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Sample records for advancing contact angles

  1. Equilibrium contact angle or the most-stable contact angle?

    PubMed

    Montes Ruiz-Cabello, F J; Rodríguez-Valverde, M A; Cabrerizo-Vílchez, M A

    2014-04-01

    It is well-established that the equilibrium contact angle in a thermodynamic framework is an "unattainable" contact angle. Instead, the most-stable contact angle obtained from mechanical stimuli of the system is indeed experimentally accessible. Monitoring the susceptibility of a sessile drop to a mechanical stimulus enables to identify the most stable drop configuration within the practical range of contact angle hysteresis. Two different stimuli may be used with sessile drops: mechanical vibration and tilting. The most stable drop against vibration should reveal the changeless contact angle but against the gravity force, it should reveal the highest resistance to slide down. After the corresponding mechanical stimulus, once the excited drop configuration is examined, the focus will be on the contact angle of the initial drop configuration. This methodology needs to map significantly the static drop configurations with different stable contact angles. The most-stable contact angle, together with the advancing and receding contact angles, completes the description of physically realizable configurations of a solid-liquid system. Since the most-stable contact angle is energetically significant, it may be used in the Wenzel, Cassie or Cassie-Baxter equations accordingly or for the surface energy evaluation.

  2. Hysteresis during contact angles measurement.

    PubMed

    Diaz, M Elena; Fuentes, Javier; Cerro, Ramon L; Savage, Michael D

    2010-03-15

    A theory, based on the presence of an adsorbed film in the vicinity of the triple contact line, provides a molecular interpretation of intrinsic hysteresis during the measurement of static contact angles. Static contact angles are measured by placing a sessile drop on top of a flat solid surface. If the solid surface has not been previously in contact with a vapor phase saturated with the molecules of the liquid phase, the solid surface is free of adsorbed liquid molecules. In the absence of an adsorbed film, molecular forces configure an advancing contact angle larger than the static contact angle. After some time, due to an evaporation/adsorption process, the interface of the drop coexists with an adsorbed film of liquid molecules as part of the equilibrium configuration, denoted as the static contact angle. This equilibrium configuration is metastable because the droplet has a larger vapor pressure than the surrounding flat film. As the drop evaporates, the vapor/liquid interface contracts and the apparent contact line moves towards the center of the drop. During this process, the film left behind is thicker than the adsorbed film and molecular attraction results in a receding contact angle, smaller than the equilibrium contact angle.

  3. Apparent dynamic contact angle of an advancing gas--liquid meniscus

    SciTech Connect

    Kalliadasis, S.; Chang, H. )

    1994-01-01

    The steady motion of an advancing meniscus in a gas-filled capillary tube involves a delicate balance of capillary, viscous, and intermolecular forces. The limit of small capillary numbers Ca (dimensionless speeds) is analyzed here with a matched asymptotic analysis that links the outer capillary region to the precursor film in front of the meniscus through a lubricating film. The meniscus shape in the outer region is constructed and the apparent dynamic contact angle [Theta] that the meniscus forms with the solid surface is derived as a function of the capillary number, the capillary radius, and the Hamaker's constant for intermolecular forces, under conditions of weak gas--solid interaction, which lead to fast spreading of the precursor film and weak intermolecular forces relative to viscous forces within the lubricating film. The dependence on intermolecular forces is very weak and the contact angle expression has a tight upper bound tan [Theta]=7.48 Ca[sup 1/3] for thick films, which is independent of the Hamaker constant. This upper bound is in very good agreement with existing experimental data for wetting fluids in any capillary and for partially wetting fluids in a prewetted capillary. Significant correction to the Ca[sup 1/3] dependence occurs only at very low Ca, where the intermolecular forces become more important and tan [Theta] diverges slightly from the above asymptotic behavior toward lower values.

  4. Dynamic contact angle measurements on superhydrophobic surfaces

    NASA Astrophysics Data System (ADS)

    Kim, Jeong-Hyun; Kavehpour, H. Pirouz; Rothstein, Jonathan P.

    2015-03-01

    In this paper, the dynamic advancing and receding contact angles of a series of aqueous solutions were measured on a number of hydrophobic and superhydrophobic surfaces using a modified Wilhelmy plate technique. Superhydrophobic surfaces are hydrophobic surfaces with micron or nanometer sized surface roughness. These surfaces have very large static advancing contact angles and little static contact angle hysteresis. In this study, the dynamic advancing and dynamic receding contact angles on superhydrophobic surfaces were measured as a function of plate velocity and capillary number. The dynamic contact angles measured on a smooth hydrophobic Teflon surface were found to obey the scaling with capillary number predicted by the Cox-Voinov-Tanner law, θD3 ∝ Ca. The response of the dynamic contact angle on the superhydrophobic surfaces, however, did not follow the same scaling law. The advancing contact angle was found to remain constant at θA = 160∘, independent of capillary number. The dynamic receding contact angle measurements on superhydrophobic surfaces were found to decrease with increasing capillary number; however, the presence of slip on the superhydrophobic surface was found to result in a shift in the onset of dynamic contact angle variation to larger capillary numbers. In addition, a much weaker dependence of the dynamic contact angle on capillary number was observed for some of the superhydrophobic surfaces tested.

  5. Statistical analysis of Contact Angle Hysteresis

    NASA Astrophysics Data System (ADS)

    Janardan, Nachiketa; Panchagnula, Mahesh

    2015-11-01

    We present the results of a new statistical approach to determining Contact Angle Hysteresis (CAH) by studying the nature of the triple line. A statistical distribution of local contact angles on a random three-dimensional drop is used as the basis for this approach. Drops with randomly shaped triple lines but of fixed volumes were deposited on a substrate and their triple line shapes were extracted by imaging. Using a solution developed by Prabhala et al. (Langmuir, 2010), the complete three dimensional shape of the sessile drop was generated. A distribution of the local contact angles for several such drops but of the same liquid-substrate pairs is generated. This distribution is a result of several microscopic advancing and receding processes along the triple line. This distribution is used to yield an approximation of the CAH associated with the substrate. This is then compared with measurements of CAH by means of a liquid infusion-withdrawal experiment. Static measurements are shown to be sufficient to measure quasistatic contact angle hysteresis of a substrate. The approach also points towards the relationship between microscopic triple line contortions and CAH.

  6. Dynamic contact angle cycling homogenizes heterogeneous surfaces.

    PubMed

    Belibel, R; Barbaud, C; Mora, L

    2016-12-01

    In order to reduce restenosis, the necessity to develop the appropriate coating material of metallic stent is a challenge for biomedicine and scientific research over the past decade. Therefore, biodegradable copolymers of poly((R,S)-3,3 dimethylmalic acid) (PDMMLA) were prepared in order to develop a new coating exhibiting different custom groups in its side chain and being able to carry a drug. This material will be in direct contact with cells and blood. It consists of carboxylic acid and hexylic groups used for hydrophilic and hydrophobic character, respectively. The study of this material wettability and dynamic surface properties is of importance due to the influence of the chemistry and the potential motility of these chemical groups on cell adhesion and polymer kinetic hydrolysis. Cassie theory was used for the theoretical correction of contact angles of these chemical heterogeneous surfaces coatings. Dynamic Surface Analysis was used as practical homogenizer of chemical heterogeneous surfaces by cycling during many cycles in water. In this work, we confirmed that, unlike receding contact angle, advancing contact angle is influenced by the difference of only 10% of acidic groups (%A) in side-chain of polymers. It linearly decreases with increasing acidity percentage. Hysteresis (H) is also a sensitive parameter which is discussed in this paper. Finally, we conclude that cycling provides real information, thus avoiding theoretical Cassie correction. H(10)is the most sensible parameter to %A. PMID:27612817

  7. A new procedure for measuring contact angle

    SciTech Connect

    Concus, P.; Finn, R.

    1994-05-01

    Described here are some recent work regarding the mathematic design of apparatus that exploits microgravity conditions for accurate experimental determination of contact angle. The underlying motivation for the procedures rests on a discontinuous dependence of the capillary free surface interface S on the contact angle {gamma}, in a cylindrical capillary tube whose section (base) {Omega} contains a protruding corner with opening angle 2{alpha}.

  8. High contact angle hysteresis of superhydrophobic surfaces: Hydrophobic defects

    NASA Astrophysics Data System (ADS)

    Chang, Feng-Ming; Hong, Siang-Jie; Sheng, Yu-Jane; Tsao, Heng-Kwong

    2009-08-01

    A typical superhydrophobic surface is essentially nonadhesive and exhibits very low water contact angle (CA) hysteresis, so-called Lotus effect. However, leaves of some plants such as scallion and garlic with an advancing angle exceeding 150° show very serious CA hysteresis. Although surface roughness and epicuticular wax can explain the very high advancing CA, our analysis indicates that the unusual hydrophobic defect, diallyl disulfide, is the key element responsible for contact line pinning on allium leaves. After smearing diallyl disulfide on an extended polytetrafluoroethylene (PTFE) film, which is originally absent of CA hysteresis, the surface remains superhydrophobic but becomes highly adhesive.

  9. Water contact angles and hysteresis of polyamide surfaces.

    PubMed

    Extrand, C W

    2002-04-01

    The wetting behavior of a series of aliphatic polyamides (PAs) has been examined. PAs with varying amide content and polyethylene (PE) were molded against glass to produce surfaces with similar roughness. After cleaning, chemical composition of the surfaces was verified with X-ray photoelectron spectroscopy. Advancing and receding contact angles were measured from small sessile water drops. Contact angles decreased with amide content while hysteresis increased. Hysteresis arose primarily from molecular interactions between the contact liquid and the solid substrates, rather than moisture absorption, variations in crystallinity, surface deformation, roughness, reorientation of amide groups, or surface contamination. Free energies of hysteresis were calculated from contact angles. For PE, which is composed entirely of nonpolar methylene groups, free energies were equivalent to the strength of dispersive van der Waals bonds. For PAs, free energies corresponded to fractional contributions from the dispersive methylene groups and polar amide groups.

  10. Determination of the Contact Angle Based on the Casimir Effect

    NASA Technical Reports Server (NTRS)

    Mazuruk, K.; Volz, M. P.

    2015-01-01

    In several crystal growth processed based on capillarity, a melt comes into contact with a crucible wall at an angle defined as the contact angle. For molten metals and semiconductors, this contact angle is dependent upon both the crucible and melt material and typical values fall in the range 80-170deg. However, on a microscopic scale, there does not exist a precise and sharp contact angle but rather the melt and solid surfaces merge smoothly and continuously over a distance of up to several micrometers. Accurate modeling requires a more advanced treatment of this interaction. The interaction between the melt and solid surfaces can be calculated by considering two forces: a short-range repulsive force and a longer range (up to a few micrometers) Casimir force. The Casimir force between the two bodies of complex geometry is calculated using a retarded temperature Green's function (Matsubara type) for the photon in the medium. The governing equations are cast in the form of a set of boundary integral equations which are then solved numerically for the case of molten Ge on SiO2. The shape of the molten surface approaching the flat solid body is determined, and the contact angle is defined as the angle between the two surfaces at the microscopically asymptotic distance of 1-2 micrometers. The formulation of this model and the results of the numerical calculations will be presented and discussed.

  11. Dancing droplets: Contact angle, drag, and confinement

    NASA Astrophysics Data System (ADS)

    Benusiglio, Adrien; Cira, Nate; Prakash, Manu

    2015-11-01

    When deposited on a clean glass slide, a mixture of water and propylene glycol forms a droplet of given contact angle, when both pure liquids spread. (Cira, Benusiglio, Prakash: Nature, 2015). The droplet is stabilized by a gradient of surface tension due to evaporation that induces a Marangoni flow from the border to the apex of the droplets. The apparent contact angle of the droplets depends on both their composition and the external humidity as captured by simple models. These droplets present remarkable properties such as lack of a large pinning force. We discuss the drag on these droplets as a function of various parameters. We show theoretical and experimental results of how various confinement geometries change the vapor gradient and the dynamics of droplet attraction.

  12. Tool Indicates Contact Angles In Bearing Raceways

    NASA Technical Reports Server (NTRS)

    Akian, Richard A.; Butner, Myles F.

    1995-01-01

    Tool devised for use in measuring contact angles between balls and races in previously operated ball bearings. Used on both inner and outer raceways of bearings having cross-sectional widths between approximately 0.5 and 2.0 in. Consists of integral protractor mounted in vertical plane on bracket equipped with leveling screws and circular level indicator. Protractor includes rotatable indicator needle and set of disks of various sizes to fit various raceway curvatures.

  13. Effect of contact angle hysteresis on moving liquid film integrity

    NASA Technical Reports Server (NTRS)

    Simon, F. F.; Hsu, Y. Y.

    1972-01-01

    A study was made of the formation and breakdown of a water film moving over solid surfaces (teflon, lucite, stainless steel, and copper). The flow rate associated with film formation was found to be higher than the flow rate at which film breakdown occurred. The difference in the flow rates for film formation and film breakdown was attributed to contact angle hysteresis. Analysis and experiment, which are in good agreement, indicated that film formation and film breakdown are functions of the advancing and receding angles, respectively.

  14. Characterization of treated porcelain surfaces via dynamic contact angle analysis.

    PubMed

    Phoenix, R D; Shen, C

    1995-01-01

    Successful porcelain repair requires conditioning of porcelain surfaces. Conditioning is intended to facilitate wetting by repair materials and improve interfacial bonding. The objective of this investigation was to determine the effects of selected surface treatments upon the wettability of a representative feldspathic porcelain. Dynamic contact angle analysis and scanning electron microscopy were used to characterize the effects of such treatments. Standardized porcelain specimens were subjected to the following five treatment regimens: (1) control (no treatment); (2) airborne particle abrasion using 50 microns aluminum oxide; (3) etching with ammonium bifluoride gel; (4) etching with acidulated phosphate fluoride gel; and (5) etching with hydrofluoric acid gel. Following treatment, specimens were cleansed and dried. Advancing contact angles were quantified using dynamic contact angle analysis. Mean values and 95% confidence intervals were (in degrees): control, 63.8 +/- 2.7; ammonium bifluoride, 39.4 +/- 2.0; airborne particle abrading, 29.1 +/- 2.9; acidulated phosphate fluoride, 24.9 +/- 1.7; and hydrofluoric acid, 16.5 +/- 1.2. Significant differences were found between all treatment groups (P = .05). Subsequent scanning electron microscopy examination of treated surfaces indicated lesser contact angles were associated with surfaces displaying deeper and wider grooves. Apparently, the resultant increase in surface area produces increased wettability. It is inferred that an increase in surface area may correspond to enhanced resin-porcelain bonding.

  15. Understanding contact angle hysteresis on an ambient solid surface.

    PubMed

    Wang, Yong Jian; Guo, Shuo; Chen, Hsuan-Yi; Tong, Penger

    2016-05-01

    We report a systematic study of contact angle hysteresis (CAH) with direct measurement of the capillary force acting on a contact line formed on the surface of a long glass fiber intersecting a liquid-air interface. The glass fiber of diameter 1-2μm and length 100-200μm is glued onto the front end of a rectangular cantilever beam, which is used for atomic force microscopy. From the measured hysteresis loop of the capillary force for 28 different liquids with varying surface tensions and contact angles, we find a universal behavior of the unbalanced capillary force in the advancing and receding directions and the spring constant of a stretched meniscus by the glass fiber. Measurements of the capillary force and its fluctuations suggest that CAH on an ambient solid surface is caused primarily by two types of coexisting and spatially intertwined defects with opposite natures. The contact line is primarily pinned by the relatively nonwetting (repulsive) defects in the advancing direction and by the relatively wetting (attractive) defects in the receding direction. Based on the experimental observations, we propose a "composite model" of CAH and relevant scaling laws, which explain the basic features of the measured hysteresis force loops. PMID:27300959

  16. Understanding contact angle hysteresis on an ambient solid surface.

    PubMed

    Wang, Yong Jian; Guo, Shuo; Chen, Hsuan-Yi; Tong, Penger

    2016-05-01

    We report a systematic study of contact angle hysteresis (CAH) with direct measurement of the capillary force acting on a contact line formed on the surface of a long glass fiber intersecting a liquid-air interface. The glass fiber of diameter 1-2μm and length 100-200μm is glued onto the front end of a rectangular cantilever beam, which is used for atomic force microscopy. From the measured hysteresis loop of the capillary force for 28 different liquids with varying surface tensions and contact angles, we find a universal behavior of the unbalanced capillary force in the advancing and receding directions and the spring constant of a stretched meniscus by the glass fiber. Measurements of the capillary force and its fluctuations suggest that CAH on an ambient solid surface is caused primarily by two types of coexisting and spatially intertwined defects with opposite natures. The contact line is primarily pinned by the relatively nonwetting (repulsive) defects in the advancing direction and by the relatively wetting (attractive) defects in the receding direction. Based on the experimental observations, we propose a "composite model" of CAH and relevant scaling laws, which explain the basic features of the measured hysteresis force loops.

