range and practialrange were different.%采用氢火焰离子化检测器与电子捕获检测器两种方法对胶粘剂中四种卤代烃的含量进行测定。通过比较,两种方法操作简便,结果比较准确;但两种方法的灵敏度、检测限及线性范围有较大区别,实用范围不同。

  20. Study of Osteoclast Adhesion to Cortical Bone Surfaces: A Correlative Microscopy Approach for Concomitant Imaging of Cellular Dynamics and Surface Modifications.

    Science.gov (United States)

    Shemesh, Michal; Addadi, Sefi; Milstein, Yonat; Geiger, Benjamin; Addadi, Lia

    2016-06-22

    Bone remodeling relies on the coordinated functioning of osteoblasts, bone-forming cells, and osteoclasts, bone-resorbing cells. The effects of specific chemical and physical bone features on the osteoclast adhesive apparatus, the sealing zone ring, and their relation to resorption functionality are still not well-understood. We designed and implemented a correlative imaging method that enables monitoring of the same area of bone surface by time-lapse light microscopy, electron microscopy, and atomic force microscopy before, during, and after exposure to osteoclasts. We show that sealing zone rings preferentially develop around surface protrusions, with lateral dimensions of several micrometers, and ∼1 μm height. Direct overlay of sealing zone rings onto resorption pits on the bone surface shows that the rings adapt to pit morphology. The correlative procedure presented here is noninvasive and performed under ambient conditions, without the need for sample labeling. It can potentially be applied to study various aspects of cell-matrix interactions. PMID:26682493

  1. Dynamic capabilities for cooperation in Brazilian multinational and factors determining its management

    Directory of Open Access Journals (Sweden)

    Priscila Rezende da Costa

    2015-05-01

    Full Text Available In the context of emerging companies’ growth, current challenges depend on the local generation of product and process innovations, as well as dynamic capability to generate innovative solutions cooperatively and new globe business models. The objective of this study is to analyse the determining managerial factors for the dynamic capability of cooperation in Brazilian multinationals (BMNs. A survey was conducted with a sample of 60 BMNs, and a structured questionnaire and statistical tests with factorial analysis and Cronbach's alpha were used. The aggregate analysis of the results indicates that BMNs are going through a transitional process between the operational capability of cooperation and the capability for dynamic cooperation, which are relevant to the continuous adaptation of already-established cooperative management routines and the evaluation and incorporation of the relational capability of management practices that consider systemic flows, open innovation and integrate strategic intentionality into cooperative processes.

  2. Determination of dynamic performance of freight cars taking into account technical condition of side bearers

    Directory of Open Access Journals (Sweden)

    S.Myamlin

    2013-02-01

    Full Text Available Purpose. The railway transport plays an important role in social and economic life of the country and carries out the large containment of transportation activities. The transport industry should migrate towards innovation changes and increase its significance as an important transit subsystem on the way of renovation of both the infrastructure and the strategy of all transportation process components including the interaction with other transport modes. At present the life sets strategic challenges for the railway branch, and the basic goals among them are as follows: high-speed train traffic development, increase of the weight of freight trains, new rolling stock development etc. Due to the urgency of this subject, the researchers should cope with the task devoted to one of aspects of improving the freight transportation efficiency, namely to the study of effects of various factors and characteristics of technical conditions of the freight cars running gears (which are unavoidable to arise during operation on their basic dynamic indices. The deviations of technical conditions of running gears from the normal state of the wedge system of bogie swing suspension also play an important role among them. The purpose of the paper is to investigate the influence of different factors of the technical conditions of freight car running gears (size deviation in both the bearers and the wedge system during operation on their basic indices – coefficients of horizontal and vertical dynamics, vehicle body acceleration, frame strength, and derailment stability coefficient. Methodology. The study was conducted by numerical integration and mathematical modeling of the freight car dynamic loading using the software package “Dynamics of Rail Vehicles” (“DYNRAIL”. Findings. As a result of the research for freight car dynamic coefficients determination taking into account technical conditions of the side bearers, the dependencies of the basic freight cars

  3. Bond strength of adhesives to dentin contaminated with smoker's saliva.

    Science.gov (United States)

    Pinzon, Lilliam M; Oguri, Makoto; O'Keefe, Kathy; Dusevish, Vladimir; Spencer, Paulette; Powers, John M; Marshall, Grayson W

    2010-02-01

    The purpose of this study was to determine the effects of contamination with smoker's and non-smoker's saliva on the bond strength of resin composite to superficial dentin using different adhesive systems. The interfacial structure between the resin and dentin was evaluated for each treatment using environmental scanning electron microscopy (ESEM). Freshly extracted human molars were ground with 600-grit SiC paper to expose the superficial dentin. Adhesives [One-Up-Bond-F-Plus (OUFP) and Adper-Prompt-L-Pop (APLP)] and resin composite (TPHSpectrum) were bonded to the dentin (n = 8/group, 180 total specimens) under five surface conditions: control (adhesive applied following manufacturers' instructions); saliva, then 5-s air dry, then adhesive; adhesive, saliva, 5-s air dry; adhesive, saliva, 5-s water rinse, 5-s air dry (ASW group); and adhesive, saliva, 5-s water rinse, 5-s air dry, reapply adhesive (ASWA group). After storage in water at 37 degrees C for 24 h, the specimens were debonded under tension at a speed of 0.5 mm/min. ESEM photomicrographs of the dentin/adhesive interfaces were taken. Mean bond strength ranged from 8.1 to 24.1 MPa. Fisher's protected least significant difference (P = 0.05) intervals for critical adhesive, saliva, and surface condition differences were 1.3, 1.3, and 2.1 MPa, respectively. There were no significant differences in bond strength to dentin between contamination by smoker's and nonsmoker's saliva, but bond strengths were significantly different between adhesive systems, with OUFP twice as strong as APLP under almost all conditions. After adhesive application and contamination with either smoker's or nonsmoker's saliva followed by washing and reapplication of the adhesive (ASWA group), the bond strength of both adhesive systems was the same as that of the control group.

  4. Climate Effects and Feedback Structure Determining Weed Population Dynamics in a Long-Term Experiment

    Science.gov (United States)

    Lima, Mauricio; Navarrete, Luis; González-Andujar, José Luis

    2012-01-01

    Pest control is one of the areas in which population dynamic theory has been successfully applied to solve practical problems. However, the links between population dynamic theory and model construction have been less emphasized in the management and control of weed populations. Most management models of weed population dynamics have emphasized the role of the endogenous process, but the role of exogenous variables such as climate have been ignored in the study of weed populations and their management. Here, we use long-term data (22 years) on two annual weed species from a locality in Central Spain to determine the importance of endogenous and exogenous processes (local and large-scale climate factors). Our modeling study determined two different feedback structures and climate effects in the two weed species analyzed. While Descurainia sophia exhibited a second-order feedback and low climate influence, Veronica hederifolia was characterized by a first-order feedback structure and important effects from temperature and rainfall. Our results strongly suggest the importance of theoretical population dynamics in understanding plant population systems. Moreover, the use of this approach, discerning between the effect of exogenous and endogenous factors, can be fundamental to applying weed management practices in agricultural systems and to controlling invasive weedy species. This is a radical change from most approaches currently used to guide weed and invasive weedy species managements. PMID:22272362

  5. Climate effects and feedback structure determining weed population dynamics in a long-term experiment.

    Directory of Open Access Journals (Sweden)

    Mauricio Lima

    Full Text Available Pest control is one of the areas in which population dynamic theory has been successfully applied to solve practical problems. However, the links between population dynamic theory and model construction have been less emphasized in the management and control of weed populations. Most management models of weed population dynamics have emphasized the role of the endogenous process, but the role of exogenous variables such as climate have been ignored in the study of weed populations and their management. Here, we use long-term data (22 years on two annual weed species from a locality in Central Spain to determine the importance of endogenous and exogenous processes (local and large-scale climate factors. Our modeling study determined two different feedback structures and climate effects in the two weed species analyzed. While Descurainia sophia exhibited a second-order feedback and low climate influence, Veronica hederifolia was characterized by a first-order feedback structure and important effects from temperature and rainfall. Our results strongly suggest the importance of theoretical population dynamics in understanding plant population systems. Moreover, the use of this approach, discerning between the effect of exogenous and endogenous factors, can be fundamental to applying weed management practices in agricultural systems and to controlling invasive weedy species. This is a radical change from most approaches currently used to guide weed and invasive weedy species managements.

  6. Towards wafer scale inductive determination of magnetostatic and dynamic parameters of magnetic thin films and multilayers

    CERN Document Server

    Sievers, Sibylle; Nass, Paul; Serrano-Guisan, Santiago; Pasquale, Massimo; Schumacher, Hans Werner

    2013-01-01

    We investigate an inductive probe head suitable for non-invasive characterization of the magnetostatic and dynamic parameters of magnetic thin films and multilayers on the wafer scale. The probe is based on a planar waveguide with rearward high frequency connectors that can be brought in close contact to the wafer surface. Inductive characterization of the magnetic material is carried out by vector network analyzer ferromagnetic resonance. Analysis of the field dispersion of the resonance allows the determination of key material parameters such as the saturation magnetization MS or the effective damping parameter Meff. Three waveguide designs are tested. The broadband frequency response is characterized and the suitability for inductive determination of MS and Meff is compared. Integration of such probes in a wafer prober could in the future allow wafer scale in-line testing of magnetostatic and dynamic key material parameters of magnetic thin films and multilayers.

  7. Determination of Inelastic Mean Free Path by Electron Holography Along with Electron Dynamic Calculation

    Institute of Scientific and Technical Information of China (English)

    王岩国; 刘红荣; 杨奇斌; 张泽

    2003-01-01

    Off-axis electron holography in a field emission gun transmission-electron microscope and electron dynamic calculation are used to determine the absorption coefficient and inelastic mean free path (IMFP) of copper.Dependence of the phase shift of the exit electron wave on the specimen thickness is established by electron dynamic simulation. The established relationship makes it possible to determine the specimen thickness with the calculated phase shift by match of the phase shift measured in the reconstructed phase image. Based on the measured amplitudes in reconstructed exit electron wave and reference wave in the vacuum, the examined IMFP of electron with energy of 200kV in Cu is obtained to be 96nm.

  8. Dry adhesives with sensing features

    Science.gov (United States)

    Krahn, J.; Menon, C.

    2013-08-01

    Geckos are capable of detecting detachment of their feet. Inspired by this basic observation, a novel functional dry adhesive is proposed, which can be used to measure the instantaneous forces and torques acting on an adhesive pad. Such a novel sensing dry adhesive could potentially be used by climbing robots to quickly realize and respond appropriately to catastrophic detachment conditions. The proposed torque and force sensing dry adhesive was fabricated by mixing Carbon Black (CB) and Polydimethylsiloxane (PDMS) to form a functionalized adhesive with mushroom caps. The addition of CB to PDMS resulted in conductive PDMS which, when under compression, tension or torque, resulted in a change in the resistance across the adhesive patch terminals. The proposed design of the functionalized dry adhesive enables distinguishing an applied torque from a compressive force in a single adhesive pad. A model based on beam theory was used to predict the change in resistance across the terminals as either a torque or compressive force was applied to the adhesive patch. Under a compressive force, the sensing dry adhesive was capable of measuring compression stresses from 0.11 Pa to 20.9 kPa. The torque measured by the adhesive patch ranged from 2.6 to 10 mN m, at which point the dry adhesives became detached. The adhesive strength was 1.75 kPa under an applied preload of 1.65 kPa for an adhesive patch with an adhesive contact area of 7.07 cm2.

  9. Molecular dynamics simulation of peeling a DNA molecule on substrate

    Institute of Scientific and Technical Information of China (English)

    Xinghua Shi; Yong Kong; Yapu Zhao; Huajian Gao

    2005-01-01

    Molecular dynamics (MD) simulations are performed to study adhesion and peeling of a short fragment of single strand DNA (ssDNA) molecule from a graphite surface. The critical peel-off force is found to depend on both the peeling angle and the elasticity of ssDNA. For the short ssDNA strand under investigation, we show that the simulation results can be explained by a continuum model of an adhesive elastic band on substrate. The analysis suggests that it is often the peak value, rather than the mean value, of adhesion energy which determines the peeling of a nanoscale material.

  10. Dependence of polymer thin film adhesion energy on cohesive interactions between chains

    OpenAIRE

    Xia, Wenjie; Hsu, David; Keten, Sinan

    2014-01-01

    The adhesion of supported polymer thin films is predominantly influenced by the substrate-film interfacial properties. Utilizing steered molecular dynamics simulations, here we uncover that the cohesive noncovalent forces between polymer chains in the film also have a significant effect on the adhesive properties of supported film. We demonstrate that weaker interchain interactions, all else being the same, can induce higher adhesion energy within the interface. Three different adhesion regim...

  11. Determinants of house price dynamics. What can we learn from search engine data?

    OpenAIRE

    Oestmann, Marco; Bennöhr, Lars

    2015-01-01

    There is a broad literature on determinants of house prices, which received increasing attention in the aftermath of the subprime crisis. Additional to macroeconomic standard variables, there might be other hard to measure or even unobservable factors influencing real estate price dynamics. Using quarterly data, we try to increase the informational input of conventional models and capture such effects by including Google search engine query information into a set of standard fundamental varia...

  12. Dynamic karyotype evolution and unique sex determination systems in Leptidea wood white butterflies

    OpenAIRE

    VOLENÍKOVÁ, Anna

    2015-01-01

    Chromosomal rearrangements such as fusions and fissions play an important role in promoting and maintaining speciation. To study these phenomena, genome architecture of three cryptic species of Leptidea wood white butterflies was investigated by means of standard and molecular cytogenetics. High variability in chromosome number and localization of cytogenetic markers was revealed, suggesting dynamic karyotype evolution in these species. Moreover, unique sex-determination system with 3-4 W chr...

  13. A new dynamic formula for determining the coefficient of Smagorinsky model

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The most common method to determine the coefficient of Smagorinsky model now is to employ the Germano identity,however it is too complex and expensive in numerical calculation. In this letter we propose a new dynamic formula for determining the coefficient,which is based on the Kolmogorov equation of filtered velocity in physical space.The simplified formula is quite easy to implement in calculation.It is then verified in both homogeneous isotropic turbulence and wall-bounded turbulence by A Priori and A...

  14. Factors determining the diurnal dynamics of blooming of chosen plant species

    Directory of Open Access Journals (Sweden)

    Bożena Denisow

    2012-12-01

    Full Text Available The paper attempts to synthesize the determinants which may influence the diurnal rhythm of blooming. Additionally, I tried to explore and bring together topics that concern blooming and have always been considered separately because of their origin in different disciplines. The following species were included: Hydrangea arborescens L. subsp. discolor (Raf., H. paniculata Sieb., Viburnum opulus L., Chaenomeles japonica Lindl., Knautia arvensis L., Adonis vernalis L., Aster saggitifolius Willd., Taraxacum officinale L. Chelidonium majus L. The taxons were observed in Lublin (51008' - 51018' N and 21027' - 21041' E in the years 2001-2007. The blooming of species was determined at least for two vegetation seasons. During observations all flowers developed in one-hour intervals were counted. The diurnal dynamics of blooming differs among species and is modified by different endogenous and exogenous factors. The endogenous determinants of diurnal dynamics of blooming are morphological diversity of flowers (fertility or sterility within species or heterostyly. The different pattern of blooming succour different mechanisms which prevent self-pollination (Chaenomeles japonica Lindl., Knautia arvensis L.. The abiotic factors, such as day length and temperature during the vegetation season, influence the change in the process of diurnal dynamics of blooming (e. g. Taraxacum officinale, Chelidonium majus.

  15. Crack Propagation in a Toughened Epoxy Adhesive under Repeated Impacts

    Directory of Open Access Journals (Sweden)

    Ian A. Ashcroft

    2011-01-01

    Full Text Available Adhesives are being increasingly used in structural applications, especially in aerospace, automotive and naval structures, making their structural integrity an important issue. In-service loading histories of such structures usually contain low-energy impacts, repetition of which can significantly affect their performance. This paper deals with the behaviour of the toughened epoxy adhesive FM73 under repeated impacts, known as impact fatigue. Izod impact fatigue tests were performed on FM73 specimens in order to study the evolution of damage and to characterise this via measurable parameters, such as the maximum force and the contact time. A finite element model was developed to simulate the impact tests and this was used to calculate the dynamic strain energy release rate, which was compared with that determined using a simple analytical method. A relationship between the maximum dynamic strain energy release rate and impact fatigue crack growth rate was established that was used as the basis of an impact fatigue crack growth law.

  16. Friction and adhesion mediated by supramolecular host-guest complexes

    Science.gov (United States)

    Guerra, Roberto; Benassi, Andrea; Vanossi, Andrea; Ma, Ming; Urbakh, Michael

    The adhesive and frictional response of an AFM tip connected to a substrate through supramolecular host-guest complexes is investigated by dynamic Monte Carlo simulations. The variation of the pull-off force with the unloading rate recently observed in experiments is here unraveled by evidencing a simultaneous (progressive) break of the bonds at fast (slow) rates. The model reveals the origin of the observed plateaus in the retraction force as a function of tip-surface distance, showing that they ensue from the tip geometrical features. In lateral sliding, the model exhibits a wide range of dynamic behaviors ranging from smooth sliding to stick-slip at different velocities, with the average friction force determined by the characteristic formation/rupture rates of the complexes. In particular, it is shown that for some molecular complexes friction can become almost constant over a wide range of velocities. Also, we show the possibility to exploit ageing effect through slide-hold-slide experiments, in order to infer the characteristic formation rate. Finally, our model predicts a novel "anti-ageing" effect which is characterized by a decrease of static friction force with the hold time. Such effect is explained in terms of enhancement of adhesion during sliding, especially observed at high driving velocities.

  17. Friction and adhesion mediated by supramolecular host-guest complexes.

    Science.gov (United States)

    Guerra, Roberto; Benassi, Andrea; Vanossi, Andrea; Ma, Ming; Urbakh, Michael

    2016-04-01

    The adhesive and frictional response of an AFM tip connected to a substrate through supramolecular host-guest complexes is investigated by dynamic Monte Carlo simulations. Here, the variation of the pull-off force with the unloading rate recently observed in experiments is unraveled by evidencing simultaneous (progressive) breaking of the bonds at fast (slow) rates. The model reveals the origin of the observed plateaus in the retraction force as a function of the tip-surface distance, showing that they result from the tip geometrical features. In lateral sliding, the model exhibits a wide range of dynamic behaviors ranging from smooth sliding to stick-slip at different velocities, with the average friction force determined by the characteristic formation/rupture rates of the complexes. In particular, it is shown that for some molecular complexes friction can become almost constant over a wide range of velocities. Also, we show the possibility of exploiting the ageing effect through slide-hold-slide experiments, in order to infer the characteristic formation rate. Finally, our model predicts a novel "anti-ageing" effect which is characterized by a decrease of the static friction force with the hold time. Such an effect is explained in terms of enhancement of adhesion during sliding, especially observed at high driving velocities. PMID:26975343

  18. Magnetic field switchable dry adhesives.

    Science.gov (United States)

    Krahn, Jeffrey; Bovero, Enrico; Menon, Carlo

    2015-02-01

    A magnetic field controllable dry adhesive device is manufactured. The normal adhesion force can be increased or decreased depending on the presence of an applied magnetic field. If the magnetic field is present during the entire normal adhesion test cycle which includes both applying a preloading force and measuring the pulloff pressure, a decrease in adhesion is observed when compared to when there is no applied magnetic field. Similarly, if the magnetic field is present only during the preload portion of the normal adhesion test cycle, a decrease in adhesion is observed because of an increased stiffness of the magnetically controlled dry adhesive device. When the applied magnetic field is present during only the pulloff portion of the normal adhesion test cycle, either an increase or a decrease in normal adhesion is observed depending on the direction of the applied magnetic field.

  19. Fracture mechanics characterisation of medium-size adhesive joint specimens

    DEFF Research Database (Denmark)

    Sørensen, Bent F.; Jacobsen, T.K.

    2004-01-01

    Medium-size specimens (<2 m in length), consisting of two glass-fibre beams bonded together by an adhesive layer were tested in four point bending to determine their load carrying capacity. Specimens having different thickness were tested. Except for onespecimen, the cracking occurred as cracking...... along the adhesive layer; initially cracking occurred along the adhesive/laminate interface, but after some crack extension the cracking took place inside the laminate (for one specimen the later part of thecracking occurred unstably along the adhesive/ laminate interface). Crack bridging by fibres was...

  20. Determination of thermal/dynamic characteristics of lava flow from surface thermal measurements

    Science.gov (United States)

    Ismail-Zadeh, Alik; Melnik, Oleg; Korotkii, Alexander; Tsepelev, Igor; Kovtunov, Dmitry

    2016-04-01

    Rapid development of ground based thermal cameras, drones and satellite data allows getting repeated thermal images of the surface of the lava flow. Available instrumentation allows getting a large amount of data during a single lava flow eruption. These data require development of appropriate quantitative techniques to link subsurface dynamics with observations. We present a new approach to assimilation of thermal measurements at lava's surface to the bottom of the lava flow to determine lava's thermal and dynamic characteristics. Mathematically this problem is reduced to solving an inverse boundary problem. Namely, using known conditions at one part of the model boundary we determine the missing condition at the remaining part of the boundary. Using an adjoint method we develop a numerical approach to the mathematical problem based on the determination of the missing boundary condition and lava flow characteristics. Numerical results show that in the case of smooth input data lava temperature and velocity can be determined with a high accuracy. A noise imposed on the smooth input data results in a less accurate solution, but still acceptable below some noise level. The proposed approach to assimilate measured data brings an opportunity to estimate thermal budget of the lava flow.

  1. Nanoscale deicing by molecular dynamics simulation

    Science.gov (United States)

    Xiao, Senbo; He, Jianying; Zhang, Zhiliang

    2016-07-01

    Deicing is important to human activities in low-temperature circumstances, and is critical for combating the damage caused by excessive accumulation of ice. The aim of creating anti-icing materials, surfaces and applications relies on the understanding of fundamental nanoscale ice adhesion mechanics. Here in this study, we employ all-atom modeling and molecular dynamics simulation to investigate ice adhesion. We apply force to detach and shear nano-sized ice cubes for probing the determinants of atomistic adhesion mechanics, and at the same time investigate the mechanical effect of a sandwiched aqueous water layer between ice and substrates. We observe that high interfacial energy restricts ice mobility and increases both ice detaching and shearing stresses. We quantify up to a 60% decrease in ice adhesion strength by an aqueous water layer, and provide atomistic details that support previous experimental studies. Our results contribute quantitative comparison of nanoscale adhesion strength of ice on hydrophobic and hydrophilic surfaces, and supply for the first time theoretical references for understanding the mechanics at the atomistic origins of macroscale ice adhesion.Deicing is important to human activities in low-temperature circumstances, and is critical for combating the damage caused by excessive accumulation of ice. The aim of creating anti-icing materials, surfaces and applications relies on the understanding of fundamental nanoscale ice adhesion mechanics. Here in this study, we employ all-atom modeling and molecular dynamics simulation to investigate ice adhesion. We apply force to detach and shear nano-sized ice cubes for probing the determinants of atomistic adhesion mechanics, and at the same time investigate the mechanical effect of a sandwiched aqueous water layer between ice and substrates. We observe that high interfacial energy restricts ice mobility and increases both ice detaching and shearing stresses. We quantify up to a 60% decrease in ice

  2. Temperature Effects on Adhesive Bond Strengths and Modulus for Commonly Used Spacecraft Structural Adhesives

    Science.gov (United States)

    Ojeda, Cassandra E.; Oakes, Eric J.; Hill, Jennifer R.; Aldi, Dominic; Forsberg, Gustaf A.

    2011-01-01

    A study was performed to observe how changes in temperature and substrate material affected the strength and modulus of an adhesive bondline. Seven different adhesives commonly used in aerospace bonded structures were tested. Aluminum, titanium and Invar adherends were cleaned and primed, then bonded using the manufacturer's recommendations. Following surface preparation, the coupons were bonded with the adhesives. The single lap shear coupons were then pull tested per ASTM D 1002 Standard Test Method for Apparent Shear Strength of Single- Lap-Joint over a temperature range from -150 deg C up to +150 deg C. The ultimate strength was calculated and the resulting data were converted into B-basis design allowables. Average and Bbasis results were compared. Results obtained using aluminum adherends are reported. The effects of using different adherend materials and temperature were also studied and will be reported in a subsequent paper. Dynamic Mechanical Analysis (DMA) was used to study variations in adhesive modulus with temperature. This work resulted in a highly useful database for comparing adhesive performance over a wide range of temperatures, and has facilitated selection of the appropriate adhesive for spacecraft structure applications.

  3. Repeated origin and loss of adhesive toepads in geckos.

    Directory of Open Access Journals (Sweden)

    Tony Gamble

    Full Text Available Geckos are well known for their extraordinary clinging abilities and many species easily scale vertical or even inverted surfaces. This ability is enabled by a complex digital adhesive mechanism (adhesive toepads that employs van der Waals based adhesion, augmented by frictional forces. Numerous morphological traits and behaviors have evolved to facilitate deployment of the adhesive mechanism, maximize adhesive force and enable release from the substrate. The complex digital morphologies that result allow geckos to interact with their environment in a novel fashion quite differently from most other lizards. Details of toepad morphology suggest multiple gains and losses of the adhesive mechanism, but lack of a comprehensive phylogeny has hindered efforts to determine how frequently adhesive toepads have been gained and lost. Here we present a multigene phylogeny of geckos, including 107 of 118 recognized genera, and determine that adhesive toepads have been gained and lost multiple times, and remarkably, with approximately equal frequency. The most likely hypothesis suggests that adhesive toepads evolved 11 times and were lost nine times. The overall external morphology of the toepad is strikingly similar in many lineages in which it is independently derived, but lineage-specific differences are evident, particularly regarding internal anatomy, with unique morphological patterns defining each independent derivation.

  4. Cooling Rate Dependent Ellipsometry Measurements to Determine the Dynamics of Thin Glassy Films.

    Science.gov (United States)

    Glor, Ethan C; Fakhraai, Zahra

    2016-01-01

    This report aims to fully describe the experimental technique of using ellipsometry for cooling rate dependent Tg (CR-Tg) experiments. These measurements are simple high-throughput characterization experiments, which can determine the glass transition temperature (Tg), average dynamics, fragility and the expansion coefficient of the super-cooled liquid and glassy states for a variety of glassy materials. This technique allows for these parameters to be measured in a single experiment, while other methods must combine a variety of different techniques to investigate all of these properties. Measurements of dynamics close to Tg are particularly challenging. The advantage of cooling rate dependent Tg measurements over other methods which directly probe bulk and surface relaxation dynamics is that they are relatively quick and simple experiments, which do not utilize fluorophores or other complicated experimental techniques. Furthermore, this technique probes the average dynamics of technologically relevant thin films in temperature and relaxation time (τα) regimes relevant to the glass transition (τα > 100 sec). The limitation to using ellipsometry for cooling rate dependent Tg experiments is that it cannot probe relaxation times relevant to measurements of viscosity (τα film remains throughout the experiment. PMID:26863256

  5. Application of static and dynamic enclosures in determining DMS and OCS fluxes in Sphagnum peatlands

    Science.gov (United States)

    Demello, William Zamboni; Hines, Mark E.

    1992-01-01

    A static enclosure method was applied to determine the exchange of dimethyl sulfide (DMS) and OCS between the surface of Sphagnum peatlands and the atmosphere. Measurements were performed concurrently with dynamic enclosure measurements with S-free air used as sweep gas. DMS emission rates determined by both methods were comparable between 5 and 500 nmol/m(sup -2)h(sup -1). The dynamic method provided positive OCS flux rates (emission) for measurements performed at sites containing Sphagnum. Conversely, data from the static method indicated that OCS was consumed from the atmosphere. Measurements using both techniques at a site devoid of vegetation showed that peat is a source of both DMS and OCS. Results suggested that OCS is produced in surface peat but it is taken up from the atmosphere by Sphagnum mosses. However, the net effect of both processes is that OCS uptake exceeds emission. The dynamic enclosure technique is adequate to measure rates of emissions of S gases which are produced in peatlands but not consumed, as long as attention is paid to the rate of sweep flow.

  6. Determination of macroscopic transport coefficients of a dissipative particle dynamics solvent

    Science.gov (United States)

    Azarnykh, Dmitrii; Litvinov, Sergey; Bian, Xin; Adams, Nikolaus A.

    2016-01-01

    We present an approach to determine macroscopic transport coefficients of a dissipative particle dynamics (DPD) solvent. Shear viscosity, isothermal speed of sound, and bulk viscosity result from DPD-model input parameters and can be determined only a posteriori. For this reason approximate predictions of these quantities are desirable in order to set appropriate DPD input parameters. For the purpose of deriving an improved approximate prediction we analyze the autocorrelation of shear and longitudinal modes in Fourier space of a DPD solvent for Kolmogorov flow. We propose a fitting function with nonexponential properties which gives a good approximation to these autocorrelation functions. Given this fitting function we improve significantly the capability of a priori determination of macroscopic solvent transport coefficients in comparison to previously used exponential fitting functions.

  7. Determination of macroscopic transport coefficients of a dissipative particle dynamics solvent.

    Science.gov (United States)

    Azarnykh, Dmitrii; Litvinov, Sergey; Bian, Xin; Adams, Nikolaus A

    2016-01-01

    We present an approach to determine macroscopic transport coefficients of a dissipative particle dynamics (DPD) solvent. Shear viscosity, isothermal speed of sound, and bulk viscosity result from DPD-model input parameters and can be determined only a posteriori. For this reason approximate predictions of these quantities are desirable in order to set appropriate DPD input parameters. For the purpose of deriving an improved approximate prediction we analyze the autocorrelation of shear and longitudinal modes in Fourier space of a DPD solvent for Kolmogorov flow. We propose a fitting function with nonexponential properties which gives a good approximation to these autocorrelation functions. Given this fitting function we improve significantly the capability of a priori determination of macroscopic solvent transport coefficients in comparison to previously used exponential fitting functions. PMID:26871186

  8. Adhesive Contact in Animal: Morphology, Mechanism and Bio-Inspired Application

    Institute of Scientific and Technical Information of China (English)

    Aihong Ji; Longbao Han; Zhendong Dai

    2011-01-01

    Many animals possess adhesive pads on their feet,which are able to attach to various substrates while controlling adhesive forces during locomotion.This review article studies the morphology of adhesive devices in animals,and the physical mechanisms of wet adhesion and dry adhesion.The adhesive pads are either ‘smooth' or densely covered with special adhesive setae.Smooth pads adhere by wet adhesion,which is facilitated by fluid secreted from the pads,whereas hairy pads can adhere by dry adhesion or wet adhesion.Contact area,distance between pad and substrate,viscosity and surface tension of the liquid filling the gap between pad and substrate are the most important factors which determine the wet adhesion.Dry adhesion was found only in hairy pads,which occurs in geckos and spiders.It was demonstrated that van der Waals interaction is the dominant adhesive force in geckos' adhesion.The bio-inspired applications derived from adhesive pads are also reviewed.

  9. Tracheomalacia in adults with cystic fibrosis: determination of prevalence and severity with dynamic cine CT.

    LENUS (Irish Health Repository)

    McDermott, Shaunagh

    2012-02-01

    PURPOSE: To determine the prevalence and severity of tracheomalacia in adults with cystic fibrosis (CF) by using dynamic cine multidetector computed tomography (CT) and to correlate these findings with pulmonary function test (PFT) results and the severity of parenchymal lung disease. MATERIALS AND METHODS: In this institutional review board-approved HIPAA-compliant study, 40 patients with CF (22 men, 18 women; mean age, 28 years +\\/- 8 [standard deviation]; age range, 18-54 years) prospectively underwent PFTs, standard thin-section CT, and two dynamic cine multidetector CT acquisitions. Ten control subjects underwent dynamic cine multidetector CT. After standard thin-section CT was completed, dynamic cine multidetector CT was performed during a forced expiratory maneuver and during coughing. Dynamic cine multidetector CT images in nine patients were excluded. Maximal inspiratory, dynamic expiratory, and end-expiratory tracheal luminal areas were compared (Student t test) and correlated (Spearman rank) with PFT results and severity of parenchymal lung disease. RESULTS: Mean predicted forced expiratory volume in 1 second (FEV(1)) was 70.6% +\\/- 20.7, and mean Bhalla CT score was 41.8% +\\/- 13.6. In patients with CF, dynamic cine mean tracheal cross-sectional area reduction was 51.7% +\\/- 18.4 (range, 9%-89%) for forced expiratory maneuvers and 68.8% +\\/- 11.7 (range, 18%-88%) for coughing (P = .001). Tracheomalacia was demonstrated in 24 (69%) patients and no control subjects during forced expiratory maneuvers (P = .001) and in 10 (29%) patients and one (10%) control subject during coughing. For end-expiration images, mean tracheal luminal reduction was 16.1% +\\/- 14.0% (range, 0.0%-53.0%), with one patient demonstrating tracheal luminal reduction of more than 50%. There was no correlation between tracheal cross-sectional luminal reduction and either predicted FEV(1) or CT Bhalla score. CONCLUSION: Tracheomalacia depicted at dynamic cine multidetector CT is a

  10. What physiological changes and cerebral traces tell us about adhesion to fiction during theater-watching?

    Directory of Open Access Journals (Sweden)

    Marie-Noëlle Metz-Lutz

    2010-08-01

    Full Text Available Live theater is typically designed to alter the state of mind of the audience. Indeed, the perceptual inputs issuing from a live theatrical performance are intended to represent something else, and the actions, emphasised by the writing and staging, are the key prompting the adhesion of viewers to fiction, i.e. their belief that it is real. This phenomenon raises the issue of the cognitive processes governing access to a fictional reality during live theater and of their cerebral underpinnings. To get insight into the physiological substrates of adhesion we recreated the peculiar context of watching live drama in a functional magnetic resonance imaging experiment, with simultaneous recording of heart activity. The instants of adhesion were defined as the co-occurrence of theatrical events determined a priori by the stage director and the spectators’ offline reports of moments when fiction acted as reality. These data served to specify, for each spectator, individual fMRI time-series, used in a random-effect group analysis to define the pattern of brain response to theatrical events. The changes in this pattern related to subjects’ adhesion to fiction, were investigated using a region of interest analysis. The results showed that adhesion to theatrical events correlated with increased activity in the left BA47 and pSTS, together with a decrease in dynamic heart rate variability, leading us to discuss the hypothesis of subtle changes in the subjects’ state of awareness, enabling them to mentally dissociate physical and mental (drama-viewing experiences, to account for the phenomenon of adhesion to dramatic fiction.

  11. Switchable Adhesion in Vacuum Using Bio-Inspired Dry Adhesives

    OpenAIRE

    Purtov, Julia; Frensemeier, Mareike; Kroner, Elmar

    2015-01-01

    Suction based attachment systems for pick and place handling of fragile objects like glass plates or optical lenses are energy-consuming and noisy and fail at reduced air pressure, which is essential, e.g., in chemical and physical vapor deposition processes. Recently, an alternative approach toward reversible adhesion of sensitive objects based on bioinspired dry adhesive structures has emerged. There, the switching in adhesion is achieved by a reversible buckling of adhesive pillar structur...

  12. Shear adhesion strength of thermoplastic gecko-inspired synthetic adhesive exceeds material limits.

    Science.gov (United States)

    Gillies, Andrew G; Fearing, Ronald S

    2011-09-20

    Natural gecko array wearless dynamic friction has recently been reported for 30,000 cycles on a smooth substrate. Following these findings, stiff polymer gecko-inspired synthetic adhesives have been proposed for high-cycle applications such as robot feet. Here we examine the behavior of high-density polyethylene (HDPE) and polypropylene (PP) microfiber arrays during repeated cycles of engagement on a glass surface, with a normal preload of less than 40 kPa. We find that fiber arrays maintained 54% of the original shear stress of 300 kPa after 10,000 cycles, despite showing a marked plastic deformation of fiber tips. This deformation could be due to shear-induced plastic creep of the fiber tips from high adhesion forces, adhesive wear, or thermal effects. We hypothesize that a fundamental material limit has been reached for these fiber arrays and that future gecko synthetic adhesive designs must take into account the high adhesive forces generated to avoid damage. Although the synthetic material and natural gecko arrays have a similar elastic modulus, the synthetic material does not show the same wear-free dynamic friction as the gecko.

  13. Dynamics and determinants of dividend policy in Pakistan (evidence from Karachi stock exchange non-financial listed firms)

    OpenAIRE

    Ahmed, Hafeez; Javid, Attiya Yasmin

    2008-01-01

    This study examines the dynamics and determinants of dividend payout policy of 320 non-financial firms listed in Karachi Stock Exchange during the period of 2001 to 2006. It is also one of the very first examples which try to identify the potential dynamics and determinants of dividend payout in Pakistan by using the well established dividend models in context of emerging market. For dynamic equation we used the extended model of Lintner, Fama and Babiak and ‘Proposed’ model in dynamic se...

  14. Switchable Adhesion in Vacuum Using Bio-Inspired Dry Adhesives.

    Science.gov (United States)

    Purtov, Julia; Frensemeier, Mareike; Kroner, Elmar

    2015-11-01

    Suction based attachment systems for pick and place handling of fragile objects like glass plates or optical lenses are energy-consuming and noisy and fail at reduced air pressure, which is essential, e.g., in chemical and physical vapor deposition processes. Recently, an alternative approach toward reversible adhesion of sensitive objects based on bioinspired dry adhesive structures has emerged. There, the switching in adhesion is achieved by a reversible buckling of adhesive pillar structures. In this study, we demonstrate that these adhesives are capable of switching adhesion not only in ambient air conditions but also in vacuum. Our bioinspired patterned adhesive with an area of 1 cm(2) provided an adhesion force of 2.6 N ± 0.2 N in air, which was reduced to 1.9 N ± 0.2 N if measured in vacuum. Detachment was induced by buckling of the structures due to a high compressive preload and occurred, independent of air pressure, at approximately 0.9 N ± 0.1 N. The switch in adhesion was observed at a compressive preload between 5.6 and 6.0 N and was independent of air pressure. The difference between maximum adhesion force and adhesion force after buckling gives a reasonable window of operation for pick and place processes. High reversibility of the switching behavior is shown over 50 cycles in air and in vacuum, making the bioinspired switchable adhesive applicable for handling operations of fragile objects. PMID:26457864

  15. Switchable Adhesion in Vacuum Using Bio-Inspired Dry Adhesives.

    Science.gov (United States)

    Purtov, Julia; Frensemeier, Mareike; Kroner, Elmar

    2015-11-01

    Suction based attachment systems for pick and place handling of fragile objects like glass plates or optical lenses are energy-consuming and noisy and fail at reduced air pressure, which is essential, e.g., in chemical and physical vapor deposition processes. Recently, an alternative approach toward reversible adhesion of sensitive objects based on bioinspired dry adhesive structures has emerged. There, the switching in adhesion is achieved by a reversible buckling of adhesive pillar structures. In this study, we demonstrate that these adhesives are capable of switching adhesion not only in ambient air conditions but also in vacuum. Our bioinspired patterned adhesive with an area of 1 cm(2) provided an adhesion force of 2.6 N ± 0.2 N in air, which was reduced to 1.9 N ± 0.2 N if measured in vacuum. Detachment was induced by buckling of the structures due to a high compressive preload and occurred, independent of air pressure, at approximately 0.9 N ± 0.1 N. The switch in adhesion was observed at a compressive preload between 5.6 and 6.0 N and was independent of air pressure. The difference between maximum adhesion force and adhesion force after buckling gives a reasonable window of operation for pick and place processes. High reversibility of the switching behavior is shown over 50 cycles in air and in vacuum, making the bioinspired switchable adhesive applicable for handling operations of fragile objects.

  16. Multibody simulation of adhesion pili

    CERN Document Server

    Zakrisson, Johan; Servin, Martin; Axner, Ove; Lacoursiere, Claude; Andersson, Magnus

    2014-01-01

    We present a coarse grained rigid multibody model of a subunit assembled helix-like polymer, e.g., adhesion pili expressed by bacteria, that is capable of describing the polymers force-extension response. With building blocks representing individual subunits the model appropriately describes the complex behavior of pili expressed by the gram-negative uropathogenic Escherichia coli bacteria under the action of an external force. Numerical simulations show that the dynamics of the model, which include both the effects of unwinding and rewinding, are in good quantitative agreement with the characteristic force-extension response as observed experimentally for type 1 and P pili. By tuning the model, it is also possible to reproduce the force-extension response in the presence of anti-shaft antibodies, which dramatically changes the mechanical properties. Thus, the model and the results in this work give enhanced understanding of how a pilus unwinds under action of external forces and provide new perspective of th...

