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Sample records for adhesion dynamics determines

  1. Targeted Molecular Dynamics to determine Focal Adhesion Targeting Domain Folding Intermediates

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    Pallavi Mohanty

    2017-10-01

    Full Text Available The Focal adhesion kinase (FAT domain of Focal Adhesion Kinase is a four helical bundle known for conformational plasticity. FAT adopts two distinctly different conformations i.e., close (cFAT and arm-exchanged (aeFAT states under native conditions [1]. The slow transition from cFAT to aeFAT is likely to proceed through an open intermediate state that allows YENV motif to attain β-turn conformation and phosphorylation of Y925 by Src kinases [2]. The two end states of FAT are known to interact with Paxillin and are responsible for maintaining steady state in Heart while intermediate conformation interacts with Grb2-SH2 leading to Pathological Cardiac Hypertrophy (PAH [2]. 10ns Targeted Molecular Dynamics (TMD was done between c- and aeFAT in order to explore the conformational transition and to capture pathologically relevant oFAT. Cluster and dynamic cross correlation analysis (DCCA of TMD generated trajectory was done and the selected FAT intermediate was docked with Grb2-SH2 using HADDOCK v2.2 docking followed by molecular dynamics. Conservation analysis of FAT-Grb2 binding site was done using CONSURF [3]. A Pharmacophore FAT-Grb2 complex was generated using SPARKv1.2 and submitted for Virtual screening using BLAZE v4. Drug likeliness and ADMET properties were calculated using MOLINSPIRATION tool. TMD reveals six clusters and DCCA showed positively and negatively correlated region along the transition pathway. Intermediates with competence for Grb2 interaction were docked with Grb2 and best binding complex was further refined. MMPBSA binding energy calculations revealed the best binding pose where the phosphorylated YENV motif of Human FAT interacted with a charged and hydrophobic pocket of Grb2. The conservation analysis showed that the charged pocket was more conserved in comparison with the hydrophobic pocket, hence providing useful insights on binding and specificity determining residues in Grb2. Virtual screening using the pharmacophore

  2. Sliding Adhesion Dynamics of Isolated Gecko Setal Arrays

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    Sponberg, Simon; Autumn, Kellar

    2003-03-01

    The tokay gecko (Gekko gecko) can adhere to nearly any surface through van der Waals interactions of the specialized setae (b-keratin "hairs") of its toe pads. Our recent research has suggested that a gecko is substantially overbuilt for static adhesion requiring as little as 0.03of its theoretical adhesive capacity. We performed the first sliding adhesion experiments on this novel biological adhesive to determine its response to dynamic loading. We isolated arrays of setae and constructed a precision controlled Robo-toe to study sliding effects. Our results indicate that, unlike many typical adhesives, gecko setal arrays exhibit an increased frictional force upon sliding (mk > ms) which further increases with velocity, suggesting that perturbation rejection may be an evolutionary design principle underlying the evolution of the gecko adhesive. We compare these dynamic properties with those of other adhesives and explore the impacts of these results on the design of artificial adhesives.

  3. Role of flexural stiffness of leukocyte microvilli in adhesion dynamics

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    Wu, Tai-Hsien; Qi, Dewei

    2018-03-01

    Previous work reported that microvillus deformation has an important influence on dynamics of cell adhesion. However, the existing studies were limited to the extensional deformation of microvilli and did not consider the effects of their bending deformation on cell adhesion. This Rapid Communication investigates the effects of flexural stiffness of microvilli on the rolling process related to adhesion of leukocytes by using a lattice-Boltzmann lattice-spring method (LLM) combined with adhesive dynamics (AD) simulations. The simulation results reveal that the flexural stiffness of microvilli and their bending deformation have a profound effect on rolling velocity and adhesive forces. As the flexural stiffness of the microvilli decreases, their bending angles increase, resulting in an increase in the number of receptor-ligand bonds and adhesive bonding force and a decrease in the rolling velocity of leukocytes. The effects of flexural stiffness on deformation and adhesion represent crucial factors involved in cell adhesion.

  4. Understanding dynamic changes in live cell adhesion with neutron reflectometry

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    Junghans, Ann

    Understanding the structure and functionality of biological systems on a nanometer-resolution and short temporal scales is important for solving complex biological problems, developing innovative treatment, and advancing the design of highly functionalized biomimetic materials. For example, adhesion of cells to an underlying substrate plays a crucial role in physiology and disease development, and has been investigated with great interest for several decades. In the talk, we would like to highlight recent advances in utilizing neutron scattering to study bio-related structures in dynamic conditions (e . g . under the shear flow) including in-situ investigations of the interfacial properties of living cells. The strength of neutron reflectometry is its non-pertubative nature, the ability to probe buried interfaces with nanometer resolution and its sensitivity to light elements like hydrogen and carbon. That allows us to study details of cell - substrate interfaces that are not accessible with any other standard techniques. We studied the adhesion of human brain tumor cells (U251) to quartz substrates and their responses to the external mechanical forces. Such cells are isolated within the central nervous system which makes them difficult to reach with conventional therapies and therefore making them highly invasive. Our results reveal changes in the thickness and composition of the adhesion layer (a layer between the cell lipid membrane and the quartz substrate), largely composed of hyaluronic acid and associated proteoglycans, when the cells were subjected to shear stress. Further studies will allow us to determine more conditions triggering changes in the composition of the bio-material in the adhesion layer. This, in turn, can help to identify changes that correlate with tumor invasiveness, which can have significant medical impact for the development of targeted anti-invasive therapies.

  5. Determination of the Strength of Adhesion between Lipid Vesicles

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    Tomáš Mareš

    2012-01-01

    Full Text Available A commonly used method to determine the strength of adhesion between adhering lipid vesicles is measuring their effective contact angle from experimental images. The aim of this paper is to estimate the interobserver variations in vesicles effective contact angle measurements and to propose a new method for estimating the strength of membrane vesicle adhesion. Theoretical model shows for the old and for the new measure a monotonic dependence on the strength of adhesion. Results obtained by both measuring techniques show statistically significant correlation and high interobserver reliability for both methods. Therefore the conventional method of measuring the effective contact angle gives qualitatively relevant results as the measure of the lipid vesicle adhesion. However, the new measuring technique provides a lower variation of the measured values than the conventional measures using the effective contact angle. Moreover, obtaining the adhesion angle can be automatized more easily than obtaining the effective contact angle.

  6. Strong dynamical effects during stick-slip adhesive peeling.

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    Dalbe, Marie-Julie; Santucci, Stéphane; Cortet, Pierre-Philippe; Vanel, Loïc

    2014-01-07

    We consider the classical problem of the stick-slip dynamics observed when peeling a roller adhesive tape at a constant velocity. From fast imaging recordings, we extract the dependence of the stick and slip phase durations on the imposed peeling velocity and peeled ribbon length. Predictions of Maugis and Barquins [in Adhesion 12, edited by K. W. Allen, Elsevier ASP, London, 1988, pp. 205-222] based on a quasistatic assumption succeed to describe quantitatively our measurements of the stick phase duration. Such a model however fails to predict the full stick-slip cycle duration, revealing strong dynamical effects during the slip phase.

  7. Adhesion dynamics and durotaxis in migrating cells

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    Harland, Ben; Walcott, Sam; Sun, Sean X.

    2011-02-01

    When tissue cells are plated on a flexible substrate, durotaxis, the directed migration of cells toward mechanically stiff regions, has been observed. Environmental mechanical signals are not only important in cell migration but also seem to influence all aspects of cell differentiation and development, including the metastatic process in cancer cells. Based on a theoretical model suggesting that this mechanosensation has a mechanical basis, we introduce a simple model of a cell by considering the contraction of F-actin bundles containing myosin motors (stress fibers) mediated by the movement of adhesions. We show that, when presented with a linear stiffness gradient, this simple model exhibits durotaxis. Interestingly, since stress fibers do not form on soft surfaces and since adhesion sliding occurs very slowly on hard surfaces, the model predicts that the expected cell velocity reaches a maximum at an intermediate stiffness. This prediction can be experimentally tested. We therefore argue that stiffness-dependent cellular adaptations (mechanosensation) and durotaxis are intimately related and may share a mechanical basis. We therefore identify the essential physical ingredients, which combined with additional biochemical mechanisms can explain durotaxis and mechanosensation in cells.

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

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    Gaspar, Paul D; Willis, F Buck

    2009-01-01

    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 adhesive Capsulitis. Trial Registration Trial Number: NCT00873158 PMID:19735563

  9. Adhesion induced by mobile binders: Dynamics

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    Brochard-Wyart, F.; de Gennes, P. G.

    We consider a vesicle bilayer loaded with molecules that can bind (upon contact) with a solid surface, following the classical model of Bell, Dembo, and Bongrand. We are interested in situations where the contact area varies with time: we assume that binders can then migrate via diffusion. The resulting dissipation and lag create a retarded force on the contact line, which could be significant squeezing or rolling experiments. However, there are two cases where we expect the lag force to be ineffective: (i) separation shrinking of an adhesive patch (where the Evans "tear out" process turns out to be less costly) and (ii) spontaneous growth of a patch from a point contact. In this last case, the lag force is weak, and we give detailed predictions for the growth laws.

  10. Substrate adhesion regulates sealing zone architecture and dynamics in cultured osteoclasts.

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    Fabian Anderegg

    Full Text Available The bone-degrading activity of osteoclasts depends on the formation of a cytoskeletal-adhesive super-structure known as the sealing zone (SZ. The SZ is a dynamic structure, consisting of a condensed array of podosomes, the elementary adhesion-mediating structures of osteoclasts, interconnected by F-actin filaments. The molecular composition and structure of the SZ were extensively investigated, yet despite its major importance for bone formation and remodelling, the mechanisms underlying its assembly and dynamics are still poorly understood. Here we determine the relations between matrix adhesiveness and the formation, stability and expansion of the SZ. By growing differentiated osteoclasts on micro-patterned glass substrates, where adhesive areas are separated by non-adhesive PLL-g-PEG barriers, we show that SZ growth and fusion strictly depend on the continuity of substrate adhesiveness, at the micrometer scale. We present a possible model for the role of mechanical forces in SZ formation and reorganization, inspired by the current data.

  11. The capillary adhesion technique: a versatile method for determining the liquid adhesion force and sample stiffness

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    Daniel Gandyra

    2015-01-01

    Full Text Available We report a novel, practical technique for the concerted, simultaneous determination of both the adhesion force of a small structure or structural unit (e.g., an individual filament, hair, micromechanical component or microsensor to a liquid and its elastic properties. The method involves the creation and development of a liquid meniscus upon touching a liquid surface with the structure, and the subsequent disruption of this liquid meniscus upon removal. The evaluation of the meniscus shape immediately before snap-off of the meniscus allows the quantitative determination of the liquid adhesion force. Concurrently, by measuring and evaluating the deformation of the structure under investigation, its elastic properties can be determined. The sensitivity of the method is remarkably high, practically limited by the resolution of the camera capturing the process. Adhesion forces down to 10 µN and spring constants up to 2 N/m were measured. Three exemplary applications of this method are demonstrated: (1 determination of the water adhesion force and the elasticity of individual hairs (trichomes of the floating fern Salvinia molesta. (2 The investigation of human head hairs both with and without functional surface coatings (a topic of high relevance in the field of hair cosmetics was performed. The method also resulted in the measurement of an elastic modulus (Young’s modulus for individual hairs of 3.0 × 105 N/cm2, which is within the typical range known for human hair. (3 Finally, the accuracy and validity of the capillary adhesion technique was proven by examining calibrated atomic force microscopy cantilevers, reproducing the spring constants calibrated using other methods.

  12. A Method To Determine Adhesion Of Suppository Mass On Excised ...

    African Journals Online (AJOL)

    A method to determine adhesion of suppository mass to intestinal tissue was developed using excised pig intestine. The method which employs the principe of drainage unto and subsequent detachment from the mucosa, of an adherent suppository mass is simple, inexpensive and accurate. Fully optimised, it can be used ...

  13. On the role of adhesion in single-file dynamics

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    Fouad, Ahmed M.; Noel, John A.

    2017-08-01

    For a one-dimensional interacting system of Brownian particles with hard-core interactions (a single-file model), we study the effect of adhesion on both the collective diffusion (diffusion of the entire system with respect to its center of mass) and the tracer diffusion (diffusion of the individual tagged particles). For the case with no adhesion, all properties of these particle systems that are independent of particle labeling (symmetric in all particle coordinates and velocities) are identical to those of non-interacting particles (Lebowitz and Percus, 1967). We clarify this last fact twice. First, we derive our analytical predictions that show that the probability-density functions of single-file (ρsf) and ordinary (ρord) diffusion are identical, ρsf =ρord, predicting a nonanomalous (ordinary) behavior for the collective single-file diffusion, where the average second moment with respect to the center of mass, , is calculated from ρ for both diffusion processes. Second, for single-file diffusion, we show, both analytically and through large-scale simulations, that grows linearly with time, confirming the nonanomalous behavior. This nonanomalous collective behavior comes in contrast to the well-known anomalous sub-diffusion behavior of the individual tagged particles (Harris, 1965). We introduce adhesion to single-file dynamics as a second inter-particle interaction rule and, interestingly, we show that adding adhesion does reduce the magnitudes of both and the mean square displacement per particle Δx2; but the diffusion behavior remains intact independent of adhesion in both cases. Moreover, we study the dependence of both the collective diffusion constant D and the tracer diffusion constant DT on the adhesion coefficient α.

  14. Shape and Dynamics of Adhesive Cells: Mechanical Response of Open Systems

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    Yang, Yuehua; Jiang, Hongyuan

    2017-05-01

    Cell adhesion is an essential biological process. However, previous theoretical and experimental studies ignore a key variable, the changes of cellular volume and pressure, during the dynamic adhesion process. Here, we treat cells as open systems and propose a theoretical framework to investigate how the exchange of water and ions with the environment affects the shape and dynamics of cells adhered between two adhesive surfaces. We show that adherent cells can be either stable (convex or concave) or unstable (spontaneous rupture or collapse) depending on the adhesion energy density, the cell size, the separation of two adhesive surfaces, and the stiffness of the flexible surface. Strikingly, we find that the unstable states vanish when cellular volume and pressure are constant. We further show that the detachments of convex and concave cells are very different. The mechanical response of adherent cells is mainly determined by the competition between the loading rate and the regulation of the cellular volume and pressure. Finally, we show that as an open system the detachment of adherent cells is also significantly influenced by the loading history. Thus, our findings reveal a major difference between living cells and nonliving materials.

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

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    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

  16. Social determinants of health related to adhesion to mammography screening

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    Camila Brasil Moreira

    Full Text Available ABSTRACT Objective: To identify proximal, intermediary and individual social determinants related to mammography adherence, according to the Social Determinants of Health model proposed by Dahlgren and Whitehead. Method: Correlational cross-sectional study, carried out with a sociodemographic and clinical data questionnaire and the Champion's Health Belief Model Scale, translated and adapted for use in Brazil. Data analyzed by multiple linear regression, from the domains scale, and sociodemographic and clinical variables were used as predictors. Results: The age group of 60-64 years (55.0% was highlighted, 22 (55.0% women had a stable partner; and 14 (65.0% completed higher education. The domain with the greatest influence on adhesion to mammography was perceived barriers. Conclusion: The social determinants of health are directly related to the levels of adherence to the exam among women, as well as the perceived benefits, susceptibilities and barriers.

  17. Wavelet Imaging on Multiple Scales (WIMS) reveals focal adhesion distributions, dynamics and coupling between actomyosin bundle stability

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    Toplak, Tim; Palmieri, Benoit; Juanes-García, Alba; Vicente-Manzanares, Miguel; Grant, Martin; Wiseman, Paul W.

    2017-01-01

    We introduce and use Wavelet Imaging on Multiple Scales (WIMS) as an improvement to fluorescence correlation spectroscopy to measure physical processes and features that occur across multiple length scales. In this study, wavelet transforms of cell images are used to characterize molecular dynamics at the cellular and subcellular levels (i.e. focal adhesions). We show the usefulness of the technique by applying WIMS to an image time series of a migrating osteosarcoma cell expressing fluorescently labelled adhesion proteins, which allows us to characterize different components of the cell ranging from optical resolution scale through to focal adhesion and whole cell size scales. Using WIMS we measured focal adhesion numbers, orientation and cell boundary velocities for retraction and protrusion. We also determine the internal dynamics of individual focal adhesions undergoing assembly, disassembly or elongation. Thus confirming as previously shown, WIMS reveals that the number of adhesions and the area of the protruding region of the cell are strongly correlated, establishing a correlation between protrusion size and adhesion dynamics. We also apply this technique to characterize the behavior of adhesions, actin and myosin in Chinese hamster ovary cells expressing a mutant form of myosin IIB (1935D) that displays decreased filament stability and impairs front-back cell polarity. We find separate populations of actin and myosin at each adhesion pole for both the mutant and wild type form. However, we find these populations move rapidly inwards toward one another in the mutant case in contrast to the cells that express wild type myosin IIB where those populations remain stationary. Results obtained with these two systems demonstrate how WIMS has the potential to reveal novel correlations between chosen parameters that belong to different scales. PMID:29049414

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

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    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

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

    DEFF Research Database (Denmark)

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

    2002-01-01

    E-cadherin, an adhesive transmembrane protein of epithelial adherens junctions, forms two types of detergent-resistant dimers: adhesive dimers consisting of cadherin molecules derived from two neighboring cells and lateral dimers incorporating cadherins of the same cell. Both dimers depend...... on the integrity of the same residue, Trp156. While the relative amounts of these complexes are not certain, we show here that in epithelial A-431 cells, adhesive dimers may be a prevalent form. Inactivation of the calcium-binding sites, located between successive cadherin ectodomains, drastically reduced...... the amount of adhesive dimers and concomitantly increased the amount of lateral dimers. A similar interdependence of adhesive and lateral dimers was observed in digitonin-permeabilized cells. In these cells, adhesive dimers immediately disassembled after lowering the Ca2+ concentration below 0.1 m...

  20. Can retinal adhesion mechanisms determine cell-sorting patterns: a test of the differential adhesion hypothesis.

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    Thomas, W A; Yancey, J

    1988-05-01

    Embryonic chick neural retina cells possess two classes of adhesion mechanism, one Ca2+-independent, one Ca2+-dependent, responsible for short-term cell aggregation. This study investigates the role of these mechanisms in the long-term cell sorting potentially relevant to in vivo histogenesis. Retina cells are prepared either with both (E cells) or with only one mechanism (TC cells, CD; LTE cells, CI), respectively. The two types of cell preparations are differentially labelled using fluorescein or rhodamine isothiocyanate, mixed and allowed to aggregate in the presence or absence of cycloheximide at 0.5 microgram ml-1 to retard metabolic recovery of the removed adhesive mechanism. When observed by fluorescence and phase-contrast microscopy, the aggregates formed in cycloheximide show cell sorting, the cells with both mechanisms assuming a more interior position relative to those with a single adhesion mechanism. In parallel hanging-drop experiments, preformed aggregates of cells with a single adhesion mechanism are seen to spread upon aggregates of cells with both mechanisms. No sorting occurs amongst cells from a given stage prepared using any single dissociation protocol. The observed cell sorting would thus seem to derive exclusively from differential cell adhesiveness dependent upon the different dissociation conditions and maintained in the presence of cycloheximide. The experiments support the hypothesis that the dual CI and CD adhesion mechanisms in question can play a central role in governing cell-sorting behaviour during normal histogenesis.

  1. Amino-terminal domain of classic cadherins determines the specificity of the adhesive interactions

    DEFF Research Database (Denmark)

    Klingelhöfer, Jörg; Troyanovsky, R B; Laur, O Y

    2000-01-01

    Classic cadherins are transmembrane receptors involved in cell type-specific calcium-dependent intercellular adhesion. The specificity of adhesion is mediated by homophilic interactions between cadherins extending from opposing cell surfaces. In addition, classic cadherins can self-associate form......Classic cadherins are transmembrane receptors involved in cell type-specific calcium-dependent intercellular adhesion. The specificity of adhesion is mediated by homophilic interactions between cadherins extending from opposing cell surfaces. In addition, classic cadherins can self....... To study lateral and adhesive intercadherin interactions, we examined interactions between two classic cadherins, E- and P-cadherins, in epithelial A-431 cells co-producing both proteins. We showed that these cells exhibited heterocomplexes consisting of laterally assembled E- and P....... The specificity of adhesive interaction was localized to the amino-terminal (EC1) domain of both cadherins. Thus, EC1 domain of classic cadherins exposes two determinants responsible for nonspecific lateral and cadherin type-specific adhesive dimerization....

  2. ADAMTS9-Regulated Pericellular Matrix Dynamics Governs Focal Adhesion-Dependent Smooth Muscle Differentiation

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    Timothy J. Mead

    2018-04-01

    Full Text Available Summary: Focal adhesions anchor cells to extracellular matrix (ECM and direct assembly of a pre-stressed actin cytoskeleton. They act as a cellular sensor and regulator, linking ECM to the nucleus. Here, we identify proteolytic turnover of the anti-adhesive proteoglycan versican as a requirement for maintenance of smooth muscle cell (SMC focal adhesions. Using conditional deletion in mice, we show that ADAMTS9, a secreted metalloprotease, is required for myometrial activation during late gestation and for parturition. Through knockdown of ADAMTS9 in uterine SMC, and manipulation of pericellular versican via knockdown or proteolysis, we demonstrate that regulated pericellular matrix dynamics is essential for focal adhesion maintenance. By influencing focal adhesion formation, pericellular versican acts upstream of cytoskeletal assembly and SMC differentiation. Thus, pericellular versican proteolysis by ADAMTS9 balances pro- and anti-adhesive forces to maintain an SMC phenotype, providing a concrete example of the dynamic reciprocity of cells and their ECM. : Mead et al. identify a proteolytic mechanism that actively maintains a pericellular microenvironment conducive to uterine smooth muscle activation prior to parturition. They show that pericellular matrix proteolysis by the secreted metalloprotease ADAMTS9 is crucial for maintenance of focal adhesions in uterine smooth muscle cells, and its absence impairs parturition. Keywords: metalloprotease, extracellular matrix, smooth muscle, proteoglycan, myometrium, parturition, uterus, focal adhesion, proteolysis, interference reflection microscopy

  3. Stroma regulates increased epithelial lateral cell adhesion in 3D culture: a role for actin/cadherin dynamics.

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    Chambers, Karen F; Pearson, Joanna F; Aziz, Naveed; O'Toole, Peter; Garrod, David; Lang, Shona H

    2011-04-18

    Cell shape and tissue architecture are controlled by changes to junctional proteins and the cytoskeleton. How tissues control the dynamics of adhesion and cytoskeletal tension is unclear. We have studied epithelial tissue architecture using 3D culture models and found that adult primary prostate epithelial cells grow into hollow acinus-like spheroids. Importantly, when co-cultured with stroma the epithelia show increased lateral cell adhesions. To investigate this mechanism further we aimed to: identify a cell line model to allow repeatable and robust experiments; determine whether or not epithelial adhesion molecules were affected by stromal culture; and determine which stromal signalling molecules may influence cell adhesion in 3D epithelial cell cultures. The prostate cell line, BPH-1, showed increased lateral cell adhesion in response to stroma, when grown as 3D spheroids. Electron microscopy showed that 9.4% of lateral membranes were within 20 nm of each other and that this increased to 54% in the presence of stroma, after 7 days in culture. Stromal signalling did not influence E-cadherin or desmosome RNA or protein expression, but increased E-cadherin/actin co-localisation on the basolateral membranes, and decreased paracellular permeability. Microarray analysis identified several growth factors and pathways that were differentially expressed in stroma in response to 3D epithelial culture. The upregulated growth factors TGFβ2, CXCL12 and FGF10 were selected for further analysis because of previous associations with morphology. Small molecule inhibition of TGFβ2 signalling but not of CXCL12 and FGF10 signalling led to a decrease in actin and E-cadherin co-localisation and increased paracellular permeability. In 3D culture models, paracrine stromal signals increase epithelial cell adhesion via adhesion/cytoskeleton interactions and TGFβ2-dependent mechanisms may play a key role. These findings indicate a role for stroma in maintaining adult epithelial tissue

  4. Stroma regulates increased epithelial lateral cell adhesion in 3D culture: a role for actin/cadherin dynamics.

    Directory of Open Access Journals (Sweden)

    Karen F Chambers

    2011-04-01

    Full Text Available Cell shape and tissue architecture are controlled by changes to junctional proteins and the cytoskeleton. How tissues control the dynamics of adhesion and cytoskeletal tension is unclear. We have studied epithelial tissue architecture using 3D culture models and found that adult primary prostate epithelial cells grow into hollow acinus-like spheroids. Importantly, when co-cultured with stroma the epithelia show increased lateral cell adhesions. To investigate this mechanism further we aimed to: identify a cell line model to allow repeatable and robust experiments; determine whether or not epithelial adhesion molecules were affected by stromal culture; and determine which stromal signalling molecules may influence cell adhesion in 3D epithelial cell cultures.The prostate cell line, BPH-1, showed increased lateral cell adhesion in response to stroma, when grown as 3D spheroids. Electron microscopy showed that 9.4% of lateral membranes were within 20 nm of each other and that this increased to 54% in the presence of stroma, after 7 days in culture. Stromal signalling did not influence E-cadherin or desmosome RNA or protein expression, but increased E-cadherin/actin co-localisation on the basolateral membranes, and decreased paracellular permeability. Microarray analysis identified several growth factors and pathways that were differentially expressed in stroma in response to 3D epithelial culture. The upregulated growth factors TGFβ2, CXCL12 and FGF10 were selected for further analysis because of previous associations with morphology. Small molecule inhibition of TGFβ2 signalling but not of CXCL12 and FGF10 signalling led to a decrease in actin and E-cadherin co-localisation and increased paracellular permeability.In 3D culture models, paracrine stromal signals increase epithelial cell adhesion via adhesion/cytoskeleton interactions and TGFβ2-dependent mechanisms may play a key role. These findings indicate a role for stroma in maintaining adult

  5. The Effect of Water on the Work of Adhesion at Epoxy Interfaces by Molecular Dynamics Simulation

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    Hinkley, J.A.; Frankland, S.J.V.; Clancy, T.C.

    2009-01-01

    Molecular dynamics simulation can be used to explore the detailed effects of chemistry on properties of materials. In this paper, two different epoxies found in aerospace resins are modeled using molecular dynamics. The first material, an amine-cured tetrafunctional epoxy, represents a composite matrix resin, while the second represents a 177 C-cured adhesive. Surface energies are derived for both epoxies and the work of adhesion values calculated for the epoxy/epoxy interfaces agree with experiment. Adding water -- to simulate the effect of moisture exposure -- reduced the work of adhesion in one case, and increased it in the other. To explore the difference, the various energy terms that make up the net work of adhesion were compared and the location of the added water was examined.

  6. Differentiation of the drying time of adhesives on plywoods through the dynamic speckle technique

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    Kumari, S.; Nirala, A. K.

    2018-02-01

    The drying time of adhesives such as Fevicol SH, Fevicol MR, Dendrite white and Bulbond after coating separately on the three plywoods, namely Archidply, Centuryply and Greenply, has been studied non-destructively using the dynamic speckle technique. The time history of the speckle pattern, the co-occurrence matrix, 3D graphs and line profiles of images from the time history of the speckle pattern along with 3D trajectory plots have been used for qualitative analysis whereas the inertia moment, absolute value difference, SM index and autocovariance have been used for quantitative analysis. The gray-level co-occurrence matrix has been used for the first time to study the textual parameters of adhesive coated on plywoods during drying. The average drying time of adhesive is a maximum for Bulbond on Archidply (357.25  ±  1.49 min) and a minimum for Dendrite white on Greenply (90.75  ±  2.36 min). Comparative studies among the results obtained for all the four adhesives on the three plywoods reveal that Dendrite white adhesive is the best among the adhesives because it takes the shortest time to dry on all the plywoods, and Greenply is the best among all the plywoods because drying is fastest on it for all the adhesives. Furthermore, it is also concluded that the best plywood and the best adhesive may be decided by knowing the remnant activity.

  7. Electrochemical determination of the onset of bacterial surface adhesion

    Science.gov (United States)

    Jones, Akhenaton-Andrew; Buie, Cullen

    2017-11-01

    Microbial biofouling causes economic loss through corrosion and drag losses on ship hulls, and in oil and food distribution. Microorganisms interacting with surfaces under these open channel flows contend with high shear rates and active transport to the surface. The metallic surfaces they interact with carry charge at various potentials that are little addressed in literature. In this study we demonstrate that the Levich curve, chronoamperometry, and cyclic voltammetry in a rotating disk electrode are ideal for studying adhesion of microbes to metallic surfaces. We study the adhesion of Escherichia coli, Bacillus subtilis, and 1 μm silica microspheres over a 0.15 - 37.33 dynes .cm-2 or shear rates of 14.73 - 3727.28 s-1 range. Our results agree with literature on red blood cells in rotating disk electrodes, deposition rates from optical systems, and show that we can quantify changes in active electrode area by bacteria adhesion and protein secretion. These methods measure changes in area instead of mass, are more accurate than fluorescence microscopy, and apply to a larger range of problems than on-chip flow devices.

  8. Dynamical arrest, percolation, gelation, and glass formation in model nanoparticle dispersions with thermoreversible adhesive interactions.

    Science.gov (United States)

    Eberle, Aaron P R; Castañeda-Priego, Ramón; Kim, Jung M; Wagner, Norman J

    2012-01-24

    We report an experimental study of the dynamical arrest transition for a model system consisting of octadecyl coated silica suspended in n-tetradecane from dilute to concentrated conditions spanning the state diagram. The dispersion's interparticle potential is tuned by temperature affecting the brush conformation leading to a thermoreversible model system. The critical temperature for dynamical arrest, T*, is determined as a function of dispersion volume fraction by small-amplitude dynamic oscillatory shear rheology. We corroborate this transition temperature by measuring a power-law decay of the autocorrelation function and a loss of ergodicity via fiber-optic quasi-elastic light scattering. The structure at T* is measured using small-angle neutron scattering. The scattering intensity is fit to extract the interparticle pair-potential using the Ornstein-Zernike equation with the Percus-Yevick closure approximation, assuming a square-well interaction potential with a short-range interaction (1% of particle diameter). (1) The strength of attraction is characterized using the Baxter temperature (2) and mapped onto the adhesive hard sphere state diagram. The experiments show a continuous dynamical arrest transition line that follows the predicted dynamical percolation line until ϕ ≈ 0.41 where it subtends the predictions toward the mode coupling theory attractive-driven glass line. An alternative analysis of the phase transition through the reduced second virial coefficient B(2)* shows a change in the functional dependence of B(2)* on particle concentration around ϕ ≈ 0.36. We propose this signifies the location of a gel-to-glass transition. The results presented herein differ from those observed for depletion flocculated dispersion of micrometer-sized particles in polymer solutions, where dynamical arrest is a consequence of multicomponent phase separation, suggesting dynamical arrest is sensitive to the physical mechanism of attraction.

  9. ADHESION EFFECTS WITHIN THE HARD MATTER – SOFT MATTER INTERFACE: MOLECULAR DYNAMICS

    Directory of Open Access Journals (Sweden)

    Alexey Tsukanov

    2016-12-01

    Full Text Available In the present study three soft matter – hard matter systems consisting of different nanomaterials and organic molecules were studied using the steered molecular dynamics approach in order to reveal regularities in the formation of organic-inorganic hybrids and the stability of multimolecular complexes, as well as to analyze the energy aspects of adhesion between bio-molecules and layered ceramics. The combined process free energy estimation (COPFEE procedure was used for quantitative and qualitative assessment of the considered heterogeneous systems. Interaction of anionic and cationic amino acids with the surface of a [Mg4Al2(OH122+ 2Cl–] layered double hydroxide (LDH nanosheet was considered. In both cases, strong adhesion was observed despite the opposite signs of electric charge. The free energy of the aspartic amino acid anion, which has two deprotonated carboxylic groups, was determined to be –45 kJ/mol for adsorption on the LDH surface. For the cationic arginine, with only one carboxylic group and a positive net charge, the energy of adsorption was –26 kJ/mol, which is twice higher than that of chloride anion adsorption on the same cationic nanosheet. This fact clearly demonstrates the capability of “soft matter” species to adjust themselves and fit into the surface, minimizing energy of the system. The adsorption of protonated histamine, having no carboxylic groups, on a boehmite nanosheet is also energetically favorable, but the depth of free energy well is quite small at 3.6 kJ/mol. In the adsorbed state the protonated amino-group of histamine plays the role of proton donor, while the hydroxyl oxygens of the layered hydroxide have the role of proton acceptor, which is unusual. The obtained results represent a small step towards further understanding of the adhesion effects within the hard matter – soft matter contact zone.

  10. The detection and role of molecular tension in focal adhesion dynamics.

    Science.gov (United States)

    Hoffman, Brenton D

    2014-01-01

    Cells are exquisitely sensitive to the mechanical nature of their environment, including applied force and the stiffness of the extracellular matrix (ECM). Recent evidence has shown that these variables are critical regulators of diverse processes mediating embryonic development, adult tissue physiology, and many disease states, including cancer, atherosclerosis, and myopathies. Often, detection of mechanical stimuli is mediated by the structures that link cells that surround ECM, the focal adhesions (FAs). FAs are intrinsically force sensitive and display altered dynamics, structure, and composition in response to applied load. While much progress has been made in determining the proteins that localize to and regulate the formation of these structures, less is known about the role of tension across specific proteins in this process. A recently developed class of force-sensitive biosensors is enabling a greater understanding of the molecular bases of cellular mechanosensitivity and cell migration. © 2014 Elsevier Inc. All rights reserved.

  11. The Molecular Architecture of Cell Adhesion: Dynamic Remodeling Revealed by Videonanoscopy

    Directory of Open Access Journals (Sweden)

    Arnauld eSergé

    2016-05-01

    Full Text Available The plasma membrane delimits the cell, which is the basic unit of living organisms, and is also a privileged site for cell communication with the environment. Cell adhesion can occur through cell-cell and cell-matrix contacts. Adhesion proteins such as integrins and cadherins also constitute receptors for inside-out and outside-in signaling within proteolipidic platforms. Adhesion molecule targeting and stabilization relies on specific features such as preferential segregation by the sub-membrane cytoskeleton meshwork and within membrane proteolipidic microdomains. This review presents an overview of the recent insights brought by the latest developments in microscopy, to unravel the molecular remodeling occurring at cell contacts. The dynamic aspect of cell adhesion was recently highlighted by super-resolution videomicroscopy, also named videonanoscopy. By circumventing the diffraction limit of light, nanoscopy has allowed the monitoring of molecular localization and behavior at the single-molecule level, on fixed and living cells. Accessing molecular-resolution details such as quantitatively monitoring components entering and leaving cell contacts by lateral diffusion and reversible association has revealed an unexpected plasticity. Adhesion structures can be highly specialized, such as focal adhesion in motile cells, as well as immune and neuronal synapses. Spatiotemporal reorganization of adhesion molecules, receptors and adaptors directly relates to structure/function modulation. Assembly of these supramolecular complexes is continuously balanced by dynamic events, remodeling adhesions on various timescales, notably by molecular conformation switches, lateral diffusion within the membrane and endo/exocytosis. Pathological alterations in cell adhesion are involved in cancer evolution, through cancer stem cell interaction with stromal niches, growth, extravasation and metastasis.

  12. Probing cellular mechanoadaptation using cell-substrate de-adhesion dynamics: experiments and model.

    Science.gov (United States)

    S S, Soumya; Sthanam, Lakshmi Kavitha; Padinhateeri, Ranjith; Inamdar, Mandar M; Sen, Shamik

    2014-01-01

    Physical properties of the extracellular matrix (ECM) are known to regulate cellular processes ranging from spreading to differentiation, with alterations in cell phenotype closely associated with changes in physical properties of cells themselves. When plated on substrates of varying stiffness, fibroblasts have been shown to exhibit stiffness matching property, wherein cell cortical stiffness increases in proportion to substrate stiffness up to 5 kPa, and subsequently saturates. Similar mechanoadaptation responses have also been observed in other cell types. Trypsin de-adhesion represents a simple experimental framework for probing the contractile mechanics of adherent cells, with de-adhesion timescales shown to scale inversely with cortical stiffness values. In this study, we combine experiments and computation in deciphering the influence of substrate properties in regulating de-adhesion dynamics of adherent cells. We first show that NIH 3T3 fibroblasts cultured on collagen-coated polyacrylamide hydrogels de-adhere faster on stiffer substrates. Using a simple computational model, we qualitatively show how substrate stiffness and cell-substrate bond breakage rate collectively influence de-adhesion timescales, and also obtain analytical expressions of de-adhesion timescales in certain regimes of the parameter space. Finally, by comparing stiffness-dependent experimental and computational de-adhesion responses, we show that faster de-adhesion on stiffer substrates arises due to force-dependent breakage of cell-matrix adhesions. In addition to illustrating the utility of employing trypsin de-adhesion as a biophysical tool for probing mechanoadaptation, our computational results highlight the collective interplay of substrate properties and bond breakage rate in setting de-adhesion timescales.

  13. Modeling cytoskeletal flow over adhesion sites: competition between stochastic bond dynamics and intracellular relaxation

    International Nuclear Information System (INIS)

    Sabass, Benedikt; Schwarz, Ulrich S

    2010-01-01

    In migrating cells, retrograde flow of the actin cytoskeleton is related to traction at adhesion sites located at the base of the lamellipodium. The coupling between the moving cytoskeleton and the stationary adhesions is mediated by the continuous association and dissociation of molecular bonds. We introduce a simple model for the competition between the stochastic dynamics of elastic bonds at the moving interface and relaxation within the moving actin cytoskeleton represented by an internal viscous friction coefficient. Using exact stochastic simulations and an analytical mean field theory, we show that the stochastic bond dynamics lead to biphasic friction laws as observed experimentally. At low internal dissipation, stochastic bond dynamics lead to a regime of irregular stick-and-slip motion. High internal dissipation effectively suppresses cooperative effects among bonds and hence stabilizes the adhesion.

  14. Quantitative analysis of dynamic adhesion properties in human hepatocellular carcinoma cells with fullerenol.

    Science.gov (United States)

    Liu, Yang; Wang, Zuobin; Wang, Xinyue; Huang, Yanhong

    2015-12-01

    In this study, the effect of fullerenol (C60(OH)24) on the cellular dynamic biomechanical behaviors of living human hepatocellular carcinoma (SMCC-7721) cancer cells were investigated by atomic force microscope (AFM) nanoindentation. As an important biomarker of cellular information, the cell adhesion is essential to maintain proper functioning as well as links with the pathogenesis and canceration. Nonetheless, it is challenging to properly evaluate the complex adhesion properties as all the biomechanical parameters interfere with each other. To investigate the dynamic adhesion changes, especially in the case of the fullerenol treatment, the detachment force and work, adhesion events, and membrane tether properties were measured and analyzed systematically with the proposed quantitative method. The statistical analyses suggest that, under the same operating parameters of AFM, the dependence of adhesion energy on the tip-cell contact area is weakened after the fullerenol treatment and the probability of adhesion decreases significantly from 30.6% to 4.2%. In addition, the disruption of the cytoskeleton resulted in a 34% decrease of the average membrane tether force and a 21% increase of the average tether length. Benefiting from the quantitative method, this work contributes to revealing the effects of fullerenol on the cellular biomechanical properties of the living SMCC-7721 cells in a precise and rigorous way and additionally is further instructive to interpret the interaction mechanism of other potential nanomedicines with living cells. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. 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

  16. On the solvability of dynamic elastic-visco-plastic contact problems with adhesion

    Czech Academy of Sciences Publication Activity Database

    Jarušek, Jiří; Sofonea, M.

    2009-01-01

    Roč. 1, č. 2 (2009), s. 191-214 ISSN 2066-6594 R&D Projects: GA AV ČR IAA100750802 Institutional research plan: CEZ:AV0Z10190503 Keywords : elastic-visco-plastic material * dynamic process * frictionless contact * normal compliance * Signorini condition * adhesion * variational formulation * weak solution * a priori estimates Subject RIV: BA - General Mathematics

  17. Continuum mechanics at the atomic scale : Insights into non-adhesive contacts using molecular dynamics simulations

    NARCIS (Netherlands)

    Solhjoo, Soheil; Vakis, Antonis I.

    2016-01-01

    Classical molecular dynamics (MD) simulations were performed to study non-adhesive contact at the atomic scale. Starting from the case of Hertzian contact, it was found that the reduced Young’s modulus E* for shallow indentations scales as a function of, both, the indentation depth and the contact

  18. Molecular dynamics for lateral surface adhesion and peeling behavior of single-walled carbon nanotubes on gold surfaces

    International Nuclear Information System (INIS)

    Huang, Pei-Hsing

    2011-01-01

    Highlights: ► Adhesion and peeling behaviors of SWCNTs are investigated by detailed, fully atomistic MD simulations. ► Adhesion energy of SWCNTs are discussed. ► Dynamical behaviors of SWCNTs in low temperature adhesion are analyzed. ► Adhesion strengths of SWCNTs obtained from MD simulations are compared with the predictions of Hamaker theory and JKR model. - Abstract: Functional gecko-inspired adhesives have attracted a lot of research attention in the last decade. In this work, the lateral surface adhesion and normal peeling-off behavior of single-walled carbon nanotubes (SWCNTs) on gold substrates are investigated by performing detailed, fully atomistic molecular dynamics (MD) simulations. The effects of the diameter and adhered length of CNTs on the adhesive properties were systematically examined. The simulation results indicate that adhesion energies between the SWCNTs and the Au surface varied from 220 to 320 mJ m −2 over the reported chirality range. The adhesion forces on the lateral surface and the tip of the nanotubes obtained from MD simulations agree very well with the predictions of Hamaker theory and Johnson–Kendall–Roberts (JKR) model. The analyses of covalent bonds indicate that the SWCNTs exhibited excellent flexibility and extensibility when adhering at low temperatures (∼100 K). This mechanism substantially increases adhesion time compared to that obtained at higher temperatures (300–700 K), which makes SWCNTs promising for biomimetic adhesives in ultra-low temperature surroundings.

  19. 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.

  20. Two new methods to determine the adhesion by means of internal friction in materials covered with films

    International Nuclear Information System (INIS)

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

    2006-01-01

    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)

  1. Intermittent stick-slip dynamics during the peeling of an adhesive tape from a roller.

    Science.gov (United States)

    Cortet, Pierre-Philippe; Dalbe, Marie-Julie; Guerra, Claudia; Cohen, Caroline; Ciccotti, Matteo; Santucci, Stéphane; Vanel, Loïc

    2013-02-01

    We study experimentally the fracture dynamics during the peeling at a constant velocity of a roller adhesive tape mounted on a freely rotating pulley. Thanks to a high speed camera, we measure, in an intermediate range of peeling velocities, high frequency oscillations between phases of slow and rapid propagation of the peeling fracture. This so-called stick-slip regime is well known as the consequence of a decreasing fracture energy of the adhesive in a certain range of peeling velocity coupled to the elasticity of the peeled tape. Simultaneously with stick slip, we observe low frequency oscillations of the adhesive roller angular velocity which are the consequence of a pendular instability of the roller submitted to the peeling force. The stick-slip dynamics is shown to become intermittent due to these slow pendular oscillations which produce a quasistatic oscillation of the peeling angle while keeping constant the peeling fracture velocity (averaged over each stick-slip cycle). The observed correlation between the mean peeling angle and the stick-slip amplitude questions the validity of the usually admitted independence with the peeling angle of the fracture energy of adhesives.

  2. Determination of the attractive force, adhesive force, adhesion energy and Hamaker constant of soot particles generated from a premixed methane/oxygen flame by AFM

    Science.gov (United States)

    Liu, Ye; Song, Chonglin; Lv, Gang; Chen, Nan; Zhou, Hua; Jing, Xiaojun

    2018-03-01

    Atomic force microscopy (AFM) was used to characterize the attractive force, adhesive force and adhesion energy between an AFM probe tip and nanometric soot particle generated by a premixed methane/oxygen flame. Different attractive force distributions were found when increasing the height above burner (HAB), with forces ranging from 1.1-3.5 nN. As the HAB was increased, the average attractive force initially increased, briefly decreased, and then underwent a gradual increase, with a maximum of 2.54 nN observed at HAB = 25 mm. The mean adhesive force was 6.5-7.5 times greater than the mean attractive force at the same HAB, and values were in the range of 13.5-24.5 nN. The adhesion energy was in the range of 2.0-5.6 × 10-17 J. The variations observed in the average adhesion energy with increasing HAB were different from those of the average adhesion force, implying that the stretched length of soot particles is an important factor affecting the average adhesion energy. The Hamaker constants of the soot particles generated at different HABs were determined from AFM force-separation curves. The average Hamaker constant exhibited a clear correlation with the graphitization degree of soot particles as obtained from Raman spectroscopy.

  3. Dynamic contact problem with adhesion and damage between thermo-electro-elasto-viscoplastic bodies

    Science.gov (United States)

    Hadj ammar, Tedjani; Saïdi, Abdelkader; Azeb Ahmed, Abdelaziz

    2017-05-01

    We study of a dynamic contact problem between two thermo-electro-elasto-viscoplastic bodies with damage and adhesion. The contact is frictionless and is modeled with normal compliance condition. We derive variational formulation for the model and prove an existence and uniqueness result of the weak solution. The proof is based on arguments of evolutionary variational inequalities, parabolic inequalities, differential equations, and fixed point theorem.

  4. ZnO nanostructure-modified QCM for dynamic monitoring of cell adhesion and proliferation.

    Science.gov (United States)

    Reyes, Pavel Ivanoff; Duan, Ziqing; Lu, Yicheng; Khavulya, Dmitry; Boustany, Nada

    2013-03-15

    Noninvasive examination of live cell function in real-time is essential in advancing the understanding of the dynamic progression of cell's biological processes. We present a dynamic and noninvasive method of monitoring the adhesion and proliferation of bovine aortic endothelial cells (BAEC) using a ZnO nanostructure-modified quartz crystal microbalance (ZnOnano-QCM) biosensor. The ZnOnano-QCM biosensor consists of a conventional QCM with ZnO nanostructures directly grown on its sensing electrode deployed in-situ of a standard cell culture environment. Cell adhesion to the ZnO surfaces with various morphologies is studied and the optimal morphology is chosen for the BAEC adhesion. The ZnOnano-QCM biosensor displays enhanced sensitivity compared to the standard QCM sensor with ~10 times higher frequency shift and motional inductance, and ~4 times higher measured motional resistance at full confluency. The dynamic motional resistance and inductance relating to the cells' viscoelastic properties during growth are extracted from the measured time-evolving acoustic spectra. The Butterworth-Van-Dyck (BVD) model is adapted for the ZnOnano-QCM biosensor system and is used to correlate the measured time-evolving acoustic spectra with the motional characteristics of cell attachment and proliferation. Copyright © 2012 Elsevier B.V. All rights reserved.

  5. 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.

  6. 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

    2016-09-01

    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

  7. Tissue organization by cadherin adhesion molecules: dynamic molecular and cellular mechanisms of morphogenetic regulation

    Science.gov (United States)

    Niessen, Carien M.; Leckband, Deborah; Yap, Alpha S.

    2013-01-01

    This review addresses the cellular and molecular mechanisms of cadherin-based tissue morphogenesis. Tissue physiology is profoundly influenced by the distinctive organizations of cells in organs and tissues. In metazoa, adhesion receptors of the classical cadherin family play important roles in establishing and maintaining such tissue organization. Indeed, it is apparent that cadherins participate in a range of morphogenetic events that range from support of tissue integrity to dynamic cellular rearrangements. A comprehensive understanding of cadherin-based morphogenesis must then define the molecular and cellular mechanisms that support these distinct cadherin biologies. Here we focus on four key mechanistic elements: the molecular basis for adhesion through cadherin ectodomains; the regulation of cadherin expression at the cell surface; cooperation between cadherins and the actin cytoskeleton; and regulation by cell signaling. We discuss current progress and outline issues for further research in these fields. PMID:21527735

  8. 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.

  9. Molecular Dynamics Simulations of the Roller Nanoimprint Process: Adhesion and Other Mechanical Characteristics

    Directory of Open Access Journals (Sweden)

    Fang Te-Hua

    2009-01-01

    Full Text Available Abstract Molecular dynamics simulations using tight-binding many body potential are carried out to study the roller imprint process of a gold single crystal. The effect of the roller tooth’s taper angle, imprint depth, imprint temperature, and imprint direction on the imprint force, adhesion, stress distribution, and strain are investigated. A two-stage roller imprint process was obtained from an imprint force curve. The two-stage imprint process included the imprint forming with a rapid increase of imprint force and the unloading stage combined with the adhesion stage. The results show that the imprint force and adhesion rapidly increase with decreasing taper angle and increasing imprint depth. The magnitude of the maximum imprint force and the time at which this maximum occurs are proportional to the imprint depth, but independent of the taper angle. In a comparison of the imprint mechanisms with a vertical imprint case, while high stress and strain regions are concentrated below the mold for vertical imprint, they also occur around the mold in the case of roller imprint. The regions were only concentrated on the substrate atoms underneath the mold in vertical imprint. Plastic flow increased with increasing imprint temperature.

  10. DYNAMIC ADHESIVE WETTABILITY OF POPLAR VENEER WITH COLD OXYGEN PLASMA TREATMENT

    OpenAIRE

    Lijuan Tang,; Rong Zhang,; Xiaoyan Zhou,; Mingzhu Pan,; Minzhi Chen,; Xuehui Yang,; Ping Zhou,; Zhao Chen

    2012-01-01

    Effects of cold oxygen plasma treatment on activating the surface of poplar veneers and improving its wettability were investigated. The veneers were treated with cold oxygen plasma for 1, 3, 5, 7, and 9 min, and aged in air for 1, 3, 7, 14, 21, and 28 days. The dynamic adhesive wettability of veneers was assessed using the contact angle, K-value analysis, and surface free energy. The shear strength of three-layer panels produced from untreated and cold oxygen plasma treated veneers was exami...

  11. Determination of work of adhesion of gelatin hydrogels on a glass substrate

    Science.gov (United States)

    Thakre, Avinash A.; Singh, Arun K.

    2018-04-01

    In this article, work of adhesion (w adh ) of soft gelatin hydrogels on a smooth glass substrate is determined experimentally using the wedge adhesion test. The results showed that w adh decreases with the increase in gelatin concentration in the hydrogels but the same is found to be independent of thickness of hydrogel specimen. These results are used further for establishing a scaling law between w adh and mesh size (ξ) of the three dimensional structure present in the hydrogel as w adh ∼ ξ 8.6. Finite element analysis is also carried out for validating the fracture stability of wedge test in view of analytical prediction. At the end, practical significance of the present study is also discussed.

  12. DETERMINATION OF ADHESIVE STRENGTH LAYER’S ROLLER COMPACTED CONCRETE THE METHOD AXIAL EXTENSION

    Directory of Open Access Journals (Sweden)

    Tang Van Lam

    2017-07-01

    Full Text Available Roller compacted concrete for the construction of hydraulic and hydroelectric buildings is a composite material, which consists of a binder, fine aggregate (sand, coarse aggregate (gravel or crushed stone, water and special additives that provide the desired concrete workability and impart the required concrete performance properties. Concrete mixture is prepared at from concrete mixing plants strictly metered quantities of cement, water, additives and graded aggregates, whereupon they are delivered to the site laying Mixer Truck and sealing layers with each stack layer. The advantages of roller compaction technology should include the reduction of construction time, which allows fast commissioning construction projects, as well as reduce the amount of investment required. One of the main problems encountered in the process of roller compaction of the concrete mix is the need to provide the required adhesion strength between layers of concrete. This paper presents a method for determining the strength of adhesion between the concrete layers of different ages roller compacted concrete using axial tension. This method makes it possible to obtain objective and accurate results with a total thickness of layers of compacted concrete of up to 300…400 mm. Results from this method, studies have shown that the value of strength between the concrete layers in addition to the composition of the concrete and adhesion depends on the quality and the parallel end surfaces of the cylinder-models, which are mounted steel plates for axial tension, as well as the state of the contact surfaces of the concrete layer. The method can be used to determine the strength of interlayer adhesion in roller compacted concrete, which are used in the construction of dams and other hydraulic structures.

  13. 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 DLC-PDMS-h (0.671 ± 0.001 × 10(7)/cm(2) and 0.751 ± 0.002 × 10(7)/cm(2) vs. 1.055 ± 0.002 × 10(7)/cm(2), respectively). No significant differences were detected between other tested materials. Hence DLC-PTFE-h 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 DLC-PTFE-h films could be used as a biomaterial coating without increasing the risk of implant-related infections.

  14. Determination of steroid injection sites using lidocaine test in adhesive capsulitis: A prospective randomized clinical trial.