  17. Understanding contact angle hysteresis on an ambient solid surface

    NASA Astrophysics Data System (ADS)

    Wang, Yong Jian; Guo, Shuo; Chen, Hsuan-Yi; Tong, Penger

    2016-05-01

    We report a systematic study of contact angle hysteresis (CAH) with direct measurement of the capillary force acting on a contact line formed on the surface of a long glass fiber intersecting a liquid-air interface. The glass fiber of diameter 1 -2 μ m and length 100 -200 μ m is glued onto the front end of a rectangular cantilever beam, which is used for atomic force microscopy. From the measured hysteresis loop of the capillary force for 28 different liquids with varying surface tensions and contact angles, we find a universal behavior of the unbalanced capillary force in the advancing and receding directions and the spring constant of a stretched meniscus by the glass fiber. Measurements of the capillary force and its fluctuations suggest that CAH on an ambient solid surface is caused primarily by two types of coexisting and spatially intertwined defects with opposite natures. The contact line is primarily pinned by the relatively nonwetting (repulsive) defects in the advancing direction and by the relatively wetting (attractive) defects in the receding direction. Based on the experimental observations, we propose a "composite model" of CAH and relevant scaling laws, which explain the basic features of the measured hysteresis force loops.

  18. Estimation of Intrinsic Contact Angle of Various Liquids on PTFE by Utilizing Ultrasonic Vibration

    NASA Astrophysics Data System (ADS)

    Urai, Takuya; Kamai, Masayoshi; Fujii, Hidetoshi

    2016-08-01

    The contact angle measured using the sessile drop method is typically an advancing contact angle, which is often used for the evaluation of wettability. However, the precise measurement of the contact angle on rough substrates has been required for developing various industrial processes. In this study, a new measuring method by achieving the minimum total free energy by ultrasonic vibration (USV) was developed. The new method has been demonstrated for different rough surfaces, droplet volumes, and wettability conditions. The advancing contact angle significantly decreased when the USV is applied, but it immediately increased after stopping the USV. In order to capture the droplet behavior at the beginning and end of the USV, a high-speed camera was used. The contact angle was apparently a receding contact angle after stopping the ultrasonic vibration. Accordingly, the intrinsic contact angle was estimated using the values of the advancing contact angles obtained before applying the ultrasonic vibration and the receding contact angles obtained after stopping the ultrasonic vibration.

  19. Ultralyophobic oxidized aluminum surfaces exhibiting negligible contact angle hysteresis.

    PubMed

    Hozumi, Atsushi; McCarthy, Thomas J

    2010-02-16

    Ultralyophobic oxidized aluminum surfaces exhibiting negligible contact angle hysteresis for probe liquids were prepared by chemical vapor deposition (CVD) of bis((tridecafluoro-1,1,2,2,-tetrahydrooctyl)-dimethylsiloxy)methylsilane (CF(3)(CF(2))(5)CH(2)CH(2)Si(CH(3))(2)O)(2)SiCH(3)H, (R(F)Si(Me)(2)O)(2)SiMeH). Oxidized aluminum surfaces were prepared by photooxidation/cleaning of sputter-coated aluminum on silicon wafers (Si/Al(Al(2)(O(3)))) using oxygen plasma. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) confirmed that this facile CVD method produces a monolayer with a thickness of 1.1 nm on the Si/Al(Al(2)(O(3))) surface without a discernible change in surface morphology. After monolayer deposition, the hydrophilic Si/Al(Al(2)(O(3))) surface became both hydrophobic and oleophobic and exhibited essentially no contact angle hysteresis for water and n-hexadecane (advancing/receding contact angles (theta(A)/theta(R)) = 110 degrees/109 degrees and 52 degrees/50 degrees, respectively). Droplets move very easily on this surface and roll off of slightly tilted surfaces, independently of the contact angle (which is a practical definition of ultralyophobic). A conventional fluoroalkylsilane monolayer was also prepared from 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (CF(3)(CF(2))(7)CH(2)CH(2)Si(OCH(3))(3), R(F)Si(OMe)(3)) for comparison. The theta(A)/theta(R) values for water and n-hexadecane are 121 degrees/106 degrees and 76 degrees/71 degrees, respectively. The larger hysteresis values indicate the "pinning" of probe liquids, even though advancing contact angles are larger than those of the (R(F)Si(Me)(2)O)(2)SiMeH-derived monolayers. The (R(F)Si(Me)(2)O)(2)SiMeH-derived monolayers have excellent hydrolytic stability in water. We propose that the (R(F)Si(Me)(2)O)(2)SiMeH-derived monolayers are flexible and liquidlike and that drops in contact with these surfaces experience very low energy barriers between metastable states, leading to the

  20. Ultralyophobic oxidized aluminum surfaces exhibiting negligible contact angle hysteresis.

    PubMed

    Hozumi, Atsushi; McCarthy, Thomas J

    2010-02-16

    Ultralyophobic oxidized aluminum surfaces exhibiting negligible contact angle hysteresis for probe liquids were prepared by chemical vapor deposition (CVD) of bis((tridecafluoro-1,1,2,2,-tetrahydrooctyl)-dimethylsiloxy)methylsilane (CF(3)(CF(2))(5)CH(2)CH(2)Si(CH(3))(2)O)(2)SiCH(3)H, (R(F)Si(Me)(2)O)(2)SiMeH). Oxidized aluminum surfaces were prepared by photooxidation/cleaning of sputter-coated aluminum on silicon wafers (Si/Al(Al(2)(O(3)))) using oxygen plasma. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) confirmed that this facile CVD method produces a monolayer with a thickness of 1.1 nm on the Si/Al(Al(2)(O(3))) surface without a discernible change in surface morphology. After monolayer deposition, the hydrophilic Si/Al(Al(2)(O(3))) surface became both hydrophobic and oleophobic and exhibited essentially no contact angle hysteresis for water and n-hexadecane (advancing/receding contact angles (theta(A)/theta(R)) = 110 degrees/109 degrees and 52 degrees/50 degrees, respectively). Droplets move very easily on this surface and roll off of slightly tilted surfaces, independently of the contact angle (which is a practical definition of ultralyophobic). A conventional fluoroalkylsilane monolayer was also prepared from 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (CF(3)(CF(2))(7)CH(2)CH(2)Si(OCH(3))(3), R(F)Si(OMe)(3)) for comparison. The theta(A)/theta(R) values for water and n-hexadecane are 121 degrees/106 degrees and 76 degrees/71 degrees, respectively. The larger hysteresis values indicate the "pinning" of probe liquids, even though advancing contact angles are larger than those of the (R(F)Si(Me)(2)O)(2)SiMeH-derived monolayers. The (R(F)Si(Me)(2)O)(2)SiMeH-derived monolayers have excellent hydrolytic stability in water. We propose that the (R(F)Si(Me)(2)O)(2)SiMeH-derived monolayers are flexible and liquidlike and that drops in contact with these surfaces experience very low energy barriers between metastable states, leading to the

  1. From hygrophilic to superhygrophobic: theoretical conditions for making high-contact-angle surfaces from low-contact-angle materials.

    PubMed

    Marmur, Abraham

    2008-07-15

    The possibility of making high-contact-angle, rough surfaces from low-contact-angle materials has recently been suggested and demonstrated. A thermodynamic analysis of this possibility in terms of feasibility and stability is presented. It turns out that only roughness topographies that conform to a feasibility condition which is developed in the present paper can support this phenomenon. Even under conditions that support the phenomenon, the high-contact-angle state may not be stable, and transition from the heterogeneous (Cassie-Baxter) wetting regime to the homogeneous (Wenzel) regime with a lower contact angle may occur. In addition, it is suggested to use the general terms hygrophilic and hygrophobic (based on the Greek prefix hygro- that means liquid) to describe low- and high-contact-angle surfaces, respectively. PMID:18543997

  2. Measurement of Critical Contact Angle in a Microgravity Space Experiment

    NASA Technical Reports Server (NTRS)

    Concus, P.; Finn, R.; Weislogel, M.

    1998-01-01

    Mathematical theory predicts that small changes in container shape or in contact angle can give rise to large shifts of liquid in a microgravity environment. This phenomenon was investigated in the Interface Configuration Experiment on board the USMT,2 Space Shuttle flight. The experiment's "double proboscis" containers were designed to strike a balance between conflicting requirements of sizable volume of liquid shift (for ease of observation) and abruptness of the shift (for accurate determination of critical contact angle). The experimental results support the classical concept of macroscopic contact angle and demonstrate the role of hysteresis in impeding orientation toward equilibrium.

  3. Measurement of Critical Contact Angle in a Microgravity Space Experiment

    NASA Technical Reports Server (NTRS)

    Concus, P.; Finn, R.; Weislogel, M.

    1998-01-01

    Mathematical theory predicts that small changes in container shape or in contact angle can give rise to large shifts of liquid in a microgravity environment. This phenomenon was investigated in the Interface Configuration Experiment on board the USML-2 Space Shuttle flight. The experiment's "double proboscis" containers were designed to strike a balance between conflicting requirements of sizable volume of liquid shift (for ease of observation) and abruptness of the shift (for accurate determination of critical contact angle). The experimental results support the classical concept of macroscopic contact angle and demonstrate the role of hysteresis in impeding orientation toward equilibrium.

  4. Measurement of critical contact angle in a microgravity space experiment

    NASA Astrophysics Data System (ADS)

    Concus, P.; Finn, R.; Weislogel, M.

    Mathematical theory predicts that small changes in container shape or in contact angle can give rise to large shifts of liquid in a microgravity environment. This phenomenon was investigated in the Interface Configuration Experiment on board the NASA USML-2 Space Shuttle flight. The experiment's ``double proboscis'' containers were designed to strike a balance between conflicting requirements of sizable volume of liquid shift (for ease of observation) and abruptness of the shift (for accurate determination of critical contact angle). The experimental results support the classical concept of macroscopic contact angle and demonstrate the role of hysteresis in impeding orientation toward equilibrium.

  5. Measurement of critical contact angle in a microgravity space experiment

    SciTech Connect

    Concus, P.; Finn, R.; Weislogel, M.

    1999-06-01

    Mathematical theory predicts that small changes in container shape or in contact angle can give rise to large shifts of liquid in a microgravity environment. This phenomenon was investigated in the Interface Configuration Experiment on board the NASA USML-2 Space Shuttle flight. The experiment's double proboscis containers were designed to strike a balance between conflicting requirements of sizable volume of liquid shift (for ease of observation) and abruptness of the shift (for accurate determination of critical contact angle). The experimental results support the classical concept of macroscopic contact angle and demonstrate the role of hysteresis in impeding orientation toward equilibrium.

  6. Static and Dynamic Contact Angles of Immersed Ferrofluid Droplets

    NASA Astrophysics Data System (ADS)

    Chatterjee, Souvick; Bhowmik, Dipanwita; Mukhopadhyay, Achintya; Ganguly, Ranjan

    2013-11-01

    Ferrofluid plug driven micro-pumps are useful for manipulating micro-volume of liquids by providing remote actuation using a localized magnetic field gradient. Inside a microchannel, the ferrofluid experiences combined actions of different relevant body forces. While the pressure, viscous and magnetic forces can be estimated using established techniques, the surface tension force requires information about the contact angle between the ferrofluid and glass capillary wall. We address this phenomenon through experimental characterization of static and dynamic contact angles of oil based ferrofluid (EFH3) droplets on glass surface immersed in pure or surfacted distilled water. The equilibrium static contact angle is found to significantly reduce in presence of a magnetic field. Dynamic contact angles are measured through high-speed imaging as the ferrofluid droplets slide along an inclined glass surface. Variation of contact angle hysteresis, which falls outside the Hoffmann Tanner equation for this case, is also investigated as a function of contact line velocity. A strong dependence is found between the contact angle hysteresis and the wetting time. Findings of the work is useful for designing ferrofluid plug-driven microfluidic plugs for different lab-on-a-chip applications.

  7. Experimental investigation of contact angle, curvature, and contact line motion in dropwise condensation and evaporation.

    PubMed

    Gokhale, Shripad J; Plawsky, Joel L; Wayner, Peter C

    2003-03-15

    Image-analyzing interferometry is used to measure the apparent contact angle and the curvature of a drop and a meniscus during condensation and evaporation processes in a constrained vapor bubble (CVB) cell. The apparent contact angle is found to be a function of the interfacial mass flux. The interfacial velocity for the drop during condensation and evaporation is a function of the apparent contact angle and the rate of change of radius of curvature. The dependence of velocity on the apparent contact angle is consistent with Tanner's scaling equation. The results support the hypothesis that evaporation/condensation is an important factor in contact line motion. The main purpose of this article is to present the experimental technique and the data. The equilibrium contact angle for the drop is found experimentally to be higher than that for the corner meniscus. The contact angle is a function of the stress field in the fluid. The equilibrium contact angle is related to the thickness of the thin adsorbed film in the microscopic region and depends on the characteristics of the microscopic region. The excess interfacial free energy and temperature jump were used to calculate the equilibrium thickness of the thin adsorbed film in the microscopic region.

  8. How pinning and contact angle hysteresis govern quasi-static liquid drop transfer.

    PubMed

    Chen, H; Tang, T; Zhao, H; Law, K-Y; Amirfazli, A

    2016-02-21

    This paper presents both experimental and numerical simulations of liquid transfer between two solid surfaces with contact angle hysteresis (CAH). Systematic studies on the role of the advancing contact angle (θa), receding contact angle (θr) and CAH in determining the transfer ratio (volume of the liquid transferred onto the acceptor surface over the total liquid volume) and the maximum adhesion force (Fmax) were performed. The transfer ratio was found to be governed by contact line pinning at the end of the transfer process caused by CAH of surfaces. A map based on θr of the two surfaces was generated to identify the three regimes for liquid transfer: (I) contact line pinning occurs only on the donor surface, (II) contact line pinning occurs on both surfaces, and (III) contact line pinning occurs only on the acceptor surface. With this map, an empirical equation is provided which is able to estimate the transfer ratio by only knowing θr of the two surfaces. The value of Fmax is found to be strongly influenced by the contact line pinning in the early stretching stage. For symmetric liquid bridges between two identical surfaces, Fmax may be determined only by θa, only by θr, or by both θa and θr, depending on the magnitude of the contact angles. For asymmetric bridges, Fmax is found to be affected by the period when contact lines are pinned on both surfaces. PMID:26777599

  9. How pinning and contact angle hysteresis govern quasi-static liquid drop transfer.

    PubMed

    Chen, H; Tang, T; Zhao, H; Law, K-Y; Amirfazli, A

    2016-02-21

    This paper presents both experimental and numerical simulations of liquid transfer between two solid surfaces with contact angle hysteresis (CAH). Systematic studies on the role of the advancing contact angle (θa), receding contact angle (θr) and CAH in determining the transfer ratio (volume of the liquid transferred onto the acceptor surface over the total liquid volume) and the maximum adhesion force (Fmax) were performed. The transfer ratio was found to be governed by contact line pinning at the end of the transfer process caused by CAH of surfaces. A map based on θr of the two surfaces was generated to identify the three regimes for liquid transfer: (I) contact line pinning occurs only on the donor surface, (II) contact line pinning occurs on both surfaces, and (III) contact line pinning occurs only on the acceptor surface. With this map, an empirical equation is provided which is able to estimate the transfer ratio by only knowing θr of the two surfaces. The value of Fmax is found to be strongly influenced by the contact line pinning in the early stretching stage. For symmetric liquid bridges between two identical surfaces, Fmax may be determined only by θa, only by θr, or by both θa and θr, depending on the magnitude of the contact angles. For asymmetric bridges, Fmax is found to be affected by the period when contact lines are pinned on both surfaces.