  17. Physiochemical properties of Caulobacter crescentus holdfast: a localized bacterial adhesive.

    Science.gov (United States)

    Berne, Cécile; Ma, Xiang; Licata, Nicholas A; Neves, Bernardo R A; Setayeshgar, Sima; Brun, Yves V; Dragnea, Bogdan

    2013-09-12

    To colonize surfaces, the bacterium Caulobacter crescentus employs a polar polysaccharide, the holdfast, located at the end of a thin, long stalk protruding from the cell body. Unlike many other bacteria which adhere through an extended extracellular polymeric network, the holdfast footprint area is tens of thousands times smaller than that of the total bacterium cross-sectional surface, making for some very demanding adhesion requirements. At present, the mechanism of holdfast adhesion remains poorly understood. We explore it here along three lines of investigation: (a) the impact of environmental conditions on holdfast binding affinity, (b) adhesion kinetics by dynamic force spectroscopy, and (c) kinetic modeling of the attachment process to interpret the observed time-dependence of the adhesion force at short and long time scales. A picture emerged in which discrete molecular units called adhesins are responsible for initial holdfast adhesion, by acting in a cooperative manner.

  18. Dynamics of Determining Motives in Choosing the Medical Profession by Medical Students

    Directory of Open Access Journals (Sweden)

    Kloktunova N.A.

    2013-06-01

    Full Text Available The purpose of the article is to study motivation of students of medical schools in choice of profession of the doctor and dynamics of defining motives in educational space of university. Material and methods: 497 students of the 1 st course took part in comparative research (356 students of medical faculty and 141 students of pediatric faculty and 382 students of the 6th course (270 students of medical faculty and 112 students of pediatric faculty of Saratov state medical university n.a. V. I. Razumovsky. In research methods of questioning and statistical data processing have been used. Results: The comparative analysis of the maximum and minimum values of the main types of motivation in professional field choice allowed to determine leading motives in medical students, and also to reveal their dynamics connected with various stages of professionalizing in the course of receiving medical education. Conclusion: Professional self-determination of the student of medical school has a multi-vector focus of structure of motivation. Determination by internal motives is supplemented with influence of external motivation, both positive, and negative value. In students of the 6th course indicators of motives included «Prestige», «Opportunity to help people», «Possibility of use of professional skills out of work».

  19. Adaptive SLICE method: an enhanced method to determine nonlinear dynamic respiratory system mechanics

    International Nuclear Information System (INIS)

    The objective of this paper is to introduce and evaluate the adaptive SLICE method (ASM) for continuous determination of intratidal nonlinear dynamic compliance and resistance. The tidal volume is subdivided into a series of volume intervals called slices. For each slice, one compliance and one resistance are calculated by applying a least-squares-fit method. The volume window (width) covered by each slice is determined based on the confidence interval of the parameter estimation. The method was compared to the original SLICE method and evaluated using simulation and animal data. The ASM was also challenged with separate analysis of dynamic compliance during inspiration. If the signal-to-noise ratio (SNR) in the respiratory data decreased from +∞ to 10 dB, the relative errors of compliance increased from 0.1% to 22% for the ASM and from 0.2% to 227% for the SLICE method. Fewer differences were found in resistance. When the SNR was larger than 40 dB, the ASM delivered over 40 parameter estimates (42.2 ± 1.3). When analyzing the compliance during inspiration separately, the estimates calculated with the ASM were more stable. The adaptive determination of slice bounds results in consistent and reliable parameter values. Online analysis of nonlinear respiratory mechanics will profit from such an adaptive selection of interval size. (paper)

  20. The interplay of cell–cell and cell–substrate adhesion in collective cell migration

    OpenAIRE

    Wang, Chenlu; Chowdhury, Sagar; Driscoll, Meghan; Parent, Carole A.; Gupta, S.K.; Losert, Wolfgang

    2014-01-01

    Collective cell migration often involves notable cell–cell and cell–substrate adhesions and highly coordinated motion of touching cells. We focus on the interplay between cell–substrate adhesion and cell–cell adhesion. We show that the loss of cell-surface contact does not significantly alter the dynamic pattern of protrusions and retractions of fast migrating amoeboid cells (Dictyostelium discoideum), but significantly changes their ability to adhere to other cells. Analysis of the dynamics ...

  1. A Novel Quantitative Mass Spectrometry Platform for Determining Protein O-GlcNAcylation Dynamics.

    Science.gov (United States)

    Wang, Xiaoshi; Yuan, Zuo-Fei; Fan, Jing; Karch, Kelly R; Ball, Lauren E; Denu, John M; Garcia, Benjamin A

    2016-07-01

    Over the past decades, protein O-GlcNAcylation has been found to play a fundamental role in cell cycle control, metabolism, transcriptional regulation, and cellular signaling. Nevertheless, quantitative approaches to determine in vivo GlcNAc dynamics at a large-scale are still not readily available. Here, we have developed an approach to isotopically label O-GlcNAc modifications on proteins by producing (13)C-labeled UDP-GlcNAc from (13)C6-glucose via the hexosamine biosynthetic pathway. This metabolic labeling was combined with quantitative mass spectrometry-based proteomics to determine protein O-GlcNAcylation turnover rates. First, an efficient enrichment method for O-GlcNAc peptides was developed with the use of phenylboronic acid solid-phase extraction and anhydrous DMSO. The near stoichiometry reaction between the diol of GlcNAc and boronic acid dramatically improved the enrichment efficiency. Additionally, our kinetic model for turnover rates integrates both metabolomic and proteomic data, which increase the accuracy of the turnover rate estimation. Other advantages of this metabolic labeling method include in vivo application, direct labeling of the O-GlcNAc sites and higher confidence for site identification. Concentrating only on nuclear localized GlcNAc modified proteins, we are able to identify 105 O-GlcNAc peptides on 42 proteins and determine turnover rates of 20 O-GlcNAc peptides from 14 proteins extracted from HeLa nuclei. In general, we found O-GlcNAcylation turnover rates are slower than those published for phosphorylation or acetylation. Nevertheless, the rates widely varied depending on both the protein and the residue modified. We believe this methodology can be broadly applied to reveal turnovers/dynamics of protein O-GlcNAcylation from different biological states and will provide more information on the significance of O-GlcNAcylation, enabling us to study the temporal dynamics of this critical modification for the first time. PMID:27114449

  2. Determination of Consumer Behaviour Dynamics Relating to Food Products: “Trakya Region Example”

    OpenAIRE

    I. H. Inan; Oraman, Y.; E. Yilmaz

    2009-01-01

    In this study, it has been determined the dynamics of consumer behaviours of individuals who live in rural and urban areas concerning food products and it analyses the effective factors on consumers food consumption choice in families, based in Trakya Region (Tekirdag, Edirne, Kırklareli). The study was conducted with a total of 770 households 385 people in towns and 385 people in rural areas, 770 people in total of which 385 was from rural areas, and 385 from urban areas.The effective factor...

  3. The electron beam cure of epoxy paste adhesives

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J.D. [Air Force Advanced Composites Program office, McClellan AFB, CA (United States); Janke, C.J. [Oak Ridge National Lab., TN (United States). Oak Ridge Centers for Manufacturing Technology; Lopata, V.J. [Atomic Energy of Canada Ltd., Pinawa, Manitoba (Canada). Whiteshell Labs.

    1998-07-01

    Recently developed epoxy paste adhesives were electron beam cured and experimentally explored to determine their suitability for use in an aerospace-quality aircraft component. There were two major goals for this program. The first was to determine whether the electron beam-curable past adhesives were capable of meeting the requirements of the US Air Force T-38 supersonic jet trainer composite windshield frame. The T-38 windshield frame`s arch is currently manufactured by bonding thin stainless steel plies using an aerospace-grade thermally-cured epoxy film adhesive. The second goal was to develop the lowest cost hand layup and debulk process that could be used to produce laminated steel plies with acceptable properties. The laminate properties examined to determine adhesive suitability include laminate mechanical and physical properties at room, adhesive tack, out-time capability, and the debulk requirements needed to achieve these properties. Eighteen past adhesives and four scrim cloths were experimentally examined using this criteria. One paste adhesive was found to have suitable characteristics in each of these categories and was later chosen for the manufacture of the T-38 windshield frame. This experimental study shows that by using low-cost debulk and layup processes, the electron beam-cured past adhesive mechanical and physical properties meet the specifications of the T-38 composite windshield frame.

  4. Analysis of the surface effects on adhesion in MEMS structures

    Science.gov (United States)

    Rusu, F.; Pustan, M.; Bîrleanu, C.; Müller, R.; Voicu, R.; Baracu, A.

    2015-12-01

    One of the main failure causes in microelectromechanical systems (MEMS) is stiction. Stiction is the adhesion of contacting surfaces due to surface forces. Adhesion force depends on the operating conditions and is influenced by the contact area. In this study, the adhesion force between MEMS materials and the AFM tips is analyzed using the spectroscopy in point mode of the AFM. The aim is to predict the stiction failure mode in MEMS. The investigated MEMS materials are silicon, polysilicon, platinum, aluminum, and gold. Three types of investigations were conducted. The first one aimed to determine the variation of the adhesion force with respect to the variation of the roughness. The roughness has a strong influence on the adhesion because the contact area between components increases if the roughness decreases. The second type of investigation aimed to determine the adhesion force in multiple points of each considered sample. The values obtained experimentally for the adhesion force were also validated using the JKR and DMT models. The third type of investigation was conducted with the purpose of determining the influence of the temperature on the adhesion force.

  5. Molecular mechanics of mussel adhesion proteins

    Science.gov (United States)

    Qin, Zhao; Buehler, Markus J.

    2014-01-01

    Mussel foot protein (mfp), a natural glue produced by marine mussel, is an intriguing material because of its superior ability for adhesion in various environments. For example, a very small amount of this material is sufficient to affix a mussel to a substrate in water, providing structural support under extreme forces caused by the dynamic effects of waves. Towards a more complete understanding of its strength and underwater workability, it is necessary to understand the microscropic mechanisms by which the protein structure interacts with various substrates. However, none of the mussel proteins' structure is known, preventing us from directly using atomistic modeling to probe their structural and mechanical properties. Here we use an advanced molecular sampling technique to identify the molecular structures of two mussel foot proteins (mfp-3 and mfp-5) and use those structures to study their mechanics of adhesion, which is then incorporated into a continuum model. We calculate the adhesion energy of the mussel foot protein on a silica substrate, compute the adhesion strength based on results obtained from molecular modeling, and compare with experimental data. Our results show good agreement with experimental measurements, which validates the multiscale model. We find that the molecular structure of the folded mussel foot protein (ultimately defined by its genetic sequence) favors strong adhesion to substrates, where L-3,4-dihydroxyphenylalanine (or DOPA) protein subunits work in a cooperative manner to enhance adhesion. Our experimental data suggests a peak attachment force of 0.4±0.1 N, which compares favorably with the prediction from the multiscale model of Fc=0.21-0.33 N. The principles learnt from those results could guide the fabrication of new interfacial materials (e.g. composites) to integrate organic with inorganic surfaces in an effective manner.

  6. Spiders Tune Glue Viscosity to Maximize Adhesion.

    Science.gov (United States)

    Amarpuri, Gaurav; Zhang, Ci; Diaz, Candido; Opell, Brent D; Blackledge, Todd A; Dhinojwala, Ali

    2015-11-24

    Adhesion in humid conditions is a fundamental challenge to both natural and synthetic adhesives. Yet, glue from most spider species becomes stickier as humidity increases. We find the adhesion of spider glue, from five diverse spider species, maximizes at very different humidities that matches their foraging habitats. By using high-speed imaging and spreading power law, we find that the glue viscosity varies over 5 orders of magnitude with humidity for each species, yet the viscosity at maximal adhesion for each species is nearly identical, 10(5)-10(6) cP. Many natural systems take advantage of viscosity to improve functional response, but spider glue's humidity responsiveness is a novel adaptation that makes the glue stickiest in each species' preferred habitat. This tuning is achieved by a combination of proteins and hygroscopic organic salts that determines water uptake in the glue. We therefore anticipate that manipulation of polymer-salts interaction to control viscosity can provide a simple mechanism to design humidity responsive smart adhesives.

  7. Pathogenesis of postoperative adhesion formation

    NARCIS (Netherlands)

    Hellebrekers, B.W.J.; Kooistra, T.

    2011-01-01

    Background: Current views on the pathogenesis of adhesion formation are based on the "classical concept of adhesion formation", namely that a reduction in peritoneal fibrinolytic activity following peritoneal trauma is of key importance in adhesion development. Methods: A non-systematic literature s

  8. Habitat heterogeneity determines climate impact on zooplankton community structure and dynamics.

    Directory of Open Access Journals (Sweden)

    Saskia A Otto

    Full Text Available Understanding and predicting species distribution in space and time and consequently community structure and dynamics is an important issue in ecology, and particularly in climate change research. A crucial factor determining the composition and dynamics of animal populations is habitat heterogeneity, i.e., the number of structural elements in a given locality. In the marine pelagic environment habitat heterogeneity is represented by the distribution of physical oceanographic parameters such as temperature, salinity and oxygen that are closely linked to atmospheric conditions. Little attention has been given, however, to the role of habitat heterogeneity in modulating the response of animal communities to external climate forcing. Here we investigate the long-term dynamics of Acartia spp., Temora longicornis, and Pseudocalanus acuspes, three dominant zooplankton species inhabiting different pelagic habitats in the Central Baltic Sea (CBS. We use the three copepods as indicator species for changes in the CBS zooplankton community and apply non-linear statistical modeling techniques to compare spatial population trends and to identify their drivers. We demonstrate that effects of climate variability and change depend strongly on species-specific habitat utilization, being more direct and pronounced at the upper water layer. We propose that the differential functional response to climate-related drivers in relation to strong habitat segregation is due to alterations of the species' environmental niches. We stress the importance of understanding how anticipated climate change will affect ecological niches and habitats in order to project spatio-temporal changes in species abundance and distribution.

  9. Work of adhesion and separation between soft elastomers

    Science.gov (United States)

    Lu, Nanshu

    2015-03-01

    The JKR (Johnson-Kendall-Roberts) method is widely used to measure the work of adhesion between soft materials. In this paper, the JKR theory is summarized and three dimensionless parameters are proposed to design a proper JKR experiment. The work of adhesion and the work of separation between two commonly used soft elastomers PDMS (Sylgard 184) and Ecoflex 0300 are obtained with the measured pull-in and pull-off forces using a dynamical mechanical analyzer (DMA). The effect of crosslinking density and solvent extraction are examined. It is found that the pull-in adhesion stays more or less constant for all contact pairs we measured. While the effect of crosslinking density is not significant for pristine PDMS, it is very obvious that the higher self-adhesion can be found in less crosslinked PDMS after solvent extraction. Such an effect is even more drastic for PDMS-to-Ecoflex adhesion. A unified adhesion mechanism is proposed to explain these complex adhesion behaviors. It is concluded that the chain-matrix interaction is the most effective adhesion mechanism compared to chain-chain or matrix-matrix interactions and the three interactions are exclusive to each other. This work is supported by the NSF CMMI award under Grant No. 1301335.

  10. PREFACE: Structure and dynamics determined by neutron and x-ray scattering Structure and dynamics determined by neutron and x-ray scattering

    Science.gov (United States)

    Müller-Buschbaum, Peter

    2011-06-01

    Neutron and x-ray scattering have emerged as powerful methods for the determination of structure and dynamics. Driven by emerging new, powerful neutron and synchrotron radiation sources, the continuous development of new instrumentation and novel scattering techniques gives rise to exciting possibilities. For example, in situ observations become possible via a high neutron or x-ray flux at the sample and, as a consequence, morphological transitions with small time constants can be detected. This special issue covers a broad range of different materials from soft to hard condensed matter. Hence, different material classes such as colloids, polymers, alloys, oxides and metals are addressed. The issue is dedicated to the 60th birthday of Professor Winfried Petry, scientific director of the Research Neutron Source Heinz Maier-Leibnitz (FRM-II), Germany, advisor at the physics department for the Bayerische Elite-Akademie, chair person of the Arbeitsgemeinschaft Metall- und Materialphysik of the German Physical Society (DPG) and a member of the professional council of the German Science Foundation (Deutsche Forschungsgemeinschaft, DFG). We would like to acknowledge and thank all contributors for their submissions, which made this special issue possible in the first place. Moreover, we would like to thank the staff at IOP Publishing for helping us with the administrative aspects and for coordinating the refereeing process, and Valeria Lauter for the beautiful cover artwork. Finally, to the readers, we hope that you find this special issue a valuable resource that provides insights into the present possibilities of neutron and x-ray scattering as powerful tools for the investigation of structure and dynamics. Structure and dynamics determined by neutron and x-ray scattering contents In situ studies of mass transport in liquid alloys by means of neutron radiography F Kargl, M Engelhardt, F Yang, H Weis, P Schmakat, B Schillinger, A Griesche and A Meyer Magnetic spin

  11. The role of self-determined motivation in job search: A dynamic approach.

    Science.gov (United States)

    da Motta Veiga, Serge P; Gabriel, Allison S

    2016-03-01

    Job search is a dynamic self-regulated process during which job seekers need to stay motivated to secure a job. However, past research has taken a relatively static approach to examining motivation during the job search, in addition to ignoring how the quality of one's motivation--ranging from autonomous to controlled--can influence job search processes. Adopting a within-person perspective, the current study extends self-determination theory (SDT) to the job search context to investigate (a) when autonomous and controlled motivations are more or less prevalent and (b) whether they influence job search effort through metacognitive strategies in differing ways depending upon the amount of time elapsed in the search. In a weekly study of new labor market entrants (Level-2 n = 149; Level-1 n = 691), results indicated that autonomous motivation decreased until the midpoint of the job search and then plateaued, whereas controlled motivation remained stable. Results also showed that autonomous motivation had a consistent, positive relation with metacognitive strategies, whereas the relation between controlled motivation and such strategies was negative early in the job search, but became positive as the job search progressed. Finally, the effects of motivation on job search effort occurred via metacognitive strategies differentially depending upon the time elapsed in the search. Combined, we provide a first glimpse into the dynamics of self-determined motivation on job search processes. PMID:26595757

  12. Determining the number of kanbans for dynamic production systems: An integrated methodology

    Directory of Open Access Journals (Sweden)

    Özlem Uzun Araz

    2016-08-01

    Full Text Available Just-in-time (JIT is a management philosophy that reduces the inventory levels and eliminates manufacturing wastes by producing only the right quantity at the right time. A kanban system is one of the key elements of JIT philosophy. Kanbans are used to authorize production and to control movement of materials in JIT systems. In Kanban systems, the efficiency of the manufacturing system depends on several factors such as number of kanbans, container size etc. Hence, determining the number of kanbans is a critical decision in Kanban systems. The aim of this study is to develop a methodology that can be used in order to determine the number of kanbans in a dynamic production environment. In this methodology, the changes in system state is monitored in real time manner, and the number of the kanbans are dynamically re-arranged. The proposed methodology integrates simulation, neural networks and Mamdani type fuzzy inference system. The methodology is modelled in simulation environment and applied on a hypothetic production system. We also performed several comparisons for different control policies to show the effectiveness of the proposed methodology.

  13. Polymerization contraction stress in dentin adhesives bonded to dentin and enamel

    NARCIS (Netherlands)

    M. Hashimoto; A.J. de Gee; A.J. Feilzer

    2008-01-01

    Objective In a previous study on of polymerization contraction stress determinations of adhesives bonded to dentin a continuous decline of stress was observed after the adhesives had been light-cured. The decline was ascribed to stress relief caused by diffusion into the adhesive layer of water and/

  14. A Dynamic Analysis on Determining of Housing Demand: A Comparison for Turkey, Hungary, and UK

    Institute of Scientific and Technical Information of China (English)

    Selahattin Bekmez; Ash Ozpolat

    2014-01-01

    Housing is both good and investment assets so that it plays an important role in the economy. Housing also can be characterized the most complex economic good because of its durability, heterogeneity, locational fixity, the possibility to raise loans against housing collateral, and the effect on well-developed secondary markets. On the other hand, income distribution, socio-economic justice, and regional disparities imply that housing market is an important concept for social and cultural transformation. In this study, the determinants of housing demand were compared for countries. These countries are selected according to economic situation: Turkey, Hungary, and United Kingdom. As a scope of this, the dynamic relationship between the housing demand and variables determining the housing demand in Turkey, Hungary, and UK has been analyzed. The model estimated uses quarterly data from January 2002 to January 2014. Building permits has been considered as housing demand. The other variables used for determining the housing demand are GDP, monetary aggregate, interest rate, and share prices. The long term relationship among variables has been analyzed with Vector Autoregressive Model (VAR) as impulse response and variance decomposition. The findings indicate that determining of housing demand changes according to economic and financial components such as government policies, mortgage system, consumer choice, tax, and subsidy in selected countries. All variables play an important role in housing demand, although the level of their impacts varies.

  15. Engineering bio-adhesive functions in an antimicrobial polymer multilayer

    International Nuclear Information System (INIS)

    Functionalization of a biomaterial surface with adhesive ligands is an effective way to promote specific cell adhesion. Ideally, biomaterial for applications in biomedical implants should simultaneously promote host cell adhesion and inhibit bacterial adhesion. Currently, little attention has been paid to the design of antimicrobial biomaterial with selective adhesiveness towards only targeted cells or tissues. In this study, the role of two typical adhesive ligands on the bioadhesion functions of a model antimicrobial film was elucidated. First, an adhesive ligand including an RGD peptide or collagen (CL) was chemically coupled to an antimicrobial polymeric multilayer composed of dextran sulfate (DS) and chitosan (CS). It was demonstrated that the density of RGD and CL immobilized on the DS/CS multilayer ranges between 4 to 137 ng cm−2 and 100 to 1000 ng cm−2, respectively. Then the effect of immobilized RGD or CL on both bacterial and fibroblast adhesion was investigated. By determining the density and morphology of adherent fibroblast on a DS/CS multilayer with or without an adhesive ligand, it was shown that RGD or CL effectively promoted fibroblast adhesion and proliferation in a concentration-dependent manner. Interestingly, the type of adhesive ligands imposed distinct effects in bacterial adhesion. Immobilized RGD did not enhance Staphylococcus aureus and Escherichia coli adhesion on DS/CS multilayers under all concentrations. In contrast, CL triggered significant S. aureus adhesion on DS/CS multilayers even at low surface concentration and when fibroblast adhesion was absent. Moreover, the detachment forces of individual S. aureus on CL coated DS/CS multilayers probed by atomic force microscopy (AFM) was 3 times and 20 times higher than that on the control substrate and on unmodified DS/CS multilayers, respectively. Interestingly, the lowest detachment force of E. coli was found on the CL coated DS/CS multilayers. This study demonstrated the

  16. Management of adhesive capsulitis

    Directory of Open Access Journals (Sweden)

    Stupay KL

    2015-08-01

    Full Text Available Kristen L Stupay,1 Andrew S Neviaser2 1Tulane University School of Medicine, New Orleans, LA, USA; 2George Washington University Medical Faculty Associates, Washington, DC, USA Abstract: Adhesive capsulitis of the shoulder is a condition of capsular contracture that reduces both active and passive glenohumeral motion. The cause of adhesive capsulitis is not known but it is strongly associated with endocrine abnormalities such as diabetes. Diverse terminology and the absence of definitive criteria for diagnosis make evaluating treatment modalities difficult. Many treatment methods have been reported, most with some success, but few have been proved to alter the natural course of this disease. Most afflicted patients will achieve acceptable shoulder function without surgery. Those who remain debilitated after 8–12 months are reasonable candidates for invasive treatments. Here, the various treatment methods and the data to support their use are reviewed. Keywords: frozen shoulder, stiff shoulder, periarthritis, painful shoulder 

  17. STRAW BASED PARTICLEBOARD BONDED WITH COMPOSITE ADHESIVES

    Directory of Open Access Journals (Sweden)

    Mingwei Di

    2011-02-01

    Full Text Available Environmentally friendly particleboard was prepared with wheat straw, an inexpensive material. The particleboard was produced by a mixing process, using a composite adhesive comprised of urea-formaldehyde (UF adhesives and EPU. The performance of the board was evaluated by measuring internal bonding strength (IB, thickness swelling, modulus of rupture (MOR, modulus of elasticity (MOE, and formaldehyde emission. The experimental results showed that maximum of dry and wet internal bonding strength, modulus of rupture, modulus of elasticity were 0.45MPa, 0.18MPa, 31.80MPa, and 5043MPa, respectively. The thickness swelling (TS2h and thickness swelling (TS24h were 3.9% and 10.7%, respectively. The composite adhesives and particleboards were measured by differential scanning calorimentry (DSC, dynamic mechanical analyzer (DMA, X-ray photoelectron spectroscopy (XPS and scanning electron microscope (SEM measurements. The results indicated that the composite adhesive of UF/EPU could contribute to excellent mechanical, thermal, and water-resistant properties of the wheat straw particleboards.

  18. INVESTIGATION OF THE STRUCTURE OF ADHESIVE JOINTS WITH A MICROTOMOGRAPHY METHOD

    Directory of Open Access Journals (Sweden)

    Chauzov K. V.

    2014-11-01

    Full Text Available The article provides a comparative analysis of two methods for assessing the structure of adhesive joint: optical microscopy and microtomography. Comparative analysis of the accuracy of measurement was shown; we have also built the graphs of the thickness of adhesive joint. The depth of penetration adhesive into the wood was determined. The structure of adhesive joint for two types of binders was studied

  19. Syndecans and cell adhesion

    DEFF Research Database (Denmark)

    Couchman, J R; Chen, L; Woods, A

    2001-01-01

    Now that transmembrane signaling through primary cell-matrix receptors, integrins, is being elucidated, attention is turning to how integrin-ligand interactions can be modulated. Syndecans are transmembrane proteoglycans implicated as coreceptors in a variety of physiological processes, including...... cell adhesion, migration, response to growth factors, development, and tumorigenesis. This review will describe this family of proteoglycans in terms of their structures and functions and their signaling in conjunction with integrins, and indicate areas for future research....

  20. How cells tiptoe on adhesive surfaces before sticking

    CERN Document Server

    Pierres, Anne; Touchard, Dominique; Bongrand, Pierre

    2008-01-01

    Cell membranes are studded with protrusions that were thoroughly analyzed with electron microscopy. However, the nanometer-scale three-dimensional motions generated by cell membranes to fit the topography of foreign surfaces and initiate adhesion remain poorly understood. Here, we describe the dynamics of surface deformations displayed by monocytic cells bumping against fibronectin-coated surfaces. We observed membrane undulations with typically 5 nm amplitude and 5-10 second lifetime. Cell membranes behaved as independent units of micrometer size. Cells detected the presence of foreign surfaces at 50 nm separation, resulting in time-dependent amplification of membrane undulations. Molecular contact then ensued with apparent cell-membrane separation of 30-40 nm, and this distance steadily decreased during the following tens of seconds. Contact maturation was associated with in-plane egress of bulky molecules and robust membrane fluctuations. Thus, membrane undulations may be the major determinant of cell sens...

  1. Localized Modeling of Biochemical and Flow Interactions during Cancer Cell Adhesion.

    Directory of Open Access Journals (Sweden)

    Julie Behr

    Full Text Available This work focuses on one component of a larger research effort to develop a simulation tool to model populations of flowing cells. Specifically, in this study a local model of the biochemical interactions between circulating melanoma tumor cells (TC and substrate adherent polymorphonuclear neutrophils (PMN is developed. This model provides realistic three-dimensional distributions of bond formation and attendant attraction and repulsion forces that are consistent with the time dependent Computational Fluid Dynamics (CFD framework of the full system model which accounts local pressure, shear and repulsion forces. The resulting full dynamics model enables exploration of TC adhesion to adherent PMNs, which is a known participating mechanism in melanoma cell metastasis. The model defines the adhesion molecules present on the TC and PMN cell surfaces, and calculates their interactions as the melanoma cell flows past the PMN. Biochemical rates of reactions between individual molecules are determined based on their local properties. The melanoma cell in the model expresses ICAM-1 molecules on its surface, and the PMN expresses the β-2 integrins LFA-1 and Mac-1. In this work the PMN is fixed to the substrate and is assumed fully rigid and of a prescribed shear-rate dependent shape obtained from micro-PIV experiments. The melanoma cell is transported with full six-degrees-of-freedom dynamics. Adhesion models, which represent the ability of molecules to bond and adhere the cells to each other, and repulsion models, which represent the various physical mechanisms of cellular repulsion, are incorporated with the CFD solver. All models are general enough to allow for future extensions, including arbitrary adhesion molecule types, and the ability to redefine the values of parameters to represent various cell types. The model presented in this study will be part of a clinical tool for development of personalized medical treatment programs.

  2. Adhesion Development and the Expression of Endothelial Nitric Oxide Synthase

    Directory of Open Access Journals (Sweden)

    David M. Svinarich

    2001-01-01

    Full Text Available Objective: This study was conducted to determine whether nitric oxide (NO, a potent vasodilator and inhibitor of thrombus formation, is involved in the formation and maintenance of adhesions.

  3. Staphylococcus epidermidis adhesion on hydrophobic and hydrophilic textured biomaterial surfaces.

    Science.gov (United States)

    Xu, Li-Chong; Siedlecki, Christopher A

    2014-06-01

    It is of great interest to use nano- or micro-structured surfaces to inhibit microbial adhesion and biofilm formation and thereby to prevent biomaterial-associated infection, without modification of the surface chemistry or bulk properties of the materials and without use of the drugs. Our previous study showed that a submicron textured polyurethane surface can inhibit staphylococcal bacterial adhesion and biofilm formation. To further understand the effect of the geometry of textures on bacterial adhesion as well as the underlying mechanism, in this study, submicron and micron textured polyurethane surfaces featuring ordered arrays of pillars were fabricated and modified to have different wettabilities. All the textured surfaces were originally hydrophobic and showed significant reductions in Staphylococcus epidermidis RP62A adhesion in phosphate buffered saline or 25% platelet poor plasma solutions under shear, as compared to smooth surfaces. After being subjected to an air glow discharge plasma treatment, all polyurethane surfaces were modified to hydrophilic, and reductions in bacterial adhesion on surfaces were subsequently found to be dependent on the size of the patterns. The submicron patterned surfaces reduced bacterial adhesion, while the micron patterned surfaces led to increased bacterial adhesion. The extracellular polymeric substances (EPS) from the S. epidermidis cell surfaces were extracted and purified, and were coated on a glass colloidal surface so that the adhesion force and separation energy in interactions of the EPS and the surface could be measured by colloidal probe atomic force microscopy. These results were consistent with the bacterial adhesion observations. Overall, the data suggest that the increased surface hydrophobicity and the decreased availability of the contact area contributes to a reduction in bacterial adhesion to the hydrophobic textured surfaces, while the availability of the contact area is the primary determinant factor

  4. Staphylococcus epidermidis adhesion on hydrophobic and hydrophilic textured biomaterial surfaces

    International Nuclear Information System (INIS)

    It is of great interest to use nano- or micro-structured surfaces to inhibit microbial adhesion and biofilm formation and thereby to prevent biomaterial-associated infection, without modification of the surface chemistry or bulk properties of the materials and without use of the drugs. Our previous study showed that a submicron textured polyurethane surface can inhibit staphylococcal bacterial adhesion and biofilm formation. To further understand the effect of the geometry of textures on bacterial adhesion as well as the underlying mechanism, in this study, submicron and micron textured polyurethane surfaces featuring ordered arrays of pillars were fabricated and modified to have different wettabilities. All the textured surfaces were originally hydrophobic and showed significant reductions in Staphylococcus epidermidis RP62A adhesion in phosphate buffered saline or 25% platelet poor plasma solutions under shear, as compared to smooth surfaces. After being subjected to an air glow discharge plasma treatment, all polyurethane surfaces were modified to hydrophilic, and reductions in bacterial adhesion on surfaces were subsequently found to be dependent on the size of the patterns. The submicron patterned surfaces reduced bacterial adhesion, while the micron patterned surfaces led to increased bacterial adhesion. The extracellular polymeric substances (EPS) from the S. epidermidis cell surfaces were extracted and purified, and were coated on a glass colloidal surface so that the adhesion force and separation energy in interactions of the EPS and the surface could be measured by colloidal probe atomic force microscopy. These results were consistent with the bacterial adhesion observations. Overall, the data suggest that the increased surface hydrophobicity and the decreased availability of the contact area contributes to a reduction in bacterial adhesion to the hydrophobic textured surfaces, while the availability of the contact area is the primary determinant factor

  5. Preparation of an Adhesive in Emulsion for Maxillofacial Prosthetic

    Science.gov (United States)

    Sánchez-García, Judith A.; Ortega, Alejandra; Barceló-Santana, Federico H.; Palacios-Alquisira, Joaquín

    2010-01-01

    Maxillofacial prostheses is a dental medicine specialty aimed at restoring anatomical facial defects caused by cancer, trauma or congenital malformations through an artificial device, which is commonly attached to the skin with the help of an adhesive. The purpose of our research was to develop a pressure-sensitive adhesive (PSA) based on acrylic monomers, characterizing and determining its drying kinetics, that is to say the time it takes to lose 50 to 90% of its moisture. The adhesive synthesis was realized by means of emulsion polymerization; the composition of formulations was: (AA-MMA-EA) and (AA-MMA-2EHA) with different molar ratios. The formulation based on (AA-MMA-2EHA) with 50 w% of solids, presented good adhesive properties such as tack, bond strength, and short drying time. We propose this formulation as a PSA, because it offers an alternative for systemically compromised patients, by less irritation compared to organic solvent-based adhesives. PMID:21152308

  6. Preparation of an Adhesive in Emulsion for Maxillofacial Prosthetic

    Directory of Open Access Journals (Sweden)

    Joaquín Palacios-Alquisira

    2010-10-01

    Full Text Available Maxillofacial prostheses is a dental medicine specialty aimed at restoring anatomical facial defects caused by cancer, trauma or congenital malformations through an artificial device, which is commonly attached to the skin with the help of an adhesive. The purpose of our research was to develop a pressure-sensitive adhesive (PSA based on acrylic monomers, characterizing and determining its drying kinetics, that is to say the time it takes to lose 50 to 90% of its moisture. The adhesive synthesis was realized by means of emulsion polymerization; the composition of formulations was: (AA‑MMA‑EA and (AA‑MMA‑2EHA with different molar ratios. The formulation based on (AA‑MMA‑2EHA with 50 w% of solids, presented good adhesive properties such as tack, bond strength, and short drying time. We propose this formulation as a PSA, because it offers an alternative for systemically compromised patients, by less irritation compared to organic solvent-based adhesives.

  7. Controlled release in transdermal pressure sensitive adhesives using organosilicate nanocomposites.

    Science.gov (United States)

    Shaikh, Sohel; Birdi, Anil; Qutubuddin, Syed; Lakatosh, Eric; Baskaran, Harihara

    2007-12-01

    Polydimethyl siloxane (PDMS) based pressure sensitive adhesives (PSA) incorporating organo-clays at different loadings were fabricated via solution casting. Partially exfoliated nanocomposites were obtained for the hydroxyl terminated PDMS in ethyl acetate solvent as determined by X-ray diffraction and atomic force microscopy. Drug release studies showed that the initial burst release was substantially reduced and the drug release could be controlled by the addition of organo-clay. Shear strength and shear adhesion failure temperature (SAFT) measurements indicated substantial improvement in adhesive properties of the PSA nanocomposite adhesives. Shear strength showed more than 200% improvement at the lower clay loadings and the SAFT increased by about 21% due to the reinforcement provided by the nano-dispersed clay platelets. It was found that by optimizing the level of the organosilicate additive to the polymer matrix, superior control over drug release kinetics and simultaneous improvements in adhesive properties could be attained for a transdermal PSA formulation. PMID:17786555

  8. Molecular simulations and lattice dynamics determination of Stillinger-Weber GaN thermal conductivity

    International Nuclear Information System (INIS)

    The bulk thermal conductivity of Stillinger-Weber (SW) wurtzite GaN in the [0001] direction at a temperature of 300 K is calculated using equilibrium molecular dynamics (EMD), non-equilibrium MD (NEMD), and lattice dynamics (LD) methods. While the NEMD method predicts a thermal conductivity of 166 ± 11 W/m·K, both the EMD and LD methods predict thermal conductivities that are an order of magnitude greater. We attribute the discrepancy to significant contributions to thermal conductivity from long-mean free path phonons. We propose that the Grüneisen parameter for low-frequency phonons is a good predictor of the severity of the size effects in NEMD thermal conductivity prediction. For weakly anharmonic crystals characterized by small Grüneisen parameters, accurate determination of thermal conductivity by NEMD is computationally impractical. The simulation results also indicate the GaN SW potential, which was originally developed for studying the atomic-level structure of dislocations, is not suitable for prediction of its thermal conductivity

  9. Dynamic light scattering and atomic force microscopy techniques for size determination of polyurethane nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Giehl Zanetti-Ramos, Betina [Laboratorio de Bioenergetica e Bioquimica de Macromoleculas, Departamento de Ciencias Farmaceuticas (Brazil)], E-mail: betinagzramos@pq.cnpq.br; Beddin Fritzen-Garcia, Mauricia [Laboratorio de Bioenergetica e Bioquimica de Macromoleculas, Departamento de Ciencias Farmaceuticas (Brazil); Schweitzer de Oliveira, Cristian; Avelino Pasa, Andre [Laboratorio de Filmes Finos e Superficie, Departamento de Fisica (Brazil); Soldi, Valdir [Grupo de Estudos em Materiais Polimericos, Departamento de Quimica, Universidade Federal de Santa Catarina, 88040-900, Florianopolis, SC (Brazil); Borsali, Redouane [Centre de Recherche sur les Macromolecules Vegetales CERMAV/CNRS, 38041 - Grenoble (France); Creczynski-Pasa, Tania Beatriz [Laboratorio de Bioenergetica e Bioquimica de Macromoleculas, Departamento de Ciencias Farmaceuticas (Brazil)

    2009-03-01

    Nanoparticles have applications in various industrial fields principally in drug delivery. Nowadays, there are several processes for manufacturing colloidal polymeric systems and methods of preparation as well as of characterization. In this work, Dynamic Light Scattering and Atomic Force Microscopy techniques were used to characterize polyurethane nanoparticles. The nanoparticles were prepared by miniemulsion technique. The lipophilic monomers, isophorone diisocyanate (IPDI) and natural triol, were emulsified in water containing surfactant. In some formulations the poly(ethylene glycol) was used as co-monomer to obtain the hydrophilic and pegylated nanoparticles. Polyurethane nanoparticles observed by atomic force microscopy (AFM) were spherical with diameter around 209 nm for nanoparticles prepared without PEG. From AFM imaging two populations of nanoparticles were observed in the formulation prepared with PEG (218 and 127 nm) while dynamic light scattering (DLS) measurements showed a monodisperse size distribution around 250 nm of diameters for both formulations. The polydispersity index of the formulations and the experimental procedures could influence the particle size determination with these techniques.

  10. Aggregate size and structure determination of nanomaterials in physiological media: importance of dynamic evolution

    International Nuclear Information System (INIS)

    Most in vitro nanotoxicological assays are performed after 24 h exposure. However, in determining size and shape effect of nanoparticles in toxicity assays, initial characterization data are generally used to describe experimental outcome. The dynamic size and structure of aggregates are typically ignored in these studies. This brief communication reports dynamic evolution of aggregation characteristics of gold nanoparticles. The study finds that gradual increase in aggregate size of gold nanospheres (AuNS) occurs up to 6 h duration; beyond this time period, the aggregation process deviates from gradual to a more abrupt behavior as large networks are formed. Results of the study also show that aggregated clusters possess unique structural conformation depending on nominal diameter of the nanoparticles. The differences in fractal dimensions of the AuNS samples likely occurred due to geometric differences, causing larger packing propensities for smaller sized particles. Both such observations can have profound influence on dosimetry for in vitro nanotoxicity analyses.Graphical Abstract

  11. Molecular simulations and lattice dynamics determination of Stillinger-Weber GaN thermal conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Zhi [Rensselaer Nanotechnology Center, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Jain, Ankit; McGaughey, Alan J. H., E-mail: mcgaughey@cmu.edu [Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Keblinski, Pawel, E-mail: keblip@rpi.edu [Rensselaer Nanotechnology Center, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

    2015-09-28

    The bulk thermal conductivity of Stillinger-Weber (SW) wurtzite GaN in the [0001] direction at a temperature of 300 K is calculated using equilibrium molecular dynamics (EMD), non-equilibrium MD (NEMD), and lattice dynamics (LD) methods. While the NEMD method predicts a thermal conductivity of 166 ± 11 W/m·K, both the EMD and LD methods predict thermal conductivities that are an order of magnitude greater. We attribute the discrepancy to significant contributions to thermal conductivity from long-mean free path phonons. We propose that the Grüneisen parameter for low-frequency phonons is a good predictor of the severity of the size effects in NEMD thermal conductivity prediction. For weakly anharmonic crystals characterized by small Grüneisen parameters, accurate determination of thermal conductivity by NEMD is computationally impractical. The simulation results also indicate the GaN SW potential, which was originally developed for studying the atomic-level structure of dislocations, is not suitable for prediction of its thermal conductivity.