    Science.gov (United States)

    Kim, Sang Jun; Gee, Albert O; Hwang, Jung Min; Kwon, Jeong Yi

    2015-01-01

    To validate the usefulness of subacromial bursa lidocaine for determination of the therapeutic steroid injection site in patients with adhesive capsulitis Ninety-two patients with adhesive capsulitis were randomly divided into the LC (lidocaine test) group (n = 46), in which LC injection was performed at the subacromial bursa prior to therapeutic steroid injection, and GH (glenohumeral) group (n = 46), in which the steroid was injected into the GH. Patients in the LC group received steroid injection at the subacromial bursa or GH according to the result of the LC. Both groups underwent the same exercise protocol. Improvement of the shoulder pain was checked at 2 weeks and 3 months postinjection and expressed on an ordinal scale. Passive range of motion was recorded preinjection, and 2 weeks and 3 months postinjection. Two weeks postinjection, 37 patients expressed "much improved" and 7 patients expressed "slightly improved" pain levels in the LC group, whereas 18 patients each expressed "much improved" and "slightly improved" pain levels in the GH group, which was significantly different (p adhesive capsulitis. © 2014 Wiley Periodicals, Inc.

  15. Determination of minimum adherend thickness for climbing drum and floating roller adhesive tests

    Science.gov (United States)

    Whitney, T. J.; Askins, D. R.

    1992-01-01

    The Climbing Drum Peel Test (ASTM D1718-76) and the Floating Roller Peel Test (ASTM D3167-76) are adhesive joint tests used to determine adhesive strength in honeycomb core tactical shelter panels. The failure modes and geometries of these tests tend to differ from specimen to specimen, however, depending on the ratio of adhesive strength to flexible adherend stiffness. This inconsistency generates peel strength data which cannot be directly compared. Although the problem can be solved by making the flexible adherend very thick so that all failure geometries are alike, the result is a loss in precision in the test results. An analysis of these test methods was performed in order to specify the minimum flexible adherend thicknesses which produce consistent failures. Experiments confirmed these predictions. Parametric studies and experiments indicate that, among the properties examined, glue line thickness and yield strength of the adherend most affect the minimum adherend thickness which can be used. A first order analysis was also conducted in order to correct the results of peel tests which do not fail in a consistent manner (i.e., the adherends detach from the test fixture rollers).

  16. [Determination of organotin compounds in water soluble paints and adhesives by GC-MS].

    Science.gov (United States)

    Kawakami, Tsuyoshi; Isama, Kazuo; Nakashima, Harunobu; Ooshima, Tomoko; Tsuchiya, Toshie; Matsuoka, Atsuko

    2010-02-01

    The use of tributyltin (TBT) and triphenyltin (TPT) in some household products are prohibited by "Act on the Control of Household Products Containing Harmful Substances" in Japan. In this study, methods for determination of TBT and TPT in water soluble paints and adhesives were developed by GC-MS. These compounds in paints and adhesives, which were mainly composed of vinyl acetate, urethane and acryl resins, and chloroprene rubber, were firstly extracted with HCl-acetone, and then extracted with hexane. On the other hand, the adhesive composed of natural rubber was firstly dispersed in water before acidification. The organotins were extracted with hexane from this solution and then these compounds were extracted with acetonitrile from hexane extract. These extracts were purified by a florisil cartridge column after ethyl-derivation with sodium tetraethylborate, and analyzed by GC-MS. The quantifications using deuterated compound of both organotins as surrogate standard were conducted, and good results were obtained. The recoveries were 81 to 118% and the coefficients of variation were 0.83 to 4.3% (TBT and TPT added; 5 microg/g). The method quantification limits were 0.0090 to 0.025 microg/g, which were lower than those of an official method. These methods were applied to monobutyltin (MBT), dibutyltin (DBT), monophenyltin (MPT), and diphenyltin (DPT). DBT and DPT in paints and adhesives were quantified, except for DPT in natural rubber. These methods were applied to commercial products. DBT was detected at low concentrations (t.r.-0.19 microg/g) in some paint samples, while TBT and TPT were not detected in all samples.

  17. 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)

  18. Dynamic Control of Synaptic Adhesion and Organizing Molecules in Synaptic Plasticity

    Energy Technology Data Exchange (ETDEWEB)

    Rudenko, Gabby (Texas-MED)

    2017-01-01

    Synapses play a critical role in establishing and maintaining neural circuits, permitting targeted information transfer throughout the brain. A large portfolio of synaptic adhesion/organizing molecules (SAMs) exists in the mammalian brain involved in synapse development and maintenance. SAMs bind protein partners, formingtrans-complexes spanning the synaptic cleft orcis-complexes attached to the same synaptic membrane. SAMs play key roles in cell adhesion and in organizing protein interaction networks; they can also provide mechanisms of recognition, generate scaffolds onto which partners can dock, and likely take part in signaling processes as well. SAMs are regulated through a portfolio of different mechanisms that affect their protein levels, precise localization, stability, and the availability of their partners at synapses. Interaction of SAMs with their partners can further be strengthened or weakened through alternative splicing, competing protein partners, ectodomain shedding, or astrocytically secreted factors. Given that numerous SAMs appear altered by synaptic activity, in vivo, these molecules may be used to dynamically scale up or scale down synaptic communication. Many SAMs, including neurexins, neuroligins, cadherins, and contactins, are now implicated in neuropsychiatric and neurodevelopmental diseases, such as autism spectrum disorder, schizophrenia, and bipolar disorder and studying their molecular mechanisms holds promise for developing novel therapeutics.

  19. Parietal pleural invasion/adhesion of subpleural lung cancer: Quantitative 4-dimensional CT analysis using dynamic-ventilatory scanning

    Energy Technology Data Exchange (ETDEWEB)

    Sakuma, Kotaro, E-mail: ksakuma@ohara-hp.or.jp [Department of Radiology, Ohara General Hospital, 6-11 Omachi, Fukushima City, Fukushima 960-8611 (Japan); Department of Radiology and Nuclear Medicine, Fukushima Medical University, 1 Hikariga-oka, Fukushima City, Fukushima 960-1295 (Japan); Yamashiro, Tsuneo, E-mail: clatsune@yahoo.co.jp [Department of Radiology, University of the Ryukyus, 207 Uehara, Nishihara, Okinawa 903-0215 (Japan); Moriya, Hiroshi, E-mail: hrshmoriya@gmail.com [Department of Radiology, Ohara General Hospital, 6-11 Omachi, Fukushima City, Fukushima 960-8611 (Japan); Murayama, Sadayuki, E-mail: sadayuki@med.u-ryukyu.ac.jp [Department of Radiology, University of the Ryukyus, 207 Uehara, Nishihara, Okinawa 903-0215 (Japan); Ito, Hiroshi, E-mail: h-ito@fmu.ac.jp [Department of Radiology and Nuclear Medicine, Fukushima Medical University, 1 Hikariga-oka, Fukushima City, Fukushima 960-1295 (Japan)

    2017-02-15

    Highlights: • 4DCT can be used for assessment of pleural invasion/adhesion by lung cancer. • Quantitative 4DCT indices of lung cancer and adjacent structures are described. • An automatic analysis of pleural invasion/adhesion would be developed in the future. - Abstract: Purpose: Using 4-dimensional dynamic-ventilatory scanning by a 320-row computed tomography (CT) scanner, we performed a quantitative assessment of parietal pleural invasion and adhesion by peripheral (subpleural) lung cancers. Methods: Sixteen patients with subpleural lung cancer underwent dynamic-ventilation CT during free breathing. Neither parietal pleural invasion nor adhesion was subsequently confirmed by surgery in 10 patients, whereas the other 6 patients were judged to have parietal pleural invasion or adhesion. Using research software, we tracked the movements of the cancer and of an adjacent structure such as the rib or aorta, and converted the data to 3-dimensional loci. The following quantitative indices were compared by the Mann-Whitney test: cross-correlation coefficient between time curves for the distances moved from the inspiratory frame by the cancer and the adjacent structure, the ratio of the total movement distances (cancer/adjacent structure), and the cosine similarities between the inspiratory and expiratory vectors (from the cancer to the adjacent structure) and between vectors of the cancer and of the adjacent structure (from inspiratory to expiratory frames). Results: Generally, the movements of the loci of the lung cancer and the adjacent structure were similar in patients with parietal pleural invasion/adhesion, while they were independent in patients without. There were significant differences in all the parameters between the two patient groups (cross-correlation coefficient and the movement distance ratio, P < 0.01; cosine similarities, P < 0.05). Conclusion: These observations suggest that quantitative indices by dynamic-ventilation CT can be utilized as a

  20. Determination of adhesion between thermoplastic and liquid silicone rubbers in hard-soft-combinations via mechanical peeling test

    Science.gov (United States)

    Kühr, C.; Spörrer, A.; Altstädt, V.

    2014-05-01

    The production of hard-soft-combinations via multi injection molding gained more and more importance in the last years. This is attributed to different factors. One principle reason is that the use of two-component injection molding technique has many advantages such as cancelling subsequent and complex steps and shortening the process chain. Furthermore this technique allows the combination of the properties of the single components like the high stiffness of the hard component and the elastic properties of the soft component. Because of the incompatibility of some polymers the adhesion on the interface has to be determined. Thereby adhesion is not only influenced by the applied polymers, but also by the injection molding parameters and the characteristics of the mold. Besides already known combinations of thermoplastics with thermoplastic elastomers (TPE), there consists the possibility to apply liquid silicone rubber (LSR) as soft component. A thermoplastic/LSR combination gains in importance due to the specific advantages of LSR to TPE. The faintly adhesion between LSR and thermoplastics is currently one of the key challenges when dealing with those combinations. So it is coercively necessary to improve adhesion between the two components by adding an adhesion promoter. To determine the promoters influence, it is necessary to develop a suitable testing method to investigate e.g. the peel resistance. The current German standard "VDI Richtlinie 2019', which is actually only employed for thermoplastic/TPE combinations, can serve as a model to determine the adhesion of thermoplastic/LSR combinations.

  1. Dynamic fracture of adhesively bonded composite structures using cohesive zone models

    Science.gov (United States)

    Makhecha, Dhaval P.

    Using experimental data obtained from standard fracture test configurations, theoretical and numerical tools are developed to mathematically describe non-self-similar progression of cracks without specifying an initial crack. A cohesive-decohesive zone model, similar to the cohesive zone model known in the fracture mechanics literature as the Dugdale-Barenblatt model, is adopted to represent the degradation of the material ahead of the crack tip. This model unifies strength-based crack initiation and fracture-mechanics-based crack progression. The cohesive-decohesive zone model is implemented with an interfacial surface material that consists of an upper and a lower surface that are connected by a continuous distribution of normal and tangential nonlinear elastic springs that act to resist either Mode I opening, Mode II sliding, Mode III sliding, or a mixed anode. The initiation of fracture is determined by the interfacial strength and the progression of the crack is determined by the critical energy release rate. The adhesive is idealized with an interfacial surface material to predict interfacial fracture. The interfacial surface material is positioned within the bulk material to predict discrete cohesive cracks. The interfacial surface material is implemented through an interface element, which is incorporated in ABAQUS using the user defined element (UEL) option. A procedure is established to formulate a rate dependent model based on experiments carried out on compact tension test specimens. The rate dependent model is incorporated into the interface element approach to capture the unstable crack growth observed in experiments under quasi-static loading conditions. The compact tension test gives the variation of the fracture toughness with the rate of loading, this information is processed and a relationship between the fracture toughness and the rate of the opening displacement is established. The cohesive-decohesive zone model is implemented through a

  2. Determination of adhesive specific energy of erythrocyte agglutination by laser retrodiffusion

    Science.gov (United States)

    Rasia, R. J.; de Isla, N.; Altube, L.; Stoltz, J. F.; Valverde, J.

    2003-05-01

    The quality of an antibody is related to its affinity expressed by the equilibrium constant. The biological activity of an antibody can be estimated by the strength of antigen-antibody bridges. An optical method is proposed to estimate the specific binding energy using the dissociation behavior of suspended RBC agglutinates in a shear flow and measuring laser backscattering. A constant increase of intensity was observed when the shear stress raises, pointing to a progressive dissociation of RBC agglutinates into smaller ones. The final break-up of two-cell rouleaux is produced at critical shear stress ( τc), which reflects the mechanical action required to dissociate the molecular bridges between cells. The critical shear stress permitted to define the specific surface adhesive energy ( Γ) by using the Derjaguin relation. The determination of τc provides a good way to assess the functional characterization of specific immunoglobulins, which could be very useful for antibody quality control.

  3. 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.)

  4. 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...

  5. Enterococcus faecalis surface proteins determine its adhesion mechanism to bile drain materials

    NARCIS (Netherlands)

    Waar, K; van der Mei, HC; Harmsen, HJM; Degener, JE; Busscher, HJ

    An important step in infections associated with biliary drains is adhesion of micro-organisms to the surface. In this study the role of three surface proteins of Enterococcus faecalis (enterococcal surface protein, aggregation substances 1 and 373) in the adhesion to silicone rubber,

  6. Structural determinants of adhesion by Protocadherin-19 and implications for its role in epilepsy

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, Sharon R.; Jontes, James D.; Sotomayor, Marcos

    2016-10-26

    Non-clustered δ-protocadherins are homophilic cell adhesion molecules essential for the development of the vertebrate nervous system, as several are closely linked to neurodevelopmental disorders. Mutations inprotocadherin-19(PCDH19) result in a female-limited, infant-onset form of epilepsy (PCDH19-FE). Over 100 mutations inPCDH19have been identified in patients with PCDH19-FE, about half of which are missense mutations in the adhesive extracellular domain. Neither the mechanism of homophilic adhesion by PCDH19, nor the biochemical effects of missense mutations are understood. Here we present a crystallographic structure of the minimal adhesive fragment of the zebrafish Pcdh19 extracellular domain. This structure reveals the adhesive interface for Pcdh19, which is broadly relevant to both non-clustered δ and clustered protocadherin subfamilies. In addition, we show that several PCDH19-FE missense mutations localize to the adhesive interface and abolish Pcdh19 adhesion inin vitroassays, thus revealing the biochemical basis of their pathogenic effects during brain development.

  7. Molecular dynamics study on the effects of stamp shape, adhesive energy, and temperature on the nanoimprint lithography process

    International Nuclear Information System (INIS)

    Kang, Ji-Hoon; Kim, Kwang-Seop; Kim, Kyung-Woong

    2010-01-01

    Molecular dynamics simulations of nanoimprint lithography (NIL) were performed to investigate the effects of three critical process parameters in NIL: stamp shape, adhesive energy between the stamp and polymer film, and imprint temperature. The proposed simulation model of the NIL process consists of an amorphous SiO 2 stamp with a line pattern, an amorphous poly(methylmethacrylate) film, and a Si substrate under the periodic boundary condition in the horizontal direction to simulate a real NIL process imprinting periodical line patterns. The behavior of polymer deformation and the effects of adhesion on pattern transfer were investigated by observing the deformation process, calculating the imprint and separation forces, and analyzing the density and stress distribution inside the polymer film. In addition, their dependency on the process parameters is also discussed with reference to the changes in pattern shape, adhesive energy between the stamp and polymer atoms, and imprint temperature of the polymer film. During the imprint process, the rectangular pattern shows inferior cavity filling and higher stress concentration compared to trapezoidal and triangular patterns because it requires much larger flow and deformation of the polymer film. Low imprint temperature also produces high stress concentration and large imprint force due to the lower fluidity of polymer film. In the separation process, the rectangular pattern generates the largest separation force and causes the most serious defects of the transferred pattern and even the polymer film, while the triangular pattern shows the most satisfactory pattern transfer. In addition, the adhesive energy between the stamp and the polymer film also strongly influences the adhesion between the stamp and the polymer film. Low adhesive energy reduces the separation force of the stamp and transferred pattern defects, and therefore enhances the quality of pattern transfer.

  8. Evaluation and criterion determination of the low-k thin film adhesion by the surface acoustic waves with cohesive zone model

    Science.gov (United States)

    Xiao, Xia; Qi, Haiyang; Sui, Xiaole; Kikkawa, Takamaro

    2017-03-01

    The cohesive zone model (CZM) is introduced in the surface acoustic wave (SAW) technique to characterize the interfacial adhesion property of the low-k thin film deposited on the Silicon substrate. The ratio of the two parameters in the CZM, the maximum normal traction and normal interface characteristic length, is derived to evaluate the interfacial adhesion properties quantitatively. In this study, the adhesion criterion to judge the adhesion property is newly proposed by the CZM-SAW technique. The criterion determination processes of two kinds of film, dense and porous Black Diamond with different film thicknesses, are presented in this paper. The interfacial adhesion properties of the dense and porous Black Diamond films with different thicknesses are evaluated by the CZM-SAW technique quantitatively and nondestructively. The quantitative adhesion properties are obtained by fitting the experimental dispersion curves with maximum frequency up to 220 MHz with the theoretical ones. Results of the nondestructive CZM-SAW technique and the destructive nanoscratch exhibit the same trend in adhesion properties, which means that the CZM-SAW technique is a promising method for determining the interfacial adhesion. Meanwhile, the adhesion properties of the detected samples are judged by the determined criterion. The test results show that different test film materials with different film thicknesses ranging from 300 nm to 1000 nm are in different adhered conditions. This paper exhibits the advantage of the CZM-SAW technique which can be a universal method to characterize the film adhesion.

  9. Amino-terminal domain of classic cadherins determines the specificity of the adhesive interactions

    DEFF Research Database (Denmark)

    Klingelhöfer, Jörg; Troyanovsky, R B; Laur, O Y

    2000-01-01

    Classic cadherins are transmembrane receptors involved in cell type-specific calcium-dependent intercellular adhesion. The specificity of adhesion is mediated by homophilic interactions between cadherins extending from opposing cell surfaces. In addition, classic cadherins can self......-associate forming lateral dimers. Whereas it is widely excepted that lateral dimerization of cadherins is critical for adhesion, details of this process are not known. Yet, no evidence for physical association between different classic cadherins in cells expressing complex cadherin patterns has been reported....... To study lateral and adhesive intercadherin interactions, we examined interactions between two classic cadherins, E- and P-cadherins, in epithelial A-431 cells co-producing both proteins. We showed that these cells exhibited heterocomplexes consisting of laterally assembled E- and P...

  10. Enterococcus faecalis surface proteins determine its adhesion mechanism to bile drain materials.

    Science.gov (United States)

    Waar, Karola; van der Mei, Henny C; Harmsen, Hermie J M; Degener, John E; Busscher, Henk J

    2002-06-01

    An important step in infections associated with biliary drains is adhesion of micro-organisms to the surface. In this study the role of three surface proteins of Enterococcus faecalis (enterococcal surface protein, aggregation substances 1 and 373) in the adhesion to silicone rubber, fluoro-ethylene-propylene and polyethylene was examined. Four isogenic E. faecalis strains with and without aggregation substances and one strain expressing enterococcal surface protein were used. The kinetics of enterococcal adhesion to the materials was measured in situ in a parallel plate flow chamber. Initial deposition rates were similar for all strains, whereas the presence of surface proteins increased the total number of adhering bacteria. Nearest neighbour analysis demonstrated that enterococci expressing the whole sex-pheromone plasmid encoding aggregation substances 1 or 373 adhered in higher numbers through mechanisms of positive cooperativity, which means that adhesion of bacteria enhances the probability of adhesion of other bacteria near these bacteria. Enterococci with the enterococcal surface protein did not adhere through this mechanism. These findings indicate that the surface proteins of E. faecalis play a key role in the adhesion to bile drains and bile drain associated infections.

  11. Multiscale approaches to protein-mediated interactions between membranes—relating microscopic and macroscopic dynamics in radially growing adhesions

    International Nuclear Information System (INIS)

    Bihr, Timo; Smith, Ana-Suncana; Seifert, Udo

    2015-01-01

    Macromolecular complexation leading to coupling of two or more cellular membranes is a crucial step in a number of biological functions of the cell. While other mechanisms may also play a role, adhesion always involves the fluctuations of deformable membranes, the diffusion of proteins and the molecular binding and unbinding. Because these stochastic processes couple over a multitude of time and length scales, theoretical modeling of membrane adhesion has been a major challenge. Here we present an effective Monte Carlo scheme within which the effects of the membrane are integrated into local rates for molecular recognition. The latter step in the Monte Carlo approach enables us to simulate the nucleation and growth of adhesion domains within a system of the size of a cell for tens of seconds without loss of accuracy, as shown by comparison to 10 6 times more expensive Langevin simulations. To perform this validation, the Langevin approach was augmented to simulate diffusion of proteins explicitly, together with reaction kinetics and membrane dynamics. We use the Monte Carlo scheme to gain deeper insight to the experimentally observed radial growth of micron sized adhesion domains, and connect the effective rate with which the domain is growing to the underlying microscopic events. We thus demonstrate that our technique yields detailed information about protein transport and complexation in membranes, which is a fundamental step toward understanding even more complex membrane interactions in the cellular context. (paper)

  12. Multiscale approaches to protein-mediated interactions between membranes—relating microscopic and macroscopic dynamics in radially growing adhesions

    Science.gov (United States)

    Bihr, Timo; Seifert, Udo; Smith, Ana-Sunčana

    2015-08-01

    Macromolecular complexation leading to coupling of two or more cellular membranes is a crucial step in a number of biological functions of the cell. While other mechanisms may also play a role, adhesion always involves the fluctuations of deformable membranes, the diffusion of proteins and the molecular binding and unbinding. Because these stochastic processes couple over a multitude of time and length scales, theoretical modeling of membrane adhesion has been a major challenge. Here we present an effective Monte Carlo scheme within which the effects of the membrane are integrated into local rates for molecular recognition. The latter step in the Monte Carlo approach enables us to simulate the nucleation and growth of adhesion domains within a system of the size of a cell for tens of seconds without loss of accuracy, as shown by comparison to 106 times more expensive Langevin simulations. To perform this validation, the Langevin approach was augmented to simulate diffusion of proteins explicitly, together with reaction kinetics and membrane dynamics. We use the Monte Carlo scheme to gain deeper insight to the experimentally observed radial growth of micron sized adhesion domains, and connect the effective rate with which the domain is growing to the underlying microscopic events. We thus demonstrate that our technique yields detailed information about protein transport and complexation in membranes, which is a fundamental step toward understanding even more complex membrane interactions in the cellular context.

  13. Cell fate determination dynamics in bacteria

    Science.gov (United States)

    Kuchina, Anna; Espinar, Lorena; Cagatay, Tolga; Garcia-Ojalvo, Jordi; Suel, Gurol

    2010-03-01

    The fitness of an organism depends on many processes that serve the purpose to adapt to changing environment in a robust and coordinated fashion. One example of such process is cellular fate determination. In the presence of a variety of alternative responses each cell adopting a particular fate represents a ``choice'' that must be tightly regulated to ensure the best survival strategy for the population taking into account the broad range of possible environmental challenges. We investigated this problem in the model organism B.Subtilis which under stress conditions differentiates terminally into highly resistant spores or initiates an alternative transient state of competence. The dynamics underlying cell fate choice remains largely unknown. We utilize quantitative fluorescent microscopy to track the activities of genes involved in these responses on a single-cell level. We explored the importance of temporal interactions between competing cell fates by re- engineering the differentiation programs. I will discuss how the precise dynamics of cellular ``decision-making'' governed by the corresponding biological circuits may enable cells to adjust to diverse environments and determine survival.

  14. Atomic force microscope adhesion measurements and atomistic molecular dynamics simulations at different humidities

    International Nuclear Information System (INIS)

    Seppä, Jeremias; Sairanen, Hannu; Korpelainen, Virpi; Husu, Hannu; Heinonen, Martti; Lassila, Antti; Reischl, Bernhard; Raiteri, Paolo; Rohl, Andrew L; Nordlund, Kai

    2017-01-01

    Due to their operation principle atomic force microscopes (AFMs) are sensitive to all factors affecting the detected force between the probe and the sample. Relative humidity is an important and often neglected—both in experiments and simulations—factor in the interaction force between AFM probe and sample in air. This paper describes the humidity control system designed and built for the interferometrically traceable metrology AFM (IT-MAFM) at VTT MIKES. The humidity control is based on circulating the air of the AFM enclosure via dryer and humidifier paths with adjustable flow and mixing ratio of dry and humid air. The design humidity range of the system is 20–60 %rh. Force–distance adhesion studies at humidity levels between 25 %rh and 53 %rh are presented and compared to an atomistic molecular dynamics (MD) simulation. The uncertainty level of the thermal noise method implementation used for force constant calibration of the AFM cantilevers is 10 %, being the dominant component of the interaction force measurement uncertainty. Comparing the simulation and the experiment, the primary uncertainties are related to the nominally 7 nm radius and shape of measurement probe apex, possible wear and contamination, and the atomistic simulation technique details. The interaction forces are of the same order of magnitude in simulation and measurement (5 nN). An elongation of a few nanometres of the water meniscus between probe tip and sample, before its rupture, is seen in simulation upon retraction of the tip in higher humidity. This behaviour is also supported by the presented experimental measurement data but the data is insufficient to conclusively verify the quantitative meniscus elongation. (paper)

  15. 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.

  16. A model of the effects of cancer cell motility and cellular adhesion properties on tumour-immune dynamics.

    Science.gov (United States)

    Frascoli, Federico; Flood, Emelie; Kim, Peter S

    2017-06-01

    We present a three-dimensional model simulating the dynamics of an anti-cancer T-cell response against a small, avascular, early-stage tumour. Interactions at the tumour site are accounted for using an agent-based model (ABM), while immune cell dynamics in the lymph node are modelled as a system of delay differential equations (DDEs). We combine these separate approaches into a two-compartment hybrid ABM-DDE system to capture the T-cell response against the tumour. In the ABM at the tumour site, movement of tumour cells is modelled using effective physical forces with a specific focus on cell-to-cell adhesion properties and varying levels of tumour cell motility, thus taking into account the ability of cancer cells to spread and form clusters. We consider the effectiveness of the immune response over a range of parameters pertaining to tumour cell motility, cell-to-cell adhesion strength and growth rate. We also investigate the dependence of outcomes on the distribution of tumour cells. Low tumour cell motility is generally a good indicator for successful tumour eradication before relapse, while high motility leads, almost invariably, to relapse and tumour escape. In general, the effect of cell-to-cell adhesion on prognosis is dependent on the level of tumour cell motility, with an often unpredictable cross influence between adhesion and motility, which can lead to counterintuitive effects. In terms of overall tumour shape and structure, the spatial distribution of cancer cells in clusters of various sizes has shown to be strongly related to the likelihood of extinction. © The authors 2016. Published by Oxford University Press on behalf of the Institute of Mathematics and its Applications. All rights reserved.

  17. Tris(trimethylsilyl)silane as a co-initiator for dental adhesive: Photo-polymerization kinetics and dynamic mechanical property.

    Science.gov (United States)

    Song, Linyong; Ye, Qiang; Ge, Xueping; Misra, Anil; Spencer, Paulette

    2016-01-01

    The purpose of this study was to evaluate the polymerization behavior of a model dentin adhesive with tris(trimethylsilyl)silane (TTMSS) as a co-initiator, and to investigate the polymerization kinetics and mechanical properties of copolymers in dry and wet conditions. A co-monomer mixture based on HEMA/BisGMA (45/55, w/w) was used as a model dentin adhesive. The photoinitiator system included camphorquinone (CQ) as the photosensitizer and the co-initiator was ethyl-4-(dimethylamino) benzoate (EDMAB) or TTMSS. Iodonium salt, diphenyliodonium hexafluorophosphate (DPIHP) serving as a catalyst, was selectively added into the adhesive formulations. The control and the experimental formulations were characterized with regard to the degree of conversion (DC) and dynamic mechanical properties under dry and wet conditions. In two-component photoinitiator system (CQ/TTMSS), with an increase of TTMSS concentration, the polymerization rate and DC of CC double bond increased, and showed a dependence on the irradiation time and curing light intensity. The copolymers that contained the three-component photoinitiator system (CQ/TTMSS/DPIHP) showed similar dynamic mechanical properties, under both dry and wet conditions, to the EDMAB-containing system. The DC of formulations using TTMSS as co-initiator showed a strong dependence on irradiation time. With the addition of TTMSS, the maximum polymerization rate can be adjusted and the network structure became more homogenous. The results indicated that the TTMSS could be used as a substitute for amine-type co-initiator in visible-light induced free radical polymerization of methacrylate-based dentin adhesives. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  18. 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

    2016-03-21

    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

  19. 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

  20. The dynamic sublayers for improving the adhesion of CVD diamond films on copper

    Science.gov (United States)

    Gaydaychuk, A. V.; Linnik, S. A.; Okhotnikov, V. V.

    2017-05-01

    Polycrystalline diamond films were fabricated on copper substrates by a multi-step process comprised of physical vapor deposition of Al-based composite interlayer on Cu substrate and depositing continuous diamond film on composite interlayer by plasma assisted chemical vapor deposition (PACVD). The interface characteristics and adhesion strength were investigated by Auger electron spectroscopy, Raman analysis, calotest and indentation test. The results show that the continuous film without cracks is successfully obtained. The improved adhesion between diamond film and substrate results from the low residual stress in the film due to their compensation by Al interlayer in the sample cooling process.

  1. Integration of actin dynamics and cell adhesion by a three-dimensional, mechanosensitive molecular clutch.

    Science.gov (United States)

    Case, Lindsay B; Waterman, Clare M

    2015-08-01

    During cell migration, the forces generated in the actin cytoskeleton are transmitted across transmembrane receptors to the extracellular matrix or other cells through a series of mechanosensitive, regulable protein-protein interactions termed the molecular clutch. In integrin-based focal adhesions, the proteins forming this linkage are organized into a conserved three-dimensional nano-architecture. Here we discuss how the physical interactions between the actin cytoskeleton and focal-adhesion-associated molecules mediate force transmission from the molecular clutch to the extracellular matrix.

  2. Inside-out signaling promotes dynamic changes in the carcinoembryonic antigen-related cellular adhesion molecule 1 (CEACAM1) oligomeric state to control its cell adhesion properties.

    Science.gov (United States)

    Patel, Prerna C; Lee, Hannah S W; Ming, Aaron Y K; Rath, Arianna; Deber, Charles M; Yip, Christopher M; Rocheleau, Jonathan V; Gray-Owen, Scott D

    2013-10-11

    Cell-cell contacts are fundamental to multicellular organisms and are subject to exquisite levels of control. The carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) can engage in both cis-homophilic (parallel) oligomerization and trans-homophilic (anti-parallel) binding. In this study, we establish that the CEACAM1 transmembrane domain has a propensity to form cis-dimers via the transmembrane-embedded (432)GXXXG(436) motif and that this basal state is overcome when activated calmodulin binds to the CEACAM1 cytoplasmic domain. Although mutation of the (432)GXXXG(436) motif reduced CEACAM1 oligomerization, it did not affect surface localization of the receptor or influence CEACAM1-dependent cellular invasion by the pathogenic Neisseria. The mutation did, however, have a striking effect on CEACAM1-dependent cellular aggregation, increasing both the kinetics of cell-cell association and the size of cellular aggregates formed. CEACAM1 association with tyrosine kinase c-Src and tyrosine phosphatases SHP-1 and SHP-2 was not affected by the (432)GXXXG(436) mutation, consistent with their association with the monomeric form of wild type CEACAM1. Collectively, our results establish that a dynamic oligomer-to-monomer shift in surface-expressed CEACAM1 facilitates trans-homophilic binding and downstream effector signaling.

  3. Determining postmortem interval using glycoproteinous adhesion deposits by Balanus improvisus on human skeletal and dental remains.

    Science.gov (United States)

    Bytheway, Joan A; Pustilnik, Stephen M

    2013-01-01

    An anthropological analysis was conducted on skeletal and dental remains brought to the Galveston County Medical Examiner's office. The skeletal remains were dry, fragmented, and absent of typical fluvial characteristics. During microscopic examination, semitransparent, circular objects were discovered on the dentition, the mandible, tibial plateau, and distal femur. The objects were glycoproteinous adhesions deposited by the acorn barnacle, Balanus improvisus. B. improvisus is an intertidal barnacle found in estuaries in Galveston Bay. Basal diameter of the adhesions on the dentition were significantly smaller than those found on the postcranial bones (p = 0.010), indicating two consecutive cohorts adhered to the bone and dentition. As settlement typically occurs once a year, this would indicate that the remains were in the fluvial environment for at least 375-410 days. It is important in geographic areas that have prevalent fluvial environments that human remains, particularly dentition, are microscopically examined for marine life evidence. © 2012 American Academy of Forensic Sciences.

  4. 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.

  5. Topography on a subcellular scale modulates cellular adhesions and actin stress fiber dynamics in tumor associated fibroblasts

    Science.gov (United States)

    Azatov, Mikheil; Sun, Xiaoyu; Suberi, Alexandra; Fourkas, John T.; Upadhyaya, Arpita

    2017-12-01

    Cells can sense and adapt to mechanical properties of their environment. The local geometry of the extracellular matrix, such as its topography, has been shown to modulate cell morphology, migration, and proliferation. Here we investigate the effect of micro/nanotopography on the morphology and cytoskeletal dynamics of human pancreatic tumor-associated fibroblast cells (TAFs). We use arrays of parallel nanoridges with variable spacings on a subcellular scale to investigate the response of TAFs to the topography of their environment. We find that cell shape and stress fiber organization both align along the direction of the nanoridges. Our analysis reveals a strong bimodal relationship between the degree of alignment and the spacing of the nanoridges. Furthermore, focal adhesions align along ridges and form preferentially on top of the ridges. Tracking actin stress fiber movement reveals enhanced dynamics of stress fibers on topographically patterned surfaces. We find that components of the actin cytoskeleton move preferentially along the ridges with a significantly higher velocity along the ridges than on a flat surface. Our results suggest that a complex interplay between the actin cytoskeleton and focal adhesions coordinates the cellular response to micro/nanotopography.

  6. Determinants of Welfare Dynamics in Rural Nicaragua

    DEFF Research Database (Denmark)

    Jakobsen, Kristian Thor

    2011-01-01

    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...... in explaining poverty movements. Moreover, climate-related shocks such as droughts and pest attacks not only have persistent and adverse impacts on household consumption, but also affect households’ productive asset holdings, which could affect their income-generating potential in the longer term....

  7. Adhesive bonding layer properties - calculated and experimentally determined; Klebschichtkennwerte aus Experiment und Simulation. Simulationsgestuetzter Zugscherversuch mit dicken gestuften Fuegeteilen

    Energy Technology Data Exchange (ETDEWEB)

    Gegner, J. [SKF Kugellagerfabriken GmbH, Schweinfurt (Germany); Oechsner, A. [Erlangen-Nuernberg Univ., Erlangen (Germany). Lehrstuhl fuer Technische Mechanik

    2001-07-01

    In this contribution, important procedures for testing of adhesive bondings are presented. The strain-shear test with thick joined parts represents the basic online test procedure. An optimized test procedure and an extended data evaluation are described. By application of the finite element method an identification procedure has been developed, in order to get adhesive bonding layer properties for modelling of complex components which cannot be determined by such basic procedures. The new tool for materials testing has been applied to a silicon sealing substance for joined parts made of steel and aluminium. (orig.) [German] Der vorliegende Beitrag stellt wichtige Methoden zur Materialpruefung in der Klebtechnik vor: Der Zugscherversuch mit dicken Fuegeteilen bildet das In-situ-Basis-Testverfahren. Es werden die verbesserte Versuchstechnik und die erweiterte Messdatenauswertung beschrieben. Mit Hilfe der Finite-Elemente-Methode wurde ein Identifikationsverfahren entwickelt, um aus diesem einen Grundversuch nicht direkt bestimmbare Klebschichtkennwerte fuer die Modellierung komplexer Bauelemente zu entnehmen. Das neue Werkzeug der Materialpruefung wird auf ein Silikon-Dichtmittel mit Fuegeteilen aus Aluminium beziehungsweise Stahl angewandt. (orig.)

  8. Dynamic Capital Structure: Dynamics, Determinants and Speed of Adjustment

    NARCIS (Netherlands)

    Tamirat, A.S.; Trujillo Barrera, A.A.; Pennings, J.M.E.

    2017-01-01

    The corporate finance literature has focused on explaining the determinants of firms target capital structure and speed of adjustment using the well-established theories such as pecking order, signaling and trade-off theories. However, less attention has been paid to understanding the financing

  9. MVL-PLA2, a snake venom phospholipase A2, inhibits angiogenesis through an increase in microtubule dynamics and disorganization of focal adhesions.

    Directory of Open Access Journals (Sweden)

    Amine Bazaa

    Full Text Available Integrins are essential protagonists of the complex multi-step process of angiogenesis that has now become a major target for the development of anticancer therapies. We recently reported and characterized that MVL-PLA2, a novel phospholipase A2 from Macrovipera lebetina venom, exhibited anti-integrin activity. In this study, we show that MVL-PLA2 also displays potent anti-angiogenic properties. This phospholipase A2 inhibited adhesion and migration of human microvascular-endothelial cells (HMEC-1 in a dose-dependent manner without being cytotoxic. Using Matrigel and chick chorioallantoic membrane assays, we demonstrated that MVL-PLA2, as well as its catalytically inactivated form, significantly inhibited angiogenesis both in vitro and in vivo. We have also found that the actin cytoskeleton and the distribution of alphav beta3 integrin, a critical regulator of angiogenesis and a major component of focal adhesions, were disturbed after MVL-PLA2 treatment. In order to further investigate the mechanism of action of this protein on endothelial cells, we analyzed the dynamic instability behavior of microtubules in living endothelial cells. Interestingly, we showed that MVL-PLA2 significantly increased microtubule dynamicity in HMEC-1 cells by 40%. We propose that the enhancement of microtubule dynamics may explain the alterations in the formation of focal adhesions, leading to inhibition of cell adhesion and migration.

  10. adhesive intestinal obstruction

    African Journals Online (AJOL)

    2006-06-01

    Jun 1, 2006 ... ABSTRACT. Background: Adhesions after abdominal and pelvic surgery are a major cause of intestinal obstruction in the western world and the pathology is steadily gaining prominence in our practice. Objective: To determine the magnitude of adhesive intestinal obstruction; to determine the types.

  11. Dynamic strain distribution measurement and crack detection of an adhesive-bonded single-lap joint under cyclic loading using embedded FBG

    International Nuclear Information System (INIS)

    Ning, Xiaoguang; Murayama, Hideaki; Kageyama, Kazuro; Wada, Daichi; Kanai, Makoto; Ohsawa, Isamu; Igawa, Hirotaka

    2014-01-01

    In this study, the dynamic strain distribution measurement of an adhesive-bonded single-lap joint was carried out in a cyclic load test using a fiber Bragg grating (FBG) sensor embedded into the adhesive/adherend interface along the overlap length direction. Unidirectional carbon fiber reinforced plastic (CFRP) substrates were bonded by epoxy resin to form the joint, and the FBG sensor was embedded into the surface of one substrate during its curing. The measurement was carried out with a sampling rate of 5 Hz by the sensing system, based on the optical frequency domain reflectometry (OFDR) throughout the test. A finite element analysis (FEA) was performed for the measurement evaluation using a three-dimensional model, which included the embedded FBG sensor. The crack detection method, based on the longitudinal strain distribution measurement, was introduced and performed to estimate the cracks that occurred at the adhesive/adherend interface in the test. (paper)

  12. Dynamic Response of Metal-Polymer Bilayers - Viscoelasticity, Adhesion and Failure

    Science.gov (United States)

    2013-11-25

    the characteristic high speed radial expansion of the sample (note that the coil is firmly embedded in epoxy and is therefore immobile ). The...the load cell and crosshead displacement sensor of the device. The engineering stress in the specimen was obtained from the load and original cross...dynamic failure behavior of ceramics used as transparent armor (see, for example [3,4, 5]). Glass, laminated with alternating layers of polymers of

  13. Interfacial characteristics and determination of cohesive and adhesive strength of plasma-coated hydroxyapatite via nanoindentation and microscratch techniques.

    Science.gov (United States)

    McManamon, Colm; de Silva, Johann P; Power, John; Ramirez-Garcia, Sonia; Morris, Michael A; Cross, Graham L W

    2014-09-30

    We investigate the chemical composition and mechanical properties of plasma-deposited hydroxyapatite on grit-blasted Ti-6Al-4V coupons as models of typical prosthetic hip implants. Nanoindentation is used to extract the mechanical properties of the hydroxyapatite (HA) coating and to evaluate the behavior of the material as a function of distance from the interface. A microscratch technique was used to determine parameters of cohesive and adhesive failure of the material that are critical in determining the functionality of these biomedical devices. This delamination method has not been studied in detail before and is usually considered to be unsuitable because of the thickness of the HA and the roughness of the substrate. However, through cross-section analysis of the scratch test, we can determine the point at which the HA delaminates from the substrate. It was concluded that spallation occurs locally, and there is no evidence of gross spallation, indicating that the coating is well adhered to the substrate.

  14. Adhesives, fillers & potting compounds: Special report molecular weight determinations of dimethypolysiloxane polymers

    Energy Technology Data Exchange (ETDEWEB)

    Luthey, Z.A.

    1968-09-03

    Using a Mechrolab Vapor Phase Osmometer and a Hallikainen Automatic Membrane Osmometer the number-average molecular weight of two samples of dimethylpolysiloxane - 2300 and 8000 cstk - as well as samples made by mixing the two previously mentioned materials were determined.

  15. Microfilament-coordinated adhesion dynamics drives single cell migration and shapes whole tissues [version 1; referees: 4 approved

    Directory of Open Access Journals (Sweden)

    Rocio Aguilar-Cuenca

    2017-02-01

    Full Text Available Cell adhesion to the substratum and/or other cells is a crucial step of cell migration. While essential in the case of solitary migrating cells (for example, immune cells, it becomes particularly important in collective cell migration, in which cells maintain contact with their neighbors while moving directionally. Adhesive coordination is paramount in physiological contexts (for example, during organogenesis but also in pathology (for example, tumor metastasis. In this review, we address the need for a coordinated regulation of cell-cell and cell-matrix adhesions during collective cell migration. We emphasize the role of the actin cytoskeleton as an intracellular integrator of cadherin- and integrin-based adhesions and the emerging role of mechanics in the maintenance, reinforcement, and turnover of adhesive contacts. Recent advances in understanding the mechanical regulation of several components of cadherin and integrin adhesions allow us to revisit the adhesive clutch hypothesis that controls the degree of adhesive engagement during protrusion. Finally, we provide a brief overview of the major impact of these discoveries when using more physiological three-dimensional models of single and collective cell migration.

  16. Dynamics of Bio-Polymeric Brushes Growing from a Cellular Membrane: Tentative Modelling of the Actin Turnover within an Adhesion Unit; the Podosome.

    Science.gov (United States)

    Biben, Thierry; Géminard, Jean-Christophe; Melo, Francisco

    2005-01-01

    Podosomes are involved in the adhesion process of various cells to a solid substrate. They have been proven to consist of a dense actin core surrounded by an actin cloud. The podosomes, which nucleate when the cell comes in the vicinity of a substrate, contribute to link the membrane to the solid surface, but rather than frozen links, collective dynamical behaviors are experimentally observed. Depending on the differentiation stage, podosomes assemble and form clusters, rings or belts. Considering the dynamics of a polymeric brush, we design a simple model aiming at the description of a single podosome, the basic unit of these complex adhesion-structures and compare our theoretical conclusions to recent experimental results. Particularly, we explain, by solving the diffusion problem around the podosome, why the structure is likely to have a finite life-span.

  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. Assessing the Impact of Germination and Sporulation Conditions on the Adhesion of Bacillus Spores to Glass and Stainless Steel by Fluid Dynamic Gauging.

    Science.gov (United States)

    Xu Zhou, Ke; Li, Nan; Christie, Graham; Wilson, D Ian

    2017-11-01

    The adhesion of spores of 3 Bacillus species with distinctive morphologies to stainless steel and borosilicate glass was studied using the fluid dynamic gauging technique. Marked differences were observed between different species of spores, and also between spores of the same species prepared under different sporulation conditions. Spores of the food-borne pathogen B. cereus were demonstrated to be capable of withstanding shear stresses greater than 1500 Pa when adhered to stainless steel, in contrast to spores of Bacillus subtilis and Bacillus megaterium, which detached in response to lower shear stress. An extended DLVO model was shown to be capable of predicting the relative differences in spore adhesion between spores of different species and different culture conditions, but did not predict absolute values of force of adhesion well. Applying the model to germinating spores showed a significant reduction in adhesion force shortly after triggering germination, indicating a potential strategy to achieve enhanced removal of spores from surfaces in response to shear stress, such as during cleaning-in-place procedures. Spore-forming bacteria are a concern to the food industry because they have the potential to cause food-borne illness and product spoilage, while being strongly adhesive to processing surfaces and resistant to cleaning-in-place procedures. This work is of significance to the food processors and manufacturers because it offers insight to the properties of spore adhesion and identifies a potential strategy to facilitate the removal of spores during cleaning procedures. © 2017 The Authors. Journal of Food Science published by Wiley Periodicals, Inc. on behalf of Institute of Food Technologists.

  19. 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....

  20. Protein adhesives

    Science.gov (United States)

    Charles R. Frihart; Linda F. Lorenz

    2018-01-01

    Nature uses a wide variety of chemicals for providing adhesion internally (e.g., cell to cell) and externally (e.g., mussels to ships and piers). This adhesive bonding is chemically and mechanically complex, involving a variety of proteins, carbohydrates, and other compounds.Consequently,the effect of protein structures on adhesive properties is only partially...

  1. The dynamics of stock price and determination of investor's cash ...

    African Journals Online (AJOL)

    We consider the dynamics of share price, that is, upward and downward movement of share price at time t. We made use of binomial derivative pricing process of stochastic processes. Our aim is to also determine investor's cash flows valuation generated from the investment. The investor invested her short position into N ...

  2. Determining Coastal Mean Dynamic Topography by Geodetic Methods

    Science.gov (United States)

    Huang, Jianliang

    2017-11-01

    In geodesy, coastal mean dynamic topography (MDT) was traditionally determined by spirit leveling technique. Advances in navigation satellite positioning (e.g., GPS) and geoid determination enable space-based leveling with an accuracy of about 3 cm at tide gauges. Recent CryoSat-2, a satellite altimetry mission with synthetic aperture radar (SAR) and SAR interferometric measurements, extends the space-based leveling to the coastal ocean with the same accuracy. However, barriers remain in applying the two space-based geodetic methods for MDT determination over the coastal ocean because current geoid modeling focuses primarily on land as a substitute to spirit leveling to realize the vertical datum.

  3. Light-curing efficiency of dental adhesives by gallium nitride violet-laser diode determined in terms of ultimate micro-tensile strength.

    Science.gov (United States)

    Kameyama, Atsushi; Kato, Junji; De Munck, Jan; Hatayama, Hitoshi; Haruyama, Akiko; Yoshinari, Masao; Takase, Yasuaki; Van Meerbeek, Bart; Tsunoda, Masatake

    2011-01-01

    The purpose of this study was to evaluate whether violet-laser diode (VLD) can be used as light-curing source. The ultimate (micro-)tensile strength (μTS) of three adhesives was determined when cured by VLD in comparison with curing by two different types of commercial LED light-curing units. One VLD (VLM 500) and two LED units (Curenos and G-Light Prima) were used to cure the adhesive resin of the two-step self-etch adhesives Clearfil SE Bond, Tokuso Mac Bond II, and FL-Bond II. A 0.6-mm thick acrylic mould was filled with adhesive resin and cured for 60 s. After 24-h water storage, specimens were trimmed into an hourglass shape with a width of 1.2 mm at the narrowest part, after which the μTS was determined (n=10). In addition, the light transmittance of each adhesive was characterized using a UV-vis-NIR spectrometer. No significant difference in curing efficiency between VLD and LED were observed for both Tokuso Mac Bond II and FL-Bond II (p>0.05). For Clearfil SE Bond, the μTS of VLD-cured specimens was higher than that of the specimens cured by the LED Curenos unit (plight transmittance of Clearfil SE Bond for visible blue light versus for the lower area of UV and visible violet light. In conclusion, A GaN-based violet laser diode can be used as light-curing source to initiate polymerization of dental resins.

  4. Bacillus cereus Adhesion to Simulated Intestinal Mucus Is Determined by Its Growth on Mucin, Rather Than Intestinal Environmental Parameters.

    Science.gov (United States)

    Tsilia, Varvara; Uyttendaele, Mieke; Kerckhof, Frederiek-Maarten; Rajkovic, Andreja; Heyndrickx, Marc; Van de Wiele, Tom

    2015-11-01

    Adhesion of pathogenic bacteria to intestinal mucus, the protective layer of the gastrointestinal epithelium, is often considered a virulence factor. The ability of food-poisoning Bacillus cereus strains to attach to mucus and the factors affecting this interaction have not yet been investigated. Therefore, the role of adhesion in pathogenesis of B. cereus still remains unknown. In the present study, an in vitro assay based on mucin agar was used to simulate adhesion of B. cereus to mucus. Bacterial-associated factors (e.g., strain specificity and microbial competition) known to influence adhesion to different surfaces and a variety of environmental conditions (e.g., pH and oxygen) encountered in the gastrointestinal tract were investigated. The effect of these parameters on B. cereus NVH 0500/00 mucin adhesion was generally limited even in the presence of microbial competition. This suggests that B. cereus NVH 0500/00 is a versatile pathogen. Inoculation of 4 to 5 log colony-forming units (CFU) per milliliter. B. cereus NVH 0500/00 resulted in 5-6 log CFU/mL mucin-associated bacteria after a short incubation period. This indicates that this pathogenic strain could grow in the presence of mucin agar. This growth may potentially mask the effect of the studied conditions. Yet, extensive attachment of B. cereus to mucin is not necessarily a prerequisite for virulence, because other pathogenic strains do not adhere with the same efficiency to mucin. Nevertheless, adhesion may contribute to the disease by providing close contact to nutrient sources, such as mucin, which would not only result in bacterial proliferation, but also in disruption of the protective host mucus surface.

  5. Dynamic pressure sensitivity determination with Mach number method

    Science.gov (United States)

    Sarraf, Christophe; Damion, Jean-Pierre

    2018-05-01

    Measurements of pressure in fast transient conditions are often performed even if the dynamic characteristic of the transducer are not traceable to international standards. Moreover, the question of a primary standard in dynamic pressure is still open, especially for gaseous applications. The question is to improve dynamic standards in order to respond to expressed industrial needs. In this paper, the method proposed in the EMRP IND09 ‘Dynamic’ project, which can be called the ‘ideal shock tube method’, is compared with the ‘collective standard method’ currently used in the Laboratoire de Métrologie Dynamique (LNE/ENSAM). The input is a step of pressure generated by a shock tube. The transducer is a piezoelectric pressure sensor. With the ‘ideal shock tube method’ the sensitivity of a pressure sensor is first determined dynamically. This method requires a shock tube implemented with piezoelectric shock wave detectors. The measurement of the Mach number in the tube allows an evaluation of the incident pressure amplitude of a step using a theoretical 1D model of the shock tube. Heat transfer, other actual effects and effects of the shock tube imperfections are not taken into account. The amplitude of the pressure step is then used to determine the sensitivity in dynamic conditions. The second method uses a frequency bandwidth comparison to determine pressure at frequencies from quasi-static conditions, traceable to static pressure standards, to higher frequencies (up to 10 kHz). The measurand is also a step of pressure generated by a supposed ideal shock tube or a fast-opening device. The results are provided as a transfer function with an uncertainty budget assigned to a frequency range, also deliverable frequency by frequency. The largest uncertainty in the bandwidth of comparison is used to trace the final pressure step level measured in dynamic conditions, owing that this pressure is not measurable in a steady state on a shock tube. A reference

  6. Dynamic Regulation of a Cell Adhesion Protein Complex Including CADM1 by Combinatorial Analysis of FRAP with Exponential Curve-Fitting

    Science.gov (United States)

    Sakurai-Yageta, Mika; Maruyama, Tomoko; Suzuki, Takashi; Ichikawa, Kazuhisa; Murakami, Yoshinori

    2015-01-01

    Protein components of cell adhesion machinery show continuous renewal even in the static state of epithelial cells and participate in the formation and maintenance of normal epithelial architecture and tumor suppression. CADM1 is a tumor suppressor belonging to the immunoglobulin superfamily of cell adhesion molecule and forms a cell adhesion complex with an actin-binding protein, 4.1B, and a scaffold protein, MPP3, in the cytoplasm. Here, we investigate dynamic regulation of the CADM1-4.1B-MPP3 complex in mature cell adhesion by fluorescence recovery after photobleaching (FRAP) analysis. Traditional FRAP analysis were performed for relatively short period of around 10min. Here, thanks to recent advances in the sensitive laser detector systems, we examine FRAP of CADM1 complex for longer period of 60 min and analyze the recovery with exponential curve-fitting to distinguish the fractions with different diffusion constants. This approach reveals that the fluorescence recovery of CADM1 is fitted to a single exponential function with a time constant (τ) of approximately 16 min, whereas 4.1B and MPP3 are fitted to a double exponential function with two τs of approximately 40-60 sec and 16 min. The longer τ is similar to that of CADM1, suggesting that 4.1B and MPP3 have two distinct fractions, one forming a complex with CADM1 and the other present as a free pool. Fluorescence loss in photobleaching analysis supports the presence of a free pool of these proteins near the plasma membrane. Furthermore, double exponential fitting makes it possible to estimate the ratio of 4.1B and MPP3 present as a free pool and as a complex with CADM1 as approximately 3:2 and 3:1, respectively. Our analyses reveal a central role of CADM1 in stabilizing the complex with 4.1B and MPP3 and provide insight in the dynamics of adhesion complex formation. PMID:25780926

  7. Dynamic regulation of a cell adhesion protein complex including CADM1 by combinatorial analysis of FRAP with exponential curve-fitting.