  10. Repulsion-based model for contact angle saturation in electrowetting

    PubMed Central

    2015-01-01

    We introduce a new model for contact angle saturation phenomenon in electrowetting on dielectric systems. This new model attributes contact angle saturation to repulsion between trapped charges on the cap and base surfaces of the droplet in the vicinity of the three-phase contact line, which prevents these surfaces from converging during contact angle reduction. This repulsion-based saturation is similar to repulsion between charges accumulated on the surfaces of conducting droplets which causes the well known Coulombic fission and Taylor cone formation phenomena. In our model, both the droplet and dielectric coating were treated as lossy dielectric media (i.e., having finite electrical conductivities and permittivities) contrary to the more common assumption of a perfectly conducting droplet and perfectly insulating dielectric. We used theoretical analysis and numerical simulations to find actual charge distribution on droplet surface, calculate repulsion energy, and minimize energy of the total system as a function of droplet contact angle. Resulting saturation curves were in good agreement with previously reported experimental results. We used this proposed model to predict effect of changing liquid properties, such as electrical conductivity, and system parameters, such as thickness of the dielectric layer, on the saturation angle, which also matched experimental results. PMID:25759748

  11. The Influence of Dynamic Contact Angle on Wetting Dynamics

    NASA Technical Reports Server (NTRS)

    Rame, Enrique; Garoff, Steven

    2005-01-01

    When surface tension forces dominate, and regardless of whether the situation is static or dynamic, the contact angle (the angle the interface between two immiscible fluids makes when it contacts a solid) is the key parameter that determines the shape of a fluid-fluid interface. The static contact angle is easy to measure and implement in models predicting static capillary surface shapes and such associated quantities as pressure drops. By contrast, when the interface moves relative to the solid (as in dynamic wetting processes) the dynamic contact angle is not identified unambiguously because it depends on the geometry of the system Consequently, its determination becomes problematic and measurements in one geometry cannot be applied in another for prediction purposes. However, knowing how to measure and use the dynamic contact angle is crucial to determine such dynamics as a microsystem throughput reliably. In this talk we will present experimental and analytical efforts aimed at resolving modeling issues present in dynamic wetting. We will review experiments that show the inadequacy of the usual hydrodynamic model when a fluid-fluid meniscus moves over a solid surface such as the wall of a small tube or duct. We will then present analytical results that show how to parametrize these problems in a predictive manner. We will illustrate these ideas by showing how to implement the method in numerical fluid mechanical calculations.

  12. Non-contact measurement of rotation angle with solo camera

    NASA Astrophysics Data System (ADS)

    Gan, Xiaochuan; Sun, Anbin; Ye, Xin; Ma, Liqun

    2015-02-01

    For the purpose to measure a rotation angle around the axis of an object, a non-contact rotation angle measurement method based on solo camera was promoted. The intrinsic parameters of camera were calibrated using chessboard on principle of plane calibration theory. The translation matrix and rotation matrix between the object coordinate and the camera coordinate were calculated according to the relationship between the corners' position on object and their coordinates on image. Then the rotation angle between the measured object and the camera could be resolved from the rotation matrix. A precise angle dividing table (PADT) was chosen as the reference to verify the angle measurement error of this method. Test results indicated that the rotation angle measurement error of this method did not exceed +/- 0.01 degree.

  13. Dynamic Contact Angle at the Nanoscale: A Unified View.

    PubMed

    Lukyanov, Alex V; Likhtman, Alexei E

    2016-06-28

    Generation of a dynamic contact angle in the course of wetting is a fundamental phenomenon of nature. Dynamic wetting processes have a direct impact on flows at the nanoscale, and therefore, understanding them is exceptionally important to emerging technologies. Here, we reveal the microscopic mechanism of dynamic contact angle generation. It has been demonstrated using large-scale molecular dynamics simulations of bead-spring model fluids that the main cause of local contact angle variations is the distribution of microscopic force acting at the contact line region. We were able to retrieve this elusive force with high accuracy. It has been directly established that the force distribution can be solely predicted on the basis of a general friction law for liquid flow at solid surfaces by Thompson and Troian. The relationship with the friction law provides both an explanation of the phenomenon of dynamic contact angle and a methodology for future predictions. The mechanism is intrinsically microscopic, universal, and irreducible and is applicable to a wide range of problems associated with wetting phenomena. PMID:27276341

  14. Contact Angle Measurements Using a Simplified Experimental Setup

    ERIC Educational Resources Information Center

    Lamour, Guillaume; Hamraoui, Ahmed; Buvailo, Andrii; Xing, Yangjun; Keuleyan, Sean; Prakash, Vivek; Eftekhari-Bafrooei, Ali; Borguet, Eric

    2010-01-01

    A basic and affordable experimental apparatus is described that measures the static contact angle of a liquid drop in contact with a solid. The image of the drop is made with a simple digital camera by taking a picture that is magnified by an optical lens. The profile of the drop is then processed with ImageJ free software. The ImageJ contact…

  15. Effect of surface texturing on superoleophobicity, contact angle hysteresis, and "robustness".

    PubMed

    Zhao, Hong; Park, Kyoo-Chul; Law, Kock-Yee

    2012-10-23

    Previously, we reported the creation of a fluorosilane (FOTS) modified pillar array silicon surface comprising ~3-μm-diameter pillars (6 μm pitch with ~7 μm height) that is both superhydrophobic and superoleophobic, with water and hexadecane contact angles exceeding 150° and sliding angles at ~10° owing to the surface fluorination and the re-entrant structure in the side wall of the pillar. In this work, the effects of surface texturing (pillar size, spacing, and height) on wettability, contact angle hysteresis, and "robustness" are investigated. We study the static, advancing, and receding contact angles, as well as the sliding angles as a function of the solid area fraction. The results reveal that pillar size and pillar spacing have very little effect on the static and advancing contact angles, as they are found to be insensitive to the solid area fraction from 0.04 to ~0.4 as the pillar diameter varies from 1 to 5 μm and the center-to-center spacing varies from 4.5 to 12 μm. On the other hand, sliding angle, receding contact angle, and contact angle hysteresis are found to be dependent on the solid area fraction. Specifically, receding contact angle decreases and sliding angle and hysteresis increase as the solid area fraction increases. This effect can be attributable to the increase in pinning as the solid area fraction increases. Surface Evolver modeling shows that water wets and pins the pillar surface whereas hexadecane wets the pillar surface and then penetrates into the side wall of the pillar with the contact line pinning underneath the re-entrant structure. Due to the penetration of the hexadecane drop into the pillar structure, the effect on the receding contact angle and hysteresis is larger relative to that of water. This interpretation is supported by studying a series of FOTS pillar array surfaces with varying overhang thickness. With the water drop, the contact line is pinned on the pillar surface and very little overhang thickness effect

  16. Effect of surface texturing on superoleophobicity, contact angle hysteresis, and "robustness".

    PubMed

    Zhao, Hong; Park, Kyoo-Chul; Law, Kock-Yee

    2012-10-23

    Previously, we reported the creation of a fluorosilane (FOTS) modified pillar array silicon surface comprising ~3-μm-diameter pillars (6 μm pitch with ~7 μm height) that is both superhydrophobic and superoleophobic, with water and hexadecane contact angles exceeding 150° and sliding angles at ~10° owing to the surface fluorination and the re-entrant structure in the side wall of the pillar. In this work, the effects of surface texturing (pillar size, spacing, and height) on wettability, contact angle hysteresis, and "robustness" are investigated. We study the static, advancing, and receding contact angles, as well as the sliding angles as a function of the solid area fraction. The results reveal that pillar size and pillar spacing have very little effect on the static and advancing contact angles, as they are found to be insensitive to the solid area fraction from 0.04 to ~0.4 as the pillar diameter varies from 1 to 5 μm and the center-to-center spacing varies from 4.5 to 12 μm. On the other hand, sliding angle, receding contact angle, and contact angle hysteresis are found to be dependent on the solid area fraction. Specifically, receding contact angle decreases and sliding angle and hysteresis increase as the solid area fraction increases. This effect can be attributable to the increase in pinning as the solid area fraction increases. Surface Evolver modeling shows that water wets and pins the pillar surface whereas hexadecane wets the pillar surface and then penetrates into the side wall of the pillar with the contact line pinning underneath the re-entrant structure. Due to the penetration of the hexadecane drop into the pillar structure, the effect on the receding contact angle and hysteresis is larger relative to that of water. This interpretation is supported by studying a series of FOTS pillar array surfaces with varying overhang thickness. With the water drop, the contact line is pinned on the pillar surface and very little overhang thickness effect

  17. A Numerical Dynamic Contact Angle Model Applied to Droplets Sliding Down An Incline

    NASA Astrophysics Data System (ADS)

    Afkhami, Shahriar; Bussmann, Markus

    2007-11-01

    A numerical dynamic contact angle model based on a well-known hydrodynamic theory is developed for the imposition of a boundary condition at the contact line. The efficacy of this new model is demonstrated via 3D examples of a viscous droplet sliding down a partially wetting incline. As experimentally observed (Phys. Rev. Lett. 87 (2001), 036102), when the inclination angle increases, the rear of the drop becomes elongated until it develops a ``corner'' which eventually breaks up into smaller droplets, while the leading edge of the drop remains rounded. Using the open source code ``Gerris'' (http://gfs.sf.net), we present the results of droplets sliding on an inclined plane. A similar behaviour (asymmetry between advancing and receding contact lines) is demonstrated. Results are in qualitative agreement with experimental observations. The role of surface inclination on the distribution of the dynamic contact angle along the droplet perimeter is also presented.

  18. Contact-angle hysteresis on periodic microtextured surfaces: Strongly corrugated liquid interfaces

    NASA Astrophysics Data System (ADS)

    Iliev, Stanimir; Pesheva, Nina

    2016-06-01

    We study numerically the shapes of a liquid meniscus in contact with ultrahydrophobic pillar surfaces in Cassie's wetting regime, when the surface is covered with identical and periodically distributed micropillars. Using the full capillary model we obtain the advancing and the receding equilibrium meniscus shapes when the cross-sections of the pillars are both of square and circular shapes, for a broad interval of pillar concentrations. The bending of the liquid interface in the area between the pillars is studied in the framework of the full capillary model and compared to the results of the heterogeneous approximation model. The contact angle hysteresis is obtained when the three-phase contact line is located on one row (block case) or several rows (kink case) of pillars. It is found that the contact angle hysteresis is proportional to the line fraction of the contact line on pillars tops in the block case and to the surface fraction for pillar concentrations 0.1 -0.5 in the kink case. The contact angle hysteresis does not depend on the shape (circular or square) of the pillars cross-section. The expression for the proportionality of the receding contact angle to the line fraction [Raj et al., Langmuir 28, 15777 (2012), 10.1021/la303070s] in the case of block depinning is theoretically substantiated through the capillary force, acting on the solid plate at the meniscus contact line.

  19. Contact-angle hysteresis on periodic microtextured surfaces: Strongly corrugated liquid interfaces.

    PubMed

    Iliev, Stanimir; Pesheva, Nina

    2016-06-01

    We study numerically the shapes of a liquid meniscus in contact with ultrahydrophobic pillar surfaces in Cassie's wetting regime, when the surface is covered with identical and periodically distributed micropillars. Using the full capillary model we obtain the advancing and the receding equilibrium meniscus shapes when the cross-sections of the pillars are both of square and circular shapes, for a broad interval of pillar concentrations. The bending of the liquid interface in the area between the pillars is studied in the framework of the full capillary model and compared to the results of the heterogeneous approximation model. The contact angle hysteresis is obtained when the three-phase contact line is located on one row (block case) or several rows (kink case) of pillars. It is found that the contact angle hysteresis is proportional to the line fraction of the contact line on pillars tops in the block case and to the surface fraction for pillar concentrations 0.1-0.5 in the kink case. The contact angle hysteresis does not depend on the shape (circular or square) of the pillars cross-section. The expression for the proportionality of the receding contact angle to the line fraction [Raj et al., Langmuir 28, 15777 (2012)LANGD50743-746310.1021/la303070s] in the case of block depinning is theoretically substantiated through the capillary force, acting on the solid plate at the meniscus contact line.

  20. Slip-stick wetting and large contact angle hysteresis on wrinkled surfaces.

    PubMed

    Bukowsky, Colton; Torres, Jessica M; Vogt, Bryan D

    2011-02-15

    Wetting on a corrugated surface that is formed via wrinkling of a hard skin layer formed by UV oxidation (UVO) of a poly(dimethylsiloxane) (PDMS) slab is studied using advancing and receding water contact angle measurements. The amplitude of the wrinkled pattern can be tuned through the pre-strain of the PDMS prior to surface oxidation. These valleys and peaks in the surface topography lead to anisotropic wetting by water droplets. As the droplet advances, the fluid is free to move along the direction parallel to the wrinkles, but the droplet moving orthogonal to the wrinkles encounters energy barriers due to the topography and slip-stick behavior is observed. As the wrinkle amplitude increases, anisotropy in the sessile droplet increases between parallel and perpendicular directions. For the drops receding perpendicular to the wrinkles formed at high strains, the contact angle tends to decrease steadily towards zero as the drop volume decreases, which can result in apparent hysteresis in the contact angle of over 100°. The wrinkled surfaces can exhibit high sessile and advancing contact angles (>115°), but the receding angle in these cases is generally vanishing as the drop is removed. This effect results in micrometer sized drops remaining in the grooves for these highly wrinkled surfaces, while the flat analogous UVO-treated PDMS shows complete removal of all macroscopic water drops under similar conditions. These wetting characteristics should be considered if these wrinkled surfaces are to be utilized in or as microfluidic devices.

  1. A "Conveyor Belt" Model for the Dynamic Contact Angle

    ERIC Educational Resources Information Center

    Della Volpe, C.; Siboni, S.

    2011-01-01

    The familiar Young contact angle measurement of a liquid at equilibrium on a solid is a fundamental aspect of capillary phenomena. But in the real world it is not so easy to observe it. This is due to the roughness and/or heterogeneity of real surfaces, which typically are not perfectly planar and chemically homogeneous. What can be easily…

  2. Drop shape visualization and contact angle measurement on curved surfaces.

    PubMed

    Guilizzoni, Manfredo

    2011-12-01

    The shape and contact angles of drops on curved surfaces is experimentally investigated. Image processing, spline fitting and numerical integration are used to extract the drop contour in a number of cross-sections. The three-dimensional surfaces which describe the surface-air and drop-air interfaces can be visualized and a simple procedure to determine the equilibrium contact angle starting from measurements on curved surfaces is proposed. Contact angles on flat surfaces serve as a reference term and a procedure to measure them is proposed. Such procedure is not as accurate as the axisymmetric drop shape analysis algorithms, but it has the advantage of requiring only a side view of the drop-surface couple and no further information. It can therefore be used also for fluids with unknown surface tension and there is no need to measure the drop volume. Examples of application of the proposed techniques for distilled water drops on gemstones confirm that they can be useful for drop shape analysis and contact angle measurement on three-dimensional sculptured surfaces.