  12. High frequency dynamics of BMG determined by synchrotron radiation: A microscopic picture

    Energy Technology Data Exchange (ETDEWEB)

    Serrano, Jorge, E-mail: jserrano@fa.upc.ed [Institucio Catalana de Recerca i Estudis Avancats (ICREA), Univ. Politecnica de Catalunya, Avda. del Canal Olimpic 15, Castelldefels (Spain); Dept. de Fisica Aplicada, EPSC, Univ. Politecnica de Catalunya, Avda. del Canal Olimpic 15, 08860 Castelldefels (Spain); Pineda, Eloi [Dept. de Fisica i Enginyeria Nuclear, ESAB, Univ. Politecnica de Catalunya, Avda. del Canal Olimpic 15, 08860 Castelldefels (Spain); Bruna, Pere [Dept. de Fisica Aplicada, EPSC, Univ. Politecnica de Catalunya, Avda. del Canal Olimpic 15, 08860 Castelldefels (Spain); Labrador, Ana [LLS, BM16-ESRF, BP 220, 38043 Grenoble Cedex 9 (France); Le Tacon, Mathieu; Krisch, Michael; Monaco, Giulio [European Synchrotron Radiation Facility, 6 Rue Jules Horowitz, BP 220, 38043 Grenoble Cedex 9 (France); Crespo, Daniel [Dept. de Fisica Aplicada, EPSC, Univ. Politecnica de Catalunya, Avda. del Canal Olimpic 15, 08860 Castelldefels (Spain)

    2010-04-16

    Mechanical properties are becoming the focus in research on bulk metallic glasses (BMG), as they are the limiting factor for structural applications. A wide range of experimental techniques gives complementary macroscopic data that are often difficult to correlate with the microscopic structural knowledge of the same materials. Recently, high resolution inelastic X-ray scattering (IXS) was applied to determine the high frequency dynamics of BMG [T. Scopigno, J.-B. Suck, R. Angelini, F. Albergamo, G. Ruocco, Phys. Rev. Lett. 96 (2006) 135501]. This technique offers a new approach to the mechanic properties helping to bridge the gap between the microscopic and the macroscopic picture. Here we will present results of IXS experiments on bulk metallic glasses with different fragility values, obtained at the European Synchrotron Radiation Facility (ESRF) in Grenoble (France).

  13. Role of the first coordination shell in determining the equilibrium structure and dynamics of simple liquids

    DEFF Research Database (Denmark)

    Toxværd, Søren; Dyre, J. C.

    2011-01-01

    . Lett. 103, 170601 (2009);10.1103/PhysRevLett.103.170601 J. Chem. Phys. 134, 214503 (2011)10.1063/1.3592709] . We present simulations of the standard Lennard-Jones liquid at several condensed-fluid state points, including a fairly low density state and a very high density state, as well as simulations......The traditional view that the physical properties of a simple liquid are determined primarily by its repulsive forces was recently challenged by Berthier and Tarjus, who showed that in some cases ignoring the attractions leads to large errors in the dynamics [L. Berthier and G. Tarjus, Phys. Rev...... are included in the simulations. What matters is whether or not interactions are included from all particles within the first coordination shell – the attractive forces can thus be ignored, but only at extremely high densities. The recognition of the importance of a local shell in condensed fluids...

  14. Molecular determinants of epidermal growth factor binding: a molecular dynamics study.

    Science.gov (United States)

    Sanders, Jeffrey M; Wampole, Matthew E; Thakur, Mathew L; Wickstrom, Eric

    2013-01-01

    The epidermal growth factor receptor (EGFR) is a member of the receptor tyrosine kinase family that plays a role in multiple cellular processes. Activation of EGFR requires binding of a ligand on the extracellular domain to promote conformational changes leading to dimerization and transphosphorylation of intracellular kinase domains. Seven ligands are known to bind EGFR with affinities ranging from sub-nanomolar to near micromolar dissociation constants. In the case of EGFR, distinct conformational states assumed upon binding a ligand is thought to be a determining factor in activation of a downstream signaling network. Previous biochemical studies suggest the existence of both low affinity and high affinity EGFR ligands. While these studies have identified functional effects of ligand binding, high-resolution structural data are lacking. To gain a better understanding of the molecular basis of EGFR binding affinities, we docked each EGFR ligand to the putative active state extracellular domain dimer and 25.0 ns molecular dynamics simulations were performed. MM-PBSA/GBSA are efficient computational approaches to approximate free energies of protein-protein interactions and decompose the free energy at the amino acid level. We applied these methods to the last 6.0 ns of each ligand-receptor simulation. MM-PBSA calculations were able to successfully rank all seven of the EGFR ligands based on the two affinity classes: EGF>HB-EGF>TGF-α>BTC>EPR>EPG>AR. Results from energy decomposition identified several interactions that are common among binding ligands. These findings reveal that while several residues are conserved among the EGFR ligand family, no single set of residues determines the affinity class. Instead we found heterogeneous sets of interactions that were driven primarily by electrostatic and Van der Waals forces. These results not only illustrate the complexity of EGFR dynamics but also pave the way for structure-based design of therapeutics targeting EGF

  15. Determination of the critical conditions for the initiation of dynamic recrystallization in boron microalloyed steels

    International Nuclear Information System (INIS)

    Research highlights: → Critical conditions for the DRX onset of boron microalloyed steels are determined. → σc and εc tend to increase as strain rate increases and temperature decreases. → σc and εc tend to decrease as boron content increases. → Critical ratios σc/σp and εc/εp remain fairly constant (∼0.82 and ∼0.53). → Boron additions promote solid solution softening and acceleration of the DRX onset. - Abstract: From the present research, the critical conditions associated with the onset of dynamic recrystallization (DRX) of hot deformed boron microalloyed steels were precisely determined based on changes in the strain hardening rate (θ) as a function of the flow stress. For this purpose, a low carbon steel microalloyed with four different amounts of boron (29, 49, 62 and 105 ppm) was deformed by uniaxial hot-compression tests at high temperature (950, 1000, 1050 and 1100 deg. C) and constant true strain rate (10-3, 10-2 and 10-1 s-1). Results indicate that the critical conditions for the initiation of dynamic recrystallization depend on the temperature and strain rate. In addition, both critical stress σc, and critical strain εc, were noticed to decrease as boron content increased. Such a behavior is attributed to a solute drag effect by boron atoms on the austenitic grain boundaries and also to a solid solution softening effect. The critical ratios σc/σp and εc/εp for all boron microalloyed steels remain fairly constant (∼0.82 and ∼0.53, respectively), such values are in agreement with those commonly reported for Al-killed, C-Mn, Nb, Nb-Ti, high carbon and stainless steels.

  16. Molecular determinants of epidermal growth factor binding: a molecular dynamics study.

    Directory of Open Access Journals (Sweden)

    Jeffrey M Sanders

    Full Text Available The epidermal growth factor receptor (EGFR is a member of the receptor tyrosine kinase family that plays a role in multiple cellular processes. Activation of EGFR requires binding of a ligand on the extracellular domain to promote conformational changes leading to dimerization and transphosphorylation of intracellular kinase domains. Seven ligands are known to bind EGFR with affinities ranging from sub-nanomolar to near micromolar dissociation constants. In the case of EGFR, distinct conformational states assumed upon binding a ligand is thought to be a determining factor in activation of a downstream signaling network. Previous biochemical studies suggest the existence of both low affinity and high affinity EGFR ligands. While these studies have identified functional effects of ligand binding, high-resolution structural data are lacking. To gain a better understanding of the molecular basis of EGFR binding affinities, we docked each EGFR ligand to the putative active state extracellular domain dimer and 25.0 ns molecular dynamics simulations were performed. MM-PBSA/GBSA are efficient computational approaches to approximate free energies of protein-protein interactions and decompose the free energy at the amino acid level. We applied these methods to the last 6.0 ns of each ligand-receptor simulation. MM-PBSA calculations were able to successfully rank all seven of the EGFR ligands based on the two affinity classes: EGF>HB-EGF>TGF-α>BTC>EPR>EPG>AR. Results from energy decomposition identified several interactions that are common among binding ligands. These findings reveal that while several residues are conserved among the EGFR ligand family, no single set of residues determines the affinity class. Instead we found heterogeneous sets of interactions that were driven primarily by electrostatic and Van der Waals forces. These results not only illustrate the complexity of EGFR dynamics but also pave the way for structure-based design of

  17. Nanoscale deicing by molecular dynamics simulation.

    Science.gov (United States)

    Xiao, Senbo; He, Jianying; Zhang, Zhiliang

    2016-08-14

    Deicing is important to human activities in low-temperature circumstances, and is critical for combating the damage caused by excessive accumulation of ice. The aim of creating anti-icing materials, surfaces and applications relies on the understanding of fundamental nanoscale ice adhesion mechanics. Here in this study, we employ all-atom modeling and molecular dynamics simulation to investigate ice adhesion. We apply force to detach and shear nano-sized ice cubes for probing the determinants of atomistic adhesion mechanics, and at the same time investigate the mechanical effect of a sandwiched aqueous water layer between ice and substrates. We observe that high interfacial energy restricts ice mobility and increases both ice detaching and shearing stresses. We quantify up to a 60% decrease in ice adhesion strength by an aqueous water layer, and provide atomistic details that support previous experimental studies. Our results contribute quantitative comparison of nanoscale adhesion strength of ice on hydrophobic and hydrophilic surfaces, and supply for the first time theoretical references for understanding the mechanics at the atomistic origins of macroscale ice adhesion.

  18. Application of Vehicle Dynamic Modeling in Uavs for Precise Determination of Exterior Orientation

    Science.gov (United States)

    Khaghani, M.; Skaloud, J.

    2016-06-01

    Advances in unmanned aerial vehicles (UAV) and especially micro aerial vehicle (MAV) technology together with increasing quality and decreasing price of imaging devices have resulted in growing use of MAVs in photogrammetry. The practicality of MAV mapping is seriously enhanced with the ability to determine parameters of exterior orientation (EO) with sufficient accuracy, in both absolute and relative senses (change of attitude between successive images). While differential carrier phase GNSS satisfies cm-level positioning accuracy, precise attitude determination is essential for both direct sensor orientation (DiSO) and integrated sensor orientation (ISO) in corridor mapping or in block configuration imaging over surfaces with low texture. Limited cost, size, and weight of MAVs represent limitations on quality of onboard navigation sensors and puts emphasis on exploiting full capacity of available resources. Typically short flying times (10-30 minutes) also limit the possibility of estimating and/or correcting factors such as sensor misalignment and poor attitude initialization of inertial navigation system (INS). This research aims at increasing the accuracy of attitude determination in both absolute and relative senses with no extra sensors onboard. In comparison to classical INS/GNSS setup, novel approach is presented here to integrated state estimation, in which vehicle dynamic model (VDM) is used as the main process model. Such system benefits from available information from autopilot and physical properties of the platform in enhancing performance of determination of trajectory and parameters of exterior orientation consequently. The navigation system employs a differential carrier phase GNSS receiver and a micro electro-mechanical system (MEMS) grade inertial measurement unit (IMU), together with MAV control input from autopilot. Monte-Carlo simulation has been performed on trajectories for typical corridor mapping and block imaging. Results reveal

  19. Physics of cell elasticity, shape and adhesion

    Science.gov (United States)

    Safran, S. A.; Gov, N.; Nicolas, A.; Schwarz, U. S.; Tlusty, T.

    2005-07-01

    We review recent theoretical work that analyzes experimental measurements of the shape, fluctuations and adhesion properties of biological cells. Particular emphasis is placed on the role of the cytoskeleton and cell elasticity and we contrast the shape and adhesion of elastic cells with fluid-filled vesicles. In red blood cells (RBC), the cytoskeleton consists of a two-dimensional network of spectrin proteins. Our analysis of the wavevector and frequency dependence of the fluctuation spectrum of RBC indicates that the spectrin network acts as a confining potential that reduces the fluctuations of the lipid bilayer membrane. However, since the cytoskeleton is only sparsely connected to the bilayer, one cannot regard the composite cytoskeleton-membrane as a polymerized object with a shear modulus. The sensitivity of RBC fluctuations and shapes to ATP concentration may reflect topological defects induced in the cytoskeleton network by ATP. The shapes of cells that adhere to a substrate are strongly determined by the cytoskeletal elasticity that can be varied experimentally by drugs that depolymerize the cytoskeleton. This leads to a tension-driven retraction of the cell body and a pearling instability of the resulting ray-like protrusions. Recent experiments have shown that adhering cells exert polarized forces on substrates. The interactions of such “force dipoles” in either bulk gels or on surfaces can be used to predict the nature of self-assembly of cell aggregates and may be important in the formation of artificial tissues. Finally, we note that cell adhesion strongly depends on the forces exerted on the adhesion sites by the tension of the cytoskeleton. The size and shape of the adhesion regions are strongly modified as the tension is varied and we present an elastic model that relates this tension to deformations that induce the recruitment of new molecules to the adhesion region. In all these examples, cell shape and adhesion differ from vesicle shape and

  20. Adhesion of PBO Fiber in Epoxy Composites

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The high mechanical and thermal performance of poly p-phenylene- 2, 6-benzobisoxazole ( PBO ) fiber provides great potential applications as reinforcement fibers for composites. A composite of PBO fiber and epoxy resin has excellent electrical insulation properties, therefore, it is considered to be the best choice for the reinforcement in high magnetic field coils for pulsed magnetic fields up to 100 T.However, poor adhesion between PBO fiber and matrix is found because of the chemically inactive and/or relatively smooth surface of the reinforcement fiber preventing efficient chemical bonding in the interface, which is a challenging issue to improve mechanical properties. Here, we report the surface modification of PBO fibers by ultraviolet (UV)irradiation, O2 and NH3 plasma, as well as acidic treatments. The interfacial adhesion strength values of all the treatments show the similar level as determined for aramid fibers by pull-out tests, a significant impact on fibermatrix-adhesion was not achieved. The surface free energy and roughness are increased for both sized and extracted fibers after plasma treatments together with maleic anhydride grafting. The sized fiber shows marginal improvement in adhesion strength and no change in fiber tensile strength because of the barrier effect of the finish.For the extracted fiber, different surface treatments either show no apparent effect or cause reduction in adhesion strength. Atomic force microscopy (AFM) topography analysis of the fracture surfaces proved adhesive failure at the fiber surface. The fiber surface roughness is increased and more surface flaws are induced, which could result in coarse interface structures when the treated fiber surface has no adequate wetting and functional groups. The adhesion failure is further confirmed by similar adhesion strength and compression shear strength values when the fiber was embedded in various epoxy resins with different temperature behavior. The tensile strength of fiber

  1. Adhesive tape exfoliation

    DEFF Research Database (Denmark)

    Bohr, Jakob

    2015-01-01

    cleaving of a single chunk of graphite. For both cases, parallel and serial exfoliation, it is investigated how many generations of cleavages are needed. An approximate model with the probability distribution expressed as a simple closed form is presented and compared with the simulations.......Single-crystal graphite can be cleaved by the use of an adhesive tape. This was also the initial route for obtaining graphene, a one-layer thick graphite slab. In this letter a few simple and fun considerations are presented in an attempt to shed some light on why this procedure is successful...

  2. Shock melting method to determine melting curve by molecular dynamics: Cu, Pd, and Al

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Zhong-Li, E-mail: zl.liu@163.com [College of Physics and Electric Information, Luoyang Normal University, Luoyang 471022 (China); Zhang, Xiu-Lu [Laboratory for Extreme Conditions Matter Properties, Southwest University of Science and Technology, 621010 Mianyang, Sichuan (China); Cai, Ling-Cang [Laboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, P.O. Box 919-102, 621900 Mianyang, Sichuan (China)

    2015-09-21

    A melting simulation method, the shock melting (SM) method, is proposed and proved to be able to determine the melting curves of materials accurately and efficiently. The SM method, which is based on the multi-scale shock technique, determines melting curves by preheating and/or prepressurizing materials before shock. This strategy was extensively verified using both classical and ab initio molecular dynamics (MD). First, the SM method yielded the same satisfactory melting curve of Cu with only 360 atoms using classical MD, compared to the results from the Z-method and the two-phase coexistence method. Then, it also produced a satisfactory melting curve of Pd with only 756 atoms. Finally, the SM method combined with ab initio MD cheaply achieved a good melting curve of Al with only 180 atoms, which agrees well with the experimental data and the calculated results from other methods. It turned out that the SM method is an alternative efficient method for calculating the melting curves of materials.

  3. An independent determination of Fomalhaut b's orbit and the dynamical effects on the outer dust belt

    CERN Document Server

    Beust, Hervé; Bonsor, Amy; Graham, J; Kalas, Paul; Lebreton, J; Lagrange, Anne-Marie; Ertel, Steve; Faramaz, Virginie; Thebault, Philippe

    2013-01-01

    The nearby star Fomalhaut harbours a cold, moderately eccentric dust belt with a sharp inner edge near 133 au. A low-mass, common proper motion companion (Fom b), was discovered near the inner edge and was identified as a planet candidate that could account for the belt morphology. However, the most recent orbit determination based on four epochs of astrometry over eight years reveals a highly eccentric orbit that appears to cross the belt in the sky plane projection. We perform here a full orbital determination based on the available astrometric data to independently validate the orbit estimates previously presented. Adopting our values for the orbital elements and their associated uncertainties, we then study the dynamical interaction between the planet and the dust ring, to check whether the proposed disk sculpting scenario by Fom b is plausible. We used a dedicated MCMC code to derive the statistical distributions of the orbital elements of Fom b. Then we used symplectic N-body integration to investigate ...

  4. Determination of bisphenol a in epoxy resin adhesives by high performance liquid chromatography%高效液相色谱法测定环氧树脂粘接剂中的双酚A

    Institute of Scientific and Technical Information of China (English)

    赖莺; 王鸿辉; 蔡鹭欣; 林睿; 葛秀秀; 林海霞; 黄龙

    2012-01-01

    建立了进出口建筑用环氧树脂粘接剂中双酚A的高效液相色谱-荧光检测法.对提取方法和色谱条件进行了研究,结果表明采用乙醇超声提取样品15min可获得良好的提取效果.以乙腈和水为流动相,采用梯度洗脱可消除样品的基质干扰.方法对环氧树脂粘接剂中双酚A的定量限(LOQ)为0.5 mg/kg,在2~4000 ng/mL范围内,线性相关系数为0.9996.在5个添加水平下回收率在89.1%~100.8%之间.%Bisphenol A in epoxy resin adhesives was determined by high performance liquid chromatography (HPLC) coupled with a fluorescence detector. The conditions of sample pretreatment and chromatographicparameters were studied. Results showed that the extraction of the BPA could reach a good performance with ethanol under ultrasonic extraction for 15 min. Matrix interference was eliminated by gradient elution with a acetonitrile and water the mobile phase. The quantification limit (LOQ) of BPA was 0. 5 mg/kg. The calibration curve was linear in the range of 2 -4000 ng/mL with a correlation coefficient of 0. 9996. The recoveries ranged from 89. L%to 100. 8% with five addition levels.

  5. Syndecan proteoglycans and cell adhesion

    DEFF Research Database (Denmark)

    Woods, A; Oh, E S; Couchman, J R

    1998-01-01

    It is now becoming clear that a family of transmembrane proteoglycans, the syndecans, have important roles in cell adhesion. They participate through binding of matrix ligand to their glycosaminoglycan chains, clustering, and the induction of signaling cascades to modify the internal microfilament...... organization. Syndecans can modulate the type of adhesive responses induced by other matrix ligand-receptor interactions, such as those involving the integrins, and so contribute to the control of cell morphology, adhesion and migration....

  6. Adhesion properties of gecko setae

    Science.gov (United States)

    Hill, Ginel; Peattie, Anne; Daniels, Roxanne; Full, Robert; Kenny, Thomas

    2005-03-01

    Millions of keratin hairs on gecko feet, called setae, act as a spectacular dry adhesive. Each seta branches into hundreds of smaller fibers that terminate in spatula-shaped ends. Morphological differences between the setae from different gecko species are suspected to affect both single-seta and whole-animal adhesion properties. Single-seta adhesive force measurements made using a MEMS piezoresistive cantilever capable of two-axis measurements are presented.

  7. Puerperal endometritis and intrauterine adhesions.

    Science.gov (United States)

    Polishuk, W Z; Anteby, S O; Weinstein, D

    1975-08-01

    The role of puerperal endometritis in intrauterine adhesion formation was studied by hysterography in 171 women who had cesarean sections. Of 28 patients who developed significant endometritis, only one developed intracervical adhesions. In the control group of 143 cases, there was also only one such case. Endometritis alone apparently does not play a significant role in intrauterine and endocervical adhesion formation. The possible role of placental fibroblasts in preventing endometrial regeneration is discussed. PMID:1158622

  8. Using Maximal Isometric Force to Determine the Optimal Load for Measuring Dynamic Muscle Power

    Science.gov (United States)

    Spiering, Barry A.; Lee, Stuart M. C.; Mulavara, Ajitkumar P.; Bentley, Jason R.; Nash, Roxanne E.; Sinka, Joseph; Bloomberg, Jacob J.

    2009-01-01

    Maximal power output occurs when subjects perform ballistic exercises using loads of 30-50% of one-repetition maximum (1-RM). However, performing 1-RM testing prior to power measurement requires considerable time, especially when testing involves multiple exercises. Maximal isometric force (MIF), which requires substantially less time to measure than 1-RM, might be an acceptable alternative for determining the optimal load for power testing. PURPOSE: To determine the optimal load based on MIF for maximizing dynamic power output during leg press and bench press exercises. METHODS: Twenty healthy volunteers (12 men and 8 women; mean +/- SD age: 31+/-6 y; body mass: 72 +/- 15 kg) performed isometric leg press and bench press movements, during which MIF was measured using force plates. Subsequently, subjects performed ballistic leg press and bench press exercises using loads corresponding to 20%, 30%, 40%, 50%, and 60% of MIF presented in randomized order. Maximal instantaneous power was calculated during the ballistic exercise tests using force plates and position transducers. Repeated-measures ANOVA and Fisher LSD post hoc tests were used to determine the load(s) that elicited maximal power output. RESULTS: For the leg press power test, six subjects were unable to be tested at 20% and 30% MIF because these loads were less than the lightest possible load (i.e., the weight of the unloaded leg press sled assembly [31.4 kg]). For the bench press power test, five subjects were unable to be tested at 20% MIF because these loads were less than the weight of the unloaded aluminum bar (i.e., 11.4 kg). Therefore, these loads were excluded from analysis. A trend (p = 0.07) for a main effect of load existed for the leg press exercise, indicating that the 40% MIF load tended to elicit greater power output than the 60% MIF load (effect size = 0.38). A significant (p . 0.05) main effect of load existed for the bench press exercise; post hoc analysis indicated that the effect of

  9. Simple method of dynamic Young’s modulus determination in lime and cement mortars

    Directory of Open Access Journals (Sweden)

    Rosell, J. R.

    2011-03-01

    Full Text Available The present work explains a simple method to determine the dynamic Young module (MOE by inducing a set of small mechanical perturbation to samples of lime and cement mortars and correlating the results obtained with results determined using other techniques and methods. The procedure described herein follows the instructions stated in the UNE-EN ISO 12680-1 standard for refractory products although in this study the instructions are applied to standardized RILEM 4x4x16 cm test samples made of lime and cement mortars. In addition, MOE determinations are obtained by using ultrasonic impulse velocity while static Young's modulus determinations are obtained by performing conventional bending tests. The ability of this procedure to correlate with results from other techniques, along with its simplicity, suggests that it can be widely adapted to determine the deformability of mortars under load using standardized samples.

    El presente trabajo muestra un método simple para determinar el módulo de Young dinámico (MOE a partir de pequeñas perturbaciones mecánicas producidas a probetas de mortero de cal y de cemento, correlacionando los resultados obtenidos con las correspondientes mediciones realizadas con otras técnicas. El procedimiento sigue básicamente las instrucciones fijadas en la norma UNE-EN ISO 12680-1 de productos refractarios, pero aplicándolo a probetas normalizadas RILEM 4x4x16 de morteros confeccionados con cal y cemento. Paralelamente se realizan determinaciones del MOE a partir de la velocidad de paso de impulsos ultrasónicos y determinaciones del módulo de Young estático a partir de ensayos de flexión convencionales. La simplicidad del método aplicado y la correlación de los resultados obtenidos con las variables medidas permiten concluir que esta metodología es de aplicación directa para determinar la deformabilidad bajo carga de los morteros a partir de probetas normalizadas.

  10. Experimental and Numerical Failure Analysis of Adhesive Composite Joints

    Directory of Open Access Journals (Sweden)

    Farhad Asgari Mehrabadi

    2012-01-01

    Full Text Available In the first section of this work, a suitable data reduction scheme is developed to measure the adhesive joints strain energy release rate under pure mode-I loading, and in the second section, three types of adhesive hybrid lap-joints, that is, Aluminum-GFRP (Glass Fiber Reinforced Plastic, GFRP-GFRP, and Steel-GFRP were employed in the determination of adhesive hybrid joints strengths and failures that occur at these assemblies under tension loading. To achieve the aims, Double Cantilever Beam (DCB was used to evaluate the fracture state under the mode-I loading (opening mode and also hybrid lap-joint was employed to investigate the failure load and strength of bonded joints. The finite-element study was carried out to understand the stress intensity factors in DCB test to account fracture toughness using J-integral method as a useful tool for predicting crack failures. In the case of hybrid lap-joint tests, a numerical modeling was also performed to determine the adhesive stress distribution and stress concentrations in the side of lap-joint. Results are discussed in terms of their relationship with adhesively bonded joints and thus can be used to develop appropriate approaches aimed at using adhesive bonding and extending the lives of adhesively bonded repairs for aerospace structures.

  11. Understanding Adhesion in Aluminum Processing via First Principles Simulation

    Science.gov (United States)

    Siegel Hector, Donald, Jr.; Adams, James

    2000-03-01

    One of the most common wear problems is adhesion and related adhesive metal transfer, in which one material transfers to the surface of another material along a heavily loaded interface. It is especially prevalent in the aluminum industry, for example, where thick ingots are subjected to massive loads in numerous hot and cold rolling processes that form the ingot into strip and plate products. One means through which adhesive metal transfer can be reduced is through the application of a ceramic tool coating that protects the tool surface for an extended period of time. The goal of this work is to use Density Functional Theory methods to determine the adhesive energies between aluminum alloys and relevant tool coating materials in order to aid in the selection of optimal coating materials. By analyzing the electronic structure of each interface one can determine the critical factors that control adhesion. Our study will yield the first reliable database on metal-ceramic adhesion energies, including the effects of the most common alloying elements. Along these lines, we discuss our recent calculations of the equilibrium structure, bonding, and adhesion energectics of two interface systems: Al(111)/α-Al_2O_3(0001) and Al(111)/WC(0001).

  12. On higher ground: how well can dynamic body acceleration determine speed in variable terrain?

    Directory of Open Access Journals (Sweden)

    Owen R Bidder

    Full Text Available INTRODUCTION: Animal travel speed is an ecologically significant parameter, with implications for the study of energetics and animal behaviour. It is also necessary for the calculation of animal paths by dead-reckoning. Dead-reckoning uses heading and speed to calculate an animal's path through its environment on a fine scale. It is often used in aquatic environments, where transmission telemetry is difficult. However, its adoption for tracking terrestrial animals is limited by our ability to measure speed accurately on a fine scale. Recently, tri-axial accelerometers have shown promise for estimating speed, but their accuracy appears affected by changes in substrate and surface gradients. The purpose of the present study was to evaluate four metrics of acceleration; Overall dynamic body acceleration (ODBA, vectorial dynamic body acceleration (VDBA, acceleration peak frequency and acceleration peak amplitude, as proxies for speed over hard, soft and inclined surfaces, using humans as a model species. RESULTS: A general linear model (GLM showed a significant difference in the relationships between the metrics and speed depending on substrate or surface gradient. When the data from all surface types were considered together, VeDBA had the highest coefficient of determination. CONCLUSIONS: All of the metrics showed some variation in their relationship with speed according to the surface type. This indicates that changes in the substrate or surface gradient during locomotion by animals would produce errors in speed estimates, and also in dead-reckoned tracks if they were calculated from speeds based entirely on a priori calibrations. However, we describe a method by which the relationship between acceleration metrics and speed can be corrected ad hoc, until tracks accord with periodic ground truthed positions, obtained via a secondary means (e.g. VHF or GPS telemetry. In this way, dead-reckoning provides a means to obtain fine scale movement data

  13. Mesoscopic Modeling of Blood Clotting: Coagulation Cascade and Platelets Adhesion

    Science.gov (United States)

    Yazdani, Alireza; Li, Zhen; Karniadakis, George

    2015-11-01

    The process of clot formation and growth at a site on a blood vessel wall involve a number of multi-scale simultaneous processes including: multiple chemical reactions in the coagulation cascade, species transport and flow. To model these processes we have incorporated advection-diffusion-reaction (ADR) of multiple species into an extended version of Dissipative Particle Dynamics (DPD) method which is considered as a coarse-grained Molecular Dynamics method. At the continuum level this is equivalent to the Navier-Stokes equation plus one advection-diffusion equation for each specie. The chemistry of clot formation is now understood to be determined by mechanisms involving reactions among many species in dilute solution, where reaction rate constants and species diffusion coefficients in plasma are known. The role of blood particulates, i.e. red cells and platelets, in the clotting process is studied by including them separately and together in the simulations. An agonist-induced platelet activation mechanism is presented, while platelets adhesive dynamics based on a stochastic bond formation/dissociation process is included in the model.

  14. Pressure sensitive adhesives from renewable resources

    OpenAIRE

    Maaßen, Wiebke

    2015-01-01

    Pressure-sensitive adhesives (PSAs) represent an important segment of the adhesives market. In this work, novel insights into the adhesive performance of bio-based pressure sensitive adhesives are presented. Three different homopolymers based on fatty acids derived from native vegetable oils as renewable feedstock were characterized in terms of their mechanical and adhesive properties.

  15. Improved Adhesion and Compliancy of Hierarchical Fibrillar Adhesives.

    Science.gov (United States)

    Li, Yasong; Gates, Byron D; Menon, Carlo

    2015-08-01

    The gecko relies on van der Waals forces to cling onto surfaces with a variety of topography and composition. The hierarchical fibrillar structures on their climbing feet, ranging from mesoscale to nanoscale, are hypothesized to be key elements for the animal to conquer both smooth and rough surfaces. An epoxy-based artificial hierarchical fibrillar adhesive was prepared to study the influence of the hierarchical structures on the properties of a dry adhesive. The presented experiments highlight the advantages of a hierarchical structure despite a reduction of overall density and aspect ratio of nanofibrils. In contrast to an adhesive containing only nanometer-size fibrils, the hierarchical fibrillar adhesives exhibited a higher adhesion force and better compliancy when tested on an identical substrate.

  16. Improved Adhesion and Compliancy of Hierarchical Fibrillar Adhesives.

    Science.gov (United States)

    Li, Yasong; Gates, Byron D; Menon, Carlo

    2015-08-01

    The gecko relies on van der Waals forces to cling onto surfaces with a variety of topography and composition. The hierarchical fibrillar structures on their climbing feet, ranging from mesoscale to nanoscale, are hypothesized to be key elements for the animal to conquer both smooth and rough surfaces. An epoxy-based artificial hierarchical fibrillar adhesive was prepared to study the influence of the hierarchical structures on the properties of a dry adhesive. The presented experiments highlight the advantages of a hierarchical structure despite a reduction of overall density and aspect ratio of nanofibrils. In contrast to an adhesive containing only nanometer-size fibrils, the hierarchical fibrillar adhesives exhibited a higher adhesion force and better compliancy when tested on an identical substrate. PMID:26167951

  17. Effect of adhesive thickness on adhesively bonded T-joint

    Science.gov (United States)

    Abdullah, A. R.; Afendi, Mohd; Majid, M. S. Abdul

    2013-12-01

    The aim of this work is to analyze the effect of adhesive thickness on tensile strength of adhesively bonded stainless steel T-joint. Specimens were made from SUS 304 Stainless Steel plate and SUS 304 Stainless Steel perforated plate. Four T-joint specimens with different adhesive thicknesses (0.5, 1.0, 1.5 and 2.0 mm) were made. Experiment result shows T-joint specimen with adhesive thickness of 1.0 mm yield highest maximum load. Identical T-joint specimen jointed by spot welding was also tested. Tensile test shows welded T-Joint had eight times higher tensile load than adhesively bonded T-joint. However, in low pressure application such as urea granulator chamber, high tensile strength is not mandatory. This work is useful for designer in fertilizer industry and others who are searching for alternative to spot welding.

  18. Determination of Activation Energy of Relaxation Events in Composite Solid Propellants by Dynamic Mechanical Analysis

    Directory of Open Access Journals (Sweden)

    B. K Bihari

    2014-03-01

    Full Text Available The shelf life of a composite solid propellant is one of the critical aspects for the usage of solid propellants. To assess the ageing behavior of the composite solid propellant, the activation energy is a key parameter. The activation energy is determined by analysis of visco-elastic response of the composite solid propellant when subjected to sinusoidal excitation. In the present study, dynamic mechanical analyzer was used to characterize six different types of propellants based on hydroxyl terminated polybutadiene, aluminium, ammonium perchlorate cured with toluene diisocyanate having burning rates varying from 5 mm/s to 25 mm/s at 7000 kPa. Each propellant sample was given a multi-frequency strain of 0.01 percent at three discrete frequencies (3.5 Hz, 11 Hz, 35 Hz in the temperature range -80 °C to + 80 °C. It was observed that all the propellants have shown two relaxation events (α- and β- transition in the temperature range -80 °C to +80 °C. The α-transition was observed between -66 °C and -51 °C and β-transition between 7 °C and 44 °C for the propellants studied. The activation energy for both transitions was determined by Arrhenius plot from dynamic properties measured at different frequencies and also by time temperature superposition principle using Williams-Landel-Ferry and Arrhenius temperature dependence equations. The data reveal that the activation energy corresponding to α-transition varies from 90 kJ/mol to 125 kJ/mol for R-value between 0.7 to 0.9 while for β-transition the values are from 75 kJ/mol to 92 kJ/mol. The activation energy corresponding to β-transition may be used to predict the useful life of solid propellant.Defence Science Journal, 2014, 64(2, pp. 173-178. DOI: http://dx.doi.org/10.14429/dsj.64.3818

  19. Cleaning properties of dry adhesives

    Institute of Scientific and Technical Information of China (English)

    J.; P.; DíAZ; TéLLEZ; D.; SAMEOTO; C.; MENON

    2010-01-01

    In this paper we present a study into the cleaning properties of synthetic dry adhesives. We have manufactured the adhesive micro-fibres through a low-cost, high yield fabrication method using Sylgard 184 Polydimethylsiloxane (PDMS) as the structural material. We deliberately contaminated the adhesive samples with different sized particles in the micro and macro scales and tested different cleaning methods for their efficacy with respect to each particle size. We investigated different cleaning methods, which included the use of wax moulding, vibration and pressure sensitive adhesives. For adhesion testing we used a custom system with a linear stage and a force sensor indenting a hemispherical probe into the adhesive surface and measuring the pull-off force. To characterize the cleaning efficacy we visually inspected each sample in a microscope and weighed the samples with a microgram-accuracy analytical balance. Results showed that the moulding method induced adhesion recovery in a greater percentage than the other cleaning methods and even helped with the recovery of collapsed posts in some cases. On the other hand pressure sensitive adhesives seem to have the upper hand with regards to certain particle sizes that can potentially pose problems with the moulding method.

  20. Towards determining appropriate hydrodynamic conditions for in vitro in vivo correlations using computational fluid dynamics.

    Science.gov (United States)

    D'Arcy, Deirdre M; Healy, Anne Marie; Corrigan, Owen I

    2009-06-28

    One of the earliest level A in vitro dissolution in vivo absorption correlations (IVIVCs) was established by Levy and co-workers in 1965 using a beaker dissolution apparatus Levy et al., 1965. In the current work, the computational fluid dynamics (CFD) package, Fluent((R)), was used to simulate the hydrodynamics within the Levy beaker apparatus and compare them to those within the paddle and basket apparatuses. In vitro velocity values relevant to in vivo dissolution, presented as apparent gastrointestinal fluid velocity (AGV) values, were calculated. The AGV values were estimated from IVIVCs of immediate release (IR) dosage forms in each apparatus and CFD simulations. The simulations from the Levy apparatus revealed complex hydrodynamics in the region of the stirrer blades, and radial inflow at the centre of the beaker base. The calculated AGV values ranged from 0.001 to 0.026ms(-1). In vitro fluid velocities should reflect in vivo dissolution rates affected by natural convection and gastrointestinal motility, in addition to local fluid velocity. The maximum CFD generated velocity at the base of the paddle apparatus at 20rpm was similar to the average maximum AGV value determined, suggesting use of agitation rates which are lower than those commonly used (e.g. 50rpm in the paddle apparatus) may be appropriate when attempting an IVIVC for IR dosage forms.

  1. Determination of arterial input function in dynamic susceptibility contrast MRI using group independent component analysis technique

    Science.gov (United States)

    Chen, Sharon; Liu, Ho-Ling; Yang, Yihong; Hsu, Yuan-Yu; Chuang, Keh-Shih

    2006-12-01

    Quantification of cerebral blood flow (CBF) with dynamic susceptibility contrast (DSC) magnetic resonance imaging (MRI) requires the determination of the arterial input function (AIF). The segmentation of surrounding tissue by manual selection is error-prone due to the partial volume artifacts. Independent component analysis (ICA) has the advantage in automatically decomposing the signals into interpretable components. Recently group ICA technique has been applied to fMRI study and showed reduced variance caused by motion artifact and noise. In this work, we investigated the feasibility and efficacy of the use of group ICA technique to extract the AIF. Both simulated and in vivo data were analyzed in this study. The simulation data of eight phantoms were generated using randomized lesion locations and time activity curves. The clinical data were obtained from spin-echo EPI MR scans performed in seven normal subjects. Group ICA technique was applied to analyze data through concatenating across seven subjects. The AIFs were calculated from the weighted average of the signals in the region selected by ICA. Preliminary results of this study showed that group ICA technique could not extract accurate AIF information from regions around the vessel. The mismatched location of vessels within the group reduced the benefits of group study.

  2. Dynamic-contrast-enhanced-MRI with extravasating contrast reagent: Rat cerebral glioma blood volume determination

    Science.gov (United States)

    Li, Xin; Rooney, William D.; Várallyay, Csanád G.; Gahramanov, Seymur; Muldoon, Leslie L.; Goodman, James A.; Tagge, Ian J.; Selzer, Audrey H.; Pike, Martin M.; Neuwelt, Edward A.; Springer, Charles S.

    2010-10-01

    The accurate mapping of the tumor blood volume (TBV) fraction ( vb) is a highly desired imaging biometric goal. It is commonly thought that achieving this is difficult, if not impossible, when small molecule contrast reagents (CRs) are used for the T1-weighted (Dynamic-Contrast-Enhanced) DCE-MRI technique. This is because angiogenic malignant tumor vessels allow facile CR extravasation. Here, a three-site equilibrium water exchange model is applied to DCE-MRI data from the cerebrally-implanted rat brain U87 glioma, a tumor exhibiting rapid CR extravasation. Analyses of segments of the (and the entire) DCE data time-course with this "shutter-speed" pharmacokinetic model, which admits finite water exchange kinetics, allow TBV estimation from the first-pass segment. Pairwise parameter determinances were tested with grid searches of 2D parametric error surfaces. Tumor blood volume ( vb), as well as ve (the extracellular, extravascular space volume fraction), and Ktrans (a CR extravasation rate measure) parametric maps are presented. The role of the Patlak Plot in DCE-MRI is also considered.

  3. Motivational dynamics of eating regulation: a self-determination theory perspective.

    Science.gov (United States)

    Verstuyf, Joke; Patrick, Heather; Vansteenkiste, Maarten; Teixeira, Pedro J

    2012-03-02

    Within Western society, many people have difficulties adequately regulating their eating behaviors and weight. Although the literature on eating regulation is vast, little attention has been given to motivational dynamics involved in eating regulation. Grounded in Self-Determination Theory (SDT), the present contribution aims to provide a motivational perspective on eating regulation. The role of satisfaction and thwarting of the basic psychological needs for autonomy, competence, and relatedness is introduced as a mechanism to (a) explain the etiology of body image concerns and disordered eating and (b) understand the optimal regulation of ongoing eating behavior for healthy weight maintenance. An overview of empirical studies on these two research lines is provided. In a final section, the potential relevance and value of SDT in relation to prevailing theoretical models in the domain of eating regulation is discussed. Although research on SDT in the domain of eating regulation is still in its early stages and more research is clearly needed, this review suggests that the SDT represents a promising framework to more thoroughly study and understand the motivational processes involved in eating regulation and associated problems.