    Science.gov (United States)

    Sakurai-Yageta, Mika; Maruyama, Tomoko; Suzuki, Takashi; Ichikawa, Kazuhisa; Murakami, Yoshinori

    2015-01-01

    Protein components of cell adhesion machinery show continuous renewal even in the static state of epithelial cells and participate in the formation and maintenance of normal epithelial architecture and tumor suppression. CADM1 is a tumor suppressor belonging to the immunoglobulin superfamily of cell adhesion molecule and forms a cell adhesion complex with an actin-binding protein, 4.1B, and a scaffold protein, MPP3, in the cytoplasm. Here, we investigate dynamic regulation of the CADM1-4.1B-MPP3 complex in mature cell adhesion by fluorescence recovery after photobleaching (FRAP) analysis. Traditional FRAP analysis were performed for relatively short period of around 10 min. Here, thanks to recent advances in the sensitive laser detector systems, we examine FRAP of CADM1 complex for longer period of 60 min and analyze the recovery with exponential curve-fitting to distinguish the fractions with different diffusion constants. This approach reveals that the fluorescence recovery of CADM1 is fitted to a single exponential function with a time constant (τ) of approximately 16 min, whereas 4.1B and MPP3 are fitted to a double exponential function with two τs of approximately 40-60 sec and 16 min. The longer τ is similar to that of CADM1, suggesting that 4.1B and MPP3 have two distinct fractions, one forming a complex with CADM1 and the other present as a free pool. Fluorescence loss in photobleaching analysis supports the presence of a free pool of these proteins near the plasma membrane. Furthermore, double exponential fitting makes it possible to estimate the ratio of 4.1B and MPP3 present as a free pool and as a complex with CADM1 as approximately 3:2 and 3:1, respectively. Our analyses reveal a central role of CADM1 in stabilizing the complex with 4.1B and MPP3 and provide insight in the dynamics of adhesion complex formation.

  8. Real-time monitoring of mechanical changes during dynamic adhesion of erythrocytes to endothelial cells by QCM-D.

    Science.gov (United States)

    Zhang, Shaolian; Bai, Haihua; Yang, Peihui

    2015-07-21

    A quartz crystal microbalance with dissipation monitoring is used to measure changes in mechanical properties of diabetic red blood cells (RBCs) and normal RBCs. Moreover, the adhesion interaction between these two kinds of RBCs and endothelial cells (ECs) is further investigated using a proposed QCM-D biosensor for the first time.

  9. Cellular Adhesion and Adhesion Molecules

    OpenAIRE

    SELLER, Zerrin

    2014-01-01

    In recent years, cell adhesion and cell adhesion molecules have been shown to be important for many normal biological processes, including embryonic cell migration, immune system functions and wound healing. It has also been shown that they contribute to the pathogenesis of a large number of common human disorders, such as rheumatoid arthritis and tumor cell metastasis in cancer. In this review, the basic mechanisms of cellular adhesion and the structural and functional features of adhes...

  10. Bacterial adhesion

    NARCIS (Netherlands)

    Loosdrecht, van M.C.M.

    1988-01-01

    As mentioned in the introduction of this thesis bacterial adhesion has been studied from a variety of (mostly practice oriented) starting points. This has resulted in a range of widely divergent approaches. In order to elucidate general principles in bacterial adhesion phenomena, we felt it

  11. 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...

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

    Science.gov (United States)

    Cady, Carl M.; Liu, Cheng; Lovato, Manuel L.

    2015-09-01

    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.

  13. 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.

  14. Plasticizers increase adhesion of the deteriogenic fungus Aureobasidium pullulans to polyvinyl chloride.

    Science.gov (United States)

    Webb, J S; Van der Mei, H C; Nixon, M; Eastwood, I M; Greenhalgh, M; Read, S J; Robson, G D; Handley, P S

    1999-08-01

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

  15. Denture Adhesives

    Science.gov (United States)

    ... prevent overuse if zinc is an ingredient. (Some companies include graphics of the amount of adhesive to ... and adequate directions for use or a clear definition of an unsafe dosage or methods or duration ...

  16. Viscosity of aqueous DNA solutions determined using dynamic light scattering.

    Science.gov (United States)

    Gilroy, Emma L; Hicks, Matthew R; Smith, David J; Rodger, Alison

    2011-10-21

    Viscosity is a key parameter for characterising the behaviour of liquids and their flow. It is, however, difficult to measure precisely, reproducibly and accurately for aqueous solutions on a micro-litre volume scale, which is what is usually needed for biological samples. We report the development of a new method for measuring dynamic viscosity by measuring dynamic light scattering (DLS) data for a range of particles of well-defined size. Most applications of DLS involve determining particle size for samples of known viscosity. We inverted the usual protocol and endeavoured to determine viscosity for samples of known particle size. Viscosity measurements for water and aqueous solutions of calf thymus DNA made using DLS were compared with those from a U-tube viscometer. The styrene particles, frequently used as particle size standards, gave unsatisfactory results for our DNA samples as did C-6 derivatized silica and positively charged amino polystyrene microspheres. However, negatively charged carboxylate polystyrene microspheres particles readily gave accurate viscosity measurements over a range of temperatures (0-100 °C). The sample volume required depends on the cuvette used to measure DLS, but can be performed with samples sizes ranging from 40 to 3000 μL. The sample can then be recovered for subsequent experiments. The DLS method is simple to perform at different temperatures and provides data of accuracy significantly above that of a U-tube viscometer. Our results also indicate a way forward to account accurately for solution viscosity in the normal applications of DLS to particle size determination by including the appropriate non-interacting particles as an internal standard.

  17. TRIM15 is a focal adhesion protein that regulates focal adhesion disassembly

    Science.gov (United States)

    Uchil, Pradeep D.; Pawliczek, Tobias; Reynolds, Tracy D.; Ding, Siyuan; Hinz, Angelika; Munro, James B.; Huang, Fang; Floyd, Robert W.; Yang, Haitao; Hamilton, William L.; Bewersdorf, Joerg; Xiong, Yong; Calderwood, David A.; Mothes, Walther

    2014-01-01

    ABSTRACT Focal adhesions are macromolecular complexes that connect the actin cytoskeleton to the extracellular matrix. Dynamic turnover of focal adhesions is crucial for cell migration. Paxillin is a multi-adaptor protein that plays an important role in regulating focal adhesion dynamics. Here, we identify TRIM15, a member of the tripartite motif protein family, as a paxillin-interacting factor and a component of focal adhesions. TRIM15 localizes to focal contacts in a myosin-II-independent manner by an interaction between its coiled-coil domain and the LD2 motif of paxillin. Unlike other focal adhesion proteins, TRIM15 is a stable focal adhesion component with restricted mobility due to its ability to form oligomers. TRIM15-depleted cells display impaired cell migration and reduced focal adhesion disassembly rates, in addition to enlarged focal adhesions. Thus, our studies demonstrate a cellular function for TRIM15 as a regulatory component of focal adhesion turnover and cell migration. PMID:25015296

  18. 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.

    2015-01-01

    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 km2 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 develop

  19. A dynamic econometric model of agricultural wage determination in Bangladesh.

    Science.gov (United States)

    Boyce, J K; Ravallion, M

    1991-11-01

    Economists applied data from 1949-1950 and 1980-1981 to a new dynamic model to examine the dynamics of determinants of agricultural wages in Bangladesh, particularly the effect of changes in relative prices of rice (the staple food) and productivity. Just a 20% rise in the price or rice was passed on in the agricultural wage rate within the current year. About 50% was passed on in the long run, however. Therefore an increase in the price of rice reduced the rice purchasing power of agricultural wages in the short and long term. In fact, the importance given to rice in the long run real wage rate was almost the same as the mean proportion of expenditure that an agricultural laborer in Bangladesh committed to rice and closely related food staples. Thus arise in the price of rice in comparison to other goods had limited effects on the long run real wage in terms of the bundle of goods typically consumed, but very adverse effects in the short run placing a high burden on the rural poor. On the other hand, the long run real wage rate fell considerably between the mid 1960s-early 1980s when overall agricultural productivity increased. The economists pointed out that this increased productivity may not have lowered long run real wage rates, but instead mitigating factors may have contributed to this fall. For example, population growth, rising landlessness, and insufficient economic growth in nonagricultural sectors resulted in a consistent growth in the labor supply. In conclusion, this new dynamic model showed that Bangladesh cannot depend only on agricultural growth to reduce the poverty of farmers.

  20. 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

  1. Dynamic and reduced-dynamic precise orbit determination of satellites in low earth orbits

    International Nuclear Information System (INIS)

    Swatschina, P.

    2009-01-01

    The precise positioning of satellites in Low Earth Orbits (LEO) has become a key technology for advanced space missions. Dedicated satellite missions, such as CHAMP, GRACE and GOCE, that aim to map the Earths gravity field and its variation over time with unprecedented accuracy, initiated the demand for highly precise orbit solutions of LEO satellites. Furthermore, a wide range of additional science opportunities opens up with the capability to generate accurate LEO orbits. For all considered satellite missions, the primary measurement system for navigation is a spaceborne GPS receiver. The goal of this thesis is to establish and implement methods for Precise Orbit Determination (POD) of LEO satellites using GPS. Striving for highest precision using yet efficient orbit generation strategies, the attained orbit solutions are aimed to be competitive with the most advanced solutions of other institutions. Dynamic and reduced-dynamic orbit models provide the basic concepts of this work. These orbit models are subsequently adjusted to the highly accurate GPS measurements. The GPS measurements are introduced at the zero difference level in the ionosphere free linear combination. Appropriate procedures for GPS data screening and editing are established to detect erroneous data and to employ measurements of good quality only. For the dynamic orbit model a sophisticated force model, especially designed for LEO satellites, has been developed. In order to overcome the limitations that are induced by the deficiencies of the purely dynamical model, two different types of empirical parameters are introduced into the force model. These reduced-dynamic orbit models allow for the generation of much longer orbital arcs while preserving the spacecraft dynamics to the most possible extent. The two methods for reduced-dynamic orbit modeling are instantaneous velocity changes (pulses) or piecewise constant accelerations. For both techniques highly efficient modeling algorithms are

  2. PI(3,4)P2plays critical roles in the regulation of focal adhesion dynamics of MDA-MB-231 breast cancer cells.

    Science.gov (United States)

    Fukumoto, Miki; Ijuin, Takeshi; Takenawa, Tadaomi

    2017-05-01

    Phosphoinositides play pivotal roles in the regulation of cancer cell phenotypes. Among them, phosphatidylinositol 3,4-bisphosphate (PI(3,4)P 2 ) localizes to the invadopodia, and positively regulates tumor cell invasion. In this study, we examined the effect of PI(3,4)P 2 on focal adhesion dynamics in MDA-MB-231 basal breast cancer cells. Knockdown of SHIP2, a phosphatidylinositol 3,4,5-trisphosphatase (PIP 3 ) 5-phosphatase that generates PI(3,4)P 2 , in MDA-MB-231 breast cancer cells, induced the development of focal adhesions and cell spreading, leading to the suppression of invasion. In contrast, knockdown of PTEN, a 3-phosphatase that de-phosphorylates PIP 3 and PI(3,4)P 2 , induced cell shrinkage and increased cell invasion. Interestingly, additional knockdown of SHIP2 rescued these phenotypes. Overexpression of the TAPP1 PH domain, which binds to PI(3,4)P 2 , and knockdown of Lpd, a downstream effector of PI(3,4)P 2 , resulted in similar phenotypes to those induced by SHIP2 knockdown. Taken together, our results suggest that inhibition of PI(3,4)P 2 generation and/or downstream signaling could be useful for inhibiting breast cancer metastasis. © 2017 The Authors. Cancer Science published by John Wiley & Sons Australia, Ltd on behalf of Japanese Cancer Association.

  3. 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.

  4. Measurement of thick film adhesion by an impact separation technique

    International Nuclear Information System (INIS)

    Snowden, W.E.; Aksay, I.A.

    1981-01-01

    The purpose of this study was to utilize a dynamic loading (impact separation) technique to determine absolute values for the force of adhesion required to separate a substrate/film interface into its two joining components. A principal advantage of the technique is that the force required for adhesive failure is applied directly at the interface by stress waves of relatively low amplitude, not by application of a force to the free surface of the film. Critical impact velocities required for separation of thick films from two types of substrates were measured. Values for force of adhesion were then calculated using a complex finite-difference computer code developed for analysis of a variety of dynamic problems

  5. 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...

  6. 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

  7. Passively stuck: death does not affect gecko adhesion strength.

    Science.gov (United States)

    Stewart, William J; Higham, Timothy E

    2014-12-01

    Many geckos use adhesive toe pads on the bottom of their digits to attach to surfaces with remarkable strength. Although gecko adhesion has been studied for hundreds of years, gaps exist in our understanding at the whole-animal level. It remains unclear whether the strength and maintenance of adhesion are determined by the animal or are passively intrinsic to the system. Here we show, for the first time, that strong adhesion is produced passively at the whole-animal level. Experiments on both live and recently euthanized tokay geckos (Gekko gecko) revealed that death does not affect the dynamic adhesive force or motion of a gecko foot when pulled along a vertical surface. Using a novel device that applied repeatable and steady-increasing pulling forces to the foot in shear, we found that the adhesive force was similarly high and variable when the animal was alive (mean ± s.d. = 5.4 ± 1.7 N) and within 30 min after death (5.4 ± 2.1 N). However, kinematic analyses showed that live geckos are able to control the degree of toe pad engagement and can rapidly stop strong adhesion by hyperextending the toes. This study offers the first assessment of whole-animal adhesive force under extremely controlled conditions. Our findings reveal that dead geckos maintain the ability to adhere with the same force as living animals, disproving that strong adhesion requires active control. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  8. 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...

  9. Controlling adhesive behavior during recycling

    Science.gov (United States)

    Carl Houtman; Karen Scallon; Jihui Guo; XinPing Wang; Steve Severtson; Mark Kroll; Mike Nowak

    2004-01-01

    Adhesives can be formulated to facilitate their removal by typical paper recycling unit operations. The investigations described in this paper are focused on determining fundamental properties that control particle size during pulping. While pressure-sensitive adhesives (PSAs) with high elastic moduli tend to survive pulping with larger particles, facestock and...

  10. Adhesion molecules

    CERN Document Server

    Preedy, Victor R

    2016-01-01

    This book covers the structure and classification of adhesion molecules in relation to signaling pathways and gene expression. It discusses immunohistochemical localization, neutrophil migration, and junctional, functional, and inflammatory adhesion molecules in pathologies such as leukocyte decompression sickness and ischemia reperfusion injury. Highlighting the medical applications of current research, chapters cover diabetes, obesity, and metabolic syndrome; hypoxia; kidney disease; smoking, atrial fibrillation, and heart disease, the brain and dementia; and tumor proliferation. Finally, it looks at molecular imaging and bioinformatics, high-throughput technologies, and chemotherapy.

  11. 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.

  12. Bacterial Adhesion & Blocking Bacterial Adhesion

    DEFF Research Database (Denmark)

    Vejborg, Rebecca Munk

    2008-01-01

    reduce or delay bacterial biofilm formation of a range of urinary tract infectious E.coli and Klebsiella isolates. Several other proteinaceous coatings were also found to display anti-adhesive properties, possibly providing a measure for controlling the colonization of implant materials. Several other...... components. These substances may both mediate and stabilize the bacterial biofilm. Finally, several adhesive structures were examined, and a novel physiological biofilm phenotype in E.coli biofilms was characterized, namely cell chain formation. The autotransporter protein, antigen 43, was implicated...

  13. Adhesive plasters

    Science.gov (United States)

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

    1978-01-01

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

  14. Determination of Dynamic Fracture Toughness Properties of Rail Steels

    Science.gov (United States)

    1987-11-01

    Motivated by the occurrence of a long-running rail web fracture in service, dynamic fracture mechanics research was undertaken to (1) quantify the crack driving force due to the residual stresses induced by roller straightening operations, (2) determ...

  15. Foreign material in postoperative adhesions

    NARCIS (Netherlands)

    R.W. Luijendijk; D.C.D. de Lange (Diederik); C.C. Wauters; W.C.J. Hop (Wim); J.J. Duron; J.L. Pailler; B.R. Camprodon; L. Holmdahl; H.J. van Geldorp; J. Jeekel (Hans)

    1996-01-01

    textabstractOBJECTIVE: The authors determined the prevalence of foreign body granulomas in intra-abdominal adhesions in patients with a history of abdominal surgery. PATIENTS AND METHODS: In a cross-sectional, multicenter, multinational study, adult patients with a

  16. Adhesive capsulitis of the shoulder.

    Science.gov (United States)

    Neviaser, Andrew S; Neviaser, Robert J

    2011-09-01

    Adhesive capsulitis is characterized by painful, gradual loss of active and passive shoulder motion resulting from fibrosis and contracture of the joint capsule. Other shoulder pathology can produce a similar clinical picture, however, and must be considered. Management is based on the underlying cause of pain and stiffness, and determination of the etiology is essential. Subtle clues in the history and physical examination can help differentiate adhesive capsulitis from other conditions that cause a stiff, painful shoulder. The natural history of adhesive capsulitis is a matter of controversy. Management of true capsular restriction of motion (ie, true adhesive capsulitis) begins with gentle, progressive stretching exercises. Most patients improve with nonsurgical treatment. Indications for surgery should be individualized. Failure to obtain symptomatic improvement and continued functional disability following ≥6 months of physical therapy is a general guideline for surgical intervention. Diligent postoperative therapy to maintain motion is required to minimize recurrence of adhesive capsulitis.

  17. Determining Equilibrium Constants for Dimerization Reactions from Molecular Dynamics Simulations

    NARCIS (Netherlands)

    De Jong, Djurre H.; Schafer, Lars V.; De Vries, Alex H.; Marrink, Siewert J.; Berendsen, Herman J. C.; Grubmueller, Helmut

    2011-01-01

    With today's available computer power, free energy calculations from equilibrium molecular dynamics simulations "via counting" become feasible for an increasing number of reactions. An example is the dimerization reaction of transmembrane alpha-helices. If an extended simulation of the two helices

  18. 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.

  19. Features of determining the parameters of dynamic shapes and gravitational fields of planetary satellites

    Science.gov (United States)

    Yasenev, S. O.

    2016-12-01

    The problem of determining the dynamic shapes of planetary satellites becomes important today. The goal of this paper is to analyze the physical properties of satellites which are referred to planetoids. An analysis of planetary satellites as self-gravitating structures is performed, and parameters of their dynamic shapes are determined.

  20. Emergent dynamics of thymocyte development and lineage determination.

    Directory of Open Access Journals (Sweden)

    Sol Efroni

    2007-01-01

    Full Text Available Experiments have generated a plethora of data about the genes, molecules, and cells involved in thymocyte development. Here, we use a computer-driven simulation that uses data about thymocyte development to generate an integrated dynamic representation-a novel technology we have termed reactive animation (RA. RA reveals emergent properties in complex dynamic biological systems. We apply RA to thymocyte development by reproducing and extending the effects of known gene knockouts: CXCR4 and CCR9. RA simulation revealed a previously unidentified role of thymocyte competition for major histocompatability complex presentation. We now report that such competition is required for normal anatomical compartmentalization, can influence the rate of thymocyte velocities within chemokine gradients, and can account for the disproportion between single-positive CD4 and CD8 lineages developing from double-positive precursors.

  1. Determination of dynamic Young’s modulus of vulnerable speleothems

    Czech Academy of Sciences Publication Activity Database

    Konečný, Pavel; Lednická, Markéta; Souček, Kamil; Staš, Lubomír; Kubina, Lukáš; Gribovszki, K.

    2015-01-01

    Roč. 20, č. 2 (2015), s. 156-163 ISSN 1335-1788 R&D Projects: GA MŠk ED2.1.00/03.0082; GA MŠk(CZ) LO1406 Institutional support: RVO:68145535 Keywords : dynamic Young´s modulus * speleothem * bulk density * X-Ray Computed Tomography Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.390, year: 2015 http://actamont.tuke.sk/pdf/2015/n2/10Konecny.pdf

  2. 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

  3. Molecular determinants and dynamics of hepatitis C virus secretion.

    Directory of Open Access Journals (Sweden)

    Kelly E Coller

    2012-01-01

    Full Text Available The current model of hepatitis C virus (HCV production involves the assembly of virions on or near the surface of lipid droplets, envelopment at the ER in association with components of VLDL synthesis, and egress via the secretory pathway. However, the cellular requirements for and a mechanistic understanding of HCV secretion are incomplete at best. We combined an RNA interference (RNAi analysis of host factors for infectious HCV secretion with the development of live cell imaging of HCV core trafficking to gain a detailed understanding of HCV egress. RNAi studies identified multiple components of the secretory pathway, including ER to Golgi trafficking, lipid and protein kinases that regulate budding from the trans-Golgi network (TGN, VAMP1 vesicles and adaptor proteins, and the recycling endosome. Our results support a model wherein HCV is infectious upon envelopment at the ER and exits the cell via the secretory pathway. We next constructed infectious HCV with a tetracysteine (TC tag insertion in core (TC-core to monitor the dynamics of HCV core trafficking in association with its cellular cofactors. In order to isolate core protein movements associated with infectious HCV secretion, only trafficking events that required the essential HCV assembly factor NS2 were quantified. TC-core traffics to the cell periphery along microtubules and this movement can be inhibited by nocodazole. Sub-populations of TC-core localize to the Golgi and co-traffic with components of the recycling endosome. Silencing of the recycling endosome component Rab11a results in the accumulation of HCV core at the Golgi. The majority of dynamic core traffics in association with apolipoprotein E (ApoE and VAMP1 vesicles. This study identifies many new host cofactors of HCV egress, while presenting dynamic studies of HCV core trafficking in infected cells.

  4. Determination of molecular species of calcium salts of MDP produced through decalcification of enamel and dentin by MDP-based one-step adhesive.

    Science.gov (United States)

    Yokota, Yoko; Nishiyama, Norihiro

    2015-01-01

    Enamel and dentin particles were added to an experimental 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-based one-step adhesive to react for 30 s. After enamel and dentin reactants were analyzed using X-ray diffraction (XRD) and phosphorus-31 nuclear magnetic resonance ((31)P NMR) techniques, curve-fitting analysis was performed on the (31)P NMR spectra of enamel and dentin reactants. By varying the molar ratio of calcium chloride to MDP, a series of three types of MDP-Ca salts were synthesized. The molecular species of calcium salts of MDP (MDP-Ca salts) produced by decalcification of enamel or dentin were determined based on the XRD and (31)P NMR analysis results of these three types of synthesized MDP-Ca salts. Curve-fitting analysis showed that enamel and dentin developed several types of MDP-Ca salts and amorphous dicalcium phosphate dihydrate (DCPD) during decalcification. The molecular species of MDP-Ca salts produced by enamel and dentin were mono-calcium salts of MDP monomer and MDP dimer. In addition, dentin produced a di-calcium of MDP dimer.

  5. 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.

  6. 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.

  7. Effect on adhesion of a nanocapsules-loaded adhesive system

    Directory of Open Access Journals (Sweden)

    Bruna Genari

    2018-02-01

    Full Text Available Abstract This study aimed to evaluate the in situ degree of conversion, contact angle, and immediate and long-term bond strengths of a commercial primer and an experimental adhesive containing indomethacin- and triclosan-loaded nanocapsules (NCs. The indomethacin- and triclosan-loaded NCs, which promote anti-inflammatory and antibacterial effects through controlled release, were incorporated into the primer at a concentration of 2% and in the adhesive at concentrations of 1, 2, 5, and 10%. The in situ degree of conversion (DC, n=3 was evaluated by micro-Raman spectroscopy. The contact angle of the primer and adhesive on the dentin surface (n = 3 was determined by an optical tensiometer. For the microtensile bond strength µTBS test (12 teeth per group, stick-shaped specimens were tested under tensile stress immediately after preparation and after storage in water for 1 year. The data were analyzed using two-way ANOVA, three-way ANOVA and Tukey’s post hoc tests with α=0.05. The use of the NC-loaded adhesive resulted in a higher in situ degree of conversion. The DC values varied from 75.07 ± 8.83% to 96.18 ± 0.87%. The use of NCs in only the adhesive up to a concentration of 5% had no influence on the bond strength. The contact angle of the primer remained the same with and without NCs. The use of both the primer and adhesive with NCs (for all concentrations resulted in a higher contact angle of the adhesive. The longitudinal μTBS was inversely proportional to the concentration of NCs in the adhesive system, exhibiting decreasing values for the groups with primer containing NCs and adhesives with increasing concentrations of NCs. Adhesives containing up to 5% of nanocapsules and primer with no NCs maintained the in situ degree of conversion, contact angle, and immediate and long-term bond strengths. Therefore, the NC-loaded adhesive can be an alternative method for combining the bond performance and therapeutic effects. The use of an

  8. Farm Target Capital Structure: Dynamics, Determinants and Speed of Adjustment

    NARCIS (Netherlands)

    Tamirat, A.S.; Trujillo Barrera, A.A.; Pennings, J.M.E.

    2017-01-01

    The corporate finance literature has focused on explaining the determinants of firms target capital structure and speed of adjustment using the well-established theories such as pecking order, signaling and trade-off theories. However, less attention has been paid to understanding the financing

  9. 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 ...

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

    Directory of Open Access Journals (Sweden)

    Nicolas Lebesgue

    2016-06-01

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

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

    Science.gov (United States)

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

    2016-06-01

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

  12. Experimental determination of dynamic parameters of an industrial robot

    Science.gov (United States)

    Banas, W.; Cwikła, G.; Foit, K.; Gwiazda, A.; Monica, Z.; Sekala, A.

    2017-08-01

    In an industry increasingly used are industrial robots. Commonly used are two basic methods of programming, on-line programming and off-line programming. In both cases, the programming consists in getting to the selected points record this position, and set the order of movement of the robot, and the introduction of logical tests. Such a program is easy to write, and it is suitable for most industrial applications. Especially when the process is known, respectively slow and unchanging. In this case, the program is being prepared for a universal model of the robot with the appropriate geometry and are checked only collisions. Is not taken into account the dynamics of the robot and how it will really behave while in motion. For this reason, the robot programmed to be tested at a reduced speed, which is raised gradually to the final value. Depending on the complexity of the move and the proximity of the elements it takes a lot of time. It is easy to notice that the robot at different speeds have different trajectories and behaves differently.

  13. Dynamic determination of equivalent CT source models for personalized dosimetry

    Directory of Open Access Journals (Sweden)

    Rosendahl Stephan

    2017-09-01

    Full Text Available With improvements in CT technology, the need for reliable patient-specific dosimetry increased in the recent years. The accuracy of Monte-Carlo simulations for absolute dose estimation is related to scanner specific information on the X-ray spectra of the scanner as well as the form filter geometries and compositions. In this work a mobile measurement setup is developed, which allows both to determine the X-ray spectra and equivalent form filter of a specific scanner from just one helical scan in less than 2 minutes.

  14. From space and from the ground: determining forest dynamics in settlement projects in the Brazilian Amazon

    NARCIS (Netherlands)

    Diniz, F.H.; Kok, K.; Hott, H.C.; Hoogstra-Klein, M.A.; Arts, B.J.M.

    2013-01-01

    Deforestation in the Brazilian Amazon has been partially attributed to the establishment of settlement projects. Acknowledging the difficulties in quantifying the rate and patterns of deforestation, the objective of this paper is to determine forest dynamics (deforestation and reforestation) in

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

    Science.gov (United States)

    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 there are large increases of [Ca2+]i, time- and Ca2+-dependent enrichment of NMMIIA and gelsolin at collagen adhesions, and abundant intracellular collagen degradation. NMMIIA knockdown retards gelsolin recruitment to adhesions and blocks collagen phagocytosis. Gelsolin exhibits tight, Ca2+-dependent binding to full-length NMMIIA. Gelsolin domains G4–G6 selectively require Ca2+ to interact with NMMIIA, which is restricted to residues 1339–1899 of NMMIIA. We conclude that cell adhesion to collagen presented on beads activates Ca2+ entry and promotes the formation of phagosomes enriched with NMMIIA and gelsolin. The Ca2+ -dependent interaction of gelsolin and NMMIIA in turn enables actin remodeling and enhances collagen degradation by phagocytosis. PMID:23325791

  16. Determination of static and dynamic reactivity effects in KNK II

    International Nuclear Information System (INIS)

    Essig, C.

    1987-11-01

    In the frame of a pre-study of the KNK II test program two series of experiments related to inherent safety characteristics of sodium cooled breeder reactors have been elaborated, which are one basis for the performance of experiments of the Loss Of Flow (LOF) type and the Loss Of Heat Sink (LOHS) type. Tests of this type at KNK II would -different from the earlier tests at RAPSODIE and EBR-II- provide a demonstration of the inherently safe performance in case of a significantly non-zero Doppler effect. With a suitable execution, the foreseen series of experiments allow, as explained in this report, a substantial separation of the reactivity contributions and the determination of reactivity effects, i.e. the time constants of the recouplings. The performance and evaluation of these experiments with respect to the inherent safety potential will once more underline the distinguished role of KNK II for the development of fast breeders [de

  17. 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

  18. Kv2 Ion Channels Determine the Expression and Localization of the Associated AMIGO-1 Cell Adhesion Molecule in Adult Brain Neurons

    Directory of Open Access Journals (Sweden)

    Hannah I. Bishop

    2018-01-01

    Full Text Available Voltage-gated K+ (Kv channels play important roles in regulating neuronal excitability. Kv channels comprise four principal α subunits, and transmembrane and/or cytoplasmic auxiliary subunits that modify diverse aspects of channel function. AMIGO-1, which mediates homophilic cell adhesion underlying neurite outgrowth and fasciculation during development, has recently been shown to be an auxiliary subunit of adult brain Kv2.1-containing Kv channels. We show that AMIGO-1 is extensively colocalized with both Kv2.1 and its paralog Kv2.2 in brain neurons across diverse mammals, and that in adult brain, there is no apparent population of AMIGO-1 outside of that colocalized with these Kv2 α subunits. AMIGO-1 is coclustered with Kv2 α subunits at specific plasma membrane (PM sites associated with hypolemmal subsurface cisternae at neuronal ER:PM junctions. This distinct PM clustering of AMIGO-1 is not observed in brain neurons of mice lacking Kv2 α subunit expression. Moreover, in heterologous cells, coexpression of either Kv2.1 or Kv2.2 is sufficient to drive clustering of the otherwise uniformly expressed AMIGO-1. Kv2 α subunit coexpression also increases biosynthetic intracellular trafficking and PM expression of AMIGO-1 in heterologous cells, and analyses of Kv2.1 and Kv2.2 knockout mice show selective loss of AMIGO-1 expression and localization in neurons lacking the respective Kv2 α subunit. Together, these data suggest that in mammalian brain neurons, AMIGO-1 is exclusively associated with Kv2 α subunits, and that Kv2 α subunits are obligatory in determining the correct pattern of AMIGO-1 expression, PM trafficking and clustering.

  19. In situ structure and dynamics of DNA origami determined through molecular dynamics simulations.

    Science.gov (United States)

    Yoo, Jejoong; Aksimentiev, Aleksei

    2013-12-10

    The DNA origami method permits folding of long single-stranded DNA into complex 3D structures with subnanometer precision. Transmission electron microscopy, atomic force microscopy, and recently cryo-EM tomography have been used to characterize the properties of such DNA origami objects, however their microscopic structures and dynamics have remained unknown. Here, we report the results of all-atom molecular dynamics simulations that characterized the structural and mechanical properties of DNA origami objects in unprecedented microscopic detail. When simulated in an aqueous environment, the structures of DNA origami objects depart from their idealized targets as a result of steric, electrostatic, and solvent-mediated forces. Whereas the global structural features of such relaxed conformations conform to the target designs, local deformations are abundant and vary in magnitude along the structures. In contrast to their free-solution conformation, the Holliday junctions in the DNA origami structures adopt a left-handed antiparallel conformation. We find the DNA origami structures undergo considerable temporal fluctuations on both local and global scales. Analysis of such structural fluctuations reveals the local mechanical properties of the DNA origami objects. The lattice type of the structures considerably affects global mechanical properties such as bending rigidity. Our study demonstrates the potential of all-atom molecular dynamics simulations to play a considerable role in future development of the DNA origami field by providing accurate, quantitative assessment of local and global structural and mechanical properties of DNA origami objects.

  20. Accuracy of preoperative real-time dynamic transvaginal ultrasound sliding sign in prediction of pelvic adhesions in women with previous abdominopelvic surgery: prospective, multicenter, double-blind study.

    Science.gov (United States)

    Ayachi, A; Bouchahda, R; Derouich, S; Mkaouer, L; Kehila, M; Abouda, H; Channoufi, B; Bouyahia, M; Braham, M; Zhioua, F; Bouchahda, H; Mourali, M

    2018-02-01

    To investigate the role of the transvaginal sonographic (TVS) sliding sign in predicting pelvic adhesions in women with previous abdominopelvic surgery. This was a multicenter, prospective, interventional, double-blind study of patients with a history of abdominopelvic surgery who were undergoing laparoscopy or laparotomy during the 6-month period from March to August 2016 in one of three academic obstetrics and gynecology departments. Prior to surgery, patients were examined by TVS to assess the vesicouterine pouch, uterus, ovaries and pouch of Douglas, using the TVS pelvic sliding sign. Ultrasound findings and medical and surgical data were recorded. We assessed the accuracy of the preoperative TVS sliding sign in the prediction of pelvic adhesions overall and in each compartment separately. During the study period, complete TVS sliding sign and laparoscopic or laparotomic data were available for 107 women. Their mean age was 44.0 (95% CI, 41.6-46.4; range, 20-79) years. Their mean parity was 2.0 (95% CI, 1.7-2.3; range, 0-9) and the mean number of previous abdominal surgical procedures per patient was 1.3 (95% CI, 1.2-1.5; range, 1-4). Adhesions were noted in 27/107 (25.2%) patients. The TVS sliding sign had a sensitivity of 96.3% and specificity of 92.6% in predicting pelvic adhesions. There was a significant relationship between adhesions in each compartment and the TVS sliding sign (P sign is an effective means to detect preoperatively pelvic adhesions in patients with previous abdominopelvic surgery. Use of such a non-invasive and well-tolerated technique could help in the planning of laparoscopy or laparotomy and counseling of these patients. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

  1. Determination of Dynamical Heterogeneity from Dynamic Neutron-Scattering of Proteins.

    Science.gov (United States)

    Vural, Derya; Smith, Jeremy C; Glyde, Henry R

    2018-03-23

    Motional displacements of hydrogen (H) in proteins can be measured using incoherent neutron-scattering methods. These displacements can also be calculated numerically using data from molecular dynamics simulations. An enormous amount of data on the average mean-square motional displacement (MSD) of H as a function of protein temperature, hydration, and other conditions has been collected. H resides in a wide spectrum of sites in a protein. Some H are tightly bound to molecular chains, and the H motion is dictated by that of the chain. Other H are quite independent. As a result, there is a distribution of motions and MSDs of H within a protein that is denoted dynamical heterogeneity. The goal of this paper is to incorporate a distribution of MSDs into models of the H incoherent intermediate scattering function, I(Q,t), that is calculated and observed. The aim is to contribute information on the distribution as well as on the average MSD from comparison of the models with simulations and experiment. For example, we find that simulations of I(Q,t) in lysozyme are well reproduced if the distribution of MSDs is bimodal with two broad peaks rather than a single broad peak. Copyright © 2018 Biophysical Society. All rights reserved.

  2. Determination of the shear and bulk viscosity from equilibrium molecular-dynamics simulations

    Science.gov (United States)

    Jaeger, Frederike; Muller, Erich; Matar, Omar K.

    2017-11-01

    Determining fluid properties accurately is essential for large-scale fluid dynamics simulations where only a few parameters determine the behaviour of an entire system. Even though many properties are well known, others are more obscure and difficult to determine experimentally. One such property is the bulk viscosity which plays a particularly large role in compressible fluids but is rarely considered in fluid-dynamics simulations. We determine both the shear and bulk viscosity using equilibrium methods within the molecular-dynamics framework using both atomistic and coarse-grained models with a view of assessing both the accuracy of coarse-grained models for transport-property calculations and the necessity of including such properties at various scales and scenarios. Funding from the Theory and Simulation of Materials, EPSRC (UK) Centre for Doctoral Training is gratefully acknowledged.

  3. Small Heat Shock Protein αB-Crystallin Controls Shape and Adhesion of Glioma and Myoblast Cells in the Absence of Stress.

    Directory of Open Access Journals (Sweden)

    Miho Shimizu

    Full Text Available Cell shape and adhesion and their proper controls are fundamental for all biological systems. Mesenchymal cells migrate at an average rate of 6 to 60 μm/hr, depending on the extracellular matrix environment and cell signaling. Myotubes, fully differentiated muscle cells, are specialized for power-generation and therefore lose motility. Cell spreading and stabilities of focal adhesion are regulated by the critical protein vinculin from immature myoblast to mature costamere of differentiated myotubes where myofibril Z-band linked to sarcolemma. The Z-band is constituted from microtubules, intermediate filaments, cell adhesion molecules and other adapter proteins that communicate with the outer environment. Mesenchymal cells, including myoblast cells, convert actomyosin contraction forces to tension through mechano-responsive adhesion assembly complexes as Z-band equivalents. There is growing evidence that microtubule dynamics are involved in the generation of contractile forces; however, the roles of microtubules in cell adhesion dynamics are not well determined. Here, we show for the first time that αB-crystallin, a molecular chaperon for tubulin/microtubules, is involved in cell shape determination. Moreover, knockdown of this molecule caused myoblasts and glioma cells to lose their ability for adhesion as they tended to behave like migratory cells. Surprisingly, αB-crystallin knockdown in both C6 glial cells and L6 myoblast permitted cells to migrate more rapidly (2.7 times faster for C6 and 1.3 times faster for L6 cells than dermal fibroblast. On the other hand, overexpression of αB-crystallin in cells led to an immortal phenotype because of persistent adhesion. Position of matured focal adhesion as visualized by vinculin immuno-staining, stress fiber direction, length, and density were clearly αB-crystallin dependent. These results indicate that the small HSP αB-crystallin has important roles for cell adhesion, and thus microtubule

  4. Adhesive wafer bonding

    Science.gov (United States)

    Niklaus, F.; Stemme, G.; Lu, J.-Q.; Gutmann, R. J.

    2006-02-01

    Wafer bonding with intermediate polymer adhesives is an important fabrication technique for advanced microelectronic and microelectromechanical systems, such as three-dimensional integrated circuits, advanced packaging, and microfluidics. In adhesive wafer bonding, the polymer adhesive bears the forces involved to hold the surfaces together. The main advantages of adhesive wafer bonding include the insensitivity to surface topography, the low bonding temperatures, the compatibility with standard integrated circuit wafer processing, and the ability to join different types of wafers. Compared to alternative wafer bonding techniques, adhesive wafer bonding is simple, robust, and low cost. This article reviews the state-of-the-art polymer adhesive wafer bonding technologies, materials, and applications.

  5. The role of the superficial region in determining the dynamic properties of articular cartilage.

    OpenAIRE

    KELLY, DANIEL JOHN; GANNON, ALANNA

    2012-01-01

    PUBLISHED OBJECTIVE: The objective of this study was to elucidate the role of the superficial region of articular cartilage in determining the dynamic properties of the tissue. It is hypothesised that removal of the superficial region will influence both the flow dependent and independent properties of articular cartilage, leading to a reduction in the dynamic modulus of the tissue. METHODS: Osteochondral cores from the femoropatellar groove of three porcine knee joints were sub...

  6. Habitat Heterogeneity Determines Climate Impact on Zooplankton Community Structure and Dynamics

    OpenAIRE

    Otto, Saskia A.; Diekmann, Rabea; Flinkman, Juha; Kornilovs, Georgs; Möllmann, Christian

    2014-01-01

    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 ...

  7. Adhesion rings surround invadopodia and promote maturation

    Directory of Open Access Journals (Sweden)

    Kevin M. Branch

    2012-06-01

    Invasion and metastasis are aggressive cancer phenotypes that are highly related to the ability of cancer cells to degrade extracellular matrix (ECM. At the cellular level, specialized actin-rich structures called invadopodia mediate focal matrix degradation by serving as exocytic sites for ECM-degrading proteinases. Adhesion signaling is likely to be a critical regulatory input to invadopodia, but the mechanism and location of such adhesion signaling events are poorly understood. Here, we report that adhesion rings surround invadopodia shortly after formation and correlate strongly with invadopodium activity on a cell-by-cell basis. By contrast, there was little correlation of focal adhesion number or size with cellular invadopodium activity. Prevention of adhesion ring formation by inhibition of RGD-binding integrins or knockdown (KD of integrin-linked kinase (ILK reduced the number of ECM-degrading invadopodia and reduced recruitment of IQGAP to invadopodium actin puncta. Furthermore, live cell imaging revealed that the rate of extracellular MT1-MMP accumulation at invadopodia was greatly reduced in both integrin-inhibited and ILK-KD cells. Conversely, KD of MT1-MMP reduced invadopodium activity and dynamics but not the number of adhesion-ringed invadopodia. These results suggest a model in which adhesion rings are recruited to invadopodia shortly after formation and promote invadopodium maturation by enhancing proteinase secretion. Since adhesion rings are a defining characteristic of podosomes, similar structures formed by normal cells, our data also suggest further similarities between invadopodia and podosomes.

  8. Foreign material in postoperative adhesions

    NARCIS (Netherlands)

    R.W. Luijendijk; D.C.D. de Lange (Diederik C.); C.C.A.P. Wauters (C. C A P); W.C.J. Hop (Wim); J.J. Duron; J.L. Pailler; B.R. Camprodon; L. Holmdahl; H.J. van Geldorp (H.); J. Jeekel (Hans)

    1996-01-01

    textabstractObjective: The authors determined the prevalence of foreign body granulomas in intra-abdominal adhesions in patients with a history of abdominal surgery. Patients and Methods: In a cross sectional, multicenter, multinational study, adult patients with a history of one or more previous

  9. Adhesive Elastomeric Proteins

    OpenAIRE

    Mansour, Haefa; Liu, Julie

    2013-01-01

    Sutures and staples commonly used to close surgical wounds tend to be much stiffer than the surrounding tissue, often resulting in external tissue damage. Surgical adhesives provide a promising alternative to these sutures and staples. Ideal surgical adhesives are biocompatible, able to set well and remain sticky in moist conditions, possess strong adhesive and cohesive properties, and exhibit mechanical properties that mimic those of the surrounding tissue. Unfortunately, the adhesives avail...

  10. 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.

  11. Computational fluid dynamics vs. inverse dynamics methods to determine passive drag in two breaststroke glide positions.

    Science.gov (United States)

    Costa, L; Mantha, V R; Silva, A J; Fernandes, R J; Marinho, D A; Vilas-Boas, J P; Machado, L; Rouboa, A

    2015-07-16

    Computational fluid dynamics (CFD) plays an important role to quantify, understand and "observe" the water movements around the human body and its effects on drag (D). We aimed to investigate the flow effects around the swimmer and to compare the drag and drag coefficient (CD) values obtained from experiments (using cable velocimetry in a swimming pool) with those of CFD simulations for the two ventral gliding positions assumed during the breaststroke underwater cycle (with shoulders flexed and upper limbs extended above the head-GP1; with shoulders in neutral position and upper limbs extended along the trunk-GP2). Six well-trained breaststroke male swimmers (with reasonable homogeneity of body characteristics) participated in the experimental tests; afterwards a 3D swimmer model was created to fit within the limits of the sample body size profile. The standard k-ε turbulent model was used to simulate the fluid flow around the swimmer model. Velocity ranged from 1.30 to 1.70 m/s for GP1 and 1.10 to 1.50 m/s for GP2. Values found for GP1 and GP2 were lower for CFD than experimental ones. Nevertheless, both CFD and experimental drag/drag coefficient values displayed a tendency to jointly increase/decrease with velocity, except for GP2 CD where CFD and experimental values display opposite tendencies. Results suggest that CFD values obtained by single model approaches should be considered with caution due to small body shape and dimension differences to real swimmers. For better accuracy of CFD studies, realistic individual 3D models of swimmers are required, and specific kinematics respected. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. 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.

  13. Effects of different durations of acid hydrolysis on the properties of starch-based wood adhesive.

    Science.gov (United States)

    Wang, Yajie; Xiong, Hanguo; Wang, Zhenjiong; Zia-Ud-Din; Chen, Lei

    2017-10-01

    In this study, the effect of different durations of acid hydrolysis on the improvement of the properties of starch-based wood adhesive was investigated through a variety of determination methods The improved properties were analyzed using the pasting properties, viscosity, shear performance in dry and wet states, fourier infrared spectrometer, dynamic time sweep, and low filed nuclear magnetic resonance spectroscopy. Starch hydrolysis improved the viscosity stability, bonding performance, and water resistance of the starch-based wood adhesive. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Lignin-Furfural Based Adhesives

    Directory of Open Access Journals (Sweden)

    Prajakta Dongre

    2015-07-01

    Full Text Available Lignin recovered from the hot-water extract of sugar maple (Acer saccharum is used in this study to synthesize adhesive blends to replace phenol-formaldehyde (PF resin. Untreated lignin is characterized by lignin content and nuclear magnetic resonance (NMR analysis. The molecular weight distribution of the lignin and the blends are characterized by size exclusion chromatography (SEC. The effect of pH (0.3, 0.65 and 1, ex situ furfural, and curing conditions on the tensile properties of adhesive reinforced glass fibers is determined and compared to the reinforcement level of commercially available PF resin. The adhesive blend prepared at pH = 0.65 with no added furfural exhibits the highest tensile properties and meets 90% of the PF tensile strength.

  15. Corrosion protection properties and interfacial adhesion mechanism of an epoxy/polyamide coating applied on the steel surface decorated with cerium oxide nanofilm: Complementary experimental, molecular dynamics (MD) and first principle quantum mechanics (QM) simulation methods

    Science.gov (United States)

    Bahlakeh, Ghasem; Ramezanzadeh, Bahram; Saeb, Mohammad Reza; Terryn, Herman; Ghaffari, Mehdi

    2017-10-01

    The effect of cerium oxide treatment on the corrosion protection properties and interfacial interaction of steel/epoxy was studied by electrochemical impedance spectroscopy, (EIS) classical molecular dynamics (MD) and first principle quantum mechanics (QM) simulation methods X-ray photoelectron spectroscopy (XPS) was used to verify the chemical composition of the Ce film deposited on the steel. To probe the role of the curing agent in epoxy adsorption, computations were compared for an epoxy, aminoamide and aminoamide modified epoxy. Moreover, to study the influence of water on interfacial interactions the MD simulations were executed for poly (aminoamide)-cured epoxy resin in contact with the different crystallographic cerium dioxide (ceria, CeO2) surfaces including (100), (110), and (111) in the presence of water molecules. It was found that aminoamide-cured epoxy material was strongly adhered to all types of CeO2 substrates, so that binding to ceria surfaces followed the decreasing order CeO2 (111) > CeO2 (100) > CeO2 (110) in both dry and wet environments. Calculation of interaction energies noticed an enhanced adhesion to metal surface due to aminoamide curing of epoxy resin; where facets (100) and (111) revealed electrostatic and Lewis acid-base interactions, while an additional hydrogen bonding interaction was identified for CeO2 (110). Overall, MD simulations suggested decrement of adhesion to CeO2 in wet environment compared to dry conditions. Additionally, contact angle, pull-off test, cathodic delamination and salt spray analyses were used to confirm the simulation results. The experimental results in line with modeling results revealed that Ce layer deposited on steel enhanced substrate surface free energy, work of adhesion, and interfacial adhesion strength of the epoxy coating. Furthermore, decrement of adhesion of epoxy to CeO2 in presence of water was affirmed by experimental results. EIS results revealed remarkable enhancement of the corrosion

  16. 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

  17. Comparison of different methods for the determination of dynamic characteristics of low velocity anemometers

    DEFF Research Database (Denmark)

    Melikov, Arsen Krikor; Popiolek, Z.

    2004-01-01

    different and insufficient for describing the frequency response of all low velocity thermal anemometers. Therefore the upper frequency, determined in tests with sinusoidal velocity fluctuations, is recommended to be used in indoor climate standards as a single parameter describing the dynamic......Three methods for determining the dynamic characteristics of low velocity thermal anemometers were compared. They were: step-up velocity change and step-down velocity change methods and a method based on sinusoidal type velocity fluctuations. Two low velocity thermal anemometers...... with omnidirectional velocity sensors were tested. The results identify differences in frequency response of low velocity anemometers determined by the three methods. The time constant and the response time determined by the step-up velocity change method and the step-down velocity change method may be substantially...

  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. 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 (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...

  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.

    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

  1. Determination of the smoke-plume heights and their dynamics with ground-based scanning LIDAR

    Science.gov (United States)

    V. Kovalev; A. Petkov; C. Wold; S. Urbanski; W. M. Hao

    2015-01-01

    Lidar-data processing techniques are analyzed, which allow determining smoke-plume heights and their dynamics and can be helpful for the improvement of smoke dispersion and air quality models. The data processing algorithms considered in the paper are based on the analysis of two alternative characteristics related to the smoke dispersion process: the regularized...

  2. Size at hatching determines population dynamics and response to harvesting in cannibalistic fish

    NARCIS (Netherlands)

    Kooten, van T.; Andersson, J.; Bystrom, P.; Persson, L.; Roos, A.M.

    2010-01-01

    We hypothesize that size at hatching strongly affects population dynamics of cannibalistic fish species and is a crucial determinant of how populations respond to selective removal of large individuals (harvesting). We use a mechanistic mathematical model to study the relation between hatching size

  3. Comparison between universal adhesives and two-step self-etch adhesives in terms of dentin bond fatigue durability in self-etch mode.

    Science.gov (United States)

    Tsujimoto, Akimasa; Barkmeier, Wayne W; Takamizawa, Toshiki; Watanabe, Hidehiko; Johnson, William W; Latta, Mark A; Miyazaki, Masashi

    2017-06-01

    This aim of this study was to compare universal adhesives and two-step self-etch adhesives in terms of dentin bond fatigue durability in self-etch mode. Three universal adhesives - Clearfil Universal, G-Premio Bond, and Scotchbond Universal Adhesive - and three-two-step self-etch adhesives - Clearfil SE Bond, Clearfil SE Bond 2, and OptiBond XTR - were used. The initial shear bond strength and shear fatigue strength of resin composite bonded to adhesive on dentin in self-etch mode were determined. Scanning electron microscopy observations of fracture surfaces after bond strength tests were also made. The initial shear bond strength of universal adhesives was material dependent, unlike that of two-step self-etch adhesives. The shear fatigue strength of Scotchbond Universal Adhesive was not significantly different from that of two-step self-etch adhesives, unlike the other universal adhesives. The shear fatigue strength of universal adhesives differed depending on the type of adhesive, unlike those of two-step self-etch adhesives. The results of this study encourage the continued use of two-step self-etch adhesive over some universal adhesives but suggest that changes to the composition of universal adhesives may lead to a dentin bond fatigue durability similar to that of two-step self-etch adhesives. © 2017 Eur J Oral Sci.

  4. 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.

  5. Integrin LFA-1 regulates cell adhesion via transient clutch formation.

    Science.gov (United States)

    Ishibashi, Munenori; Miyanaga, Yukihiro; Matsuoka, Satomi; Kozuka, Jun; Togashi, Yuichi; Kinashi, Tatsuo; Ueda, Masahiro

    2015-08-21

    Integrin LFA-1 regulates immune cell adhesion and trafficking by binding to ICAM-1 upon chemokine stimulation. Integrin-mediated clutch formation between extracellular ICAM-1 and the intracellular actin cytoskeleton is important for cell adhesion. We applied single-molecule tracking analysis to LFA-1 and ICAM-1 in living cells to examine the ligand-binding kinetics and mobility of the molecular clutch under chemokine-induced physiological adhesion and Mn(2+)-induced tight adhesion. Our results show a transient LFA-1-mediated clutch formation that lasts a few seconds and leads to a transient lower-mobility is sufficient to promote cell adhesion. Stable clutch formation was observed for Mn(2+)-induced high affinity LFA-1, but was not required for physiological adhesion. We propose that fast cycling of the clutch formation by intermediate-affinity integrin enables dynamic cell adhesion and migration. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

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

    International Nuclear Information System (INIS)

    Xu, Dinghua; Ge, Meibao

    2012-01-01

    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. (paper)

  7. Determination of the coefficient of dynamic friction between coatings of alumina and metallic materials

    Science.gov (United States)

    Santos, A.; Córdoba, E.; Ramírez, Z.; Sierra, C.; Ortega, Y.