  3. Effects of temperature and conditioning on contact lens wetting angles.

    PubMed

    Knick, P D; Huff, J W

    1991-07-01

    Because wettability is not always examined under standard conditions, we investigated the temperature dependence of saline wettability on unconditioned and conditioned polymethylmethacrylate (PMMA), cellulose acetate butyrate (CAB), and three silicone acrylate lens materials. Sessile drop contact angles were measured in a humidity chamber at 23 degrees C and 34 degrees C using laser-assisted contact angle goniometry. In separate experiments, saline-stored and preconditioned lenses were examined either with or without rinsing. Sessile drop contact angles at 34 degrees C were within 2 degrees to 5 degrees of the room temperature values for both conditioned and unconditioned lenses, demonstrating a negligible temperature dependence. At both temperatures, the conditioned PMMA, CAB, silafocon A, and pasifocon C lenses wet slightly better, by 1 degree to 12 degrees, than unconditioned lenses. However, this increase was only significant with PMMA and silafocon A (P less than 0.05) and reversed when the preconditioned lenses were rinsed repeatedly in saline and reexamined. The results suggest that for these materials: 1) in vitro saline contact angles do not approach those seen on the eye, and this discrepancy can not be explained by temperature or conditioning; and 2) conditioning does not increase material wettability but merely forms a temporary hydrophilic interface that is more wettable than the lens material. PMID:1654228

  4. Drop shape visualization and contact angle measurement on curved surfaces.

    PubMed

    Guilizzoni, Manfredo

    2011-12-01

    The shape and contact angles of drops on curved surfaces is experimentally investigated. Image processing, spline fitting and numerical integration are used to extract the drop contour in a number of cross-sections. The three-dimensional surfaces which describe the surface-air and drop-air interfaces can be visualized and a simple procedure to determine the equilibrium contact angle starting from measurements on curved surfaces is proposed. Contact angles on flat surfaces serve as a reference term and a procedure to measure them is proposed. Such procedure is not as accurate as the axisymmetric drop shape analysis algorithms, but it has the advantage of requiring only a side view of the drop-surface couple and no further information. It can therefore be used also for fluids with unknown surface tension and there is no need to measure the drop volume. Examples of application of the proposed techniques for distilled water drops on gemstones confirm that they can be useful for drop shape analysis and contact angle measurement on three-dimensional sculptured surfaces. PMID:21889152

  5. Contact Angles and Surface Tension of Germanium-Silicon Melts

    NASA Technical Reports Server (NTRS)

    Croell, A.; Kaiser, N.; Cobb, S.; Szofran, F. R.; Volz, M.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    Precise knowledge of material parameters is more and more important for improving crystal growth processes. Two important parameters are the contact (wetting) angle and the surface tension, determining meniscus shapes and surface-tension driven flows in a variety of methods (Czochralski, EFG, floating-zone, detached Bridgman growth). The sessile drop technique allows the measurement of both parameters simultaneously and has been used to measure the contact angles and the surface tension of Ge(1-x)Si(x) (0 less than or equal to x less than or equal to 1.3) alloys on various substrate materials. Fused quartz, Sapphire, glassy carbon, graphite, SiC, carbon-based aerogel, pyrolytic boron nitride (pBN), AIN, Si3N4, and polycrystalline CVD diamond were used as substrate materials. In addition, the effect of different cleaning procedures and surface treatments on the wetting behavior were investigated. Measurements were performed both under dynamic vacuum and gas atmospheres (argon or forming gas), with temperatures up to 1100 C. In some experiments, the sample was processed for longer times, up to a week, to investigate any changes of the contact angle and/or surface tension due to slow reactions with the substrate. For pure Ge, stable contact angles were found for carbon-based substrates and for pBN, for Ge(1-x)Si(x) only for pBN. The highest wetting angles were found for pBN substrates with angles around 170deg. For the surface tension of Ge, the most reliable values resulted in gamma(T) = (591- 0.077 (T-T(sub m)) 10(exp -3)N/m. The temperature dependence of the surface tension showed similar values for Ge(1-x)Si(x), around -0.08 x 10(exp -3)N/m K, and a compositional dependence of 2.2 x 10(exp -3)N/m at%Si.

  6. Protein adsorption on surfaces: dynamic contact-angle (DCA) and quartz-crystal microbalance (QCM) measurements.

    PubMed

    Stadler, H; Mondon, M; Ziegler, C

    2003-01-01

    Adsorption of the protein bovine serum albumin (BSA) on gold has been tested at various concentrations in aqueous solution by dynamic contact-angle analysis (DCA) and quartz-crystal microbalance (QCM) measurements. With the Wilhelmy plate technique advancing and receding contact angles and the corresponding hysteresis were measured and correlated with the hydrophilicity and the homogeneity of the surface. With electrical admittance measurements of a gold-coated piezoelectrical quartz crystal, layer mass and viscoelastic contributions to the resonator's frequency shift during adsorption could be separated. A correlation was found between the adsorbed mass and the homogeneity and hydrophilicity of the adsorbed film.

  7. What is the contact angle of water on graphene?

    PubMed

    Taherian, Fereshte; Marcon, Valentina; van der Vegt, Nico F A; Leroy, Frédéric

    2013-02-01

    Although experimental and theoretical studies have addressed the question of the wetting properties of graphene, the actual value of the contact angle of water on an isolated graphene monolayer remains unknown. While recent experimental literature indicates that the contact angle of water on graphite is in the range 90-95°, it has been suggested that the contact angle on graphene may either be as high as 127° or moderately enhanced in comparison with graphite. With the support of classical molecular dynamics simulations using empirical force-fields, we develop an argumentation to show that the value of 127° is an unrealistic estimate and that a value of the order of 95-100° should be expected. Our study establishes a connection between the variation of the work of adhesion of water on graphene-based surfaces and the interaction potential between individual water molecules and these surfaces. We show that a variation of the contact angle from 90° on graphite to 127° on graphene would imply that both of the first two carbon layers of graphite contribute approximately the same interaction energy with water. Such a situation is incompatible with the short-range nature of the interaction between water and this substrate. We also show that the interaction potential energy between water and the graphene-based substrates is the main contribution to the work of adhesion of water with a relative magnitude that is independent of the number of graphene layers. We introduce the idea that the remaining contribution is entropic in nature and is connected to the fluctuations in the water-substrate interaction energy.

  8. Relaxation of contact-line singularities solely by the Kelvin effect and apparent contact angles for isothermal volatile liquids in contact with air

    NASA Astrophysics Data System (ADS)

    Rednikov, Alexey; Colinet, Pierre

    2013-11-01

    The contact (triple) line of a volatile liquid on a flat solid is studied theoretically. Like with a pure-vapor atmosphere [Phys. Rev. E 87, 010401, 2013], but here for isothermal diffusion-limited evaporation/condensation in the presence of an inert gas, we rigorously show that the notorious contact-line singularities (related to motion or phase change itself) can be regularized solely on account of the Kelvin effect (curvature dependence of the saturation conditions). No disjoining pressure, precursor films or Navier slip are in fact needed to this purpose, and nor are they taken into consideration here (``minimalist'' approach). The model applies to both perfect (zero Young's angle) and partial wetting, and is in particular used to study the related issue of evaporation-induced contact angles. Their modification by the contact-line motion (either advancing or receding) is assessed. The formulation is posed for a distinguished immediate vicinity of the contact line (the ``microregion''), the corresponding problem decoupling to leading order, here up to one unknown coefficient, from what actually happens at the macroscale. The lubrication approximation (implying sufficiently small contact angles) is used in the liquid, coupled with the diffusion equation in the gaz phase. Supported by ESA and BELSPO PRODEX and F.R.S.-FNRS.

  9. Numerical Simulation of Dynamic Contact Angles and Contact Lines in Multiphase Flows using Level Set Method

    NASA Astrophysics Data System (ADS)

    Pendota, Premchand

    Many physical phenomena and industrial applications involve multiphase fluid flows and hence it is of high importance to be able to simulate various aspects of these flows accurately. The Dynamic Contact Angles (DCA) and the contact lines at the wall boundaries are a couple of such important aspects. In the past few decades, many mathematical models were developed for predicting the contact angles of the inter-face with the wall boundary under various flow conditions. These models are used to incorporate the physics of DCA and contact line motion in numerical simulations using various interface capturing/tracking techniques. In the current thesis, a simple approach to incorporate the static and dynamic contact angle boundary conditions using the level set method is developed and implemented in multiphase CFD codes, LIT (Level set Interface Tracking) (Herrmann (2008)) and NGA (flow solver) (Desjardins et al (2008)). Various DCA models and associated boundary conditions are reviewed. In addition, numerical aspects such as the occurrence of a stress singularity at the contact lines and grid convergence of macroscopic interface shape are dealt with in the context of the level set approach.

  10. Determination of contact angles on microporous particles using the thin-layer wicking technique.

    PubMed

    Cui, Zheng-Gang; Binks, Bernard P; Clint, John H

    2005-08-30

    The properties of particle-stabilized emulsions, especially with regard to phase inversion, are very dependent on the contact angle that the particles experience at the oil-water interface. For the very small particles used for such emulsions (often a few tens of nm), it is impossible to measure this contact angle directly. Its value could be calculated if it were possible to determine the components of the solid surface free energy. To establish a method suitable for such particles, we have investigated the imbibition of five probe liquids into a porous bed of silica (commercial TLC plates) using the thin-layer wicking technique. For all liquids, the difference between wicking rate for bare plates and for those pre-contacted with the vapors is large but it is not due to an advancing angle effect on bare plates. Our analysis shows that it is due to the diversion of flowing liquid into blind pores which are already filled in the pre-contacted case. Thus a new model is proposed describing wicking in a porous medium with very small blind pores by introducing a parameter into the Washburn equation that corrects for this capillary condensation effect. The parameter needed is determined independently using gravimetric adsorption measurements. When this modified Washburn equation is used, the difference between advancing and receding contact angle is actually quite small. When the averages are used as the Young's contact angles, values for the surface energy components of silica are obtained that are completely consistent between the five liquids and have magnitudes expected for this type of silica surface.

  11. Surface tension and contact angles: Molecular origins and associated microstructure

    NASA Technical Reports Server (NTRS)

    Davis, H. T.

    1982-01-01

    Gradient theory converts the molecular theory of inhomogeneous fluid into nonlinear boundary value problems for density and stress distributions in fluid interfaces, contact line regions, nuclei and microdroplets, and other fluid microstructures. The relationship between the basic patterns of fluid phase behavior and the occurrence and stability of fluid microstructures was clearly established by the theory. All the inputs of the theory have molecular expressions which are computable from simple models. On another level, the theory becomes a phenomenological framework in which the equation of state of homogeneous fluid and sets of influence parameters of inhomogeneous fluids are the inputs and the structures, stress tensions and contact angles of menisci are the outputs. These outputs, which find applications in the science and technology of drops and bubbles, are discussed.

  12. Design of a Condensation-Based Contact Angle Goniometer

    NASA Astrophysics Data System (ADS)

    Roopesh, Ajay; Damle, Viraj; Rykaczewski, Konrad

    2014-11-01

    Condensation of low surface tension fluids such as refrigerants, natural gas, and carbon dioxide is important to a variety of industrial processes. Condensation of these fluids often occurs at elevated pressures and/or cryogenic temperatures, making measurement of their wetting properties using standard approaches challenging. It was recently demonstrated that these properties are critical in designing omniphobic surfaces for low surface tension fluid condensation rate enhancement. To this end, we have developed an alternative goniometer design capable of contact angle measurement at wide pressure and temperature range. In this design, droplets are not dispensed through a pipette but generated through localized condensation on a tip of a preferentially cooled small metal wire encapsulated within a thick thermal insulator layer. Here we present a computational and an experimental study of the relation between the condensation-based goniometer geometry, subcooling, and droplet generation rate. We also compare water contact angle measurements using standard and condensation-based goniometer. KR acknowledges startup funding from ASU.

  13. Hydrophilic property by contact angle change of ion implanted polycarbonate

    SciTech Connect

    Lee, Chan Young; Kil, Jae Keun

    2008-02-15

    In this study, ion implantation was performed onto a polymer, polycarbonate (PC), in order to investigate surface hydrophilic property through contact angle measurement. PC was irradiated with N, Ar, and Xe ions at the irradiation energy of 20-50 keV and the dose range of 5x10{sup 15}, 1x10{sup 16}, 7x10{sup 16} ions/cm{sup 2}. The contact angle of water was estimated by means of the sessile drop method and was reduced with increasing fluence and ion mass but increased with increasing implanted energy. The changes of chemical and structural properties are discussed in view of Furier transform infrared and x-ray photoelectron spectroscopy, which shows increasing C-O bonding and C-C bonding. The surface roughness examined by atomic force microscopy measurement changed smoothly from 3.59 to 2.22 A as the fluence increased. It is concluded that the change in wettability may be caused by surface carbonization and oxidation as well as surface roughness.

  14. Evaporation-induced flow near a contact line: Consequences on coating and contact angle

    NASA Astrophysics Data System (ADS)

    Berteloot, G.; Pham, C.-T.; Daerr, A.; Lequeux, F.; Limat, L.

    2008-07-01

    We propose a simple model of the dynamics of a contact line under evaporation and partial wetting conditions, taking into account the divergent nature of evaporation near the contact line, as evidenced by Deegan et al. (Nature, 389 (1997) 827). We show that evaporation can induce a non-negligible change of the contact angle together with modification of the flow near the contact line. We apply our results to dip-coating of a substrate with non volatile solutes. We show that at small velocities the coating thickness increases and scales like the inverse of the square of the velocity which implies a minimum of the coating thickness at the cross-over with the more familiar Landau-Levich regime.

  15. The effect of contact angle hysteresis on droplet motion and collisions on superhydrophobic surfaces

    NASA Astrophysics Data System (ADS)

    Nilsson, Michael; Rothstein, Jonathan

    2010-11-01

    The effect of varying the contact angle hysteresis of a superhydrophobic surface on the characteristics and dynamics of water droplet motion and their subsequent collision are investigated using a high-speed camera. The surfaces are created by imparting random roughness to Teflon through sanding. With this technique, it is possible to create surfaces with similar advancing contact angles near 150 degrees, but with varying contact angle hysteresis. This talk will focus on a number of interesting experimental observations pertaining to drop dynamics along a surface with uniform hysteresis, drop motion along surfaces with transition zones from one hysteresis to another, and the collision of droplets on surfaces of uniform hysteresis. For single drop studies, gravity is used as the driving force, while the collision studies use pressurized air to propel one drop into the other. For the case of droplet collision, the effect of hysteresis, Weber number, and impact number on the maximum deformation of the drops, and the post-collision dynamics will be discussed. For the single droplet measurements, the resistance to motion will be characterized as well as the transition from rolling to sliding as a function of drop size, inclination angle, and hysteresis. Additionally, we will quantify the effect of surface transitions on the resulting motion, mixing, and deflection of the drops.

  16. Effect of contact angle on the orientation, stability, and assembly of dense floating cubes.

    PubMed

    Daniello, Robert; Khan, Kashan; Donnell, Michael; Rothstein, Jonathan P

    2014-02-01

    In this paper, the effect of contact angle, density, and size on the orientation, stability, and assembly of floating cubes was investigated. All the cubes tested were more dense than water. Floatation occurred as a result of capillary stresses induced by deformation of the air-water interface. The advancing contact angle of the bare acrylic cubes was measured to be 85°. The contact angle of the cubes was increased by painting the cubes with a commercially available superhydrophobic paint to reach an advancing contact angle of 150°. Depending on their size, density, and contact angle, the cubes were observed to float in one of three primary orientations: edge up, vertex up, and face up. An experimental apparatus was built such that the sum of the gravitational force, buoyancy force, and capillary forces could be measured using a force transducer as a function of cube position as it was lowered through the air-water interface. Measurements showed that the maximum capillary forces were always experienced for the face up orientation. However, when floatation was possible in the vertex up orientation, it was found to be the most stable cube orientation because it had the lowest center of gravity. A series of theoretical predictions were performed for the cubes floating in each of the three primary orientations to calculate the net force on the cube. The theoretical predictions were found to match the experimental measurements well. A cube stability diagram of cube orientation as a function of cube contact angle and size was prepared from the predictions of theory and found to match the experimental observations quite well. The assembly of cubes floating face up and vertex up were also studied for assemblies of two, three, and many cubes. Cubes floating face up were found to assemble face-to-face and form regular square lattice patterns with no free interface between cubes. Cubes floating vertex up were found to assemble in a variety of different arrangements

  17. Ultrasonic estimation of the contact angle of a sessile droplet

    SciTech Connect

    Quintero, R.; Simonetti, F.

    2014-02-18

    Radiation of energy by large amplitude leaky Rayleigh waves is regarded as one of the key physical mechanisms regulating the actuation and manipulation of droplets in surface acoustic wave (SAW) microfluidic devices. The interaction between a SAW and a droplet is highly complex and is presently the subject of extensive research. This paper investigates the existence of an additional interaction mechanism based on the propagation of quasi-Stoneley waves inside sessile droplets deposited on a solid substrate. In contrast with the leaky Rayleigh wave, the energy of the Stoneley wave is confined within a thin fluid layer in contact with the substrate. The hypothesis is confirmed by three-dimensional finite element simulations and ultrasonic scattering experiments measuring the reflection of Rayleigh waves from droplets of different diameters. Moreover, real-time monitoring of the droplet evaporation process reveals a clear correlation between the droplet contact angle and the spectral information of the reflected Rayleigh signal, thus paving the way for ultrasonic measurements of surface tension.