  4. Determination of thermal properties pure ThO2 using classical molecular dynamics simulations

    Science.gov (United States)

    Ghosh, Partha S.; Kaur, Karamvir; Ali, K.; Arya, A.; Dey, G. K.

    2016-05-01

    This paper calculates lattice thermal expansion (LTE), thermal conductivity (TC) and melting temperature (MT) of ThO2 using classical molecular dynamic simulations. In this study we consider two set of interatomic potential consisting of Coulomb-Buckingham (Buck) and Coulomb-Buckingham-Morse-Many body (BMM) potential form. The MD calculated LTE of 10.29 × 10-6 and 10.61 × 10-6 K-1 using BMM and Buck potential, respectively, is slightly higher than the experimentally determined values (9.54 - 9.86 × 10-6 K-1). The MD calculated TC values in the high temperature range (600 to 1200 K) accords very well with the experimental measurements and at the low temperature range (300-500 K) our results are slightly different from experimental results as our presumption that the dominant mechanism for phonon scattering is the Umklapp process. The MD calculated MT of ThO2 using Buck and BMM potential model is 3662.5±12.5 K and 3812.5±12.5 K, respectively, and these values are in reasonable agreement with previous experimental values.

  5. Absolute densities, masses, and radii of the WASP-47 system determined dynamically

    CERN Document Server

    Almenara, J M; Bonfils, X; Udry, S

    2016-01-01

    We present a self-consistent modelling of the available light curve and radial velocity data of WASP-47 that takes into account the gravitational interactions between all known bodies in the system. The joint analysis of light curve and radial velocity data in a multi-planetary system allows deriving absolute densities, radii, and masses without the use of theoretical stellar models. For WASP-47 the precision is limited by the reduced dynamical information that is due to the short time span of the K2 light curve. We achieve a precision of around 22% for the radii of the star and the transiting planets, between 40% and 60% for their masses, and between 1.5% and 38% for their densities. All values agree with previously reported measurements. When theoretical stellar models are included, the system parameters are determined with a precision that exceeds that achieved by previous studies, thanks to the self-consistent modelling of light curve and radial velocity data.

  6. Determination of Consumer Behaviour Dynamics Relating to Food Products: “Trakya Region Example”

    Directory of Open Access Journals (Sweden)

    I.H. Inan

    2009-01-01

    Full Text Available In this study, it has been determined the dynamics of consumer behaviours of individuals who live in rural and urban areas concerning food products and it analyses the effective factors on consumers food consumption choice in families, based in Trakya Region (Tekirdag, Edirne, Kırklareli. The study was conducted with a total of 770 households 385 people in towns and 385 people in rural areas, 770 people in total of which 385 was from rural areas, and 385 from urban areas.The effective factors on consumer behaviour when purchasing food products have been evaluated by Multivariate Analysis of Variance (MANOVA and T-Test and Factor Analysis Methods in rural and urban areas in Trakya Region.This study indicates that families who live in urban areas of Trakya Region give more importance to food consumption compared to the ones living in rural areas. Also families living in urban and rural areas are concerned about “the Foot-and-Mouth Disease Mad Cow (BSE and Avian Influenza”.

  7. Motivational dynamics of eating regulation: a self-determination theory perspective

    Directory of Open Access Journals (Sweden)

    Verstuyf Joke

    2012-03-01

    Full Text Available Abstract Within Western society, many people have difficulties adequately regulating their eating behaviors and weight. Although the literature on eating regulation is vast, little attention has been given to motivational dynamics involved in eating regulation. Grounded in Self-Determination Theory (SDT, the present contribution aims to provide a motivational perspective on eating regulation. The role of satisfaction and thwarting of the basic psychological needs for autonomy, competence, and relatedness is introduced as a mechanism to (a explain the etiology of body image concerns and disordered eating and (b understand the optimal regulation of ongoing eating behavior for healthy weight maintenance. An overview of empirical studies on these two research lines is provided. In a final section, the potential relevance and value of SDT in relation to prevailing theoretical models in the domain of eating regulation is discussed. Although research on SDT in the domain of eating regulation is still in its early stages and more research is clearly needed, this review suggests that the SDT represents a promising framework to more thoroughly study and understand the motivational processes involved in eating regulation and associated problems.

  8. Vortices determine the dynamics of biodiversity in cyclical interactions with protection spillovers

    CERN Document Server

    Szolnoki, Attila

    2015-01-01

    If rock beats scissors and scissors beat paper, one might assume that rock beats paper too. But this is not the case for intransitive relationships that make up the famous rock-paper-scissors game. However, the sole presence of paper might prevent rock from beating scissors, simply because paper beats rock. This is the blueprint for the rock-paper-scissors game with protection spillovers, which has recently been introduced as a new paradigm for biodiversity in well-mixed microbial populations. Here we study the game in structured populations, demonstrating that protection spillovers give rise to spatial patterns that are impossible to observe in the classical rock-paper-scissors game. We show that the spatiotemporal dynamics of the system is determined by the density of stable vortices, which may ultimately transform to frozen states, to propagating waves, or to target waves with reversed propagation direction, depending further on the degree and type of randomness in the interactions among the species. If vo...

  9. Interaction between age and aerobic fitness in determining heart rate dynamics

    International Nuclear Information System (INIS)

    Heart rate variability (HRV) and phase-rectified signal averaging (PRSA) estimates of heart rate dynamics are diminished in older people compared with younger people. However, it is not fully elucidated whether these differences are related to age per se or to the concomitant influence of aerobic fitness. Aerobic fitness (peak oxygen uptake, gas exchange threshold, oxygen uptake kinetics, exercise economy) was assessed in 70 healthy adults (41 male) aged 18–57 years. Participants also underwent a 24 h, ambulatory ECG for the derivation of HRV and PRSA variables. HRV was most sensitive to age and aerobic fitness when measured during the morning period (6 am–12 pm). HRV and PRSA were both diminished with age and were higher in aerobically superior participants. The decline in HRV with age was predominantly attributable to age itself (33%), with aerobic fitness representing an additional modulating factor. The present study also provides tentative evidence that assessment of the influence of aerobic fitness should not rely on .VO2peak alone. These findings demonstrate that age per se is an important factor in determining HRV. However, given the clinical importance of diminished HRV and the immutable nature of aging, the potential significance of physical activity/training to enhance cardiac regulatory function should not be underestimated. (paper)

  10. Albedo of the South Pole on Mars Determined by Topographic Forcing of Atmosphere Dynamics

    Science.gov (United States)

    Colaprete, Anthony; Barnes, Jeffrey R.; Haberle, Robert M.; Hollingsworth, Jeffery L.; Kleffer, Hugh H.; Titus, Timothy N.

    2005-01-01

    The nature of the martian south polar cap has remained enigmatic since the first spacecraft observations. In particular, the presence of a perennial carbon dioxide ice cap, the formation of a vast area of black slab ice known as the Cryptic region and the asymmetric springtime retreat of the cap have eluded explanation. Here we present observations and climate modelling that indicate the south pole of Mars is characterized by two distinct regional climates that are the result of dynamical forcing by the largest southern impact basins, Argyre and Hellas. The style of surface frost deposition is controlled by these regional climates. In the cold and stormy conditions that exist poleward of 60 degrees S and extend 180 degrees in longitude west from the Mountains of Mitchel (about 30 degrees W), surface frost accumulation is dominated by precipitation. In the opposite hemisphere, the polar atmosphere is relatively warm and clear and frost accumulation is dominated by direct vapour deposition. It is the differences in these deposition styles that determine the cap albedo.

  11. Transcription closed and open complex dynamics studies reveal balance between genetic determinants and co-factors.

    Science.gov (United States)

    Sala, Adrien; Shoaib, Muhammad; Anufrieva, Olga; Mutharasu, Gnanavel; Jahan Hoque, Rawnak; Yli-Harja, Olli; Kandhavelu, Meenakshisundaram

    2015-05-19

    In E. coli, promoter closed and open complexes are key steps in transcription initiation, where magnesium-dependent RNA polymerase catalyzes RNA synthesis. However, the exact mechanism of initiation remains to be fully elucidated. Here, using single mRNA detection and dual reporter studies, we show that increased intracellular magnesium concentration affects Plac initiation complex formation resulting in a highly dynamic process over the cell growth phases. Mg2+ regulates transcription transition, which modulates bimodality of mRNA distribution in the exponential phase. We reveal that Mg2+ regulates the size and frequency of the mRNA burst by changing the open complex duration. Moreover, increasing magnesium concentration leads to higher intrinsic and extrinsic noise in the exponential phase. RNAP-Mg2+ interaction simulation reveals critical movements creating a shorter contact distance between aspartic acid residues and Nucleotide Triphosphate residues and increasing electrostatic charges in the active site. Our findings provide unique biophysical insights into the balanced mechanism of genetic determinants and magnesium ion in transcription initiation regulation during cell growth.

  12. Mitigation of biological adhesion to aircraft leading edge surfaces

    OpenAIRE

    Kok, Mariana

    2014-01-01

    Contamination caused by insects on aircraft leading edge surfaces can result in premature transition of the boundary layer, leading to an increase in skin friction drag and fuel consumption. Consequently, the use of novel low surface energy coatings to mitigate insect residue adhesion was investigated. In order to determine the effect of surface characteristics on insect residue adhesion a range of surfaces, from superhydrophobic to hydrophilic, were evaluated. Surfaces were characterized in ...

  13. Cell Adhesion on Polycaprolactone Modified by Plasma Treatment

    OpenAIRE

    Nina Recek; Matic Resnik; Helena Motaln; Tamara Lah-Turnšek; Robin Augustine; Nandakumar Kalarikkal; Sabu Thomas; Miran Mozetič

    2016-01-01

    We have investigated the influence of various plasma treatments of electrospun polycaprolactone (PCL) scaffolds on the adhesion and proliferation of human umbilical endothelial cells (HUVEC). The PCL scaffolds were treated in plasmas created in O2, NH3 or SO2 gas at identical conditions. Surface functionalization of plasma-treated samples was determined using X-ray photoelectron spectroscopy. Cell adhesion and morphology were investigated by scanning electron microscopy and the influence of p...

  14. [Retention of adhesive bridges].

    Science.gov (United States)

    Raes, F; De Boever, J

    1994-04-01

    Since the development of adhesive bridges in the early seventies, the retention and therefore the durability of these bridges has been tremendously improved. Conditioning of the non-precious metal by silanisation, careful acid etching of the enamel and the use of the appropriate composite resin are of prime importance. Furthermore, the meticulous preparation with enough interproximal embrace, occlusal rests, interocclusal clearance and cingulum stops is equally important. Including more teeth in the design does not necessarily lead to an improved retention. Besides the material and technical aspects, the whole clinical procedure needs much attention. The retention does not depend on one single factor, but on the precision of all the necessary clinical steps and on a well-defined selection of the material. In this way a five-year survival rate of close to 80% can be obtained. PMID:11830965

  15. Hyaluronan-mediated cellular adhesion

    Science.gov (United States)

    Curtis, Jennifer

    2005-03-01

    Many cells surround themselves with a cushioning halo of polysaccharides that is further strengthened and organized by proteins. In fibroblasts and chrondrocytes, the primary component of this pericellular matrix is hyaluronan, a large linear polyanion. Hyaluronan production is linked to a variety of disease, developmental, and physiological processes. Cells manipulate the concentration of hyaluronan and hyaluronan receptors for numerous activities including modulation of cell adhesion, cell motility, and differentiation. Recent investigations by identify hyaluronan's role in mediating early-stage cell adhesion. An open question is how the cell removes the 0.5-10 micron thick pericellular matrix to allow for further mature adhesion events requiring nanometer scale separations. In this investigation, holographic optical tweezers are used to study the adhesion and viscoelastic properties of chondrocytes' pericellular matrix. Ultimately, we aim to shed further light on the spatial and temporal details of the dramatic transition from micron to nanometer gaps between the cell and its adhesive substrate.

  16. Application Study on the Dynamic Prediction Model for Determining the Mining Subsidence

    Directory of Open Access Journals (Sweden)

    H.F. HU

    2016-04-01

    Full Text Available The movement and deformation of the overlying strata and surface induced by underground mining are processes involving temporal and spatial changes, which, in turn, cause damage to buildings. Estimating the dynamic ground movement and deformation is important to ascertain the damage degree of buildings. To predict the dynamic ground subsidence caused by underground coal mining and protect ground buildings from dynamic damage, a dynamic prediction model was established to calculate ground deformation. A derivation of the dynamic subsidence prediction model based on Knothe’s dynamic subsidence hypothesis and Litwiniszyn's stochastic medium theory was proposed under the conditions of constant advancing speed mining and post-mining. The composition and significance of the dynamic model were analyzed and provided a basis for calculating the dynamics and programming implementation. Through case studies, the dynamic prediction model was verified and the expected results were obtained during mining and post-mining. Results showed the dynamic prediction model is fit for the normal geological condition of mining but is limited for the special geological condition, that is, thick loose layer and thick bedrock. The study can meet the demand of protecting ground buildings from deformation caused by underground mining. The proposed model solves the time issue in mining subsidence prediction.

  17. A gecko-inspired double-sided adhesive.

    Science.gov (United States)

    Wang, Zhengzhi; Gu, Ping; Wu, Xiaoping

    2013-12-21

    Geckos' outstanding abilities to adhere to various surfaces are widely credited to the large actual contact areas of the fibrillar and hierarchical structures on their feet. These special features regulate the essential structural compliance for every attachment and thus provide robust yet reversible adhesions. Inspired by gecko's feet and our commonly used double-faced tape, we have successfully fabricated a gecko-inspired double-sided dry adhesive by using porous anodic alumina template assisted nano-wetting on a stiff polymer. It was determined that the obtained 2-sided structure showed largely decreased effective stiffness compared with its 1-sided counterpart, which favored better compliance and interfacial integrity. We also demonstrated that the repeatable double-sided adhesive improved the macroscopic normal and shear adhesion capacities over the widely-studied 1-side structure by ~50% and ~85%, respectively. By using the synthetic double-sided adhesive, the usage of traditional pressure-sensitive/chemical adhesives could be well avoided. Besides, the double-sided nanostructures showed great potential in finding new interesting properties and practical applications for the synthetic dry adhesives.

  18. Contact between rough surfaces and a criterion for macroscopic adhesion.

    Science.gov (United States)

    Pastewka, Lars; Robbins, Mark O

    2014-03-01

    At the molecular scale, there are strong attractive interactions between surfaces, yet few macroscopic surfaces are sticky. Extensive simulations of contact by adhesive surfaces with roughness on nanometer to micrometer scales are used to determine how roughness reduces the area where atoms contact and thus weakens adhesion. The material properties, adhesive strength, and roughness parameters are varied by orders of magnitude. In all cases, the area of atomic contact is initially proportional to the load. The prefactor rises linearly with adhesive strength for weak attractions. Above a threshold adhesive strength, the prefactor changes sign, the surfaces become sticky, and a finite force is required to separate them. A parameter-free analytic theory is presented that describes changes in these numerical results over up to five orders of magnitude in load. It relates the threshold adhesive strength to roughness and material properties, explaining why most macroscopic surfaces do not stick. The numerical results are qualitatively and quantitatively inconsistent with classical theories based on the Greenwood-Williamson approach that neglect the range of adhesion and do not include asperity interactions. PMID:24550489

  19. HPLC法测定镇江橡胶膏中士的宁及马钱子碱的含量%Determination of Strychnine and Brucine in Zhenjiang Adhesive Plaster by HPLC

    Institute of Scientific and Technical Information of China (English)

    陈清华; 耿秋霞; 汤小伟

    2012-01-01

    Objective: To establish a method for the determination of strychnine and brucine in the Zhenjiang Adhesive Plaster. Methods: The HPLC method was carried out on a column Kromasil-C18 (4.6 mmx250 mm, 5 μm) at the temperature of 30t, the mobile phase was composed of A-B (11 :89) ( A for acetonitrile, B for water-acetic acid-triethylamine (230:2.4:0.3) ), the flow rate was at 1.0 mL·min-1, the UV detection wavelength was at 254 nm. Results: The calibration curves of strychnine and brucine were in good linearities over the ranges of 0.0885~1.327 μg (r =0.9997) and 0.0522-0.782 μg (r =0.9960), respectively, and the average recoveries were 99.6% and 98.2%, respectively. Conclusion: This method is accurate, rapid, reproducible and suitable for the quality control of this preparation.%目的:建立镇江橡胶膏中士的宁及马钱子碱含量测定方法.方法:采用HPLC法,色谱柱为Kromasil-C18 (4.6 mm×250 mm,5μm),流动相为A-B (11:89)[A为乙腈,B由水-冰醋酸-三乙胺(230:2.4:0.3)组成],检测波长254 nm,流速1.0mL·min-1,柱温30C.结果:士的宁、马钱子碱分别在0.0885~1.327 μg(r=0.9997)、0.0522~0.782 μg(r=0.9960)范围内线性关系良好,平均回收率分别为99.6%、98.2%.结论:该方法准确、快速、重现性好,能有效控制本品质量.

  20. Wind tunnel determination of dynamic cross-coupling derivatives - A new approach

    Science.gov (United States)

    Hanff, E. S.; Orlik-Rueckemann, J.

    1980-01-01

    The latest developments in the NAE ongoing dynamic stability research program are briefly summarized. Emphasis is placed on the recently developed wind-tunnel data reduction procedures used to obtain cross and cross-coupling derivatives due to an oscillatory motion. These procedures, which account for the dynamic behaviour of the model-balance subsystem, are described for the balance configurations currently in use. The principles on which they are based, however, are quite general and can therefore be applied to other balance configurations. Two full-model dynamic stability apparatuses are described and typical results, obtained from dynamic calibrations as well as from wind-tunnel experiments, are presented.

  1. Determination of the Orientation and Dynamics of Ergosterol in Model Membranes Using Uniform 13C Labeling and Dynamically Averaged 13C Chemical Shift Anisotropies as Experimental Restraints

    Science.gov (United States)

    Soubias, O.; Jolibois, F.; Massou, S.; Milon, A.; Réat, V.

    2005-01-01

    A new strategy was established to determine the average orientation and dynamics of ergosterol in dimyristoylphosphatidylcholine model membranes. It is based on the analysis of chemical shift anisotropies (CSAs) averaged by the molecular dynamics. Static 13C CSA tensors were computed by quantum chemistry, using the gauge-including atomic-orbital approach within Hartree-Fock theory. Uniformly 13C-labeled ergosterol was purified from Pichia pastoris cells grown on labeled methanol. After reconstitution into dimyristoylphosphatidylcholine lipids, the complete 1H and 13C assignment of ergosterol's resonances was performed using a combination of magic-angle spinning two-dimensional experiments. Dynamically averaged CSAs were determined by standard side-band intensity analysis for isolated 13C resonances (C3 and ethylenic carbons) and by off-magic-angle spinning experiments for other carbons. A set of 18 constraints was thus obtained, from which the sterol's molecular order parameter and average orientation could be precisely defined. The validity of using computed CSAs in this strategy was verified on cholesterol model systems. This new method allowed us to quantify ergosterol's dynamics at three molar ratios: 16 mol % (Ld phase), 30 mol % (Lo phase), and 23 mol % (mixed phases). Contrary to cholesterol, ergosterol's molecular diffusion axis makes an important angle (14°) with the inertial axis of the rigid four-ring system. PMID:15923221

  2. Physics of adhesion and elasticity of biological cells

    Science.gov (United States)

    Safran, S. A.

    2006-03-01

    Forces exerted by adherent cells are important for many physiological processes such as wound healing and tissue formation. By pulling on their environment, cells sense rigidity gradients, boundaries and strains induced by the presence of other cells. Many cell types respond to these signals by actively adjusting the magnitude and direction of the adhesions that connect cells to surfaces or to each other. These adhesions are formed from membrane-bound integrin proteins and other cytoplasmic proteins that form condensed domains that grow in the direction of externally applied or internal, cytoskeletal forces. We present a model for the adsorption of adhesion proteins from the cell interior to the adhesion site and the resulting, force-sensitive anisotropic growth. The theory couples the mechanical forces to the non- linear adsorption dynamics and predicts the growth velocities of the back and front of the adhesion in qualitative agreement with experiment. The adhesion forces generated by a collection of cells in a tissue significantly alter the overall elastic response of the system. We model an ensemble of cells by an extension of the treatment of dielectric response of polar molecules to elastic interactions. By introducing the elastic analogy of the dielectric constant of the medium, we are able to predict the average cell polarization, their orientational order, and the effective material constants.

  3. Nanoparticle adhesion in proton exchange membrane fuel cell electrodes

    Science.gov (United States)

    He, Qianping; Joy, David C.; Keffer, David J.

    2013-11-01

    Carbon supported platinum (Pt/C) catalyst remains among the most preferable catalyst materials for Proton Exchange Membrane (PEM) fuel cells. However, platinum (Pt) particles suffer from poor durability and encounter electrochemical surface area (ESA) loss under operation with the accompany of Pt nanoparticle coarsening. Several proposed mechanisms have involved the Pt detachment from its carbonate support as an initial step for the deactivation of Pt nanoparticles. In this study, we investigated the detachment mechanism from the nano-adhesion point of view. Classic molecular dynamics simulations are performed on systems contain Pt nanoparticles of different sizes and shapes. A thin Nafion film (1 nm) at different hydration levels is also included in the system to study the environmental effect on nanoparticle adhesion. We found that the adhesion force strengthens as the Pt size goes up. Pt nanoparticles of tetrahedral shape exhibit relatively stronger connection with the carbon substrate due to its unique ‘anchor-like’ structure. Adhesion is enhanced with the introduction of a Nafion. The humidity level in the Nafion film has a rather complicated effect on the strength of nanoparticle adhesion. The binding energies and maximum adhesive forces are reported for all systems studied.

  4. Nanostructured niobium oxide coatings influence osteoblast adhesion.

    Science.gov (United States)

    Eisenbarth, E; Velten, D; Müller, M; Thull, R; Breme, J

    2006-10-01

    The interaction of osteoblasts was correlated to the roughness of nanosized surface structures of Nb(2)O(5) coatings on polished CP titanium grade 2. Nb(2)O(5) sol-gel coatings were selected as a model surface to study the interaction of osteoblasts with nanosized surface structures. The surface roughness was quantified by determination of the average surface finish (Ra number) by means of atomic force microscopy. Surface topographies with Ra = 7, 15, and 40 nm were adjusted by means of the annealing process parameters (time and temperature) within a sol-gel coating procedure. The observed osteoblast migration was fastest on smooth surfaces with Ra = 7 nm. The adhesion strength, spreading area, and collagen-I synthesis showed the best results on an intermediate roughness of Ra = 15 nm. The surface roughness of Ra = 40 nm was rather peaked and reduced the speed of cell reactions belonging to the adhesion process. PMID:16788971

  5. Adhesive joint and composites modeling in SIERRA.

    Energy Technology Data Exchange (ETDEWEB)

    Ohashi, Yuki; Brown, Arthur A.; Hammerand, Daniel Carl; Adolf, Douglas Brian; Chambers, Robert S.; Foulk, James W., III (.,; )

    2005-11-01

    Polymers and fiber-reinforced polymer matrix composites play an important role in many Defense Program applications. Recently an advanced nonlinear viscoelastic model for polymers has been developed and incorporated into ADAGIO, Sandia's SIERRA-based quasi-static analysis code. Standard linear elastic shell and continuum models for fiber-reinforced polymer-matrix composites have also been added to ADAGIO. This report details the use of these models for advanced adhesive joint and composites simulations carried out as part of an Advanced Simulation and Computing Advanced Deployment (ASC AD) project. More specifically, the thermo-mechanical response of an adhesive joint when loaded during repeated thermal cycling is simulated, the response of some composite rings under internal pressurization is calculated, and the performance of a composite container subjected to internal pressurization, thermal loading, and distributed mechanical loading is determined. Finally, general comparisons between the continuum and shell element approaches for modeling composites using ADAGIO are given.

  6. Bacterial monitoring with adhesive sheet in the international space station-"Kibo", the Japanese experiment module.

    Science.gov (United States)

    Ichijo, Tomoaki; Hieda, Hatsuki; Ishihara, Rie; Yamaguchi, Nobuyasu; Nasu, Masao

    2013-01-01

    Microbiological monitoring is important to assure microbiological safety, especially in long-duration space habitation. We have been continuously monitoring the abundance and diversity of bacteria in the International Space Station (ISS)-"Kibo" module to accumulate knowledge on microbes in the ISS. In this study, we used a new sampling device, a microbe-collecting adhesive sheet developed in our laboratory. This adhesive sheet has high operability, needs no water for sampling, and is easy to transport and store. We first validated the adhesive sheet as a sampling device to be used in a space habitat with regard to the stability of the bacterial number on the sheet during prolonged storage of up to 12 months. Bacterial abundance on the surfaces in Kibo was then determined and was lower than on the surfaces in our laboratory (10(5) cells [cm(2)](-1)), except for the return air grill, and the bacteria detected in Kibo were human skin microflora. From these aspects of microbial abundance and their phylogenetic affiliation, we concluded that Kibo has been microbiologically well maintained; however, microbial abundance may increase with the prolonged stay of astronauts. To ensure crew safety and understand bacterial dynamics in space habitation environments, continuous bacterial monitoring in Kibo is required.

  7. Adhesion and multi-materials

    International Nuclear Information System (INIS)

    Adhesion is a multidisciplinary science relevant to many practical fields. The main application of adhesion is bonding by adhesives. This technique is widely used in the industrial world and more specifically in the advanced technical domains. Adhesion is also involved in multi-component materials such as coatings, multilayer materials, polymer blends, composite materials... The multidisciplinary aspect of adhesion is well demonstrated by considering the wide variety of concepts, models and theories proposed for its description. An example of the adhesion between a fiber and a matrix in a composite material will lead to a general model relating the molecular properties of the interface to its capacity of stress transfer and hence to the macroscopic mechanical properties of the composite. This relationship is valid whatever the fiber (glass, carbon, polymeric) or the polymer matrix (thermoplastics, thermosetting). Any deviation from this model can be attributed to the existence of an interfacial zone or interphase exhibiting properties, mainly mechanical properties, different from the bulk matrix. Two examples are examined: the first one deals with the creation of a trans crystalline interphase in a semi-crystalline thermoplastic matrix and the second one is concerned with the formation of a pseudo glassy interphase in an elastomer matrix. These examples stress the need for complementary approaches in the understanding of adhesion phenomena at different levels of knowledge, from molecular to macroscopic. They also show how important it is to understand the mechanisms of formation of inter phases in order to be able to master the performance of multicomponent materials. (Author)

  8. Viral and epidemiological determinants of the invasion dynamics of novel dengue genotypes.

    Directory of Open Access Journals (Sweden)

    José Lourenço

    Full Text Available BACKGROUND: Dengue has become a major concern for international public health. Frequent epidemic outbreaks are believed to be driven by a complex interplay of immunological interactions between its four co-circulating serotypes and large fluctuations in mosquito densities. Viral lineage replacement events, caused for example by different levels of cross-protection or differences in viral fitness, have also been linked to a temporary change in dengue epidemiology. A major replacement event was recently described for South-East Asia where the Asian-1 genotype of dengue serotype 2 replaced the resident Asian/American type. Although this was proposed to be due to increased viral fitness in terms of enhanced human-to-mosquito transmission, no major change in dengue epidemiology could be observed. METHODS/RESULTS: Here we investigate the invasion dynamics of a novel, advantageous dengue genotype within a model system and determine the factors influencing the success and rate of fixation as well as their epidemiological consequences. We find that while viral fitness overall correlates with invasion success and competitive exclusion of the resident genotype, the epidemiological landscape plays a more significant role for successful emergence. Novel genotypes can thus face high risks of stochastic extinction despite their fitness advantage if they get introduced during episodes of high dengue prevalence, especially with respect to that particular serotype. CONCLUSION: The rarity of markers for positive selection has often been explained by strong purifying selection whereby the constraints imposed by dengue's two-host cycle are expected to result in a high rate of deleterious mutations. Our results demonstrate that even highly beneficial mutants are under severe threat of extinction, which would suggest that apart from purifying selection, stochastic effects and genetic drift beyond seasonal bottlenecks are equally important in shaping dengue's viral

  9. Water droplet excess free energy determined by cluster mitosis using guided molecular dynamics

    International Nuclear Information System (INIS)

    Atmospheric aerosols play a vital role in affecting climate by influencing the properties and lifetimes of clouds and precipitation. Understanding the underlying microscopic mechanisms involved in the nucleation of aerosol droplets from the vapour phase is therefore of great interest. One key thermodynamic quantity in nucleation is the excess free energy of cluster formation relative to that of the saturated vapour. In our current study, the excess free energy is extracted for clusters of pure water modelled with the TIP4P/2005 intermolecular potential using a method based on nonequilibrium molecular dynamics and the Jarzynski relation. The change in free energy associated with the “mitosis” or division of a cluster of N water molecules into two N/2 sub-clusters is evaluated. This methodology is an extension of the disassembly procedure used recently to calculate the excess free energy of argon clusters [H. Y. Tang and I. J. Ford, Phys. Rev. E 91, 023308 (2015)]. Our findings are compared to the corresponding excess free energies obtained from classical nucleation theory (CNT) as well as internally consistent classical theory (ICCT). The values of the excess free energy that we obtain with the mitosis method are consistent with CNT for large cluster sizes but for the smallest clusters, the results tend towards ICCT; for intermediate sized clusters, we obtain values between the ICCT and CNT predictions. Furthermore, the curvature-dependent surface tension which can be obtained by regarding the clusters as spherical droplets of bulk density is found to be a monotonically increasing function of cluster size for the studied range. The data are compared to other values reported in the literature, agreeing qualitatively with some but disagreeing with the values determined by Joswiak et al. [J. Phys. Chem. Lett. 4, 4267 (2013)] using a biased mitosis approach; an assessment of the differences is the main motivation for our current study

  10. Determining dynamic parameters of different-scale ionospheric irregularities over northern Siberia

    Science.gov (United States)

    Afraimovich, E. L.; Lipko, Y. V. Y. V.; Vugmeister, B. O.

    2000-01-01

    In 1995-1996, observations were carried out at Norilsk (geomagnetic latitude and longitude 64.2 degN and 160.4 degE) to determine dynamic parameters of irregularities in the high-latitude ionosphere. The short-baseline spaced-receiver method that has been implemented at the ionospheric facility of the Norilsk Integrated Magnetic-Ionospheric Station, provides a means of simultaneously measuring parameters of small-scale irregularities (spatial scale of 3-5 km) by the Similar-Fading Method (SFM), as well as of medium-scale irregularities (time scale of 10-30 min, spatial scale of hundreds of kilometres) by the Statistical Angle-of-arrival and Doppler Method (SADM). About 20 h of the observational data for the F2-layer under quiet geomagnetic conditions (Kp = 3) and about 15 h for the sporadic E-layer (Kp ~ 3) were processed. It has been found that the propagation directions and velocities of different-scale irregularities do not coincide. Small-scale irregularities of the F2-layer travel predominantly eastward or westward. The velocity of the F2-layer irregularities is about 100 m/s, and under disturbed conditions it is up to 200-250 m/s. Small-scale irregularities of the sporadic E-layer travel mostly in the northward direction. It is confirmed that the Es-layer is characterised by high velocities of the irregularities (as high as 1000 m/s). Medium-scale irregularities with periods in the range of 10-30 min travel mostly in a southward direction with velocities of 20-40 m/s.

  11. Climate warming and agricultural stressors interact to determine stream macroinvertebrate community dynamics.

    Science.gov (United States)

    Piggott, Jeremy J; Townsend, Colin R; Matthaei, Christoph D

    2015-05-01

    Global climate change is likely to modify the ecological consequences of currently acting stressors, but potentially important interactions between climate warming and land-use related stressors remain largely unknown. Agriculture affects streams and rivers worldwide, including via nutrient enrichment and increased fine sediment input. We manipulated nutrients (simulating agricultural run-off) and deposited fine sediment (simulating agricultural erosion) (two levels each) and water temperature (eight levels, 0-6°C above ambient) simultaneously in 128 streamside mesocosms to determine the individual and combined effects of the three stressors on macroinvertebrate community dynamics (community composition and body size structure of benthic, drift and insect emergence assemblages). All three stressors had pervasive individual effects, but in combination often produced additive or antagonistic outcomes. Changes in benthic community composition showed a complex interplay among habitat quality (with or without sediment), resource availability (with or without nutrient enrichment) and the behavioural/physiological tendency to drift or emerge as temperature rose. The presence of sediment and raised temperature both resulted in a community of smaller organisms. Deposited fine sediment strongly increased the propensity to drift. Stressor effects were most prominent in the benthic assemblage, frequently reflected by opposite patterns in individuals quitting the benthos (in terms of their propensity to drift or emerge). Of particular importance is that community measures of stream health routinely used around the world (taxon richness, EPT richness and diversity) all showed complex three-way interactions, with either a consistently stronger temperature response or a reversal of its direction when one or both agricultural stressors were also in operation. The negative effects of added fine sediment, which were often stronger at raised temperatures, suggest that streams already

  12. Water droplet excess free energy determined by cluster mitosis using guided molecular dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Lau, Gabriel V.; Müller, Erich A.; Jackson, George [Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom); Hunt, Patricia A. [Department of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom); Ford, Ian J. [Department of Physics and Astronomy and London Centre for Nanotechnology, University College London, Gower Street, London WC1E 6BT (United Kingdom)

    2015-12-28

    Atmospheric aerosols play a vital role in affecting climate by influencing the properties and lifetimes of clouds and precipitation. Understanding the underlying microscopic mechanisms involved in the nucleation of aerosol droplets from the vapour phase is therefore of great interest. One key thermodynamic quantity in nucleation is the excess free energy of cluster formation relative to that of the saturated vapour. In our current study, the excess free energy is extracted for clusters of pure water modelled with the TIP4P/2005 intermolecular potential using a method based on nonequilibrium molecular dynamics and the Jarzynski relation. The change in free energy associated with the “mitosis” or division of a cluster of N water molecules into two N/2 sub-clusters is evaluated. This methodology is an extension of the disassembly procedure used recently to calculate the excess free energy of argon clusters [H. Y. Tang and I. J. Ford, Phys. Rev. E 91, 023308 (2015)]. Our findings are compared to the corresponding excess free energies obtained from classical nucleation theory (CNT) as well as internally consistent classical theory (ICCT). The values of the excess free energy that we obtain with the mitosis method are consistent with CNT for large cluster sizes but for the smallest clusters, the results tend towards ICCT; for intermediate sized clusters, we obtain values between the ICCT and CNT predictions. Furthermore, the curvature-dependent surface tension which can be obtained by regarding the clusters as spherical droplets of bulk density is found to be a monotonically increasing function of cluster size for the studied range. The data are compared to other values reported in the literature, agreeing qualitatively with some but disagreeing with the values determined by Joswiak et al. [J. Phys. Chem. Lett. 4, 4267 (2013)] using a biased mitosis approach; an assessment of the differences is the main motivation for our current study.

  13. Water droplet excess free energy determined by cluster mitosis using guided molecular dynamics

    Science.gov (United States)

    Lau, Gabriel V.; Hunt, Patricia A.; Müller, Erich A.; Jackson, George; Ford, Ian J.

    2015-12-01

    Atmospheric aerosols play a vital role in affecting climate by influencing the properties and lifetimes of clouds and precipitation. Understanding the underlying microscopic mechanisms involved in the nucleation of aerosol droplets from the vapour phase is therefore of great interest. One key thermodynamic quantity in nucleation is the excess free energy of cluster formation relative to that of the saturated vapour. In our current study, the excess free energy is extracted for clusters of pure water modelled with the TIP4P/2005 intermolecular potential using a method based on nonequilibrium molecular dynamics and the Jarzynski relation. The change in free energy associated with the "mitosis" or division of a cluster of N water molecules into two N/2 sub-clusters is evaluated. This methodology is an extension of the disassembly procedure used recently to calculate the excess free energy of argon clusters [H. Y. Tang and I. J. Ford, Phys. Rev. E 91, 023308 (2015)]. Our findings are compared to the corresponding excess free energies obtained from classical nucleation theory (CNT) as well as internally consistent classical theory (ICCT). The values of the excess free energy that we obtain with the mitosis method are consistent with CNT for large cluster sizes but for the smallest clusters, the results tend towards ICCT; for intermediate sized clusters, we obtain values between the ICCT and CNT predictions. Furthermore, the curvature-dependent surface tension which can be obtained by regarding the clusters as spherical droplets of bulk density is found to be a monotonically increasing function of cluster size for the studied range. The data are compared to other values reported in the literature, agreeing qualitatively with some but disagreeing with the values determined by Joswiak et al. [J. Phys. Chem. Lett. 4, 4267 (2013)] using a biased mitosis approach; an assessment of the differences is the main motivation for our current study.

  14. How to determine the dynamic fracture energy of concrete. Theoretical considerations and experimental evidence

    NARCIS (Netherlands)

    Weerheijm, J.; Vegt, I.

    2011-01-01

    Data on the dynamic fracture energy of concrete are scarce and also not consistent due to different test methods, data analyses and definitions. In [1] the authors summarized and evaluated the test methods. Suggestions for the standardization of dynamic tensile testing were given. In the current pap

  15. Shearing Nanometer-Thick Confined Hydrocarbon Films: Friction and Adhesion

    DEFF Research Database (Denmark)

    Sivebæk, I. M.; Persson, B. N. J.

    2016-01-01

    We present molecular dynamics (MD) friction and adhesion calculations for nanometer-thick confined hydrocarbon films with molecular lengths 20, 100 and 1400 carbon atoms. We study the dependency of the frictional shear stress on the confining pressure and sliding speed. We present results...

  16. Relationship between the adhesive properties of bacteria and their transport and colonization in the subsurface environment. Final technical report

    Energy Technology Data Exchange (ETDEWEB)

    Fletcher, M.

    1997-03-13

    The adhesion of bacteria to sediment particle or rock surfaces considerably effects their transport in subsurface environments. This research focuses on the macromolecular properties of bacteria that determine their adhesiveness and on the significance of adhesion in transport of subsurface bacteria. Specific objectives include (1) to obtain adhesion mutants of subsurface Pseudomonas species altered in surface adhesives; (2) to determine alterations in adhesives in selected mutants; (3) to evaluate the effect of adhesiveness on transport and long-term distribution and colonization of bacteria in porous media. Primary methods will be tranposon mutagenesis to generate adhesion mutants, biochemical analyses of cell surface polymers, and the use of laboratory columns containing subsurface materials to study the distribution and transport of bacteria along flow paths over time.

  17. Focal Adhesion Kinases in Adhesion Structures and Disease

    Directory of Open Access Journals (Sweden)

    Pierre P. Eleniste

    2012-01-01

    Full Text Available Cell adhesion to the extracellular matrix (ECM is essential for cell migration, proliferation, and embryonic development. Cells can contact the ECM through a wide range of matrix contact structures such as focal adhesions, podosomes, and invadopodia. Although they are different in structural design and basic function, they share common remodeling proteins such as integrins, talin, paxillin, and the tyrosine kinases FAK, Pyk2, and Src. In this paper, we compare and contrast the basic organization and role of focal adhesions, podosomes, and invadopodia in different cells. In addition, we discuss the role of the tyrosine kinases, FAK, Pyk2, and Src, which are critical for the function of the different adhesion structures. Finally, we discuss the essential role of these tyrosine kinases from the perspective of human diseases.