    2017-12-01

    This project aims to determine the coefficient of dynamic friction between micrometric size coatings of alumina and metallic materials (Steel and aluminium); the methodology used to achieve the proposed objective consisted of 4 phases, in the first one was developed a procedure that allowed, from a Pin on Disk machine built based on the specifications given by the ASTM G99-05 standard (Standard test method for wear tests with a Pin on Disk machine), to determine the coefficient of dynamic friction between two materials in contact; subsequently the methodology was verified through tests between steel-steel and steel-aluminium, due to these values are widely reported in the literature; as a third step, deposits of alumina particles of micrometric size were made on a steel substrate through thermal spraying by flame; finally, the tests were carried out between pins of steel of aluminium and alumina coating to determine the coefficients of dynamic friction between these two surfaces. The results of the project allowed to verify that the developed methodology is valid to obtain coefficients of dynamic friction between surfaces in contact since the percentages of error were of 3.5% and 2.1% for steel-steel and aluminium-steel, respectively; additionally, it was found that the coefficient of friction between steel-alumina coatings is 0.36 and aluminium-alumina coating is 0.25.

  8. An Iterative Algorithm to Determine the Dynamic User Equilibrium in a Traffic Simulation Model

    Science.gov (United States)

    Gawron, C.

    An iterative algorithm to determine the dynamic user equilibrium with respect to link costs defined by a traffic simulation model is presented. Each driver's route choice is modeled by a discrete probability distribution which is used to select a route in the simulation. After each simulation run, the probability distribution is adapted to minimize the travel costs. Although the algorithm does not depend on the simulation model, a queuing model is used for performance reasons. The stability of the algorithm is analyzed for a simple example network. As an application example, a dynamic version of Braess's paradox is studied.

  9. The adhesive strength and initial viscosity of denture adhesives.

    Science.gov (United States)

    Han, Jian-Min; Hong, Guang; Dilinuer, Maimaitishawuti; Lin, Hong; Zheng, Gang; Wang, Xin-Zhi; Sasaki, Keiichi

    2014-11-01

    To examine the initial viscosity and adhesive strength of modern denture adhesives in vitro. Three cream-type denture adhesives (Poligrip S, Corect Cream, Liodent Cream; PGS, CRC, LDC) and three powder-type denture adhesives (Poligrip Powder, New Faston, Zanfton; PGP, FSN, ZFN) were used in this study. The initial viscosity was measured using a controlled-stress rheometer. The adhesive strength was measured according to ISO-10873 recommended procedures. All data were analyzed independently by one-way analysis of variance combined with a Student-Newman-Keuls multiple comparison test at a 5% level of significance. The initial viscosity of all the cream-type denture adhesives was lower than the powder-type adhesives. Before immersion in water, all the powder-type adhesives exhibited higher adhesive strength than the cream-type adhesives. However, the adhesive strength of cream-type denture adhesives increased significantly and exceeded the powder-type denture adhesives after immersion in water. For powder-type adhesives, the adhesive strength significantly decreased after immersion in water for 60 min, while the adhesive strength of the cream-type adhesives significantly decreased after immersion in water for 180 min. Cream-type denture adhesives have lower initial viscosity and higher adhesive strength than powder type adhesives, which may offer better manipulation properties and greater efficacy during application.

  10. Comparison of enamel bond fatigue durability of universal adhesives and two-step self-etch adhesives in self-etch mode.

    Science.gov (United States)

    Tsujimoto, Akimasa; Barkmeier, Wayne W; Hosoya, Yumiko; Nojiri, Kie; Nagura, Yuko; Takamizawa, Toshiki; Latta, Mark A; Miyazaki, Masashi

    2017-10-01

    To comparatively evaluate universal adhesives and two-step self-etch adhesives for enamel bond fatigue durability in self-etch mode. Three universal adhesives (Clearfil Universal Bond; G-Premio Bond; Scotchbond Universal Adhesive) and three two-step self-etch adhesives (Clearfil SE Bond; Clearfil SE Bond 2; OptiBond XTR) were used. The initial shear bond strength and shear fatigue strength of the adhesive to enamel in self-etch mode were determined. The initial shear bond strengths of the universal adhesives to enamel in self-etch mode was significantly lower than those of two-step self-etch adhesives and initial shear bond strengths were not influenced by type of adhesive in each adhesive category. The shear fatigue strengths of universal adhesives to enamel in self-etch mode were significantly lower than that of Clearfil SE Bond and Clearfil SE Bond 2, but similar to that OptiBond XTR. Unlike two-step self-etch adhesives, the initial shear bond strength and shear fatigue strength of universal adhesives to enamel in self-etch mode was not influenced by the type of adhesive. This laboratory study showed that the enamel bond fatigue durability of universal adhesives was lower than Clearfil SE Bond and Clearfil SE Bond 2, similar to Optibond XTR, and was not influenced by type of adhesive, unlike two-step self-etch adhesives.

  11. 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

  12. Synaptic Cell Adhesion

    OpenAIRE

    Missler, Markus; Südhof, Thomas C.; Biederer, Thomas

    2012-01-01

    Chemical synapses are asymmetric intercellular junctions that mediate synaptic transmission. Synaptic junctions are organized by trans-synaptic cell adhesion molecules bridging the synaptic cleft. Synaptic cell adhesion molecules not only connect pre- and postsynaptic compartments, but also mediate trans-synaptic recognition and signaling processes that are essential for the establishment, specification, and plasticity of synapses. A growing number of synaptic cell adhesion molecules that inc...

  13. 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

  14. 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.

  15. 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.

  16. Influence of Application Time and Etching Mode of Universal Adhesives on Enamel Adhesion.

    Science.gov (United States)

    Sai, Keiichi; Takamizawa, Toshiki; Imai, Arisa; Tsujimoto, Akimasa; Ishii, Ryo; Barkmeier, Wayne W; Latta, Mark A; Miyazaki, Masashi

    2018-01-01

    To investigate the influence of application time and etching mode of universal adhesives on enamel adhesion. Five universal adhesives, Adhese Universal, Bondmer Lightless, Clearfil Universal Bond Quick, G-Premio Bond, and Scotchbond Universal, were used. Bovine incisors were prepared and divided into four groups of ten teeth each. SBS, Ra, and SFE were determined after the following procedures: 1. self-etch mode with immediate air blowing after application (IA); 2. self-etch mode with prolonged application time (PA); 3. etch-and-rinse mode with IA; 4. etch-and-rinse mode with PA. After 24-h water storage, the bonded assemblies were subjected to shear bond strength (SBS) tests. For surface roughness (Ra) and surface free energy (SFE) measurements, the adhesives were simply applied to the enamel and rinsed with acetone and water before the measurements were carried out. Significantly higher SBS and Ra values were obtained with etch-and-rinse mode than with self-etch mode regardless of the application time or type of adhesive. Although most adhesives showed decreased SFE values with increased application time in self-etch mode, SFE values in etch-and-rinse mode were dependent on the adhesive type and application time. Etching mode, application time, and type of adhesive significantly influenced the SBS, Ra, and SFE values.

  17. A Dynamic Model for GPS Based Attitude Determination and Testing using a Serial Robotic Manipulator

    OpenAIRE

    Raskaliyev, Almat; Patel, Sarosh; Sobh, Tarek

    2017-01-01

    A computational algorithm is developed for estimating accurately the attitude of a robotic arm which moves along a predetermined path. This algorithm requires preliminary input data obtained in the static mode to yield phase observables for the precise, 3-axis attitude determination of a swinging manipulator in the dynamic mode. Measurements are recorded simultaneously by three GPS L1 receivers and then processed in several steps to accomplish this task. First, artkconv batch executable conve...

  18. 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.

  19. Determinants of inbound tourists in Cambodia : a dynamic panel data approach

    OpenAIRE

    Tanaka, Kiyoyasu

    2016-01-01

    Understanding the determinants of tourism demand is crucial for the tourism sector. This paper develops a dynamic panel model to examine the determinants of inbound tourists to Siem Reap airport, Phnom Penh airport, and land and waterway borders in Cambodia. Consistent with the consumer theory of tourism consumption, a 10% increase in the origin country GDP per capita is predicted to increase the number of tourist visits to Siem Reap airport by 5.8%. A 10% increase in the real exchange rate b...

  20. A hybrid total internal reflection fluorescence and optical tweezers microscope to study cell adhesion and membrane protein dynamics of single living cells

    NARCIS (Netherlands)

    Snijder-van As, M.I.; Rieger, B.; Joosten, B.; Subramaniam, Vinod; Figdor, Carl; Kanger, Johannes S.

    2009-01-01

    The dynamics of cell surface membrane proteins plays an important role in cell–cell interactions. The onset of the interaction is typically not precisely controlled by current techniques, making especially difficult the visualization of early-stage dynamics. We have developed a novel method where

  1. Using weigh-in-motion data to determine bridge dynamic amplification factor

    Directory of Open Access Journals (Sweden)

    Kalin Jan

    2015-01-01

    Full Text Available The dynamic component of bridge traffic loading is commonly taken into account with a Dynamic Amplification Factor (DAF – the ratio between the maximum dynamic and static load effects on a bridge. In the design codes, this factor is generally higher than in reality. While this is fine for new bridges that must account for various risks during their life-time, it imposes unnecessary conservativism into assessment of the existing well defined bridges. Therefore, analysis of existing bridges should apply more realistic DAF values. One way of obtaining them experimentally is by bridge weigh-in-motion (B-WIM measurements, which use an existing instrumented bridge or culvert to weigh all crossing vehicles at highway speeds. The B-WIM system had been equipped with two methods of obtaining an approximation to the static response of the. The first method uses the sum of influence lines. This method relies on accurate axle identification, the failure of which can have a large influence on the DAF value. The other method uses a pre-determined low-pass filter to remove the dynamic component of the measured signal; however an expert is needed to set the filter parameters. A new approach that tries to eliminate these two drawbacks has been developed. In this approach the parameters for the filter are determined automatically by fitting the filtered response to the sum of the influence lines. The measurement of DAF on a typical bridge site agrees with experiments performed in the ARCHES [1] project: dynamic amplification decreases as static loading increases.

  2. Soy protein adhesives

    Science.gov (United States)

    Charles R. Frihart

    2010-01-01

    In the quest to manufacture and use building materials that are more environmentally friendly, soy adhesives can be an important component. Trees fix and store carbon dioxide in the atmosphere. After the trees are harvested, machinery converts the wood into strands, which are then bonded together with adhesives to form strandboard, used in constructing long-lasting...

  3. Adhesive compositions and methods

    Energy Technology Data Exchange (ETDEWEB)

    Allen, Scott D.; Sendijarevic, Vahid; O' Connor, James

    2017-12-05

    The present invention encompasses polyurethane adhesive compositions comprising aliphatic polycarbonate chains. In one aspect, the present invention encompasses polyurethane adhesives derived from aliphatic polycarbonate polyols and polyisocyanates wherein the polyol chains contain a primary repeating unit having a structure:. In another aspect, the invention provides articles comprising the inventive polyurethane compositions as well as methods of making such compositions.

  4. Instant acting adhesive system

    Science.gov (United States)

    Davis, T. R.; Haines, R. C.

    1971-01-01

    Adhesive developes 80 percent of minimum bond strength of 250 psi less than 30 sec after activation is required. Adhesive is stable, handles easily, is a low toxic hazard, and is useful in industrial and domestic prototype bonding and clamping operations.

  5. Prevention of bacterial adhesion

    DEFF Research Database (Denmark)

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

    2010-01-01

    Management of bacterial infections is becoming increasingly difficult due to the emergence and increasing prevalence of bacterial pathogens that are resistant to available antibiotics. Conventional antibiotics generally kill bacteria by interfering with vital cellular functions, an approach...... 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...

  6. The dynamics of the plasmasphere boundary layer as determined by ground magnetometers, satellite observations, and modeling

    Science.gov (United States)

    Zesta, E.; Boudouridis, A.; Yizengaw, E.; Jorgensen, A. M.; Carranza-fulmer, T. L.; Moldwin, M.; Mann, I. R.; Chi, P. J.

    2013-12-01

    The plasmasphere boundary layer (PBL) separates the cold and dense plasmaspheric plasma from the more tenuous and hot plasma sheet plasma and organizes the spatial distribution of ULF and VLF waves that can contribute to acceleration or loss processes of radiation belt particles through wave-particle interactions. The PBL has been traditionally determined by in situ observations and can be given by empirical models. Recent work has shown that a mid-latitude chain of well-spaced ground magnetometers can also determine the PBL location. Spectral properties, like the cross-phase reversal in the standard field-line resonance (FLR) determination between two stations closely aligned in latitude, have been shown to indicate the presence of a sharp PBL. We merge data from many ground magnetometer pairs from the SAMBA (South American Meridional B-field Array), McMAC (Mid continent Magnetoseismic Chain), and CARISMA (Canadian Array for Realtime Investigations of Magnetic Activity) chains to provide the best available spatial coverage in L values spanning the plasmasphere and PBL, for a range of dynamic states (L=1.6 to greater than 5). The PBL location is identified as the L value of the station pair for which a reverse phase difference is observed in the standard FLR determination. We compare the FLR determined PBL with the trough boundary determined by GPS Total Electron Content (TEC) analysis and with model PBL. Initial results demonstrate that the PBL as identified by the reverse phase differences is in general agreement with TEC identifications and reasonable agreement with models. Reverse Phase Differences are regularly observed at the L range of 2.7 to 3.7 and are highly correlated with Dst and Kp, as determined by daily correlations. We further examine the more detailed time sequence of the PBL dynamics by focusing on key periods around storms preceded by quiet periods, and by using the full L range of the ground magnetometer pairs.

  7. A dynamic model for GPS based attitude determination and testing using a serial robotic manipulator.

    Science.gov (United States)

    Raskaliyev, Almat; Patel, Sarosh; Sobh, Tarek

    2017-07-01

    A computational algorithm is developed for estimating accurately the attitude of a robotic arm which moves along a predetermined path. This algorithm requires preliminary input data obtained in the static mode to yield phase observables for the precise, 3-axis attitude determination of a swinging manipulator in the dynamic mode. Measurements are recorded simultaneously by three GPS L1 receivers and then processed in several steps to accomplish this task. First, artkconv batch executable converts GPS receiver readings into RINEX format to generate GPS observables and ephemeris for multiple satellites. Then baseline vectors determination is carried out by baseline constrained Least-Squares Ambiguity Decorrelation (LAMBDA) method that uses double difference carrier phase estimates as input to calculate integer solution for each baseline. Finally, attitude determination is made by employing alternatively Least-squares attitude determination (LSAD) in the static mode and extended Kalman filter in the dynamic mode. The algorithm presented in this paper is applied to recorded data on Mitsubishi RV-M1 robotic arm in order to produce attitude estimates. These results are confirmed by another set of Euler angles independently evaluated from robotic arm postures obtained along the predefined trajectory.

  8. A dynamic model for GPS based attitude determination and testing using a serial robotic manipulator

    Directory of Open Access Journals (Sweden)

    Almat Raskaliyev

    2017-07-01

    Full Text Available A computational algorithm is developed for estimating accurately the attitude of a robotic arm which moves along a predetermined path. This algorithm requires preliminary input data obtained in the static mode to yield phase observables for the precise, 3-axis attitude determination of a swinging manipulator in the dynamic mode. Measurements are recorded simultaneously by three GPS L1 receivers and then processed in several steps to accomplish this task. First, artkconv batch executable converts GPS receiver readings into RINEX format to generate GPS observables and ephemeris for multiple satellites. Then baseline vectors determination is carried out by baseline constrained Least-Squares Ambiguity Decorrelation (LAMBDA method that uses double difference carrier phase estimates as input to calculate integer solution for each baseline. Finally, attitude determination is made by employing alternatively Least-squares attitude determination (LSAD in the static mode and extended Kalman filter in the dynamic mode. The algorithm presented in this paper is applied to recorded data on Mitsubishi RV-M1 robotic arm in order to produce attitude estimates. These results are confirmed by another set of Euler angles independently evaluated from robotic arm postures obtained along the predefined trajectory.

  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. 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.

  11. Bloodstain Pattern Analysis: implementation of a fluid dynamic model for position determination of victims

    Science.gov (United States)

    Laan, Nick; de Bruin, Karla G.; Slenter, Denise; Wilhelm, Julie; Jermy, Mark; Bonn, Daniel

    2015-06-01

    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 and drag and thus overestimating the height of the source. We determined how accurately the location of the origin can be estimated when including gravity and drag into the trajectory reconstruction. We created eight bloodstain patterns at one meter distance from the wall. The origin’s location was determined for each pattern with: the straight-line approximation, our method including gravity, and our method including both gravity and drag. The latter two methods require the volume and impact velocity of each bloodstain, which we are able to determine with a 3D scanner and advanced fluid dynamics, respectively. We conclude that by including gravity and drag in the trajectory calculation, the origin’s location can be determined roughly four times more accurately than with the straight-line approximation. Our study enables investigators to determine if the victim was sitting or standing, or it might be possible to connect wounds on the body to specific patterns, which is important for crime scene reconstruction.

  12. GPS Based Reduced-Dynamic Orbit Determination for Low Earth Orbiters with Ambiguity Fixing

    Directory of Open Access Journals (Sweden)

    Yang Yang

    2015-01-01

    Full Text Available With the ever-increasing number of satellites in Low Earth Orbit (LEO for scientific missions, the precise determination of the position and velocity of the satellite is a necessity. GPS (Global Positioning System based reduced-dynamic orbit determination (RPOD method is commonly used in the post processing with high precision. This paper presents a sequential RPOD strategy for LEO satellite in the framework of Extended Kalman Filter (EKF. Precise Point Positioning (PPP technique is used to process the GPS observations, with carrier phase ambiguity resolution using Integer Phase Clocks (IPCs products. A set of GRACE (Gravity Recovery And Climate Experiment mission data is used to test and validate the RPOD performance. Results indicate that orbit determination accuracy could be improved by 15% in terms of 3D RMS error in comparison with traditional RPOD method with float ambiguity solutions.

  13. Signal Processing for Determining Water Height in Steam Pipes with Dynamic Surface Conditions

    Science.gov (United States)

    Lih, Shyh-Shiuh; Lee, Hyeong Jae; Bar-Cohen, Yoseph

    2015-01-01

    An enhanced signal processing method based on the filtered Hilbert envelope of the auto-correlation function of the wave signal has been developed to monitor the height of condensed water through the steel wall of steam pipes with dynamic surface conditions. The developed signal processing algorithm can also be used to estimate the thickness of the pipe to determine the cut-off frequency for the low pass filter frequency of the Hilbert Envelope. Testing and analysis results by using the developed technique for dynamic surface conditions are presented. A multiple array of transducers setup and methodology are proposed for both the pulse-echo and pitch-catch signals to monitor the fluctuation of the water height due to disturbance, water flow, and other anomaly conditions.

  14. Determination of Quantum Chemistry Based Force Fields for Molecular Dynamics Simulations of Aromatic Polymers

    Science.gov (United States)

    Jaffe, Richard; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    Ab initio quantum chemistry calculations for model molecules can be used to parameterize force fields for molecular dynamics simulations of polymers. Emphasis in our research group is on using quantum chemistry-based force fields for molecular dynamics simulations of organic polymers in the melt and glassy states, but the methodology is applicable to simulations of small molecules, multicomponent systems and solutions. Special attention is paid to deriving reliable descriptions of the non-bonded and electrostatic interactions. Several procedures have been developed for deriving and calibrating these parameters. Our force fields for aromatic polyimide simulations will be described. In this application, the intermolecular interactions are the critical factor in determining many properties of the polymer (including its color).

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

    Science.gov (United States)

    Afrooz, A. R. M. Nabiul; Hussain, Saber M.; Saleh, Navid B.

    2014-12-01

    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.

  16. Structure and dynamics of porcine submaxillary mucin as determined by natural abundance carbon-13 NMR spectroscopy

    International Nuclear Information System (INIS)

    Gerken, T.A.; Jentoft, N.

    1987-01-01

    Nearly all of the resonances in the 13 C NMR spectrum of porcine submaxillary mucin glycoprotein (PSM) have been assigned to the peptide core carbons and to the carbons in the eight different oligosaccharide side chains that arise from the incomplete biosynthesis of the sialylated A blood group pentasaccharide. By use of these assignments, a nearly complete structural analysis of intact PSM has been performed without resorting to degradative chemical methods. Considerable structural variability in the carbohydrate side chains was observed between mucins obtained from different animals, while no variability was observed between glands in a single animal. The dynamics of the PSM core and carbohydrate side chains were examined by using the carbon-13 nuclear magnetic resonance relaxation times and nuclear Overhauser enhancements of each assigned carbon resonance. The peptide core of PSM exhibits internal segmental flexibility that is virtually identical with that of ovine submaxillary mucin (OSM), whose carbohydrate side chain consists of the α-NeuNAc(2-6)α-Ga1NAc disaccharide. These results differ from most reports of glycoprotein dynamics, which typically find the terminal carbohydrate residues to be undergoing rapid internal rotation about their terminal glycosidic bonds. The results reported here are consistent with previous studies on the conformations of the A and H determinants derived from model oligosaccharides and further indicate that the conformations of these determinants are unchanged when covalently bound to the mucin peptide core. In spite of their carbohydrate side-chain heterogeneity, mucins appear to be ideal glycoproteins for the study of O-linked oligosaccharide conformation and dynamics and for the study of the effects of glycosylation on polypeptide conformation and dynamics

  17. Experimental determination of the distributed dynamic coefficients for a hydrodynamic fluid film bearing

    Science.gov (United States)

    Gyurko, John Harrison

    Most current rotor bearing analysis utilizes lumped parameter bearing coefficients to model the static and dynamic characteristics of fluid film bearings. By treating the stiffness and damping properties of the fluid film as acting upon the axial centerline of the rotor, these models are limited in their analysis to first order lateral rotor-bearing motion. The development of numerical methods that distribute the dynamic properties of the fluid film around the bearing circumference allow for higher order analysis of the motion between the bearing and rotor. Assessment of the accuracy of the numerical method used to calculate distributed dynamic fluid film bearing coefficients is performed by developing a novel hydrodynamic journal bearing test rig and experimental testing procedure capable of obtaining measured distributed dynamic coefficients over a range of bearing operating conditions. The instrumented bearing test rig is used to measure the dynamic bearing displacement and fluid film pressure responses from application of an externally applied excitation force. Least squares solution to a system of perturbated pressure equations, populated by measured displacement and pressure responses, is used to determine the hydrodynamic stiffness and damping properties for a finite region of the bearing surface. Incremental rotation of pressure sensors embedded in the body of the test bearing allow for measurement of the fluid film circumferential pressure distribution which is used to calculate a set of experimentally determined dynamic bearing coefficients. Distributed bearing coefficients derived from experimental measurements are compared to numerically calculated distributed coefficients as well as to lumped parameter coefficients generated from experimental and numerical methods found in the literature. Overall, the numerically calculated distributed coefficients successfully model both the circumferential distribution and the operating conditions of the experimental

  18. Controllable biomimetic adhesion using embedded phase change material

    International Nuclear Information System (INIS)

    Krahn, J; Sameoto, D; Menon, C

    2011-01-01

    In many cases, such as in the instance of climbing robots or temporary adhesives, there is the need to be able to dynamically control the level of adhesion a biomimetic dry adhesive can provide. In this study, the effect of changing the backing layer stiffness of a dry adhesive is examined. Embedding a phase change material within the backing of a synthetic dry adhesive sheet allows the stiffness to be tailored at different points of a preload and adhesion cycle. Larger contact areas and more equal load sharing between adhesive fibres can be achieved by increasing the backing layer stiffness after initial deformation when the adhesive backing is loaded in its softened state. Adhesion behaviour is examined when the backing layer is maintained in solid and softened phases during complete load cycles and for load cycles under the condition of contact with the softened phase backing followed by pull-off during the solid phase. Absolute adhesion force is increased for trials in which a soft backing layer hardens prior to pull-off. This effect is due to the increased contact area made between the rounded probe and the softened material during preloading and the more equal load sharing condition during pull-off when the backing layer becomes stiff again

  19. The role of adhesion energy in controlling cell?cell contacts

    OpenAIRE

    Ma?tre, Jean-L?on; Heisenberg, Carl-Philipp

    2011-01-01

    Recent advances in microscopy techniques and biophysical measurements have provided novel insight into the molecular, cellular and biophysical basis of cell adhesion. However, comparably little is known about a core element of cell?cell adhesion?the energy of adhesion at the cell?cell contact. In this review, we discuss approaches to understand the nature and regulation of adhesion energy, and propose strategies to determine adhesion energy between cells in vitro and in vivo.

  20. 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.

  1. Determination of dynamic mechanical properties of silica aerogel by resonance and non-resonance method

    Science.gov (United States)

    Qu, Z. P.; Sheng, M. P.

    2017-03-01

    Silica aerogel has great potential in aeronautics, building construction, and offshore oil transportation. The dynamic mechanical properties of silica aerogel were measured by the resonance and non-resonance method. The results of the two methods were compared. While the Young’s modulus coincided well, the loss factor had big difference. To explain this phenomenon, the sensitivity of the two methods was analyzed. It shows that the loss factor determination of low-loss materials by the non-resonance method is quite sensitive to the experiment uncertainties. This probably results in the loss factor difference between the two methods.

  2. The determination of the attitude and attitude dynamics of TeamSat

    DEFF Research Database (Denmark)

    Betto, Maurizio; Jørgensen, John Leif; Riis, Troels

    1999-01-01

    The second qualification flight of Ariane 5 was launched from the European Space Port in French Guiana on October 30, 1997. It carried on board a small technology demonstration satellite dubbed TeamSat into which five experiments, proposed by various universities and research institutions, were...... integrated. Among them, the Autonomous Vision System, AVS, a fully autonomous star tracker and vision system. This paper gives a short overview of the TeamSat satellite design, implementation and mission objectives. The AVS is described in more details. The main science objectives of the AVS were to verify...... determined the attitude and attitude dynamics of TeamSat....

  3. Comparison of experimental methods for determination of dynamic properties of viscoelastic material

    Science.gov (United States)

    Yam, L. H.; Kong, Leung H.; Wah, Lee W.; Fai, Fung K.

    1993-09-01

    Four experimental methods for determination of dynamic mechanical properties of viscoelastic materials are presented. The first and the second ones are the strain and acceleration measurement at two different crosssections of an axially impacted rod specimen respectively. The third method adopts resonance technique and the fourth one is correction method. Tests are carried out with Nylon 6 and Polyurethane(pU) . The diagrams of complex Young''s modulus and loss factor versus frequency are obtained. Comparison shows that the results from these four methods are reasonably close. The useful frequency ranges for valid results for each method are discussed.

  4. Immediate postarousal sleep dynamics: an important determinant of sleep stability in obstructive sleep apnea.

    Science.gov (United States)

    Younes, Magdy; Hanly, Patrick J

    2016-04-01

    Arousability from sleep is increasingly recognized as an important determinant of the clinical spectrum of sleep disordered breathing (SDB). Patients with SDB display a wide range of arousability. The reason for these differences is not known. We hypothesized that differences in the speed with which sleep deepens following arousals/awakenings (postarousal sleep dynamics) is a major determinant of these differences in arousability in patients with SDB. We analyzed 40 preexisting clinical polysomnography records from patients with a range of SDB severity (apnea-hypopnea index 5-135/h). Sleep depth was determined every 3 s using the odds ratio product (ORP) method, a continuous index of sleep depth (0 = deep sleep, 2.5 = full wakefulness) that correlates strongly (r = 0.98) with arousability (Younes M, Ostrowski M, Soiferman M, Younes H, Younes M, Raneri J, and Hanly P. Sleep 38: 641-654, 2015). Time course of ORP was determined from end of arousal until the next arousal. All arousals were analyzed (142 ± 65/polysomnogram). ORP increased from 0.58 ± 0.32 during sleep to 1.67 ± 0.35 during arousals. ORP immediately (first 9 s) following arousals/awakenings (ORP-9) ranged from 0.21(very deep sleep) to 1.71 (highly arousable state) in different patients. In patients with high ORP-9, sleep deepened slowly (over minutes) beyond 9 s but only if no arousals/awakenings recurred. ORP-9 correlated strongly with average non-rapid eye movement sleep depth (r = 0.87, P change on continuous positive airway pressure despite marked improvement in sleep architecture. We conclude that postarousal sleep dynamics are highly variable among patients with sleep-disordered breathing and largely determine average sleep depth and continuity. Copyright © 2016 the American Physiological Society.

  5. EB curable laminating adhesives

    International Nuclear Information System (INIS)

    Matsuyama, Asao; Kobayashi, Masahide; Gotoh, Sakiko

    1992-01-01

    New developed solvent free EB curable laminating adhesives have two liquid components, A with hydroxy and acryloyl group, B with isocyanate and acryloyl group in a molecule. These EB laminating adhesives do not need any aging process, which is a big advantage, and are very suitable for environment, safety, and health because of no heating process and solvent free formulas. And we have made basic research about the relation of peel strength or heat seal strength versus Tg of cured film, elongation at break, elastic modulus, and so on. Basic specifications of the new developed adhesives are shown. (author)

  6. Main Effect QTL with Dominance Determines Heterosis for Dynamic Plant Height in Upland Cotton.

    Science.gov (United States)

    Shang, Lianguang; Ma, Lingling; Wang, Yumei; Su, Ying; Wang, Xiaocui; Li, Yuhua; Abduweli, Abdugheni; Cai, Shihu; Liu, Fang; Wang, Kunbo; Hua, Jinping

    2016-10-13

    Plant height, which shows dynamic development and heterosis, is a major trait affecting plant architecture and has an indirect influence on economic yield related to biological yield in cotton. In the present study, we carried out dynamic analysis for plant height and its heterosis by quantitative trait loci (QTL) mapping at multiple developmental stages using two recombinant inbred lines (RILs) and their backcross progeny. At the single-locus level, 47 QTL were identified at five developmental stages in two hybrids. In backcross populations, QTL identified at an early stage mainly showed partial effects and QTL detected at a later stage mostly displayed overdominance effects. At the two-locus level, we found that main effect QTL played a more important role than epistatic QTL in the expression of heterosis in backcross populations. Therefore, this study implies that the genetic basis of plant height heterosis shows dynamic character and main effect QTL with dominance determines heterosis for plant height in Upland cotton. Copyright © 2016 Shang et al.

  7. Determination of Dynamics of Plant Plasma Membrane Proteins with Fluorescence Recovery and Raster Image Correlation Spectroscopy.

    Science.gov (United States)

    Laňková, Martina; Humpolíčková, Jana; Vosolsobě, Stanislav; Cit, Zdeněk; Lacek, Jozef; Čovan, Martin; Čovanová, Milada; Hof, Martin; Petrášek, Jan

    2016-04-01

    A number of fluorescence microscopy techniques are described to study dynamics of fluorescently labeled proteins, lipids, nucleic acids, and whole organelles. However, for studies of plant plasma membrane (PM) proteins, the number of these techniques is still limited because of the high complexity of processes that determine the dynamics of PM proteins and the existence of cell wall. Here, we report on the usage of raster image correlation spectroscopy (RICS) for studies of integral PM proteins in suspension-cultured tobacco cells and show its potential in comparison with the more widely used fluorescence recovery after photobleaching method. For RICS, a set of microscopy images is obtained by single-photon confocal laser scanning microscopy (CLSM). Fluorescence fluctuations are subsequently correlated between individual pixels and the information on protein mobility are extracted using a model that considers processes generating the fluctuations such as diffusion and chemical binding reactions. As we show here using an example of two integral PM transporters of the plant hormone auxin, RICS uncovered their distinct short-distance lateral mobility within the PM that is dependent on cytoskeleton and sterol composition of the PM. RICS, which is routinely accessible on modern CLSM instruments, thus represents a valuable approach for studies of dynamics of PM proteins in plants.

  8. Main Effect QTL with Dominance Determines Heterosis for Dynamic Plant Height in Upland Cotton

    Directory of Open Access Journals (Sweden)

    Lianguang Shang

    2016-10-01

    Full Text Available Plant height, which shows dynamic development and heterosis, is a major trait affecting plant architecture and has an indirect influence on economic yield related to biological yield in cotton. In the present study, we carried out dynamic analysis for plant height and its heterosis by quantitative trait loci (QTL mapping at multiple developmental stages using two recombinant inbred lines (RILs and their backcross progeny. At the single-locus level, 47 QTL were identified at five developmental stages in two hybrids. In backcross populations, QTL identified at an early stage mainly showed partial effects and QTL detected at a later stage mostly displayed overdominance effects. At the two-locus level, we found that main effect QTL played a more important role than epistatic QTL in the expression of heterosis in backcross populations. Therefore, this study implies that the genetic basis of plant height heterosis shows dynamic character and main effect QTL with dominance determines heterosis for plant height in Upland cotton.

  9. Geckolike high shear strength by carbon nanotube fiber adhesives

    Science.gov (United States)

    Maeno, Y.; Nakayama, Y.

    2009-01-01

    Carbon nanotube adhesives can adhere strongly to surfaces as a gecko does. The number of carbon nanotube layers is an important determinant of the contact area for adhesion. Balancing the catalyst ratio and buffer layer used for chemical vapor deposition processing controls the number of carbon nanotube layers and their distribution. The features of carbon nanotubes determine the shear strength of adhesion. Carbon nanotubes with a broad distribution of layers exhibit enhanced shear strength with equivalent adhesive capability to that of a natural Tokay Gecko (Gekko gecko)

  10. Free energy of melts and intermetallic compounds of binary alloys determined by a molecular dynamics approach.

    Science.gov (United States)

    Guerdane, M

    2014-02-01

    We present an atomistic approach aimed at determining the free energy g(liq) of binary alloy liquids, a quantity which governs the thermodynamics of phase transformations and whose evaluation has long been a challenge to modeling methods. Our approach, illustrated here for a metallic system model NiZr, combines two methods: the quasiharmonic approximation, applied for some existing (real or hypothetical) intermetallic compounds, and the liquid-solid coexistence conditions. The underlying equations for g(liq) are solved by means of a subregular-solution approximation. We demonstrate the high reliability of our calculated free energies in determining the phase diagram of a binary system and describing quantitatively the growth kinetics. The latter issue is illustrated by linking molecular dynamics simulations to phase-field modeling with regard to directional solidification and melting in a two-phase system [Ni(x)Zr(1-x)](liq)-Zr(cryst) out of chemical equilibrium.

  11. 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

  12. Cohesion and Adhesion with Proteins

    Science.gov (United States)

    Charles R. Frihart

    2016-01-01

    With increasing interest in bio-based adhesives, research on proteins has expanded because historically they have been used by both nature and humans as adhesives. A wide variety of proteins have been used as wood adhesives. Ancient Egyptians most likely used collagens tobond veneer to wood furniture, then came casein (milk), blood, fish scales, and soy adhesives, with...

  13. Inverse Force Determination on a Small Scale Launch Vehicle Model Using a Dynamic Balance

    Science.gov (United States)

    Ngo, Christina L.; Powell, Jessica M.; Ross, James C.

    2017-01-01

    A launch vehicle can experience large unsteady aerodynamic forces in the transonic regime that, while usually only lasting for tens of seconds during launch, could be devastating if structural components and electronic hardware are not designed to account for them. These aerodynamic loads are difficult to experimentally measure and even harder to computationally estimate. The current method for estimating buffet loads is through the use of a few hundred unsteady pressure transducers and wind tunnel test. Even with a large number of point measurements, the computed integrated load is not an accurate enough representation of the total load caused by buffeting. This paper discusses an attempt at using a dynamic balance to experimentally determine buffet loads on a generic scale hammer head launch vehicle model tested at NASA Ames Research Center's 11' x 11' transonic wind tunnel. To use a dynamic balance, the structural characteristics of the model needed to be identified so that the natural modal response could be and removed from the aerodynamic forces. A finite element model was created on a simplified version of the model to evaluate the natural modes of the balance flexures, assist in model design, and to compare to experimental data. Several modal tests were conducted on the model in two different configurations to check for non-linearity, and to estimate the dynamic characteristics of the model. The experimental results were used in an inverse force determination technique with a psuedo inverse frequency response function. Due to the non linearity, the model not being axisymmetric, and inconsistent data between the two shake tests from different mounting configuration, it was difficult to create a frequency response matrix that satisfied all input and output conditions for wind tunnel configuration to accurately predict unsteady aerodynamic loads.

  14. Experimental and numerical determination of the dynamic properties of the reactor building of Atucha II NPP

    International Nuclear Information System (INIS)

    Ceballos, M.A.; Car, E.J.; Prato, T.A.; Prato, C.A.; Alvarez, L.M.; Godoy, A.R.

    1995-01-01

    Determination of the dynamic properties of the reactor building of Atucha II NPP is carried out in order to: i) Obtain valuable information for seismic qualification of the plant, and ii) Assess some procedures for testing and analysis that are used in the process of seismic evaluation of existing nuclear facilities founded on Quaternary soil deposits. Both steady state and impulsive dynamic tests were performed but attention is centered here in tile techniques used to determine natural frequencies and modal damping ratios with impulsive tests. Numerical analyses were performed by means of a 3-D model model of the superstructure together with foundation stiffness coefficients derived in a separate paper from steady state vibration tests, and also from analysis with a 2-D F.E. model of the soil layers capable of approximating the 3-D features of the problem. The computed foundation stiffness coefficients are compared both with those obtained from the tests and from an axisymmetric F.E. model; results indicate that foundation stiffness coefficients calculated with F.E. models with soil parameters given by laboratory tests performed on cored samples are significantly lower than those given by the steady state vibration tests. (author)

  15. 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. (c) 2016 APA, all rights reserved).

  16. 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.

  17. 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.

  18. Adhesive properties and adhesive joints strength of graphite/epoxy composites

    Science.gov (United States)

    Rudawska, Anna; Stančeková, Dana; Cubonova, Nadezda; Vitenko, Tetiana; Müller, Miroslav; Valášek, Petr

    2017-05-01

    The article presents the results of experimental research of the adhesive joints strength of graphite/epoxy composites and the results of the surface free energy of the composite surfaces. Two types of graphite/epoxy composites with different thickness were tested which are used to aircraft structure. The single-lap adhesive joints of epoxy composites were considered. Adhesive properties were described by surface free energy. Owens-Wendt method was used to determine surface free energy. The epoxy two-component adhesive was used to preparing the adhesive joints. Zwick/Roell 100 strength device were used to determination the shear strength of adhesive joints of epoxy composites. The strength test results showed that the highest value was obtained for adhesive joints of graphite-epoxy composite of smaller material thickness (0.48 mm). Statistical analysis of the results obtained, the study showed statistically significant differences between the values of the strength of the confidence level of 0.95. The statistical analysis of the results also showed that there are no statistical significant differences in average values of surface free energy (0.95 confidence level). It was noted that in each of the results the dispersion component of surface free energy was much greater than polar component of surface free energy.

  19. Polymer nanocarriers for dentin adhesion.

    Science.gov (United States)

    Osorio, R; Osorio, E; Medina-Castillo, A L; Toledano, M

    2014-12-01

    To obtain more durable adhesion to dentin, and to protect collagen fibrils of the dentin matrix from degradation, calcium- and phosphate-releasing particles have been incorporated into the dental adhesive procedure. The aim of the present study was to incorporate zinc-loaded polymeric nanocarriers into a dental adhesive system to facilitate inhibition of matrix metalloproteinases (MMPs)-mediated collagen degradation and to provide calcium ions for mineral deposition within the resin-dentin bonded interface. PolymP- N : Active nanoparticles (nanoMyP) were zinc-loaded through 30-minute ZnCl2 immersion and tested for bioactivity by means of 7 days' immersion in simulated body fluid solution (the Kokubo test). Zinc-loading and calcium phosphate depositions were examined by scanning and transmission electron microscopy, elemental analysis, and x-ray diffraction. Nanoparticles in ethanol solution infiltrated into phosphoric-acid-etched human dentin and Single Bond (3M/ESPE) were applied to determine whether the nanoparticles interfered with bonding. Debonded sticks were analyzed by scanning electron microscopy. A metalloproteinase collagen degradation assay was also performed in resin-infiltrated dentin with and without nanoparticles, measuring C-terminal telopeptide of type I collagen (ICTP) concentration in supernatants, after 4 wk of immersion in artificial saliva. Numerical data were analyzed by analysis of variance (ANOVA) and Student-Newman-Keuls multiple comparisons tests (p degradation. Tested nanoparticles may be incorporated into dental adhesive systems to provide the appropriate environment in which dentin MMP collagen degradation is inhibited and mineral growth can occur. © International & American Associations for Dental Research.

  20. Dentin pretreatment and adhesive temperature as affecting factors on bond strength of a universal adhesive system

    Directory of Open Access Journals (Sweden)

    Bruna Gabrielle da Silva Sutil

    Full Text Available Abstract Objectives: To evaluate the effects of dentin pretreatment and temperature on the bond strength of a universal adhesive system to dentin. Material and Methods: Ninety-six extracted non-carious human third molars were randomly divided into 12 groups (n=8 according to Scotchbond Universal Adhesive (SbU applied in self-etch (SE and etch-and-rinse (ER mode, adhesive temperature (20°C or 37°C and sodium bicarbonate or aluminum oxide air abrasion. After composite build up, bonded sticks with cross-sectional area of 1 mm2 were obtained to evaluate the microtensile bond strength (μTBS. The specimens were tested at a crosshead speed of 0.5 mm/min on a testing machine until failure. Fractured specimens were analyzed under stereomicroscope to determine the failure patterns in adhesive, cohesive (dentin or resin and mixed fractures. The microtensile bond strength data was analyzed using two-way ANOVA and Tukey's test (α=5%. Results: Interaction between treatment and temperature was statistically significant for SbU applied in self-etch technique. Both dentin treatments showed higher bond strength for ER mode, regardless of adhesive temperature. When compared to control group, sodium bicarbonate increased bond strength of SbU in SE technique. Adhesive temperature did not significantly affect the μTBS of tested groups. Predominantly, adhesive failure was observed for all groups. Conclusions: Dentin surface treatment with sodium bicarbonate air abrasion improves bond strength of SbU, irrespective of adhesive application mode, which makes this approach an alternative to increase adhesive performance of Scotchbond Universal Adhesive to dentin.

  1. Continual and molecular dynamics approaches in determining thermal properties of silicon

    Science.gov (United States)

    Mazhukin, A. V.; Koroleva, O. N.; Mazhukin, V. I.; Shapranov, A. V.

    2017-08-01

    The article discusses the use of mathematical modeling to obtain properties of silicon. The nonequilibrium heating of semiconductor proceeds with a large separation of temperatures of the current carriers from the lattice, therefore, in the problems of laser action a silicon target can be regarded as an object consisting of two interacting subsystems, electron and phonon subsystems. At the same time, for each of subsystems it is necessary to determine thermophysical, optical and thermodynamic characteristics that vary over a wide temperature range. To determine the properties of the electronic subsystem a continual approach was used, and for the phonon subsystem a molecular-dynamic approach was used. Such properties of the electron Fermi gas as electron concentration Ne(T), holes concentration Nh(T), Fermi energy EF(T), band gap Eg(T,N), carrier mobility μ(T,N), electrical conductivity σ(T,N) are determined within the framework of quantum statistics in an arbitrary degeneracy range when the temperature varies from 300K to 2000K. The most important characteristics of the phonon subsystem such as the pressure dependences of the melting temperature of silicon Tm(P) and the heat of melting Lm(P), and the temperature dependence of the heat of evaporation Lv(T) were determined. The results are compared with the experimental data.

  2. Bond durability of contemporary adhesive systems to pulp chamber dentin.

    Science.gov (United States)

    Ayar, Muhammet Kerim

    2015-12-01

    Objective : The purpose of this study was to evaluate long-term bond strengths of dentin adhesive systems, which include one-step self-etch adhesive systems (Optibond All-in-one, Kerr; Adper Prompt L-POP, 3 M ESPE), a three-step etch-and-rinse adhesive (Optibond FL, Kerr) and two-step self-etch adhesive (AdheSE Bond, Ivoclar), applied to pulp chamber dentin surfaces after 12-month water storage by using microtensile bond strength (µTBS) test. Materials and methods : Dentin adhesive systems were applied to unprepared pulp chamber dentin surfaces according to manufacturer's directions, respectively ( n = 5). After applying adhesive systems, composite buildups were done incrementally. Bond strengths to pulp chamber dentin surfaces were determined using µTBS test after water storage for 24 h and 12 month. Kruskal-Wallis analysis and Mann-Whitney U-test for pairwise comparisons were used to determine statistical differences in µTBS between the groups at a significance level of 5%. Results : There were no significant differences in µTBS between storage periods for tested adhesives regardless adhesive class. Conclusion : Bond durability of tested adhesive systems, including one-bottle self-etch adhesives with pulp chamber dentin surfaces, may be considered stable after 12-month water storage. Therefore, one-step self-etch, also called "user-friendly" adhesives may perform and traditional three-step etch-and-rinse adhesives in the long-term when used for bonding to pulp chamber dentin surfaces.

  3. Model of moisture absorption by adhesive joint

    Science.gov (United States)

    Bonilla Mora, Veronica; Mieloszyk, Magdalena; Ostachowicz, Wieslaw

    2018-01-01

    Adhesive joints offer many advantages over traditional mechanical joining systems. Nonetheless, their use is limited since they can be adversely affected by extreme temperatures and humidity conditions. Moisture contamination (even 1-3% of the sample weight) in an adhesive can alter its tensile strength and compromise the structural integrity of the joint. Moisture absorption processes can be monitored using methods based on fibre Bragg grating sensors embedded in the adhesive material. In the present paper, a finite element model of an adhesive joint between composite elements was analysed using the commercial code Abaqus™. The investigation contains two main parts: a thermal analysis and a hygro-mechanical analysis. The achieved results were verified using experimental investigation results for a sample with embedded fibre Bragg grating sensors that were applied to monitor the moisture-induced strains in the adhesive joint. The achieved numerical results show good agreement with the experimental ones for all considered analyses. The presented models can also be used for the determination of moisture content in an adhesive layer especially in a range of 1.5-2.5% of the water content.

  4. Distinct Photopolymerization Efficacy on Dentin of Self-etch Adhesives

    Science.gov (United States)

    Zhang, Y.; Wang, Y.

    2012-01-01

    The effect of application mode on polymerization effectiveness of self-etch adhesives with different pHs has rarely been studied. We applied 2 self-etch adhesives—Adper Prompt L-Pop (APLP, pH ~ 0.8) and Adper Easy-Bond (AEB, pH ~ 2.5)—to dentin with or without agitation (dynamic or static application), to investigate photopolymerization efficacy on dentin, and to understand the role of chemical interaction/reaction between adhesives and dentin. Micro-Raman spectra and imaging were acquired across the dentin/adhesive (D/A) interface. The degree of conversion (DC) of each adhesive as a function of position was calculated. SEM-EDS was used to obtain the elemental distribution along the interface. Photopolymerization efficacies of the two self-etch adhesives on dentin were apparently different. APLP exhibited decreasing DCs as the distance from the D/A interface became greater for both application modes, while the DCs for the dynamic mode were much higher than those for the static mode. As for AEB, the DCs remained almost constant across the adhesive layer and showed no significant difference between two modes. Raman spectral analysis disclosed that the chemical interaction between dentin and adhesives was responsible for the observations. We also verified this by tracking the distribution of the elements Ca and P in the adhesive layers. PMID:22736445

  5. Dry adhesives with sensing features

    International Nuclear Information System (INIS)

    Krahn, J; Menon, C

    2013-01-01

    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 cm 2 . (paper)

  6. 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.

  7. 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.

  8. Leukocyte adhesion and polarization: Role of glycosylphosphatidylinositol-anchored proteins.

    Science.gov (United States)

    Richardson, Dion D; Fernandez-Borja, Mar

    2015-01-01

    Leukocyte traffic out of the blood stream is crucial for an adequate immune response. Leukocyte extravasation is critically dependent on the binding of leukocyte integrins to their endothelial counterreceptors. This interaction enables the firm adhesion of leukocytes to the luminal side of the vascular wall and allows for leukocyte polarization, crawling and diapedesis. Leukocyte adhesion, polarization and migration requires the orchestrated regulation of integrin adhesion/de-adhesion dynamics and actin cytoskeleton rearrangements. Adhesion strength depends on conformational changes of integrin molecules (affinity) as well as the number of integrin molecules engaged at adhesion sites (valency). These two processes can be independently regulated and several molecules modulate either one or both processes. Cholesterol-rich membrane domains (lipid rafts) participate in integrin regulation and play an important role in leukocyte adhesion, polarization and motility. In particular, lipid raft-resident glycosyl-phosphatidyl-inositol-anchored proteins (GPI-APs) have been reported to regulate leukocyte adhesion, polarization and motility in both integrin-dependent and independent manners. Here, we present our recent discovery concerning the novel role of the GPI-AP prion protein (PrP) in the regulation of β1 integrin-mediated monocyte adhesion, migration and shape polarization in the context of existing literature on GPI-AP-dependent regulation of integrins.

  9. Adhesion and friction of polymer surfaces studied using scanning probe microscopy

    Science.gov (United States)

    Moon, Seung-Ho

    2003-10-01

    Scanning Probe Microscopy has been utilized to investigate the nanomechanical and nanorheological properties at the surface of polymers and polymer blends. To study the surface behavior in detail, it is critical that the SPM instrument have sufficient flexibility. A temperature stage and environmental chamber have been implemented and measurement automation has been achieved using a high-speed data acquisition system controlled by LabView(TM). Finally, new measurement protocols, "X-modulation" and "Force-Distance with X-modulation", have been developed. First measurements using those techniques have been performed for the study of aged model pressure sensitive adhesives. It has been found that the magnitude of the lateral force is so sensitive to adhesion force that X-modulation can identify qualitative differences in the strength of surface stickiness. Variations in surface adhesiveness with humidity are more obvious when the tackifier is present. A large lateral force and strongly reduced stiffness, measured using F-d with X-modulation, have been observed at high humidity for the homogeneous, hydrophilic surface of the adhesive loaded with 60wt% tackifier. These observations are consistent with a model that envisions a tackifier-enriched region near the surface. A large creep effect has also been observed for this sample, and the creep effect is magnified with temperature. These results are consistent with the hypothesis that at a hydrophilic adhesive surface water molecules may strongly alter the surface-tip interactions or modify the mechanical properties of the material nearest the surface. By changing the Z-loading velocity, dynamic adhesion behavior has been investigated. The mechanism of adhesive failure have been elucidated by comparing the velocity dependence of pull-off force and lateral force. Since this dynamic measurement is sensitive to the material composition at the surface, it has been utilized to study the surface segregation of one component at

  10. Determination of the protonation state of the Asp dyad: conventional molecular dynamics versus thermodynamic integration.

    Science.gov (United States)

    Huang, Jinfeng; Zhu, Yali; Sun, Bin; Yao, Yuan; Liu, Junjun

    2016-03-01

    The protonation state of the Asp dyad is important as it can reveal enzymatic mechanisms, and the information this provides can be used in the development of drugs for proteins such as memapsin 2 (BACE-1), HIV-1 protease, and rennin. Conventional molecular dynamics (MD) simulations have been successfully used to determine the preferred protonation state of the Asp dyad. In the present work, we demonstrate that the results obtained from conventional MD simulations can be greatly influenced by the particular force field applied or the values used for control parameters. In principle, free-energy changes between possible protonation states can be used to determine the protonation state. We show that protonation state prediction by the thermodynamic integration (TI) method is insensitive to force field version or to the cutoff for calculating nonbonded interactions (a control parameter). In the present study, the protonation state of the Asp dyad predicted by TI calculations was the same regardless of the force field and cutoff value applied. Contrary to the intuition that conventional MD is more efficient, our results clearly show that the TI method is actually more efficient and more reliable for determining the protonation state of the Asp dyad.

  11. Dynamic PET scanning and compartmental model analysis to determine cellular level radiotracer distribution in vivo

    International Nuclear Information System (INIS)

    Smith, G.T.; Hubner, K.F.; Goodman, M.M.; Stubbs, J.B.