  18. Spreading of liquid droplets on cylindrical surfaces: Accurate determination of contact angle

    NASA Astrophysics Data System (ADS)

    Wagner, H. D.

    1990-02-01

    The characterization of the physicochemical nature of interfaces is a key problem in the field of advanced fibrous composites. The macroscopic regime contact angle, which reflects the energetics of wetting at the solid-liquid interface, is difficult to measure by usual methods in the case of very thin cylindrical fibers, but it may be calculated from the shape of a liquid droplet spread onto a cylindrical monofilament using a method developed by Yamaki and Katayama [J. Appl. Polym. Sci. 19, 2897 (1975)], and B. J. Carroll [J. Coll. Interf. Sci. 57, 488 (1976)]. Unfortunately, measurements of the contact angle based on this method are, so far, unable to provide an accuracy of better than about 5°. In the present article two simple extensions of the method of Yamaki and Katayama and Carroll, are presented, from which highly accurate values of the contact angle may be obtained. This is demonstrated experimentally from the spreading of glycerol droplets on carbon fibers and epoxy droplets on aramid fibers.

  19. Contact angle at the leading edge controls cell protrusion rate.

    PubMed

    Gabella, Chiara; Bertseva, Elena; Bottier, Céline; Piacentini, Niccolò; Bornert, Alicia; Jeney, Sylvia; Forró, László; Sbalzarini, Ivo F; Meister, Jean-Jacques; Verkhovsky, Alexander B

    2014-05-19

    Plasma membrane tension and the pressure generated by actin polymerization are two antagonistic forces believed to define the protrusion rate at the leading edge of migrating cells [1-5]. Quantitatively, resistance to actin protrusion is a product of membrane tension and mean local curvature (Laplace's law); thus, it depends on the local geometry of the membrane interface. However, the role of the geometry of the leading edge in protrusion control has not been yet investigated. Here, we manipulate both the cell shape and substrate topography in the model system of persistently migrating fish epidermal keratocytes. We find that the protrusion rate does not correlate with membrane tension, but, instead, strongly correlates with cell roundness, and that the leading edge of the cell exhibits pinning on substrate ridges-a phenomenon characteristic of spreading of liquid drops. These results indicate that the leading edge could be considered a triple interface between the substrate, membrane, and extracellular medium and that the contact angle between the membrane and the substrate determines the load on actin polymerization and, therefore, the protrusion rate. Our findings thus illuminate a novel relationship between the 3D shape of the cell and its dynamics, which may have implications for cell migration in 3D environments.

  20. Finite size effects on textured surfaces: recovering contact angles from vagarious drop edges.

    PubMed

    Gauthier, Anaïs; Rivetti, Marco; Teisseire, Jérémie; Barthel, Etienne

    2014-02-18

    A clue to understand wetting hysteresis on superhydrophobic surfaces is the relation between receding contact angle and surface textures. When the surface textures are large, there is a significant distribution of local contact angles around the drop. As seen from the cross section, the apparent contact angle oscillates as the triple line recedes. Our experiments demonstrate that the origin of these oscillations is a finite size effect. Combining side and bottom views of the drop, we take into account the 3D conformation of the surface near the edge to evaluate an intrinsic contact angle from the oscillations of the apparent contact angle. We find that for drops receding on axisymmetric textures the intrinsic receding contact angle is the minimum value of the oscillation while for a square lattice it is the maximum.

  1. [Determination of contact angle of pharmaceutical excipients and regulating effect of surfactants on their wettability].

    PubMed

    Hua, Dong-dong; Li, He-ran; Yang, Bai-xue; Song, Li-na; Liu, Tiao-tiao; Cong, Yu-tang; Li, San-ming

    2015-10-01

    To study the effects of surfactants on wettability of excipients, the contact angles of six types of surfactants on the surface of two common excipients and mixture of three surfactants with excipients were measured using hypsometry method. The results demonstrated that contact angle of water on the surface of excipients was associated with hydrophilcity of excipients. Contact angle was lowered with increase in hydrophilic groups of excipient molecules. The sequence of contact angle from small to large was starch < sodium benzoate < polyvinylpyrrolidone < sodium carboxymethylcellulose < sodium alginate < chitosan < hydroxypropyl methyl cellulose contact angle of excipients, and their abilities to lower contact angle varied. The results of the present study offer a guideline in the formulation design of tablets.

  2. Influence of electrolytes on contact angles of droplets under electric field.

    PubMed

    Lee, Chiun-Peng; Fang, Bo-Yuan; Wei, Zung-Hang

    2013-04-21

    The change of contact angle is one of the major subjects in the studies of electrowetting on dielectrics. A larger change in contact angle with a less applied electric potential has been pursued by the researchers on digital microfluidics. From previous research it is concluded that the effect of free charges in electrolytes on contact angles can almost be neglected. In this article, obvious influences of free charges on contact angles are presented and discussed. To verify the influence of free charges, both weak electrolyte (boric acid) and strong electrolyte (sodium chloride) are used as sources of free charges in our experiment. It was found that the increase of ion concentration enhances the contact angle variation due to the attraction between the bound surface charges in the dielectric layer and the free counter-ions in the solution. The saturated contact angle occurs with a lower electric potential compared with de-ionized water due to the shielding of the electric field by the free counter-ions. When a strong electrolyte is used, the contact angle varies at a much higher rate than with de-ionized water, and the huge amount of accumulated free ions shields the driving field, causing the contact angle to saturate at a much lower electric potential. The saturated contact angle in strong electrolyte solution is markedly larger than those in weak electrolyte solutions and de-ionized water.

  3. Contact angle saturation in electrowetting: Injection of ions into the surrounding media

    NASA Astrophysics Data System (ADS)

    Yamamoto, Tetsuya; Doi, Masao; Andelman, David

    2015-12-01

    We use the Poisson-Boltzmann theory to predict contact angle saturation of aqueous droplets in electrowetting. Our theory predicts that injection of ions from the droplet into its surrounding medium is responsible for the deviation of the apparent contact angle from the Young-Lippmann equation for large applied voltages. The ion injection substantially decreases the Maxwell stress and increases the osmotic pressure at the interface between the two media, leading to saturation of the apparent contact angle. Moreover, we find that the contact angle does not saturate, but only has a broad minimum that increases again upon further increase of the applied voltage, in agreement with experiments.

  4. Lattice Boltzmann modeling of contact angle and its hysteresis in two-phase flow with large viscosity difference

    NASA Astrophysics Data System (ADS)

    Liu, Haihu; Ju, Yaping; Wang, Ningning; Xi, Guang; Zhang, Yonghao

    2015-09-01

    Contact angle hysteresis is an important physical phenomenon omnipresent in nature and various industrial processes, but its effects are not considered in many existing multiphase flow simulations due to modeling complexity. In this work, a multiphase lattice Boltzmann method (LBM) is developed to simulate the contact-line dynamics with consideration of the contact angle hysteresis for a broad range of kinematic viscosity ratios. In this method, the immiscible two-phase flow is described by a color-fluid model, in which the multiple-relaxation-time collision operator is adopted to increase numerical stability and suppress unphysical spurious currents at the contact line. The contact angle hysteresis is introduced using the strategy proposed by Ding and Spelt [Ding and Spelt, J. Fluid Mech. 599, 341 (2008), 10.1017/S0022112008000190], and the geometrical wetting boundary condition is enforced to obtain the desired contact angle. This method is first validated by simulations of static contact angle and dynamic capillary intrusion process on ideal (smooth) surfaces. It is then used to simulate the dynamic behavior of a droplet on a nonideal (inhomogeneous) surface subject to a simple shear flow. When the droplet remains pinned on the surface due to hysteresis, the steady interface shapes of the droplet quantitatively agree well with the previous numerical results. Four typical motion modes of contact points, as observed in a recent study, are qualitatively reproduced with varying advancing and receding contact angles. The viscosity ratio is found to have a notable impact on the droplet deformation, breakup, and hysteresis behavior. Finally, this method is extended to simulate the droplet breakup in a microfluidic T junction, with one half of the wall surface ideal and the other half nonideal. Due to the contact angle hysteresis, the droplet asymmetrically breaks up into two daughter droplets with the smaller one in the nonideal branch channel, and the behavior of

  5. Lattice Boltzmann modeling of contact angle and its hysteresis in two-phase flow with large viscosity difference.

    PubMed

    Liu, Haihu; Ju, Yaping; Wang, Ningning; Xi, Guang; Zhang, Yonghao

    2015-09-01

    Contact angle hysteresis is an important physical phenomenon omnipresent in nature and various industrial processes, but its effects are not considered in many existing multiphase flow simulations due to modeling complexity. In this work, a multiphase lattice Boltzmann method (LBM) is developed to simulate the contact-line dynamics with consideration of the contact angle hysteresis for a broad range of kinematic viscosity ratios. In this method, the immiscible two-phase flow is described by a color-fluid model, in which the multiple-relaxation-time collision operator is adopted to increase numerical stability and suppress unphysical spurious currents at the contact line. The contact angle hysteresis is introduced using the strategy proposed by Ding and Spelt [Ding and Spelt, J. Fluid Mech. 599, 341 (2008)JFLSA70022-112010.1017/S0022112008000190], and the geometrical wetting boundary condition is enforced to obtain the desired contact angle. This method is first validated by simulations of static contact angle and dynamic capillary intrusion process on ideal (smooth) surfaces. It is then used to simulate the dynamic behavior of a droplet on a nonideal (inhomogeneous) surface subject to a simple shear flow. When the droplet remains pinned on the surface due to hysteresis, the steady interface shapes of the droplet quantitatively agree well with the previous numerical results. Four typical motion modes of contact points, as observed in a recent study, are qualitatively reproduced with varying advancing and receding contact angles. The viscosity ratio is found to have a notable impact on the droplet deformation, breakup, and hysteresis behavior. Finally, this method is extended to simulate the droplet breakup in a microfluidic T junction, with one half of the wall surface ideal and the other half nonideal. Due to the contact angle hysteresis, the droplet asymmetrically breaks up into two daughter droplets with the smaller one in the nonideal branch channel, and the

  6. CONTACT ANGLE OF YUCCA MOUNTAIN WELDED TUFF WITH WATER AND BRINES

    SciTech Connect

    H. Kalia

    2006-04-30

    A number of tests were performed to acquire contact angles between Yucca Mountain welded tuff from Topopah Springs Lower Lithophysal geologic unit and various brine solutions. The tests were performed on core disks received from Sample Management Facility (SMF), oven dried to a constant weight and the core disks vacuum saturated in: distilled water, J-13 water, calcium chloride brine and sodium chloride brine to constant weight. The contact angles were acquired from eight points on the surface of the core disks, four on rough surface, and four on polished surface. The contact angle was measured by placing a droplet of the test fluid, distilled water, J-13 water, calcium chloride brine and sodium chloride brine on the core disks. The objective of this test was to acquire contact angles as a potential input to estimating capillary forces in accumulated dust on the waste packages and drip shields slated for the proposed High-Level Radioactive Waste Repository at Yucca Mountain, Nevada. It was noted that once the droplet contacts the test surface, it continues to spread hence the contact angle continues to decrease with elapsed time. The maximum observed angle was at time 0 or when the drop contacted the rock surface. The measured contact angle, in all cases has significant scatter. In general, the time zero contact angles for core disks saturated in sodium chloride brine were smaller than those saturated in calcium chloride brine, distilled water, and J-13 water. The contact angles for samples saturated in distilled water, J-13 water and calcium chloride brine at time zero were similar. There was slight difference between the observed contact angles for smooth and rough surface of the test samples. The contact angles for smooth surfaces were smaller than for the rough surfaces.

  7. Utilizing dynamic tensiometry to quantify contact angle hysteresis and wetting state transitions on nonwetting surfaces.

    PubMed

    Kleingartner, Justin A; Srinivasan, Siddarth; Mabry, Joseph M; Cohen, Robert E; McKinley, Gareth H

    2013-11-01

    Goniometric techniques traditionally quantify two parameters, the advancing and receding contact angles, that are useful for characterizing the wetting properties of a solid surface; however, dynamic tensiometry, which measures changes in the net force on a surface during the repeated immersion and emersion of a solid into a probe liquid, can provide further insight into the wetting properties of a surface. We detail a framework for analyzing tensiometric results that allows for the determination of wetting hysteresis, wetting state transitions, and characteristic topographical length scales on textured, nonwetting surfaces, in addition to the more traditional measurement of apparent advancing and receding contact angles. Fluorodecyl POSS, a low-surface-energy material, was blended with commercially available poly(methyl methacrylate) (PMMA) and then dip- or spray-coated onto glass substrates. These surfaces were probed with a variety of liquids to illustrate the effects of probe liquid surface tension, solid surface chemistry, and surface texture on the apparent contact angles and wetting hysteresis of nonwetting surfaces. Woven meshes were then used as model structured substrates to add a second, larger length scale for the surface texture. When immersed into a probe liquid, these spray-coated mesh surfaces can form a metastable, solid-liquid-air interface on the largest length scale of surface texture. The increasing hydrostatic pressure associated with progressively greater immersion depths disrupts this metastable, composite interface and forces penetration of the probe liquid into the mesh structure. This transition is marked by a sudden change in the wetting hysteresis, which can be systematically probed using spray-coated, woven meshes of varying wire radius and spacing. We also show that dynamic tensiometry can accurately and quantitatively characterize topographical length scales that are present on microtextured surfaces.

  8. Dissolution-induced contact angle modification in dense nonaqueous phase liquid/water systems.

    PubMed

    Mohammad, Orphius I; Kibbey, Tohren C G

    2005-03-15

    The contact angle between DNAPL, water, and aquifer material interfaces influences the spatial distribution of DNAPLs as they infiltrate into the aquifer, and may ultimately influence their remediation. The objective of this work was to evaluate the effects of dissolution on contact angle. Just as physically retracting a sessile drop reduces its contact angle with a surface, it was speculated that dissolution could cause contact angles to be reduced. Long-term dissolution experiments were conducted over the course of days to weeks, examining the dissolution of sessile drops of two DNAPLs, trichloroethylene (TCE) and tetrachloroethylene (PCE), in water and low concentration surfactant solutions, on glass surfaces. Experiments found that dissolution led to a continuous decrease of contact angle measured through the DNAPL drop, in most cases to near 0 degrees, far lower than angles achievable through measurements of receding contact angles for the same systems. Pinning of drop contact diameter was observed in most experiments. A model developed on the basis of the Bashforth-Adams equation to predict the effect of dissolution on contact angle for drops with a pinned contact diameter showed very good agreement with experimental observations.

  9. Geysers advanced direct contact condenser research

    SciTech Connect

    Henderson, J.; Bahning, T.; Bharathan, D.

    1997-12-31

    The first geothermal application of the Advanced Direct Contact Condenser (ADCC) technology developed by the National Renewable Energy Laboratory (NREL) is now operational and is being tested at The Geysers Power Plant Unit 11. This major research effort is being supported through the combined efforts of NREL, The Department of Energy (DOE), and Pacific Gas and Electric (PG&E). NREL and PG&E have entered into a Cooperative Research And Development Agreement (CRADA) for a project to improve the direct-contact condenser performance at The Geysers Power Plant. This project is the first geothermal adaptation of an advanced condenser design developed for the Ocean Thermal Energy Conversion (OTEC) systems. PG&E expects this technology to improve power plant performance and to help extend the life of the steam field by using steam more efficiently. In accordance with the CRADA, no money is transferred between the contracting parties. In this case the Department of Energy is funding NREL for their efforts in this project and PG&E is contributing funds in kind. Successful application of this technology at The Geysers will provide a basis for NREL to continue to develop this technology for other geothermal and fossil power plant systems.