  18. Focal adhesion kinases in adhesion structures and disease.

    Science.gov (United States)

    Eleniste, Pierre P; Bruzzaniti, Angela

    2012-01-01

    Cell adhesion to the extracellular matrix (ECM) is essential for cell migration, proliferation, and embryonic development. Cells can contact the ECM through a wide range of matrix contact structures such as focal adhesions, podosomes, and invadopodia. Although they are different in structural design and basic function, they share common remodeling proteins such as integrins, talin, paxillin, and the tyrosine kinases FAK, Pyk2, and Src. In this paper, we compare and contrast the basic organization and role of focal adhesions, podosomes, and invadopodia in different cells. In addition, we discuss the role of the tyrosine kinases, FAK, Pyk2, and Src, which are critical for the function of the different adhesion structures. Finally, we discuss the essential role of these tyrosine kinases from the perspective of human diseases. PMID:22888421

  19. Hemodynamic aspects of reduced platelet adhesion on bioinspired microstructured surfaces.

    Science.gov (United States)

    Pham, Tam Thanh; Wiedemeier, Stefan; Maenz, Stefan; Gastrock, Gunter; Settmacher, Utz; Jandt, Klaus D; Zanow, Jürgen; Lüdecke, Claudia; Bossert, Jörg

    2016-09-01

    Occlusion by thrombosis due to the absence of the endothelial cell layer is one of the most frequent causes of failure of artificial vascular grafts. Bioinspired surface structures may have a potential to reduce the adhesion of platelets contributing to hemostasis. The aim of this study was to investigate the hemodynamic aspects of platelet adhesion, the main cause of thrombosis, on bioinspired microstructured surfaces mimicking the endothelial cell morphology. We tested the hypothesis that platelet adhesion is statistically significantly reduced on bioinspired microstructured surfaces compared to unstructured surfaces. Platelet adhesion as a function of the microstructure dimensions was investigated under flow conditions on polydimethylsiloxane (PDMS) surfaces by a combined experimental and theoretical approach. Platelet adhesion was statistically significantly reduced (by up to 78%; p≤0.05) on the microstructured PDMS surfaces compared to that on the unstructured control surface. Finite element method (FEM) simulations of blood flow dynamic revealed a micro shear gradient on the microstructure surfaces which plays a pivotal role in reducing platelet adhesion. On the surfaces with the highest differences of the shear stress between the top of the microstructures and the ground areas, platelet adhesion was reduced most. In addition, the microstructures help to reduce the interaction strength between fluid and surfaces, resulting in a larger water contact angle but no higher resistance to flow compared to the unstructured surface. These findings provide new insight into the fundamental mechanisms of reducing platelet adhesion on microstructured bioinspired surfaces and may lay the basis for the development of innovative next generation artificial vascular grafts with reduced risk of thrombosis. PMID:27239904

  20. Photovoltaic module with adhesion promoter

    Science.gov (United States)

    Xavier, Grace

    2013-10-08

    Photovoltaic modules with adhesion promoters and methods for fabricating photovoltaic modules with adhesion promoters are described. A photovoltaic module includes a solar cell including a first surface and a second surface, the second surface including a plurality of interspaced back-side contacts. A first glass layer is coupled to the first surface by a first encapsulating layer. A second glass layer is coupled to the second surface by a second encapsulating layer. At least a portion of the second encapsulating layer is bonded directly to the plurality of interspaced back-side contacts by an adhesion promoter.

  1. Adhesives from modified soy protein

    Science.gov (United States)

    Sun, Susan; Wang, Donghai; Zhong, Zhikai; Yang, Guang

    2008-08-26

    The, present invention provides useful adhesive compositions having similar adhesive properties to conventional UF and PPF resins. The compositions generally include a protein portion and modifying ingredient portion selected from the group consisting of carboxyl-containing compounds, aldehyde-containing compounds, epoxy group-containing compounds, and mixtures thereof. The composition is preferably prepared at a pH level at or near the isoelectric point of the protein. In other preferred forms, the adhesive composition includes a protein portion and a carboxyl-containing group portion.

  2. Focal Adhesion Kinases in Adhesion Structures and Disease

    OpenAIRE

    Pierre P. Eleniste; Angela Bruzzaniti

    2012-01-01

    Cell adhesion to the extracellular matrix (ECM) is essential for cell migration, proliferation, and embryonic development. Cells can contact the ECM through a wide range of matrix contact structures such as focal adhesions, podosomes, and invadopodia. Although they are different in structural design and basic function, they share common remodeling proteins such as integrins, talin, paxillin, and the tyrosine kinases FAK, Pyk2, and Src. In this paper, we compare and contrast the basic organiza...

  3. Ultrastructural and Histochemical Characterization of the Zebra Mussel Adhesive Apparatus

    Science.gov (United States)

    Farsad, Nikrooz

    Since their accidental introduction into the Great Lakes in mid- to late-1980s, the freshwater zebra mussels, Dreissena polymorpha, have colonized most lakes and waterways across eastern North America. Their rapid spread is partly attributed to their ability to tenaciously attach to hard substrates via an adhesive apparatus called the byssus, resulting in serious environmental and economic impacts. A detailed ultrastructural study of the byssus revealed a 10 nm adhesive layer at the attachment interface. Distributions of the main adhesive amino acid, 3,4-dihydroxyphenylalanine (DOPA), and its oxidizing (cross-linking) enzyme, catechol oxidase, were determined histochemically. It was found that, upon aging, DOPA levels remained high in the portion of the byssus closest to the interface, consistent with an adhesive role. In contrast, reduced levels of DOPA corresponded well with high levels of catechol oxidase in the load-bearing component of the byssus, presumably forming cross-links and increasing the cohesive strength.

  4. Timescales and Frequencies of Reversible and Irreversible Adhesion Events of Single Bacterial Cells.

    Science.gov (United States)

    Hoffman, Michelle D; Zucker, Lauren I; Brown, Pamela J B; Kysela, David T; Brun, Yves V; Jacobson, Stephen C

    2015-12-15

    In the environment, most bacteria form surface-attached cell communities called biofilms. The attachment of single cells to surfaces involves an initial reversible stage typically mediated by surface structures such as flagella and pili, followed by a permanent adhesion stage usually mediated by polysaccharide adhesives. Here, we determine the absolute and relative timescales and frequencies of reversible and irreversible adhesion of single cells of the bacterium Caulobacter crescentus to a glass surface in a microfluidic device. We used fluorescence microscopy of C. crescentus expressing green fluorescent protein to track the swimming behavior of individual cells prior to adhesion, monitor the cell at the surface, and determine whether the cell reversibly or irreversibly adhered to the surface. A fluorescently labeled lectin that binds specifically to polar polysaccharides, termed holdfast, discriminated irreversible adhesion events from reversible adhesion events where no holdfast formed. In wild-type cells, the holdfast production time for irreversible adhesion events initiated by surface contact (23 s) was 30-times faster than the holdfast production time that occurs through developmental regulation (13 min). Irreversible adhesion events in wild-type cells (3.3 events/min) are 15-times more frequent than in pilus-minus mutant cells (0.2 events/min), indicating the pili are critical structures in the transition from reversible to irreversible surface-stimulated adhesion. In reversible adhesion events, the dwell time of cells at the surface before departing was the same for wild-type cells (12 s) and pilus-minus mutant cells (13 s), suggesting the pili do not play a significant role in reversible adhesion. Moreover, reversible adhesion events in wild-type cells (6.8 events/min) occur twice as frequently as irreversible adhesion events (3.3 events/min), demonstrating that most cells contact the surface multiple times before transitioning from reversible to

  5. Biomimetic emulsions reveal the effect of homeostatic pressure on cell-cell adhesion

    CERN Document Server

    Pontani, Lea-Laetitia; Viasnoff, Virgile; Brujic, Jasna

    2012-01-01

    Cell-cell contacts in tissues are continuously subject to mechanical forces due to homeostatic pressure and active cytoskeleton dynamics. While much is known about the molecular pathways of adhesion, the role of mechanics is less well understood. To isolate the role of pressure we present a dense packing of functionalized emulsion droplets in which surface interactions are tuned to mimic those of real cells. By visualizing the microstructure in 3D we find that a threshold compression force is necessary to overcome electrostatic repulsion and surface elasticity and establish protein-mediated adhesion. Varying the droplet interaction potential maps out a phase diagram for adhesion as a function of force and salt concentration. Remarkably, fitting the data with our theoretical model predicts binder concentrations in the adhesion areas that are similar to those found in real cells. Moreover, we quantify the adhesion size dependence on the applied force and thus reveal adhesion strengthening with increasing homeos...

  6. Cell Adhesion and Its Endocytic Regulation in Cell Migration during Neural Development and Cancer Metastasis

    Directory of Open Access Journals (Sweden)

    Takeshi Kawauchi

    2012-04-01

    Full Text Available Cell migration is a crucial event for tissue organization during development, and its dysregulation leads to several diseases, including cancer. Cells exhibit various types of migration, such as single mesenchymal or amoeboid migration, collective migration and scaffold cell-dependent migration. The migration properties are partly dictated by cell adhesion and its endocytic regulation. While an epithelial-mesenchymal transition (EMT-mediated mesenchymal cell migration requires the endocytic recycling of integrin-mediated adhesions after the disruption of cell-cell adhesions, an amoeboid migration is not dependent on any adhesions to extracellular matrix (ECM or neighboring cells. In contrast, a collective migration is mediated by both cell-cell and cell-ECM adhesions, and a scaffold cell-dependent migration is regulated by the endocytosis and recycling of cell-cell adhesion molecules. Although some invasive carcinoma cells exhibit an EMT-mediated mesenchymal or amoeboid migration, other cancer cells are known to maintain cadherin-based cell-cell adhesions and epithelial morphology during metastasis. On the other hand, a scaffold cell-dependent migration is mainly utilized by migrating neurons in normal developing brains. This review will summarize the structures of cell adhesions, including adherens junctions and focal adhesions, and discuss the regulatory mechanisms for the dynamic behavior of cell adhesions by endocytic pathways in cell migration in physiological and pathological conditions, focusing particularly on neural development and cancer metastasis.

  7. Oxide film microstructure: the link between surface preparation processes and strength/durability of adhesively bonded aluminum. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Hsia, K. Jimmy; Pearlstein, Arne J.; Scheeline, Alexander; Shang, Jian Ku

    2000-11-30

    Strength and durability of adhesive bonding of aluminum alloys structures are intrinsically determined by the surface microstructures and interfacial failure micromechanisms. The current project presents a multidisciplinary approach to addressing critical issues controlling the strength and durability of adhesive bonds of aluminum alloys. Three main thrust areas have been pursued: surface treatment technology development to achieve desirable surface microstructures; relationship between surface structure and properties of adhesive bonds; and failure mechanisms of adhesively bonded components.

  8. Denture Adhesives - A Literature Review

    Directory of Open Access Journals (Sweden)

    Sudhanshu Shekhar

    2016-06-01

    Full Text Available Successful complete denture treatment combines exemplary technique, effective patient rapport and education and familiarity with all possible management options to provide the highest degree of patient satisfaction. Dentists need to know about denture adhesives to be able to identify those patients who actually need them and to be able to educate them about the advantages, disadvantages and correct use of these products. Denture adhesives are commercially available nontoxic, soluble materials that when applied to the tissue surface of dentures enhance their retention, stability and performance. They were introduced in dentistry in the late 18th century. The first patent related to adhesives was issued in 1913, followed in the 1920’s and 1930’s. The purpose of the use of denture adhesives can be described as to subjectively benefit denture-wearers with improved stability, retention and comfort of their dentures, and with improved incisal force, masticatory ability, and confidence.

  9. Determining the Role of Dynamic Hyperinflation in Patients with Severe Chronic Obstructive Pulmonary Disease

    NARCIS (Netherlands)

    Klooster, Karin; ten Hacken, Nick H. T.; Hartman, Jorine E.; Sciurba, Frank C.; Kerstjens, Huib A. M.; Slebos, Dirk-Jan

    2015-01-01

    Background: Dynamic hyperinflation due to increased respiratory frequency during exercise is associated with limitations in exercise capacity in patients with moderately severe chronic obstructive pulmonary disease (COPD). Objectives: The present study assessed whether the manually paced tachypnea (

  10. ANALYSIS OF METHOD FOR DETERMINING AZIMUTH OF PRINCIPAL AXIS OF INERTIA BASED ON DYNAMIC BALANCE MEASUREMENT

    Institute of Scientific and Technical Information of China (English)

    ZHAO Jun; GUAN Yingzi; QI Naiming

    2006-01-01

    The dynamic balance quality of a rotating object is an important factor to maintain the stability and accuracy for motion. The azimuth of the principal axis of inertia is a major sign of dynamic balance. A usual method is measuring moment of inertia matrix relative to some base coordinates on a rotary inertia machine so as to calculate the azimuth of principal axis of inertia. By using the measured unbalance results on the two trimmed planes on a vertical hard bearing double-plane dynamic balancing machine, the dimension and direction of couple unbalance can be found. An azimuth angle formula for the principal axis of inertia is derived and is solved by using unbalance quantities. The experiments indicate that method based on dynamic balancing measurement is proved rational and effective and has a fine precision.

  11. Determination of $\\Lambda_{\\bar{MS}}$ from quenched and $N_f = 2$ dynamical QCD

    CERN Document Server

    Booth, S; Horsley, R; Irving, A C; Joó, B; Pickles, S; Pleiter, D; Rakow, P E L; Schierholz, G; Sroczynski, Z; Stüben, H

    2001-01-01

    The scale parameter $\\Lambda_{\\bar{MS}}$ is computed on the lattice in the quenched approximation and for $N_f = 2$ flavors of light dynamical quarks. The dynamical calculation is done with non-perturbatively $O(a)$ improved Wilson fermions. In the continuum limit we obtain $\\Lambda_{\\bar{MS}}^{N_f=0} = 243(1)(10)$ MeV and $\\Lambda_{\\bar{MS}}^{N_f=2} = 203(6)(20)$ MeV, respectively.

  12. Underwater adhesion: The barnacle way

    Digital Repository Service at National Institute of Oceanography (India)

    Khandeparker, L.; Anil, A.C.

    rosa and demonstrated the stimulatory effect of dopamine and noradrenaline on such secretion. Their study indicated exocytosis to be the major mode of cement secretion and suggest that gradual, localized exocytotic secretion of cement triggered... by catecholaminergic neurons to be the key mechanism during permanent attachment by barnacle cyprids [51]. Properties of barnacle adhesive The resistance to chemical breakdown by barnacle adhesive caused a major problem in its characterization. However...

  13. Laser surface modification and adhesion

    CERN Document Server

    Mittal, K L

    2014-01-01

    The book provides a unique overview on laser techniques and applications for the purpose of improving adhesion by altering surface chemistry and topography/morphology of the substrate. It details laser surface modification techniques for a wide range of industrially relevant materials (plastics, metals, ceramics, composites) with the aim to improve and enhance their adhesion to other materials. The joining of different materials is of critical importance in the fabrication of many and varied products.

  14. Notch-Mediated Cell Adhesion

    OpenAIRE

    Akihiko Murata; Shin-Ichi Hayashi

    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...

  15. Adhesive capsulitis: a case report

    OpenAIRE

    Kazemi, Mohsen

    2000-01-01

    Adhesive capsulitis or frozen shoulder is an uncommon entity in athletes. However, it is a common cause of shoulder pain and disability in the general population. Although it is a self limiting ailment, its rather long, restrictive and painful course forces the affected person to seek treatment. Conservative management remains the mainstay treatment of adhesive capsulitis. This includes chiropractic manipulation of the shoulder, therapeutic modalities, mobilization, exercise, soft tissue ther...

  16. Unfolding Grammars in Adhesive Categories

    OpenAIRE

    Baldan, Paolo; Corradini, Andrea; Heindel, Tobias; König, Barbara; Sobocinski, Pawel

    2009-01-01

    We generalize the unfolding semantics, previously developed for concrete formalisms such as Petri nets and graph grammars, to the abstract setting of (single pushout) rewriting over adhesive categories. The unfolding construction is characterized as a coreflection, i.e. the unfolding functor arises as the right adjoint to the embedding of the category of occurrence grammars into the category of grammars.As the unfolding represents potentially infinite computations, we need to work in adhesive...

  17. Analysis of dynamic and static filtration and determination of MUD cake parameters

    Energy Technology Data Exchange (ETDEWEB)

    Calcada, L.A.; Scheid, C.M.; Araujo, C.A.O. de [Universidade Federal Rural do Rio de Janeiro (UFRRJ), Seropedica, RJ (Brazil). Dept. de Engenharia Quimica], e-mail: calcada@ufrrj.br; Waldmann, A.T.A.; Martins, A.L. [Petroleo Brasileiro S.A. (CENPES/PETROBRAS), Rio de Janeiro, RJ (Brazil). Centro de Pesquisas

    2011-07-15

    Drilling operations around the world employ a concept called overbalance. During this process, it is well known that dynamic and static filtration can occur. Thin filter cakes and low fluid-invasion rates are extremely desirable to promote optimal logging conditions and permeability return. The aim of this work was to compare the different behavior between dynamic and static filtration in drilling wells. To investigate the filtration process of Newtonian suspensions, we built a dynamic and static filtration loop with which we acquired experimental filtration volume data as a function of time. The filtration loop included a tank mixer where a Newtonian aqueous calcium carbonate polydisperse suspension was homogenized. The suspension was pumped through tubes to a dynamic or a static filtration cell. We validated a theoretical model based on Darcy's law and on mass conservation proposed by Ferreira and Massarani (2005). That model predicted mud cake buildup and filtrate flow rate for Newtonian suspensions. Relying on both models and the experimental data, filter cake parameters were calculated. We discuss, based on these parameters, the effects of the filtration configuration in dynamic and static modes. Finally, we generalized Ferreira and Massarani's model (2005) for procedures involving non-Newtonian suspensions. This new model can predict dynamic filtration and fluid invasion for non-Newtonian suspensions as drilling fluids. (author)

  18. Environmental factors that determine the occurrence and seasonal dynamics of Aphanizomenon flos-aquae

    Directory of Open Access Journals (Sweden)

    Yoshimasa YAMAMOTO

    2009-02-01

    Full Text Available This study investigated the seasonal dynamics of two populations of Aphanizomenon flos-aquae Ralfs ex Bornet & Flahault var. flos-aquae and four populations of A. flos-aquae var. klebahnii Elenkin in eutrophic water bodies over 1 year from February 2006 to January 2007. The growth of A. flos-aquae var. flos-aquae was promoted at high temperatures even if in one case the biomass development was very low when other co-occurring cyanoprokaryotes (Anabaena spp. and Microcystis spp. were abundant. In contrast, the highest density of the other population of A. flos-aquae var. flos-aquae was observed in August when the population density of M. aeruginosa (Kützing Kützing reached an annual peak. A. flos-aquae var. flos-aquae usually bloomed in summer but could also tolerate low temperatures in the winter, and was present in relatively high densities. The populations of A. flos-aquae var. klebahnii observed in this study can be divided into three groups based on preferred temperature; three populations increased in winter, and the other increased in summer. Large biomasses of the low-temperature-adapted A. flos-aquae were observed mainly during winter when population densities of co-occurring cyanoprokaryotes (Anabaena spp., Microcystis spp. and Planktothrix raciborskii (Woloszynska Anagnostidis & Komárek were relatively low or almost absent. The increase in or existence of cooccurring cyanoprokaryotes during the summer resulted in a decrease of the A. flos-aquae population density. It was revealed that high temperatures (20-25 °C are suitable for maintaining A. flos-aquae var. klebahnii strains isolated from the study ponds, implying that low-temperature-adapted A. flos-aquae can grow over a wide range of water temperatures. The high-temperatureadapted A. flos-aquae var. klebahnii co-existed with M. aeruginosa during summer; however, its peak population density was significantly lower than those in previous years when M. aeruginosa was absent

  19. Mouse lung adhesion assay for Bordetella pertussis

    Energy Technology Data Exchange (ETDEWEB)

    Burns, K.A.; Freer, J.H. (Department of Microbiology, Alexander Stone Building, Bearsden, Glasgow, Scotland)

    1982-03-01

    The ability of Bordetella pertussis to adhere to cell surfaces has been demonstrated by adhesion to tissue culture cells and adhesion to chicken, hamster or rabbit trachea in organ culture. In this report a mouse lung assay for adhesion is described and the results obtained using two virulent strains of B. pertussis and their avirulent counterparts. These were a C modulation of one of the original virulent strains and a phase IV variant of the other virulent strain. Organisms were radiolabelled by adding 1 ..mu..Ci (37 K Bq) of (/sup 14/C)glutamic acid per 10 ml of culture medium before inoculation and incubation for 5 days. The lungs were washed by perfusion in situ with at least two volumes (1 ml) of sterile 1% (w/v) casamino acids. The percentage of the inoculated organisms retained in the lungs was determined, after removal of the lungs, by one of the following two methods: viable count or radioactive count. Results for both methods were expressed as the percentage of the inoculum retained in the lungs plus or minus one standard deviation.

  20. A feasibility study of using two-component polyurethane adhesive in constructing wooden structures

    Institute of Scientific and Technical Information of China (English)

    Mohammad Derikvand; Ghanbar Ebrahimi; Mehdi Tajvidi

    2014-01-01

    This investigation was conducted to determine the feasibility of using a two-component polyurethane (PUR) adhesive, with special waterproof properties, in constructing wooden structures. We designed and conducted tests to compare the shear strength and adhesion per-formance of PUR with polyvinyl acetate (PVAc) adhesive on block-shear specimens constructed of oriental beech (Fagus orientalis L.), fir (Abies alba Mill.), poplar (Populus deltoides Bartr.), white oak (Quercus alba L.), sycamore (Platanus orientalis L.) and white walnut (Juglans cinerea L.). The values of the percentage of wood failure were also determined in specimens constructed with each adhesive. The highest shear strength values of both adhesives were obtained in specimens constructed of beech, while the lowest shear strength values were obtained in fir and poplar specimens. Average shear strength of the PUR adhesive was 16.5%higher than that of the PVAc adhesive. Specimens constructed of fir, poplar and sycamore were characterised by the highest percentages of wood failure, whereas the lowest average percentages of wood failure were obtained in beech and oak specimens. With the exception of oak specimens, there was no statistically significant difference between per-centage of wood failure among the PUR and PVAc adhesives. Generally, the PUR adhesive showed an acceptable adhesion performance on wood materials used in our study.

  1. Fibrillar Adhesive for Climbing Robots

    Science.gov (United States)

    Pamess, Aaron; White, Victor E.

    2013-01-01

    A climbing robot needs to use its adhesive patches over and over again as it scales a slope. Replacing the adhesive at each step is generally impractical. If the adhesive or attachment mechanism cannot be used repeatedly, then the robot must carry an extra load of this adhesive to apply a fresh layer with each move. Common failure modes include tearing, contamination by dirt, plastic deformation of fibers, and damage from loading/ unloading. A gecko-like fibrillar adhesive has been developed that has been shown useful for climbing robots, and may later prove useful for grasping, anchoring, and medical applications. The material consists of a hierarchical fibrillar structure that currently contains two levels, but may be extended to three or four levels in continuing work. The contacting level has tens of thousands of microscopic fibers made from a rubberlike material that bend over and create intimate contact with a surface to achieve maximum van der Waals forces. By maximizing the real area of contact that these fibers make and minimizing the bending energy necessary to achieve that contact, the net amount of adhesion has been improved dramatically.

  2. Adhesion energy, surface traction and surface tension in liquid xenon

    Indian Academy of Sciences (India)

    B Mathew; G A Adebayo

    2011-12-01

    We calculated the adhesion energy, the surface traction and the surface energy of liquid xenon using molecular dynamics (MD) simulation. The value of the adhesion energy for liquid xenon at a reduced density of 0.630 was found to be 0.591 J/m2 and the surface traction has a peak at = 3.32 Å. It was observed that the attraction of the molecules in the liquid surface which produces a resistance to penetration decreases with temperature. This may be attributed to the greater average separation of molecules at higher temperature.

  3. Investigating On-Orbit Attitude Determination Anomalies for the Solar Dynamics Observatory Mission

    Science.gov (United States)

    Vess, Melissa F.; Starin, Scott R.; Chia-Kuo, Alice Liu

    2011-01-01

    The Solar Dynamics Observatory (SDO) was launched on February 11, 2010 from Kennedy Space Center on an Atlas V launch vehicle into a geosynchronous transfer orbit. SDO carries a suite of three scientific instruments, whose observations are intended to promote a more complete understanding of the Sun and its effects on the Earth's environment. After a successful launch, separation, and initial Sun acquisition, the launch and flight operations teams dove into a commissioning campaign that included, among other things, checkout and calibration of the fine attitude sensors and checkout of the Kalman filter (KF) and the spacecraft s inertial pointing and science control modes. In addition, initial calibration of the science instruments was also accomplished. During that process of KF and controller checkout, several interesting observations were noticed and investigated. The SDO fine attitude sensors consist of one Adcole Digital Sun Sensor (DSS), two Galileo Avionica (GA) quaternion-output Star Trackers (STs), and three Kearfott Two-Axis Rate Assemblies (hereafter called inertial reference units, or IRUs). Initial checkout of the fine attitude sensors indicated that all sensors appeared to be functioning properly. Initial calibration maneuvers were planned and executed to update scale factors, drift rate biases, and alignments of the IRUs. After updating the IRU parameters, the KF was initialized and quickly reached convergence. Over the next few hours, it became apparent that there was an oscillation in the sensor residuals and the KF estimation of the IRU bias. A concentrated investigation ensued to determine the cause of the oscillations, their effect on mission requirements, and how to mitigate them. The ensuing analysis determined that the oscillations seen were, in fact, due to an oscillation in the IRU biases. The low frequencies of the oscillations passed through the KF, were well within the controller bandwidth, and therefore the spacecraft was actually

  4. Effect of thermal aging on the tensile bond strength at reduced areas of seven current adhesives.

    Science.gov (United States)

    Baracco, Bruno; Fuentes, M Victoria; Garrido, Miguel A; González-López, Santiago; Ceballos, Laura

    2013-07-01

    The purpose of this study was to determine the micro-tensile bond strength (MTBS) to dentin of seven adhesive systems (total and self-etch adhesives) after 24 h and 5,000 thermocycles. Dentin surfaces of human third molars were exposed and bonded with two total-etch adhesives (Adper Scotchbond 1 XT and XP Bond), two two-step self-etch adhesives (Adper Scotchbond SE and Filtek Silorane Adhesive System) and three one-step self-etch adhesives (G-Bond, Xeno V and Bond Force). All adhesive systems were applied following manufacturers' instructions. Composite buildups were constructed and the bonded teeth were then stored in water (24 h, 37 °C) or thermocycled (5,000 cycles) before being sectioned and submitted to MTBS test. Two-way ANOVA and subsequent comparison tests were applied at α = 0.05. Characteristic de-bonded specimens were analyzed using scanning electron microscopy (SEM). After 24 h water storage, MTBS values were highest with XP Bond, Adper Scotchbond 1 XT, Filtek Silorane Adhesive System and Adper Scotchbond SE and lowest with the one-step self-etch adhesives Bond Force, Xeno V and G-Bond. After thermocycling, MTBS values were highest with XP Bond, followed by Filtek Silorane Adhesive System, Adper Scotchbond SE and Adper Scotchbond 1 XT and lowest with the one-step self-etch adhesives Bond Force, Xeno V and G-Bond. Thermal aging induced a significant decrease in MTBS values with all adhesives tested. The resistance of resin-dentin bonds to thermal-aging degradation was material dependent. One-step self-etch adhesives obtained the lowest MTBS results after both aging treatments, and their adhesive capacity was significantly reduced after thermocycling.

  5. Bond strength of adhesives to dentin contaminated with smoker’s saliva

    Science.gov (United States)

    Oguri, Makoto; O’Keefe, Kathy; Dusevish, Vladimir; Spencer, Paulette; Powers, John M.; Marshall, Grayson W.

    2010-01-01

    The purpose of this study was to determine the effects of contamination with smoker’s and non-smoker’s saliva on the bond strength of resin composite to superficial dentin using different adhesive systems. The interfacial structure between the resin and dentin was evaluated for each treatment using environmental scanning electron microscopy (ESEM). Freshly extracted human molars were ground with 600-grit SiC paper to expose the superficial dentin. Adhesives [One-Up-Bond-F-Plus (OUFP) and Adper-Prompt-L-Pop (APLP)] and resin composite (TPH-Spectrum) were bonded to the dentin (n = 8/group, 180 total specimens) under five surface conditions: control (adhesive applied following manufacturers’ instructions); saliva, then 5-s air dry, then adhesive; adhesive, saliva, 5-s air dry; adhesive, saliva, 5-s water rinse, 5-s air dry (ASW group); and adhesive, saliva, 5-s water rinse, 5-s air dry, reapply adhesive (ASWA group). After storage in water at 37°C for 24 h, the specimens were debonded under tension at a speed of 0.5 mm/min. ESEM photomicrographs of the dentin/adhesive interfaces were taken. Mean bond strength ranged from 8.1 to 24.1 MPa. Fisher’s protected least significant difference (P = 0.05) intervals for critical adhesive, saliva, and surface condition differences were 1.3, 1.3, and 2.1 MPa, respectively. There were no significant differences in bond strength to dentin between contamination by smoker’s and non-smoker’s saliva, but bond strengths were significantly different between adhesive systems, with OUFP twice as strong as APLP under almost all conditions. After adhesive application and contamination with either smoker’s or nonsmoker’s saliva followed by washing and reapplication of the adhesive (ASWA group), the bond strength of both adhesive systems was the same as that of the control group. PMID:20155506

  6. Differential adhesion of tumor cells to capillary endothelial cells in vitro.

    OpenAIRE

    Alby, L; Auerbach, R

    1984-01-01

    Adhesion studies were carried out to determine the relative ability of glioma cells and ovary-derived teratoma cells to adhere to endothelial cells obtained from mouse brain capillaries (designated MBE cell line) or mouse ovaries (designated MOE cell line). The teratoma cells showed preferential adhesion to MOE cells, whereas the glioma cells showed preferential adhesion to the MBE cell line. In contrast, the glioma and teratoma cells adhered equally to L929 and 3T3 fibroblasts. A testicular ...

  7. An Analytical Model for Predicting the Stress Distributions within Single-Lap Adhesively Bonded Beams

    Directory of Open Access Journals (Sweden)

    Xiaocong He

    2014-01-01

    Full Text Available An analytical model for predicting the stress distributions within single-lap adhesively bonded beams under tension is presented in this paper. By combining the governing equations of each adherend with the joint kinematics, the overall system of governing equations can be obtained. Both the adherends and the adhesive are assumed to be under plane strain condition. With suitable boundary conditions, the stress distribution of the adhesive in the longitudinal direction is determined.

  8. Obtaining Arbitrary Prescribed Mean Field Dynamics for Recurrently Coupled Networks of Type-I Spiking Neurons with Analytically Determined Weights

    Directory of Open Access Journals (Sweden)

    Wilten eNicola

    2016-02-01

    Full Text Available A fundamental question in computational neuroscience is how to connect a network of spiking neurons to produce desired macroscopic or mean field dynamics. One possible approach is through the Neural Engineering Framework (NEF. The NEF approach requires quantities called decoders which are solved through an optimization problem requiring large matrix inversion. Here, we show how a decoder can be obtained analytically for type I and certain type II firing rates as a function of the heterogeneity of its associated neuron. These decoders generate approximants for functions that converge to the desired function in mean-squared error like 1/N, where N is the number of neurons in the network. We refer to these decoders as scale-invariant decoders due to their structure. These decoders generate weights for a network of neurons through the NEF formula for weights. These weights force the spiking network to have arbitrary and prescribed mean field dynamics. The weights generated with scale-invariant decoders all lie on low dimensional hypersurfaces asymptotically. We demonstrate the applicability of these scale-invariant decoders and weight surfaces by constructing networks of spiking theta neurons that replicate the dynamics of various well known dynamical systems such as the neural integrator, Van der Pol system and the Lorenz system. As these decoders are analytically determined and non-unique, the weights are also analytically determined and non-unique. We discuss the implications for measured weights of neuronal networks

  9. Adhesion quality of glued joints from different commercial wood species

    Directory of Open Access Journals (Sweden)

    Alexandre Miguel do Nascimento

    2013-12-01

    Full Text Available The objective of this study was to determine the effect of wood density, adhesive type and gluing pressure on the shear strength of glued joints of fourteen commercial wood species. Wood pieces were classified in three density classes (Class 1: less than 0.55 g cm-3; Class 2: from 0.55 to 0.75 g cm-3; and Class 3: greater than 0.75 g cm-3 and joints bonded with two adhesives: polyvinyl acetate (PVA and urea-formaldehyde (UF, under two different pressures: 6 and 12 kgf cm-2. Glued joints bonded with PVA adhesive presented higher shear strength than those bonded with UF adhesive. For percentage of wood failure, the PVA adhesive had the best performance, however, only Classes 1 and 2 reached the values required by ASTM 3110 standard. Glued joints from Class 3, bonded with UF adhesive, did not reach the values of solid wood. The gluing pressure of 12 kgf cm-2 was more efficient for Class 3, for both shear strength and percentage of wood failure.

  10. Role of dystrophins and utrophins in platelet adhesion process.

    Science.gov (United States)

    Cerecedo, Doris; Mondragón, Ricardo; Cisneros, Bulmaro; Martínez-Pérez, Francisco; Martínez-Rojas, Dalila; Rendón, Alvaro

    2006-07-01

    Platelets are crucial at the site of vascular injury, adhering to the sub-endothelial matrix through receptors on their surface, leading to cell activation and aggregation to form a haemostatic plug. Platelets display focal adhesions as well as stress fibres to contract and facilitate expulsion of growth and pro-coagulant factors contained in the granules and to constrict the clot. The interaction of F-actin with different actin-binding proteins determines the properties and composition of the focal adhesions. Recently, we demonstrated the presence of dystrophin-associated protein complex corresponding to short dystrophin isoforms (Dp71d and Dp71) and the uthophin gene family (Up400 and Up71), which promote shape change, adhesion, aggregation, and granule centralisation. To elucidate participation of both complexes during the platelet adhesion process, their potential association with integrin beta-1 fraction and the focal adhesion system (alpha-actinin, vinculin and talin) was evaluated by immunofluorescence and immunoprecipitation assays. It was shown that the short dystrophin-associated protein complex participated in stress fibre assembly and in centralisation of cytoplasmic granules, while the utrophin-associated protein complex assembled and regulated focal adhesions. The simultaneous presence of dystrophin and utrophin complexes indicates complementary structural and signalling mechanisms to the actin network, improving the platelet haemostatic role.

  11. Amygdalin influences bladder cancer cell adhesion and invasion in vitro.

    Directory of Open Access Journals (Sweden)

    Jasmina Makarević

    Full Text Available The cyanogenic diglucoside amygdalin, derived from Rosaceae kernels, is employed by many patients as an alternative anti-cancer treatment. However, whether amygdalin indeed acts as an anti-tumor agent is not clear. Metastasis blocking properties of amygdalin on bladder cancer cell lines was, therefore, investigated. Amygdalin (10 mg/ml was applied to UMUC-3, TCCSUP or RT112 bladder cancer cells for 24 h or for 2 weeks. Tumor cell adhesion to vascular endothelium or to immobilized collagen as well as tumor cell migration was examined. Effects of drug treatment on integrin α and β subtypes, on integrin-linked kinase (ILK and total and activated focal adhesion kinase (FAK were also determined. Integrin knock-down was carried out to evaluate integrin influence on migration and adhesion. A 24 h or 2 week amygdalin application distinctly reduced tumor cell adhesion and migration of UMUC-3 and RT112 cells. TCCSUP adhesion was also reduced, but migration was elevated under amygdalin. Integrin subtype expression was significantly and specifically altered by amygdalin depending on the cell line. ILK was moderately, and activated FAK strongly, lost in all tumor cell lines in the presence of amygdalin. Knock down of β1 integrin caused a significant decrease in both adhesion and migration of UMUC-3 cells, but a significant increase in TCCSUP adhesion. Knock down of β4 integrin caused a significant decrease in migration of RT112 cells. Since the different actions of amygdalin on the different cell lines was mirrored by β1 or β4 knock down, it is postulated that amygdalin influences adhesion and migratory properties of bladder cancer cells by modulating β1 or β4 integrin expression. The amygdalin induced increase in TCCSUP migratory behavior indicates that any anti-tumor benefits from amygdalin (seen with the other two cell lines may depend upon the cancer cell type.

  12. Optimizing Adhesive Design by Understanding Compliance.

    Science.gov (United States)

    King, Daniel R; Crosby, Alfred J

    2015-12-23

    Adhesives have long been designed around a trade-off between adhesive strength and releasability. Geckos are of interest because they are the largest organisms which are able to climb utilizing adhesive toepads, yet can controllably release from surfaces and perform this action over and over again. Attempting to replicate the hierarchical, nanoscopic features which cover their toepads has been the primary focus of the adhesives field until recently. A new approach based on a scaling relation which states that reversible adhesive force capacity scales with (A/C)(1/2), where A is the area of contact and C is the compliance of the adhesive, has enabled the creation of high strength, reversible adhesives without requiring high aspect ratio, fibrillar features. Here we introduce an equation to calculate the compliance of adhesives, and utilize this equation to predict the shear adhesive force capacity of the adhesive based on the material components and geometric properties. Using this equation, we have investigated important geometric parameters which control force capacity and have shown that by controlling adhesive shape, adhesive force capacity can be increased by over 50% without varying pad size. Furthermore, we have demonstrated that compliance of the adhesive far from the interface still influences shear adhesive force capacity. Utilizing this equation will allow for the production of adhesives which are optimized for specific applications in commercial and industrial settings.

  13. Role of attractive forces in determining the equilibrium structure and dynamics of simple liquids

    DEFF Research Database (Denmark)

    Toxværd, Søren

    2015-01-01

    Molecular Dynamics simulations of a Lennard-Jones system with different range of attraction show that the attractive forces modify the radial distribution of the particles. For condensed liquids only, the forces within the the first coordination shell (FCS) are important, but for gases and moderate...... condensed fluids, even the attractive forces outside the FCS play a role. The changes in the distribution caused by neglecting the attractive forces, lead to a too high pressure. The weak long-range attractions damp the dynamics and the diffusion of the particles in gas-, super critical fluid- and in liquid...

  14. DETERMINATION OF FRICTION PERFORMANCE INFLUENCE IN THE SYSTEM "BODY–BOGIE" ON THE FREIGHT CAR DYNAMICS

    Directory of Open Access Journals (Sweden)

    S. V. Myamlin

    2014-03-01

    Full Text Available Purpose. The main requirements for the design of a new generation of cars, according to the Program of rolling stock renovation, are the requirements reducing the operating costs and increasing the cost-effectiveness of their use, taking into account the achievements of scientific and technical thought. Due to the urgency of this subject the paper is devoted to the study of the friction coefficient influence in the bearing connection «center plate – center bowl – bearers»of freight cars on their main dynamic parameters – coefficients of horizontal and vertical dynamics, body acceleration, frame strength, derailment stability factor. Methodology. The study was conducted by numerical integration and mathematical modeling of the freight car dynamic loading using the software package «Dynamics of Rail Vehicles» («DYNRAIL». Findings. Investigations have shown that the safety movement parameters are influenced by both the friction parameters in bearing connection «center plate – center bowl – bearers» of freight cars in empty and loaded state with bogies TSNII-X3 (model 18-100. Effect have other components of freight car dynamics, namely: radii of curved track sections, height of outer rail, etc. Originality. The author investigated the friction influence on the car dynamic loading using new approaches to solving the problem of predicting the rolling stock dynamics. Prediction was carried out on the basis of significantly updated theoretical material that covers all history of the friction theory and includes the results of recent experimental studies because of the speed on the straights and curves of small-and medium-range sections of the road.Practical value. The obtained results have practical orientation. During the research and after modeling with the improved method of accounting of friction processes dependencies of main dynamic parameters of a four-freight gondola on the value of the friction coefficient in the "body

  15. Motion of Elastic Microcapsules on Compliant Surfaces with Adhesive Ligands

    Science.gov (United States)

    Maresov, Egor; Kolmakov, German; Balazs, Anna

    2011-03-01

    By integrating mesoscale models for hydrodynamics, micromechanics and adhesion, we examine the fluid driven motion of elastic microcapsules on compliant surfaces. The capsules, modeled as three-dimensional fluid-filled elastic shells, represent polymeric microcapsules or biological cells. Our combined integrated Lattice Boltzmann model/Lattice spring model (LBM/LSM) approach allows for a dynamic interaction between the elastic capsule's wall and surrounding fluid. To capture the interaction between the shell and the surface, we adopt the Bell model, used previously to describe the interaction of biological cell like leukocytes rolling on surfaces under the influence of an imposed shear. The surface of the microcapsule contains receptors with an affinity to adhesive ligands of the substrate. We examine how the parameters of adhesion and rigidity of the capsules and the substrate affect movement of the capsules. The findings provide guidelines for creating smart surfaces that could regulate the microcapsules' motion.

  16. Innovative Electrostatic Adhesion Technologies

    Science.gov (United States)

    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

  17. Innovative Electrostatic Adhesion Technologies

    Science.gov (United States)

    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

  18. Failure strength prediction for adhesively bonded single lap joints

    Science.gov (United States)

    Rahman, Niat Mahmud

    experimentally measured crack tip opening angles (CTOA) using DCB tests and CTOAs extracted from FEA using SLJs at failure loads follow similar trend when adhesive thickness was considered as variable. A factor was proposed to accommodate differences. Proposed method was also adopted for SLJs with overlap length as variable. Reasons for discrepancies were identified for such case. For generating adherend failure, graphite fiber epoxy composite was used as adherend. To avoid singularity, an area based approach was adopted. It is considered that failure within composite adherend occurs when size of the damaged zone reaches a critical value. This value was determined using test data and then FEA of SLJ. Using this hypothesis, various strength of material based failure models were tested for SLJs with different geometries. According to the study, Azzi-Tsai model works well for SLJs having different geometric parameters. Only composite failure parallel to interface and within the first ply was considered here.