    1992-01-01

    Positron emission tomography (PET) has been used to measure tissue radiotracer concentration in vivo. Radiochemical distribution can be determined with compartmental model analysis. A two compartment model describes the kinetics of N-13 ammonia ( 13 NH 3 ) in the myocardium. The model consists of a vascular space, Q 1 and a space for 13 NH 3 bound within the tissue, Q 2 . Differential equations for the model can be written: X(t) = AX(t) + BU( t), Y(t)= CX(t)+ DU(t) (1) where X(t) is a column vector [Q 1 (t); Q 2 (t)], U(t) is the arterial input activity measured from the left ventricular blood pool, and Y(t) is the measured tissue activity using PET. Matrices A, B, C, and D are dependent on physiological parameters describing the kinetics of 13 NH 3 in the myocardium. Estimated parameter matrices in Equation 1 have been validated in dog experiments by measuring myocardial perfusion with dynamic PET scanning and intravenous injection of 13 NH 3 . Tracer concentrations for each compartment can be calculated by direct integration of Equation 1. If the cellular level distribution of each compartment is known, the concentration of tracer within the intracellular and extracellular space can be determined. Applications of this type of modeling include parameter estimation for measurement of physiological processes, organ level dosimetry, and determination of cellular radiotracer distribution

  12. An elemental mercury diffusion coefficient for natural waters determined by molecular dynamics simulation.

    Science.gov (United States)

    Kuss, Joachim; Holzmann, Jörg; Ludwig, Ralf

    2009-05-01

    Mercury is a priority pollutant as its mobility between the hydrosphere and the atmosphere threatens the biosphere globally. The air-water gas transfer of elemental mercury (Hg0) is controlled by its diffusion through the water-side boundary layer and thus by its diffusion coefficient, D(Hg), the value of which, however, has not been established. Here, the diffusion of Hg0 in water was modeled by molecular dynamics (MD) simulation and the diffusion coefficient subsequently determined. Therefore the movement of either Hg(0) or xenon and 1000 model water molecules (TIP4P-Ew) were traced for time spans of 50 ns. The modeled D(Xe) of the monatomic noble gas agreed well with measured data; thus, MD simulation was assumed to be a reliable approach to determine D(Hg) for monatomic Hg(0) as well. Accordingly, Hg(0) diffusion was then simulated for freshwater and seawater, and the data were well-described by the equation of Eyring. The activation energies for the diffusion of Hg0 in freshwater was 17.0 kJ mol(-1) and in seawater 17.8 kJ mol(-1). The newly determined D(Hg) is clearly lower than the one previously used for an oceanic mercury budget. Thus, its incorporation into the model should lead to lower estimates of global ocean mercury emissions.

  13. A theoretical framework for determining cerebral vascular function and heterogeneity from dynamic susceptibility contrast MRI.

    Science.gov (United States)

    Digernes, Ingrid; Bjørnerud, Atle; Vatnehol, Svein Are S; Løvland, Grete; Courivaud, Frédéric; Vik-Mo, Einar; Meling, Torstein R; Emblem, Kyrre E

    2017-06-01

    Mapping the complex heterogeneity of vascular tissue in the brain is important for understanding cerebrovascular disease. In this translational study, we build on previous work using vessel architectural imaging (VAI) and present a theoretical framework for determining cerebral vascular function and heterogeneity from dynamic susceptibility contrast magnetic resonance imaging (MRI). Our tissue model covers realistic structural architectures for vessel branching and orientations, as well as a range of hemodynamic scenarios for blood flow, capillary transit times and oxygenation. In a typical image voxel, our findings show that the apparent MRI relaxation rates are independent of the mean vessel orientation and that the vortex area, a VAI-based parameter, is determined by the relative oxygen saturation level and the vessel branching of the tissue. Finally, in both simulated and patient data, we show that the relative distributions of the vortex area parameter as a function of capillary transit times show unique characteristics in normal-appearing white and gray matter tissue, whereas tumour-voxels in comparison display a heterogeneous distribution. Collectively, our study presents a comprehensive framework that may serve as a roadmap for in vivo and per-voxel determination of vascular status and heterogeneity in cerebral tissue.

  14. Inquiring the niche determinants of social media websites in dynamically mobile hypercompetitive communication era

    Directory of Open Access Journals (Sweden)

    Chih-Cheng Huang

    2016-03-01

    Full Text Available This research cross-employs the information communication distribution transaction and analytic network process models to effectively institute the hierarchical evaluated model and utilizes, in specific, fuzzy theory and the grey relation analysis approaches of multiple criteria decision-making methodology into the weight measurements of expert’s questionnaires from three analytical perspectives (user’s satisfaction, corporate commitment, and social trust of relationship quality in order to explore the niche determinants of the social media websites in the contemporarily hypercompetitive and dynamic online era. Consequently, as for the measured consequences after a series of complicated and systematical calculations, the most valuable findings in this research are (1 the technological interfaces of social media websites is a positive niche in the dynamically mobile hypercompetitive communication era and (2 the “social media websites” is in a position of becoming one of the social media mainstreams in the online technology field based on the measured weights from the detailed survey data collected from experts in this research.

  15. 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.

  16. DNA thermodynamic stability and supercoil dynamics determine the gene expression program during the bacterial growth cycle.

    Science.gov (United States)

    Sobetzko, Patrick; Glinkowska, Monika; Travers, Andrew; Muskhelishvili, Georgi

    2013-07-01

    The chromosomal DNA polymer constituting the cellular genetic material is primarily a device for coding information. Whilst the gene sequences comprise the digital (discontinuous) linear code, physiological alterations of the DNA superhelical density generate in addition analog (continuous) three-dimensional information essential for regulation of both chromosome compaction and gene expression. Insight into the relationship between the DNA analog information and the digital linear code is of fundamental importance for understanding genetic regulation. Our previous study in the model organism Escherichia coli suggested that the chromosomal gene order and a spatiotemporal gradient of DNA superhelicity associated with DNA replication determine the growth phase-dependent gene transcription. In this study we reveal a general gradient of DNA thermodynamic stability correlated with the polarity of chromosomal replication and manifest in the spatiotemporal pattern of gene transcription during the bacterial growth cycle. Furthermore, by integrating the physical and dynamic features of the transcribed sequences with their functional content we identify spatiotemporal domains of gene expression encompassing different functions. We thus provide both an insight into the organisational principle of the bacterial growth program and a novel holistic methodology for exploring chromosomal dynamics.

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

    Energy Technology Data Exchange (ETDEWEB)

    Afrooz, A. R. M. Nabiul [The University of Texas, Civil, Architectural and Environmental Engineering (United States); Hussain, Saber M. [Wright-Patterson AFB, Human Effectiveness Directorate, 711th Human Performance Wing, Air Force Research Laboratory (United States); Saleh, Navid B., E-mail: navid.saleh@utexas.edu [The University of Texas, Civil, Architectural and Environmental Engineering (United States)

    2014-12-15

    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.

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

    International Nuclear Information System (INIS)

    Afrooz, A. R. M. Nabiul; Hussain, Saber M.; Saleh, Navid B.

    2014-01-01

    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

  19. Protein diffusion coefficients determined by macroscopic-gradient Rayleigh interferometry and dynamic light scattering.

    Science.gov (United States)

    Annunziata, Onofrio; Buzatu, Daniela; Albright, John G

    2005-12-20

    Dynamic light scattering (DLS) is extensively used for measuring macromolecule diffusion coefficients. Contrary to classical techniques based on macroscopic concentration gradients, DLS probes microscopic fluctuations in concentration. DLS accuracy and its concordance with macroscopic-gradient techniques remains an outstanding important issue. We measured lysozyme diffusion coefficients in aqueous salt using both DLS and Rayleigh interferometry, a highly accurate macroscopic-gradient technique. The precision of our results is unprecedented. We find that our DLS values were systematically 2% higher than interferometry values. We believe that our interferometric measurements have produced the most accurate diffusion data ever reported for a protein, providing a new standard for quality control of DLS measurements. Furthermore, by interferometry, we have determined the whole diffusion coefficient matrix required for rigorously describing lysozyme-salt coupled diffusion. For the first time, we experimentally demonstrate that DLS does not provide the protein diffusion coefficient but one eigenvalue of the diffusion coefficient matrix.

  20. A Numerical Approach to Determine Attitude Dynamics of Floating Bodies with Irregular Configurations

    Directory of Open Access Journals (Sweden)

    Jiann-Lin Chen

    2014-07-01

    Full Text Available This study acquires the attitude dynamics of floating bodies with irregular configurations using an effective computational model, which has been validated theoretically and verified by experiments. By comparison a correlation formula was described to predict inclinations for the floating slender body imitating an excise torpedo. Thereafter a computational model was developed to account for bodies with attitudes in more general situations. For demonstration, a submersible was simulated to reveal that the inclinations vary abruptly around certain longitudinal locations of center of gravity. The property variations during water ingress assumption were presented. Similar to the virtue tank, an innovative concept of building the numerical data base for a specific floating body has been proposed, by which the position of its center of gravity can be obtained by interpolation from attitude data in tables as determined by the present computational model.

  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

    . 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 goes back...

  2. The surface chemistry determines the spatio-temporal interaction dynamics of quantum dots in atherosclerotic lesions.

    Science.gov (United States)

    Uhl, Bernd; Hirn, Stephanie; Mildner, Karina; Coletti, Raffaele; Massberg, Steffen; Reichel, Christoph A; Rehberg, Markus; Zeuschner, Dagmar; Krombach, Fritz

    2018-03-01

    To optimize the design of nanoparticles for diagnosis or therapy of vascular diseases, it is mandatory to characterize the determinants of nano-bio interactions in vascular lesions. Using ex vivo and in vivo microscopy, we analyzed the interactive behavior of quantum dots with different surface functionalizations in atherosclerotic lesions of ApoE-deficient mice. We demonstrate that quantum dots with different surface functionalizations exhibit specific interactive behaviors with distinct molecular and cellular components of the injured vessel wall. Moreover, we show a role for fibrinogen in the regulation of the spatio-temporal interaction dynamics in atherosclerotic lesions. Our findings emphasize the relevance of surface chemistry-driven nano-bio interactions on the differential in vivo behavior of nanoparticles in diseased tissue.

  3. 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.

  4. In vitro phosphorylation of the focal adhesion targeting domain of focal adhesion kinase by Src kinase.

    Science.gov (United States)

    Cable, Jennifer; Prutzman, Kirk; Gunawardena, Harsha P; Schaller, Michael D; Chen, Xian; Campbell, Sharon L

    2012-03-20

    Focal adhesion kinase (FAK), a key regulator of cell adhesion and migration, is overexpressed in many types of cancer. The C-terminal focal adhesion targeting (FAT) domain of FAK is necessary for proper localization of FAK to focal adhesions and subsequent activation. Phosphorylation of Y926 in the FAT domain by the tyrosine kinase Src has been shown to promote metastasis and invasion in vivo by linking the FAT domain to the MAPK pathway via its interaction with growth factor receptor-bound protein 2. Several groups have reported that inherent conformational dynamics in the FAT domain likely regulate phosphorylation of Y926; however, what regulates these dynamics is unknown. In this paper, we demonstrate that there are two sites of in vitro Src-mediated phosphorylation in the FAT domain: Y926, which has been shown to affect FAK function in vivo, and Y1008, which has no known biological role. The phosphorylation of these two tyrosine residues is pH-dependent, but this does not reflect the pH dependence of Src kinase activity. Circular dichroism and nuclear magnetic resonance data indicate that the stability and conformational dynamics of the FAT domain are sensitive to changes in pH over a physiological pH range. In particular, regions of the FAT domain previously shown to regulate phosphorylation of Y926 as well as regions near Y1008 show pH-dependent dynamics on the microsecond to millisecond time scale.

  5. Population dynamics can be more important than physiological limits for determining range shifts under climate change.

    Science.gov (United States)

    Fordham, Damien A; Mellin, Camille; Russell, Bayden D; Akçakaya, Reşit H; Bradshaw, Corey J A; Aiello-Lammens, Matthew E; Caley, Julian M; Connell, Sean D; Mayfield, Stephen; Shepherd, Scoresby A; Brook, Barry W

    2013-10-01

    Evidence is accumulating that species' responses to climate changes are best predicted by modelling the interaction of physiological limits, biotic processes and the effects of dispersal-limitation. Using commercially harvested blacklip (Haliotis rubra) and greenlip abalone (Haliotis laevigata) as case studies, we determine the relative importance of accounting for interactions among physiology, metapopulation dynamics and exploitation in predictions of range (geographical occupancy) and abundance (spatially explicit density) under various climate change scenarios. Traditional correlative ecological niche models (ENM) predict that climate change will benefit the commercial exploitation of abalone by promoting increased abundances without any reduction in range size. However, models that account simultaneously for demographic processes and physiological responses to climate-related factors result in future (and present) estimates of area of occupancy (AOO) and abundance that differ from those generated by ENMs alone. Range expansion and population growth are unlikely for blacklip abalone because of important interactions between climate-dependent mortality and metapopulation processes; in contrast, greenlip abalone should increase in abundance despite a contraction in AOO. The strongly non-linear relationship between abalone population size and AOO has important ramifications for the use of ENM predictions that rely on metrics describing change in habitat area as proxies for extinction risk. These results show that predicting species' responses to climate change often require physiological information to understand climatic range determinants, and a metapopulation model that can make full use of this data to more realistically account for processes such as local extirpation, demographic rescue, source-sink dynamics and dispersal-limitation. © 2013 John Wiley & Sons Ltd.

  6. 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

  7. What Determines Water Temperature Dynamics in the San Francisco Bay-Delta System?

    Science.gov (United States)

    Vroom, J.; van der Wegen, M.; Martyr-Koller, R. C.; Lucas, L. V.

    2017-11-01

    Water temperature is an important factor determining estuarine species habitat conditions. Water temperature is mainly governed by advection (e.g., from rivers) and atmospheric exchange processes varying strongly over time (day-night, seasonally) and the spatial domain. On a long time scale, climate change will impact water temperature in estuarine systems due to changes in river flow regimes, air temperature, and sea level rise. To determine which factors govern estuarine water temperature and its sensitivity to changes in its forcing, we developed a process-based numerical model (Delft3D Flexible Mesh) and applied it to a well-monitored estuarine system (the San Francisco Estuary) for validation. The process-based approach allows for detailed process description and a physics-based analysis of governing processes. The model was calibrated for water year 2011 and incorporated 3-D hydrodynamics, salinity intrusion, water temperature dynamics, and atmospheric coupling. Results show significant skill in reproducing temperature observations on daily, seasonal, and yearly time scales. In North San Francisco Bay, thermal stratification is present, enhanced by salinity stratification. The temperature of the upstream, fresh water Delta area is captured well in 2-D mode, although locally—on a small scale—vertical processes (e.g., stratification) may be important. The impact of upstream river temperature and discharge and atmospheric forcing on water temperatures differs throughout the Delta, possibly depending on dispersion and residence times. Our modeling effort provides a sound basis for future modeling studies including climate change impact on water temperature and associated ecological modeling, e.g., clam and fish habitat and phytoplankton dynamics.

  8. Determinação por espectroscopia nas regiões MIR/NIR do teor de NCO em adesivos poliuretânicos Determination of NCO contents in polyurethane adhesives using MIR/NIR spectroscopies

    Directory of Open Access Journals (Sweden)

    Sandra H. S. Siqueira

    2008-03-01

    Full Text Available Adesivos poliuretânicos (AD-PU, contendo teor conhecido de isocianato (NCO, foram preparados, nos laboratórios da Rohm and Haas Química Ltda, e amostras foram usadas para a elaboração de uma curva analítica, visando à determinação do teor de NCO por espectroscopia no infravermelho médio (MIR e próximo (NIR. Os valores de % NCO, obtidos pelo método analítico por via úmida para amostras retiradas durante o processo de fabricação, foram usados como referência. A banda FT-IR escolhida na região MIR foi: 2270 cm-1 (banda analítica. Na região NIR, foi usada uma banda relativa, A4063/A4348. Em ambos os métodos, MIR e NIR, a intensidade das bandas escolhidas e o teor de NCO, obtidos a partir da análise via úmida, foram utilizados para construção de curvas que apresentaram boas correlações lineares (MIR - R = 0,995 e NIR - R = 0,961, que possibilitarão a determinação dos teores de NCO em misturas de composição semelhante.Polyurethane adhesives reference samples (AD-PU with known contents of isocyanate (NCO have been prepared in Rohm and Haas to elaborate analytical curves for determination of NCO content, using MIR and NIR analysis. Wet chemical values were used to determine the content of NCO in the AD-PU samples obtained during the process. The MIR analytical band used was 2270 cm-1 and the NIR relative band was A4063/A4348. Data of absorbance intensity and NCO contents obtained from wet chemical analysis were used to elaborate the analytical curves (MIR - R = 0.995 and NIR - R = 0.961 which should allow for the determination of NCO content in adhesive samples of similar composition.

  9. Adhesive performance of precoated brackets after expiration.

    Science.gov (United States)

    Cloud, Cayce C; Trojan, Terry M; Suliman, Sam N; Tantbirojn, Daranee; Versluis, Antheunis

    2016-03-01

    To evaluate adhesive performance in terms of debonding forces of precoated metal and ceramic brackets 4 years after expiration. Buccal and lingual surfaces of embedded extracted maxillary premolars were etched with 34% Tooth Conditioner Gel (Dentsply Caulk, Milford, Del), rinsed, and dried. Transbond MIP (3M Unitek, Monrovia, Calif) was applied prior to placing adhesive precoated brackets (APC II Victory stainless steel and APC Plus Clarity ceramic brackets, 3M Unitek). The preexpiration brackets had 29-35 months before, and the postexpiration brackets were 45-52 months past, their expiration dates. Sample size was 17-21 per group. Debonding forces were determined by subjecting the bonded brackets to a shear force in a universal testing machine. Debonding forces were compared using two-way ANOVA. Debonded surfaces were examined under a stereomicroscope to determine failure modes, which were compared using the chi-square test. No statistically significant difference was found in debonding forces (P  =  .8581) or failure modes (P  =  .4538) between expired and unexpired brackets. Metal brackets required statistically significantly higher debonding forces than did ceramic brackets (P  =  .0001). For both expired and unexpired brackets, failure modes were mostly cohesive in the adhesive layer for ceramic brackets, and mixed between adhesive and cohesive failure in the adhesive layer for metal brackets. Adhesive precoated brackets did not have any reduction in enamel-adhesion properties up to 4 years after their expiration date. Extended shelf life testing for precoated dental brackets may be worth considering.

  10. Management of low adhesion on railway tracks in European countries

    DEFF Research Database (Denmark)

    Thommesen, Jacob; Duijm, Nijs Jan; Andersen, Henning Boje

    This report presents approaches of selected European countries to the management of low adhesion problems. It spans approaches addressing different levels of the problem, including preventive measures focusing on the tasks aimed at removing or reducing low adhesion, mitigative technical measures...... aimed at improving wheel performance in low adhesion conditions, as well as mitigative measures for driving and operating trains under these conditions. The report thus spans measures that are often managed by different organisations, mainly infrastructure managers and train operators. The report...... focuses on management of low adhesion and will not go into detail with the characteristics and generation of the low adhesion layer but will touch on this only to the extent that this determines or is directly linked with the specific low adhesion measures taken. Neither will the report go into detail...

  11. What Physiological Changes and Cerebral Traces Tell Us about Adhesion to Fiction During Theater-Watching?

    Science.gov (United States)

    Metz-Lutz, Marie-Noëlle; Bressan, Yannick; Heider, Nathalie; Otzenberger, Hélène

    2010-01-01

    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, emphasized 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 (fMRI) 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 posterior superior temporal sulcus, 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.

  12. Structural basis of the tensile strength of protein complexes mediating cell adhesion

    Science.gov (United States)

    Bayas, Marco Vinicio

    This study explores the behaviour of adhesive complexes of cell adhesion molecules undergoing forced detachment. Molecular-forces measurements combined with Steered Molecular Dynamic (SMD) simulations were used to investigate the mechanical response of the CD2 C58 and hemophilic C-cadherin bonds. The CD2-CD58 adhesive complex, important for the adaptive immune response, contains several salt-bridges in the adhesive interface. SMD simulations showed that these inter-protein salt bridges contribute independently to the tensile strength of the complex. Consistent with this, force measurements with the Surface Force Apparatus (SFA) demonstrated that the elimination of single salt bridges weakens the bond. The corresponding loss in adhesion energy of the CD2-CD58 complex correlates with the importance of the salt bridges observed in the simulations. These findings correlate closely with the effect of the elimination of single salt bridges observed in cell aggregation assays and binding measurements. On the other hand, the hemophilic C-cadherin interaction determines specific cell-cell adhesion during development in Xenopus laevis . Single molecule force spectroscopy was used to characterize the multiple bound states between C-cadherin ectodomains. The experiments showed two short-lived bound states associated with the two outermost ectodomains and two long-lived states associated with the full ectodomain. It is likely that the two short-lived states are involved in the specificity of the interaction since previous studies showed that the corresponding states in E-cadherin have different lifetimes. In addition, SMD simulations of the forced dissociation of the strand dieter of C-cadherin suggested a mechanism for the specificity of cadherin interactions.

  13. 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.

  14. 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.

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

    Science.gov (United States)

    Gamble, Tony; Greenbaum, Eli; Jackman, Todd R; Russell, Anthony P; Bauer, Aaron M

    2012-01-01

    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.

  16. APPLICATION OF VEHICLE DYNAMIC MODELING IN UAVS FOR PRECISE DETERMINATION OF EXTERIOR ORIENTATION

    Directory of Open Access Journals (Sweden)

    M. Khaghani

    2016-06-01

    Full Text Available 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

  17. Adhesive particle shielding

    Science.gov (United States)

    Klebanoff, Leonard Elliott [Dublin, CA; Rader, Daniel John [Albuquerque, NM; Walton, Christopher [Berkeley, CA; Folta, James [Livermore, CA

    2009-01-06

    An efficient device for capturing fast moving particles has an adhesive particle shield that includes (i) a mounting panel and (ii) a film that is attached to the mounting panel wherein the outer surface of the film has an adhesive coating disposed thereon to capture particles contacting the outer surface. The shield can be employed to maintain a substantially particle free environment such as in photolithographic systems having critical surfaces, such as wafers, masks, and optics and in the tools used to make these components, that are sensitive to particle contamination. The shield can be portable to be positioned in hard-to-reach areas of a photolithography machine. The adhesive particle shield can incorporate cooling means to attract particles via the thermophoresis effect.

  18. Electrically Conductive Epoxy Adhesives

    Directory of Open Access Journals (Sweden)

    Lan Bai

    2011-02-01

    Full Text Available Conductive adhesives are widely used in electronic packaging applications such as die attachment and solderless interconnections, component repair, display interconnections, and heat dissipation. The effects of film thickness as functions of filler volume fraction, conductive filler size, shape, as well as uncured adhesive matrix viscosity on the electrical conduction behavior of epoxy-based adhesives are presented in this work. For this purpose, epoxy-based adhesives were prepared using conductive fillers of different size, shape, and types, including Ni powder, flakes, and filaments, Ag powder, and Cu powder. The filaments were 20 μm in diameter, and 160 or 260 μm in length. HCl and H3PO4 acid solutions were used to etch and remove the surface oxide layers from the fillers. The plane resistance of filled adhesive films was measured using the four-point method. In all cases of conductive filler addition, the planar resistivity levels for the composite adhesive films increased when the film thickness was reduced. The shape of resistivity-thickness curves was negative exponential decaying type and was modeled using a mathematical relation. The relationships between the conductive film resistivities and the filler volume fractions were also derived mathematically based on the experimental data. Thus, the effects of surface treatment of filler particles, the type, size, shape of fillers, and the uncured epoxy viscosity could be included empirically by using these mathematical relations based on the experimental data. By utilizing the relations we proposed to model thickness-dependent and volume fraction-dependent conduction behaviors separately, we were able to describe the combined and coupled volume fraction-film thickness relationship mathematically based on our experimental data.

  19. Evaluation of bond strength and thickness of adhesive layer according to the techniques of applying adhesives in composite resin restorations.

    Science.gov (United States)

    de Menezes, Fernando Carlos Hueb; da Silva, Stella Borges; Valentino, Thiago Assunção; Oliveira, Maria Angélica Hueb de Menezes; Rastelli, Alessandra Nara de Souza; Conçalves, Luciano de Souza

    2013-01-01

    Adhesive restorations have increasingly been used in dentistry, and the adhesive system application technique may determine the success of the restorative procedure. The aim of this study was to evaluate the influence of the application technique of two adhesive systems (Clearfil SE Bond and Adper Scotchbond MultiPurpose) on the bond strength and adhesive layer of composite resin restorations. Eight human third molars were selected and prepared with Class I occlusal cavities. The teeth were restored with composite using various application techniques for both adhesives, according to the following groups (n = 10): group 1 (control), systems were applied and adhesive was immediately light activated for 20 seconds without removing excesses; group 2, excess adhesive was removed with a gentle jet of air for 5 seconds; group 3, excess was removed with a dry microbrushtype device; and group 4, a gentle jet of air was applied after the microbrush and then light activation was performed. After this, the teeth were submitted to microtensile testing. For the two systems tested, no statistical differences were observed between groups 1 and 2. Groups 3 and 4 presented higher bond strength values compared with the other studied groups, allowing the conclusion that excess adhesive removal with a dry microbrush could improve bond strength in composite restorations. Predominance of adhesive fracture and thicker adhesive layer were observed via scanning electron microscopy (SEM) in groups 1 and 2. For groups 3 and 4, a mixed failure pattern and thinner adhesive layer were verified. Clinicians should be aware that excess adhesive may negatively affect bond strength, whereas a thin, uniform adhesive layer appears to be favorable.

  20. Efficiency of sirolimus in prevention of adhesions around vascular

    African Journals Online (AJOL)

    muhip kanko

    sirolimus) was applied (in powder form) on the grafts of the study group. Four weeks later a laparotomy was done and the adhesions developed were evaluated. Results: In the study group the adhesions were determined to be fewer in number and ...

  1. Natural and bio-inspired underwater adhesives: Current progress and new perspectives

    Science.gov (United States)

    Cui, Mengkui; Ren, Susu; Wei, Shicao; Sun, Chengjun; Zhong, Chao

    2017-11-01

    Many marine organisms harness diverse protein molecules as underwater adhesives to achieve strong and robust interfacial adhesion under dynamic and turbulent environments. Natural underwater adhesion phenomena thus provide inspiration for engineering adhesive materials that can perform in water or high-moisture settings for biomedical and industrial applications. Here we review examples of biological adhesives to show the molecular features of natural adhesives and discuss how such knowledge serves as a heuristic guideline for the rational design of biologically inspired underwater adhesives. In view of future bio-inspired research, we propose several potential opportunities, either in improving upon current L-3, 4-dihydroxyphenylalanine-based and coacervates-enabled adhesives with new features or engineering conceptually new types of adhesives that recapitulate important characteristics of biological adhesives. We underline the importance of viewing natural adhesives as dynamic materials, which owe their outstanding performance to the cellular coordination of protein expression, delivery, deposition, assembly, and curing of corresponding components with spatiotemporal control. We envision that the emerging synthetic biology techniques will provide great opportunities for advancing both fundamental and application aspects of underwater adhesives.

  2. Switchable bio-inspired adhesives

    Science.gov (United States)

    Kroner, Elmar

    2015-03-01

    Geckos have astonishing climbing abilities. They can adhere to almost any surface and can run on walls and even stick to ceilings. The extraordinary adhesion performance is caused by a combination of a complex surface pattern on their toes and the biomechanics of its movement. These biological dry adhesives have been intensely investigated during recent years because of the unique combination of adhesive properties. They provide high adhesion, allow for easy detachment, can be removed residue-free, and have self-cleaning properties. Many aspects have been successfully mimicked, leading to artificial, bio-inspired, patterned dry adhesives, and were addressed and in some aspects they even outperform the adhesion capabilities of geckos. However, designing artificial patterned adhesion systems with switchable adhesion remains a big challenge; the gecko's adhesion system is based on a complex hierarchical surface structure and on advanced biomechanics, which are both difficult to mimic. In this paper, two approaches are presented to achieve switchable adhesion. The first approach is based on a patterned polydimethylsiloxane (PDMS) polymer, where adhesion can be switched on and off by applying a low and a high compressive preload. The switch in adhesion is caused by a reversible mechanical instability of the adhesive silicone structures. The second approach is based on a composite material consisting of a Nickel- Titanium (NiTi) shape memory alloy and a patterned adhesive PDMS layer. The NiTi alloy is trained to change its surface topography as a function of temperature, which results in a change of the contact area and of alignment of the adhesive pattern towards a substrate, leading to switchable adhesion. These examples show that the unique properties of bio-inspired adhesives can be greatly improved by new concepts such as mechanical instability or by the use of active materials which react to external stimuli.

  3. Micromechanical and surface adhesive properties of single saccharomyces cerevisiae cells

    Science.gov (United States)

    Farzi, Bahman; Cetinkaya, Cetin

    2017-09-01

    The adhesion and mechanical properties of a biological cell (e.g. cell membrane elasticity and adhesiveness) are often strong indicators for the state of its health. Many existing techniques for determining mechanical properties of cells require direct physical contact with a single cell or a group of cells. Physical contact with the cell can trigger complex mechanotransduction mechanisms, leading to cellular responses, and consequently interfering with measurement accuracy. In the current work, based on ultrasonic excitation and interferometric (optical) motion detection, a non-contact method for characterizing the adhesion and mechanical properties of single cells is presented. It is experimentally demonstrated that the rocking (rigid body) motion and internal vibrational resonance frequencies of a single saccharomyces cerevisiae (SC) (baker’s yeast) cell can be acquired with the current approach, and the Young’s modulus and surface tension of the cell membrane as well as surface adhesion energy can be extracted from the values of these acquired resonance frequencies. The detected resonance frequency ranges for single SC cells include a rocking (rigid body) frequency of 330  ±  70 kHz and two breathing resonance frequencies of 1.53  ±  0.12 and 2.02  ±  0.31 MHz. Based on these values, the average work-of-adhesion of SC cells on a silicon substrate in aqueous medium is extracted, for the first time, as WASC-Si=16.2+/- 3.8 mJ {{m}-2} . Similarly, the surface tension and the Young’s modulus of the SC cell wall are predicted as {{σ }SC}=0.16+/- 0.02 N {{m}-1} and {{E}SC}= 9.20  ±  2.80 MPa, respectively. These results are compared to those reported in the literature by utilizing various methods, and good agreements are found. The current approach eliminates the measurement inaccuracies associated with the physical contact. Exciting and detecting cell dynamics at micro-second time-scales is significantly faster than the

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

    Science.gov (United States)

    Purtov, Julia; Frensemeier, Mareike; Kroner, Elmar

    2015-11-04

    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.

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

    Science.gov (United States)

    Bidder, Owen R; Qasem, Lama A; Wilson, Rory P

    2012-01-01

    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. 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. 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 for terrestrial animals, without the need for

  6. 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

  7. Determining lead, cadmium and mercury in cosmetics using sweeping via dynamic chelation by capillary electrophoresis.

    Science.gov (United States)

    Chen, Kuan-Ling; Jiang, Shiuh-Jen; Chen, Yen-Ling

    2017-03-01

    International limits have been established for metal impurities in cosmetics to prevent overexposure to heavy metal ions. Sweeping via dynamic chelation was developed using capillary electrophoresis to analyze lead (Pb), cadmium (Cd) and mercury (Hg) impurities in cosmetics. The sweeping via dynamic chelation mechanism involves a large volume of metal ions being swept by a small quantity of chelating agents that were electrokinetically injected into the capillary to chelate metal ions and increase the detection sensitivity. The optimized conditions were as follows: Firstly, the capillary was rinsed by a 0.6 mM TTAB solution to reverse the EOF. The sample solution, which was diluted using 25 mM ammonium acetate (pH 6.0), was injected into the capillary using a pressure of 3.5 psi for 99.9 s. Then, EDTA was injected at -25 kV for 1 min from the EDTA buffer (25 mM ammonium acetate containing 0.6 mM TTAB and 5 mM EDTA), and the metal ions were swept and stacked simultaneously. Finally, the separation was performed at -20 kV using a separation buffer (100 mM ammonium acetate (pH 6.0)). A small quantity of chelating agents introduced into the capillary could yield 33-, 50- and 100-fold detection improvements for Pb, Cd and Hg, respectively, more sensitive than conventional capillary zone electrophoresis. Correlation coefficients greater than 0.998 indicated that this method exhibited good linearity. The relative standard deviation and relative error were less than 8.7%, indicating high precision and accuracy. The recovery value of the homemade lotion, which was employed to simulate the real sample matrix, was 93-104%, which indicated that the sample matrix does not affect the quantitative results. Finally, commercial cosmetics were employed to demonstrate the feasibility of the method to determine Pb, Cd and Hg without complicated sample pretreatment. Graphical Abstract The procedure of analyzing metal ions in cosmetics by sweeping via dynamic chelation.

  8. Comparison of enamel bond fatigue durability between universal adhesives and two-step self-etch adhesives: Effect of phosphoric acid pre-etching.

    Science.gov (United States)

    Suda, Shunichi; Tsujimoto, Akimasa; Barkmeier, Wayne W; Nojiri, Kie; Nagura, Yuko; Takamizawa, Toshiki; Latta, Mark A; Miyazaki, Masashi

    2017-11-23

    The effect of phosphoric acid pre-etching on enamel bond fatigue durability of universal adhesives and two-step self-etch adhesives was investigated. Four universal adhesives and three two-step self-etch adhesives were used. The initial shear bond strengths and shear fatigue strengths to enamel with and without phosphoric acid pre-etching using the adhesives were determined. SEM observations were also conducted. Phosphoric acid pre-etching of enamel was found to increase the bond fatigue durability of universal adhesives, but its effect on two-step self-etch adhesives was material-dependent. In addition, some universal adhesives with phosphoric acid preetching showed similar bond fatigue durability to the two-step self-etch adhesives, although the bond fatigue durability of universal adhesives in self-etch mode was lower than that of the two-step self-etch adhesives. Phosphoric acid pre-etching enhances enamel bond fatigue durability of universal adhesives, but the effect of phosphoric acid pre-etching on the bond fatigue durability of two-step self-etch adhesives was material-dependent.

  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. an Adhesive Patch

    Directory of Open Access Journals (Sweden)

    S. Mojtaba Taghizadeh

    2013-01-01

    Full Text Available Drug-in-adhesive transdermal drug delivery systems  TDDSs containing stimulants, termed as energetic substances, such as caffeine and pantothenic acid, were studied. Caffeine is a white crystalline substance and a stimulant to central nervous system. In humans, caffeine acts as a central nervous system stimulant, temporarily warding off drowsiness and restoring alertness. Pantothenic acid, also recognized as vitamin B5, is a water-soluble vitamin. For many animals, pantothenic acid is an essential nutrient. Animals require pantothenic acid to synthesize and metabolize proteins, carbohydrates and fats. For this purpose caffeine and pantothenic acid were  used  as  drug  components with  6.32%  and  1.12%  loadings,  in  different functional and non-functional acrylic pressure sensitive adhesives (PSAs of 52.89%, respectively. Ethylene glycol as a chemical enhancer was used in all TDDSs with 39.67%. The effect of PSAs  type on  in vitro  release and adhesion properties  (peel strength and tack values from drug delivery devices were evaluated. It was found that TDDS containing -COOH functional PSA showed  the  lowest steady state fux. The adhesion properties of the samples were improved by addition of functional acrylic PSA in formulations.

  11. Syndecans: synergistic activators of cell adhesion

    DEFF Research Database (Denmark)

    Woods, A; Couchman, J R

    1998-01-01

    Cell-surface proteoglycans participate in cell adhesion, growth-factor signalling, lipase activity and anticoagulation. Until recently, only the roles of the glycosaminoglycan chains were investigated. Now, with molecular characterization of several core proteins, the roles of each individual...... proteoglycan species in cellular signalling pathways are being determined. This review describes some of the recent advances in our understanding of the major transmembrane group of heparan sulfate proteoglycans, the syndecans, including evidence that they play an important role as accessory signalling...... molecules modulating integrin-based adhesion....

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

    Indian Academy of Sciences (India)

    Abstract. 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 z = 3.32 Å. It was observed ...

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

    Indian Academy of Sciences (India)

    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 ...

  14. From genotypes to phenotypes: classification of the tumour profiles for different variants of the cadherin adhesion pathway

    International Nuclear Information System (INIS)

    Ramis-Conde, Ignacio; Drasdo, Dirk

    2012-01-01

    The E-cadherin adhesive profile expressed by a tumour is a characterization of the intracellular and intercellular protein interactions that control cell–cell adhesion. Within the intracellular proteins that determine the tumour adhesive profile, Src and PI3 are two essentials to initiate the formation of the E-cadherin adhesion complex. On the other hand, Src has also the capability of disrupting the β-catenin–E-cadherin complex and down-regulating cell–cell adhesion. In this paper, using a multi-scale mathematical model, we study the role of each of these proteins in the adhesive profile and invasive properties of the tumour. To do this, we create three versions of an intracellular model that explains the interplay between the proteins E-cadherin, β-catenin, Src and PI3; and we couple them to the strength of the cell–cell adhesion forces within an individual-cell-based model. The simulation results show how the tumour profile and its aggressive potential may change depending on the intrinsic characteristics of the protein pathways, and how these pathways may influence the early stages of cancer invasion. Our major findings may be summarized as follows. (1) Intermediate levels of Src synthesis rates generate the least invasive tumour phenotype. (2) Conclusions drawn from findings obtained from the intracellular molecular dynamics (here cadherin–catenin binding complexes) to the multi-cellular invasive potential of a tumour may be misleading or erroneous. The conclusions should be validated in a multi-cellular context on timescales relevant for population growth. (3) Monoclonal populations of more cohesive cells with otherwise equal properties tend to grow slower. (4) Less cohesive cells tend to outcompete more cohesive cells. (5) Less cohesive cells have a larger probability of invasion as migration forces can more easily outbalance cohesive forces. (paper)

  15. Adhesives for Achieving Durable Bonds with Acetylated Wood

    Directory of Open Access Journals (Sweden)

    Charles R. Frihart

    2017-12-01

    Full Text Available Acetylation of wood imparts moisture durability, decay resistance, and dimensional stability to wood; however, making durable adhesive bonds with acetylated wood can be more difficult than with unmodified wood. The usual explanation is that the acetylated surface has fewer hydroxyl groups, resulting in a harder-to-wet surface and in fewer hydrogen bonds between wood and adhesive. This concept was evaluated using four different adhesives (resorcinol–formaldehyde, emulsion polymer isocyanate, epoxy, and melamine–formaldehyde with unmodified wood, acetylated wood, and acetylated wood that had been planed. Strikingly, acetylation did not hinder adhesive bonds with a waterborne resorcinol–formaldehyde adhesive that bonded equally well to both unmodified and acetylated yellow poplar. An epoxy adhesive bonded better to the acetylated wood than to the unmodified wood, in contrast to an emulsion polymer isocyanate, which gave less durable bonds to acetylated than to unmodified wood. Planing of the acetylated wood surface prior to bonding reduced bond durability for the epoxy adhesive and increased the amount of surface hydroxyl groups, as measured using X-ray photoelectron spectroscopic analysis of the trifluoroacetic anhydride-treated wood. These experiments showed that wood modification is useful in understanding wood-adhesive interactions, in addition to determining how to develop adhesives for acetylated woods.

  16. The effect of surface roughness and viscoelasticity on rubber adhesion.

    Science.gov (United States)

    Tiwari, A; Dorogin, L; Bennett, A I; Schulze, K D; Sawyer, W G; Tahir, M; Heinrich, G; Persson, B N J

    2017-05-21

    Adhesion between silica glass or acrylic balls and silicone elastomers and various industrial rubbers is investigated. The work of adhesion during pull-off is found to strongly vary depending on the system, which we attribute to the two opposite effects: (1) viscoelastic energy dissipation close to an opening crack tip and (2) surface roughness. Introducing surface roughness on the glass ball is found to increase the work of adhesion for soft elastomers, while for the stiffer elastomers it results in a strong reduction in the work of adhesion. For the soft silicone elastomers a strong increase in the work of adhesion with increasing pull-off velocity is observed, which may result from the non-adiabatic processes associated with molecular chain pull-out. In general, the work of adhesion is decreased after repeated contacts due to the transfer of molecules from the elastomers to the glass ball. Thus, extracting the free chains (oligomers) from the silicone elastomers is shown to make the work of adhesion independent of the number of contacts. The viscoelastic properties (linear and nonlinear) of all of the rubber compounds are measured, and the velocity dependent crack opening propagation energy at the interface is calculated. Silicone elastomers show a good agreement between the measured work of adhesion and the predicted results, but carbon black filled hydrogenated nitrile butadiene rubber compounds reveal that strain softening at the crack tip may play an important role in determining the work of adhesion. Additionally, adhesion measurement under submerged conditions in distilled water and water + soap solutions are also performed: a strong reduction in the work of adhesion is measured for the silicone elastomers submerged in water, and a complete elimination of adhesion is found for the water + soap solution attributed to an osmotic repulsion between the negatively charged surface of the glass and the elastomer.

  17. 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.

  18. Adhesive bonding of wood materials

    Science.gov (United States)

    Charles B. Vick

    1999-01-01

    Adhesive bonding of wood components has played an essential role in the development and growth of the forest products industry and has been a key factor in the efficient utilization of our timber resource. The largest use of adhesives is in the construction industry. By far, the largest amounts of adhesives are used to manufacture building materials, such as plywood,...

  19. Determination of the dynamics of restored teeth by 3D electronic speckle pattern interferometry.

    Science.gov (United States)

    Lang, H; Rampado, M; Müllejans, R; Raab, W H-M

    2004-01-01

    The difficulties typically encountered in studying the effects of restorations on tooth reinforcement are often due to the 3-dimensional (3D) nature of deformation. Therefore, electronic 3D-Speckle-Interferometry (3D-ESPI) was used to assess the impact of different restorative materials on the deformation of teeth. Small and large MOD-preparations in extracted premolars were restored with gold inlays, ceramic inlays, composite resin inlays, amalgam, or composite resin. The restorations and cusps were loaded (90 N) and the deformation was assessed by 3D-ESPI. Teeth with small restorations were deformed only slightly and the differences between the materials were minimal (P>0.05). In contrast, teeth with large restorations displayed material-specific deformation patterns: (a) all materials led to decreased deformation as compared with unfilled teeth, (b) elastic materials caused only local deformation, (c) non-adhesive materials resulted in translation of the restoration and marginal discrepancies, (d) adhesive inlays brought about increased deformation of the luting resin composite, (e) loading of the cusps caused higher deformation than loading of the restorations, and (f) bonded restorations stabilized the cusps. The results show that the deformation pattern of restored teeth is material-specific but the extent of deformation is primarily limited by the remaining tooth substance. Copyright 2004 Wiley-Liss, Inc.

  20. Tissue adhesives for simple traumatic lacerations.

    Science.gov (United States)

    Beam, Joel W

    2008-01-01

    using a standard form. The primary measure was cosmetic outcome. Secondary measures were pain with the procedure, time to complete the procedure, and complications (erythema, infection, discharge, need for delayed closure, and dehiscence). Studies were divided into 2 groups as follows: group 1, comparisons among tissue adhesives with SWC, and group 2, comparisons among different tissue adhesives. All eligible studies were assessed for methodologic quality independently by 2 investigators using the Jadad Scale, which evaluates randomization, double blinding, withdrawals, and dropouts and is scored on a 5-point (maximum) scale. The data from the tissue adhesive and SWC studies were pooled and analyzed with a random-effects model. The I (2) statistic was used to determine heterogeneity among the studies. chi (2) analysis was performed to compare participant age, wound location, and type of tissue adhesive among the studies. The data from the studies comparing tissue adhesives were pooled and analyzed using a fixed-effects model. The search criteria identified 39 eligible studies, of which 11 met the inclusion criteria. In 10 studies, a tissue adhesive was compared with SWC. Five groups used butylcyanoacrylate, and 5 used octylcyanoacrylate. For SWC, 6 groups used sutures, 2 used adhesive strips, and 2 used a combination of methods, although most used sutures. Six studies were limited to pediatric patients and 2 to adult patients; 2 included patients of any age. Wounds were limited to facial lacerations in 2 pediatric studies and 1 group with patients of any age. Lacerations requiring deep sutures were excluded in 4 studies. One group compared tissue adhesives (butylcyanoacrylate and octylcyanoacrylate) among pediatric patients with facial lacerations not requiring deep sutures. In the 11 included studies, authors of 9 randomized and evaluated 1 laceration per patient, whereas 2 groups included patients with more than 1 laceration. In 1 group, each laceration was

  1. Determinants of Romanians' Migration within the European Union: Static and Dynamic Panel Gravity Approaches

    Directory of Open Access Journals (Sweden)

    Adriana Ana Maria Davidescu

    2017-08-01

    Full Text Available The 1st of January 2007 marked Romania’s accession to the European Union (EU and represented its 'ticket' to a free access to the common market. This soon evolved into an important trigger for the increased migration flows from Romania towards the more developed western countries, members of the EU. Not only the opportunity of a free movement of persons – emerged with the integration - but also the existing socio-economic disparities between Romania and the more developed western countries in the EU, led to unidirectional migration flows. Using both static and dynamic panel gravity models, we aim to identify the main determinants of Romanians' migration towards 10 EU member states – Czech Republic, Denmark, Italy, Netherlands, Finland, Germany, Norway, Poland, Spain, and Sweden – for the period 2007-2014. Our empirical findings support the results of other studies performed on different economies. The most important pull factor for Romanians' migration is represented by the economic conditions in the destination countries, proxied by the GDP/capita. Other important pull factors fuelling Romanians' migration refer to the unemployment rate, life expectancy, education spending, and population density. A key role is also played by the existing social networks in the destination countries which are proxied in our model by the lagged migration flows

  2. DETERMINANTS OF PERFORMANCE IN INDONESIAN BANKING:A CROSS-SECTIONAL AND DYNAMIC PANEL DATA ANALYSIS

    Directory of Open Access Journals (Sweden)

    Buyung Sarita

    2012-07-01

    Full Text Available This paper examines determinants of bank performance inIndonesia for theperiod of 1994-1999. It was pooled cross-sectional time series and dynamic paneldata models. This research incorporates the traditional Structure-Conduct-Performance (SCP and Relative Efficiency (RE hypotheses. The estimationresults show that bank performance industry is competitive, and implies thatmarket structure in Indonesian banking sector is nearly perfect competition.However, no evidence has been found in this study in support of the traditionalSCP, while RE is otherwise. The negative relationship between loans to businessgroups and bank performance, which is likely due to the high loans provided tothem, thus supporting the moral hazard hypothesis. The negative relationshipbetween market share loan and return on assets, the negative relationship betweendebt-to-total assets and bank performance is likely because of the high level ofdebt. The negative relationship between debt-to-total assets and bank performancein a scenario of high interest rates indicates that banks acted responsibly by payinghigh interest charges prevailing at that time. This also results in the negativerelationship between capital adequacy ratio and bank performance.

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

    Science.gov (United States)

    McNarry, M A; Lewis, M J

    2012-06-01

    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 [Formula: see text]O(2peak) 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.

  4. Spatiotemporal Dynamics and Spatial Determinants of Urban Growth in Suzhou, China

    Directory of Open Access Journals (Sweden)

    Ling Zhang

    2017-03-01

    Full Text Available This paper analyzes the spatiotemporal dynamics of urban growth and models its spatial determinants in China through a case study of Suzhou, a rapidly industrializing and globalizing city. We conducted spatial analysis on land use data derived from multi-temporal remote sensing images of Suzhou from 1986 to 2008. Three urban growth types, namely infilling, edge-expansion, and leapfrog, were identified. We used landscape metrics to quantify the temporal trend of urban growth in Suzhou. During these 22 years, Suzhou’s urbanization changed from bottom-up rural urbanization to city-based top-down urban expansion. The underlying mechanism changed from TVE (town village enterprise driven rural industrialization to FDI (foreign direct investment driven development zone fever. Furthermore, we employed both global and local logistic regressions to model the probability of urban land conversion against a set of spatial variables. The global logistic regression model found the significance of proximity, neighborhood conditions, and socioeconomic factors. The logistic geographically weighted regression (GWR model improved the global regression model with better model goodness-of-fit and higher prediction accuracy. More importantly, the local parameter estimates of variables enabled us to exam spatial variations of the influences of variables on urban growth in Suzhou.

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

    Science.gov (United States)

    Almenara, J. M.; Díaz, R. F.; Bonfils, X.; Udry, S.

    2016-10-01

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

    International Nuclear Information System (INIS)

    McNarry, M A; Lewis, M J

    2012-01-01

    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 .VO 2peak 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)

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

    Science.gov (United States)

    2012-01-01

    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. PMID:22385782

  8. 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.

  9. Pressure modulation, a new dynamic technique for the electrochemical determination of adsorption, reaction and activation volumes.

    Science.gov (United States)

    Loewe, T; Baltruschat, H

    2005-01-21

    A new dynamic method for the measurement of pressure dependent kinetic and thermodynamic quantities is described and its successful operation demonstrated for two example systems. The pressure was modulated with an amplitude of only +/-1 bar or less by means of a piezo-transducer. The small effect on the reaction rate, potential or charge of the electrode can be detected using the lock in technique. The determination of the reaction volume of the redox couple Fe(CN)6(4-)/Fe(CN)6(3-) served as a control of the validity of the measurement and the reliability of the experimental approach. As a first model system the adsorption of hydrogen on polycrystalline Pt was studied. A volume of adsorption of 4.8 cm3 mol(-1) was found. The partial molar volume for protons in water (upsilon+ = -5.4 cm3 mol(-)) measured by Zana and Yeager, J. Phys. Chem., 1967, 71, 521-536, was used to establish that the partial molar volume of the adsorbed hydrogen was close to zero.

  10. Hydrogen bonding energy determined by molecular dynamics simulation and correlation to properties of thermoplastic starch films.

    Science.gov (United States)

    Yang, Jinhui; Tang, Kangkang; Qin, Guoqiang; Chen, Yanxue; Peng, Ling; Wan, Xia; Xiao, Huining; Xia, Qiuyang

    2017-06-15

    The molecular dynamics (MD) simulation method was used to investigate the hydrogen bonding energy of starch/glycerol system under different temperatures (range from 90°C to 120°C) and different glycerol contents (range from 20% to 40%, based on dry starch weight). These effects on the hydrogen bonding energy (including the total hydrogen bonding energy, hydrogen bonding energy of starch/starch, glycerol/glycerol, and starch/glycerol) were analyzed in detail. Meanwhile, glycerol plasticized starch films were prepared using casting method. The relationship between the hydrogen bonding energy and the performances of thermoplastic starch film (TPSF), such as crystallinity, mechanical properties and water uptake determined experimentally, were revealed and discussed. The results indicated that glycerol/starch film contained strong hydrogen bonding interaction which could be increased by decreasing the temperature or increasing the glycerol content. The hydrogen bonding interaction is the key factor for the preparation of the plasticized starch material, and the plasticized mechanism can be interpreted according to the analytical results of the simulation. Copyright © 2017 Elsevier Ltd. All rights reserved.

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

    International Nuclear Information System (INIS)

    Chen, S.; Liu, H.-L.; Yang Yihong; Hsu, Y.-Y.; Chuang, K.-S.

    2006-01-01

    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

  12. 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.

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

    Science.gov (United States)

    Behr, Julie; Gaskin, Byron; Fu, Changliang; Dong, Cheng; Kunz, Robert

    2015-01-01

    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.

  14. 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

  15. 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 

  16. 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....

  17. 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.

  18. The Impact of the Gas Distribution on the Determination of Dynamical Masses of Galaxies Using Unresolved Observations

    NARCIS (Netherlands)

    de Blok, W. J. G.; Walter, Fabian

    Dynamical mass (M dyn) is a key property of any galaxy, yet a determination of M dyn is not straightforward if spatially resolved measurements are not available. This situation occurs in single-dish H I observations of the local universe, but also frequently in high-redshift observations. M dyn

  19. How mechanical context and feedback jointly determine the use of mechanical variables in length perception by dynamic touch

    NARCIS (Netherlands)

    Menger, Rudmer; Withagen, Rob

    2009-01-01

    Earlier studies have revealed that both mechanical context and feedback determine what mechanical invariant is used to perceive length by dynamic touch. In the present article, the authors examined how these two factors jointly constrain the informational variable that is relied upon. Participants

  20. Relative stability of protein structures determined by X-ray crystallography or NMR spectroscopy : A molecular dynamics simulation study

    NARCIS (Netherlands)

    Fan, H; Mark, AE

    2003-01-01

    The relative stability of protein structures determined by either X-ray crystallography or nuclear magnetic resonance (NMR) spectroscopy has been investigated by using molecular dynamics simulation techniques. Published structures of 34 proteins containing between 50 and 100 residues have been

  1. Hydrogen dynamics in soil organic matter as determined by 13C and 2H labeling experiments

    Science.gov (United States)

    Paul, Alexia; Hatté, Christine; Pastor, Lucie; Thiry, Yves; Siclet, Françoise; Balesdent, Jérôme

    2016-12-01

    Understanding hydrogen dynamics in soil organic matter is important to predict the fate of 3H in terrestrial environments. One way to determine hydrogen fate and to point out processes is to examine the isotopic signature of the element in soil. However, the non-exchangeable hydrogen isotopic signal in soil is complex and depends on the fate of organic compounds and microbial biosyntheses that incorporate water-derived hydrogen. To decipher this complex system and to understand the close link between hydrogen and carbon cycles, we followed labeled hydrogen and labeled carbon throughout near-natural soil incubations. We performed incubation experiments with three labeling conditions: 1 - 13C2H double-labeled molecules in the presence of 1H2O; 2 - 13C-labeled molecules in the presence of 2H2O; 3 - no molecule addition in the presence of 2H2O. The preservation of substrate-derived hydrogen after 1 year of incubation (ca. 5 % in most cases) was lower than the preservation of substrate-derived carbon (30 % in average). We highlighted that 70 % of the C-H bonds are broken during the degradation of the molecule, which permits the exchange with water hydrogen. Added molecules are used more for trophic resources. The isotopic composition of the non-exchangeable hydrogen was mainly driven by the incorporation of water hydrogen during microbial biosynthesis. It is linearly correlated with the amount of carbon that is degraded in the soil. The quantitative incorporation of water hydrogen in bulk material and lipids demonstrates that non-exchangeable hydrogen exists in both organic and mineral-bound forms. The proportion of the latter depends on soil type and minerals. This experiment quantified the processes affecting the isotopic composition of non-exchangeable hydrogen, and the results can be used to predict the fate of tritium in the ecosystem or the water deuterium signature in organic matter.