  10. An extension of Miller scaling to scale sorptivity by contact angle

    NASA Astrophysics Data System (ADS)

    Wallach, Rony; Wang, Qiuling

    2013-10-01

    This study sheds light on the limitations of using [(cos θ)½] to scale sorptivity by contact angle while reaffirming its scaling by geometrical Miller scaling factor (λ½). The sorptivity for uniform and nonuniform (wavy) capillary tubes was determined by a mathematical model that includes the effect of inertia and dynamic contact angle. Given that real porous media are preferably represented by a bundle of nonuniform rather than uniform capillary tubes, the relationship between sorptivity and contact angle was examined for different combinations of contact angles and capillary tube degrees of waviness. A general relationship of S = f [cos θ)β] (with β ≤ ½) was found. The deviation of β from ½ (associated with uniform capillary tubes) increased with contact angle and capillary waviness increase. Zero sorptivity was obtained even for wettable capillaries, θ < 90°, a phenomenon that has been generally associated with hydrophobic capillaries (θ ≥ 90°). Contact angle and nonuniform pore structure had a synergistic effect on sorptivity. Capillary nonuniformity per se diminished sorptivity but its synergy with contact angle markedly magnified this reduction. Thus, following the sorptivity impact on finger width, it is rational to assume that larger-than-zero contact angles are involved in the formation of narrow fingers with an abrupt change between the inner wet and surrounding dry areas.

  11. Measurement of contact angles of aqueous solutions on some rock forming minerals

    NASA Astrophysics Data System (ADS)

    Takakura, M.; Katsura, M.; Nakashima, S.

    2007-12-01

    Wetting properties of fluids on earth's materials are controlling fluid flows and dynamics of the geological systems. Although the wetting behavior of industrial materials have been widely examined often by contact angle measurements, contact angles of rock-forming materials have not been commonly measured. Therefore, we have been measuring contact angles of some representative rock-forming minerals. The surfaces of solid samples were polished successively by emery papers then by grinding powders (alumina: up to \\sharp3000: grain size about 5 micrometers). Water droplet from a micro-syringe needle are placed on solid surfaces by moving up the sample stage. Images of water drops on the solid surfaces are captured from the horizontal direction with a CCD camera. Contact angles can be determined from the height and the length of the images by assuming them to be parts of circles. Over 60 measurements of contact angles of pure water on (101) and (011) faces plates cut from a natural quartz single crystal were repeated. The average contact angles of pure water on (101) and (011) faces of quartz were 48 ± 5 degrees and 52 ± 3 degrees, respectively. Contact angles of pure water on a natural calcite single crystal was also measured in the same way to be 37 ± 8 degrees. Contact angles of various aqueous solutions such as NaCl and NaHCO3 on these minerals will also be measured in order to evaluate wetting properties of natural rock-water systems.

  12. Cell surface energy, contact angles and phase partition. II. Bacterial cells in biphasic aqueous mixtures.

    PubMed

    Gerson, D F; Akit, J

    1980-11-01

    Partition coefficients in biphasic mixtures of poly(ethylene glycol) and Dextran are compared to cell surface energies obtained from contact angles of each liquid phase on cell layers. Linear relationships are observed between these two independent measurements for a variety of bacterial cells. The results demonstrate the importance of interfacial phenomena and contact angles in the phase-partition process. PMID:6159003

  13. Automated contact angle estimation for three-dimensional X-ray microtomography data

    NASA Astrophysics Data System (ADS)

    Klise, Katherine A.; Moriarty, Dylan; Yoon, Hongkyu; Karpyn, Zuleima

    2016-09-01

    Multiphase flow in capillary regimes is a fundamental process in a number of geoscience applications. The ability to accurately define wetting characteristics of porous media can have a large impact on numerical models. In this paper, a newly developed automated three-dimensional contact angle algorithm is described and applied to high-resolution X-ray microtomography data from multiphase bead pack experiments with varying wettability characteristics. The algorithm calculates the contact angle by finding the angle between planes fit to each solid/fluid and fluid/fluid interface in the region surrounding each solid/fluid/fluid contact point. Results show that the algorithm is able to reliably compute contact angles using the experimental data. The in situ contact angles are typically larger than flat surface laboratory measurements using the same material. Wetting characteristics in mixed-wet systems also change significantly after displacement cycles.

  14. Mechanism of contact angle saturation and an energy-based model for electrowetting

    NASA Astrophysics Data System (ADS)

    Rui, Zhao; Zhong-Cheng, Liang

    2016-06-01

    Electrowetting, as a well-known approach to increasing droplet wettability on a solid surface by electrical bias, has broad applications. However, it is limited by contact angle saturation at large voltage. Although several debated hypotheses have been proposed to describe it, the physical origin of contact angle saturation still remains obscure. In this work, the physical factors responsible for the onset of contact angle saturation are explored, and the correlated theoretical models are established to characterize electrowetting behavior. Combination of the proper 3-phase system employed succeeds in dropping the saturating contact angle below 25°, and validates that the contact angle saturation is not a result of device-related imperfection. Project supported by the Fund from the Research Center of Optical Communications Engineering & Technology, Jiangsu Province, China (Grant No. ZSF0402).

  15. Apparent-contact-angle model at partial wetting and evaporation: Impact of surface forces

    NASA Astrophysics Data System (ADS)

    Janeček, V.; Nikolayev, V. S.

    2013-01-01

    This theoretical and numerical study deals with evaporation of a fluid wedge in contact with its pure vapor. The model describes a regime where the continuous wetting film is absent and the actual line of the triple gas-liquid-solid contact appears. A constant temperature higher than the saturation temperature is imposed at the solid substrate. The fluid flow is solved in the lubrication approximation. The introduction of the surface forces in the case of the partial wetting is discussed. The apparent contact angle (the gas-liquid interface slope far from the contact line) is studied numerically as a function of the substrate superheating, contact line velocity, and parameters related to the solid-fluid interaction (Young and microscopic contact angles, Hamaker constant, etc.). The dependence of the apparent contact angle on the substrate temperature is in agreement with existing approaches. For water, the apparent contact angle may be 20∘ larger than the Young contact angle for 1 K superheating. The effect of the surface forces on the apparent contact angle is found to be weak.

  16. Ignition angle advancer for internal combustion engine

    SciTech Connect

    Yamazaki, T.

    1986-08-19

    This patent describes a throttle and spark advance control system for an internal combustion engine having a spark advance mechanism and a throttle valve comprising an operator controlled element, a throttle control lever supported for pivotal movement about an axis and directly connected to the operator controlled element for rotation under operator control. It also includes means for positively connecting the throttle control lever to the throttle valve for positioning the throttle valve in response to movement of the throttle control lever. A spark advance control lever supported for pivotal movement about an axis is included as well as motion transmitting means for operatively connecting the spark advance control lever to the throttle control lever for pivotal movement of the spark advance control lever about its axis in response to pivotal movement of the throttle control lever about its axis and the spark control lever to the spark advance mechanism for controlling the position of the spark advance mechanism in response to the position of the throttle control lever.

  17. Estimation of bearing contact angle in-situ by X-ray kinematography

    NASA Technical Reports Server (NTRS)

    Fowler, P. H.; Manders, F.

    1982-01-01

    The mounted, preloaded contact angle of the structural bearings in the assembled design mechanical assembly was measured. A modification of the Turns method is presented, based upon the clarity and definition of moving parts achieved with X-ray technique and cinematic display. Contact angle is estimated by counting the number of bearings passing a given point as a function of number of turns of the shaft. Ball and pitch diameter variations are discussed. Ball train and shaft angle uncertainties are also discussed.

  18. Investigating How Contact Angle Effects the Interaction between Water and a Hydrophobic Surface

    NASA Astrophysics Data System (ADS)

    Poynor, Adele; Neidig, Caitlyn

    2012-02-01

    By definition hydrophobic substances hate water. What happens when water is forced into contact with a hydrophobic surface? One theory is that an ultra-thin low-density region forms near the surface. Contact angle is a measure of how hydrophobic a surface is. We have employed an automated home-built Surface Plasmon Resonance (SPR) apparatus to investigate the effect of varying the contact angle on the depletion layer

  19. Influence of Contact Angle, Growth Angle and Melt Surface Tension on Detached Solidification of InSb

    NASA Technical Reports Server (NTRS)

    Wang, Yazhen; Regel, Liya L.; Wilcox, William R.

    2000-01-01

    We extended the previous analysis of detached solidification of InSb based on the moving meniscus model. We found that for steady detached solidification to occur in a sealed ampoule in zero gravity, it is necessary for the growth angle to exceed a critical value, the contact angle for the melt on the ampoule wall to exceed a critical value, and the melt-gas surface tension to be below a critical value. These critical values would depend on the material properties and the growth parameters. For the conditions examined here, the sum of the growth angle and the contact angle must exceed approximately 130, which is significantly less than required if both ends of the ampoule are open.

  20. Relation between contact angles and formation of fog on polymer surfaces

    NASA Astrophysics Data System (ADS)

    Grosu, Gabriela; Ross, Guy G.; Abel, Gilles; Andrzejewski, Lukasz

    2004-03-01

    Formation of fog on surfaces is cause of accidents in sports and industries. Formation of fog is not observed on very wetting polymer surfaces such as CR-39 and PC. Using 3 keV Ar ion implantation under an O2 partial pressure, advancing (ACA) and receding (RCA) contact angles as low as 10o and 20o, respectively, have been obtained. Fog is not observed on such wetting surfaces. Unfortunately, both contact angles increase with time. This phenomena, called aging, avoids the use of this technique for commercial application. Also, a correlation between the ACA and RCA and the dimension of fog droplets has been established. The RCA seems to play an important role. Passivation of implanted samples in O2 gas is a little help for the aging control. However, the pre-implantation of He has reduced the increase of both the ACA and, especially, the RCA. A direct consequence is that, up to now, no fog has been observed on the surfaces treated by He and Ar co-implantation. A characterization of surfaces by XPS has been undertaken. The relative concentration of polar molecules could be an explanation. The results will be presented and discussed.

  1. The influence of incident angle on physical properties of a novel back contact prepared by oblique angle deposition

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Zhao, Yue; Feng, Yue; Shen, Jiesheng; Liang, Xiaoyan; Huang, Jian; Min, Jiahua; Wang, Linjun; Shi, Weimin

    2016-02-01

    In this paper, oblique vacuum thermal evaporation and direct current (DC) magnetron sputtering technique are used to produce a novel back contact electrode (BCE) of CuInS2 solar cell. These novel back contact electrodes (BCEs) are based on a layered structure of Mo/Ag/Mo (MAM). The influence of vapor source incidence angle θ on optical-electrical properties of novel BCE is investigated by X-ray Diffraction (XRD), Surface Profiler, Atomic Force Microscope (AFM), UV-vis-IR Spectrometer, and Four-point Probe Method. According to the analysis of AFM images of BCEs, the variation tendencies of surface roughness and uniformity are closely related to the incidence angle θ. The surface roughness increases with the increase of incidence angle θ, but the uniformity becomes poor at same time. This phenomenon can be attributed to the variation of interlayer Ag films (the density and inclined angle of Ag nanorods). The results of four-point probe test show that the novel BCE deposited by vapor source incidence angle θ equal to 45° owns the lowest resistance value of 3.71 × 10-8 Ω m, which is probably due to a loose and multi-point contact interface between Ag layer and top layer (Mo2). The reflectance of novel BCEs deposited by incident angle less than 45° is higher than that of normal bi-layer Mo (Mo12) BCE. As a result, the efficiency of corresponding solar cell may be upgraded.

  2. Contact angle adjustment in equation-of-state-based pseudopotential model.

    PubMed

    Hu, Anjie; Li, Longjian; Uddin, Rizwan; Liu, Dong

    2016-05-01

    The single component pseudopotential lattice Boltzmann model has been widely applied in multiphase simulation due to its simplicity and stability. In many studies, it has been claimed that this model can be stable for density ratios larger than 1000. However, the application of the model is still limited to small density ratios when the contact angle is considered. The reason is that the original contact angle adjustment method influences the stability of the model. Moreover, simulation results in the present work show that, by applying the original contact angle adjustment method, the density distribution near the wall is artificially changed, and the contact angle is dependent on the surface tension. Hence, it is very inconvenient to apply this method with a fixed contact angle, and the accuracy of the model cannot be guaranteed. To solve these problems, a contact angle adjustment method based on the geometry analysis is proposed and numerically compared with the original method. Simulation results show that, with our contact angle adjustment method, the stability of the model is highly improved when the density ratio is relatively large, and it is independent of the surface tension. PMID:27301005

  3. Simultaneous Soft Sensing of Tissue Contact Angle and Force for Millimeter-scale Medical Robots

    PubMed Central

    Arabagi, Veaceslav; Gosline, Andrew; Wood, Robert J.; Dupont, Pierre E.

    2013-01-01

    A novel robotic sensor is proposed to measure both the contact angle and the force acting between the tip of a surgical robot and soft tissue. The sensor is manufactured using a planar lithography process that generates microchannels that are subsequently filled with a conductive liquid. The planar geometry is then molded onto a hemispherical plastic scaffolding in a geometric configuration enabling estimation of the contact angle (angle between robot tip tangent and tissue surface normal) by the rotation of the sensor around its roll axis. Contact force can also be estimated by monitoring the changes in resistance in each microchannel. Bench top experimental results indicate that, on average, the sensor can estimate the angle of contact to within ±2° and the contact force to within ±5.3 g. PMID:24241496

  4. Measuring contact angle and meniscus shape with a reflected laser beam

    SciTech Connect

    Eibach, T. F.; Nguyen, H.; Butt, H. J.; Auernhammer, G. K.; Fell, D.

    2014-01-15

    Side-view imaging of the contact angle between an extended planar solid surface and a liquid is problematic. Even when aligning the view perfectly parallel to the contact line, focusing one point of the contact line is not possible. We describe a new measurement technique for determining contact angles with the reflection of a widened laser sheet on a moving contact line. We verified this new technique measuring the contact angle on a cylinder, rotating partially immersed in a liquid. A laser sheet is inclined under an angle φ to the unperturbed liquid surface and is reflected off the meniscus. Collected on a screen, the reflection image contains information to determine the contact angle. When dividing the laser sheet into an array of laser rays by placing a mesh into the beam path, the shape of the meniscus can be reconstructed from the reflection image. We verified the method by measuring the receding contact angle versus speed for aqueous cetyltrimethyl ammonium bromide solutions on a smooth hydrophobized as well as on a rough polystyrene surface.

  5. Considering Hydrophobicity via Contact Angle Stability of Organic Thiols Measured with a Homemade Goniometer

    NASA Astrophysics Data System (ADS)

    Seraly, Mark; Ollander, Brooke; Statman, Ariel; Poynor, Adele

    2014-03-01

    When water meets an extended hydrophobic surface, an ultra-thin, low-density depletion layer is expected at the interface. Exactly how the depletion layer changes with change in hydrophobicity is still an open question. An accurate measure of contact angle is essential in determining how water meets a hydrophobic surface. Utilizing a homemade goniometer with ImageJ software we investigate the stability of self-assembled organic thiol monolayers, 1-octadecanethiol (ODT) and 11-mercaptoundecanoic acid (MUA). We report the changes in contact angle due to exposure to air, water, and ethanol. Other factors that affect contact angles were also considered in our investigation.

  6. Effect of relative humidity on contact angle of inkjet-printed evaporating colloidal drops

    NASA Astrophysics Data System (ADS)

    Chhasatia, Viral; Joshi, Abhijit; Sun, Ying

    2010-11-01

    The deposition behavior of inkjet-printed aqueous colloidal drops onto glass and polymer (PEN and PET) substrates has been investigated by using fluorescence microscopy, a high-resolution CCD camera, and scanning electron microscopy. Real-time side-view images show that the contact angle of an evaporating colloidal drop is a function of the ambient humidity. The relative humidity also affects the extent to which the drop is able to spread after impacting a substrate, the evaporation rate at the drop surface, and the evaporatively-driven flow inside the drop that drives the suspended particles towards the contact line. The difference between the contact line velocity and liquid velocity at the drop contact line induced by evaporation creates a larger contact angle compared to that of the case without evaporation. This increase in contact angle becomes more significant for a low ambient humidity. Results also show that the particle deposition area and pattern change with the ambient humidity.

  7. Novel film-calliper method of measuring the contact angle of colloidal particles at liquid interfaces.

    PubMed

    Horozov, Tommy S; Braz, Dulce A; Fletcher, Paul D I; Binks, Bernard P; Clint, John H

    2008-03-01

    A simple and reliable film-calliper method of measuring the particle contact angle at the water-air (oil) interface in real time has been developed. Its applicability to submicrometer and micrometer latex and silica particles is demonstrated.