  19. Elastocapilllarity in insect adhesion: the case of beetle adhesive hair

    Science.gov (United States)

    Gernay, Sophie; Gilet, Tristan; Lambert, Pierre; Federle, Walter

    2014-11-01

    The feet of many insects are covered with dense arrays of hair-like structures called setae. Liquid capillary bridges at the tip of these micrometric structures are responsible for the controlled adhesion of the insect on a large variety of substrates. The resulting adhesion force can exceed several times the body weight of the insect. The high aspect-ratio of setae suggests that flexibility is a key ingredient in this capillary-based adhesion mechanism. There is indeed a strong coupling between their elastic deformation and the shape of the liquid meniscus. In this experimental work, we observe and quantify the local deflection of dock beetle seta tips under perpendicular loading using interference microscopy. Our results are then interpreted in the light of an analytic model of elastocapillarity. This research has been funded by the FRIA/FNRS and the Interuniversity Attraction Poles Programme (IAP 7/38 MicroMAST) initiated by the Belgian Science Policy Office.

  20. Fractal dimensions of soy protein nanoparticle aggregates determined by dynamic mechanical method

    Science.gov (United States)

    The fractal dimension of the protein aggregates can be estimated by dynamic mechanical methods when the particle aggregates are imbedded in a polymer matrix. Nanocomposites were formed by mixing hydrolyzed soy protein isolate (HSPI) nanoparticle aggregates with styrene-butadiene (SB) latex, followe...

  1. Ionosphere/thermosphere heating determined from dynamic magnetosphere-ionosphere/thermosphere coupling

    Science.gov (United States)

    Tu, Jiannan; Song, Paul; Vasyliūnas, Vytenis M.

    2011-09-01

    Ionosphere/thermosphere heating driven by magnetospheric convection is investigated through a three-fluid inductive (including Faraday's law) approach to describing magnetosphere-ionosphere/thermosphere coupling, for a 1-D stratified ionosphere/thermosphere in this initial study. It is shown that the response of the ionosphere/thermosphere and thus the heating is dynamic and height-dependent. The heating is essentially frictional in nature rather than Joule heating as commonly assumed. The heating rate reaches a quasi-steady state after about 25 Alfvén travel times. During the dynamic period, the heating can be enhanced and displays peaks at multiple times due to wave reflections. The dynamic heating rate can be more than twice greater than the quasi-steady state value. The heating is strongest in the E-layer but the heating rate per unit mass is concentrated around the F-layer peak height. This implies a potential mechanism of driving O+ upflow from O+ rich F-layer. It is shown that the ionosphere/thermosphere heating caused by the magnetosphere-ionosphere coupling can be simply evaluated through the relative velocity between the plasma and neutrals without invoking field-aligned currents, ionospheric conductance, and electric field. The present study provides understanding of the dynamic magnetosphere-ionosphere/thermosphere coupling from the ionospheric/thermospheric view in addition to magnetospheric perspectives.

  2. GABA[subscript A] Receptors Determine the Temporal Dynamics of Memory Retention

    Science.gov (United States)

    McNally, Gavan P.; Augustyn, Katarzyna A.; Richardson, Rick

    2008-01-01

    Four experiments studied the role of GABA[subscript A] receptors in the temporal dynamics of memory retention. Memory for an active avoidance response was a nonmonotonic function of the retention interval. When rats were tested shortly (2 min) or some time (24 h) after training, retention was excellent, but when they were tested at intermediate…

  3. Application of Computational Fluid Dynamics in the problems of determining the aerodynamic characteristics of the helicopter

    OpenAIRE

    Andrei Batrakov; Lyaisan Garipova; Aleksandr Kysumov; George Barakos

    2014-01-01

    In this article, computational Fluid Dynamics is used to study the complex interactions between the rotor and fuselage of the helicopter. Helicopter flows have been under investigation using isolated fuselage models, actuator disks as well as complete rotor-fuselage configurations. The paper highlights the flow detail that can be available to modern helicopter engineers equipped with modern software and computer clusters.

  4. Tool for a configurable integrated circuit that uses determination of dynamic power consumption

    Science.gov (United States)

    French, Matthew C. (Inventor); Wang, Li (Inventor); Agarwal, Deepak (Inventor); Davoodi, Azadeh (Inventor)

    2011-01-01

    A configurable logic tool that allows minimization of dynamic power within an FPGA design without changing user-entered specifications. The minimization of power may use minimized clock nets as a first order operation, and a second order operation that minimizes other factors, such as area of placement, area of clocks and/or slack.

  5. A dynamic approach to the determinants of immigrants’ language proficiency : the United States, 1980-2000

    NARCIS (Netherlands)

    Tubergen, F.A. van; Kalmijn, M.

    2009-01-01

    This article proposes a dynamic perspective on immigrants’ language proficiency. Hypotheses are formulated about immigrants’ language skills at arrival and about the speed with which immigrants learn the language thereafter. It pools data from the 1980, 1990, and 2000 U.S. Censuses, and uses a synth

  6. A novel technique for determining dynamic fracture toughness in sub- sized specimens

    Energy Technology Data Exchange (ETDEWEB)

    Couque, H.; Hudak, S.J. Jr.; Leung, C.P.; Dexter, R.J. (Southwest Research Inst., San Antonio, TX (United States))

    1993-02-01

    In order to perform structural reliability assessments, utilities need to characterize fracture properties from small specimens-not only for economic reasons but because in many situations only a small quantity of material is available. This report presents a novel experimental-analytic procedure to measure dynamic fracture toughness properties of steel using small specimens.

  7. Photo-dynamical mass determination of the multi-planetary system K2-19

    CERN Document Server

    Barros, S C C; Demangeon, O; Tsantaki, M; Santerne, A; Armstrong, D J; Barrado, D; Brown, D; Deleuil, M; Lillo-Box, J; Osborn, H; Pollacco, D; Abe, L; Andre, P; Bendjoya, P; Boisse, I; Bonomo, A S; Bouchy, F; Bruno, G; Cerda, J Rey; Courcol, B; Díaz, R F; Hébrard, G; Kirk, J; Lachurié, J C; Lam, K W F; Martinez, P; McCormac, J; Moutou, C; Rajpurohit, A; Rivet, J -P; Spake, J; Suarez, O; Toublanc, D; Walker, S R

    2015-01-01

    K2-19 is the second multi-planetary system discovered with K2 observations. The system is composed of two Neptune size planets close to the 3:2 mean-motion resonance. To better characterise the system we obtained two additional transit observations of K2-19b and five additional radial velocity observations. These were combined with K2 data and fitted simultaneously with the system dynamics (photo-dynamical model) which increases the precision of the transit time measurements. The higher transit time precision allows us to detect the chopping signal of the dynamic interaction of the planets that in turn permits to uniquely characterise the system. Although the reflex motion of the star was not detected, dynamic modelling of the system allowed us to derive planetary masses of $M_b= 44 \\pm 12\\, M_{\\oplus}$ and $M_c = 15.9 \\pm 7.0\\, M_{\\oplus}$ for the inner and the outer planets respectively, leading to densities close to Uranus. We also show that our method allows the derivation of mass ratios using only the 80...

  8. feedback between population and evolutionary dynamics determines the fate of social microbial populations.

    Directory of Open Access Journals (Sweden)

    Alvaro Sanchez

    Full Text Available The evolutionary spread of cheater strategies can destabilize populations engaging in social cooperative behaviors, thus demonstrating that evolutionary changes can have profound implications for population dynamics. At the same time, the relative fitness of cooperative traits often depends upon population density, thus leading to the potential for bi-directional coupling between population density and the evolution of a cooperative trait. Despite the potential importance of these eco-evolutionary feedback loops in social species, they have not yet been demonstrated experimentally and their ecological implications are poorly understood. Here, we demonstrate the presence of a strong feedback loop between population dynamics and the evolutionary dynamics of a social microbial gene, SUC2, in laboratory yeast populations whose cooperative growth is mediated by the SUC2 gene. We directly visualize eco-evolutionary trajectories of hundreds of populations over 50-100 generations, allowing us to characterize the phase space describing the interplay of evolution and ecology in this system. Small populations collapse despite continual evolution towards increased cooperative allele frequencies; large populations with a sufficient number of cooperators "spiral" to a stable state of coexistence between cooperator and cheater strategies. The presence of cheaters does not significantly affect the equilibrium population density, but it does reduce the resilience of the population as well as its ability to adapt to a rapidly deteriorating environment. Our results demonstrate the potential ecological importance of coupling between evolutionary dynamics and the population dynamics of cooperatively growing organisms, particularly in microbes. Our study suggests that this interaction may need to be considered in order to explain intraspecific variability in cooperative behaviors, and also that this feedback between evolution and ecology can critically affect the

  9. Adhesion and friction characteristics of carbon nanotube arrays

    International Nuclear Information System (INIS)

    There has been a great deal of interest in understanding, design and fabrication of bio-mimetic and bio-inspired adhesives in recent years. In this paper we present theoretical investigations on adhesion, friction behaviors and characteristics of fibrillar arrays composed of noninteracting carbon nanotubes for bio-inspired dry adhesives. Contact, compression, subsequent pulling off and dry sliding friction simulations were performed. It is demonstrated that there are two different adhesion forces during pull off. Static friction force values are in between 40 and 60 N cm−2 at different loads and they are significantly larger than the normal adhesion forces. Dynamic friction force and load are anisotropic and they depend on the direction of the motion. It is also found that friction force values and friction coefficients decrease although contact length and contact area increase when the loads are high. This is due to the arms of the nanotubes which bend significantly and act as stiffer springs at high loads. (paper)

  10. Capillarity-based switchable adhesion.

    Science.gov (United States)

    Vogel, Michael J; Steen, Paul H

    2010-02-23

    Drawing inspiration from the adhesion abilities of a leaf beetle found in nature, we have engineered a switchable adhesion device. The device combines two concepts: The surface tension force from a large number of small liquid bridges can be significant (capillarity-based adhesion) and these contacts can be quickly made or broken with electronic control (switchable). The device grabs or releases a substrate in a fraction of a second via a low-voltage pulse that drives electroosmotic flow. Energy consumption is minimal because both the grabbed and released states are stable equilibria that persist with no energy added to the system. Notably, the device maintains the integrity of an array of hundreds to thousands of distinct interfaces during active reconfiguration from droplets to bridges and back, despite the natural tendency of the liquid toward coalescence. We demonstrate the scaling of adhesion strength with the inverse of liquid contact size. This suggests that strengths approaching those of permanent bonding adhesives are possible as feature size is scaled down. In addition, controllability is fast and efficient because the attachment time and required voltage also scale down favorably. The device features compact size, no solid moving parts, and is made of common materials.

  11. Quantitative multicolor compositional imaging resolves molecular domains in cell-matrix adhesions.

    Directory of Open Access Journals (Sweden)

    Eli Zamir

    Full Text Available BACKGROUND: Cellular processes occur within dynamic and multi-molecular compartments whose characterization requires analysis at high spatio-temporal resolution. Notable examples for such complexes are cell-matrix adhesion sites, consisting of numerous cytoskeletal and signaling proteins. These adhesions are highly variable in their morphology, dynamics, and apparent function, yet their molecular diversity is poorly defined. METHODOLOGY/PRINCIPAL FINDINGS: We present here a compositional imaging approach for the analysis and display of multi-component compositions. This methodology is based on microscopy-acquired multicolor data, multi-dimensional clustering of pixels according to their composition similarity and display of the cellular distribution of these composition clusters. We apply this approach for resolving the molecular complexes associated with focal-adhesions, and the time-dependent effects of Rho-kinase inhibition. We show here compositional variations between adhesion sites, as well as ordered variations along the axis of individual focal-adhesions. The multicolor clustering approach also reveals distinct sensitivities of different focal-adhesion-associated complexes to Rho-kinase inhibition. CONCLUSIONS/SIGNIFICANCE: Multicolor compositional imaging resolves "molecular signatures" characteristic to focal-adhesions and related structures, as well as sub-domains within these adhesion sites. This analysis enhances the spatial information with additional "contents-resolved" dimensions. We propose that compositional imaging can serve as a powerful tool for studying complex multi-molecular assemblies in cells and for mapping their distribution at sub-micron resolution.

  12. Lap Shear and Impact Testing of Ochre and Beeswax in Experimental Middle Stone Age Compound Adhesives.

    Science.gov (United States)

    Kozowyk, P R B; Langejans, G H J; Poulis, J A

    2016-01-01

    The production of compound adhesives using disparate ingredients is seen as some of the best evidence of advanced cognition outside of the use of symbolism. Previous field and laboratory testing of adhesives has shown the complexities involved in creating an effective Middle Stone Age glue using Acacia gum. However, it is currently unclear how efficient different adhesive recipes are, how much specific ingredients influence their performance, and how difficult it may have been for those ingredients to be combined to maximum effect. We conducted a series of laboratory-based lap shear and impact tests, following modern adhesion testing standards, to determine the efficacy of compound adhesives, with particular regard to the ingredient ratios. We tested rosin (colophony) and gum adhesives, containing additives of beeswax and ochre in varying ratios. During both lap shear and impact tests compound rosin adhesives performed better than single component rosin adhesives, and pure acacia gum was the strongest. The large difference in performance between each base adhesive and the significant changes in performance that occur due to relatively small changes in ingredient ratios lend further support to the notion that high levels of skill and knowledge were required to consistently produce the most effective adhesives.

  13. Determination of SMES capacity to enhance the dynamic stability of power system

    Energy Technology Data Exchange (ETDEWEB)

    Shi, J., E-mail: shijing_hust@126.co [R and D Center of Applied Superconductivity, Huazhong University of Science and Technology, Wuhan (China); Tang, Y. [R and D Center of Applied Superconductivity, Huazhong University of Science and Technology, Wuhan (China); Dai, T. [Department of Information and Electrical Engineering, Shandong University of Science and Technology , Qingdao (China); Ren, L.; Li, J.; Cheng, S. [R and D Center of Applied Superconductivity, Huazhong University of Science and Technology, Wuhan (China)

    2010-11-01

    This paper proposes the principle of SMES capacity determination for power system stable operation. Adopting the energy function method, the mechanism of SMES damping power oscillation in the classical single-machine infinite-bus (SMIB) system is analyzed. The released kinetic energy during disturbance is the original of power system oscillation, which is taken as the principle of SMES capacity determination. Then, the influence of fault type, fault position, and fault clearing time on the SMES capacity determination are discussed. Using MATLAB simulation, the principle of SMES capacity determination is evaluated.

  14. Bloodstain Pattern Analysis: implementation of a fluid dynamic model for position determination of victims

    NARCIS (Netherlands)

    N. Laan; K.G. de Bruin; D. Slenter; J. Wilhelm; M. Jermy; D. Bonn

    2015-01-01

    Bloodstain Pattern Analysis is a forensic discipline in which, among others, the position of victims can be determined at crime scenes on which blood has been shed. To determine where the blood source was investigators use a straight-line approximation for the trajectory, ignoring effects of gravity

  15. LDA and molecular dynamics determination of Ag deposition onto (1 0 0) surfaces in silicon

    Energy Technology Data Exchange (ETDEWEB)

    Mazzone, A.M

    2003-03-20

    This study analyzes the effects of the surface morphology on the deposition of Ag onto Si using LDA and isothermal molecular dynamics. The (1 0 0) silicon surface has either a bulk termination or the dimerization pattern experimentally observed. Small clusters representing a section of these surfaces have been used in LDA calculations to find preferred adsorption sites. Isothermal molecular dynamics describe the motions of the diffusing adatoms in a temperature range from T=10 to 1000 K. Both calculations indicate that Ag and Si do not mix and the deposited structure is formed by linear chains located in the trench between surface atoms. However, MD calculations show that, due to the relaxation of the surface and to thermal lattice vibrations, the stable state of the deposited atoms may considerably differ from the one calculated from LDA. This result has both a practical and a methodological significance.

  16. Determination of the dynamics of temperature variation in a model object by acoustic thermography

    Science.gov (United States)

    Anosov, A. A.; Belyaev, R. V.; Vilkov, V. A.; Kazanskiĭ, A. S.; Mansfel'D, A. D.; Sharakshané, A. S.

    2008-07-01

    An experiment on monitoring the dynamics of internal temperature variation in a model object by the acoustic thermography method is carried out. The measurements were performed in a cell filled with an aqueous solution of glycerol, into which a plasticine object was placed. Thermal acoustic radiation of the object was measured in the course of its heating and cooling. Two bars of acoustic thermometers positioned on two sides of the object were used for this purpose. The results of measurements allowed the reconstruction of the dynamics of the varying two-dimensional distribution of in-depth temperature. The position of the heated region, its temperature, and its characteristic size are estimated. In addition, an estimate is obtained for the absorption coefficient.

  17. Application of Computational Fluid Dynamics in the problems of determining the aerodynamic characteristics of the helicopter

    Directory of Open Access Journals (Sweden)

    Andrei Batrakov

    2014-04-01

    Full Text Available In this article, computational Fluid Dynamics is used to study the complex interactions between the rotor and fuselage of the helicopter. Helicopter flows have been under investigation using isolated fuselage models, actuator disks as well as complete rotor-fuselage configurations. The paper highlights the flow detail that can be available to modern helicopter engineers equipped with modern software and computer clusters.

  18. Lattice dynamics of polyaniline and poly(p-pyridyl vinyline) : first-principles determination.

    OpenAIRE

    Zheng, G.; Clark, S J; Brand, S; Abram, R A

    2006-01-01

    First-principles density functional studies of the dynamical properties of the conjugated polymers polyaniline and poly(p-pyridyl vinyline) are presented in this work. We have employed linear response within density functional perturbation theory, as implemented in the CASTEP code, to investigate the Born effective charges, polarizabilities, and vibrational properties. With regard to the last, we have calculated the vibrational frequencies and made assignments of the m...

  19. Telomeric overhang length determines structural dynamics and accessibility to telomerase and ALT associated proteins

    OpenAIRE

    Hwang, Helen; Kreig, Alex; Calvert, Jacob; Lormand, Justin; Kwon, Yongho; Daley, James M.; Sung, Patrick; Opresko, Patricia L.; Myong, Sua

    2014-01-01

    The G-rich single stranded DNA at the 3′ end of human telomeres can self-fold into G-quaduplex (GQ). However, telomere lengthening by telomerase or the recombination-based alternative lengthening of telomere (ALT) mechanism requires protein loading on the overhang. Using single molecule fluorescence spectroscopy we discovered that lengthening the telomeric overhang also increased the rate of dynamic exchanges between structural conformations. Overhangs with five to seven TTAGGG repeats, compa...

  20. Determination of optimum rotational speed of heterogeneous catalytic reactor using computational fluid dynamic

    OpenAIRE

    Rungrote Kokoo; Phavanee Narataruksa; Karn Pana-Suppamassadu; Sabaithip Tungkamani

    2008-01-01

    Solid suspension in a stirrer tank reactor is relevant in many chemical process industries. For a heterogeneous catalyticreactor, the degree of solid suspension is a crucial parameter in the design and scaling-up processes. The suspension of solid catalysts at a minimum impeller speed can reduce the operating cost of processes. To ensure optimum conditions for suspension, a 3D simulation technique by Computational Fluid Dynamic (CFD) was used to study flow characteristics in a heterogeneous c...

  1. Effect of Curing Procedure on the Properties of Copper-Powder-Filled Conductive Adhesives

    Institute of Scientific and Technical Information of China (English)

    ZHENG Xiaoling; ZHANG Lulu; YOU Min; WU Jianhao; YU Haizhou; YANG Derong; MAO Yuping

    2008-01-01

    By means of testing the shear strength with single lap joint, measuring electrical resistivity for cured products and the curing strain with strain gauges, the effect of cure parameters on the properties of HT1012 conductive adhesive filled with copper powder was investigated, and the residual stress in the conductive adhesives was also estimated. The experimental results show that the properties such as shear strength of the adhesives, electrical resistivity of products as well as the residual stress of cured HT1012 copper-filled conductive adhesive were evidently affected by curing temperature and time. The diagrams of scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) were also used to determine the properties. The higher mechanical property was achieved under the condition of curing the adhesive 3h at 60℃ as the density of the hydrogen links or linkages existed in the adhesive was relatively higher and the lower electrical resistivity occurred at 80℃.

  2. Quantitative scanning thermal microscopy based on determination of thermal probe dynamic resistance.

    Science.gov (United States)

    Bodzenta, J; Juszczyk, J; Chirtoc, M

    2013-09-01

    Resistive thermal probes used in scanning thermal microscopy provide high spatial resolution of measurement accompanied with high sensitivity to temperature changes. At the same time their sensitivity to variations of thermal conductivity of a sample is relatively low. In typical dc operation mode the static resistance of the thermal probe is measured. It is shown both analytically and experimentally that the sensitivity of measurement can be improved by a factor of three by measuring the dynamic resistance of a dc biased probe superimposed with small ac current. The dynamic resistance can be treated as a complex value. Its amplitude represents the slope of the static voltage-current U-I characteristic for a given I while its phase describes the delay between the measured ac voltage and applied ac current component in the probe. The phase signal also reveals dependence on the sample thermal conductivity. Signal changes are relatively small but very repeatable. In contrast, the difference between dynamic and static resistance has higher sensitivity (the same maximum value as that of the 2nd and 3rd harmonics), and also much higher amplitude than higher harmonics. The proposed dc + ac excitation scheme combines the benefits of dc excitation (mechanical stability of probe-sample contact, average temperature control) with those of ac excitation (base-line stability, rejection of ambient temperature influence, high sensitivity, lock-in signal processing), when the experimental conditions prohibit large ac excitation. PMID:24089831

  3. A miniaturized, high frequency mechanical scanner for high speed atomic force microscope using suspension on dynamically determined points

    Energy Technology Data Exchange (ETDEWEB)

    Herfst, Rodolf; Dekker, Bert; Witvoet, Gert; Crowcombe, Will; Lange, Dorus de [Department of Optomechatronics, Netherlands Organization for Applied Scientific Research, TNO, Delft (Netherlands); Sadeghian, Hamed, E-mail: hamed.sadeghianmarnani@tno.nl, E-mail: h.sadeghianmarnani@tudelft.nl [Department of Optomechatronics, Netherlands Organization for Applied Scientific Research, TNO, Delft (Netherlands); Department of Precision and Microsystems Engineering, Delft University of Technology, Delft (Netherlands)

    2015-11-15

    One of the major limitations in the speed of the atomic force microscope (AFM) is the bandwidth of the mechanical scanning stage, especially in the vertical (z) direction. According to the design principles of “light and stiff” and “static determinacy,” the bandwidth of the mechanical scanner is limited by the first eigenfrequency of the AFM head in case of tip scanning and by the sample stage in terms of sample scanning. Due to stringent requirements of the system, simply pushing the first eigenfrequency to an ever higher value has reached its limitation. We have developed a miniaturized, high speed AFM scanner in which the dynamics of the z-scanning stage are made insensitive to its surrounding dynamics via suspension of it on specific dynamically determined points. This resulted in a mechanical bandwidth as high as that of the z-actuator (50 kHz) while remaining insensitive to the dynamics of its base and surroundings. The scanner allows a practical z scan range of 2.1 μm. We have demonstrated the applicability of the scanner to the high speed scanning of nanostructures.

  4. Determination of Fatty Acid Metabolism with Dynamic 11C-Palmitate Positron Emission Tomography of Mouse Heart In Vivo

    Science.gov (United States)

    Li, Yinlin; Huang, Tao; Zhang, Xinyue; Zhong, Min; Walker, Natalie N.; He, Jiang; Berr, Stuart S.; Keller, Susanna R.; Kundu, Bijoy K.

    2015-01-01

    The goal of this study was to establish a quantitative method for measuring FA metabolism with partial volume (PV) and spill-over (SP) corrections using dynamic 11C-palmitate PET images of mouse heart in vivo. Methods Twenty-minute dynamic 11C-palmitate PET scans of four 18–20 week old male C57BL/6 mice under isoflurane anesthesia were performed using a Focus 120 PET scanner. A model corrected blood input function (MCIF), by which the input function with SP and PV corrections and the metabolic rate constants (k1−k5) are simultaneously estimated from the dynamic 11C-palmitate PET images of mouse hearts in a 4-compartment tracer kinetic model, was used to determine rates of myocardial FA oxidation (MFAO), myocardial FA esterification (MFAE), myocardial FA utilization (MFAU) and myocardial FA uptake (MFAUp). Results The MFAO thus measured in C57BL/6 mice was 375.03±43.83 nmoles/min/g. This compares well with the MFAO measured in perfused working C57BL/6 mouse hearts ex vivo of about 350 nmoles/g/min and 400 nmoles/min/g. Conclusions FA metabolism was measured for the first time in mouse heart in vivo using dynamic 11C-palmitate PET in a 4-compartment tracer kinetic model. MFAO obtained with this model were validated by results previously obtained with mouse hearts ex vivo. PMID:26462138

  5. Effect of thermal shock loadings on stability of dentin-composite polymer material adhesive interfaces

    Science.gov (United States)

    Bessudnova, Nadezda O.; Shlyapnikova, Olga A.; Venig, Sergey B.; Gribov, Andrey N.

    2015-03-01

    In the past several decades the problem of longevity and durability of adhesive interfaces between hard tooth tissues and composite resin-based materials are of great interest among dental researchers and clinicians. These parameters are partially determined by adhesive system mechanical properties. In the present research project nanoindentation has been examined to test hardness of dental adhesive systems. A series of laboratory experiments was performed to study the effect of light curing time and oxygen inhibition phenomenon on light-cured adhesive material hardness. An adhesive system AdperTM Single Bond (3M ESPE) was selected as a material for testing. The analysis of experimental data revealed that the maximum values of hardness were observed after the material had been light-cured for 20 seconds, as outlined in guidelines for polymerization time of the adhesive system. The experimental studies of oxygen inhibition influence on adhesive system hardness pointed out to the fact that the dispersive layer removal led to increase in adhesive system hardness. A long - time exposure of polymerized material of adhesive system at open air at room temperature resulted in no changes in its hardness, which was likely to be determined by the mutual effect of rival processes of air oxygen inhibition and directed light curing.

  6. A ring circuit for the determination of dynamic error rates in high-temperature superconductor RSFQ circuits

    International Nuclear Information System (INIS)

    We have designed and simulated a circuit for the experimental determination of the rate of dynamic switching errors in high-temperature superconductor RSFQ circuits. The proposal is that a series-connected pair of Josephson junctions is read out by SFQ pulses circulating in a ring-shaped Josephson transmission line at high frequency. Suitable bias currents determine the switching thresholds of the junction pair. By measuring the voltage across the transmission line, it is proposed that the occurrence of a switching error can be detected. The bit error rate can be determined from the mean time before false switching together with the SFQ circulation frequency. The circuit design allows measurements over a wide temperature range. (author)

  7. Effect of Heartwood and Sapwood Ratio on Adhesion Strength of Finished Wood Species

    Directory of Open Access Journals (Sweden)

    Turgay Ozdemir

    2015-01-01

    Full Text Available The objective of this study was to determine adhesion strength of samples from wood species coated with cellulose varnish as function of heartwood and sapwood ratio. Roughness of the specimens from four different species was measured employing stylus type equipment before they were coated with varnish. Pull-off testing unit was employed to determine adhesion strength of the samples. Based on the findings in this work it seems that no significant difference was determined between adhesion strength values of the samples prepared from heartwood and sapwood portions. The highest adhesion strength value of 2.62 N/mm2 was found for the beech samples sanded with 80-grit sand paper. Overall rougher surfaces of the samples resulted in higher adhesion strength between finish and substrate.

  8. A method for predicting critical load evaluating adhesion of coatings in scratch testing

    Institute of Scientific and Technical Information of China (English)

    CHEN Xi-fang(陈溪芳); YAN Mi(严密); YANG De-ren(杨德人); HIROSE Yukio

    2003-01-01

    In this paper based on the experiment principle of evaluating adhesion property by scratch testing, the peeling mechanism of thin films is discussed by applying contact theory and surface physics theory. A mathematical model predicting the critical load is proposed for calculating critical load as determined by scratch testing. The factors for correctly evaluating adhesion of coatings according to the experimental data are discussed.

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

    NARCIS (Netherlands)

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

    2011-01-01

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

  10. A method for predicting critical load evaluating adhesion of coatings in scratch testing

    Institute of Scientific and Technical Information of China (English)

    陈溪芳; 严密; 杨德人; HIROSEYukio

    2003-01-01

    In this paper based on the experiment principle of evaluating adhesion property by scratch testing, the peeling mechanism of thin films is discussed by applying contact theory and surface physics theory. A mathematical model predicting the critical load is proposed for calculating critical load as determined byscratch testing. The factors for correctly evaluating adhesion of coatings according to the experimental data arediscussed.

  11. Bacterial Adhesion Forces to Ag-Impregnated Contact Lens Cases and Transmission to Contact Lenses

    NARCIS (Netherlands)

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

    2013-01-01

    Purpose: To measure adhesion forces of Pseudomonas aeruginosa, Staphylococcus aureus, and Serratia marcescens to a rigid contact lens (CL), standard polypropylene, and Ag-impregnated lens cases using atomic force microscopy and determine bacterial transmission from lens case to CL. Methods: Adhesion

  12. Plasticizers increase adhesion of the deteriogenic fungus Aureobasidium pullulans to polyvinyl chloride

    NARCIS (Netherlands)

    Webb, JS; Van der Mei, HC; Nixon, M; Eastwood, IM; Greenhalgh, M; Read, SJ; Robson, GD; Handley, PS

    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

  13. Implementation of a methodology for determining elastic properties of lipid assemblies from molecular dynamics simulations

    OpenAIRE

    Johner, Niklaus; Harries, Daniel; Khelashvili, George

    2016-01-01

    Background The importance of the material properties of membranes for diverse cellular processes is well established. Notably, the elastic properties of the membrane, which depend on its composition, can directly influence membrane reshaping and fusion processes as well as the organisation and function of membrane proteins. Determining these properties is therefore key for a mechanistic understanding of how the cell functions. Results We have developed a method to determine the bending rigidi...

  14. NEXT GENERATION OF TELESCOPES OR DYNAMICS REQUIRED TO DETERMINE IF EXO-MOONS HAVE PROGRADE OR RETROGRADE ORBITS

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, Karen M.; Fujii, Yuka [Earth-Life Science Institute (WPI-ELSI), Tokyo Institute of Technology, Ookayama, Meguro district, Tokyo 152-8551 (Japan)

    2014-08-20

    We survey the methods proposed in the literature for detecting moons of extrasolar planets in terms of their ability to distinguish between prograde and retrograde moon orbits, an important tracer of the moon formation channel. We find that most moon detection methods, in particular, sensitive methods for detecting moons of transiting planets, cannot observationally distinguishing prograde and retrograde moon orbits. The prograde and retrograde cases can only be distinguished where the dynamical evolution of the orbit due to, e.g., three body effects is detectable, where one of the two cases is dynamically unstable, or where new observational facilities, which can implement a technique capable of differentiating the two cases, come online. In particular, directly imaged planets are promising targets because repeated spectral and photometric measurements, which are required to determine moon orbit direction, could also be conducted with the primary interest of characterizing the planet itself.

  15. NEXT GENERATION OF TELESCOPES OR DYNAMICS REQUIRED TO DETERMINE IF EXO-MOONS HAVE PROGRADE OR RETROGRADE ORBITS

    International Nuclear Information System (INIS)

    We survey the methods proposed in the literature for detecting moons of extrasolar planets in terms of their ability to distinguish between prograde and retrograde moon orbits, an important tracer of the moon formation channel. We find that most moon detection methods, in particular, sensitive methods for detecting moons of transiting planets, cannot observationally distinguishing prograde and retrograde moon orbits. The prograde and retrograde cases can only be distinguished where the dynamical evolution of the orbit due to, e.g., three body effects is detectable, where one of the two cases is dynamically unstable, or where new observational facilities, which can implement a technique capable of differentiating the two cases, come online. In particular, directly imaged planets are promising targets because repeated spectral and photometric measurements, which are required to determine moon orbit direction, could also be conducted with the primary interest of characterizing the planet itself

  16. Rotation Dynamics Do Not Determine the Unexpected Isotropy of Methyl Radical EPR Spectra.

    Science.gov (United States)

    Benetis, Nikolas P; Dmitriev, Yurij; Mocci, Francesca; Laaksonen, Aatto

    2015-09-01

    A simple first-principles electronic structure computation, further qc (quantum chemistry) computation, of the methyl radical gives three equal hf (hyperfine) couplings for the three protons with the unpaired electron. The corresponding dipolar tensors were notably rhombic and had different orientations and regular magnitude components, as they should, but what the overall A-tensor was seen by the electron spin is a different story! The final g = (2.002993, 2.002993, 2.002231) tensor and the hf coupling results obtained in vacuum, at the B3LYP/EPRIII level of theory clearly indicate that in particular the above A = (-65.19, -65.19, 62.54) MHz tensor was axial to a first approximation without considering any rotational dynamics for the CH3. This approximation was not applicable, however, for the trifluoromethyl CF3 radical, a heavier and nonplanar rotor with very anisotropic hf coupling, used here for comparison. Finally, a derivation is presented explaining why there is actually no need for the CH3 radicals to consider additional rotational dynamics in order for the electron to obtain an axially symmetric hf (hyperfine) tensor by considering the simultaneous dipolar couplings of the three protons. An additional consequence is an almost isotropic A-tensor for the electron spin of the CH3 radical. To the best of our knowledge, this point has not been discussed in the literature before. The unexpected isotropy of the EPR parameters of CH3 was solely attributed to the rotational dynamics and was not clearly separated from the overall symmetry of the species. The present theoretical results allowed a first explanation of the "forbidden" satellite lines in the CH3 EPR spectrum. The satellites are a fingerprint of the radical rotation, helping thus in distinguishing the CH3 reorientation from quantum rotation at very low temperatures. PMID:26262753

  17. Determination of light and strange quark masses from two-flavour dynamical lattice QCD

    International Nuclear Information System (INIS)

    We compute the light and strange quark masses ml =(mu+md)/2 and ms, respectively, in unquenched lattice QCD with Nf=2 flavours of light dynamical quarks. The renormalisation constants, which convert bare quark masses into renormalised quark masses, are computed nonperturbatively, including the effect of quark-line disconnected diagrams. We obtain mlMS-bar (2 GeV)=4.7(2)(3) MeV and msMS-bar (2 GeV)=119(5)(8) MeV, using r0=0.467 fm to set the scale

  18. Pulsatile microfluidics as an analytical tool for determining the dynamic characteristics of microfluidic systems

    DEFF Research Database (Denmark)

    Vedel, Søren; Olesen, Laurits Højgaard; Bruus, Henrik

    2010-01-01

    An understanding of all fluid dynamic time scales is needed to fully understand and hence exploit the capabilities of fluid flow in microfluidic systems. We propose the use of harmonically oscillating microfluidics as an analytical tool for the deduction of these time scales. Furthermore, we...... suggest the use of system-level equivalent circuit theory as an adequate theory of the behavior of the system. A novel pressure source capable of operation in the desired frequency range is presented for this generic analysis. As a proof of concept, we study the fairly complex system of water...

  19. [FTIR spectroscopic studies of facial prosthetic adhesives].

    Science.gov (United States)

    Kang, Biao; Yang, Qing-fang; Liang, Jian-feng; Zhao, Yi-min

    2008-10-01

    According to the composition of the traditional facial prosthetic adhesives, most of adhesives can be classified into two categories: acrylic polymer-based adhesive and silicone-based adhesive. In previous studies, measurements of various mechanical bond strengths were carried out, whereas the functional groups of the adhesives were evaluated seldom during the adhesion. In the present study the analysis of two facial prosthetic adhesives (Epithane and Secure Adhesive) was carried out by using infrared spectroscopy. Two adhesives in the form of fluid or semisolid were submitted to FTIR spectroscopy, respectively. The results showed that water and ammonia residue volatilized during the solidification of Epithane, and absorption peak reduction of carbonyl was due to the volatilization of acetate vinyl from Secure Adhesive. Similar silicone functional groups both in the silicone-based adhesive and in silicone elastomer could be the key to higher bond strength between silicone elastomer and skin with silicone-based adhesive. The position, shape of main absorption peaks of three adhesives didn't change, which showing that their main chemicals and basic structures didn't change during solidification. PMID:19123392

  20. Bi facial silicon solar cell study in modelling in frequency dynamic regime under multispectral illumination: Recombination parameters determination methods

    International Nuclear Information System (INIS)

    A bibliographic study on the techniques of characterization of silicon solar cell, diodes, massifs and silicon wafer are presented. The influence of the modulation frequency and recombination in volume and in surface phenomena of on the profiles of carriers' densities, photocurrent and photovoltage has been put in evidence. The study of surface recombination velocities permitted to show that the bi facial silicon solar cell of Back Surface Field type behaves like an ohmic contacts solar cell for modulation frequencies above 40 khz. pplicability in frequency dynamic regime in the frequency range [0 - 40 khz] of three techniques of steady state recombination parameters determination is shown. A technique of diffusion length determination, in the range of (200 Hz - 40 khz] is proposed. It rests on the measurement of the short circuit current phase that is compared with the theoretical curve of short circuit current phase. The intersection of the experimental short circuit current phase and the theoretical curve of short circuit current phase permits to get the minority carriers effective diffusion length. An equivalent electric model of a solar cell in frequency dynamic regime is proposed. A study in modelling of the bi facial solar cell shunt resistance and space charge zone capacity is led from a determination method of these parameters proposed in steady state. (Author

  1. Dynamics

    CERN Document Server

    Goodman, Lawrence E

    2001-01-01

    Beginning text presents complete theoretical treatment of mechanical model systems and deals with technological applications. Topics include introduction to calculus of vectors, particle motion, dynamics of particle systems and plane rigid bodies, technical applications in plane motions, theory of mechanical vibrations, and more. Exercises and answers appear in each chapter.

  2. Complementarity of PALM and SOFI for super-resolution live cell imaging of focal adhesions

    CERN Document Server

    Deschout, Hendrik; Sharipov, Azat; Szlag, Daniel; Feletti, Lely; Vandenberg, Wim; Dedecker, Peter; Hofkens, Johan; Leutenegger, Marcel; Lasser, Theo; Radenovic, Aleksandra

    2016-01-01

    Live cell imaging of focal adhesions requires a sufficiently high temporal resolution, which remains a challenging task for super-resolution microscopy. We have addressed this important issue by combining photo-activated localization microscopy (PALM) with super-resolution optical fluctuation imaging (SOFI). Using simulations and fixed cell focal adhesion images, we investigated the complementarity between PALM and SOFI in terms of spatial and temporal resolution. This PALM-SOFI framework was used to image focal adhesions in living cells, while obtaining a temporal resolution below 10 s. We visualized the dynamics of focal adhesions, and revealed local mean velocities around 190 nm per minute. The complementarity of PALM and SOFI was assessed in detail with a methodology that integrates a quantitative resolution and signal-to-noise metric. This PALM and SOFI concept provides an enlarged quantitative imaging framework, allowing unprecedented functional exploration of focal adhesions through the estimation of m...

  3. Aggrecan nanoscale solid-fluid interactions are a primary determinant of cartilage dynamic mechanical properties.

    Science.gov (United States)

    Nia, Hadi Tavakoli; Han, Lin; Bozchalooi, Iman Soltani; Roughley, Peter; Youcef-Toumi, Kamal; Grodzinsky, Alan J; Ortiz, Christine

    2015-03-24

    Poroelastic interactions between interstitial fluid and the extracellular matrix of connective tissues are critical to biological and pathophysiological functions involving solute transport, energy dissipation, self-stiffening and lubrication. However, the molecular origins of poroelasticity at the nanoscale are largely unknown. Here, the broad-spectrum dynamic nanomechanical behavior of cartilage aggrecan monolayer is revealed for the first time, including the equilibrium and instantaneous moduli and the peak in the phase angle of the complex modulus. By performing a length scale study and comparing the experimental results to theoretical predictions, we confirm that the mechanism underlying the observed dynamic nanomechanics is due to solid-fluid interactions (poroelasticity) at the molecular scale. Utilizing finite element modeling, the molecular-scale hydraulic permeability of the aggrecan assembly was quantified (kaggrecan = (4.8 ± 2.8) × 10(-15) m(4)/N·s) and found to be similar to the nanoscale hydraulic permeability of intact normal cartilage tissue but much lower than that of early diseased tissue. The mechanisms underlying aggrecan poroelasticity were further investigated by altering electrostatic interactions between the molecule's constituent glycosaminoglycan chains: electrostatic interactions dominated steric interactions in governing molecular behavior. While the hydraulic permeability of aggrecan layers does not change across species and age, aggrecan from adult human cartilage is stiffer than the aggrecan from newborn human tissue. PMID:25758717

  4. Local sharing as a predominant determinant of synaptic matrix molecular dynamics.

    Directory of Open Access Journals (Sweden)

    Shlomo Tsuriel

    2006-09-01

    Full Text Available Recent studies suggest that central nervous system synapses can persist for weeks, months, perhaps lifetimes, yet little is known as to how synapses maintain their structural and functional characteristics for so long. As a step toward a better understanding of synaptic maintenance we examined the loss, redistribution, reincorporation, and replenishment dynamics of Synapsin I and ProSAP2/Shank3, prominent presynaptic and postsynaptic matrix molecules, respectively. Fluorescence recovery after photobleaching and photoactivation experiments revealed that both molecules are continuously lost from, redistributed among, and reincorporated into synaptic structures at time-scales of minutes to hours. Exchange rates were not affected by inhibiting protein synthesis or proteasome-mediated protein degradation, were accelerated by stimulation, and greatly exceeded rates of replenishment from somatic sources. These findings indicate that the dynamics of key synaptic matrix molecules may be dominated by local protein exchange and redistribution, whereas protein synthesis and degradation serve to maintain and regulate the sizes of local, shared pools of these proteins.