  2. 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.

  3. 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.

  4. Determination of mixing quality in biogas plant digesters using tracer tests and computational fluid dynamics

    Directory of Open Access Journals (Sweden)

    Luděk Kamarád

    2013-01-01

    Full Text Available The total electricity demand of investigated biogas plants (BGP makes up 7–8 % of the total electricity produced. Nearly 40 % of this energy is consumed just for mixing in digesters and the energy demand for mixing in some biogas plants can be even higher. Therefore, optimal mixing in anaerobic digesters is a basic condition for efficient plant operation and biogas production. The use of problematic substrates (e.g. grass silage or other fibrous substrates, installation of unsuitable mixing systems or inconvenient mixing intervals may lead to mixing problems. Knowledge about mixing in biogas digesters is still insufficient, so the objective of this study was to fill the information gaps in the literature by determining the minimal retention time of substrates fed into anaerobic digesters and to describe substrate distribution and washing out rates from investigated digesters. Two full-scale biogas plant digesters (2000 m3 and 1500 m3 using different mixing systems and substrates were investigated. To characterize the substrate distribution, lithium hydroxide monohydrate solutions were used for tracer tests at concentrations of 47.1 mg Li+ / kg TS and 46.6 mg Li+ / kg TS in digester. The tracer concentration in the digester effluents was measured during two hydraulic retention times and compared. Although the tracer was detected in the digester effluent at nearly the same time in both cases, the tracer tests showed very different distribution curves. The tracer concentration in effluent B grew much slower than in effluent A and no significant short circuiting streams were detected. Although the data calculated by computational fluid dynamics methods (CFD showed a very good agreement with the full scale results, full comparison was not possible.

  5. Dynamics and molecular determinants of cytoplasmic lipid droplet clustering and dispersion.

    Directory of Open Access Journals (Sweden)

    David J Orlicky

    Full Text Available Perilipin-1 (Plin1, a prominent cytoplasmic lipid droplet (CLD binding phosphoprotein and key physiological regulator of triglyceride storage and lipolysis in adipocytes, is thought to regulate the fragmentation and dispersion of CLD that occurs in response to β-adrenergic activation of adenylate cyclase. Here we investigate the dynamics and molecular determinants of these processes using cell lines stably expressing recombinant forms of Plin1 and/or other members of the perilipin family. Plin1 and a C-terminal CLD-binding fragment of Plin1 (Plin1CT induced formation of single dense CLD clusters near the microtubule organizing center, whereas neither an N-terminal CLD-binding fragment of Plin1, nor Plin2 or Plin3 induced clustering. Clustered CLD coated by Plin1, or Plin1CT, dispersed in response to isoproterenol, or other agents that activate adenylate cyclase, in a process inhibited by the protein kinase A inhibitor, H89, and blocked by microtubule disruption. Isoproterenol-stimulated phosphorylation of CLD-associated Plin1 on serine 492 preceded their dispersion, and live cell imaging showed that cluster dispersion involved initial fragmentation of tight clusters into multiple smaller clusters, which then fragmented into well-dispersed individual CLD. siRNA knockdown of the cortical actin binding protein, moesin, induced disaggregation of tight clusters into multiple smaller clusters, and inhibited the reaggregation of dispersed CLD into tight clusters. Together these data suggest that the clustering and dispersion processes involve a complex orchestration of phosphorylation-dependent, microtubule-dependent and independent, and microfilament dependent steps.

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

    Science.gov (United States)

    Šíchová, Jindra; Voleníková, Anna; Dincă, Vlad; Nguyen, Petr; Vila, Roger; Sahara, Ken; Marec, František

    2015-05-19

    Chromosomal rearrangements have the potential to limit the rate and pattern of gene flow within and between species and thus play a direct role in promoting and maintaining speciation. Wood white butterflies of the genus Leptidea are excellent models to study the role of chromosome rearrangements in speciation because they show karyotype variability not only among but also within species. In this work, we investigated genome architecture of three cryptic Leptidea species (L. juvernica, L. sinapis and L. reali) by standard and molecular cytogenetic techniques in order to reveal causes of the karyotype variability. Chromosome numbers ranged from 2n = 85 to 91 in L. juvernica and 2n = 69 to 73 in L. sinapis (both from Czech populations) to 2n = 51 to 55 in L. reali (Spanish population). We observed significant differences in chromosome numbers and localization of cytogenetic markers (rDNA and H3 histone genes) within the offspring of individual females. Using FISH with the (TTAGG) n telomeric probe we also documented the presence of multiple chromosome fusions and/or fissions and other complex rearrangements. Thus, the intraspecific karyotype variability is likely due to irregular chromosome segregation of multivalent meiotic configurations. The analysis of female meiotic chromosomes by GISH and CGH revealed multiple sex chromosomes: W1W2W3Z1Z2Z3Z4 in L. juvernica, W1W2W3Z1Z2Z3 in L. sinapis and W1W2W3W4Z1Z2Z3Z4 in L. reali. Our results suggest a dynamic karyotype evolution and point to the role of chromosomal rearrangements in the speciation of Leptidea butterflies. Moreover, our study revealed a curious sex determination system with 3-4 W and 3-4 Z chromosomes, which is unique in the Lepidoptera and which could also have played a role in the speciation process of the three Leptidea species.

  7. ADHESION OF BIOCOMPATIBLE TiNb COATING

    Directory of Open Access Journals (Sweden)

    Tomas Kolegar

    2017-06-01

    Full Text Available Preparation of a coating with a high quality requires good adhesion of the film to the substrate. The paper deals with the adhesion of biocompatible TiNb coating with different base materials. Several materials such as titanium CP grade 2, titanium alloys Ti6Al4V and stainless steel AISI 316L were measured. Testing samples were made in the shape of small discs. Those samples were coated with a TiNb layer by using the PVD method (magnetron sputtering. Onto the measured layer of TiNb an assistant cylinder was stuck using a high strength epoxy adhesive E1100S. The sample with the assistant cylinder was fixed into a special fixture and the whole assembly underwent pull-off testing for adhesion. The main result of this experiment was determining the strength needed to peel the layer and morphology and size of the breakaway. As a result, we will be able to determine the best base material and conditions where the coating will be remain intact with the base material.

  8. 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.

  9. A novel c-Src recruitment pathway from the cytosol to focal adhesions.

    Science.gov (United States)

    Machiyama, Hiroaki; Yamaguchi, Tomoyuki; Watanabe, Tomonobu M; Fujita, Hideaki

    2017-07-01

    The role of myristoylation in the localization and catalytic activity of Src at focal adhesions was investigated by live-cell imaging and site-directed mutagenesis. Although the majority of activated Src molecules are localized at focal adhesions, it is unclear how activated Src molecules are recruited to focal adhesions. Because Src is activated at the cell membrane, translocation of Src to cell membranes is considered to be essential for its recruitment to focal adhesions. Membrane-targeting-deficient Src mutant SrcG2A localizes at focal adhesions, indicating direct recruitment of Src from cytosol to focal adhesions. Furthermore, directly recruited Src molecules are shown to enhance paxillin dynamics at focal adhesions. These results reveal that the regulation of Src activation and translocation is more complex than previously suggested. © 2017 Federation of European Biochemical Societies.

  10. Analytic determination of dynamical and mosaic length scales in a Kac glass model

    Energy Technology Data Exchange (ETDEWEB)

    Franz, S [Abdus Salam ICTP, Strada Costiera 11, PO Box 586, I-34100 Trieste (Italy); Montanari, A [Isaac Newton Institute for Mathematical Sciences 20 Clarkson Road, Cambridge, CB3 0EH (United Kingdom)

    2007-03-16

    We consider a disordered spin model with multi-spin interactions undergoing a glass transition. We introduce dynamic and static length scales and compute them in the Kac limit (long-but-finite range interactions). They diverge at the dynamic and static phase transition with exponents -1/4 and -1 (respectively). The two length scales are approximately equal well above the mode coupling transition. Their discrepancy increases rapidly as this transition is approached. We argue that this signals a crossover from mode coupling to activated dynamics. (fast track communication)

  11. Microtensile bond strength of etch and rinse versus self-etch adhesive systems.

    Science.gov (United States)

    Hamouda, Ibrahim M; Samra, Nagia R; Badawi, Manal F

    2011-04-01

    The aim of this study was to compare the microtensile bond strength of the etch and rinse adhesive versus one-component or two-component self-etch adhesives. Twelve intact human molar teeth were cleaned and the occlusal enamel of the teeth was removed. The exposed dentin surfaces were polished and rinsed, and the adhesives were applied. A microhybride composite resin was applied to form specimens of 4 mm height and 6 mm diameter. The specimens were sectioned perpendicular to the adhesive interface to produce dentin-resin composite sticks, with an adhesive area of approximately 1.4 mm(2). The sticks were subjected to tensile loading until failure occurred. The debonded areas were examined with a scanning electron microscope to determine the site of failure. The results showed that the microtensile bond strength of the etch and rinse adhesive was higher than that of one-component or two-component self-etch adhesives. The scanning electron microscope examination of the dentin surfaces revealed adhesive and mixed modes of failure. The adhesive mode of failure occurred at the adhesive/dentin interface, while the mixed mode of failure occurred partially in the composite and partially at the adhesive/dentin interface. It was concluded that the etch and rinse adhesive had higher microtensile bond strength when compared to that of the self-etch adhesives. Copyright © 2010 Elsevier Ltd. All rights reserved.

  12. The effect of Kombucha on post-operative intra-abdominal adhesion formation in rats.

    Science.gov (United States)

    Maghsoudi, Hemmat; Mohammadi, Hussein Benagozar

    2009-04-01

    Peritoneal adhesions are fibrous bands of tissues formed between organs that are normally separated and/or between organs and the internal body wall after peritoneal injury. The aim of the study was to investigate the effect of intra-peritoneal administration of Kombucha on intra-peritoneal adhesions. Eighty Wistar rats were subjected to standardized lesion by scraping model and were randomly divided into two groups. Group I received no treatment, and Group II received 15 ml of Kombucha solution intra-peritoneally. On the post-operative 14th day adhesion intensity score, inflammatory cell reaction and number of adhesion bands were determined. In the control group, there were no rats with grade 0 and I adhesions. In the group II, there were 26 rats (78.8%) with grade 0-2 adhesions. Adhesion intensity was significantly less in group II (PKombucha might be useful for preventing peritoneal adhesions.

  13. Engineering emergent multicellular behavior through synthetic adhesion

    Science.gov (United States)

    Glass, David; Riedel-Kruse, Ingmar

    In over a decade, synthetic biology has developed increasingly robust gene networks within single cells, but constructed very few systems that demonstrate multicellular spatio-temporal dynamics. We are filling this gap in synthetic biology's toolbox by developing an E. coli self-assembly platform based on modular cell-cell adhesion. We developed a system in which adhesive selectivity is provided by a library of outer membrane-displayed peptides with intra-library specificities, while affinity is provided by consistent expression across the entire library. We further provide a biophysical model to help understand the parameter regimes in which this tool can be used to self-assemble into cellular clusters, filaments, or meshes. The combined platform will enable future development of synthetic multicellular systems for use in consortia-based metabolic engineering, in living materials, and in controlled study of minimal multicellular systems. Stanford Bio-X Bowes Fellowship.

  14. Spectroscopic and morphologic characterization of the dentin/adhesive interface

    Science.gov (United States)

    Lemor, R. M.; Kruger, Michael B.; Wieliczka, David M.; Swafford, Jim R.; Spencer, Paulette

    1999-01-01

    The potential environmental risks associated with mercury release have forced many European countries to ban the use of dental amalgam. Alternative materials such as composite resins do not provide the clinical function for the length of time characteristically associated with dental amalgam. The weak link in the composite restoration is the dentin/adhesive bond. The purpose of this study was to correlate morphologic characterization of the dentin/adhesive bond with chemical analyses using micro- Fourier transform infrared and micro-Raman spectroscopy. A commercial dental adhesive was placed on dentin substrates cut from extracted, unerupted human third molars. Sections of the dentin/adhesive interface were investigated using infrared radiation produced at the Aladdin synchrotron source; visible radiation from a Kr+ laser was used for the micro-Raman spectroscopy. Sections of the dentin/adhesive interface, differentially stained to identify protein, mineral, and adhesive, were examined using light microscopy. Due to its limited spatial resolution and the unknown sample thickness the infrared results cannot be used quantitatively in determining the extent of diffusion. The results from the micro-Raman spectroscopy and light microscopy indicate exposed protein at the dentin/adhesive interface. Using a laser that reduces background fluorescence, the micro-Raman spectroscopy provides quantitative chemical and morphologic information on the dentin/adhesive interface. The staining procedure is sensitive to sites of pure protein and thus, complements the Raman results.

  15. Determining the shear viscosity of model liquids from molecular dynamics simulations

    NARCIS (Netherlands)

    Hess, B

    2002-01-01

    Several methods are available for calculating shear viscosities of liquids from molecular dynamics simulations. There are equilibrium methods based on pressure or momentum fluctuations and several nonequilibrium methods. For the nonequilibrium method using a periodic shear flow, all relevant

  16. Fluid and structural dynamics calculations to determine core barrel loads during blowdown (EV 3,000)

    International Nuclear Information System (INIS)

    Krieg, R.; Schlechtendahl, E.G.

    1977-01-01

    To begin with, the main physical phenomena in connection with blowdown loads on the care barrel and the computer models used are briefly described. These models have also been used in the design of the HTR test care barrel. The fluid dynamics part of the calculations was carried out using the WHAMMOD and DAPSY codes; for the structural dynamics part, the STRUDL/Dynal code was employed. (orig./RW) [de

  17. Mitogen-activated protein kinase (MAPK) dynamics determine cell fate in the yeast mating response.

    Science.gov (United States)

    Li, Yang; Roberts, Julie; AkhavanAghdam, Zohreh; Hao, Nan

    2017-12-15

    In the yeast Saccharomyces cerevisiae , the exposure to mating pheromone activates a prototypic mitogen-activated protein kinase (MAPK) cascade and triggers a dose-dependent differentiation response. Whereas a high pheromone dose induces growth arrest and formation of a shmoo-like morphology in yeast cells, lower pheromone doses elicit elongated cell growth. Previous population-level analysis has revealed that the MAPK Fus3 plays an important role in mediating this differentiation switch. To further investigate how Fus3 controls the fate decision process at the single-cell level, we developed a specific translocation-based reporter for monitoring Fus3 activity in individual live cells. Using this reporter, we observed strikingly different dynamic patterns of Fus3 activation in single cells differentiated into distinct fates. Cells committed to growth arrest and shmoo formation exhibited sustained Fus3 activation. In contrast, most cells undergoing elongated growth showed either a delayed gradual increase or pulsatile dynamics of Fus3 activity. Furthermore, we found that chemically perturbing Fus3 dynamics with a specific inhibitor could effectively redirect the mating differentiation, confirming the causative role of Fus3 dynamics in driving cell fate decisions. MAPKs mediate proliferation and differentiation signals in mammals and are therapeutic targets in many cancers. Our results highlight the importance of MAPK dynamics in regulating single-cell responses and open up the possibility that MAPK signaling dynamics could be a pharmacological target in therapeutic interventions. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  18. 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)

  19. Determination of residual stresses and natural frequencies of roll-tensioned disc by a dynamic simulation of the rolling process

    Science.gov (United States)

    Skordaris, G.; Bouzakis, K.-D.; Tasoulas, D.

    2017-02-01

    Roll tensioning is a common method for increasing locally the superficial strength of thin circular saws and in this way their dynamic stability. Through roll tensioning, residual stresses are induced into the disc material leading to a significant enhancement of its dynamic stiffness. In this paper, a FEM-methodology is proposed for determining the developed residual stresses in the discs after rolling and for investigating their effects on the circular saw natural frequencies. More specifically, a 3D-FEM model was developed for the dynamic simulation of the rolling process on circular saws, using the LS-DYNA software. This model enables the explicit determination of the developed residual stresses in the roll-tensioned discs. Furthermore, the natural frequencies of the pre-stressed circular saws were calculated by the ANSYS software. In these calculations, the already determined residual stresses were taken into consideration. Different distances of the roll-tensioned zone from the disc centre were taken into account for estimating their effect on the disc’s natural frequencies. By the proposed methodology, optimum roll-tensioning conditions can be predicted for improving the dynamic behaviour of thin circular saws during cutting.

  20. Determining Occurrence Dynamics when False Positives Occur: Estimating the Range Dynamics of Wolves from Public Survey Data.

    Science.gov (United States)

    Miller, David A W; Nichols, James D; Gude, Justin A; Rich, Lindsey N; Podruzny, Kevin M; Hines, James E; Mitchell, Michael S

    2013-01-01

    Large-scale presence-absence monitoring programs have great promise for many conservation applications. Their value can be limited by potential incorrect inferences owing to observational errors, especially when data are collected by the public. To combat this, previous analytical methods have focused on addressing non-detection from public survey data. Misclassification errors have received less attention but are also likely to be a common component of public surveys, as well as many other data types. We derive estimators for dynamic occupancy parameters (extinction and colonization), focusing on the case where certainty can be assumed for a subset of detections. We demonstrate how to simultaneously account for non-detection (false negatives) and misclassification (false positives) when estimating occurrence parameters for gray wolves in northern Montana from 2007-2010. Our primary data source for the analysis was observations by deer and elk hunters, reported as part of the state's annual hunter survey. This data was supplemented with data from known locations of radio-collared wolves. We found that occupancy was relatively stable during the years of the study and wolves were largely restricted to the highest quality habitats in the study area. Transitions in the occupancy status of sites were rare, as occupied sites almost always remained occupied and unoccupied sites remained unoccupied. Failing to account for false positives led to over estimation of both the area inhabited by wolves and the frequency of turnover. The ability to properly account for both false negatives and false positives is an important step to improve inferences for conservation from large-scale public surveys. The approach we propose will improve our understanding of the status of wolf populations and is relevant to many other data types where false positives are a component of observations.

  1. Pseudo-extravasation rate constant of dynamic susceptibility contrast-MRI determined from pharmacokinetic first principles.

    Science.gov (United States)

    Li, Xin; Varallyay, Csanad G; Gahramanov, Seymur; Fu, Rongwei; Rooney, William D; Neuwelt, Edward A

    2017-11-01

    Dynamic susceptibility contrast-magnetic resonance imaging (DSC-MRI) is widely used to obtain informative perfusion imaging biomarkers, such as the relative cerebral blood volume (rCBV). The related post-processing software packages for DSC-MRI are available from major MRI instrument manufacturers and third-party vendors. One unique aspect of DSC-MRI with low-molecular-weight gadolinium (Gd)-based contrast reagent (CR) is that CR molecules leak into the interstitium space and therefore confound the DSC signal detected. Several approaches to correct this leakage effect have been proposed throughout the years. Amongst the most popular is the Boxerman-Schmainda-Weisskoff (BSW) K 2 leakage correction approach, in which the K 2 pseudo-first-order rate constant quantifies the leakage. In this work, we propose a new method for the BSW leakage correction approach. Based on the pharmacokinetic interpretation of the data, the commonly adopted R 2 * expression accounting for contributions from both intravascular and extravasating CR components is transformed using a method mathematically similar to Gjedde-Patlak linearization. Then, the leakage rate constant (K L ) can be determined as the slope of the linear portion of a plot of the transformed data. Using the DSC data of high-molecular-weight (~750 kDa), iron-based, intravascular Ferumoxytol (FeO), the pharmacokinetic interpretation of the new paradigm is empirically validated. The primary objective of this work is to empirically demonstrate that a linear portion often exists in the graph of the transformed data. This linear portion provides a clear definition of the Gd CR pseudo-leakage rate constant, which equals the slope derived from the linear segment. A secondary objective is to demonstrate that transformed points from the initial transient period during the CR wash-in often deviate from the linear trend of the linearized graph. The inclusion of these points will have a negative impact on the accuracy of the leakage

  2. 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

  3. Polymer Claw: Instant Underwater Adhesive

    Science.gov (United States)

    2012-09-24

    glycerol is a well-known hygroscopic liquid and lubricant. In the Polymer Claw Progress Report -4- 9/24/12 The Johns Hopkins University Applied Physics...the Polymer Claw adhesive partially solidified, while commercial adhesives were completely liquid after one hour. However, the curing rate was...is not valid for partial liquid adhesives, we will only test at later times, noting the minimum time for which the glass slides break. The time to

  4. 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

  5. Polyurethane adhesive ingestion.

    Science.gov (United States)

    Fitzgerald, Kevin T; Bronstein, Alvin C

    2013-02-01

    Polyurethane adhesives are found in a large number of household products in the United States and are used for a variety of purposes. Several brands of these expanding wood glues (those containing diphenylmethane diisocyanate [MDI]) have the potential to form gastrointestinal (GI) foreign bodies if ingested. The ingested adhesive forms an expanding ball of glue in the esophagus and gastric lumen. This expansion is caused by a polymerization reaction using the heat, water, and gastric acids of the stomach. A firm mass is created that can be 4-8 times its original volume. As little as 2 oz of glue have been reported to develop gastric foreign bodies. The obstructive mass is reported to form within minutes of ingestion of the adhesive. The foreign body can lead to esophageal impaction and obstruction, airway obstruction, gastric outflow obstruction, mucosal hemorrhage, ulceration, laceration, perforation of the esophageal and gastric linings, and death. Clinical signs following ingestion include anorexia, lethargy, vomiting, tachypnea, and abdominal distention and pain, and typically develop within 12 hours. Clinical signs may depend upon the size of the mass. If left untreated, perforation and rupture of the esophagus or stomach can occur. The glue mass does not stick to the GI mucosa and is not always detectable on abdominal palpation. Radiographs are recommended to confirm the presence of the "glue-ball" foreign body, and radiographic evidence of the obstruction may be seen as early as 4-6 hours following ingestion. Emesis is contraindicated owing to the risk of aspiration of the glue into the respiratory tree or the subsequent lodging of the expanding glue mass in the esophagus. Likewise, efforts to dilute the glue and prevent the formation of the foreign body through administration of liquids, activated charcoal, or bulk-forming products to push the foreign body through the GI tract have proven ineffective. Even endoscopy performed to remove the foreign body has

  6. Interfacial fracture toughness of aged adhesive-dentin interfaces.

    Science.gov (United States)

    De Munck, Jan; Poitevin, André; Lührs, Anne-Katrin; Pongprueksa, Pong; Van Ende, Annelies; Van Landuyt, Kirsten L; Van Meerbeek, Bart

    2015-04-01

    To assess interfacial fracture toughness of different adhesive approaches and compare to a standard micro-tensile bond-strength (μTBS) test after 6 months water storage. Chevron-notched beam fracture toughness (CNB) was determined using a modified ISO 24370:2005 standard. Adhesive-dentin micro-specimens (1.0 mm × 1.0 mm × 8-10 mm) were stressed in tensile until failure to determine the micro-tensile bond strength (μTBS). The highest mean μTBS and interfacial fracture toughness were measured for the multi-step adhesives Clearfil SE Bond (Kuraray Noritake) and OptiBond FL (Kerr). While large differences were observed in the bond strength values (from 7.4 to 27.2 MPa) of the one-step self-etch adhesives tested, interfacial fracture toughness was less different (from 0.7 to 1.0 MPam(1/2)). The adhesive with the lowest mean toughness (All-bond Universal, Bisco) had however the highest Weibull reliability, which might be a better parameter in regard to more consistent clinical performance. The self-adhesive composite Vertise Flow (Kerr) scored significantly lower at all levels. Although the ranking of the adhesives tested using CNB and μTBS corresponded well, the outcome of CNB appeared more reliable and less variable. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  7. 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

  8. Demonstration/Validation of Hazardous Air Pollutant-Free Adhesive Replacement for Federal Specification MMM-A-121 on the Stryker Infantry Carrier Vehicle

    Science.gov (United States)

    2013-06-01

    of hazardous air pollutant (HAP) emissions produced in coating operations, including adhesives application and removal. Adhesives and sealants ...addition to alternative substrates, such as silicone rubber and lightweight composite materials, showing a high versatility to the 3M-847 adhesive...installations were surveyed, and it was determined that the Army used numerous adhesives and sealants , among other coating materials, that contain significant

  9. 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

  10. Determination of shear viscosity of molecular nitrogen (N2): molecular dynamic hard rotor methodology and the results.

    Science.gov (United States)

    Strak, Paweł; Krukowski, Stanisław

    2011-04-21

    Determination of shear viscosity of molecular nitrogen (N(2)) by molecular dynamics (MD) in the high density range needs explicit incorporation of the rotational motion and therefore precise knowledge of angular dependence of N(2)-N(2) intermolecular potential. Newly designed Couette flow nonequilibrium molecular dynamic (NEMD) simulation procedure employs corrugated moving boundary, coupling the moving walls to translational and rotational motion exactly. Low density data on nitrogen viscosity show good agreement between MD data and experiment, confirming the radial dependence of the potential derived from quantum mechanical (QM) high precision calculations (coupled-cluster singles-and-doubles with a perturbative triples corrections [CCSD(T)]). Additionally, the angular dependence of the potential is verified using shear viscosity data for high density region, obtained from newly developed molecular dynamics (MD) simulations. It was demonstrated that the corrugated wall flow simulations provide results that are independent of the details of wall potential, fulfilling a basic requirement for application of MD simulations. These results are in good agreement with the equilibrium molecular dynamics (EMD) viscosity, derived from the Green-Kubo formula. Derived analytical dependence of the shear viscosity on the density and temperature shows that the MD data are in good agreement with experiment. Thus, MD simulations indicate that the CCSD(T) potential angular form is sufficiently precise for determination of the viscosity in a wide range of temperature and pressure.

  11. Studies on the Adhesive Property of Snail Adhesive Mucus.

    Science.gov (United States)

    Newar, Janu; Ghatak, Archana

    2015-11-10

    Many gastropod molluscs are known to secrete mucus which allow these animals to adhere to a substrate while foraging over it. While the mucus is known to provide strong adhesion to both dry and wet surfaces, including both horizontal and vertical ones, no systematic study has been carried out to understand the strength of such adhesion under different conditions. We report here results from preliminary studies on adhesion characteristics of the mucus of a snail found in eastern India, Macrochlamys indica. When perturbed, the snail was found to secrete its adhesive mucus, which was collected and subjected to regular adhesion tests. The hydrated mucus was used as such, and also as mixed with buffer of different pH. These experiments suggest that the mucus was slightly alkaline, and showed the maximum adhesion strength of 9 kPa when present in an alkaline buffer. Preliminary studies indicate that adhesive force is related to the ability of the mucus to incorporate water. In alkaline condition, the gel like mass that it forms, incorporate water from a wet surface and enable strong adhesion.

  12. Gecko-Inspired Electrospun Flexible Fiber Arrays for Adhesion

    Science.gov (United States)

    Najem, Johnny F.

    The ability of geckos to adhere to vertical solid surfaces comes from their remarkable feet with millions of projections terminating in nanometer spatulae. We present a simple yet robust method for fabricating directionally sensitive dry adhesives. By using electrospun nylon 6 nanofiber arrays, we create gecko-inspired dry adhesives, that are electrically insulating, and that show shear adhesion strength of 27 N/cm2 on a glass slide. This measured value is 270% that reported of gecko feet and 97-fold above normal adhesion strength of the same arrays. The data indicate a strong shear binding-on and easy normal lifting-off. This anisotropic strength distribution is attributed to an enhanced shear adhesion strength with decreasing fiber diameter (d) and an optimum performance of nanofiber arrays in the shear direction over a specific range of thicknesses. With use of electrospinning, we report the fabrication of nylon 6 nanofiber arrays that show a friction coefficient (mu) of 11.5. These arrays possess significant shear adhesion strength and low normal adhesion strength. Increasing the applied normal load considerably enhances the shear adhesion strength and mu, irrespective of d and fiber arrays thickness (T). Fiber bending stiffness and fiber surface roughness are considerably decreased with diminishing d while fiber packing density is noticeably increased. These enhancements are proposed to considerably upsurge the shear adhesion strength between nanofiber arrays and a glass slide. The latter upsurge is mainly attributed to a sizeable proliferation in van der Waals (vdW) forces. These nanofiber arrays can be alternatively bound-on and lifted-off over a glass slide with a trivial decrease in the initial mu and adhesion strength. By using selective coating technique, we have also created hierarchical structures having closely packed nanofibers with d of 50 nm. We determine the effects of applied normal load, fiber surface roughness, loading angle, d, T, and repeated

  13. 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.

  14. 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...

  15. Determinants of Self-Employment Dynamics and their Implications on Entrepreneurial Policy Effectiveness

    Directory of Open Access Journals (Sweden)

    José María Millán

    2010-07-01

    Full Text Available This paper summarizes the main results of the empirical research on self-employment dynamics —particularly entry and success— and discusses their possible implications on entrepreneurial policy effectiveness. The main goal of this study is to promote a debate on this topic, encouraging conditional analyses that serve as guidance in the design of a policy agenda.

  16. 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...

  17. Determine the effect of repeated dynamic loading on the performance of tunnel support systems

    CSIR Research Space (South Africa)

    Güler, G

    2001-03-01

    Full Text Available rope lacing, and fibre reinforced shotcrete. The simulated rock mass comprised concrete blocks stacked within the defined rock bolt pattern in the geometry of a pyramid. The system was loaded dynamically by means of a drop weight from which...

  18. Nascent chromatin capture proteomics determines chromatin dynamics during DNA replication and identifies unknown fork components

    DEFF Research Database (Denmark)

    Alabert, Constance; Bukowski-Wills, Jimi-Carlo; Lee, Sung-Po

    2014-01-01

    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 3,995 proteins. The replication machinery and 485 chromatin factors...

  19. 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

  20. 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.

  1. Dynamic determination of modulus of elasticity of full-size wood composite panels using a vibration method

    Science.gov (United States)

    Cheng Guan; Houjiang Zhang; Lujing Zhou; Xiping Wang

    2015-01-01

    A vibration testing method based on free vibration theory in a ‘‘free–free” support condition was investigated for evaluating the modulus of elasticity (MOE) of full-size wood composite panels (WCPs). Vibration experiments were conducted on three types of WCPs (medium density fibreboard, particleboard, and plywood) to determine the dynamic MOE of the panels. Static...

  2. 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

  3. Cell Adhesions: Actin-Based Modules that Mediate Cell-Extracellular Matrix and Cell-Cell Interactions

    Science.gov (United States)

    Bachir, Alexia; Horwitz, Alan Rick; Nelson, W. James; Bianchini, Julie M.

    2018-01-01

    Cell adhesions link cells to the extracellular matrix (ECM) and to each other, and depend on interactions with the actin cytoskeleton. Both cell-ECM and cell-cell adhesion sites contain discrete, yet overlapping functional modules. These modules establish physical association with the actin cytoskeleton, locally modulate actin organization and dynamics, and trigger intracellular signaling pathways. Interplay between these modules generates distinct actin architectures that underlie different stages, types, and functions of cell-ECM and cell-cell adhesions. Actomyosin contractility is required to generate mature, stable adhesions, as well as sense and translate the mechanical properties of the cellular environment to changes in cell organization and behavior. In this chapter we discuss the organization and function of different adhesion modules and how they interact with the actin cytoskeleton. We highlight the molecular mechanisms of mechanotransduction in adhesions, and how adhesion molecules mediate crosstalk between cell-ECM and cell-cell adhesion sites. PMID:28679638

  4. The effect of water on the gecko adhesive system

    Science.gov (United States)

    Stark, Alyssa Yeager

    The gecko adhesive system is a dry, reversible adhesive that is virtually surface-insensitive due to the utilization of intermolecular van der Waals forces. Remarkably, although detailed models of the adhesive mechanism exist and hundreds of gecko-inspired synthetics have been fabricated, our ability to fully replicate the system still falls short. One reason for this is our limited understanding of how the system performs in natural environments. To begin to resolve this I focused on one particular environmental parameter, water. Although thin layers of water can disrupt van der Waals forces, I hypothesized that geckos are able to retain or regain adhesive function on wet surfaces. I was motivated to investigate this hypothesis because many species of gecko are native to the tropics, a climate where we expect surface water to be prevalent, thus it is likely geckos have some mechanism to overcome the challenges associated with surface water and wetting. Despite the challenge water should pose to adhesion, I found that when tested on hydrophobic substrates geckos cling equally well in air and water. Conversely, on wet hydrophilic substrates geckos cannot support their body weight. Investigating these results further, I found that the superhydrophobic nature of the adhesive toe pads allows geckos to form an air bubble around their foot, which when pressed into contact with a hydrophobic substrate likely removes water from the adhesive interface. When the toe pads are no longer superhydrophobic however, geckos cannot support their body weight and fall from substrates. In order to regain adhesion geckos only need to take about ten steps on a dry substrate to self-dry their toe pads. Finally, when measuring a dynamic component of adhesion, running, we found that geckos are able to maintain speed on misted hydrophobic and hydrophilic substrates, contrary to what we would predict based on static shear adhesion measurements. In conclusion, my research provides a detailed

  5. Syndecans, signaling, and cell adhesion

    DEFF Research Database (Denmark)

    Couchman, J R; Woods, A

    1996-01-01

    structures within the heparan sulfate chains, leaving the roles of chondroitin sulfate chains and extracellular portion of the core proteins to be elucidated. Evidence that syndecans are a class of receptor involved in cell adhesion is mounting, and their small cytoplasmic domains may link...... transmembrane signaling from matrix to cytoskeleton, as proposed for other classes of adhesion receptors....

  6. Effect of fibril shape on adhesive properties

    Science.gov (United States)

    Soto, Daniel; Hill, Ginel; Parness, Aaron; Esparza, Noé; Cutkosky, Mark; Kenny, Tom

    2010-08-01

    Research into the gecko's adhesive system revealed a unique architecture for adhesives using tiny hairs. By using a stiff material (β-keratin) to create a highly structured adhesive, the gecko's system demonstrates properties not seen in traditional pressure-sensitive adhesives which use a soft, unstructured planar layer. In contrast to pressure sensitive adhesives, the gecko adhesive displays frictional adhesion, in which increased shear force allows it to withstand higher normal loads. Synthetic fibrillar adhesives have been fabricated but not all demonstrate this frictional adhesion property. Here we report the dual-axis force testing of single silicone rubber pillars from synthetic adhesive arrays. We find that the shape of the adhesive pillar dictates whether frictional adhesion or pressure-sensitive behavior is observed. This work suggests that both types of behavior can be achieved with structures much larger than gecko terminal structures. It also indicates that subtle differences in the shape of these pillars can significantly influence their properties.

  7. Editorial Commentary: Recalcitrant Idiopathic Adhesive Capsulitis of the Shoulder.

    Science.gov (United States)

    Yoo, Jae Chul

    2017-03-01

    An investigation of recalcitrant idiopathic adhesive capsulitis of the shoulder showed good outcomes with arthroscopic capsular release. However, it is critical that future authors carefully define the term "recalcitrant idiopathic adhesive capsulitis" so that we are speaking the same language and that future authors include a control (nonsurgical) treatment group to better determine whether surgery is truly superior to nonsurgical treatment. Copyright © 2017 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

  8. Relationship between enamel bond fatigue durability and surface free-energy characteristics with universal adhesives.

    Science.gov (United States)

    Nagura, Yuko; Tsujimoto, Akimasa; Barkmeier, Wayne W; Watanabe, Hidehiko; Johnson, William W; Takamizawa, Toshiki; Latta, Mark A; Miyazaki, Masashi

    2018-04-01

    The relationship between enamel bond fatigue durability and surface free-energy characteristics with universal adhesives was investigated. The initial shear bond strengths and shear fatigue strengths of five universal adhesives to enamel were determined with and without phosphoric acid pre-etching. The surface free-energy characteristics of adhesive-treated enamel with and without pre-etching were also determined. The initial shear bond strength and shear fatigue strength of universal adhesive to pre-etched enamel were higher than those to ground enamel. The initial shear bond strength and shear fatigue strength of universal adhesive to pre-etched enamel were material dependent, unlike those to ground enamel. The surface free-energy of the solid (γ S ) and the hydrogen-bonding force (γSh) of universal adhesive-treated enamel were different depending on the adhesive, regardless of the presence or absence of pre-etching. The bond fatigue durability of universal adhesives was higher to pre-etched enamel than to ground enamel. In addition, the bond fatigue durability to pre-etched enamel was material dependent, unlike that to ground enamel. The surface free-energy characteristics of universal adhesive-treated enamel were influenced by the adhesive type, regardless of the presence or absence of pre-etching. The surface free-energy characteristics of universal adhesive-treated enamel were related to the results of the bond fatigue durability. © 2018 Eur J Oral Sci.

  9. Inelastic Neutron Scattering and Molecular Dynamics Determination of the Interaction Potential in Liquid CD4

    International Nuclear Information System (INIS)

    Guarini, E.; Barocchi, F.; Sampoli, M.; Venturi, G.; Bafile, U.

    2007-01-01

    Anisotropic interactions of liquid CD 4 are studied in detail by comparison of inelastic neutron Brillouin scattering data with molecular dynamics simulations using up to four different models of the methane site-site potential. We demonstrate that the experimental dynamic structure factor S(Q,ω) acts as a highly discriminating quantity for possible interaction schemes. In particular, the Q evolution of the spectra enables a selective probing of the short- and medium-range features of the anisotropic potentials. We show that the preferential configuration of methane dimers at liquid densities can thus be discerned by analyzing the orientation-dependent model potential curves, in light of the experimental and simulation results

  10. Determination of fault operation dynamical constraints for the design of wind turbine DFIG drives

    CERN Document Server

    Aguglia, Davide; Wamkeue, René; Cros, Jérôme

    2010-01-01

    This paper presents an efficient design tool for the estimation of the transient electromagnetic peak torque and transient rotor over-voltages of wind turbines (WT) doubly-fed induction generators (DFIG) during severe fault conditions on the grid side. This versatile and robust tool is well adapted to the implementation in a DFIG drives CAD environment using iterative optimization procedures. In such an application, it is used to compute the dynamical constraints function during the integrated design process of the whole drive including the generator, the gearbox and the power converters. Results show that it is necessary to take into account the dynamical constraints under fault operation, during the early steps of the system design process. Another application of the tool is also illustrated in the paper: the design of the protection system (i.e. the crowbar resistance) for a given generator, a given gearbox and a given power converter.

  11. Reciprocity-based experimental determination of dynamic forces and moments: A feasibility study

    Science.gov (United States)

    Ver, Istvan L.; Howe, Michael S.

    1994-01-01

    BBN Systems and Technologies has been tasked by the Georgia Tech Research Center to carry Task Assignment No. 7 for the NASA Langley Research Center to explore the feasibility of 'In-Situ Experimental Evaluation of the Source Strength of Complex Vibration Sources Utilizing Reciprocity.' The task was carried out under NASA Contract No. NAS1-19061. In flight it is not feasible to connect the vibration sources to their mounting points on the fuselage through force gauges to measure dynamic forces and moments directly. However, it is possible to measure the interior sound field or vibration response caused by these structureborne sound sources at many locations and invoke principle of reciprocity to predict the dynamic forces and moments. The work carried out in the framework of Task 7 was directed to explore the feasibility of reciprocity-based measurements of vibration forces and moments.

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

    DEFF Research Database (Denmark)

    Achenbach, Michael; Ostermann, Klaus

    2010-01-01

    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......The implementation of unit tests with mock objects and stubs often involves substantial manual work. Stubbed methods return simple default values, therefore variations of these values require separate test cases. The integration of mock objects often requires more infrastructure code and design...... 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...

  13. Determination of ion quantity by using low-temperature ion density theory and molecular dynamics simulation

    International Nuclear Information System (INIS)

    Du Li-Jun; Song Hong-Fang; Li Hai-Xia; Chen Shao-Long; Chen Ting; Sun Huan-Yao; Huang Yao; Tong Xin; Guan Hua; Gao Ke-Lin

    2015-01-01

    In this paper, we report a method by which the ion quantity is estimated rapidly with an accuracy of 4%. This finding is based on the low-temperature ion density theory and combined with the ion crystal size obtained from experiment with the precision of a micrometer. The method is objective, straightforward, and independent of the molecular dynamics (MD) simulation. The result can be used as the reference for the MD simulation, and the method can improve the reliability and precision of MD simulation. This method is very helpful for intensively studying ion crystal, such as phase transition, spatial configuration, temporal evolution, dynamic character, cooling efficiency, and the temperature limit of the ions. (paper)

  14. Regulative mechanisms of chondrocyte adhesion

    DEFF Research Database (Denmark)

    Schmal, Hagen; Mehlhorn, Alexander T; Fehrenbach, Miriam

    2006-01-01

    Interaction between chondrocytes and extracellular matrix is considered a key factor in the generation of grafts for matrix-associated chondrocyte transplantation. Therefore, our objective was to study the influence of differentiation status on cellular attachment. Adhesion of chondrocytes...... to collagen type II increased after removal from native cartilage up to the third day in monolayer in a dose-dependent manner. Following dedifferentiation after the second passage, adhesion to collagen types I (-84%) and II (-46%) decreased, whereas adhesion to fibrinogen (+59%) and fibronectin (+43......%) increased. A cartilage construct was developed based on a clinically established collagen type I scaffold. In this matrix, more than 80% of the cells could be immobilized by mechanisms of adhesion, filtration, and cell entrapment. Confocal laser microscopy revealed focal adhesion sites as points of cell...

  15. New Arrangement of Dynamic Permeation Method for Determination of Gas Separation Ability of Ionic Liquids

    Czech Academy of Sciences Publication Activity Database

    Řezníčková Čermáková, Jiřina; Suen, S.-Y.; Petričkovič, Roman; Setničková, Kateřina; Luo, Y.-M.; Wagner, Zdeněk; Uchytil, Petr

    2015-01-01

    Roč. 147, JUN 16 (2015), s. 1-8 ISSN 1383-5866 R&D Projects: GA ČR GA104/09/1165 Grant - others:AV ČR(CZ) MOST-15-05 Program:Bilaterální spolupráce Institutional support: RVO:67985858 Keywords : dynamic permeation method * ionic liquid * support arrangement Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 3.299, year: 2015

  16. Dynamics and determinants of credit risk discovery : evidence from CDS and stock markets.

    OpenAIRE

    Chau, F.; Han, C.; Shi, S.

    2018-01-01

    This paper investigates the dynamics and drivers of credit risk discovery between stock and CDS markets in the US. Our research is distinguished from the existing literature in three aspects: 1) we employ an improved method to measure the information share; 2) we discover new drivers of credit risk discovery; and 3) we assess the impact of central clearing counterparty (CCP) on the CDS market. By using the generalized information share (GIS) by Lien and Shrestha (2014), we address the issue t...

  17. Approaches to determining the reliability of a multimodal three-dimensional dynamic signature

    Directory of Open Access Journals (Sweden)

    Yury E. Kozlov

    2018-03-01

    Full Text Available The market of modern mobile applications has increasingly strict requirements for the authentication system reliability. This article examines an authentication method using a multimodal three-dimensional dynamic signature (MTDS, that can be used both as a main and additional method of user authentication in mobile applications. It is based on the use of gesture in the air performed by two independent mobile devices as an identifier. The MTDS method has certain advantages over currently used biometric methods, including fingerprint authentication, face recognition and voice recognition. A multimodal three-dimensional dynamic signature allows quickly changing an authentication gesture, as well as concealing the authentication procedure using gestures that do not attract attention. Despite all its advantages, the MTDS method has certain limitations, the main one is building functionally dynamic complex (FDC skills required for accurate repeating an authentication gesture. To correctly create MTDS need to have a system for assessing the reliability of gestures. Approaches to the solution of this task are grouped in this article according to methods of their implementation. Two of the approaches can be implemented only with the use of a server as a centralized MTDS processing center and one approach can be implemented using smartphone's own computing resources. The final part of the article provides data of testing one of these methods on a template performing the MTDS authentication.

  18. Determining the dynamic range of MCPs based on pore size and strip current

    Science.gov (United States)

    Hunt, C.; Adrian, M. L.; Herrero, F.; James, P.; Jones, H. H.; Rodriguez, M.; Roman, P.; Shappirio, M.

    2010-12-01

    Micro-Channel Plates (MCPs) are used as detectors for almost all detectors measuring particles (both ions, electrons and neutrals) below 30 keV. Recent advances in the manufacturing technology of the MCPs have increased the number of options one has when selecting plates for an instrument. But it is not clear how many of these options affect the performance of the MCPs. In particular the dynamic range is not a clear cut calculation to make from the strip current. There is also some evidence that pore size and coating play a role. We measured the dynamic range and pulse height distribution of MCPs detector chevron stacks with a wide variety of strip currents from the low “normal” range in the EDR range. We also looked at the effects of varying the pore size from 25 microns to 10 microns, partial plating of the MCP surface and coating one surface on each MCP with gold rather than the standard zinc chromium. We will show how the dynamic range and pulse height distributions vary vs. strip current, pore size, and surface plating configurations.

  19. 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.

  20. Adhesive tape exfoliation

    DEFF Research Database (Denmark)

    Bohr, Jakob

    2015-01-01

    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....... In particular on the nature of the surprisingly small number of repetitive steps that are needed in order to obtain a single-layer slab. Two frameworks for exfoliation are investigated: parallel exfoliation involving repetitive simultaneous cleaving, the other, serial exfoliation, which involves the repetitive...... 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....

  1. RAGE controls leukocyte adhesion in preterm and term infants.

    Science.gov (United States)

    Buschmann, Kirsten; Tschada, Raphaela; Metzger, Marie-Sophie; Braach, Natascha; Kuss, Navina; Hudalla, Hannes; Poeschl, Johannes; Frommhold, David

    2014-11-27

    Insufficient leukocyte recruitment may be one reason for the high incidence of life-threatening infections in preterm infants. Since the receptor of advanced glycation end products (RAGE) is a known leukocyte adhesion molecule and highly expressed during early development, we asked whether RAGE plays a role for leukocyte recruitment in preterm and term infants. Leukocyte adhesion was analyzed in dynamic flow chamber experiments using isolated leukocytes of cord blood from extremely premature (35 weeks of gestation) and compared to the results of adults. For fluorescent microscopy leukocytes were labeled with rhodamine 6G. In the respective age groups we also measured the plasma concentration of soluble RAGE (sRAGE) by ELISA and Mac-1 and LFA-1 expression on neutrophils by flow cytometry. The adhesive functions of fetal leukocytes significantly increase with gestational age. In all age groups, leukocyte adhesion was crucially dependent on RAGE. In particular, RAGE was equally effective to mediate leukocyte adhesion when compared to ICAM-1. The plasma levels of sRAGE were high in extremely premature infants and decreased with increasing gestational age. In contrast, expression of β2-Integrins Mac-1 and LFA-1 which are known ligands for RAGE and ICAM-1 did not change during fetal development. We conclude that RAGE is a crucial leukocyte adhesion molecule in both preterm and term infants.

  2. Numerical investigation of adhesion effects on solid particles filtration efficiency

    Science.gov (United States)

    Shaffee, Amira; Luckham, Paul; Matar, Omar K.

    2017-11-01

    Our work investigate the effectiveness of particle filtration process, in particular using a fully-coupled Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM) approach involving poly-dispersed, adhesive solid particles. We found that an increase in particle adhesion reduces solid production through the opening of a wire-wrap type filter. Over time, as particle agglomerates continuously deposit on top of the filter, layer upon layer of particles is built on top of the filter, forming a particle pack. It is observed that with increasing particle adhesion, the pack height build up also increases and hence decreases the average particle volume fraction of the pack. This trend suggests higher porosity and looser packing of solid particles within the pack with increased adhesion. Furthermore, we found that the pressure drop for adhesive case is lower compared to non-adhesive case. Our results suggest agglomerating solid particles has beneficial effects on particle filtration. One important application of these findings is towards designing and optimizing sand control process for a hydrocarbon well with excessive sand production which is major challenge in oil and gas industry. Funding from PETRONAS and RAEng UK for Research Chair (OKM) gratefully acknowledged.

  3. 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...

  4. Embryonic cell-cell adhesion: a key player in collective neural crest migration.

    Science.gov (United States)

    Barriga, Elias H; Mayor, Roberto

    2015-01-01

    Cell migration is essential for morphogenesis, adult tissue remodeling, wound healing, and cancer cell migration. Cells can migrate as individuals or groups. When cells migrate in groups, cell-cell interactions are crucial in order to promote the coordinated behavior, essential for collective migration. Interestingly, recent evidence has shown that cell-cell interactions are also important for establishing and maintaining the directionality of these migratory events. We focus on neural crest cells, as they possess extraordinary migratory capabilities that allow them to migrate and colonize tissues all over the embryo. Neural crest cells undergo an epithelial-to-mesenchymal transition at the same time than perform directional collective migration. Cell-cell adhesion has been shown to be an important source of planar cell polarity and cell coordination during collective movement. We also review molecular mechanisms underlying cadherin turnover, showing how the modulation and dynamics of cell-cell adhesions are crucial in order to maintain tissue integrity and collective migration in vivo. We conclude that cell-cell adhesion during embryo development cannot be considered as simple passive resistance to force, but rather participates in signaling events that determine important cell behaviors required for cell migration. © 2015 Elsevier Inc. All rights reserved.

  5. 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.

  6. Determination of Fatty Acid Metabolism with Dynamic [11C]Palmitate Positron Emission Tomography of Mouse Heart In Vivo

    Directory of Open Access Journals (Sweden)

    Yinlin Li

    2015-09-01

    Full Text Available The goal of this study was to establish a quantitative method for measuring fatty acid (FA metabolism with partial volume (PV and spill-over (SP corrections using dynamic [11C]palmitate positron emission tomographic (PET images of mouse heart in vivo. Twenty-minute dynamic [11C]palmitate PET scans of four 18- to 20-week-old male C57BL/6 mice under isoflurane anesthesia were performed using a Focus F-120 PET scanner. A model-corrected blood input function, 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 four-compartment tracer kinetic model, was used to determine rates of myocardial fatty acid oxidation (MFAO, myocardial FA esterification, myocardial FA use, and myocardial FA uptake. The MFAO thus measured in C57BL/6 mice was 375.03 ± 43.83 nmol/min/g. This compares well to the MFAO measured in perfused working C57BL/6 mouse hearts ex vivo of about 350 nmol/g/min and 400 nmol/min/g. FA metabolism was measured for the first time in mouse heart in vivo using dynamic [11C]palmitate PET in a four-compartment tracer kinetic model. MFAO obtained with this model was validated by results previously obtained with mouse hearts ex vivo.

  7. Investigations on the viscoelastic performance of pressure sensitive adhesives in drug-in-adhesive type transdermal films.

    Science.gov (United States)

    Wolff, Hans-Michael; Irsan; Dodou, Kalliopi

    2014-08-01

    We aimed to investigate the effect of solubility parameter and drug concentration on the rheological behaviour of drug-in-adhesive films intended for transdermal application. Films were prepared over a range of drug concentrations (5%, 10% and 20% w/w) using ibuprofen, benzoic acid, nicotinic acid and lidocaine as model drugs in acrylic (Duro-Tak 87-4287 and Duro-Tak 87900A) or silicone (Bio-PSA 7-4301 and Bio-PSA 7-4302) pressure sensitive adhesives (PSAs). Saturation status of films was determined using light microscopy. Viscoelastic parameters were measured in rheology tests at 32°C. Subsaturated films had lower viscoelastic moduli whereas saturated films had higher moduli than the placebo films and/or a concentration-dependent increase in their modulus. Saturation concentration of each drug in the films was reflected by decreasing/increasing viscoelastic patterns. The viscoelastic windows (VWs) of the adhesive and drug-in-adhesive films clearly depicted the effect of solubility parameter differences, molar concentration of drug in the adhesive film and differences in PSA chemistry. Drug solubility parameters and molar drug concentrations have an impact on rheological patterns and thus on the adhesive performance of tested pressure sensitive adhesives intended for use in transdermal drug delivery systems. Use of the Flory equation in its limiting form was appropriate to predict drug solubility in the tested formulations.

  8. Competition between adhesion and inertia during stick-slip peeling of Pressure Sensitive Adhesives

    Science.gov (United States)

    Dalbe, M.-J.; Villey, R.; Ciccotti, M.; Cortet, P.-P.; Santucci, S.; Vanel, L.