  8. Prediction of static contact angles on the basis of molecular forces and adsorption data.

    PubMed

    Diaz, M Elena; Savage, Michael D; Cerro, Ramon L

    2016-08-01

    At a three-phase contact line, a liquid bulk phase is in contact with and coexists with a very thin layer of adsorbed molecules. This adsorbed film in the immediate vicinity of a liquid wedge modifies the balance of forces between the liquid and solid phases such that, when included in the balance of forces, a quantitative relationship emerges between the adsorbed film thickness and the static contact angle. This relationship permits the prediction of static contact angles from molecular forces and equilibrium adsorption data by means of quantities that are physically meaningful and measurable. For n-alkanes on polytetrafluoroethylene, for which there are experimental data available on adsorption and contact angles, our computations show remarkable agreement with the data. The results obtained are an improvement on previously published calculations-particularly for alkanes with a low number of carbon atoms, for which adsorption is significant. PMID:27627371

  9. Prediction of static contact angles on the basis of molecular forces and adsorption data

    NASA Astrophysics Data System (ADS)

    Diaz, M. Elena; Savage, Michael D.; Cerro, Ramon L.

    2016-08-01

    At a three-phase contact line, a liquid bulk phase is in contact with and coexists with a very thin layer of adsorbed molecules. This adsorbed film in the immediate vicinity of a liquid wedge modifies the balance of forces between the liquid and solid phases such that, when included in the balance of forces, a quantitative relationship emerges between the adsorbed film thickness and the static contact angle. This relationship permits the prediction of static contact angles from molecular forces and equilibrium adsorption data by means of quantities that are physically meaningful and measurable. For n-alkanes on polytetrafluoroethylene, for which there are experimental data available on adsorption and contact angles, our computations show remarkable agreement with the data. The results obtained are an improvement on previously published calculations—particularly for alkanes with a low number of carbon atoms, for which adsorption is significant.

  10. Prediction of static contact angles on the basis of molecular forces and adsorption data.

    PubMed

    Diaz, M Elena; Savage, Michael D; Cerro, Ramon L

    2016-08-01

    At a three-phase contact line, a liquid bulk phase is in contact with and coexists with a very thin layer of adsorbed molecules. This adsorbed film in the immediate vicinity of a liquid wedge modifies the balance of forces between the liquid and solid phases such that, when included in the balance of forces, a quantitative relationship emerges between the adsorbed film thickness and the static contact angle. This relationship permits the prediction of static contact angles from molecular forces and equilibrium adsorption data by means of quantities that are physically meaningful and measurable. For n-alkanes on polytetrafluoroethylene, for which there are experimental data available on adsorption and contact angles, our computations show remarkable agreement with the data. The results obtained are an improvement on previously published calculations-particularly for alkanes with a low number of carbon atoms, for which adsorption is significant.

  11. Assessing the accuracy of contact angle measurements for sessile drops on liquid-repellent surfaces.

    PubMed

    Srinivasan, Siddarth; McKinley, Gareth H; Cohen, Robert E

    2011-11-15

    Gravity-induced sagging can amplify variations in goniometric measurements of the contact angles of sessile drops on super-liquid-repellent surfaces. The very large value of the effective contact angle leads to increased optical noise in the drop profile near the solid-liquid free surface and the progressive failure of simple geometric approximations. We demonstrate a systematic approach to determining the effective contact angle of drops on super-repellent surfaces. We use a perturbation solution of the Bashforth-Adams equation to estimate the contact angles of sessile drops of water, ethylene glycol, and diiodomethane on an omniphobic surface using direct measurements of the maximum drop width and height. The results and analysis can be represented in terms of a dimensionless Bond number that depends on the maximum drop width and the capillary length of the liquid to quantify the extent of gravity-induced sagging. Finally, we illustrate the inherent sensitivity of goniometric contact angle measurement techniques to drop dimensions as the apparent contact angle approaches 180°. PMID:21923173

  12. Effects of Evaporation/Condensation on Spreading and Contact Angle of a Volatile Liquid Drop

    NASA Technical Reports Server (NTRS)

    Zhang, Nengli; Chao, David F.; Singh, Bhim S. (Technical Monitor)

    2000-01-01

    Effects of evaporation/condensation on spreading and contact angle were experimentally studied. A sessile drop of R-113 was tested at different vapor environments to determine the effects of evaporation/condensation on the evolution of contact diameter and contact angle of the drop. Condensation on the drop surface occurs at both the saturated and a nonsaturated vapor environments and promotes the spreading. When the drop is placed in the saturated vapor environment it tends to completely wetting and spreads rapidly. In a nonsaturated vapor environment, the evolution of the sessile drop is divided three stages: condensation-spreading stage, evaporation-retracting stage and rapid contracting stage. In the first stage the drop behaves as in the saturated environment. In the evaporation -retracting stage, the competition between spreading and evaporation of the drop determines the evolution characteristics of the contact diameter and the contact angle. A lower evaporation rate struggles against the spreading power to turn the drop from spreading to retracting with a continuous increase of the contact angle. The drop placed in open air has a much higher evaporation rate. The strong evaporation suppresses the spreading and accelerates the retraction of the drop with a linear decrease of the contact diameter. The contraction of the evaporating drops is gradually accelerated when the contact diameter decreases to 3 min and less till drying up, though the evaporation rate is gradually slowing down.

  13. Contact angle determination procedure and detection of an invisible surface film

    NASA Technical Reports Server (NTRS)

    Meyer, G.; Grat, R.

    1990-01-01

    The contact angle value, i.e., the tangent angle of liquid resting on a planar solid surface, is a basic parameter which can be applied to a wide range of applications. The goal is to provide a basic understanding of the contact angle measurement technique and to present a simple illustration that can be applied as a quality control method; namely, detection of a surface contaminant which exists on a surface that appears clean to the unaided eye. The equipment and experimental procedures are detailed.

  14. Wettability of supercritical carbon dioxide/water/quartz systems: simultaneous measurement of contact angle and interfacial tension at reservoir conditions.

    PubMed

    Saraji, Soheil; Goual, Lamia; Piri, Mohammad; Plancher, Henry

    2013-06-11

    Injection of carbon dioxide in deep saline aquifers is considered as a method of carbon sequestration. The efficiency of this process is dependent on the fluid-fluid and rock-fluid interactions inside the porous media. For instance, the final storage capacity and total amount of capillary-trapped CO2 inside an aquifer are affected by the interfacial tension between the fluids and the contact angle between the fluids and the rock mineral surface. A thorough study of these parameters and their variations with temperature and pressure will provide a better understanding of the carbon sequestration process and thus improve predictions of the sequestration efficiency. In this study, the controversial concept of wettability alteration of quartz surfaces in the presence of supercritical carbon dioxide (sc-CO2) was investigated. A novel apparatus for measuring interfacial tension and contact angle at high temperatures and pressures based on Axisymmetric Drop Shape Analysis with no-Apex (ADSA-NA) method was developed and validated with a simple system. Densities, interfacial tensions, and dynamic contact angles of CO2/water/quartz systems were determined for a wide range of pressures and temperatures relevant to geological sequestration of CO2 in the subcritical and supercritical states. Image analysis was performed with ADSA-NA method that allows the determination of both interfacial tensions and contact angles with high accuracy. The results show that supercritical CO2 alters the wettability of quartz surface toward less water-wet conditions compared to subcritical CO2. Also we observed an increase in the water advancing contact angles with increasing temperature indicating less water-wet quartz surfaces at higher temperatures.

  15. Direct determination of contact angles of model soils in comparison with wettability characterization by capillary rise

    NASA Astrophysics Data System (ADS)

    Ramírez-Flores, Juan Carlos; Bachmann, Jörg; Marmur, Abraham

    2010-03-01

    SummaryAn accurate method to determine contact angles (CA) of soils as a measure of water repellency is still missing. In the present research, we evaluated and compared different methods to determine the CA of dry soil samples. Experiments were made by using a set of porous materials (silt, sand and glass beads) with different levels of water repellency. The CAs were measured with the Capillary Rise Method ( θCRM; liquid penetration into a 3-d system), the Wilhelmy plate method ( θWPM; measurement of capillary forces acting on a plane sample) and the Sessile Drop Method ( θSDM; optical CA analysis of drop contour on a plane sample). Results were compared with the CAs calculated from capillary rise in long vertical columns ( θECR), where liquid profiles of the final capillary rise of water and ethanol, respectively, were used to derive the contact angle under the assumed equilibrium conditions. The results showed the overestimation of the CA by using the well established bi-liquid CRM technique for porous materials, in particular for material with a low degree of water repellency (CA < 40°) and for the finer textured materials. In contrast, a variant of the Wilhelmy plate method, i.e. the cosine-averaged advancing CA and receding CA ( θEWPM), as well as the Sessile Drop CA, θSDM, were close to the ones of θECR. We concluded that θEWPM and θSDM are apparent CA, but nevertheless able to predict the impact of wettability on the final capillary rise which is affected by pore topology as well as by wettability.

  16. Experimental Investigation of the Contact Angle at Wetting the Non-ferrous Metals

    NASA Astrophysics Data System (ADS)

    Feoktistov, D. V.; Orlova, E. G.; Ponomarev, K. O.

    2015-10-01

    Experimental dependences on the effect of the drop volume from the contact angle under the conditions of the static three-phase contact line formation during wetting the nonferrous metals (aluminium, magnalium, copper and brass) are presented in the work. The surface of the substrates was investigated by modern equipment (profilometer "Micro Measure 3D station" and microscope TM-3000). The drop was placed on the surface by the precision electronic single-channel pipette (Thermo scientific). Shadow method was used to obtain the drop profile; symmetry of the drop was controlled by Schlieren method. The comparison of the methods used to determine the contact angle on the image of the drop profile was executed. It was established that in spite of influencing the friction and gravity forces the structure of metal surfaces affects greatly the value of the contact angle.

  17. Flow Visualization in Evaporating Liquid Drops and Measurement of Dynamic Contact Angles and Spreading Rate

    NASA Technical Reports Server (NTRS)

    Zhang, Neng-Li; Chao, David F.

    2001-01-01

    A new hybrid optical system, consisting of reflection-refracted shadowgraphy and top-view photography, is used to visualize flow phenomena and simultaneously measure the spreading and instant dynamic contact angle in a volatile-liquid drop on a nontransparent substrate. Thermocapillary convection in the drop, induced by evaporation, and the drop real-time profile data are synchronously recorded by video recording systems. Experimental results obtained from this unique technique clearly reveal that thermocapillary convection strongly affects the spreading process and the characteristics of dynamic contact angle of the drop. Comprehensive information of a sessile drop, including the local contact angle along the periphery, the instability of the three-phase contact line, and the deformation of the drop shape is obtained and analyzed.

  18. A highly accurate dynamic contact angle algorithm for drops on inclined surface based on ellipse-fitting.

    PubMed

    Xu, Z N; Wang, S Y

    2015-02-01

    To improve the accuracy in the calculation of dynamic contact angle for drops on the inclined surface, a significant number of numerical drop profiles on the inclined surface with different inclination angles, drop volumes, and contact angles are generated based on the finite difference method, a least-squares ellipse-fitting algorithm is used to calculate the dynamic contact angle. The influences of the above three factors are systematically investigated. The results reveal that the dynamic contact angle errors, including the errors of the left and right contact angles, evaluated by the ellipse-fitting algorithm tend to increase with inclination angle/drop volume/contact angle. If the drop volume and the solid substrate are fixed, the errors of the left and right contact angles increase with inclination angle. After performing a tremendous amount of computation, the critical dimensionless drop volumes corresponding to the critical contact angle error are obtained. Based on the values of the critical volumes, a highly accurate dynamic contact angle algorithm is proposed and fully validated. Within nearly the whole hydrophobicity range, it can decrease the dynamic contact angle error in the inclined plane method to less than a certain value even for different types of liquids.

  19. Wetting of biopolymer coatings: contact angle kinetics and image analysis investigation.

    PubMed

    Farris, Stefano; Introzzi, Laura; Biagioni, Paolo; Holz, Torsten; Schiraldi, Alberto; Piergiovanni, Luciano

    2011-06-21

    The surface wetting of five biopolymers, used as coating materials for a plastic film, was monitored over a span of 8 min by means of the optical contact angle technique. Because most of the total variation was observed to occur during the first 60 s, we decided to focus on this curtailed temporal window. Initial contact angle values (θ(0)) ranged from ∼91° for chitosan to ∼30° for pullulan. However, the water drop profile began to change immediately following drop deposition for all biocoatings, confirming that the concept of water contact angle equilibrium is not applicable to most biopolymers. First, a three-parameter decay equation [θ(t) = θ(0) exp(kt(n))] was fit to the experimental contact angle data to describe the kinetics of the contact angle change for each biocoating. Interestingly, the k constant correlated well with the contact angle evolution rate and the n exponent seemed to be somehow linked to the physicochemical phenomena underlying the overall kinetics process. Second, to achieve a reliable description of droplet evolution, the contact angle (CA) analysis was coupled with image analysis (IA) through a combined geometric/trigonometric approach. Absorption and spreading were the key factors governing the overall mechanism of surface wetting during the 60 s analysis, although the individual quantification of both phenomena demonstrated that spreading provided the largest contribution for all biopolymers, with the only exception of gelatin, which showed two quasi-equivalent and counterbalancing effects. The possible correlation between these two phenomena and the topography of the biopolymer surfaces are then discussed on the basis of atomic force microscopy analyses. PMID:21619017

  20. Contact-angle measurements as a means of probing the surface alignment characteristics of liquid crystal materials on photoalignment layers

    NASA Astrophysics Data System (ADS)

    Marshall, K. L.; Didovets, O.; Saulnier, D.

    2014-10-01

    The exceptionally high 1054-nm laser-damage resistance of photoalignment materials (approaching that of fused silica) has made it possible to fabricate a wide variety of photoaligned liquid crystal (LC) devices for high-peak-power laser applications. Despite these advances, materials selection and photoalignment exposure conditions are still determined using costly and time-consuming "trial-and-error" methods. The contact angle of a fluid droplet on an alignment layer yields important information about LC-surface physicochemical interactions, and as such, it has potential as a rapid and convenient metric for optimizing photoaligned device quality. To this end, we report on efforts to correlate fluid contact angle with surface energy and azimuthal-anchoring energy to aid in the assessment of alignment quality in photoalignment materials systems.

  1. Influence of temperature and pressure on quartz-water-CO₂ contact angle and CO₂-water interfacial tension.

    PubMed

    Sarmadivaleh, Mohammad; Al-Yaseri, Ahmed Z; Iglauer, Stefan

    2015-03-01

    We measured water-CO2 contact angles on a smooth quartz surface (RMS surface roughness ∼40 nm) as a function of pressure and temperature. The advancing water contact angle θ was 0° at 0.1 MPa CO2 pressure and all temperatures tested (296-343 K); θ increased significantly with increasing pressure and temperature (θ=35° at 296 K and θ=56° at 343 K at 20 MPa). A larger θ implies less structural and residual trapping and thus lower CO2 storage capacities at higher pressures and temperatures. Furthermore we did not identify any significant influence of CO2-water equilibration on θ. Moreover, we measured the CO2-water interfacial tension γ and found that γ strongly decreased with increasing pressure up to ∼10 MPa, and then decreased with a smaller slope with further increasing pressure. γ also increased with increasing temperature.

  2. Darcy's Flow with Prescribed Contact Angle: Well-Posedness and Lubrication Approximation

    NASA Astrophysics Data System (ADS)

    Knüpfer, Hans; Masmoudi, Nader

    2015-11-01

    We consider the spreading of a thin two-dimensional droplet on a solid substrate. We use a model for viscous fluids where the evolution is governed by Darcy's law. At the contact point where air and liquid meet the solid substrate, a constant, non-zero contact angle ( partial wetting) is assumed. We show local and global well-posedness of this free boundary problem in the presence of the moving contact point. Our estimates are uniform in the contact angle assumed by the liquid at the contact point. In the so-called lubrication approximation (long-wave limit) we show that the solutions converge to the solution of a one-dimensional degenerate parabolic fourth order equation which belongs to a family of thin-film equations. The main technical difficulty is to describe the evolution of the non-smooth domain and to identify suitable spaces that capture the transition to the asymptotic model uniformly in the small parameter.