  5. Chromatin Dynamics During DNA Replication and Uncharacterized Replication Factors determined by Nascent Chromatin Capture (NCC) Proteomics

    Science.gov (United States)

    Alabert, Constance; Bukowski-Wills, Jimi-Carlo; Lee, Sung-Bau; Kustatscher, Georg; Nakamura, Kyosuke; de Lima Alves, Flavia; Menard, Patrice; Mejlvang, Jakob; Rappsilber, Juri; Groth, Anja

    2014-01-01

    SUMMARY To maintain genome function and stability, DNA sequence and its organization into chromatin must be duplicated during cell division. Understanding how entire chromosomes are copied remains a major challenge. Here, we use Nascent Chromatin Capture (NCC) to profile chromatin proteome dynamics during replication in human cells. NCC relies on biotin-dUTP labelling of replicating DNA, affinity-purification and quantitative proteomics. Comparing nascent chromatin with mature post-replicative chromatin, we provide association dynamics for 3995 proteins. The replication machinery and 485 chromatin factors like CAF-1, DNMT1, SUV39h1 are enriched in nascent chromatin, whereas 170 factors including histone H1, DNMT3, MBD1-3 and PRC1 show delayed association. This correlates with H4K5K12diAc removal and H3K9me1 accumulation, while H3K27me3 and H3K9me3 remain unchanged. Finally, we combine NCC enrichment with experimentally derived chromatin probabilities to predict a function in nascent chromatin for 93 uncharacterized proteins and identify FAM111A as a replication factor required for PCNA loading. Together, this provides an extensive resource to understand genome and epigenome maintenance. PMID:24561620

  6. Determining important regulatory relations of amino acids from dynamic network analysis of plasma amino acids.

    Science.gov (United States)

    Shikata, Nahoko; Maki, Yukihiro; Nakatsui, Masahiko; Mori, Masato; Noguchi, Yasushi; Yoshida, Shintaro; Takahashi, Michio; Kondo, Nobuo; Okamoto, Masahiro

    2010-01-01

    The changes in the concentrations of plasma amino acids do not always follow the flow-based metabolic pathway network. We have previously shown that there is a control-based network structure among plasma amino acids besides the metabolic pathway map. Based on this network structure, in this study, we performed dynamic analysis using time-course data of the plasma samples of rats fed single essential amino acid deficient diet. Using S-system model (conceptual mathematical model represented by power-law formalism), we inferred the dynamic network structure which reproduces the actual time-courses within the error allowance of 13.17%. By performing sensitivity analysis, three of the most dominant relations in this network were selected; the control paths from leucine to valine, from methionine to threonine, and from leucine to isoleucine. This result is in good agreement with the biological knowledge regarding branched-chain amino acids, and suggests the biological importance of the effect from methionine to threonine.

  7. Blister Test for Measurements of Adhesion and Adhesion Degradation of Organic Polymers on AA2024-T3

    Science.gov (United States)

    Rincon Troconis, Brendy Carolina

    cleaning/desmutting and conversion coating (CC) on the adhesion strength of acetoacetate to AA2024-T3 and the effects of improper water rinse temperature after cleaner were assessed using the BT. The results showed that pretreatments improve the adhesion strength of acetoacetate primer on AA2024-T3, but the comparative behavior depends on the specific treatment. Process control is of paramount importance for the performance of acetoacetate coated systems applied on AA2024-T3. The lack of thermal activity in the water rinse after cleaning step produces deleterious effects on the adhesion and blistering resistance of CC. Finally, a test sample incorporating a coated and scribed Al alloy panel and uncoated through-hole fasteners (Ti, SS316, AA2024-T3) was designed to provide accelerated response during atmospheric corrosion testing in the field (long-term beach exposure) or in laboratory chambers (ASTM B117). The results after only three weeks of exposure to ASTM B117 correlated well with long-term beach exposure, allowing rapid ranking of different coating systems. Of the fastener materials studied, visual observation and volume lost determination indicated that the worst attack occurred near SS316 fasteners its effect was explained by Scanning Kelvin Probe measurements and the available cathodic current measured in chloride solution.

  8. Candida biofilms: is adhesion sexy?

    Science.gov (United States)

    Soll, David R

    2008-08-26

    The development of Candida albicans biofilms requires two types of adhesion molecule - the Als proteins and Hwp1. Mutational analyses have recently revealed that these molecules play complementary roles, and their characteristics suggest that they may have evolved from primitive mating agglutinins. PMID:18727911

  9. Creep behaviour of flexible adhesives

    NARCIS (Netherlands)

    Straalen, IJ.J. van; Botter, E.; Berg, A. van den; Beers, P. van

    2004-01-01

    Since flexible adhesives are used more and more in structural applications, designers should have a better understanding of its behaviour under various conditions as ultimate load, fatigue load, long-term load and environmental conditions. This paper focuses on long-term load conditions and its effe

  10. Determinant representation for dynamical correlation functions of the Quantum nonlinear Schrödinger equation

    CERN Document Server

    Kojima, T; Slavnov, N A

    1997-01-01

    Painlevé analysis of correlation functions of the impenetrable Bose gas by M. Jimbo, T. Miwa, Y. Mori and M. Sato was based on the determinant representation of these correlation functions obtained by A. Lenard. The impenetrable Bose gas is the free fermionic case of the quantum nonlinear Schrödinger equation. In this paper we generalize the Lenard determinant representation for $$ to the non-free fermionic case. We also include time and temperature dependence. In forthcoming publications we shall perform the JMMS analysis of this correlation function. This will give us a completely integrable equation and asymptotic for the quantum correlation function of interacting fermions.

  11. Are the determinants of young SMEs profitability different?: empirical evidence using dynamic estimators

    OpenAIRE

    Viveiros, Ana Catarina Raposo

    2010-01-01

    Based in two sub-samples of Portuguese SMEs: 1) 495 young SMEs; and 2) 1350 old SMEs, we conclude that age is a determinant factor in the relationships formed between determinants and profitability. Age, size, liquidity and long-term debt are of greater relative importance for the increased profitability of young SMEs, while risk is of greater relative importance for the diminished profitability of this type of SME, compared to the case of old SMEs. R&D expenditure is of greate...

  12. Adhesion of biocompatible and biodegradable micropatterned surfaces

    NARCIS (Netherlands)

    Kaiser, J.S.; Kamperman, M.M.G.; Souza, E.J.; Schick, B.; Arzt, E.

    2011-01-01

    We studied the effects of pillar dimensions and stiffness of biocompatible and biodegradable micropatterned surfaces on adhesion on different compliant substrates. The micropatterned adhesives were based on biocompatible polydimethylsiloxane (PDMS) and biodegradable poly(lactic-co-glycolic) acid (PL

  13. Focal adhesions and cell-matrix interactions

    DEFF Research Database (Denmark)

    Woods, A; Couchman, J R

    1988-01-01

    Focal adhesions are areas of cell surfaces where specializations of cytoskeletal, membrane and extracellular components combine to produce stable cell-matrix interactions. The morphology of these adhesions and the components identified in them are discussed together with possible mechanisms...

  14. A new method for the determination of surface tension from molecular dynamics simulations applied to liquid droplets

    International Nuclear Information System (INIS)

    For the determination of surface tension of liquid droplets by molecular dynamics simulations, the most time-consuming part is the calculation of pressure tensor in the transition layer, which makes it difficult to enhance the precision of the computation. A new method for the calculation of surface tension of liquid droplets to reduce the calculation quantity of pressure tensor in transition layer to the minimum is proposed in this paper. Two thousand particles are taken as example to show how to carry out our scheme. (condensed matter: structural, mechanical, and thermal properties)

  15. Spatial Dynamics and Determinants of County-Level Education Expenditure in China

    Science.gov (United States)

    Gu, Jiafeng

    2012-01-01

    In this paper, a multivariate spatial autoregressive model of local public education expenditure determination with autoregressive disturbance is developed and estimated. The existence of spatial interdependence is tested using Moran's I statistic and Lagrange multiplier test statistics for both the spatial error and spatial lag models. The full…

  16. Temporal Dynamics and Decomposition of Reciprocal Determinism: A Reply to Phillips and Orton.

    Science.gov (United States)

    Bandura, Albert

    1983-01-01

    In their analysis of reciprocal determinism, Phillips and Orton (TM 509 061) mistakenly assume that behavior, cognitive and other personal factors, and environmental events operate as a simultaneous wholistic interaction. Contrary to this belief, the interactants in triadic reciprocality work their mutual effects sequentially over variable time…

  17. Epidemiology, determinants and dynamics of cholera in pakistan: gaps and prospects for future research

    International Nuclear Information System (INIS)

    Cholera is one of the notifiable endemic diseases in Pakistan, but the reporting of cholera cases is still unsatisfactory. Most of the diagnosed cases are never reported to the relevant authorities. In the year 1993 - 2005, the country did not report any single case of cholera to the WHO. The objectives of this review were to understand the epidemiology and to identify the possible determinants of cholera infection in Pakistan. Medscape, Medline, PakMedinet and PubMed, was searched, using key words, epidemiology and determinants of cholera infection in Pakistan during 1995 - 2010. Morbidity and mortality due to cholera infection during 1995 - 2010, without any language restriction. Out of 27 articles published between 1995 - 2010, 17 articles were included in the review. Vibrio cholerae O139 identified as a major cause of infection in older age group, while O1 biotype of cholera as a predominant cause of cholera among young individuals. Mainly reported determinants of cholera in Pakistan include poor sanitation and hygiene practices, increased population density in urban areas, leading to rapid and unplanned urbanization of the major cities and climate change due to increased environmental pollution in Pakistan are plausible factors for endemicity of cholera in Pakistan. Cholera reporting as a notifiable disease to the relevant departments and timely action can prevent the risk of outbreaks. There is a need to identify specific behavioral and environmental determinants responsible for outbreaks and epidemics of cholera in Pakistan which can help to design appropriate preventive and control interventions. (author)

  18. Determinants and Impacts Of Human Mobility Dynamics In The Western Highlands Of Cameroon

    NARCIS (Netherlands)

    Tankou, C.M.; Iongh, de H.H.; Persoon, G.; Bruijn, de M.E.; Snoo, de G.R.

    2014-01-01

    This study analyses human mobility among inhabitants of Cameroon‘s most populous region, the Western Highlands of Cameroon. In other to capture the impact of various determinants on human mobility, a comparative study was conducted through household and field surveys in three villages in the region

  19. Epidemiology, determinants and dynamics of cholera in Pakistan: gaps and prospects for future research.

    Science.gov (United States)

    Naseer, Maliha; Jamali, Tanzil

    2014-11-01

    Cholera is one of the notifiable endemic diseases in Pakistan, but the reporting of cholera cases is still unsatisfactory. Most of the diagnosed cases are never reported to the relevant authorities. In the year 1993 - 2005, the country did not report any single case of cholera to the WHO. The objectives of this review were to understand the epidemiology and to identify the possible determinants of cholera infection in Pakistan. Medscape, Medline, PakMedinet and PubMed, was searched, using key words, epidemiology and determinants of cholera infection in Pakistan during 1995 - 2010. Morbidity and mortality due to cholera infection during 1995 - 2010, without any language restriction. Out of 27 articles published between 1995 - 2010, 17 articles were included in the review. Vibrio cholerae O139 identified as a major cause of infection in older age group, while O1 biotype of cholera as a predominant cause of cholera among young individuals. Mainly reported determinants of cholera in Pakistan include poor sanitation and hygiene practices, increased population density in urban areas, leading to rapid and unplanned urbanization of the major cities and climate change due to increased environmental pollution in Pakistan are plausible factors for endemicity of cholera in Pakistan. Cholera reporting as a notifiable disease to the relevant departments and timely action can prevent the risk of outbreaks. There is a need to identify specific behavioral and environmental determinants responsible for outbreaks and epidemics of cholera in Pakistan which can help to design appropriate preventive and control interventions.

  20. Determination of organochlorine pesticides in water using dynamic hook-type liquid-phase microextraction

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Pai-Shan; Huang, Shih-Pin [Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Fuh, Ming-Ren, E-mail: msfuh@mail.scu.edu.tw [Department of Chemistry, Soochow University, Taipei, Taiwan (China); Huang, Shang-Da, E-mail: sdhuang@mx.nthu.edu.tw [Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

    2009-08-11

    We developed a simple and efficient headspace liquid-phase microextraction (LPME) technique named dynamic hook-type liquid-phase microextraction (DHT-LPME) and used it in combination with gas chromatography-mass spectrometry (GC-MS) and an electron capture detector (ECD). Aqueous specimens of organochlorine pesticides (OCPs) were used as model compounds to demonstrate the effectiveness of the technique. In the present study, the calibration curves were linear over at least 2 orders of magnitude with R{sup 2} values of 0.997. The method detection limits (MDLs) varied from 2 to 44.0 ng L{sup -1}. The precision of DHT-LPME ranged from 6.5 to 14.4%. The relative recoveries of OCPs in rainwater were more than 84.2%. Enrichment factors (EF) in the range 275-1127 were obtained using DHT-LPME.

  1. Dynamical behaviors determined by the Lyapunov function in competitive Lotka-Volterra systems.

    Science.gov (United States)

    Tang, Ying; Yuan, Ruoshi; Ma, Yian

    2013-01-01

    Dynamical behaviors of the competitive Lotka-Volterra system even for 3 species are not fully understood. In this paper, we study this problem from the perspective of the Lyapunov function. We construct explicitly the Lyapunov function using three examples of the competitive Lotka-Volterra system for the whole state space: (1) the general 2-species case, (2) a 3-species model, and (3) the model of May-Leonard. The basins of attraction for these examples are demonstrated, including cases with bistability and cyclical behavior. The first two examples are the generalized gradient system, where the energy dissipation may not follow the gradient of the Lyapunov function. In addition, under a new type of stochastic interpretation, the Lyapunov function also leads to the Boltzmann-Gibbs distribution on the final steady state when multiplicative noise is added.

  2. The dynamics of mergers and acquisitions: ancestry as the seminal determinant

    Science.gov (United States)

    Viegas, Eduardo; Cockburn, Stuart P.; Jensen, Henrik J.; West, Geoffrey B.

    2014-01-01

    Understanding the fundamental mechanisms behind the complex landscape of corporate mergers and acquisitions is of crucial importance to economies across the world. Adapting ideas from the fields of complexity and evolutionary dynamics to analyse business ecosystems, we show here that ancestry, i.e. the cumulative sum of historical mergers across all ancestors, is the key characteristic to company mergers and acquisitions. We verify this by comparing an agent-based model to an extensive range of business data, covering the period from the 1830s to the present day and a range of industries and geographies. This seemingly universal mechanism leads to imbalanced business ecosystems, with the emergence of a few very large, but sluggish ‘too big to fail’ entities, and very small, niche entities, thereby creating a paradigm where a configuration akin to effective oligopoly or monopoly is a likely outcome for free market systems. PMID:25383025

  3. Dynamics of Soil Erosion in Xingguo County, China,Determined Using Remote Sensing and GIS

    Institute of Scientific and Technical Information of China (English)

    PAN Jian-Jun; ZHANG Tao-Lin; ZHAO Qi-Guo

    2005-01-01

    The spatial and temporal dynamics of soil erosion in Xingguo County, Jiangxi Province, China were studied using multi-period remote sensing images and GIS. The results indicated that the soil erosion status of the region has been improving, particularly since the 1980s, with the erosion rate showing an evident decline over the past 30 years. The improvement showed not only in the decline of eroded soil area, but also with the reduction in the extent of erosion. The extent of erosion mainly changed by one level, and the change primarily occurred with the severely or moderately eroded soil types. However, in general, soil erosion was still an overriding problem in the region with some areas becoming more serious, especially those with large quantities of granite.

  4. Potassium dynamics are attenuated in hyperkalemia and a determinant of QT adaptation in exercising hemodialysis patients

    DEFF Research Database (Denmark)

    Tran, Cao Thach; Bundgaard, Henning; Ladefoged, Søren Daustrand;

    2013-01-01

    Disturbances in plasma potassium concentration (pK) are well known risk factors for the development of cardiac arrhythmia. The aims of the present study were to evaluate the effect of hemodialysis on exercise pK dynamics and QT hysteresis, and whether QT hysteresis is associated with the p......K decrease following exercise. Twenty-two end-stage renal disease patients exercised on a cycle ergometer with incremental work load before and after hemodialysis. ECG was recorded and pK was measured during exercise and recovery. During exercise, pK increased from 5.1 ± 0.2 to 6.1 ± 0.2 mM (mean ± SE; P...

  5. Dynamical patterning modules: physico-genetic determinants of morphological development and evolution

    Science.gov (United States)

    Newman, Stuart A.; Bhat, Ramray

    2008-03-01

    The shapes and forms of multicellular organisms arise by the generation of new cell states and types and changes in the numbers and rearrangements of the various kinds of cells. While morphogenesis and pattern formation in all animal species are widely recognized to be mediated by the gene products of an evolutionarily conserved 'developmental-genetic toolkit', the link between these molecular players and the physics underlying these processes has been generally ignored. This paper introduces the concept of 'dynamical patterning modules' (DPMs), units consisting of one or more products of the 'toolkit' genes that mobilize physical processes characteristic of chemically and mechanically excitable meso- to macroscopic systems such as cell aggregates: cohesion, viscoelasticity, diffusion, spatiotemporal heterogeneity based on lateral inhibition and multistable and oscillatory dynamics. We suggest that ancient toolkit gene products, most predating the emergence of multicellularity, assumed novel morphogenetic functions due to change in the scale and context inherent to multicellularity. We show that DPMs, acting individually and in concert with each other, constitute a 'pattern language' capable of generating all metazoan body plans and organ forms. The physical dimension of developmental causation implies that multicellular forms during the explosive radiation of animal body plans in the middle Cambrian, approximately 530 million years ago, could have explored an extensive morphospace without concomitant genotypic change or selection for adaptation. The morphologically plastic body plans and organ forms generated by DPMs, and their ontogenetic trajectories, would subsequently have been stabilized and consolidated by natural selection and genetic drift. This perspective also solves the apparent 'molecular homology-analogy paradox', whereby widely divergent modern animal types utilize the same molecular toolkit during development by proposing, in contrast to the Neo

  6. Adhesion properties of styrene-butadiene rubber (SBR/Standard Malaysian Rubber (SMR L-based adhesives in the presence of phenol formaldehyde resin

    Directory of Open Access Journals (Sweden)

    2007-10-01

    Full Text Available The adhesion properties, i. e. viscosity, tack and peel strength of styrene-butadiene rubber (SBR/Standard Malaysian Rubber (SMR L-based pressure-sensitive adhesive was studied using phenol formaldehyde resin as the tackifying resin. Toluene was used as the solvent throughout the experiment. SBR composition in SBR/SMR L blend used was 0, 20, 40, 60, 80, 100%. Three different resin loadings, i. e. 40, 80 and 120 parts per hundred parts of rubber (phr were used in the adhesive formulation. The viscosity of adhesive was determined by a HAAKE Rotary Viscometer whereas loop tack and peel strength of paper/polyethylene terephthalate (PET film were measured using a Lloyd Adhesion Tester operating at 30 cm/min. Results indicate that the viscosity of adhesive decreases with increasing % SBR whereas loop tack passes through a maximum value at 20% SBR for all resin loadings. Except for the control sample (without resin, the peel strength shows a maximum value at 60% SBR for the three modes of peel tests. For a fixed % SBR, adhesive sample containing 40 phr phenol formaldehyde resin always exhibits the highest loop tack and peel strength, an observation which is associated to the optimum wettability of adhesive on the substrate.

  7. Contraction stress in dentin adhesives bonded to dentin.

    Science.gov (United States)

    Hashimoto, M; de Gee, A J; Kaga, M; Feilzer, A J

    2006-08-01

    Adhesives cured under constrained conditions develop contraction stresses. We hypothesized that, with dentin as a bonding substrate, the stress would reach a maximum, followed by a continuous decline. Stress development was determined with a tensilometer for two total-etch systems and two systems with self-etching primers. The adhesives were placed in a thin layer between a glass plate and a flat dentin surface pretreated with phosphoric acid or self-etching primer. After an initial maximum shortly after light-curing, the stress decreased dramatically for the total-etch systems (70%) and, to a lesser extent, for the adhesives with self-etching primers (30%). The greater stress decrease for the total-etch systems was ascribed to water and/or solvents released into the adhesives from the fully opened dentinal tubules by the pulling/sucking action of the contraction stress. This happened less with the adhesives with self-etching primers, where the tubules remained mainly closed.

  8. Glass Fiber Reinforced Polypropylene Mechanical Properties Enhancement by Adhesion Improvement

    Directory of Open Access Journals (Sweden)

    Mariana Etcheverry

    2012-06-01

    Full Text Available Glass fibers (GF are the reinforcement agent most used in polypropylene (PP based composites, as they have good balance between properties and costs. However, their final properties are mainly determined by the strength and stability of the polymer-fiber interphase. Fibers do not act as an effective reinforcing material when the adhesion is weak. Also, the adhesion between phases can be easily degraded in aggressive environmental conditions such as high temperatures and/or elevated moisture, and by the stress fields to which the material may be exposed. Many efforts have been done to improve polymer-glass fiber adhesion by compatibility enhancement. The most used techniques include modifications in glass surface, polymer matrix and/or both. However, the results obtained do not show a good costs/properties improvement relationship. The aim of this work is to perform an accurate analysis regarding methods for GF/PP adhesion improvement and to propose a new route based on PP in-situ polymerization onto fibers. This route involves the modification of fibers with an aluminum alkyl and hydroxy-α-olefin and from there to enable the growth of the PP chains using direct metallocenic copolymerization. The adhesion improvements were further proved by fragmentation test, as well as by mechanical properties measurements. The strength and toughness increases three times and the interfacial strength duplicates in PP/GF composites prepared with in-situ polymerized fibers.

  9. Neutron imaging inspections of composite honeycomb adhesive bonds

    International Nuclear Information System (INIS)

    Numerous commercial and military aircraft, including the Canadian Forces CF188 Hornet, use composite honeycomb structures in the design of their flight control surfaces (FCS). These structures provide excellent strength to weight ratios, but are often susceptible to degradation from moisture ingress. Once inside the honeycomb structure moisture causes the structural adhesive bonds to weaken, which can lead to complete failure of the FCS in flight. There are two critical structural adhesive bonds: the node bond and the filet bond. The node bond is integral to the honeycomb portion of the composite core and is located between the honeycomb cells. The filet bond is the adhesive bond located between the skin and the core. In order to asses overall structural degradation and develop repair procedures, it is important to determine the degree of degradation in each type of bond. Neutron radiography and tomography of the adhesive bonds was conducted at the Royal Military College (RMC) and FRM-II. Honeycomb samples were manufactured from FCS with in-service water ingress. The radiographs and tomograms provided important information about the degree of degradation in the core as well as about which adhesive bonds are more susceptible. The information obtained from this study will help to develop repair techniques and assess the flight worthiness of FCS.

  10. Film adhesion in amorphous silicon solar cells

    Indian Academy of Sciences (India)

    A R M Yusoff; M N Syahrul; K Henkel

    2007-08-01

    A major issue encountered during fabrication of triple junction -Si solar cells on polyimide substrates is the adhesion of the solar cell thin films to the substrates. Here, we present our study of film adhesion in amorphous silicon solar cells made on different polyimide substrates (Kapton VN, Upilex-S and Gouldflex), and the effect of tie coats on film adhesion.

  11. Self-Adjustable Adhesion of Polyampholyte Hydrogels.

    Science.gov (United States)

    Roy, Chanchal Kumar; Guo, Hong Lei; Sun, Tao Lin; Ihsan, Abu Bin; Kurokawa, Takayuki; Takahata, Masakazu; Nonoyama, Takayuki; Nakajima, Tasuku; Gong, Jian Ping

    2015-12-01

    Developing nonspecific, fast, and strong adhesives that can glue hydrogels and biotissues substantially promotes the application of hydrogels as biomaterials. Inspired by the ubiquitous adhesiveness of bacteria, it is reported that neutral polyampholyte hydrogels, through their self-adjustable surface, can show rapid, strong, and reversible adhesion to charged hydrogels and biological tissues through the Coulombic interaction.

  12. Shear and Thermal Testing of Adhesives for VELO Upgrade

    CERN Document Server

    De Capua, Stefano; Klaver, Suzanne; Parkes, Chris; Rodriguez Perez, Pablo; Shtipliyski, Antoni; Stelmasiak, Guy James

    2016-01-01

    As part of the R&D process of the LHCb VELO Upgrade, a study has been performed on the thermal and mechanical performance of the adhesives Stycast 2850FT, 3M 9461P, and Araldite 2011. One or more of these adhesives could be used to attach the ASICs and hybrids to the microchannel cooling substrate. Samples were irradiated at up to the maximum dose expected at the upgrade. Shear tests of the samples were made and a suitable performance obtained from all glues. Some failures were encountered with Stycast 2850FT glued samples and this is attributed to the sample preparation. The relative thermal conductivities of the adhesives were also determined by measuring the relative temperature difference across a glued joint while one side is heated.

  13. Perspective: Adhesion Mediated Signal Transduction in Bacterial Pathogens

    Science.gov (United States)

    Moorthy, Sudha; Keklak, Julia; Klein, Eric A.

    2016-01-01

    During the infection process, pathogenic bacteria undergo large-scale transcriptional changes to promote virulence and increase intrahost survival. While much of this reprogramming occurs in response to changes in chemical environment, such as nutrient availability and pH, there is increasing evidence that adhesion to host-tissue can also trigger signal transduction pathways resulting in differential gene expression. Determining the molecular mechanisms of adhesion-mediated signaling requires disentangling the contributions of chemical and mechanical stimuli. Here we highlight recent work demonstrating that surface attachment drives a transcriptional response in bacterial pathogens, including uropathogenic Escherichia coli (E. coli), and discuss the complexity of experimental design when dissecting the specific role of adhesion-mediated signaling during infection. PMID:26901228

  14. Tangential adhesion strength of cement mortars in masonry

    Directory of Open Access Journals (Sweden)

    Derkach V.N.

    2012-05-01

    Full Text Available The initial shear strength (tangential adhesion and the angle of internal friction in the horizontal plane of mortar joints are among important characteristics, determining the masonry strength and stiffness qualities in case of share. These characteristics influence largely over the limit state approach of buildings and facilities during seismic activity and over wind, crane and other load, causing the panel frame distortion in frame buildings with masonry infill.In the paper the experimental studies results of tangential adhesion strength of cement mortars with solid and hollow ceramic bricks, porous stones, calcium silicate bricks and cellular concrete blocks are presented. This research gives experimental dependences of mortar adhesive strength with mentioned types of masonry units on compressive strength of cement mortar. There is also the comparison of the obtained results with Russian and foreign standards in this paper.

  15. Hyperphosphorylated FAK Delocalizes from Focal Adhesions to Membrane Ruffles

    Directory of Open Access Journals (Sweden)

    Abdelkader Hamadi

    2010-01-01

    Full Text Available Cell adhesion and migration are key determinants in tumor metastasis. Adherence of tumor cell to the extracellular matrix is mediated via integrin containing focal adhesions (FAs. Binding of integrins to ECM triggers phosphorylation of two major components of FAs, focal adhesion kinase (FAK and Src, activating downstream signaling pathway which leads to FA disassembly and cell migration. In this paper, we analyze how phosphorylation of FAK regulates its trafficking at FAs in living human astrocytoma cells. Upon pervanadate-induced FAK phosphorylation, phosphorylated FAK appeared highly expressed at newly formed membrane ruffles. This effect was abolished in presence of the specific Src inhibitor PP2. Our findings demonstrate that upon phosphorylation, FAK delocalizes from FAs to membrane ruffles.

  16. Constitutive behaviour of mixed mode loaded adhesive layer

    DEFF Research Database (Denmark)

    Högberg, J.L.; Sørensen, Bent F.; Stigh, U.

    2007-01-01

    Mixed mode testing of adhesive layer is performed with the Mixed mode double Cantilever Bean? specimen. During the experiments, the specimens are loaded by transversal and/or shear forces; seven different mode mixities are tested. The J-integral is used to evaluate the energy dissipation in the f......Mixed mode testing of adhesive layer is performed with the Mixed mode double Cantilever Bean? specimen. During the experiments, the specimens are loaded by transversal and/or shear forces; seven different mode mixities are tested. The J-integral is used to evaluate the energy dissipation...... in the failure process zone. The constitutive behaviour of the adhesive layer is obtained by a so called inverse method and fitting an existing mixed mode cohesive model, which uses a coupled formulation to describe a mode dependent constitutive behaviour. The cohesive parameters are determined by optimizing...

  17. Bovine milk osteopontin - Targeting bacterial adhesion for biofilm control

    DEFF Research Database (Denmark)

    Kristensen, Mathilde Frost; Meyer, Rikke Louise; Schlafer, Sebastian

    Self-performed mechanical tooth cleaning does usually not result in complete biofilm removal, due to the complex oral anatomy and the strong adhesion of the biofilm to the tooth. Therefore, different supportive measures are employed, most of which aim at the chemical eradication of bacteria...... in dental biofilms. As their bactericidal action impacts the entire oral microflora, agents that inhibit biofilm formation without killing bacteria, such as the bovine milk protein osteopontin, have gained increasing attention. Here, we investigate the adhesion of 8 bacterial species associated with dental.......05). ), as determined by two-sample t-tests. The broad range anti-adhesive effect of osteopontin on dental bacterial strains might explain the reduced biofilm formation observed and be exploited in vivo for increased caries control....

  18. Determination of reactivity by a revised rod-drop technique in the muse-4 programme - comparison with dynamic measurements

    International Nuclear Information System (INIS)

    The MUSE-4 experimental programme in the zero power fast facility MASURCA at CEA Cadarache aims at studying accelerator-driven-systems (ADS). One of the main objectives is the qualification of measuring and monitoring sub-critical reactivities. Rossi α and Feynman α and pulsed neutron source techniques based on the use of the GENEPI deuteron accelerator are investigated to assess the prompt neutron decay constant a and to deduce the reactivity. Reactivity reference levels are determined using a revised rod drop technique and static source multiplication methods for comparison with values extracted from dynamic measurements. This article focuses on the determination of the inherent source and the reactivity sensitivity to kinetic constants and counting rate in the rod drop technique using the point kinetic model. (author)

  19. In Silico Determination of Gas Permeabilities by Non-Equilibrium Molecular Dynamics: CO2 and He through PIM-1

    Directory of Open Access Journals (Sweden)

    Hendrik Frentrup

    2015-03-01

    Full Text Available We study the permeation dynamics of helium and carbon dioxide through an atomistically detailed model of a polymer of intrinsic microporosity, PIM-1, via non-equilibrium molecular dynamics (NEMD simulations. This work presents the first explicit molecular modeling of gas permeation through a high free-volume polymer sample, and it demonstrates how permeability and solubility can be obtained coherently from a single simulation. Solubilities in particular can be obtained to a very high degree of confidence and within experimental inaccuracies. Furthermore, the simulations make it possible to obtain very specific information on the diffusion dynamics of penetrant molecules and yield detailed maps of gas occupancy, which are akin to a digital tomographic scan of the polymer network. In addition to determining permeability and solubility directly from NEMD simulations, the results shed light on the permeation mechanism of the penetrant gases, suggesting that the relative openness of the microporous topology promotes the anomalous diffusion of penetrant gases, which entails a deviation from the pore hopping mechanism usually observed in gas diffusion in polymers.

  20. Friction and Adhesion mediated by supramolecular host-guest complexes

    OpenAIRE

    Guerra, Roberto; Benassi, Andrea; Vanossi, Andrea; Ma, Ming; Urbakh, Michael

    2016-01-01

    The adhesive and frictional response of an AFM tip connected to a substrate through supramolecular host-guest complexes is investigated by dynamic Monte Carlo simulations. The variation of the pull-off force with the unloading rate recently observed in experiments is here unraveled by evidencing a simultaneous (progressive) break of the bonds at fast (slow) rates. The model reveals the origin of the observed plateaus in the retraction force as a function of tip-surface distance, showing that ...

  1. Staying sticky: contact self-cleaning of gecko-inspired adhesives.

    Science.gov (United States)

    Mengüç, Yigit; Röhrig, Michael; Abusomwan, Uyiosa; Hölscher, Hendrik; Sitti, Metin

    2014-05-01

    The exceptionally adhesive foot of the gecko remains clean in dirty environments by shedding contaminants with each step. Synthetic gecko-inspired adhesives have achieved similar attachment strengths to the gecko on smooth surfaces, but the process of contact self-cleaning has yet to be effectively demonstrated. Here, we present the first gecko-inspired adhesive that has matched both the attachment strength and the contact self-cleaning performance of the gecko's foot on a smooth surface. Contact self-cleaning experiments were performed with three different sizes of mushroom-shaped elastomer microfibres and five different sizes of spherical silica contaminants. Using a load-drag-unload dry contact cleaning process similar to the loads acting on the gecko foot during locomotion, our fully contaminated synthetic gecko adhesives could recover lost adhesion at a rate comparable to that of the gecko. We observed that the relative size of contaminants to the characteristic size of the microfibres in the synthetic adhesive strongly determined how and to what degree the adhesive recovered from contamination. Our approximate model and experimental results show that the dominant mechanism of contact self-cleaning is particle rolling during the drag process. Embedding of particles between adjacent fibres was observed for particles with diameter smaller than the fibre tips, and further studied as a temporary cleaning mechanism. By incorporating contact self-cleaning capabilities, real-world applications of synthetic gecko adhesives, such as reusable tapes, clothing closures and medical adhesives, would become feasible.

  2. Potential of the adhesion of bacteria isolated from drinking water to materials.

    Science.gov (United States)

    Simões, Lúcia Chaves; Simões, Manuel; Oliveira, Rosário; Vieira, Maria João

    2007-04-01

    Heterotrophic bacteria (11 genera, 14 species, 25 putative strains) were isolated from drinking water, identified either biochemically or by partial 16s rDNA gene sequencing and their adherence characteristics were determined by two methods: i. thermodynamic prediction of adhesion potential by measuring hydrophobicity (contact angle measurements) and ii. by measuring adherence to eight different substrata (ASI 304 and 316 stainless steel, copper, polyvinyl chloride, polypropylene, polyethylene, silicone and glass). All the test organisms were hydrophilic and inter-species variation in hydrophobicity occurred only for Comamonas acidovorans. Stainless steel 304 (SS 304), copper, polypropylene (PP), polyethylene (PE) and silicone thermodynamically favoured adhesion for the majority of test strains (>18/25), whilst adhesion was generally less thermodynamically favorable for stainless steel 316 (SS 316), polyvinyl chloride (PVC) and glass. The predictability of thermodynamic adhesion test methods was validated by comparison with 24-well microtiter plate assays using nine reference strains and three adhesion surfaces (SS 316, PVC and PE). Results for Acinetobacter calcoaceticus, Burkolderia cepacia and Stenotrophomonas maltophilia sp. 2 were congruent between both methods whilst they differed for the other bacteria to at least one material. Only A. calcoaceticus had strongly adherent properties to the three tested surfaces. Strain variation in adhesion ability was detected only for Sphingomonas capsulata. Analysis of adhesion demonstrated that in addition to physicochemical surface properties of bacterium and substratum, biological factors are involved in early adhesion processes, suggesting that reliance on thermodynamic approaches alone may not accurately predict adhesion capacity. PMID:17440920

  3. Determinant representation for dynamical correlation functions of the quantum nonlinear Schroedinger equation

    Energy Technology Data Exchange (ETDEWEB)

    Kojima, T. [Kyoto Univ. (Japan). Research Inst. for Mathematical Sciences; Korepin, V.E. [Institute for Theoretical Physics, State University of New York at Stony Brook, Stony Brook, NY (United States); Slavnov, N.A. [Steklov Mathematical Institute, Gubkina 8, Moscow 117966 (Russian Federation)

    1997-10-01

    Painleve analysis of correlation functions of the impenetrable Bose gas by M. Jimbo, T. Miwa, Y. Mori and M. Sato was based on the determinant representation of these correlation functions obtained by A. Lenard. The impenetrable Bose gas is the free fermionic case of the quantum nonlinearSchroedinger equation. In this paper we generalize the Lenard determinant representation for left angle {psi}(0,0){psi}{sup {dagger}}(x,t) right angle to the non-free fermionic case. We also include time and temperature dependence. In forthcoming publications we shall perform the JMMS analysis of this correlation function. This will give us a completely integrable equation and asymptotic for the quantum correlation function of interacting fermions. (orig.) 19 refs.

  4. Determinant Representation for Dynamical Correlation Functions of the Quantum Nonlinear Schrödinger Equation

    Science.gov (United States)

    Kojima, T.; Korepin, V. E.; Slavnov, N. A.

    Painlevé analysis of correlation functions of the impenetrable Bose gas by M. Jimbo, T. Miwa, Y. Mori and M. Sato [1] was based on the determinant representation of these correlation functions obtained by A. Lenard [2]. The impenetrable Bose gas is the free fermionic case of the quantum nonlinear Schrödinger equation. In this paper we generalize the Lenard determinant representation for ψ (0,0)ψ (x,t)> to the non-free fermionic case. We also include time and temeprature dependence. In forthcoming publications we shall perform the JMMS analysis of this correlationl function. This will give us a completely integrable equation and asymptotic for the quantum correlation function of interacting fermions.

  5. DETERMINATION OF PARTICLE DENSITY BY MERCURY POROSIMETRY FOR BIOMASS FLUID DYNAMIC STUDY IN MOVING BEDS

    Directory of Open Access Journals (Sweden)

    Juan F. Saldarriaga

    2014-06-01

    Full Text Available Determination of the particle density is required to address the hydrodynamic study of a moving bed contactor. The measurement of this parameter is complicated when particles are irregularly shaped. In this study, two different techniques were use: compaction by mechanical compression and an alternative proposal, which contemplates the potential of mercury porosimetry for determining the surface and structural properties. It was observed that the results obtained by compacting in all cases are higher than expected. However, the values obtained by mercury porosimetry are more consistent with expected values. For example in the sawdust valued at 500kg/m3, very similar to the value of the original wood (502kg/m3. Values obtained by this procedure adequately represent the relationship between mass and volume of the particle and therefore are valid for hydrodynamic characterization of the biomass.

  6. Ultrastructural and biochemical studies of two dynamically expressed cell surface determinants on Candida albicans.

    OpenAIRE

    Brawner, D L; Cutler, J E

    1986-01-01

    Variability in the expression of two different cell surface carbohydrate determinants was examined with two agglutinating immunoglobulin M monoclonal antibodies (H9 and C6) and immunoelectron microscopy during growth of three strains of Candida albicans. A single strain of Candida parapsilosis did not express either antigen at any time during growth. Antigens were detected on the surface of C. albicans by agglutination tests with either H9 or C6 over a 48-h growth period. The difference in sp...

  7. Phylogenetic distribution and evolutionary dynamics of the sex determination genes doublesex and transformer in insects.

    Science.gov (United States)

    Geuverink, E; Beukeboom, L W

    2014-01-01

    Sex determination in insects is characterized by a gene cascade that is conserved at the bottom but contains diverse primary signals at the top. The bottom master switch gene doublesex is found in all insects. Its upstream regulator transformer is present in the orders Hymenoptera, Coleoptera and Diptera, but has thus far not been found in Lepidoptera and in the basal lineages of Diptera. transformer is presumed to be ancestral to the holometabolous insects based on its shared domains and conserved features of autoregulation and sex-specific splicing. We interpret that its absence in basal lineages of Diptera and its order-specific conserved domains indicate multiple independent losses or recruitments into the sex determination cascade. Duplications of transformer are found in derived families within the Hymenoptera, characterized by their complementary sex determination mechanism. As duplications are not found in any other insect order, they appear linked to the haplodiploid reproduction of the Hymenoptera. Further phylogenetic analyses combined with functional studies are needed to understand the evolutionary history of the transformer gene among insects.