    2015-03-01

    We consider the classical problem of the instable stick-slip dynamics often observed when peeling a pressure sensitive adhesive, quantifying for the first time experimentally the influence of the peeling angle. This instability is known to be the consequence of a decreasing fracture energy of the adhesive-substrate joint over a certain range of driving velocity: we focus here on the important case where the instability develops at large driving velocity. We show that the shape of the peeling front velocity fluctuations progressively changes from typical stick-slip relaxation oscillations to nearly sinusoidal oscillations as the peeling angle and/or the driving velocity is increased. This transition is accompanied with a change in the dependencies of the limit cycles' period on the control parameters. We show that it results from the competition, in the dynamical equation, between the standard fracture energy and a term -considered here for the first time- associated to the freestanding tape elasticity and inertia. We manage to predict quantitatively the transition of the instability amplitude and period from the classical Barquins-Maugis quasistatic regime to a purely inertial regime in which the adhesion energy is no more at play in setting the instability limit cycles.

  9. Wet adhesion and adhesive locomotion of snails on anti-adhesive non-wetting surfaces.

    Directory of Open Access Journals (Sweden)

    Neil J Shirtcliffe

    Full Text Available Creating surfaces capable of resisting liquid-mediated adhesion is extremely difficult due to the strong capillary forces that exist between surfaces. Land snails use this to adhere to and traverse across almost any type of solid surface of any orientation (horizontal, vertical or inverted, texture (smooth, rough or granular or wetting property (hydrophilic or hydrophobic via a layer of mucus. However, the wetting properties that enable snails to generate strong temporary attachment and the effectiveness of this adhesive locomotion on modern super-slippy superhydrophobic surfaces are unclear. Here we report that snail adhesion overcomes a wide range of these microscale and nanoscale topographically structured non-stick surfaces. For the one surface which we found to be snail resistant, we show that the effect is correlated with the wetting response of the surface to a weak surfactant. Our results elucidate some critical wetting factors for the design of anti-adhesive and bio-adhesion resistant surfaces.

  10. Wet adhesion and adhesive locomotion of snails on anti-adhesive non-wetting surfaces.

    Science.gov (United States)

    Shirtcliffe, Neil J; McHale, Glen; Newton, Michael I

    2012-01-01

    Creating surfaces capable of resisting liquid-mediated adhesion is extremely difficult due to the strong capillary forces that exist between surfaces. Land snails use this to adhere to and traverse across almost any type of solid surface of any orientation (horizontal, vertical or inverted), texture (smooth, rough or granular) or wetting property (hydrophilic or hydrophobic) via a layer of mucus. However, the wetting properties that enable snails to generate strong temporary attachment and the effectiveness of this adhesive locomotion on modern super-slippy superhydrophobic surfaces are unclear. Here we report that snail adhesion overcomes a wide range of these microscale and nanoscale topographically structured non-stick surfaces. For the one surface which we found to be snail resistant, we show that the effect is correlated with the wetting response of the surface to a weak surfactant. Our results elucidate some critical wetting factors for the design of anti-adhesive and bio-adhesion resistant surfaces.

  11. Low Impedance Carbon Adhesive Electrodes with Long Shelf Life.

    Science.gov (United States)

    Posada-Quintero, Hugo F; Reyes, Bersaín A; Burnham, Ken; Pennace, John; Chon, Ki H

    2015-10-01

    A novel electrocardiogram (ECG) electrode film is developed by mixing carbon black powder and a quaternary salt with a visco-elastic polymeric adhesive. Unlike traditional wet gel-based electrodes, carbon/salt/adhesive (CSA) electrodes should theoretically have an infinite shelf life as they do not dehydrate even after a prolonged period of storage. The CSA electrodes are electrically activated for use through the process of electrophoresis. Specifically, the activation procedure involves sending a high voltage and current through the electrode, which results in significant reduction of impedance so that high fidelity ECG signals can be obtained. Using the activation procedure, the ideal concentration of carbon black powder in the mixture with the adhesive was examined. It was determined that the optimum concentration of carbon black which minimized post-activation impedance was 10%. Once the optimal carbon black powder concentration was determined, extensive signal analysis was performed to compare the performance of the CSA electrodes to the standard silver-silver chloride (Ag/AgCl) electrodes. As a part of data analysis, electrode-skin contact impedance of the CSA was measured and compared to the standard Ag/AgCl electrodes; we found consistently lower impedance for CSA electrodes. For quantitative data analysis, we simultaneously collected ECG data with CSA and Ag/AgCl electrodes from 17 healthy subjects. Heart rate variability (HRV) indices and ECG morphological waveforms were calculated to compare CSA and Ag/AgCl electrodes. Non-significant differences for most of the HRV indices between CSA and Ag/AgCl electrodes were found. Of the morphological waveform metrics consisting of R-wave peak amplitude, ST-segment elevation and QT interval, only the first index was found to be significantly different between the two media. The response of CSA electrodes to motion artifacts was also tested, and we found in general no difference in the quality of the ECG signal

  12. Possible dynamical determination of m$_{t}$, m$_{b}$ and m$_{\\tau}$

    CERN Document Server

    Kounnas, Costas; Ridolfi, G; Zwirner, Fabio; Kounnas, Costas; Pavel, Ilarion; Ridolfi, Giovanni; Zwirner, Fabio

    1995-01-01

    Motivated by four-dimensional superstring models, we consider the possibility of treating the Yukawa couplings of the Minimal Supersymmetric Standard Model (MSSM) as dynamical variables of the effective theory at the electroweak scale. Assuming bottom-tau unification, we concentrate on the top and bottom Yukawa couplings, and find that minimizing the effective potential drives them close to an effective infrared fixed line. Requiring an acceptable bottom-top mass ratio leads in principle to an additional constraint on the MSSM parameter space. As a by-product, we give new approximate analytical solutions of the renormalization group equations for the MSSM parameters.

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

    OpenAIRE

    Almenara, J. M.; Díaz, R. F.; 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 o...

  14. Comparison of two methods to determine fan performance curves using computational fluid dynamics

    Science.gov (United States)

    Onma, Patinya; Chantrasmi, Tonkid

    2018-01-01

    This work investigates a systematic numerical approach that employs Computational Fluid Dynamics (CFD) to obtain performance curves of a backward-curved centrifugal fan. Generating the performance curves requires a number of three-dimensional simulations with varying system loads at a fixed rotational speed. Two methods were used and their results compared to experimental data. The first method incrementally changes the mass flow late through the inlet boundary condition while the second method utilizes a series of meshes representing the physical damper blade at various angles. The generated performance curves from both methods are compared with an experiment setup in accordance with the AMCA fan performance testing standard.

  15. Humidity dependence of adhesion for silane coated microcantilevers

    International Nuclear Information System (INIS)

    De Boer, Maarten P.; Mayer, Thomas M.; Carpick, Robert W.; Michalske, Terry A.; Srinivasan, U.; Maboudian, R.

    1999-01-01

    This study examines adhesion between silane-coated micromachined surfaces that are exposed to humid conditions. Our quantitative values for interfacial adhesion energies are determined from an in-situ optical measurement of deformations in partly-adhered cantilever beams. We coated micromachined cantilevers with either ODTS (C(sub 18)H(sub 37)SiCl(sub 3)) or FDTS (C(sub 8)F(sub 17)C(sub 2)H(sub 4)SiCl(sub 3)) with the objective of creating hydrophobic surfaces whose adhesion would be independent of humidity. In both cases, the adhesion energy is significantly lower than for uncoated, hydrophilic surfaces. For relative humidities (RH) less than 95% (ODTS) and 80% (FDTS) the adhesion energy was extremely low and constant. In fact, ODTS-coated beams exposed to saturated humidity conditions and long (48 hour) exposures showed only a factor of two increase in adhesion energy. Surprisingly, FDTS coated beams, which initially have a higher contact angle (115(degree)) with water than do ODTS coated beams (112(degree)), proved to be much more sensitive to humidity. The FDTS coated surfaces showed a factor of one hundred increase in adhesion energy after a seven hour exposure to 90% RH. Atomic force microscopy revealed agglomerated coating material after exposed to high RH, suggesting a redistribution of the monolayer film. This agglomeration was more prominent for FDTS than ODTS. These findings suggest a new mechanism for uptake of moisture under high humidity conditions. At high humidities, the silane coatings can reconfigure from a surface to a bulk phase leaving behind locally hydrophilic sites which increase the average measured adhesion energy. In order for the adhesion increase to be observed, a significant fraction of the monolayer must be converted from the surface to the bulk phase

  16. Determination of polychlorinated biphenyls in water using dynamic hollow fiber liquid-phase microextraction and gas chromatography-mass spectrometry.

    Science.gov (United States)

    Li, Guanhua; Zhang, Lijun; Zhang, Zhanen

    2008-09-12

    The application of dynamic hollow fiber liquid-phase microextraction (dynamic HF-LPME) and gas chromatography-mass spectrometry (GC-MS) for the determination of trace amounts of polychlorinated biphenyls (PCBs) in water was investigated. The experimental parameters were optimized. Under the optimum conditions, the concentration enrichment factors for PCBs were from 718-fold to 840-fold. The calibration curves were linear over a range of 0.05-90 microg/L, with a correlation coefficient (r(2)) of 0.9957-0.9979. The relative standard deviation (RSD) ranged from 3.4% to 5.8% for intra-day variation and from 4.1% to 7.3% for inter-day variation. The limits of detection (LODs, S/N=3:1) were in the range of 13-41 ng/L. The recoveries for spiked water samples ranged from 85.9% to 92.0%.

  17. 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.

  18. NEXT GENERATION OF TELESCOPES OR DYNAMICS REQUIRED TO DETERMINE IF EXO-MOONS HAVE PROGRADE OR RETROGRADE ORBITS

    International Nuclear Information System (INIS)

    Lewis, Karen M.; Fujii, Yuka

    2014-01-01

    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

  19. Determination of Young's Modulus of Carbon Nanotube Using Molecular Dynamics (MDSS) Simulation

    National Research Council Canada - National Science Library

    Oh, Jung

    2003-01-01

    .... The empirical Tersoff-Brenner potential and freestanding thermal vibration methods proposed by Krishnan et al were used to determine interatomic forces and rms displacements of carbon atoms at room temperature 300 K...

  20. Marine Bioinspired Underwater Contact Adhesion.

    Science.gov (United States)

    Clancy, Sean K; Sodano, Antonio; Cunningham, Dylan J; Huang, Sharon S; Zalicki, Piotr J; Shin, Seunghan; Ahn, B Kollbe

    2016-05-09

    Marine mussels and barnacles are sessile biofouling organisms that adhere to a number of surfaces in wet environments and maintain remarkably strong bonds. Previous synthetic approaches to mimic biological wet adhesive properties have focused mainly on the catechol moiety, present in mussel foot proteins (mfps), and especially rich in the interfacial mfps, for example, mfp-3 and -5, found at the interface between the mussel plaque and substrate. Barnacles, however, do not use Dopa for their wet adhesion, but are instead rich in noncatecholic aromatic residues. Due to this anomaly, we were intrigued to study the initial contact adhesion properties of copolymerized acrylate films containing the key functionalities of barnacle cement proteins and interfacial mfps, for example, aromatic (catecholic or noncatecholic), cationic, anionic, and nonpolar residues. The initial wet contact adhesion of the copolymers was measured using a probe tack testing apparatus with a flat-punch contact geometry. The wet contact adhesion of an optimized, bioinspired copolymer film was ∼15.0 N/cm(2) in deionized water and ∼9.0 N/cm(2) in artificial seawater, up to 150 times greater than commercial pressure-sensitive adhesive (PSA) tapes (∼0.1 N/cm(2)). Furthermore, maximum wet contact adhesion was obtained at ∼pH 7, suggesting viability for biomedical applications.

  1. The role of riparian vegetation density, channel orientation and water velocity in determining river temperature dynamics

    Science.gov (United States)

    Garner, Grace; Malcolm, Iain A.; Sadler, Jonathan P.; Hannah, David M.

    2017-10-01

    A simulation experiment was used to understand the importance of riparian vegetation density, channel orientation and flow velocity for stream energy budgets and river temperature dynamics. Water temperature and meteorological observations were obtained in addition to hemispherical photographs along a ∼1 km reach of the Girnock Burn, a tributary of the Aberdeenshire Dee, Scotland. Data from nine hemispherical images (representing different uniform canopy density scenarios) were used to parameterise a deterministic net radiation model and simulate radiative fluxes. For each vegetation scenario, the effects of eight channel orientations were investigated by changing the position of north at 45° intervals in each hemispheric image. Simulated radiative fluxes and observed turbulent fluxes drove a high-resolution water temperature model of the reach. Simulations were performed under low and high water velocity scenarios. Both velocity scenarios yielded decreases in mean (≥1.6 °C) and maximum (≥3.0 °C) temperature as canopy density increased. Slow-flowing water resided longer within the reach, which enhanced heat accumulation and dissipation, and drove higher maximum and lower minimum temperatures. Intermediate levels of shade produced highly variable energy flux and water temperature dynamics depending on the channel orientation and thus the time of day when the channel was shaded. We demonstrate that in many reaches relatively sparse but strategically located vegetation could produce substantial reductions in maximum temperature and suggest that these criteria are used to inform future river management.

  2. Demographic and Socio-economic Determinants of Birth Interval Dynamics in Manipur: A Survival Analysis

    OpenAIRE

    Singh, Sanajaoba N; Singh, Sharat N; Narendra, RK

    2011-01-01

    The birth interval is a major determinant of levels of fertility in high fertility populations. A house-to-house survey of 1225 women in Manipur, a tiny state in North Eastern India was carried out to investigate birth interval patterns and its determinants. Using survival analysis, among the nine explanatory variables of interest, only three factors – infant mortality, Lactation and use of contraceptive devices have highly significant effect (P

  3. Modeling the motion of non-adhesive and adhesive capsules through channels with posts

    Science.gov (United States)

    Zhu, Guangdong; Alexeev, Alexander; Balazs, Anna

    2007-03-01

    We study numerically the motion of compliant microcapsules in microchannels. These microchannels have two adhesive posts on the walls that form an orifice with a separation distance roughly comparable in size to the diameter of the capsules. Each microcapsule consists of an elastic shell that is filled with a viscous fluid. The capsules model synthetic polymeric microcapsules or biological cells, such as leukocytes. The microcapsules are driven to move through the channels by an imposed pressure gradient. To model this multi-component system, we combine the lattice Boltzmann model for fluid dynamics and the lattice spring model for the micromechanics of elastic solids. We probe the effect of capsule stiffness and adhesion between the posts and capsule on the motion of capsules within the channel.

  4. TANNIN ADHESIVES AS AN ALTENATIVE TO THE SYNTHETIC PHENOLIC ADHESIVES

    Directory of Open Access Journals (Sweden)

    Semra Çolak

    2003-04-01

    Full Text Available Recently, increasing attention has been paid industrially to the use of tannin formaldehyde adhesives in production of wood based panel products such as particleboard, fiber board and plywood. The researches on the use of tannin extracts as a wood adhesive started in 1950, however, they proceeded very slowly since the problems associated with the application of them. The idea which tannin extract can be used replace the oil-based phenolic adhesive was the base of several studies after the oil crisis of the 1970s. In the past, the economical aspects were important in the researches on the tannin-based adhesives. Nowadays, however, both economical and ecological factors should have taken into consideration in wood bonding.

  5. Adhesive properties of PTFE modified by DC discharge

    Science.gov (United States)

    Gilman, A.; Piskarev, M.; Yablokov, M.; Kechek'yan, A.; Kuznetsov, A.

    2014-06-01

    It is shown that low-pressure DC discharge treatment of PTFE films at both the anode and cathode leads to substantial enhancement of the contact properties of the polymer surface and alters considerably the adhesion properties of PTFE film surface. A procedure is developed for determination the adhesion characteristics of the modified surface of plasma treated thin polymer films using Scotch® 810 adhesive tape. The procedure comprises of a study of the surface coating created by means of physical vapor deposition of an aluminum layer with thickness of the order of 100 nm, an adhesive joint of the film with Scotch® 810 tape, and T-peel testing of the specimen. Using this procedure, the peel resistance of the initial and the modified PTFE film on both the anode and the cathode in DC discharge is measured.

  6. 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.

  7. Structural adhesives directory and databook

    CERN Document Server

    Wilson, Jo

    1996-01-01

    A worldwide directory of commercially available adhesive products for use in a wide range of engineering disciplines. Along with product names and suppliers, basic property data are tabulated and cross-referenced. The book is subdivided according to class of adhesive, with introductions to each class followed by comparison tables and datasheets for each adhesive. The datasheets contain detailed information, from product codes to environmental properties and are therefore of interest across a broad readership. Standardized data will aid the user in cross-comparison between different manufacturers and in easily identifying the required information.

  8. 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.

  9. Adhesion of laser deposited films

    International Nuclear Information System (INIS)

    Zhovannik, E.V.; Nikolaev, I.N.; Utochkin, Yu.A.; Stavkin, D.G.

    1996-01-01

    The method of thin solid films (Ni, Cu, Al, Pd, Si, InSb, Ta 2 O 5 ) formation on different substrates (Cu, Fe, Si, SiO 2 , Ta 2 O 5 , carbon, glass, mica, teflon) with higher adhesion strength (∼ 10 7 Pa) without preliminary treatment of substrate surface was discribed. The method is based on laser evaporation of solid in vacuum. Adhesion was measured by means of a direct pull technique using a pin soldered to buffer film evaporated by laser on the investigated film. Possible reasons for higher adhesion of films fabricated by laser deposition were discussed. 10 refs.; 3 figs

  10. Adhesives from modified soy protein

    Science.gov (United States)

    Sun, Susan [Manhattan, KS; Wang, Donghai [Manhattan, KS; Zhong, Zhikai [Manhattan, KS; Yang, Guang [Shanghai, CN

    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.

  11. A Review of Cell Adhesion Studies for Biomedical and Biological Applications

    Science.gov (United States)

    Ahmad Khalili, Amelia; Ahmad, Mohd Ridzuan

    2015-01-01

    Cell adhesion is essential in cell communication and regulation, and is of fundamental importance in the development and maintenance of tissues. The mechanical interactions between a cell and its extracellular matrix (ECM) can influence and control cell behavior and function. The essential function of cell adhesion has created tremendous interests in developing methods for measuring and studying cell adhesion properties. The study of cell adhesion could be categorized into cell adhesion attachment and detachment events. The study of cell adhesion has been widely explored via both events for many important purposes in cellular biology, biomedical, and engineering fields. Cell adhesion attachment and detachment events could be further grouped into the cell population and single cell approach. Various techniques to measure cell adhesion have been applied to many fields of study in order to gain understanding of cell signaling pathways, biomaterial studies for implantable sensors, artificial bone and tooth replacement, the development of tissue-on-a-chip and organ-on-a-chip in tissue engineering, the effects of biochemical treatments and environmental stimuli to the cell adhesion, the potential of drug treatments, cancer metastasis study, and the determination of the adhesion properties of normal and cancerous cells. This review discussed the overview of the available methods to study cell adhesion through attachment and detachment events. PMID:26251901

  12. AFM measurements of adhesive forces between carbonaceous particles and the substrates

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Tianqi [Institute of Nuclear and New Energy Technology of Tsinghua University, Collaborative Innovation Center of Advanced Nuclear Energy Technology, Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education, Beijing 100084 (China); Peng, Wei, E-mail: pengwei@tsinghua.edu.cn [Institute of Nuclear and New Energy Technology of Tsinghua University, Collaborative Innovation Center of Advanced Nuclear Energy Technology, Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education, Beijing 100084 (China); Shen, Ke [Institute of Nuclear and New Energy Technology of Tsinghua University, Collaborative Innovation Center of Advanced Nuclear Energy Technology, Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education, Beijing 100084 (China); Yu, Suyuan, E-mail: suyuan@tsinghua.edu.cn [Center for Combustion Energy, Key Laboratory for Thermal Science and Power Engineering of Ministry of Educations, Department of Thermal Engineering, Tsinghua University, Beijing 100084 (China)

    2015-11-15

    Highlights: • Adhesive force of spherical carbonaceous particle MCMBs and HTR-10 graphite matrix debris were measured for the first time. • The measured equivalent works of adhesion were much smaller than the ideal values. • The shape factor and the particle morphology reduce the adhesive force. • The adhesion effect does not change directly with the asperity size. - Abstract: Graphite dust is carbonaceous particles generated during operation of High Temperature Gas-Cooled Reactors (HTR). Graphite dust resuspension is the key behavior associated with HTR source term analyses and environmental safety assessment. The adhesive force is the key factor that determines the resuspension rate. The present study used an atomic force microscope (AFM) to measure the adhesive force between a single carbonaceous particle and the substrate. The measurements were performed on mica, graphite IG110 and Inconel 800H. The prepared “probe cantilevers” were mesocarbon microbeads (MCMB), fuel element debris from HTR-10 and graphite NBG18. The equivalent work of adhesion was derived from the measured adhesive force and calculated based on substrate profile approximation and the JKR theoretical model. The measured work was smaller than the ideal work of adhesion, most likely due to the rough particle morphology and the rough substrate surface. Additionally, a shape factor imposes a constraint on the lateral deformation of the particles. Furthermore, surface roughness could reduce the adhesive force some depending on the particle size. Once the particle was too small to be trapped into a trough, the adhesive force would not be further reduced.

  13. Biomaterial based novel polyurethane adhesives for wood to wood and metal to metal bonding

    Directory of Open Access Journals (Sweden)

    Mitesh Ramanlal Patel

    2009-01-01

    Full Text Available Polyurethane adhesives made from synthetic chemicals are non-biodegradable, costly and difficult to find raw materials from local market. To avoid solid pollution problem, cost effectiveness and easy availability of raw materials, biomaterials based polyurethane adhesives are used in current industrial interest. Direct use of castor oil in polyurethane adhesive gives limited hardness. Modification on active sites of castor oil to utilize double bond of unsaturated fatty acid and carboxyl group yields new modified or activated polyols, which can be utilized for polyurethane adhesive formulation. In view of this, we have synthesized polyurethane adhesives from polyester polyols, castor oil based polyols and epoxy based polyols with Isocyanate adducts based on castor oil and trimethylolpropane. To study the effects of polyurethane adhesive strength (i.e. lap shear strength on wood-to-wood and metal-to-metal bonding through various types of polyols, cross-linking density, isocyanate adducts and also to compare adhesive strength between wood to wood and metal to metal surface. These polyols and polyurethanes were characterized through GPC, NMR and IR-spectroscopy, gel and surface drying time. Thermal stability of PU adhesives was determined under the effect of cross-linking density (NCO/OH ratio. The NCO/OH ratio (1.5 was optimized for adhesives as the higher NCO/OH ratio (2.0 increasing cross-linking density and decreases adhesion. Lower NCO/OH ratio (1.0 provideslow cross-linking density and low strength of adhesives.

  14. A Review of Cell Adhesion Studies for Biomedical and Biological Applications

    Directory of Open Access Journals (Sweden)

    Amelia Ahmad Khalili

    2015-08-01

    Full Text Available Cell adhesion is essential in cell communication and regulation, and is of fundamental importance in the development and maintenance of tissues. The mechanical interactions between a cell and its extracellular matrix (ECM can influence and control cell behavior and function. The essential function of cell adhesion has created tremendous interests in developing methods for measuring and studying cell adhesion properties. The study of cell adhesion could be categorized into cell adhesion attachment and detachment events. The study of cell adhesion has been widely explored via both events for many important purposes in cellular biology, biomedical, and engineering fields. Cell adhesion attachment and detachment events could be further grouped into the cell population and single cell approach. Various techniques to measure cell adhesion have been applied to many fields of study in order to gain understanding of cell signaling pathways, biomaterial studies for implantable sensors, artificial bone and tooth replacement, the development of tissue-on-a-chip and organ-on-a-chip in tissue engineering, the effects of biochemical treatments and environmental stimuli to the cell adhesion, the potential of drug treatments, cancer metastasis study, and the determination of the adhesion properties of normal and cancerous cells. This review discussed the overview of the available methods to study cell adhesion through attachment and detachment events.

  15. Comparing Soy Flour Wood Adhesives to Purified Soy Protein Adhesives

    Science.gov (United States)

    Charles R. Frihart; Linda F. Lorenz

    2013-01-01

    While economics dictate that soy-based wood adhesives be made with soy flour, much of the recent literature on soy-based wood adhesives has involved using soy protein isolate. The obvious assumption is that the additional carbohydrates in the flour but not in the isolate only serve as inert diluents. Our studies have shown that the isolate can provide 10 times the wet...

  16. 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

    2014-11-08

    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.

  17. Hydrogen partitioning in pure cast aluminum as determined by dynamic evolution rate measurements

    Science.gov (United States)

    Outlaw, R. A.; Peterson, D. T.; Schmidt, F. A.

    1981-01-01

    Hydrogen in pure aluminum can be found in two different states. One is related to a presence in gas-filled pores, while the other state involves the formation of a solid solution between hydrogen and aluminum. The considered investigation is concerned with the distribution of the hydrogen between various states. A dynamic technique is employed to measure the evolution of hydrogen from commercially available samples of polycrystalline pure aluminum under ultrahigh vacuum conditions. The obtained data are compared with the results of a statistical analysis concerning the porosity in the cast aluminum. It was found that more than 99 pct of the hydrogen in the aluminum is located in large pores. Less than 1 pct of the hydrogen is partitioned between the solid solution and the small pores.

  18. Dynamic magnetic resonance imaging in determining histopathological prognostic factors of invasive breast cancers

    International Nuclear Information System (INIS)

    Tuncbilek, Nermin; Karakas, Hakki Muammer; Okten, Ozerk Omur

    2005-01-01

    Objective: To evaluate the relation between morphological features and enhancement parameters in dynamic contrast-enhanced magnetic resonance (DCE-MR) imaging with histopathological prognostic factors. Materials and methods: Fifty-five patients with surgicopathological diagnosis of breast carcinoma were evaluated with 1.0 T MR scanner as a part of their preoperative diagnostic work-up. Dynamic studies were performed in axial plane using 3D fast low angle shot (FLASH) sequence. Time intensity curves (TICs) were obtained from the regions showing maximal enhancement in subtraction images. The correlations between enhancement parameters and histopathological findings were analyzed using stepwise multiple regression analysis, Student's t-test, χ 2 -tests and Pearson's moment correlation coefficient. Results: Significant correlations were found between the presence of lymph node metastasis and tumor size (P<0.05) and edge characteristics (P<0.05). A highly significant correlation was found between histopathological grades and qualitative enhancement patterns (r=0.403, P<0.01). Statistically significant differences were found between the groups with and without lymph node metastasis regarding enhancement in the first minute (P<0.01) and TIC slope (P<0.05). A significant difference was found between the histopathological grades I and III regarding all quantitative enhancement parameters, whereas no difference was found between the grades I-II, and II-III. Conclusion: DCE-MR imaging helps to predict prognostic factors of breast cancer by revealing morphological features and enhancement parameters of the primary tumor. Additional morphological factors further improve our ability to predict lymphatic metastasis

  19. Dynamical patterning modules: physico-genetic determinants of morphological development and evolution

    International Nuclear Information System (INIS)

    Newman, Stuart A; Bhat, Ramray

    2008-01-01

    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

  20. 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

  1. Dynamic Electrochemistry Corrects for Hematocrit Interference on Blood Glucose Determinations with Patient Self-Measurement Devices

    Science.gov (United States)

    Musholt, Petra B; Schipper, Christina; Thomé, Nicole; Ramljak, Sanja; Schmidt, Marc; Forst, Thomas; Pfützner, Andreas

    2011-01-01

    Background It has been demonstrated that dynamic electrochemistry can be used to correct blood glucose measurement results for potentially interfering conditions, such as humidity, hematocrit (HCT) variations, and ascorbic acid. The purpose of this laboratory investigation was to assess the potential influence of hematocrit variations on a variety of blood glucose meters applying different measurement technologies. Methods Venous heparinized whole blood was drawn, immediately aliquoted, and manipulated to contain three different blood glucose concentrations (80, 155, and 310 mg/dl) and five different hematocrit levels (25%, 37%, 45%, 52%, and 60%). After careful oxygenation to normal blood oxygen pressure, each of the resulting 15 different samples was measured 8 times with the following devices: BGStar, Contour, Accu-Chek Aviva, Accu-Chek Aviva Nano, Breeze 2, Precision Xceed, OneTouch Ultra 2, OneTouch Verio, FreeStyle Freedom Lite, Glucocard G+, GlucoMen LX, GlucoMen GM, and StatStrip [point-of-care (POC) device]. Cobas (Roche Diagnostics, glucose hexokinase method) served as laboratory plasma reference method. Stability to hematocrit influence was assumed when less than 10% bias occurred between the highest and lowest hematocrit levels when analyzing mean deviations for all three glucose concentrations. Results Besides the POC StatStrip device, which is known to measure and correct for hematocrit (resulting in hematocrit variations occur in daily routine (e.g., because of smoking, exercise, hypermenorrhea, pregnancy, stay in mountains, and hemodialysis), our results may encourage use of meters with stable performance under these conditions. Dynamic electrochemistry as used in the BGStar device (sanofi-aventis) appears to be an effective technology to correct for potential hematocrit influence on the meter results. PMID:22027312

  2. Bacterial endotoxin adhesion to different types of orthodontic adhesives

    Directory of Open Access Journals (Sweden)

    Priscilla Coutinho ROMUALDO

    Full Text Available Abstract Bacterial endotoxin (LPS adhesion to orthodontic brackets is a known contributing factor to inflammation of the adjacent gingival tissues. Objective The aim of this study was to assess whether LPS adheres to orthodontic adhesive systems, comparing two commercial brands. Material and Methods Forty specimens were fabricated from Transbond XT and Light Bond composite and bonding agent components (n=10/component, then contaminated by immersion in a bacterial endotoxin solution. Contaminated and non-contaminated acrylic resin samples were used as positive and negative control groups, respectively. LPS quantification was performed by the Limulus Amebocyte Lysate QCL-1000™ test. Data obtained were scored and subjected to the Chi-square test using a significance level of 5%. Results There was endotoxin adhesion to all materials (p0.05. There was no significant difference (p>0.05 among commercial brands. Affinity of endotoxin was significantly greater for the bonding agents (p=0.0025. Conclusions LPS adhered to both orthodontic adhesive systems. Regardless of the brand, the endotoxin had higher affinity for the bonding agents than for the composites. There is no previous study assessing the affinity of LPS for orthodontic adhesive systems. This study revealed that LPS adheres to orthodontic adhesive systems. Therefore, additional care is recommended to orthodontic applications of these materials.

  3. Demographic and Socio-economic Determinants of Birth Interval Dynamics in Manipur: A Survival Analysis

    Directory of Open Access Journals (Sweden)

    Sanajaoba Singh N,

    2011-01-01

    Full Text Available The birth interval is a major determinant of levels of fertility in high fertility populations. A house-to-house survey of 1225 women in Manipur, a tiny state in North Eastern India was carried out to investigate birth interval patterns and its determinants. Using survival analysis, among the nine explanatory variables of interest, only three factors – infant mortality, Lactation and use of contraceptive devices have highly significant effect (P<0.01 on the duration of birth interval and only three factors – age at marriage of wife, parity and sex of child are found to be significant (P<0.05 on the duration variable.

  4. Determination of the absolute binding free energies of HIV-1 protease inhibitors using non-equilibrium molecular dynamics simulations

    Science.gov (United States)

    Ngo, Son Tung; Nguyen, Minh Tung; Nguyen, Minh Tho

    2017-05-01

    The absolute binding free energy of an inhibitor to HIV-1 Protease (PR) was determined throughout evaluation of the non-bonded interaction energy difference between the two bound and unbound states of the inhibitor and surrounding molecules by the fast pulling of ligand (FPL) process using non-equilibrium molecular dynamics (NEMD) simulations. The calculated free energy difference terms help clarifying the nature of the binding. Theoretical binding affinities are in good correlation with experimental data, with R = 0.89. The paradigm used is able to rank two inhibitors having the maximum difference of ∼1.5 kcal/mol in absolute binding free energies.

  5. 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

  6. Epidemiology, determinants and dynamics of cholera in pakistan: gaps and prospects for future research

    International Nuclear Information System (INIS)

    Naseer, M.; Jamali, T.

    2014-01-01

    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. (author)

  7. Adhesive capsulitis: a review.

    Science.gov (United States)

    Ewald, Anthony

    2011-02-15

    Adhesive capsulitis is a common, yet poorly understood, condition causing pain and loss of range of motion in the shoulder. It can occur in isolation or concomitantly with other shoulder conditions (e.g., rotator cuff tendinopathy, bursitis) or diabetes mellitus. It is often self-limited, but can persist for years and may never fully resolve. The diagnosis is usually clinical, although imaging can help rule out other conditions. The differential diagnosis includes acromioclavicular arthropathy, autoimmune disease (e.g., systemic lupus erythematosus, rheumatoid arthritis), biceps tendinopathy, glenohumeral osteoarthritis, neoplasm, rotator cuff tendinopathy or tear (with or without impingement), and subacromial and subdeltoid bursitis. Several treatment options are commonly used, but few have high-level evidence to support them. Because the condition is often self-limited, observation and reassurance may be considered; however, this may not be acceptable to many patients because of the painful and debilitating nature of the condition. Nonsurgical treatments include analgesics (e.g., acetaminophen, nonsteroidal anti-inflammatory drugs), oral prednisone, and intra-articular corticosteroid injections. Home exercise regimens and physical therapy are often prescribed. Surgical treatments include manipulation of the joint under anesthesia and capsular release.

  8. Underwater adhesion: The barnacle way

    Digital Repository Service at National Institute of Oceanography (India)

    Khandeparker, L.; Anil, A.C.

    silicone substrata. For both materials, significant variation among maternal families in the proportion of barnacles producing a thick adhesive plaque was observed, which suggests the presence of genetic variation, or maternal environmental effects...

  9. Function of adhesion molecules lymphocyte function-associated antigen-3 and intercellular adhesion molecule-1 on human epidermal Langerhans cells in antigen-specific T cell activation

    NARCIS (Netherlands)

    Teunissen, M. B.; Rongen, H. A.; Bos, J. D.

    1994-01-01

    In addition to the interaction between the TCR and the MHC/Ag complex on the APC, optimal T cell activation also requires interaction between adhesion molecules on the APC and their ligands on T cells. We determined the presence of adhesion molecules on human epidermal Langerhans cells (LC) and

  10. 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.

  11. 21 CFR 878.4010 - Tissue adhesive.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Tissue adhesive. 878.4010 Section 878.4010 Food... DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4010 Tissue adhesive. (a) Tissue adhesive for the topical approximation of skin—(1) Identification. A tissue adhesive for the topical...

  12. Adhesion Strength of Wood Based Composites Coated with Cellulosic and Polyurethane Paints

    Directory of Open Access Journals (Sweden)

    Tuncer Dilik

    2015-01-01

    Full Text Available The objective of this study was to determine adhesive strength of particleboard and medium density fiberboard (MDF finished with two types of paints. Samples were coated using cellulosic and polyurethane based paints. Adhesion strength and coating layer thickness of each sample were measured using pull-off testing method and PosiTector equipment, respectively. The highest adhesion strength value of 3.62 MPa was found for MDF samples coated with paint. Based on the statistical analysis type of substrate significantly influenced overall adhesion strength of the samples while type and layer thickness of paint as well as number of layers applied to the surface of specimens have not affected significantly adhesion resistance of the panels used in this work. It appears that pull-off test can effectively be used to determine and evaluate adhesion strength of the samples considered in the experiments.

  13. New denture adhesive containing miconazole nitrate polymeric microparticles: Antifungal, adhesive force and toxicity properties.

    Science.gov (United States)

    Cartagena, Andrés Felipe; Esmerino, Luís Antonio; Polak-Junior, Rogerio; Olivieri Parreiras, Sibelli; Domingos Michél, Milton; Farago, Paulo Vitor; Campanha, Nara Hellen

    2017-02-01

    The purpose of this study was to develop a new oral drug delivery system by incorporating polymeric miconazole nitrate (MN) microparticles on an experimental antifungal denture adhesive (DA). Spray drying Eudragit L-100 (E) and Gantrez MS-955 (G) MN-microparticles were incorporated in DA. DAE1, DAG1, DAEG1, DAE2, DAG2, DAEG2 groups were obtained from the combination of polymers used in MN-microparticles (E, G and EG) and concentration of MN into DA (1, for 1% and 2, for 2%). DA with 2% pure MN (DAM) and DA without microparticles or drug (DACT) were both control groups. All groups were evaluated to determine microbiological assay, adhesive force and toxicity. Minimum inhibitory concentration (MIC) against Candida albicans was performed by broth micro-dilution and agar dilution methods in extract of DAs and conventional gel form (Daktarin ® ). Adhesive load testing was made between acrylic resin samples on a universal testing machine after immersion in water. The toxicity of several dilutions of DAs was performed with Artemia salina bioassay after 24 and 48h. Data of adhesive force were evaluated with two-way ANOVA and Bonferroni tests (α=0.05). The concentration required to kill 50% (LC50) was determined using the Provit analysis. DA with polymeric microparticles and pure drug presented MIC between 1.25-5μg/mL similar to MIC values of DAM. DAEG2, DAEG1, DAG20 showed the most actives against C. albicans. The best adhesive properties were exhibited by DAEG2, consisting of high initial adhesive force which was maintained for up to 6h. The extracts of all DA presented low or not toxicity at 24 and 48h. DA containing 2% of MN loaded in microparticles made by Gantrez MS-955 alone or combined with Eudragit L-100 produce effective antifungal activity, good adhesive force, and no toxicity effect being a promising therapeutics for removable denture wearers affected by denture stomatitis. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All

  14. Dynamic 99mTc-DTPA renal gammagraphy with glomerular filtration rate determination

    International Nuclear Information System (INIS)

    Vivodova, M.; Hupka, S.; Michalko, J.; Lehotska, V.; Pipa, V.; Hasik, E.; Tomek, D.

    1989-01-01

    Using the method of 99m Tc-DTPA (diethylenetriaminepentaacetic acid) sequential renal gammagraphy with subsequent glomerular filtration rate determination by means of a gamma camera and a computer, a total of 285 patients were examined with suspected renal and urinary tract diseases, subjects after surgery on these organs or those serving as controls after drug therapy. With the help of a modified application computer program, a study was designed to evaluate quantitatively some functional parameters and to determine the total and the separate glomerular filtration rate values by 99m Tc-DTPA according to Gates. The benefits of the method are that it is non-invasive, rapid, atraumatic, with low exposure to radiation while offering a broad range of applications in routine diagnostic practice of nephrology, and especially so in pediatric patients. (author). 7 figs., 3 tabs., 18 refs

  15. Development of nuclear methods for determining fluid-dynamic parameters in fluid catalyst cracking reactors

    International Nuclear Information System (INIS)

    Santos, V.A. dos; Dantas, C.C.

    1986-01-01

    Flow parameters of circulating fluidized bed in a simulated Fluid Catalyst Cracking reactor were determined by means of nuclear methods. The parameters were: residence time, density, inventory, circulation rate and radial distribution, for the catalyst; residence time for the gaseous phase. The nuclear methods where the gamma attenuation and the radiotracer. Two tracer techniques were developed, one for tagging of the catalyst by the 59 Fe as intrinsic tracer and another for tagging of the gaseous phase by the CH 3 82 Br as tracer. A detailed description of each measuring technique for all the investigated parameters is included. To carry out the determination for some of parameters a combination of the two methods was also applied. The results and the nuclear data are given in a table. (Author) [pt

  16. Mouse lung adhesion assay for Bordetella pertussis

    International Nuclear Information System (INIS)

    Burns, K.A.; Freer, J.H.

    1982-01-01

    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 μCi (37 K Bq) of [ 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. (Auth.)

  17. Characterizing fluid dynamics in a bubble column aimed for the determination of reactive mass transfer

    Science.gov (United States)

    Kováts, Péter; Thévenin, Dominique; Zähringer, Katharina

    2018-02-01

    Bubble column reactors are multiphase reactors that are used in many process engineering applications. In these reactors a gas phase comes into contact with a fluid phase to initiate or support reactions. The transport process from the gas to the liquid phase is often the limiting factor. Characterizing this process is therefore essential for the optimization of multiphase reactors. For a better understanding of the transfer mechanisms and subsequent chemical reactions, a laboratory-scale bubble column reactor was investigated. First, to characterize the flow field in the reactor, two different methods have been applied. The shadowgraphy technique is used for the characterisation of the bubbles (bubble diameter, velocity, shape or position) for various process conditions. This technique is based on particle recognition with backlight illumination, combined with particle tracking velocimetry (PTV). The bubble trajectories in the column can also be obtained in this manner. Secondly, the liquid phase flow has been analysed by particle image velocimetry (PIV). The combination of both methods, delivering relevant information concerning disperse (bubbles) and continuous (liquid) phases, leads to a complete fluid dynamical characterization of the reactor, which is the pre-condition for the analysis of mass transfer between both phases.

  18. A methodology for determining the dynamic exchange of resources in nuclear fuel cycle simulation

    International Nuclear Information System (INIS)

    Gidden, Matthew J.; Wilson, Paul P.H.

    2016-01-01

    Highlights: • A novel fuel cycle simulation entity interaction mechanism is proposed. • A framework and implementation of the mechanism is described. • New facility outage and regional interaction scenario studies are described and analyzed. - Abstract: Simulation of the nuclear fuel cycle can be performed using a wide range of techniques and methodologies. Past efforts have focused on specific fuel cycles or reactor technologies. The CYCLUS fuel cycle simulator seeks to separate the design of the simulation from the fuel cycle or technologies of interest. In order to support this separation, a robust supply–demand communication and solution framework is required. Accordingly an agent-based supply-chain framework, the Dynamic Resource Exchange (DRE), has been designed implemented in CYCLUS. It supports the communication of complex resources, namely isotopic compositions of nuclear fuel, between fuel cycle facilities and their managers (e.g., institutions and regions). Instances of supply and demand are defined as an optimization problem and solved for each timestep. Importantly, the DRE allows each agent in the simulation to independently indicate preference for specific trading options in order to meet both physics requirements and satisfy constraints imposed by potential socio-political models. To display the variety of possible simulations that the DRE enables, example scenarios are formulated and described. Important features include key fuel-cycle facility outages, introduction of external recycled fuel sources (similar to the current mixed oxide (MOX) fuel fabrication facility in the United States), and nontrivial interactions between fuel cycles existing in different regions.

  19. Nodal recovery, dual pathway physiology, and concealed conduction determine complex AV dynamics in human atrial tachyarrhythmias.

    Science.gov (United States)

    Masè, Michela; Glass, Leon; Disertori, Marcello; Ravelli, Flavia

    2012-11-15

    The genesis of complex ventricular rhythms during atrial tachyarrhythmias in humans is not fully understood. To clarify the dynamics of atrioventricular (AV) conduction in response to a regular high-rate atrial activation, 29 episodes of spontaneous or pacing-induced atrial flutter (AFL), covering a wide range of atrial rates (cycle lengths from 145 to 270 ms), were analyzed in 10 patients. AV patterns were identified by applying firing sequence and surrogate data analysis to atrial and ventricular activation series, whereas modular simulation with a difference-equation AV node model was used to correlate the patterns with specific nodal properties. AV node response at high atrial rate was characterized by 1) AV patterns of decreasing conduction ratios at the shortening of atrial cycle length (from 236.3 ± 32.4 to 172.6 ± 17.8 ms) according to a Farey sequence ordering (conduction ratio from 0.34 ± 0.12 to 0.23 ± 0.06; P AV block patterns occurring during regular atrial tachyarrhythmias. The characterization of AV nodal function during different AFL forms constitutes an intermediate step toward the understanding of complex ventricular rhythms during atrial fibrillation.

  20. A model based on stochastic dynamic programming for determining China's optimal strategic petroleum reserve policy

    International Nuclear Information System (INIS)

    Zhang Xiaobing; Fan Ying; Wei Yiming

    2009-01-01

    China's Strategic Petroleum Reserve (SPR) is currently being prepared. But how large the optimal stockpile size for China should be, what the best acquisition strategies are, how to release the reserve if a disruption occurs, and other related issues still need to be studied in detail. In this paper, we develop a stochastic dynamic programming model based on a total potential cost function of establishing SPRs to evaluate the optimal SPR policy for China. Using this model, empirical results are presented for the optimal size of China's SPR and the best acquisition and drawdown strategies for a few specific cases. The results show that with comprehensive consideration, the optimal SPR size for China is around 320 million barrels. This size is equivalent to about 90 days of net oil import amount in 2006 and should be reached in the year 2017, three years earlier than the national goal, which implies that the need for China to fill the SPR is probably more pressing; the best stockpile release action in a disruption is related to the disruption levels and expected continuation probabilities. The information provided by the results will be useful for decision makers.

  1. Dynamic strength and failure of 430F stainless steel determined by combined experimental-numerical method

    Science.gov (United States)

    Paris, Vitaly; Cohen, Amitay; Porat, Elkana; Fridman, Pinhas; Harpenes, Zvi; Yosef-Hai, Arnon; Levi-Hevroni, David

    2017-06-01

    Dynamic flow stress of metals is well known to depend significantly on the strain rate. Strain to failure behavior of ductile metals can be influenced by both the stress triaxiality and the strain rate. While either compressive or tensile Split Hopkinson Pressure Bar system (SHPB) are commonly used to obtain flow stress and failure data for metals, experimental methodologies to obtain such data under conditions of shear loading are less based. In the present study we have investigated the effect of strain rate on the flow stress and strain to failure of 430F stainless steel at strain rates ranging from 400 to 16000 1/sec using shear disc specimens (SDS) incorporated into standard SHPB system. The SDS sample is a disc having axisymmetric slits on its both flat faces which is sheared during the test by ring and cylinder-shaped adaptors mounted between the bars. The analysis of the data was performed by matching the experimental signals with results of numerical modeling of the tests. The obtained flow stress versus strain rate data were fitted with Cowper-Symonds model. The results indicate strong dependence of flow stress of 430F steel on strain rate in the investigated range of rates. The strain to failure data demonstrates a noticeable decrease with increase of the strain rate.

  2. Direct and indirect effects of giant kelp determine benthic community structure and dynamics.

    Science.gov (United States)

    Arkema, Katie K; Reed, Daniel C; Schroeter, Stephen C

    2009-11-01

    Indirect facilitation can occur when a species positively affects another via the suppression of a shared competitor. In giant kelp forests, shade from the canopy of the giant kelp, Macrocystis pyrifera, negatively affects understory algae, which compete with sessile invertebrates for space. This raises the possibility that giant kelp indirectly facilitates sessile invertebrates, via suppression of understory algae. We evaluated the effect of giant kelp on the relative abundance of algae and invertebrates by experimentally manipulating kelp abundance on large artificial reefs located off San Clemente, California, USA. The experiments revealed a negative effect of giant kelp on both light availability and understory algal abundance and a positive effect on the abundance of sessile invertebrates, which was consistent with an indirect effect mediated by shade from the kelp canopy. The importance of these processes to temporal variability in benthic community structure was evaluated at 16 locations on natural reefs off Santa Barbara, California, over an eight-year period. Interannual variability in the abundance of understory algae and in the abundance of sessile invertebrates was significantly and positively related to interannual variability in the abundance of giant kelp. Analysis of these observational data using Structural Equation Modeling (SEM) indicated that the magnitude of the indirect effect of giant kelp on invertebrates was six times larger than the direct effect on invertebrates. Results suggest that the dynamics of this system are driven by variability in the abundance of a single structure-forming species that has indirect positive, as well as direct negative, effects on associated species.

  3. The Molecular Structure of a Phosphatidylserine Bilayer Determined by Scattering and Molecular Dynamics Simulations

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Jianjun [University of South Florida, Tampa (USF); Cheng, Xiaolin [ORNL; Monticelli, Luca [Institut National de la Santé et de la Recherche Médicale (INSERM) and INTS, France; Heberle, Frederick A [ORNL; Kucerka, Norbert [Atomic Energy of Canada Limited (AECL), Canadian Neutron Beam Centre (CNBC) and Comenius University,; Tieleman, D. Peter [University of Calgary, ALberta, Canada; Katsaras, John [ORNL

    2014-01-01

    Phosphatidylserine (PS) lipids play essential roles in biological processes, including enzyme activation and apoptosis. We report on the molecular structure and atomic scale interactions of a fluid bilayer composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylserine (POPS). A scattering density profile model, aided by molecular dynamics (MD) simulations, was developed to jointly refine different contrast small-angle neutron and X-ray scattering data, which yielded a lipid area of 62.7 A2 at 25 C. MD simulations with POPS lipid area constrained at different values were also performed using all-atom and aliphatic united-atom models. The optimal simulated bilayer was obtained using a model-free comparison approach. Examination of the simulated bilayer, which agrees best with the experimental scattering data, reveals a preferential interaction between Na+ ions and the terminal serine and phosphate moieties. Long-range inter-lipid interactions were identified, primarily between the positively charged ammonium, and the negatively charged carboxylic and phosphate oxygens. The area compressibility modulus KA of the POPS bilayer was derived by quantifying lipid area as a function of surface tension from area-constrained MD simulations. It was found that POPS bilayers possess a much larger KA than that of neutral phosphatidylcholine lipid bilayers. We propose that the unique molecular features of POPS bilayers may play an important role in certain physiological functions.

  4. Network dynamics determine the autocrine and paracrine signaling functions of TNF

    Science.gov (United States)

    Caldwell, Andrew B.; Cheng, Zhang; Vargas, Jesse D.; Birnbaum, Harry A.

    2014-01-01

    A hallmark of the inflammatory response to pathogen exposure is the production of tumor necrosis factor (TNF) that coordinates innate and adaptive immune responses by functioning in an autocrine or paracrine manner. Numerous molecular mechanisms contributing to TNF production have been identified, but how they function together in macrophages remains unclear. Here, we pursued an iterative systems biology approach to develop a quantitative understanding of the regulatory modules that control TNF mRNA synthesis and processing, mRNA half-life and translation, and protein processing and secretion. By linking the resulting model of TNF production to models of the TLR-, the TNFR-, and the NFκB signaling modules, we were able to study TNF’s functions during the inflammatory response to diverse TLR agonists. Contrary to expectation, we predicted and then experimentally confirmed that in response to lipopolysaccaride, TNF does not have an autocrine function in amplifying the NFκB response, although it plays a potent paracrine role in neighboring cells. However, in response to CpG DNA, autocrine TNF extends the duration of NFκB activity and shapes CpG-induced gene expression programs. Our systems biology approach revealed that network dynamics of MyD88 and TRIF signaling and of cytokine production and response govern the stimulus-specific autocrine and paracrine functions of TNF. PMID:25274725

  5. Phytoplankton growth and microzooplankton grazing dynamics across vertical environmental gradients determined by transplantin situdilution experiments.

    Science.gov (United States)

    Gutiérrez-Rodríguez, Andrés; Selph, Karen E; Landry, Michael R

    2016-03-01

    The Costa Rica Dome (CRD) represents a classic case of the bloom-forming capacity of small phytoplankton. Unlike other upwelling systems, autotrophic biomass in the CRD is dominated by picocyanobacteria and small eukaryotes that outcompete larger diatoms and reach extremely high biomass levels. We investigated responses of the subsurface phytoplankton community of the CRD to changes associated with vertical displacement of water masses, coupling in situ transplanted dilution experiments with flow cytometry and epifluorescence microscopy to assess group-specific dynamics. Growth rates of Synechococcus (SYN) and photosynthetic picoeukaryotes (PEUK) were positively correlated with light ( R pearson_SYN = 0.602 and R pearson_PEUK = 0.588, P grazing and growth rates were closely coupled in all picophytoplankton groups ( R spearman_PRO = 0.572, R spearman_SYN = 0.588, R spearman_PEUK = 0.624), and net growth rates remained close to zero. Conversely, the abundance and biomass of larger phytoplankton, mainly diatoms, increased more than 10-fold in shallower transplant incubations indicating that, in addition to trace-metal chemistry, light also plays a significant role in controlling microphytoplankton populations in the CRD.

  6. Mic60/Mitofilin determines MICOS assembly essential for mitochondrial dynamics and mtDNA nucleoid organization

    OpenAIRE

    Li, H; Ruan, Y; Zhang, K; Jian, F; Hu, C; Miao, L; Gong, L; Sun, L; Zhang, X; Chen, S; Chen, H; Liu, D; Song, Z

    2015-01-01

    The MICOS complex (mitochondrial contact site and cristae organizing system) is essential for mitochondrial inner membrane organization and mitochondrial membrane contacts, however, the molecular regulation of MICOS assembly and the physiological functions of MICOS in mammals remain obscure. Here, we report that Mic60/Mitofilin has a critical role in the MICOS assembly, which determines the mitochondrial morphology and mitochondrial DNA (mtDNA) organization. The downregulati...

  7. 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.

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

    NARCIS (Netherlands)

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

    Sea urchins have specialized adhesive organs called tube feet, which mediate strong but reversible adhesion. Tube feet are composed by a disc, producing adhesive and de-adhesive secretions for substratum attachment, and a stem for movement. After detachment the secreted adhesive remains bound to the

  9. Nonequilibrium ab initio molecular dynamics determination of Ti monovacancy migration rates in B 1 TiN

    Science.gov (United States)

    Gambino, D.; Sangiovanni, D. G.; Alling, B.; Abrikosov, I. A.