  8. Bidirectional remodeling of β1-integrin adhesions during chemotropic regulation of nerve growth

    Directory of Open Access Journals (Sweden)

    Carlstrom Lucas P

    2011-11-01

    Full Text Available Abstract Background Chemotropic factors in the extracellular microenvironment guide nerve growth by acting on the growth cone located at the tip of extending axons. Growth cone extension requires the coordination of cytoskeleton-dependent membrane protrusion and dynamic adhesion to the extracellular matrix, yet how chemotropic factors regulate these events remains an outstanding question. We demonstrated previously that the inhibitory factor myelin-associated glycoprotein (MAG triggers endocytic removal of the adhesion receptor β1-integrin from the growth cone surface membrane to negatively remodel substrate adhesions during chemorepulsion. Here, we tested how a neurotrophin might affect integrin adhesions. Results We report that brain-derived neurotropic factor (BDNF positively regulates the formation of substrate adhesions in axonal growth cones during stimulated outgrowth and prevents removal of β1-integrin adhesions by MAG. Treatment of Xenopus spinal neurons with BDNF rapidly triggered β1-integrin clustering and induced the dynamic formation of nascent vinculin-containing adhesion complexes in the growth cone periphery. Both the formation of nascent β1-integrin adhesions and the stimulation of axon extension by BDNF required cytoplasmic calcium ion signaling and integrin activation at the cell surface. Exposure to MAG decreased the number of β1-integrin adhesions in the growth cone during inhibition of axon extension. In contrast, the BDNF-induced adhesions were resistant to negative remodeling by MAG, correlating with the ability of BDNF pretreatment to counteract MAG-inhibition of axon extension. Pre-exposure to MAG prevented the BDNF-induced formation of β1-integrin adhesions and blocked the stimulation of axon extension by BDNF. Conclusions Altogether, these findings demonstrate the neurotrophin-dependent formation of integrin-based adhesions in the growth cone and reveal how a positive regulator of substrate adhesions can block

  9. The Role of Lipid Rafts in Cancer Cell Adhesion and Migration

    Directory of Open Access Journals (Sweden)

    Toshiyuki Murai

    2012-01-01

    Full Text Available Lipid rafts are cholesterol-enriched microdomains of the cell membrane and possess a highly dynamic nature. They have been involved in various cellular functions including the regulation of cell adhesion and membrane signaling through proteins within lipid rafts. The dynamic features of the cancer cell surface may modulate the malignant phenotype of cancer, including adhesion disorders and aggressive phenotypes of migration and invasion. Recently, it was demonstrated that lipid rafts play critical roles in cancer cell adhesion and migration. This article summarizes the important roles of lipid rafts in cancer cell adhesion and migration, with a focus on the current state of knowledge. This article will improve the understanding of cancer progression and lead to the development of novel targets for cancer therapy.

  10. Strong underwater adhesives made by self-assembling multi-protein nanofibres.

    Science.gov (United States)

    Zhong, Chao; Gurry, Thomas; Cheng, Allen A; Downey, Jordan; Deng, Zhengtao; Stultz, Collin M; Lu, Timothy K

    2014-10-01

    Many natural underwater adhesives harness hierarchically assembled amyloid nanostructures to achieve strong and robust interfacial adhesion under dynamic and turbulent environments. Despite recent advances, our understanding of the molecular design, self-assembly and structure-function relationships of these natural amyloid fibres remains limited. Thus, designing biomimetic amyloid-based adhesives remains challenging. Here, we report strong and multi-functional underwater adhesives obtained from fusing mussel foot proteins (Mfps) of Mytilus galloprovincialis with CsgA proteins, the major subunit of Escherichia coli amyloid curli fibres. These hybrid molecular materials hierarchically self-assemble into higher-order structures, in which, according to molecular dynamics simulations, disordered adhesive Mfp domains are exposed on the exterior of amyloid cores formed by CsgA. Our fibres have an underwater adhesion energy approaching 20.9 mJ m(-2), which is 1.5 times greater than the maximum of bio-inspired and bio-derived protein-based underwater adhesives reported thus far. Moreover, they outperform Mfps or curli fibres taken on their own and exhibit better tolerance to auto-oxidation than Mfps at pH ≥ 7.0.

  11. Strong underwater adhesives made by self-assembling multi-protein nanofibres

    Science.gov (United States)

    Zhong, Chao; Gurry, Thomas; Cheng, Allen A.; Downey, Jordan; Deng, Zhengtao; Stultz, Collin M.; Lu, Timothy K.

    2014-10-01

    Many natural underwater adhesives harness hierarchically assembled amyloid nanostructures to achieve strong and robust interfacial adhesion under dynamic and turbulent environments. Despite recent advances, our understanding of the molecular design, self-assembly and structure-function relationships of these natural amyloid fibres remains limited. Thus, designing biomimetic amyloid-based adhesives remains challenging. Here, we report strong and multi-functional underwater adhesives obtained from fusing mussel foot proteins (Mfps) of Mytilus galloprovincialis with CsgA proteins, the major subunit of Escherichia coli amyloid curli fibres. These hybrid molecular materials hierarchically self-assemble into higher-order structures, in which, according to molecular dynamics simulations, disordered adhesive Mfp domains are exposed on the exterior of amyloid cores formed by CsgA. Our fibres have an underwater adhesion energy approaching 20.9 mJ m-2, which is 1.5 times greater than the maximum of bio-inspired and bio-derived protein-based underwater adhesives reported thus far. Moreover, they outperform Mfps or curli fibres taken on their own and exhibit better tolerance to auto-oxidation than Mfps at pH ≥ 7.0.

  12. Polyurethane structural adhesives applied in automotive composite joints

    Directory of Open Access Journals (Sweden)

    Josue Garcia Quini

    2012-06-01

    Full Text Available In recent years structural adhesives technology has demonstrated great potential for application due to its capacity to transform complex structures into solid unitary and monolithic assemblies using different materials. Thus, seams or joints integrate these structures providing, besides a reduction in weight, a considerable increase in the mechanical resistance and stiffness. The increase in the industrial use of structural adhesives is mainly due to their ability to efficiently bond different materials in an irreversible manner, even replacing systems involving mechanical joints. In the automobile industry structural adhesives have been widely used for the bonding of metal substrates, thermoplastics and composites, frequently employing these in combination, particularly glass fiber and polyester resin composites molded using RTM and SMC processes. However, the use of urethane structural adhesives in applications involving composites and thermoplastics has been the subject of few investigations. In this study the effects of temperature and time on the shear strength of RTM, SMC and ABS joints, applying temperatures of -40, 25, 80, 120 and 177 °C and times of 20 minutes and 500 hours, were determined. The objective was to evaluate the performance under extreme conditions of use in order to assess whether these joints could be used in passenger or off-road vehicles. The results showed that the urethane structural adhesive promoted the efficient bonding of these materials, considering that due to the high adhesive strength the failures occurred in the substrates without adversely affecting the bonded area. For each test condition the joint failure modes were also determined.

  13. Determination of populations of vibrational levels of carbon dioxide molecules in gas dynamic lasers by ir spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Bakhir, L.P.; Overchenko, Yu.V.

    1979-01-01

    The absorption and emission spectra of some vibrational and rotational transitions of the carbon dioxide molecule in the range of 4.3, 10, and 15 ..mu.. m are analyzed under non-equilibrium conditions at the outlet of a gas-dynamic laser; and an examination is made of the possibility of their use to determine the populations of lower vibrational levels of carbon dioxide at different degrees of expansion. In view of the sharp distinction of relaxation rates for various degrees of freedom in a gas-dynamic laser, the vibrational temperatures of various levels of CO/sub 2/ may differ significantly from each other, as well as from rotational and translational temperatures. In describing populations in terms of the length of a jet, vibrational and rotational energies are separated and population temperatures equal to mode temperatures are assumed for purely symmetric deformation and asymmetric vibrations. A method for determining the absolute populations of low vibrational levels of the carbon dioxide molecule is developed according to measurements of absorption and brightness of a non-equilibrium jet near given frequencies.

  14. Dynamics of pruning waste and spent horse litter co-composting as determined by chemical parameters.

    Science.gov (United States)

    Benito, Marta; Masaguer, Alberto; Moliner, Ana; Hontoria, Chiquinquirá; Almorox, Javier

    2009-01-01

    Co-composting of pruning waste and horse manure was monitored by different parameters. A windrow composting pile, having the dimensions 2.5m (height) x 30m (length) was established. The maturation of pruning waste and horse manure compost was accompanied by a decline in NH(4)(+)-N concentration, water soluble C and an increase in NO(3)(-)-N content. Organic matter (OM) content during composting followed a first-order kinetic equation. This result was in agreement with the microbiological activity measured by the CO(2) respiration during the process. The correlation at a high level of probability found between the OM loss and CO(2) evolution showed that both parameters could be used to indicate the degree of OM degradation that is the maturity and stability phases of the compost studied. Humification parameters data from the organic matter fractionation did not show a clear tendency during the composting time, suggesting that these parameters are not suitable for evaluating the dynamics of the process.

  15. Determination of the Accommodation Coefficient Using Vapor/gas Bubble Dynamics in an Acoustic Field

    Science.gov (United States)

    Gumerov, Nail A.; Hsiao, Chao-Tsung; Goumilevski, Alexei G.; Allen, Jeff (Technical Monitor)

    2001-01-01

    Nonequilibrium liquid/vapor phase transformations can occur in superheated or subcooled liquids in fast processes such as in evaporation in a vacuum. The rate at which such a phase transformation occurs depends on the "condensation" or "accommodation" coefficient, Beta, which is a property of the interface. Existing measurement techniques for Beta are complex and expensive. The development of a relatively inexpensive and reliable technique for measurement of Beta for a wide range of substances and temperatures is of great practical importance. The dynamics of a bubble in an acoustic field strongly depends on the value of Beta. It is known that near the saturation temperature, small vapor bubbles grow under the action of an acoustic field due to "rectified heat transfer." This finding can be used as the basis for an effective measurement technique of Beta. We developed a theory of vapor bubble behavior in an isotropic acoustic wave and in a plane standing acoustic wave. A numerical code was developed which enables simulation of a variety of experimental situations and accurately takes into account slowly evolving temperature. A parametric study showed that the measurement of Beta can be made over a broad range of frequencies and bubble sizes. We found several interesting regimes and conditions which can be efficiently used for measurements of Beta. Measurements of Beta can be performed in both reduced and normal gravity environments.

  16. Life-history and spatial determinants of somatic growth dynamics in Komodo dragon populations.

    Directory of Open Access Journals (Sweden)

    Rebecca J Laver

    Full Text Available Somatic growth patterns represent a major component of organismal fitness and may vary among sexes and populations due to genetic and environmental processes leading to profound differences in life-history and demography. This study considered the ontogenic, sex-specific and spatial dynamics of somatic growth patterns in ten populations of the world's largest lizard the Komodo dragon (Varanus komodoensis. The growth of 400 individual Komodo dragons was measured in a capture-mark-recapture study at ten sites on four islands in eastern Indonesia, from 2002 to 2010. Generalized Additive Mixed Models (GAMMs and information-theoretic methods were used to examine how growth rates varied with size, age and sex, and across and within islands in relation to site-specific prey availability, lizard population density and inbreeding coefficients. Growth trajectories differed significantly with size and between sexes, indicating different energy allocation tactics and overall costs associated with reproduction. This leads to disparities in maximum body sizes and longevity. Spatial variation in growth was strongly supported by a curvilinear density-dependent growth model with highest growth rates occurring at intermediate population densities. Sex-specific trade-offs in growth underpin key differences in Komodo dragon life-history including evidence for high costs of reproduction in females. Further, inverse density-dependent growth may have profound effects on individual and population level processes that influence the demography of this species.

  17. Dynamics of the generalized 3x+1 function determined by its fractal images

    Institute of Scientific and Technical Information of China (English)

    Xingyuan Wang; Xuejing Yu

    2008-01-01

    Two different complex maps were obtained by generalizing 3x + 1 function to the complex plane, and fractal images for these two complex maps were constructed by using escape time, stopping time and total stopping time arithmetic. The dynamics of the generalized 3x+1 function based on the structural characteristics of the fractal images was studied. We found that: (1) the size and structure of the stable regions, stopping regions, total stopping regions, and divergent regions for the three types of fractal images depend on convergence rate of the map on the x and y axes. (2) The black stable regions constructed, respectively, by escape time and total stopping time are almost overlapped, demonstrating that 3x+1 function converged steadily. (3) All of the three fractal images are symmetric to the real axis. The structures on the neighborhood of positive integer number are symmetric to a perpendicular line, which is corresponding to the point or its nearby points on the x axis. And the structures have complicated fractal structure characteristics. These findings indicate that the generalized 3x+1 function on integer number and its neighborhood contains plentiful information in the complex plane.

  18. A Direct Comparison between Static and Dynamic Melting Temperature Determinations below 100 GPa

    Institute of Scientific and Technical Information of China (English)

    SUN Yu-Huai; HUANG Hai-Jun; LIU Fu-Sheng; YANG Mei-Xia; JING Fu-Qian

    2005-01-01

    @@ A preliminary experiment of sound velocity measurements for porous iron with initial average density of 6.275 g/cm3 has been performed at pressures below 100 GPa, in order to clarify a long-standing problem that the static melting temperature Tm, mostly below 100 GPa due to its technical limitations, is notably lower than the extrapolated melting data inferred from the shock wave experiments made above 200 GPa, for the sake of making a direct comparison between the experimental static and dynamic melting temperatures in the same pressure region.With the lately proposed Hugoniot sound velocity data analysis technique [Chin. Phys. Lett. 22 (2005) 863], the results deduced from this Hugoniot sound velocity measurement is Tm = 3200 K at 87GPa and Tm = 3080 K at80 GPa, which are in good agreement with the two latest static data ofTm = 3510 K at 105 GPa and Tm = 2750 K at 58 GPa, which utilized modern improved double-side laser heating and in situ accurate x-ray diffraction techniques in experiments. It can be concluded that consensus Tm data would be obtained from static and shock wave experiments in the case that the recently improved techniques are adopted in investigations.

  19. Growth and structural determination of He bubbles in iron/chromium alloys using molecular dynamics simulations

    Science.gov (United States)

    Abhishek, A.; Warrier, M.; Ganesh, R.; Caro, A.

    2016-04-01

    Helium(He) produced by transmutation process inside structural material due to neutron irradiation plays a vital role in the degradation of material properties. We have carried out Molecular dynamics(MD) simulations to study the growth of He bubble in Iron-Chromium alloy. Simulations are carried out at two different temperatures, viz. 0.1 K and 800 K, upto He bubble radius of 2.5 nm. An equation for variation of volume of He bubbles with the number of He atoms is obtained at both the temperatures. Bubble pressure and potential energy variation is obtained with increasing bubble radius. Dislocations are also found to be emitted after the bubble reaches a critical radius of 0.39 nm at 800 K. Separate MD simulations of He with pre-created voids are also carried out to study the binding energies of He and Vacancy (V) to Hem-Vn cluster. Binding energies are found to be in the range of 1-5.5 eV.

  20. A two-stage method to determine optimal product sampling considering dynamic potential market.

    Science.gov (United States)

    Hu, Zhineng; Lu, Wei; Han, Bing

    2015-01-01

    This paper develops an optimization model for the diffusion effects of free samples under dynamic changes in potential market based on the characteristics of independent product and presents a two-stage method to figure out the sampling level. The impact analysis of the key factors on the sampling level shows that the increase of the external coefficient or internal coefficient has a negative influence on the sampling level. And the changing rate of the potential market has no significant influence on the sampling level whereas the repeat purchase has a positive one. Using logistic analysis and regression analysis, the global sensitivity analysis gives a whole analysis of the interaction of all parameters, which provides a two-stage method to estimate the impact of the relevant parameters in the case of inaccuracy of the parameters and to be able to construct a 95% confidence interval for the predicted sampling level. Finally, the paper provides the operational steps to improve the accuracy of the parameter estimation and an innovational way to estimate the sampling level.

  1. Cell adhesion molecules and hyaluronic acid as markers of inflammation, fibrosis and response to antiviral therapy in chronic hepatitis C patients

    Directory of Open Access Journals (Sweden)

    Esther Granot

    2001-01-01

    Full Text Available Objective: Cell adhesion molecules (intracellular adhesion molecule-1 (ICAM-1, vascular cell adhesion molecule-1 (VCAM-1 and hyaluronic acid, markers of inflammation and fibrosis were monitored in hepatitis C patients to determine whether changes in plasma levels, during antiviral treatment, can predict long-term response to therapy.

  2. A Dynamic Analysis of Capital Structure Determinants. Empirical Results for Romanian Capital Market

    Directory of Open Access Journals (Sweden)

    Mihaela Dragota

    2008-04-01

    Full Text Available The analysis of capital structure and its determinants represents an useful approach for the Romanian and foreign investors and for the companies, at the same time. The main conclusion for capital structure analysis was that Romanian listed companies sustained their assets, in this order, on equity, commercial debt and, finally, on financial debt. The four variables used in the regression model are significant. The pecking order theory seemed to be more appropriate for the Romanian capital market, but the signalling theory was not entirely rejected.

  3. Determination of Scaling Parameter and Dynamical Resonances in Complex-Rotated Hamiltonian Ⅰ: Theory

    Institute of Scientific and Technical Information of China (English)

    LI Heng-Mei; ZHAO Fang; YUAN Hong-Chun; ZHAO Mei-Shan

    2008-01-01

    In this paper we present a theoretical analysis on the determination of the scaling parameter in the complex-rotated Hamiltonian, which has served as a basis for successful applications of the rigged Hilbert space theory for resonances. Based on the complex energy eigenvalue, E(θ) = En(θ) - iF(θ)/2, as a function of the scaling parameter The condition dER(θR)/ dθ = 0 is merely a consequence of the Virial theorem and θⅠ = θR is not a necessary condition for a resonance state. We also provide a harmonic approximation formalism for resonances in scattering over a potential barrier.

  4. Direct observation of microbial adhesion to membranes.

    Science.gov (United States)

    Wang, Sunny; Guillen, Greg; Hoek, Eric M V

    2005-09-01

    Direct microscopic observation and an interfacial force model were used to better understand and control microbial adhesion to polymeric ultrafiltration membranes. The model was used to predict a "critical flux", below which cells deposited reversibly, and direct observation was used to visually quantify cell deposition and removal. In preliminary direct observation experiments, permeate reversal (backpulsing) was more effective than cross-flow hydrodynamics at removing deposited cells. In experiments conducted below the critical flux, no cell accumulation was observed over repeated forward-reverse filtration cycles; however, a small fraction of cells deposited irreversibly regardless of the flux, membrane, or solution chemistry. The fraction of irreversibly deposited cells was consistent with the equilibrium surface coverage attained without permeation (i.e., due to heterogeneous adsorption). Although steric forces were not invoked to establish a critical flux, when operating above the critical flux, a balance between permeation drag and steric repulsion appeared to determine the strength of adhesion of cells to membranes. Direct observation also confirmed that above the critical flux fouling occurred and pressure losses accumulated over several backpulse cycles, whereas below the critical flux there were no observable pressure losses or fouling. PMID:16190200

  5. UV-cured adhesives for carbon fiber composite applications

    Science.gov (United States)

    Lu, Hsiao-Chun

    Carbon fiber composite materials are increasingly used in automobile, marine, and aerospace industries due to their unique properties, including high strength, high stiffness and low weight. However, due to their brittle characteristic, these structures are prone to physical damage, such as a bird strike or impact damage. Once the structure is damaged, it is important to have fast and reliable temporary repair until the permanent repair or replacement can take place. In this dissertation, UV-based adhesives were used to provide a bonding strength for temporary repair. Adhesively bonded patch repair is an efficient and effective method for temporary repair. In this study, precured patches (hard patches) and dry fabric patches with laminating resins (soft patches) were performed. UV-based epoxy adhesives were applied to both patch repair systems. For precured patch repair, the bonding strengths were investigated under different surface treatments for bonding area and different adhesives thicknesses. The shear stresses of different UV exposure times and curing times were tested. Besides, the large patch repair was investigated as well. For soft patch repair, the hand wet lay-up was applied due to high viscosity of UV resins. A modified single lap shear testing (ASTM D5868) was applied to determine the shear stress. The large patches used fiber glass instead of carbon fiber to prove the possibility of repair with UV epoxy resin by hand wet lay-up process. The hand lay-up procedure was applied and assisted by vacuum pressure to eliminate the air bubbles and consolidate the patches. To enhance the bonding strength and effective soft patch repair, vacuum assisted resin transferring molding (VaRTM) is the better option. However, only low viscosity resins can be operated by VaRTM. Hence, new UV-based adhesives were formulated. The new UV-based adhesives included photoinitiator (PI), epoxy and different solvents. Solvents were used to compound the photoinitiator into epoxy

  6. Snail1 controls epithelial–mesenchymal lineage commitment in focal adhesion kinase–null embryonic cells

    OpenAIRE

    Li, Xiao-Yan; Zhou, Xiaoming; Rowe, R. Grant; Hu, Yuexian; Schlaepfer, David D.; Ilić, Dusko; Dressler, Gregory; Park, Ann; Guan, Jun-Lin; Weiss, Stephen J.

    2011-01-01

    Mouse embryonic cells isolated from focal adhesion kinase (FAK)–null animals at embryonic day 7.5 display multiple defects in focal adhesion remodeling, microtubule dynamics, mechanotransduction, proliferation, directional motility, and invasion. To date, the ability of FAK to modulate cell function has been ascribed largely to its control of posttranscriptional signaling cascades in this embryonic cell population. In this paper, we demonstrate that FAK unexpectedly exerts control over an epi...

  7. Influence of fluoride-containing adhesives and bleaching agents on enamel bond strength

    OpenAIRE

    Vanessa Cavalli; Priscila Cristiane Suzy Liporoni; Marcos Augusto do Rego; Sandrine Bittencourt Berger; Marcelo Giannini

    2012-01-01

    This study evaluated the influence of fluoride-containing carbamide peroxide (CP) bleaching agents and adhesive systems on bonded enamel interfaces that are part of the dynamic pH cycling and thermal cycling models. The buccal surfaces of 60 bovine incisors were restored with a composite resin and bonded with three- and two-step, etch-and-rinse, fluoride-containing adhesives, Optibond FL (FL) and Optibond Solo Plus (SP), respectively. Restored teeth were subjected to thermal cycling to age th...

  8. Monocytes mediate metastatic breast tumor cell adhesion to endothelium under flow

    OpenAIRE

    Evani, Shankar J.; Prabhu, Rajesh G.; Gnanaruban, V.; Finol, Ender A.; Anand K. Ramasubramanian

    2013-01-01

    Endothelial adhesion is necessary for the hematogenous dissemination of tumor cells. However, the metastatic breast tumor cell MDA-MB-231 does not bind to the endothelium under physiological flow conditions, suggesting alternate mechanisms of adhesion. Since monocytes are highly represented in the tumor microenvironment, and also bind to endothelium during inflammation, we hypothesized that the monocytes assist in the arrest of MDA-MB-231 on the endothelium. Using in vitro models of the dynam...

  9. Elastic properties determination of CuInSe2 polycrystalline thin films via a dynamic method

    Energy Technology Data Exchange (ETDEWEB)

    Hadjoub, Z; Merdes, S; Hadjoub, I; Doghmane, A, E-mail: z_hadjoub@yahoo.fr [Laboratoire des Semi-Conducteurs, Departement de Physique, Faculte des Sciences, Universite Badji-Mokhtar, BP 12, Annaba, DZ-23000 (Algeria)

    2010-11-15

    Developing and using a simulation program based on the spectrum angular model, we first determine reflectance functions and acoustic signatures for bulk as well as for different thickness of CuInSe2 films. For bulk material, it is found that the longitudinal and Rayleigh modes are excited at incidence angles of 23.4{sup 0} and 47{sup 0}, respectively. This result reveals the great difficulties to characterize CuInSe2 with a conventional scanning acoustic microscope that uses a lens half- opening angle of 50{sup 0} and water as a coupling liquid. Hence, Freon is used as alternative coupling liquid. Consequently, the effect of thickness on reflection coefficient and acoustic signature variations are quantified for both bulk and thin material. It is shown that as the thickness increases: (i) the critical angle of mode excitation increases, (ii) the periods of acoustic signature curves decrease and (iii) the Rayleigh velocity, VR, mode shifts towards lower values. Hence, a velocity dispersion curve is established in terms of VR as a function of film thickness; it decreases initially from the velocity value of the glass substrate then saturates when it reaches that of CuInSe2. The importance of such curve lies in the possibility of velocity determination by just knowing the thickness, and vice versa. Moreover, elastic constants are straight forward deduced from such a velocity.

  10. Host genetics determine susceptibility to avian influenza infection and transmission dynamics

    Science.gov (United States)

    Ruiz-Hernandez, Raul; Mwangi, William; Peroval, Marylene; Sadeyen, Jean-Remy; Ascough, Stephanie; Balkissoon, Devanand; Staines, Karen; Boyd, Amy; McCauley, John; Smith, Adrian; Butter, Colin

    2016-01-01

    Host-genetic control of influenza virus infection has been the object of little attention. In this study we determined that two inbred lines of chicken differing in their genetic background , Lines 0 and C-B12, were respectively relatively resistant and susceptible to infection with the low pathogenicity influenza virus A/Turkey/England/647/77 as defined by substantial differences in viral shedding trajectories. Resistant birds, although infected, were unable to transmit virus to contact birds, as ultimately only the presence of a sustained cloacal shedding (and not oropharyngeal shedding) was critical for transmission. Restriction of within-bird transmission of virus occurred in the resistant line, with intra-nares or cloacal infection resulting in only local shedding and failing to transmit fully through the gastro-intestinal-pulmonary tract. Resistance to infection was independent of adaptive immune responses, including the expansion of specific IFNγ secreting cells or production of influenza-specific antibody. Genetic resistance to a novel H9N2 virus was less robust, though significant differences between host genotypes were still clearly evident. The existence of host-genetic determination of the outcome of influenza infection offers tools for the further dissection of this regulation and also for understanding the mechanisms of influenza transmission within and between birds. PMID:27279280

  11. Host genetics determine susceptibility to avian influenza infection and transmission dynamics.

    Science.gov (United States)

    Ruiz-Hernandez, Raul; Mwangi, William; Peroval, Marylene; Sadeyen, Jean-Remy; Ascough, Stephanie; Balkissoon, Devanand; Staines, Karen; Boyd, Amy; McCauley, John; Smith, Adrian; Butter, Colin

    2016-01-01

    Host-genetic control of influenza virus infection has been the object of little attention. In this study we determined that two inbred lines of chicken differing in their genetic background , Lines 0 and C-B12, were respectively relatively resistant and susceptible to infection with the low pathogenicity influenza virus A/Turkey/England/647/77 as defined by substantial differences in viral shedding trajectories. Resistant birds, although infected, were unable to transmit virus to contact birds, as ultimately only the presence of a sustained cloacal shedding (and not oropharyngeal shedding) was critical for transmission. Restriction of within-bird transmission of virus occurred in the resistant line, with intra-nares or cloacal infection resulting in only local shedding and failing to transmit fully through the gastro-intestinal-pulmonary tract. Resistance to infection was independent of adaptive immune responses, including the expansion of specific IFNγ secreting cells or production of influenza-specific antibody. Genetic resistance to a novel H9N2 virus was less robust, though significant differences between host genotypes were still clearly evident. The existence of host-genetic determination of the outcome of influenza infection offers tools for the further dissection of this regulation and also for understanding the mechanisms of influenza transmission within and between birds. PMID:27279280

  12. Towards the determination of Mytilus edulis food preferences using the dynamic energy budget (DEB) theory.

    Science.gov (United States)

    Picoche, Coralie; Le Gendre, Romain; Flye-Sainte-Marie, Jonathan; Françoise, Sylvaine; Maheux, Frank; Simon, Benjamin; Gangnery, Aline

    2014-01-01

    The blue mussel, Mytilus edulis, is a commercially important species, with production based on both fisheries and aquaculture. Dynamic Energy Budget (DEB) models have been extensively applied to study its energetics but such applications require a deep understanding of its nutrition, from filtration to assimilation. Being filter feeders, mussels show multiple responses to temporal fluctuations in their food and environment, raising questions that can be investigated by modeling. To provide a better insight into mussel-environment interactions, an experiment was conducted in one of the main French growing zones (Utah Beach, Normandy). Mussel growth was monitored monthly for 18 months, with a large number of environmental descriptors measured in parallel. Food proxies such as chlorophyll a, particulate organic carbon and phytoplankton were also sampled, in addition to non-nutritious particles. High-frequency physical data recording (e.g., water temperature, immersion duration) completed the habitat description. Measures revealed an increase in dry flesh mass during the first year, followed by a high mass loss, which could not be completely explained by the DEB model using raw external signals. We propose two methods that reconstruct food from shell length and dry flesh mass variations. The former depends on the inversion of the growth equation while the latter is based on iterative simulations. Assemblages of food proxies are then related to reconstructed food input, with a special focus on plankton species. A characteristic contribution is attributed to these sources to estimate nutritional values for mussels. M. edulis shows no preference between most plankton life history traits. Selection is based on the size of the ingested particles, which is modified by the volume and social behavior of plankton species. This finding reveals the importance of diet diversity and both passive and active selections, and confirms the need to adjust DEB models to different

  13. A feasibility study for experimentally determining dynamic force distribution in a lap joint.

    Energy Technology Data Exchange (ETDEWEB)

    Mayes, Randall Lee

    2013-11-01

    Developing constitutive models of the physics in mechanical joints is currently stymied by inability to measure forces and displacements within the joint. The current state of the art estimates whole joint stiffness and energy loss per cycle from external measured force input and one or two acceleration responses. To validate constitutive models beyond this state requires a measurement of the distributed forces and displacements at the joint interface. Unfortunately, introducing measurement devices at the interface completely disrupts the desired physics. A feasibility study is presented for a non-intrusive method of solving for the interface dynamic forces from an inverse problem using full field measured responses. The responses come from the viewable surface of a beam. The noise levels associated with digital image correlation and continuous scanning laser Doppler velocimetry are evaluated from typical beam experiments. Two inverse problems are simulated. One utilizes the extended Sum of Weighted Accelerations Technique (SWAT). The second is a new approach dubbed the method of truncated orthogonal forces. These methods are much more robust if the contact patch geometry is well identified. Various approaches to identifying the contact patch are investigated, including ion marker tracking, Prussian blue and ultrasonic measurements. A typical experiment is conceived for a beam which has a lap joint at one end with a single bolt connecting it to another identical beam. In a virtual test using the beam finite element analysis, it appears that the SWAT inverse method requires evaluation of too many coefficients to adequately identify the force distribution to be viable. However, the method of truncated orthogonal forces appears viable with current digital image correlation (and probably other) imaging techniques.

  14. Photochemical tissue bonding with chitosan adhesive films

    Directory of Open Access Journals (Sweden)

    Piller Sabine C

    2010-09-01

    Full Text Available Abstract Background Photochemical tissue bonding (PTB is a promising sutureless technique for tissue repair. PTB is often achieved by applying a solution of rose bengal (RB between two tissue edges, which are irradiated by a green laser to crosslink collagen fibers with minimal heat production. In this study, RB has been incorporated in chitosan films to create a novel tissue adhesive that is laser-activated. Methods Adhesive films, based on chitosan and containing ~0.1 wt% RB were manufactured and bonded to calf intestine by a solid state laser (λ = 532 nm, Fluence~110 J/cm2, spot size~0.5 cm. A single-column tensiometer, interfaced with a personal computer, tested the bonding strength. K-type thermocouples recorded the temperature (T at the adhesive-tissue interface during laser irradiation. Human fibroblasts were also seeded on the adhesive and cultured for 48 hours to assess cell growth. Results The RB-chitosan adhesive bonded firmly to the intestine with adhesion strength of 15 ± 2 kPa, (n = 31. The adhesion strength dropped to 0.5 ± 0.1 (n = 8 kPa when the laser was not applied to the adhesive. The average temperature of the adhesive increased from 26°C to 32°C during laser exposure. Fibroblasts grew confluent on the adhesive without morphological changes. Conclusion A new biocompatible chitosan adhesive has been developed that bonds photochemically to tissue with minimal temperature increase.

  15. Gecko adhesion pad: a smart surface?

    Science.gov (United States)

    Pesika, Noshir S.; Zeng, Hongbo; Kristiansen, Kai; Zhao, Boxin; Tian, Yu; Autumn, Kellar; Israelachvili, Jacob

    2009-11-01

    Recently, it has been shown that humidity can increase the adhesion of the spatula pads that form the outermost (adhesive) surface of the tokay gecko feet by 50% relative to the main adhesion mechanism (i.e. van der Waals adhesive forces), although the mechanism by which the enhancement is realized is still not well understood. A change in the surface hydrophobicity of a gecko setal array is observed when the array, which supports the spatulae, is exposed to a water drop for more than 20 min, suggesting a change in the hydrophilic-lyophilic balance (HLB), and therefore of the conformation of the surface proteins. A surface force apparatus (SFA) was used to quantify these changes, i.e. in the adhesion and friction forces, while shearing the setal array against a silica surface under (i) dry conditions, (ii) 100% humidity and (iii) when fully immersed in water. The adhesion increased in the humid environment but greatly diminished in water. Although the adhesion forces changed significantly, the friction forces remained unaffected, indicating that the friction between these highly textured surfaces is 'load-controlled' rather than 'adhesion-controlled'. These results demonstrate that the gecko adhesive pads have the ability to exploit environmental conditions to maximize their adhesion and stabilize their friction forces. Future designs of synthetic dry adhesives inspired by the gecko can potentially include similar 'smart' surfaces that adapt to their environment.

  16. Gecko adhesion pad: a smart surface?

    Energy Technology Data Exchange (ETDEWEB)

    Pesika, Noshir S [Chemical and Biomolecular Engineering Department, Tulane University, New Orleans, LA 70118 (United States); Zeng Hongbo [Chemical and Materials Engineering Department, University of Alberta, Edmonton, AB, T6G 2V4 (Canada); Kristiansen, Kai; Israelachvili, Jacob [Chemical Engineering Department, University of California, Santa Barbara, CA 93117 (United States); Zhao, Boxin [Chemical Engineering Department and Waterloo Institute of Nanotechnology, University of Waterloo, Ontario, N2L 3G1 (Canada); Tian Yu [State Key Laboratory of Tribology, Department of Precision Instruments, Tsinghua University, Beijing 100084 (China); Autumn, Kellar, E-mail: npesika@tulane.ed [Department of Biology, Lewis and Clark College, Portland, OR 97219 (United States)

    2009-11-18

    Recently, it has been shown that humidity can increase the adhesion of the spatula pads that form the outermost (adhesive) surface of the tokay gecko feet by 50% relative to the main adhesion mechanism (i.e. van der Waals adhesive forces), although the mechanism by which the enhancement is realized is still not well understood. A change in the surface hydrophobicity of a gecko setal array is observed when the array, which supports the spatulae, is exposed to a water drop for more than 20 min, suggesting a change in the hydrophilic-lyophilic balance (HLB), and therefore of the conformation of the surface proteins. A surface force apparatus (SFA) was used to quantify these changes, i.e. in the adhesion and friction forces, while shearing the setal array against a silica surface under (i) dry conditions, (ii) 100% humidity and (iii) when fully immersed in water. The adhesion increased in the humid environment but greatly diminished in water. Although the adhesion forces changed significantly, the friction forces remained unaffected, indicating that the friction between these highly textured surfaces is 'load-controlled' rather than 'adhesion-controlled'. These results demonstrate that the gecko adhesive pads have the ability to exploit environmental conditions to maximize their adhesion and stabilize their friction forces. Future designs of synthetic dry adhesives inspired by the gecko can potentially include similar 'smart' surfaces that adapt to their environment.

  17. Cell adhesion defines the topology of endocytosis and signaling.

    Science.gov (United States)

    Grossier, Jean-Philippe; Xouri, Georgia; Goud, Bruno; Schauer, Kristine

    2014-01-01

    Preferred sites of endocytosis have been observed in various cell types, but whether they occur randomly or are linked to cellular cues is debated. Here, we quantified the sites of endocytosis of transferrin (Tfn) and epidermal growth factor (EGF) in cells whose adhesion geometry was defined by micropatterns. 3D probabilistic density maps revealed that Tfn was enriched in adhesive sites during uptake, whereas EGF endocytosis was restricted to the dorsal cellular surface. This spatial separation was not due to distributions of corresponding receptors but was regulated by uptake mechanisms. Asymmetric uptake of Tfn resulted from the enrichment of clathrin and adaptor protein 2 at adhesive areas. Asymmetry in EGF uptake was strongly dependent on the actin cytoskeleton and led to asymmetry in EGF receptor activation. Mild alteration of actin dynamics abolished asymmetry in EGF uptake and decreased EGF-induced downstream signaling, suggesting that cellular adhesion cues influence signal propagation. We propose that restriction of endocytosis at distinct sites allows cells to sense their environment in an "outside-in" mechanism. PMID:24366944

  18. Tuning hydrophobicity and water adhesion by electrospinning and silanization.

    Science.gov (United States)

    Pisuchpen, Thanarath; Chaim-ngoen, Navarun; Intasanta, Narupol; Supaphol, Pitt; Hoven, Voravee P

    2011-04-01

    Electrospinning and silanization were synergistically employed to fabricate poly(vinyl alcohol) (PVA) and PVA/silica mixtures into flexible and chemically modifiable nanostructured surfaces with varying degrees of hydrophobicity and water adhesion. Surfaces possessing the greatest advancing water contact angle yet exhibiting a high level of water adhesion (θ(A)/θ(R) ≈ 168°/0°) were achieved by the reaction of PVA fiber mats with multiple cycles of SiCl(4)/H(2)O treatment, followed by silanization with (1H,1H,2H,2H-perfluorooctyl)trichlorosilane. It is postulated that the strong pinning effect and hence the water adhesion originated from the collapse of the underlying fibrous structures and the removal of air pockets. The addition of silica to the PVA matrix improved the rigidity and thus prevented the fibers from collapsing, allowing air to remain trapped within the fibrous structure and giving the surface greater water repellency. Throughout the investigation, the three wetting models--Wenzel's, Cassie-Baxter's, and the Cassie-impregnating--were regularly referred to as a conceptual framework. The hydrophobic surface that exhibited strong water adhesion, or the so-called "Petal effect", was elucidated in correlation with the fibrous structure of the film, as reviewed by microscopic analysis. In summary, electrospinning as a facile and cost-effective method provides promising opportunities for investigating the mechanistic character of nanowetting, nanoprinting, and nanocoating where the precise control of the dynamical three-phase contact line is of paramount importance. PMID:21401064

  19. Theory and simulations of adhesion receptor dimerization on membrane surfaces.

    Science.gov (United States)

    Wu, Yinghao; Honig, Barry; Ben-Shaul, Avinoam

    2013-03-19

    The equilibrium constants of trans and cis dimerization of membrane bound (2D) and freely moving (3D) adhesion receptors are expressed and compared using elementary statistical-thermodynamics. Both processes are mediated by the binding of extracellular subdomains whose range of motion in the 2D environment is reduced upon dimerization, defining a thin reaction shell where dimer formation and dissociation take place. We show that the ratio between the 2D and 3D equilibrium constants can be expressed as a product of individual factors describing, respectively, the spatial ranges of motions of the adhesive domains, and their rotational freedom within the reaction shell. The results predicted by the theory are compared to those obtained from a novel, to our knowledge, dynamical simulations methodology, whereby pairs of receptors perform realistic translational, internal, and rotational motions in 2D and 3D. We use cadherins as our model system. The theory and simulations explain how the strength of cis and trans interactions of adhesive receptors are affected both by their presence in the constrained intermembrane space and by the 2D environment of membrane surfaces. Our work provides fundamental insights as to the mechanism of lateral clustering of adhesion receptors after cell-cell contact and, more generally, to the formation of lateral microclusters of proteins on cell surfaces. PMID:23528081

  20. Bacterial adhesion and biofilms on surfaces

    Institute of Scientific and Technical Information of China (English)

    Trevor Roger Garrett; Manmohan Bhakoo; Zhibing Zhang

    2008-01-01

    Bacterial adhesion has become a significant problem in industry and in the domicile,and much research has been done for deeper understanding of the processes involved.A generic biological model of bacterial adhesion and population growth called the bacterial biofilm growth cycle,has been described and modified many times.The biofilm growth cycle encompasses bacterial adhesion at all levels,starting with the initial physical attraction of bacteria to a substrate,and ending with the eventual liberation of cell dusters from the biofilm matrix.When describing bacterial adhesion one is simply describing one or more stages of biofilm development,neglecting the fact that the population may not reach maturity.This article provides an overview of bacterial adhesion.cites examples of how bac-terial adhesion affects industry and summarises methods and instrumentation used to improve our understanding of the adhesive prop-erties of bacteria.