    2017-09-01

    We use the color diffusion (CD) algorithm in nonequilibrium (accelerated) ab initio molecular dynamics simulations to determine Ti monovacancy jump frequencies in NaCl-structure titanium nitride (TiN), at temperatures ranging from 2200 to 3000 K. Our results show that the CD method extended beyond the linear-fitting rate-versus-force regime [Sangiovanni et al., Phys. Rev. B 93, 094305 (2016), 10.1103/PhysRevB.93.094305] can efficiently determine metal vacancy migration rates in TiN, despite the low mobilities of lattice defects in this type of ceramic compound. We propose a computational method based on gamma-distribution statistics, which provides unambiguous definition of nonequilibrium and equilibrium (extrapolated) vacancy jump rates with corresponding statistical uncertainties. The acceleration-factor achieved in our implementation of nonequilibrium molecular dynamics increases dramatically for decreasing temperatures from 500 for T close to the melting point Tm, up to 33 000 for T ≈0.7 Tm .

  10. 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.

  11. 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 ...

  12. Antagonistic Activity of Lactobacillus reuteri Strains on the Adhesion Characteristics of Selected Pathogens

    OpenAIRE

    Singh, Tejinder P.; Kaur, Gurpreet; Kapila, Suman; Malik, Ravinder K.

    2017-01-01

    Adhesion ability of probiotics is the key factor that decides their colonization in the gastrointestinal tract and potential to inhibit pathogens. Therefore, adhesion ability can be considered as a key determinant for probiotic efficacy. Presents study documents the antagonistic activity of viable/untreated, Lithium chloride (LiCl) treated or heat-killed forms of eight probiotic Lactobacillus reuteri strains on the adhesion characteristics of selected pathogens. All strains investigated were ...

  13. 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.

  14. Flood regime and leaf fall determine soil inorganic nitrogen dynamics in semiarid riparian forests.

    Science.gov (United States)

    Shah, J J Follstad; Dahm, C N

    2008-04-01

    Flow regulation has reduced the exchange of water, energy, and materials between rivers and floodplains, caused declines in native plant populations, and advanced the spread of nonnative plants. Naturalized flow regimes are regarded as a means to restore degraded riparian areas. We examined the effects of flood regime (short [SIFI] vs. long [LIFI] inter-flood interval) on plant community and soil inorganic nitrogen (N) dynamics in riparian forests dominated by native Populus deltoides var. wislizenii Eckenwalder (Rio Grande cottonwood) and nonnative Tamarix chinensis Lour. (salt cedar) along the regulated middle Rio Grande of New Mexico. The frequency of inundation (every 2-3 years) at SIFI sites better reflected inundation patterns prior to the closure of an upstream dam relative to the frequency of inundation at LIFI sites (> or =10 years). Riparian inundation at SIFI sites varied from 7 to 45 days during the study period (April 2001-July 2004). SIFI vs. LIFI sites had higher soil moisture but greater groundwater table elevation fluctuation in response to flooding and drought. Rates of net N mineralization were consistently higher at LIFI vs. SIFI sites, and soil inorganic N concentrations were greatest at sites with elevated leaf-litter production. Sites with stable depth to ground water (approximately 1.5 m) supported the greatest leaf-litter production. Reduced leaf production at P. deltoides SIFI sites was attributed to drought-induced recession of ground water and prolonged inundation. We recommend that natural resource managers and restoration practitioners (1) utilize naturalized flows that help maintain riparian groundwater elevations between 1 and 3 m in reaches with mature P. deltoides or where P. deltoides revegetation is desired, (2) identify areas that naturally undergo long periods of inundation and consider restoring these areas to seasonal wetlands, and (3) use native xeric-adapted riparian plants to revegetate LIFI and SIFI sites where

  15. Dynamic oceanography determines fine scale foraging behavior of Masked Boobies in the Gulf of Mexico.

    Science.gov (United States)

    Poli, Caroline L; Harrison, Autumn-Lynn; Vallarino, Adriana; Gerard, Patrick D; Jodice, Patrick G R

    2017-01-01

    During breeding, foraging marine birds are under biological, geographic, and temporal constraints. These contraints require foraging birds to efficiently process environmental cues derived from physical habitat features that occur at nested spatial scales. Mesoscale oceanography in particular may change rapidly within and between breeding seasons, and findings from well-studied systems that relate oceanography to seabird foraging may transfer poorly to regions with substantially different oceanographic conditions. Our objective was to examine foraging behavior of a pan-tropical seabird, the Masked Booby (Sula dactylatra), in the understudied Caribbean province, a moderately productive region driven by highly dynamic currents and fronts. We tracked 135 individuals with GPS units during May 2013, November 2013, and December 2014 at a regionally important breeding colony in the southern Gulf of Mexico. We measured foraging behavior using characteristics of foraging trips and used area restricted search as a proxy for foraging events. Among individual attributes, nest stage contributed to differences in foraging behavior whereas sex did not. Birds searched for prey at nested hierarchical scales ranging from 200 m-35 km. Large-scale coastal and shelf-slope fronts shifted position between sampling periods and overlapped geographically with overall foraging locations. At small scales (at the prey patch level), the specific relationship between environmental variables and foraging behavior was highly variable among individuals but general patterns emerged. Sea surface height anomaly and velocity of water were the strongest predictors of area restricted search behavior in random forest models, a finding that is consistent with the characterization of the Gulf of Mexico as an energetic system strongly influenced by currents and eddies. Our data may be combined with tracking efforts in the Caribbean province and across tropical regions to advance understanding of seabird

  16. pKa values in proteins determined by electrostatics applied to molecular dynamics trajectories.

    Science.gov (United States)

    Meyer, Tim; Knapp, Ernst-Walter

    2015-06-09

    For a benchmark set of 194 measured pKa values in 13 proteins, electrostatic energy computations are performed in which pKa values are computed by solving the Poisson-Boltzmann equation. In contrast to the previous approach of Karlsberg(+) (KB(+)) that essentially used protein crystal structures with variations in their side chain conformations, the present approach (KB2(+)MD) uses protein conformations from four molecular dynamics (MD) simulations of 10 ns each. These MD simulations are performed with different specific but fixed protonation patterns, selected to sample the conformational space for the different protonation patterns faithfully. The root-mean-square deviation between computed and measured pKa values (pKa RMSD) is shown to be reduced from 1.17 pH units using KB(+) to 0.96 pH units using KB2(+)MD. The pKa RMSD can be further reduced to 0.79 pH units, if each conformation is energy-minimized with a dielectric constant of εmin = 4 prior to calculating the electrostatic energy. The electrostatic energy expressions upon which the computations are based have been reformulated such that they do not involve terms that mix protein and solvent environment contributions and no thermodynamic cycle is needed. As a consequence, conformations of the titratable residues can be treated independently in the protein and solvent environments. In addition, the energy terms used here avoid the so-called intrinsic pKa and can therefore be interpreted without reference to arbitrary protonation states and conformations.

  17. Towards the determination of Mytilus edulis food preferences using the dynamic energy budget (DEB theory.

    Directory of Open Access Journals (Sweden)

    Coralie Picoche

    Full Text Available 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

  18. A feasibility study for experimentally determining dynamic force distribution in a lap joint

    Energy Technology Data Exchange (ETDEWEB)

    Mayes, Randall Lee [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    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.

  19. Dynamic oceanography determines fine scale foraging behavior of Masked Boobies in the Gulf of Mexico

    Science.gov (United States)

    Poli, Caroline L.; Harrison, Autumn-Lynn; Vallarino, Adriana; Gerard, Patrick D.; Jodice, Patrick G.R.

    2017-01-01

    During breeding, foraging marine birds are under biological, geographic, and temporal constraints. These contraints require foraging birds to efficiently process environmental cues derived from physical habitat features that occur at nested spatial scales. Mesoscale oceanography in particular may change rapidly within and between breeding seasons, and findings from well-studied systems that relate oceanography to seabird foraging may transfer poorly to regions with substantially different oceanographic conditions. Our objective was to examine foraging behavior of a pan-tropical seabird, the Masked Booby (Sula dactylatra), in the understudied Caribbean province, a moderately productive region driven by highly dynamic currents and fronts. We tracked 135 individuals with GPS units during May 2013, November 2013, and December 2014 at a regionally important breeding colony in the southern Gulf of Mexico. We measured foraging behavior using characteristics of foraging trips and used area restricted search as a proxy for foraging events. Among individual attributes, nest stage contributed to differences in foraging behavior whereas sex did not. Birds searched for prey at nested hierarchical scales ranging from 200 m—35 km. Large-scale coastal and shelf-slope fronts shifted position between sampling periods and overlapped geographically with overall foraging locations. At small scales (at the prey patch level), the specific relationship between environmental variables and foraging behavior was highly variable among individuals but general patterns emerged. Sea surface height anomaly and velocity of water were the strongest predictors of area restricted search behavior in random forest models, a finding that is consistent with the characterization of the Gulf of Mexico as an energetic system strongly influenced by currents and eddies. Our data may be combined with tracking efforts in the Caribbean province and across tropical regions to advance understanding of seabird

  20. Dynamic oceanography determines fine scale foraging behavior of Masked Boobies in the Gulf of Mexico.

    Directory of Open Access Journals (Sweden)

    Caroline L Poli

    Full Text Available During breeding, foraging marine birds are under biological, geographic, and temporal constraints. These contraints require foraging birds to efficiently process environmental cues derived from physical habitat features that occur at nested spatial scales. Mesoscale oceanography in particular may change rapidly within and between breeding seasons, and findings from well-studied systems that relate oceanography to seabird foraging may transfer poorly to regions with substantially different oceanographic conditions. Our objective was to examine foraging behavior of a pan-tropical seabird, the Masked Booby (Sula dactylatra, in the understudied Caribbean province, a moderately productive region driven by highly dynamic currents and fronts. We tracked 135 individuals with GPS units during May 2013, November 2013, and December 2014 at a regionally important breeding colony in the southern Gulf of Mexico. We measured foraging behavior using characteristics of foraging trips and used area restricted search as a proxy for foraging events. Among individual attributes, nest stage contributed to differences in foraging behavior whereas sex did not. Birds searched for prey at nested hierarchical scales ranging from 200 m-35 km. Large-scale coastal and shelf-slope fronts shifted position between sampling periods and overlapped geographically with overall foraging locations. At small scales (at the prey patch level, the specific relationship between environmental variables and foraging behavior was highly variable among individuals but general patterns emerged. Sea surface height anomaly and velocity of water were the strongest predictors of area restricted search behavior in random forest models, a finding that is consistent with the characterization of the Gulf of Mexico as an energetic system strongly influenced by currents and eddies. Our data may be combined with tracking efforts in the Caribbean province and across tropical regions to advance

  1. Drop shape analysis for determination of dynamic contact angles by double sided elliptical fitting method

    DEFF Research Database (Denmark)

    Andersen, Nis Korsgaard; Taboryski, Rafael J.

    2017-01-01

    Contact angle measurements are a fast and simple way to measure surface properties and is therefore widely used to measure surface energy and quantify wetting of a solid surface by a liquid substance. In common praxis contact angle measurements are done with sessile drops on a horizontal surface...... fitted to a drop profile derived from the Young-Laplace equation. When measuring the wetting behaviour by tilting experiments this is not possible since it involves moving drops that are not in equilibrium. Here we present a fitting technique capable of determining the contact angle of asymmetric drops...

  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. Analysis of domain wall dynamics based on skewness of magnetic Barkhausen noise for applied stress determination

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Song [College of Electrical Engineering and Control Science, Nanjing Tech University, Nanjing, Jiangsu 211816 (China); School of Automation Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu 210016 (China); Tian, GuiYun, E-mail: tian280@hotmail.com [School of Automation Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu 210016 (China); School of Electrical and Electronic Engineering, Merz Court, University of Newcastle upon Tyne, Newcastle NE1 7RU (United Kingdom); Dobmann, Gerd; Wang, Ping [School of Automation Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu 210016 (China)

    2017-01-01

    Skewness of Magnetic Barkhausen Noise (MBN) signal is used as a new feature for applied stress determination. After experimental studies, skewness presents its ability for measuring applied tensile stress compared with conventional feature, meanwhile, a non-linear behavior of this new feature and an independence of the excitation conditions under compressive stress are found and discussed. Effective damping during domain wall motion influencing the asymmetric shape of the MBN statistical distribution function is discussed under compressive and tensile stress variation. Domain wall (DW) energy and distance between pinning edges of the DW are considered altering the characteristic relaxation time, which is the reason for the non-linear phenomenon of skewness. - Highlights: • The skewness of magnetic Barkhausen noise profile is proposed as a new feature for applied stress determination. • The skewness is sensitive to applied stress and independent to excitation frequency. • Domain wall energy and pinning distance influence the relaxation time of domain wall, which leads to a non-linear behavior of skewness under compressive stress.

  4. The association of metabolic syndrome markers with adhesive capsulitis.

    Science.gov (United States)

    Austin, Daniel C; Gans, Itai; Park, Min Jung; Carey, James L; Kelly, John D

    2014-07-01

    Research has associated adhesive capsulitis with diabetes mellitus but suggests that glucose-mediated injury may begin before diabetes is diagnosed. The period preceding diabetes is often marked by metabolic syndrome. We investigated the relationship between metabolic syndrome components (insulin resistance, hypertension, dyslipidemia, and obesity) and the development of adhesive capsulitis using a case-control study. We retrospectively reviewed 150 consecutive adhesive capsulitis patient charts to determine the prevalence of obesity and of medications used for treating metabolic syndrome elements and compared these with previously reported nationwide values. The prevalence of anti-hyperglycemia medications in the adhesive capsulitis cohort was 18.4% (95% confidence interval [CI], 12.9%-25.7%), twice the national rate of diagnosed diabetes of 7.6% (95% CI, 6.7%-8.5%). In the 20- to 39-year-old group, the prevalence of anti-hyperglycemic medications, 26.3% (95% CI, 11.8%-48.8%), was over 10 times the nationwide rate. The overall prevalence of hypertensive medication use in the adhesive capsulitis group, 33.1% (95% CI, 25.9%-41.2%), was notably higher than the nationwide rate, 21.6% (95% CI, 19.8%-23.4%). In the 40- to 64-year-old group, the prevalence of hypertensive medication use, 36.8% (95% CI, 28.6%-46.0%), was notably higher than the nationwide rate of 24.5% (95% CI, 22.2%-27.0%). The prevalence of anti-lipid medications and obesity was similar between the groups. The relationship between adhesive capsulitis and metabolic syndrome remains unclear. Our results confirm previous work associating hyperglycemia with adhesive capsulitis. We have also shown a possible association of hypertension, part of metabolic syndrome and a proinflammatory condition, with adhesive capsulitis, which has not been previously described. Copyright © 2014 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Mosby, Inc. All rights reserved.

  5. 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.

  6. Determinants and repeatability of the specific dynamic response of the corn snake, Pantherophis guttatus.

    Science.gov (United States)

    Crocker-Buta, Sarah P; Secor, Stephen M

    2014-03-01

    Ingesting, digesting, absorbing, and assimilating a meal are all energy consuming processes that accumulate to form the specific dynamic action (SDA) of the meal. Sensitive to digestive demand, SDA is theoretically fixed to a given meal size and type. In this study, we altered relative meal size to explore the effects of digestive demand on the postprandial metabolic profile and SDA of the corn snake, Pantherophis guttatus. We also examined the effects of body temperature on the SDA response while controlling for meal size and type and assessed whether these responses are highly repeatable under the same conditions. Additionally, the effects of body mass on SDA were investigated by feeding snakes the same relative and absolute meal size. With increases in digestive demand (meals from 5% to 45% of body mass), P. guttatus responded with incremental increases in the postprandial peak in oxygen consumption (VO2), the duration of the significantly elevated VO2, and SDA. Body temperature had an observable impact on the postprandial metabolic profile, decreasing the duration and increasing the peak VO2, however, body temperature did not significantly alter SDA. Regardless of temperature, and hence duration, snakes expended the same amount of energy in digesting a given meal. This was additionally borne out when testing the individual repeatability of the SDA response, individual P. guttatus exhibited nearly identical postprandial responses to the same meal. Over a 90-fold range in body mass, and fed meals equaling 25% of body mass, P. guttatus exhibited an isometric relationship between SDA and body mass. When fed a set 10-gram meal, snakes regardless of body size expended the same amount of energy on digestion and assimilation. Characteristically, P. guttatus experience a rapid postprandial increase in metabolic rate that peaks and gradually descends to prefeeding levels. The magnitude of that response (quantified as SDA) varies as a function of digestive demand (i

  7. Drop shape analysis for determination of dynamic contact angles by double sided elliptical fitting method

    International Nuclear Information System (INIS)

    Andersen, Nis Korsgaard; Taboryski, Rafael

    2017-01-01

    Contact angle measurements are a fast and simple way to measure surface properties and is therefore widely used to measure surface energy and quantify wetting of a solid surface by a liquid substance. In common praxis contact angle measurements are done with sessile drops on a horizontal surface fitted to a drop profile derived from the Young-Laplace equation. When measuring the wetting behaviour by tilting experiments this is not possible since it involves moving drops that are not in equilibrium. Here we present a fitting technique capable of determining the contact angle of asymmetric drops with very high accuracy even with blurry or noisy images. We do this by splitting the trace of a drop into a left and right part at the apex and then fit each side to an ellipse. (technical note)

  8. Water Level Flux in Household Containers in Vietnam - A Key Determinant of Aedes aegypti Population Dynamics

    Science.gov (United States)

    Jeffery, Jason A. L.; Clements, Archie C. A.; Nguyen, Yen Thi; Nguyen, Le Hoang; Tran, Son Hai; Le, Nghia Trung; Vu, Nam Sinh; Ryan, Peter A.; Kay, Brian H.

    2012-01-01

    We examined changes in the abundance of immature Aedes aegypti at the household and water storage container level during the dry-season (June-July, 2008) in Tri Nguyen village, central Vietnam. We conducted quantitative immature mosquito surveys of 171 containers in the same 41 households, with replacement of samples, every two days during a 29-day period. We developed multi-level mixed effects regression models to investigate container and household variability in pupal abundance. The percentage of houses that were positive for I/II instars, III/IV instars and pupae during any one survey ranged from 19.5–43.9%, 48.8–75.6% and 17.1–53.7%, respectively. The mean numbers of Ae. aegypti pupae per house ranged between 1.9–12.6 over the study period. Estimates of absolute pupal abundance were highly variable over the 29-day period despite relatively stable weather conditions. Most variability in pupal abundance occurred at the container rather than the household level. A key determinant of Ae. aegypti production was the frequent filling of the containers with water, which caused asynchronous hatching of Ae. aegypti eggs and development of cohorts of immatures. We calculated the probability of the water volume of a large container (>500L) increasing or decreasing by ≥20% to be 0.05 and 0.07 per day, respectively, and for small containers (<500L) to be 0.11 and 0.13 per day, respectively. These human water-management behaviors are important determinants of Ae. aegypti production during the dry season. This has implications for choosing a suitable Wolbachia strain for release as it appears that prolonged egg desiccation does not occur in this village. PMID:22911683

  9. Preirradiation endocrinopathies in pediatric brain tumor patients determined by dynamic tests of endocrine function

    International Nuclear Information System (INIS)

    Merchant, Thomas E.; Williams, Tani; Smith, Julie M.; Rose, Susan R.; Danish, Robert K.; Burghen, George A.; Kun, Larry E.; Lustig, Robert H.

    2002-01-01

    Purpose: To prospectively evaluate pediatric patients with localized primary brain tumors for evidence of endocrinopathy before radiotherapy (RT). Methods and Materials: Seventy-five pediatric patients were evaluated with the arginine tolerance test and L-dopa test for growth hormone secretory capacity and activity; thyroid-stimulating hormone surge and thyrotropin-releasing hormone stimulation test for the hypothalamic-thyroid axis; the 1-μg adrenocorticotropin hormone (ACTH) and metyrapone test for ACTH reserve; and, depending on age, a gonadotropin-releasing hormone stimulation test to determine gonadotropin response. The study included 38 male and 37 female patients, age 1-21 years with ependymoma (n=35), World Health Organization (WHO) Grade I-II astrocytoma (n=18), WHO Grade III-IV astrocytoma (n=10), craniopharyngioma (n=7), optic pathway tumor (n=4), and germinoma (n=1). Seven patients receiving dexamethasone at the time of the evaluation were excluded from the final analysis. Results: Of 68 assessable patient, 45 (66%) had evidence of endocrinopathy before RT, including 15 of 32 patients (47%) with posterior fossa tumors. Of the 45 patients, 38% had growth hormone deficiency, 43% had thyroid-stimulating hormone secretion abnormality, 22% had an abnormality in ACTH reserve, and 13% had an abnormality in age-dependent gonadotropin secretion. Conclusion: The incidence of pre-RT endocrinopathy in pediatric brain tumor patients is high, including patients with tumors not adjacent to the hypothalamic-pituitary unit. These data suggest an overestimation in the incidence of radiation-induced endocrinopathy. Baseline endocrine function should be determined for brain tumor patients before therapy. The potential for radiation-induced endocrinopathy alone cannot be used as an argument for alternatives to RT for most patients. Pre-RT endocrinopathy may be an early indicator of central nervous system damage that will influence the functional outcome unrelated to RT

  10. Recovery coefficients for the quantification of the arterial input function from dynamic pet measurements: experimental and theoretical determination

    International Nuclear Information System (INIS)

    Brix, G.; Bellemann, M.E.; Hauser, H.; Doll, J.

    2002-01-01

    Aim: For kinetic modelling of dynamic PET data, the arterial input function can be determined directly from the PET scans if a large artery is visualized on the images. It was the purpose of this study to experimentally and theoretically determine recovery coefficients for cylinders as a function of the diameter and level of background activity. Methods: The measurements were performed using a phantom with seven cylinder inserts (φ = 5-46 mm). The cylinders were filled with an aqueous 68 Ga solution while the main chamber was filled with a 18 F solution in order to obtain a varying concentration ratio between the cylinders and the background due to the different isotope half lives. After iterative image reconstruction, the activity concentrations were measured in the center of the cylinders and the recovery coefficients were calculated as a function of the diameter and the background activity. Based on the imaging properties of the PET system, we also developed a model for the quantitative assessment of recovery coefficients. Results: The functional dependence of the measured recovery data from the cylinder diameter and the concentration ratio is well described by our model. For dynamic PET measurements, the recovery correction must take into account the decreasing concentration ratio between the blood vessel and the surrounding tissue. Under the realized measurement and data analysis conditions, a recovery correction is required for vessels with a diameter of up to 25 mm. Conclusions: Based on the experimentally verified model, the activity concentration in large arteries can be calculated from the measured activity concentration in the blood vessel and the background activity. The presented approach offers the possibility to determine the arterial input function for pharmacokinetic PET studies non-invasively from large arteries (especially the aorta). (orig.) [de

  11. Dynamic Mechanical and Thermal Properties of Bagasse/Glass Fiber/Polypropylene Hybrid Composites

    Directory of Open Access Journals (Sweden)

    Mehdi Roohani

    2016-06-01

    Full Text Available This work aims to evaluate the thermal and dynamic mechanical properties of bagasse/glass fiber/polypropylene hybrid composites. Composites were prepared by the melt compounding method and their properties were characterized by differential scanning calorimetry (DSC and dynamic mechanical analysis (DMA. DSC results found that with incorporation of bagasse and glass fiber the melting temperature (Tm and the crystallisation temperature (Tc shift to higher temperatures and the degree of crystallinity (Xc increase. These findings suggest that the fibers played the role of a nucleating agent in composites. Dynamic mechanical analysis indicated that by the incorporation of bagasse and glass fiber into polypropylene, the storage modulus ( and the loss modulus ( increase whereas the mechanical loss factor (tanδ decrease. To assess the effect of reinforcement with increasing temperature, the effectiveness coefficient C was calculated at different temperature ranges and revealed that, at the elevated temperatures, improvement of mechanical properties due to the presence of fibers was more noticeable. The fiber-matrix adhesion efficiency determined by calculating of adhesion factor A in terms of the relative damping of the composite (tan δc and the polymer (tan δpand volume fraction of the fibers (Фf. Calculated adhesion factor A values indicated that by adding glass fiber to bagasse/polypropylene system, the fiber-matrix adhesion improve. Hybrid composite containing 25% bagasse and 15% glass fiber showed better fiber-matrix adhesion.

  12. Effect of molecular weight and testing rate on adhesion property of pressure-sensitive adhesives prepared from epoxidized natural rubber

    International Nuclear Information System (INIS)

    Khan, Imran; Poh, B.T.

    2011-01-01

    Research highlights: → Elucidation of adhesion property of epoxidized natural rubber (ENR 25). → Correlation of peel and shear strength with molecular weight and rate of testing. → Confirmation of miscibility of tackifier and ENR 25 by DSC and FTIR study. → Applicability of Fox equation in ENR 25/coumarone-indene resin system. -- Abstract: The dependence of peel strength and shear strength of epoxidized natural rubber (ENR 25)-based pressure-sensitive adhesive on molecular weight and rate of testing was investigated using coumarone-indene as the tackifying resin. Toluene and polyethylene terephthalate (PET) were used as the solvent and substrate respectively throughout the study. A SHEEN hand coater was used to coat the adhesive on the substrate at a coating thickness of 120 μm. All the adhesion properties were determined by a Llyod Adhesion Tester operating at different rates of testing. Result shows that peel strength and shear strength increases up to an optimum molecular weight of 6.5 x 10 4 of ENR 25. For peel strength, the observation is attributed to the combined effects of wettability and mechanical strength of rubber at the optimum molecular weight, whereas for the shear strength, it is ascribed to the increasing amount of adhesive present in the coating layer which enhances the shear resistance of the adhesive. Peel strength and shear strength also increases with increase in rate of testing, an observation which is associated to the viscoeslastic response of the adhesive. Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) study confirms the miscibility of tackifier and the ENR 25.

  13. Lap Shear and Impact Testing of Ochre and Beeswax in Experimental Middle Stone Age Compound Adhesives

    Science.gov (United States)

    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. PMID:26983080

  14. Lap Shear and Impact Testing of Ochre and Beeswax in Experimental Middle Stone Age Compound Adhesives.

    Directory of Open Access Journals (Sweden)

    P R B Kozowyk

    Full Text Available 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.

  15. 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

  16. Cardiovascular diseases in the developing countries: dimensions, determinants, dynamics and directions for public health action.

    Science.gov (United States)

    Reddy, K Srinath

    2002-02-01

    The global burden of disease due to cardiovascular diseases (CVDs) is escalating, principally due to a sharp rise in the developing countries which are experiencing rapid health transition. Contributory causes include: demographic shifts with altered population age profiles; lifestyle changes due to recent urbanisation, delayed industrialisation and overpowering globalisation; probable effects of foetal undernutrition on adult susceptibility to vascular disease and possible gene-environment interactions influencing ethnic diversity. Altered diets and diminished physical activity are critical factors contributing to the acceleration of CVD epidemics, along with tobacco use. The pace of health transition, however, varies across developing regions with consequent variations in the relative burdens of the dominant CVDs. A comprehensive public health response must integrate policies and programmes that effectively impact on the multiple determinants of these diseases and provide protection over the life span through primordial, primary and secondary prevention. Populations as well as individuals at risk must be protected through initiatives that espouse and enable nutrition-based preventive strategies to protect and promote cardiovascular health. An empowered community, an enlightened policy and an energetic coalition of health professionals must ensure that development is not accompanied by distorted nutrition and disordered health.

  17. Dynamic modulus of rigidity of seven types of Mexican wood determined by torsional vibration

    Directory of Open Access Journals (Sweden)

    Javier R. Sotomayor-Castellanos

    2016-01-01

    Full Text Available El módulo de rigidez de la madera es útil para el cálculo estructural y la elaboración de productos derivados de la misma. El objetivo de esta investigación fue determinar los módulos de rigidez en el plano longitudinal tangencial (G LT de siete especies de maderas mexicanas ( Enterolobium cyclocarpum , Tabebuia donnell-smithii , T. rosea , Swietenia humilis , Lysiloma acapulcensis , Cordia elaeagnoides y T. chrysantha , realizando pruebas de vibraciones en torsión. También se determin ó l a densidad, el contenido de humedad y la frecuencia natural de probetas de pequeñas dimensiones. Los valores del G LT de las siete especies fueron similares a los módulos propuestos en estudios ya realizados con maderas de densidad y contenido de humedad comparables. Los módulos de rigidez variaron entre 695 MPa ( E. cyclocarpum y 2,807 MPa ( T. chrysantha . Los valores de cada especie oscilaron alrededor de la predicción lineal propuesta a través del modelo elástico de la madera. La densidad y la frecuencia natural de vibraciones en torsión son predictores del módulo de rigidez dinámico con coeficientes de determinación de 0.98 y 0.81, respectivamente.

  18. Mic60/Mitofilin determines MICOS assembly essential for mitochondrial dynamics and mtDNA nucleoid organization.

    Science.gov (United States)

    Li, H; Ruan, Y; Zhang, K; Jian, F; Hu, C; Miao, L; Gong, L; Sun, L; Zhang, X; Chen, S; Chen, H; Liu, D; Song, Z

    2016-03-01

    The MICOS complex (mitochondrial contact site and cristae organizing system) is essential for mitochondrial inner membrane organization and mitochondrial membrane contacts, however, the molecular regulation of MICOS assembly and the physiological functions of MICOS in mammals remain obscure. Here, we report that Mic60/Mitofilin has a critical role in the MICOS assembly, which determines the mitochondrial morphology and mitochondrial DNA (mtDNA) organization. The downregulation of Mic60/Mitofilin or Mic19/CHCHD3 results in instability of other MICOS components, disassembly of MICOS complex and disorganized mitochondrial cristae. We show that there exists direct interaction between Mic60/Mitofilin and Mic19/CHCHD3, which is crucial for their stabilization in mammals. Importantly, we identified that the mitochondrial i-AAA protease Yme1L regulates Mic60/Mitofilin homeostasis. Impaired MICOS assembly causes the formation of 'giant mitochondria' because of dysregulated mitochondrial fusion and fission. Also, mtDNA nucleoids are disorganized and clustered in these giant mitochondria in which mtDNA transcription is attenuated because of remarkable downregulation of some key mtDNA nucleoid-associated proteins. Together, these findings demonstrate that Mic60/Mitofilin homeostasis regulated by Yme1L is central to the MICOS assembly, which is required for maintenance of mitochondrial morphology and organization of mtDNA nucleoids.

  19. Review of test methods for coating adhesion

    International Nuclear Information System (INIS)

    Maxwell, A.S.

    2001-01-01

    The following report summarises the results of a literature search and a series of industrial surveys that have been conducted to determine the current status of test methods for the measurement of coating adhesion. The review consists of: a list of test methods that have been identified from current scientific literature; a short description of the methodologies used in industry; a review of applicable standards; a summary of recent scientific reviews; and the results from two recent industrial surveys conducted by the National Physical Laboratory (NPL) and the National Institute of Standards and Technology (NIST) into current industrial practice. (author)

  20. Polyurethane adhesives in flat roofs

    Directory of Open Access Journals (Sweden)

    Bogárová Markéta

    2017-01-01

    Full Text Available It is necessary to stabilize individual layers of flat roofs, mainly because of wind suction. Apart from anchoring and surcharge, these layers can be secured by bonding. At present gluing is an indispensable and widely used stabilization method. On our market we can found many types of adhesives, most widely used are based on polyurethane. This paper focuses on problematic about stabilization thermal insulation from expanded polystyrene to vapor barrier from bitumen. One of the main issues is to calculate the exact amount of adhesive, which is required to guarantee the resistance against wind suction. In this problematic we can not find help neither in technical data sheets provided by the manufactures. Some of these data sheets contain at least information about amount of adhesive depending on location in roof plane and building height, but they do not specify the strength of such connection. It was therefore resorted to select several representatives polyurethane adhesives and their subsequent testing on specimens simulating the flat roof segment. The paper described the test methodology and results for two types of polyurethane adhesives.

  1. Defining Determinants and Dynamics and Cellulose Microfibril Biosynthesis, Assembly and Degredation OSP Number: 63079/A001

    Energy Technology Data Exchange (ETDEWEB)

    None, None

    2013-12-01

    The central paradigm for converting plant biomass into soluble sugars for subsequent conversion to transportation fuels involves the enzymatic depolymerization of lignocellulosic plant cell walls by microbial enzymes. Despite decades of intensive research, this is still a relatively inefficient process, due largely to the recalcitrance and enormous complexity of the substrate. A major obstacle is still insufficient understanding of the detailed structure and biosynthesis of major wall components, including cellulose. For example, although cellulose is generally depicted as rigid, insoluble, uniformly crystalline microfibrils that are resistant to enzymatic degradation, the in vivo structures of plant cellulose microfibrils are surprisingly complex. Crystallinity is frequently disrupted, for example by dislocations and areas containing chain ends, resulting in “amorphous” disordered regions. Importantly, microfibril structure and the relative proportions of crystalline and non-crystalline disordered surface regions vary substantially and yet the molecular mechanisms by which plants regulate microfibril crystallinity, and other aspects of microfibril architecture, are still entirely unknown. This obviously has a profound effect on susceptibility to enzymatic hydrolysis and so this is a critical area of research in order to characterize and optimize cellulosic biomass degradation. The entire field of cell wall assembly, as distinct from polysaccharide biosynthesis, and the degree to which they are coupled, are relatively unexplored, despite the great potential for major advances in addressing the hurdle of biomass recalcitrance. Our overarching hypothesis was that identification of the molecular machinery that determine microfibril polymerization, deposition and structure will allow the design of more effective degradative systems, and the generation of cellulosic materials with enhanced and predictable bioconversion characteristics. Our experimental framework had

  2. A Study of the Effects of Relative Humidity on Small Particle Adhesion to Surfaces

    Science.gov (United States)

    Whitfield, W. J.; David, T.

    1971-01-01

    Ambient dust ranging in size from less than one micron up to 140 microns was used as test particles. Relative humidities of 33% to 100% were used to condition test surfaces after loading with the test particles. A 20 psi nitrogen blowoff was used as the removal mechanism to test for particle adhesion. Particles were counted before and after blowoff to determine retention characteristics. Particle adhesion increased drastically as relative humidity increased above 50%. The greatest adhesion changes occurred within the first hour of conditioning time. Data are presented for total particle adhesion, for particles 10 microns and larger, and 50 microns and larger.

  3. Adhesion of food-borne bacteria to stainless steel is reduced by food conditioning films

    DEFF Research Database (Denmark)

    Bernbom, Nete; Ng, Yin; Jorgensen, R.L.

    2009-01-01

    also decreases adhesion of other food-relevant bacteria. The manipulation of adhesion was not attributable to growth inhibitory effects. Chemical analysis revealed that the stainless steels were covered by homogenous layers of adsorbed proteins. The presence of tropomyocin was indicated by appearance......Preconditioning of stainless steel with aqueous cod muscle extract significantly impedes subsequent bacterial adhesion most likely due to repelling effects of fish tropomyosin. The purpose of this study was to determine if other food conditioning films decrease or enhance bacterial adhesion...

  4. Interface failure and adhesion measured by focused ion beam cutting of metal-polymer interfaces

    Science.gov (United States)

    Cordill, M. J.; Schmidegg, K.; Dehm, G.

    2011-08-01

    New developments in flexible electronics require metal films to adhere to polymer substrates. Measuring the interfacial adhesion of these systems is challenging, requiring the formulation of new techniques and models. A strategy to measure the adhesion of Cr-polyethylene terephthalate (PET) interfaces using tensile straining and buckle formation is presented in this article. Focused ion beam cross-sectioning of the buckles reveals that the polymer substrate can locally fail, which may lead to an overestimate of adhesion. Cr-PET adhesion energy of 9.4 ± 1.6 J/m2 is determined with the present approach.

  5. Population Dynamics of Staphylococcus aureus in Cystic Fibrosis Patients To Determine Transmission Events by Use of Whole-Genome Sequencing.

    Science.gov (United States)

    Ankrum, Andrea; Hall, Barry G

    2017-07-01

    Strict infection control practices have been implemented for health care visits by cystic fibrosis (CF) patients in an attempt to prevent transmission of important pathogens. This study used whole-genome sequencing (WGS) to determine strain relatedness and assess population dynamics of Staphylococcus aureus isolates from a cohort of CF patients as assessed by strain relatedness. A total of 311 S. aureus isolates were collected from respiratory cultures of 115 CF patients during a 22-month study period. Whole-genome sequencing was performed, and using single nucleotide polymorphism (SNP) analysis, phylogenetic trees were assembled to determine relatedness between isolates. Methicillin-resistant Staphylococcus aureus (MRSA) phenotypes were predicted using PPFS2 and compared to the observed phenotype. The accumulation of SNPs in multiple isolates obtained over time from the same patient was examined to determine if a genomic molecular clock could be calculated. Pairs of isolates with ≤71 SNP differences were considered to be the "same" strain. All of the "same" strain isolates were either from the same patient or siblings pairs. There were 47 examples of patients being superinfected with an unrelated strain. The predicted MRSA phenotype was accurate in all but three isolates. Mutation rates were unable to be determined because the branching order in the phylogenetic tree was inconsistent with the order of isolation. The observation that transmissions were identified between sibling patients shows that WGS is an effective tool for determining transmission between patients. The observation that transmission only occurred between siblings suggests that Staphylococcus aureus acquisition in our CF population occurred outside the hospital environment and indicates that current infection prevention efforts appear effective. Copyright © 2017 American Society for Microbiology.

  6. Study on Adhesion Strength of clear Coatings in Beech -Furfuryl alcohol wood polymer

    Directory of Open Access Journals (Sweden)

    Aisona Talaei

    2016-06-01

    Full Text Available The objective of this study was to determine the influence of Furfurylation treatment on adhesion strength of clear coatings and surface roughness of Beech (Fagus orientalis wood. Furfurylation of specimens were performed by impregnation and heat catalyze up to 20% and 65% weight percent gain. Half of the specimens coated with acid catalyst paint and half of them coated with polyurethane based paint. Surface roughness and adhesion strength (Pull-off and cross-hatch cutter test were analysed and compared to untreated specimens. Results revealed that 20% furfurylated specimens did not show significant difference in roughness and adhesion strength, compared to untreated control. But 65% furfurylated specimens caused decline in adhesion strength and raise in surface roughness. Polyurethane based paint had better efficiency and adhesion strength than acid catalyst paint. The highest adhesion strength observed in 20% furfurylated specimens coated with polyurethane and the least obtained in 65% furfurylated wood coated with acid catalyst paint.

  7. Simultaneous determination of arterial input function of the internal carotid and middle cerebral arteries for dynamic susceptibility contrast MRI

    International Nuclear Information System (INIS)

    Scholdei, R.; Wenz, F.; Fuss, M.; Essig, M.; Knopp, M.V.

    1999-01-01

    Purpose: The determination of the arterial input function (AIF) is necessary for absolute quantification of the regional cerebral blood volume and blood flow using dynamic susceptibility contrast MRI. The suitability of different vessels (ICA-internal carotid artery, MCA-middle cerebral artery) for AIF determination was compared in this study. Methods: A standard 1.5 T MR system and a simultaneous dual FLASH sequence (TR/TE1/TE2/α=32/15/25/10 ) were used to follow a bolus of contrast agent. Slice I was chosen to cut the ICA perpendicularly. Slice II included the MCA. Seventeen data sets from ten subjects were evaluated. Results: The number of AIF-relevant pixels, the area under the AIF and the maximum concentration were all lower when the AIF was determined from the MCA compared to the ICA. Additionally, the mean transit time (MTT) and the time to maximum concentration (TTM) were longer in the MCA, complicating the computerized identification of AIF-relevant pixels. Data from one subject, who was examined five times, demonstrated that the intraindividual variance of the measured parameters was markedly lower than the interpersonal variance. Conclusions: It appears to be advantageous to measure the AIF in the ICA rather than the MCA. (orig.) [de

  8. Solution Method and Precision Analysis of Double-difference Dynamic Precise Orbit Determination of BeiDou Navigation Satellite System

    Directory of Open Access Journals (Sweden)

    LIU Weiping

    2016-02-01

    Full Text Available To resolve the high relativity between the transverse element of GEO orbit and double-difference ambiguity, the classical double-difference dynamic method is improved and the method, which is to determine precise BeiDou satellite orbit using carrier phase and pseudo-range smoothed by phase, is proposed. The feasibility of the method is discussed and the influence of the method about ambiguity fixing is analyzed. Considering the characteristic of BeiDou, the method, which is to fix double-difference ambiguity of BeiDou satellites by QIF, is derived. The real data analysis shows that the new method, which can reduce the relativity and assure the precision, is better than the classical double-difference dynamic method. The result of ambiguity fixing is well by QIF, but the ambiguity fixing success rate is not high on the whole. So the precision of BeiDou orbit can't be improved clearly after ambiguity fixing.

  9. Focal adhesion kinase-dependent focal adhesion recruitment of SH2 domains directs SRC into focal adhesions to regulate cell adhesion and migration

    Science.gov (United States)

    Wu, Jui-Chung; Chen, Yu-Chen; Kuo, Chih-Ting; Wenshin Yu, Helen; Chen, Yin-Quan; Chiou, Arthur; Kuo, Jean-Cheng

    2015-01-01

    Directed cell migration requires dynamical control of the protein complex within focal adhesions (FAs) and this control is regulated by signaling events involving tyrosine phosphorylation. We screened the SH2 domains present in tyrosine-specific kinases and phosphatases found within FAs, including SRC, SHP1 and SHP2, and examined whether these enzymes transiently target FAs via their SH2 domains. We found that the SRC_SH2 domain and the SHP2_N-SH2 domain are associated with FAs, but only the SRC_SH2 domain is able to be regulated by focal adhesion kinase (FAK). The FAK-dependent association of the SRC_SH2 domain is necessary and sufficient for SRC FA targeting. When the targeting of SRC into FAs is inhibited, there is significant suppression of SRC-mediated phosphorylation of paxillin and FAK; this results in an inhibition of FA formation and maturation and a reduction in cell migration. This study reveals an association between FAs and the SRC_SH2 domain as well as between FAs and the SHP2_N-SH2 domains. This supports the hypothesis that the FAK-regulated SRC_SH2 domain plays an important role in directing SRC into FAs and that this SRC-mediated FA signaling drives cell migration. PMID:26681405

  10. Effect of double-layer application on bond quality of adhesive systems.

    Science.gov (United States)

    Fujiwara, Satoshi; Takamizawa, Toshiki; Barkmeier, Wayne W; Tsujimoto, Akimasa; Imai, Arisa; Watanabe, Hidehiko; Erickson, Robert L; Latta, Mark A; Nakatsuka, Toshiyuki; Miyazaki, Masashi

    2018-01-01

    The aim of this study was to determine the effect of double-layer application of universal adhesives on the bond quality and compare to other adhesive systems. Two universal adhesives used were in this study: Scotchbond Universal (SU), [3M ESPE] and Prime & Bond elect (PE), [Dentsply Caulk]. The conventional single-step self-etch adhesives G-ӕnial Bond (GB), [GC Corporation.] and BeautiBond (BB), [Shofu Inc.], and a two-step self-etch adhesive, Optibond XTR (OX), [Kerr Corporation], were used as comparison adhesives. Shear bond strengths (SBS) and shear fatigue strengths (SFS) to human enamel and dentin were measured in single application mode and double application mode. For each test condition, 15 specimens were prepared for SBS testing and 30 specimens for SFS testing. Enamel and dentin SBS of the universal adhesives in the double application mode were significantly higher than those of the single application mode. In addition, the universal adhesives in the double application mode had significantly higher dentin SFS values than those of the single application mode. The two-step self-etch adhesive OX tended to have lower bond strengths in the double application mode, regardless of the test method or adherent substrate. The double application mode is effective in enhancing SBS and SFS of universal adhesives, but not conventional two-step self-etch adhesives. These results suggest that, although the double application mode may enhance the bonding quality of a universal adhesive, it may be counter-productive for two-step self-etch adhesives in clinical use. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. INFLUENCE OF DOXORUBICIN ON ADHESIVE PROPERTIES OF E.COLI

    Directory of Open Access Journals (Sweden)

    O.G. Shapoval

    2008-09-01

    Full Text Available Influence ofantineoplastic drug doxorubicin and amikacin, the aminoglycoside family on adhesive activity of Escherichia coli was studied. Antimicrobialactivity(minimum inhibitory concentration-MIC ofboth drugs against experimental strains using serial two-fold dilution method was determined. Susceptibility of E.coli to amikacin in the presence of Sand j MIC doxorubicin was studied. After 10 passages in beef-extract broth with constant and increasing doxorubicin concentrations in the presence of Sand j MIC doxorubicin, the adhesive activity of initial and passage variants according to theirability to absorb human erythrocytes 1(0 Rh+ was determined. Itwas observed that experimental strains were susceptible to amikacin (MIC 1,5-6,2 mkg/ml butwere resistantto doxorubicin (MIC 1000 mkg/ml. Subinhibitory concentrations of this cytostatic (S and j MIC raised the sensitivity of experimental strains to amikacin and differently effected on adhesive activity of passage variants of E.coli.

  12. Raster image correlation spectroscopy (RICS) for measuring fast protein dynamics and concentrations with a commercial laser scanning confocal microscope.

    Science.gov (United States)

    Brown, C M; Dalal, R B; Hebert, B; Digman, M A; Horwitz, A R; Gratton, E

    2008-01-01

    Raster image correlation spectroscopy (RICS) is a new and novel technique for measuring molecular dynamics and concentrations from fluorescence confocal images. The RICS technique extracts information about molecular dynamics and concentrations from images of living cells taken on commercial confocal systems. Here we develop guidelines for performing the RICS analysis on an analogue commercial laser scanning confocal microscope. Guidelines for typical instrument settings, image acquisition settings and analogue detector characterization are presented. Using appropriate instrument/acquisition parameters, diffusion coefficients and concentrations can be determined, even for highly dynamic dye molecules in solution. Standard curves presented herein demonstrate the ability to detect protein concentrations as low as approximately 2 nM. Additionally, cellular measurements give accurate values for the diffusion of paxillin-enhanced-green fluorescent protein (EGFP), an adhesion adaptor molecule, in the cytosol of the cell and also show slower paxillin dynamics near adhesions where paxillin interacts with immobile adhesion components. Methods are presented to account for bright immobile structures within the cell that dominate spatial correlation functions; allowing the extraction of fast protein dynamics within and near these structures. A running average algorithm is also presented to address slow cellular movement or movement of cellular features such as adhesions. Finally, methods to determine protein concentration in the presence of immobile structures within the cell are presented. A table is presented giving guidelines for instrument and imaging setting when performing RICS on the Olympus FV300 confocal and these guidelines are a starting point for performing the analysis on other commercial confocal systems.

  13. THE DETERMINATION OF A CRITICAL VALUE FOR DYNAMIC STABILITY OF SEMICONDUCTOR LASER DIODE WITH EXTERNAL OPTICAL FEEDBACK

    Directory of Open Access Journals (Sweden)

    Remzi YILDIRIM

    1998-01-01

    Full Text Available In this study, dynamic stability analysis of semiconductor laser diodes with external optical feedback has been realized. In the analysis the frequency response of the transfer function of laser diode H jw( , the transfer m function of laser diode with external optical feedback TF jw( , and optical feedback transfer function m K jw( obtained from small signal equations has been m accomplished using Nyquist stability analysis in complex domain. The effect of optical feedback on the stability of the system has been introduced and to bring the laser diode to stable condition the working critical boundary range of dampig frequency and reflection power constant (R has been determined. In the study the reflection power has been taken as ( .

  14. Using cell-substrate impedance and live cell imaging to measure real-time changes in cellular adhesion and de-adhesion induced by matrix modification.

    Science.gov (United States)

    Rees, Martin D; Thomas, Shane R

    2015-02-19

    Cell-matrix adhesion plays a key role in controlling cell morphology and signaling. Stimuli that disrupt cell-matrix adhesion (e.g., myeloperoxidase and other matrix-modifying oxidants/enzymes released during inflammation) are implicated in triggering pathological changes in cellular function, phenotype and viability in a number of diseases. Here, we describe how cell-substrate impedance and live cell imaging approaches can be readily employed to accurately quantify real-time changes in cell adhesion and de-adhesion induced by matrix modification (using endothelial cells and myeloperoxidase as a pathophysiological matrix-modifying stimulus) with high temporal resolution and in a non-invasive manner. The xCELLigence cell-substrate impedance system continuously quantifies the area of cell-matrix adhesion by measuring the electrical impedance at the cell-substrate interface in cells grown on gold microelectrode arrays. Image analysis of time-lapse differential interference contrast movies quantifies changes in the projected area of individual cells over time, representing changes in the area of cell-matrix contact. Both techniques accurately quantify rapid changes to cellular adhesion and de-adhesion processes. Cell-substrate impedance on microelectrode biosensor arrays provides a platform for robust, high-throughput measurements. Live cell imaging analyses provide additional detail regarding the nature and dynamics of the morphological changes quantified by cell-substrate impedance measurements. These complementary approaches provide valuable new insights into how myeloperoxidase-catalyzed oxidative modification of subcellular extracellular matrix components triggers rapid changes in cell adhesion, morphology and signaling in endothelial cells. These approaches are also applicable for studying cellular adhesion dynamics in response to other matrix-modifying stimuli and in related adherent cells (e.g., epithelial cells).

  15. Modified silyl-terminated polyether polymer blends with bisphenol A diglycidyl ether epoxy for adhesive applications

    International Nuclear Information System (INIS)

    Bitenieks, J; Meri, R Merijs; Zicans, J; Berzins, R; Umbraško, J; Rekners, U

    2016-01-01

    Modified silyl-terminated polyether polymer (MS Polymer) was blended with bisphenol A diglycidyl ether (DGEBPA) epoxy at MS Polymer/epoxy ratio from 30/70 to 70/30. MS Polymer/epoxy systems were examined for two-component adhesive formulation with additional fillers. Applicability of the MS Polymer/epoxy system at the ratio of the components 60/40 is demonstrated for the development of adhesive formulation. Rheological analysis of the components A and B shows suitable viscosity values for development of two- component adhesives formulation. Curing dynamics as well as tensile stress-strain properties and Shore A hardness of the chosen adhesive formulation are reasonable for the development of MS Polymer/epoxy type adhesive. (paper)

  16. Integrative systems and synthetic biology of cell-matrix adhesion sites.

    Science.gov (United States)

    Zamir, Eli

    2016-09-02

    The complexity of cell-matrix adhesion convolves its roles in the development and functioning of multicellular organisms and their evolutionary tinkering. Cell-matrix adhesion is mediated by sites along the plasma membrane that anchor the actin cytoskeleton to the matrix via a large number of proteins, collectively called the integrin adhesome. Fundamental challenges for understanding how cell-matrix adhesion sites assemble and function arise from their multi-functionality, rapid dynamics, large number of components and molecular diversity. Systems biology faces these challenges in its strive to understand how the integrin adhesome gives rise to functional adhesion sites. Synthetic biology enables engineering intracellular modules and circuits with properties of interest. In this review I discuss some of the fundamental questions in systems biology of cell-matrix adhesion and how synthetic biology can help addressing them.

  17. Membrane tension controls adhesion positioning at the leading edge of cells

    Science.gov (United States)

    Pontes, Bruno; Gole, Laurent; Kosmalska, Anita Joanna; Tam, Zhi Yang; Luo, Weiwei; Kan, Sophie; Viasnoff, Virgile; Roca-Cusachs, Pere; Tucker-Kellogg, Lisa

    2017-01-01

    Cell migration is dependent on adhesion dynamics and actin cytoskeleton remodeling at the leading edge. These events may be physically constrained by the plasma membrane. Here, we show that the mechanical signal produced by an increase in plasma membrane tension triggers the positioning of new rows of adhesions at the leading edge. During protrusion, as membrane tension increases, velocity slows, and the lamellipodium buckles upward in a myosin II–independent manner. The buckling occurs between the front of the lamellipodium, where nascent adhesions are positioned in rows, and the base of the lamellipodium, where a vinculin-dependent clutch couples actin to previously positioned adhesions. As membrane tension decreases, protrusion resumes and buckling disappears, until the next cycle. We propose that the mechanical signal of membrane tension exerts upstream control in mechanotransduction by periodically compressing and relaxing the lamellipodium, leading to the positioning of adhesions at the leading edge of cells. PMID:28687667

  18. Surface adhesion and its dependence on surface roughness and humidity measured with a flat AFM tip

    NARCIS (Netherlands)

    Colak, A.; Wormeester, Herbert; Zandvliet, Henricus J.W.; Poelsema, Bene

    2012-01-01

    The adhesion force between a surface and the tip of an atomic force microscope cantilever has been determined by recording force–distance curves with an atomic force microscope. Flat tips with a diameter of 2 μm were used to mimic the adhesion between two parallel surfaces. In such a configuration,

  19. 77 FR 59090 - Approval and Promulgation of Air Quality Implementation Plans; Pennsylvania; Adhesives and...

    Science.gov (United States)

    2012-09-26

    ... state and local air pollution control agencies to consider in determining RACT. State and local pollution control agencies are free to implement other technically-sound approaches that are consistent with... Industrial Adhesive CTG. EPA's Miscellaneous Industrial Adhesive CTG provides state and local air pollution...

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

    NARCIS (Netherlands)

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

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