  3. Contact angles of substances used for internal tamponade in retinal detachment surgery.

    PubMed

    Fawcett, I M; Williams, R L; Wong, D

    1994-07-01

    In order to ascertain the tamponade effect of air and silicone oil we examined the contact angles subtended by ex vivo human retina, Teflon and Perspex to find a suitable experimental material which would mimic the surface properties of the retina at a three-phase interface. Using the captive bubble technique to measure the contact angle, it was found that air subtended a larger contact angle (38.8 degrees) with the retina than did silicone oil (18.2 degrees). On coating the Perspex surface with protein (PCP), it was observed that the surface properties were modified such that PCP subtended contact angles with air (43.0 degrees) and silicone oil (16.4 degrees) similar to those subtended by ex vivo human retina. Using PCP as an experimental material that mimics ex vivo human retina, spherical chambers were employed in order to examine qualitatively and to quantify the arc of contact obtained with air and silicone oil. It was found that air gave a greater arc of contact for the same percentage fill than silicone oil. PMID:7926877

  4. Manipulation of Contact Angles and Interfacial Lengths of Liquid Drops using Electro-Kinetic Techniques

    NASA Astrophysics Data System (ADS)

    Zhou, X.; Nolte, D. D.; Pyrak-Nolte, L. J.

    2014-12-01

    Traditionally, capillary pressure is determined by increasing or decreasing external fluid pressures to change the immiscible fluid saturation in a porous medium. The resulting saturation and interfacial area are then linked to the capillary pressure through constitutive equations. A key question is whether externally measured pressures are sensitive to changes in distributions that arise from internal changes in contact angles. As a first step in addressing this question, we investigated the effect of electro-kinetic manipulation on interfacial area and contact angles for a fixed saturation. An EWOD (electro-wetting on dielectric) technique was used to alter the contact angle of single 10 μL droplets of a 1M KCl-H2O solution. A liquid droplet was placed on a glass cover slip (18 mm x 18 mm) coated with a layer of silver (100 nm in thickness) to act as an electrode and then spin-coated with polyimide (a dielectric). A platinum wire was inserted into the droplet and connected to an AC voltage source. The glass plate electrode was connected to ground. Measurements were made for Vrms voltages between 0 to 300 V at a frequency of 50 Hz. Two CCD cameras were used to image changes in the shape of a droplet. One camera was placed on a microscope to capture a top view of a drop in order to measure changes in areal extent and the perimeter of the drop. The second camera imaged a drop from the side to measure contact angles and side-view areal extent and perimeter. At low voltages, the cosine of the contact angle, θ, after applying voltage was linearly dependent on Vrms2. Several experiments showed that the slope of the low-voltage relationship of cos θ vs Vrms2 remained constant for all trials. As the voltage increased, the contact angle saturated. From the side-view images, the contact angle and interfacial length decreased with increasing voltage. From the top-view images, the drop shape changed from circular to elliptical-to irregular as the voltage increased

  5. High-precision drop shape analysis (HPDSA) of quasistatic contact angles on silanized silicon wafers with different surface topographies during inclining-plate measurements: Influence of the surface roughness on the contact line dynamics

    NASA Astrophysics Data System (ADS)

    Heib, F.; Hempelmann, R.; Munief, W. M.; Ingebrandt, S.; Fug, F.; Possart, W.; Groß, K.; Schmitt, M.

    2015-07-01

    Contact angles and wetting of solid surfaces are strongly influenced by the physical and chemical properties of the surfaces. These influence quantities are difficult to distinguish from each other if contact angle measurements are performed by measuring only the advancing θa and the receding θr contact angle. In this regard, time-dependent water contact angles are measured on two hydrophobic modified silicon wafers with different physical surface topographies. The first surface is nearly atomically flat while the second surface is patterned (alternating flat and nanoscale rough patterns) which is synthesized by a photolithography and etching procedure. The different surface topographies are characterized with atomic force microscopy (AFM), Fourier transform infrared reflection absorption spectroscopy (FTIRRAS) and Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR). The resulting set of contact angle data obtained by the high-precision drop shape analysis approach is further analyzed by a Gompertzian fitting procedure and a statistical counting procedure in dependence on the triple line velocity. The Gompertzian fit is used to analyze overall properties of the surface and dependencies between the motion on the front and the back edge of the droplets. The statistical counting procedure results in the calculation of expectation values E(p) and standard deviations σ(p) for the inclination angle φ, contact angle θ, triple line velocity vel and the covered distance of the triple line dis relative to the first boundary points XB,10. Therefore, sessile drops during the inclination of the sample surface are video recorded and different specific contact angle events in dependence on the acceleration/deceleration of the triple line motion are analyzed. This procedure results in characteristically density distributions in dependence on the surface properties. The used procedures lead to the possibility to investigate influences on contact

  6. Experimental Study on the Effect of Liquid Contact Angle on Bubble Movement under Microgravity

    NASA Astrophysics Data System (ADS)

    Yanjie, Yang; Li, Shiyou; Yiyong, Huang; Guangyu, Li

    2016-07-01

    The experimental study of bubble dynamics under microgravity has been conducted utilizing the Drop Tower Beijing(NMLC). A pottery sized of 20mm in length, 10mm in width and 1.2mm in height was used as the heater. The fluid was HFE7500 and distilled water. During the experiment under microgravity the nucleate boiling and film boiling were observed. At the same heating power the bubble of HFE7500 whose contact angle is smaller grew faster and bigger, moved quickly on the heating surface, combined into center big bubble by colliding and reached its CHF earlier to film boiling. The bubble of distilled water whose contact angle is bigger didn't move obviously on heating surface, and it transferred from nucleate boiling to film boiling at its original place meanwhile it absorbed smaller bubble around. Key words: microgravity; bubble movement; contact angle; drop tower

  7. Insights into bacterial contact angles: difficulties in defining hydrophobicity and surface Gibbs energy.

    PubMed

    Gallardo-Moreno, Amparo M; Navarro-Pérez, M Luisa; Vadillo-Rodríguez, Virginia; Bruque, José M; González-Martín, M Luisa

    2011-11-01

    One of the principal techniques for evaluating the surface hydrophobicity of biological samples is contact angle. This method, applied readily to flat-smooth-inert surfaces, gives rise to an important debate when implemented with microbial lawns. After its initial description, in 1984, several authors have carried out modifications of the technique but the results obtained have not been previously judged. This work focuses on the particularities of contact angle measurements on bacterial lawns and enhances the idea of the impossibility of using water contact angle as a universal measurement of bacterial hydrophobicity. Contact angles can only be used as relative indicators of hydrophobicity, in a similar way to tests based on microbial adhesion to solvents. The strong dependence of contact angles on dried bacterial lawns with measuring time and environmental conditions (e.g. pH of the media) preclude the estimation of their absolute values, and so, of the cells surface Gibbs energy. Yet, for a given measuring time, it is found that the hydrophobicity and the apparent bacterial surface Gibbs energy components are qualitatively related to the bacterial surface electrical potential. In particular, a hydrophobic increase is always accompanied by an increase of the cells Lifshitz-Van der Waals component and a decrease of their acid-base component and absolute zeta potential. Therefore, the present study shows that the physico-chemical surface properties that characterize bacteria are not independent, and one of them can be qualitatively described in terms of the others when measuring contact angles at a fixed time after the drying of the microbial beds.

  8. Contact angles and wettability of ionic liquids on polar and non-polar surfaces†

    PubMed Central

    Sousa, Filipa L.; Silva, Nuno J. O.; Lopes-da-Silva, José A.; Coutinho, João A. P.; Freire, Mara G.

    2016-01-01

    Many applications involving ionic liquids (ILs) require the knowledge of their interfacial behaviour, such as wettability and adhesion. In this context, herein, two approaches were combined aiming at understanding the impact of the IL chemical structures on their wettability on both polar and non-polar surfaces, namely: (i) the experimental determination of the contact angles of a broad range of ILs (covering a wide number of anions of variable polarity, cations, and cation alkyl side chain lengths) on polar and non-polar solid substrates (glass, Al-plate, and poly-(tetrafluoroethylene) (PTFE)); and (ii) the correlation of the experimental contact angles with the cation–anion pair interaction energies generated by the Conductor-like Screening Model for Real Solvents (COSMO-RS). The combined results reveal that the hydrogen-bond basicity of ILs, and thus the IL anion, plays a major role through their wettability on both polar and non-polar surfaces. The increase of the IL hydrogen-bond accepting ability leads to an improved wettability of more polar surfaces (lower contact angles) while the opposite trend is observed on non-polar surfaces. The cation nature and alkyl side chain lengths have however a smaller impact on the wetting ability of ILs. Linear correlations were found between the experimental contact angles and the cation–anion hydrogen-bonding and cation ring energies, estimated using COSMO-RS, suggesting that these features primarily control the wetting ability of ILs. Furthermore, two-descriptor correlations are proposed here to predict the contact angles of a wide variety of ILs on glass, Al-plate, and PTFE surfaces. A new extended list is provided for the contact angles of ILs on three surfaces, which can be used as a priori information to choose appropriate ILs before a given application. PMID:26554705

  9. Contact angles and wettability of ionic liquids on polar and non-polar surfaces.

    PubMed

    Pereira, Matheus M; Kurnia, Kiki A; Sousa, Filipa L; Silva, Nuno J O; Lopes-da-Silva, José A; Coutinho, João A P; Freire, Mara G

    2015-12-21

    Many applications involving ionic liquids (ILs) require the knowledge of their interfacial behaviour, such as wettability and adhesion. In this context, herein, two approaches were combined aiming at understanding the impact of the IL chemical structures on their wettability on both polar and non-polar surfaces, namely: (i) the experimental determination of the contact angles of a broad range of ILs (covering a wide number of anions of variable polarity, cations, and cation alkyl side chain lengths) on polar and non-polar solid substrates (glass, Al-plate, and poly-(tetrafluoroethylene) (PTFE)); and (ii) the correlation of the experimental contact angles with the cation-anion pair interaction energies generated by the Conductor-like Screening Model for Real Solvents (COSMO-RS). The combined results reveal that the hydrogen-bond basicity of ILs, and thus the IL anion, plays a major role through their wettability on both polar and non-polar surfaces. The increase of the IL hydrogen-bond accepting ability leads to an improved wettability of more polar surfaces (lower contact angles) while the opposite trend is observed on non-polar surfaces. The cation nature and alkyl side chain lengths have however a smaller impact on the wetting ability of ILs. Linear correlations were found between the experimental contact angles and the cation-anion hydrogen-bonding and cation ring energies, estimated using COSMO-RS, suggesting that these features primarily control the wetting ability of ILs. Furthermore, two-descriptor correlations are proposed here to predict the contact angles of a wide variety of ILs on glass, Al-plate, and PTFE surfaces. A new extended list is provided for the contact angles of ILs on three surfaces, which can be used as a priori information to choose appropriate ILs before a given application.

  10. Superhydrophobic surfaces: A model approach to predict contact angle and surface energy of soil particles

    NASA Astrophysics Data System (ADS)

    Shirtcliffe, Neil; Hamlett, Christopher; McHale, Glen; Newton, Michael; Bachmann, Joerg; Woche, S.

    2010-05-01

    C. Hamlett(a), G. McHALE(a), N. Shirtcliffe(a), M. Newton(a), S.K. Woche(b), and J. BACHMANN(b) aSchool of Science & Technology, Nottingham Trent University, Clifton Lane, Nottingham, NG11 8NS, UK and bInstitute of Soil Science, Leibniz University Hannover, Herrenhaeuser Str.2, 30419, Hannover, Germany. Summary Wettability of soil affects a wide variety of processes including infiltration, preferential flow and surface runoff. The problem of determining contact angles and surface energy of powders, such as soil particles, remains unsolved. So far, several theories and approaches have been proposed, but formulation of surface and interfacial free energy, as regards its components, is still a very debatable issue. In the present study, the general problem of the interpretation of contact angles and surface free energy on chemically heterogeneous and rough soil particle surfaces are evaluated by a reformulation of the Cassie-Baxter equation assuming that the particles are attached on to a plane and rigid surface. Compared with common approaches, our model considers a roughness factor which depends on the Young's Law contact angle determined by the surface chemistry. Results of the model are discussed and compared with independent contact angle measurements using the Sessile Drop and the Wilhelmy Plate methods. Based on contact angle data, the critical surface tension of the grains were determined by the method proposed by Zisman. Experiments were made with glass beads and three soil materials ranging from sand to clay. Soil particles were coated with different loadings of dichlorodimethylsilane (DCDMS) to vary the wettability. Varying the solid surface tension using DCDMS treatments provided pure water wetting behaviours ranging from wettable to extremely hydrophobic with contact angles >150°. Results showed that the critical surface energy measured on grains with the highest DCDMS loadings was similar to the surface energy measured independently on ideal DCDMS

  11. Liquid-bridge stability and breakup on surfaces with contact-angle hysteresis.

    PubMed

    Akbari, Amir; Hill, Reghan J

    2016-08-10

    We study the stability and breakup of liquid bridges with a free contact line on surfaces with contact-angle hysteresis (CAH) under zero-gravity conditions. Non-ideal surfaces exhibit CAH because of surface imperfections, by which the constraints on three-phase contact lines are influenced. Given that interfacial instabilities are constraint-sensitive, understanding how CAH affects the stability and breakup of liquid bridges is crucial for predicting the drop size in contact-drop dispensing. Unlike ideal surfaces on which contact lines are always free irrespective of surface wettability, contact lines may undergo transitions from pinned to free and vice versa during drop deposition on non-ideal surfaces. Here, we experimentally and theoretically examine how stability and breakup are affected by CAH, highlighting cases where stability is lost during a transition from a pinned-pinned (more constrained) to pinned-free (less constrained) interface-rather than a critical state. This provides a practical means of expediting or delaying stability loss. We also demonstrate how the dynamic contact angle can control the contact-line radius following stability loss. PMID:27443494

  12. Interfacial phenomena and dynamic contact angle modulation in microcapillary flows subjected to electroosmotic actuation.

    PubMed

    Chakraborty, Debapriya; Chakraborty, Suman

    2008-09-01

    The dynamic evolution of an incompressible liquid meniscus inside a microcapillary is investigated, under the combined influences of viscous, capillary, intermolecular, pondermotive, and electroosmotic effects. In the limit of small capillary numbers, an advancing meniscus shape is shown to merge smoothly with the precursor film, using matched asymptotic analysis. A scaling relationship is also established for the dynamic contact angle as a nondimensional function of the capillary number and the applied electrical voltage. The analysis is further generalized by invoking a kinetic slip model for overcoming the constraints of meniscus tip singularity. The kinetic slip model is subsequently utilized to analyze the interfacial dynamics from the perspective of the results obtained from the matched asymptotic analysis. A generalization is achieved in this regard, which may provide a sound basis for controlling the topographical features of a dynamically evolving meniscus in a microcapillary subjected to electrokinetic effects. These results are also in excellent agreement with the experimental findings over a wide range of capillary number values.

  13. Understanding properties of engineered catalyst supports using contact angle measurements and X-ray reflectivity.

    PubMed

    Amama, Placidus B; Islam, Ahmad E; Saber, Sammy M; Huffman, Daniel R; Maruyama, Benji

    2016-02-01

    There is significant interest in broadening the type of catalyst substrates that support the growth of high-quality carbon nanotube (CNT) carpets. In this study, ion beam bombardment has been utilized to modify catalyst substrates for CNT carpet growth. Using a combination of contact angle measurements (CAMs) and X-ray reflectivity (XRR) for the first time, new correlations between the physicochemical properties of pristine and engineered catalyst substrates and CNT growth behavior have been established. The engineered surfaces obtained after exposure to different degrees of ion beam damage have distinct physicochemical properties (porosity, layer thickness, and acid-base properties). The CAM data were analyzed using the van Oss-Chaudhury-Good model, enabling the determination of the acid-base properties of the substrate surfaces. For the XRR data, a Fourier analysis of the interference patterns enabled extraction of layer thickness, while the atomic density and interfacial roughness were extracted by analyzing the amplitude of the interference oscillations. The dramatic transformation of the substrate from "inactive" to "active" is attributed to a combined effect of substrate porosity or damage depth and Lewis basicity. The results reveal that the efficiency of catalyst substrates can be further improved by increasing the substrate basicity, if the minimum surface porosity is established. This study advances the use of a non-thermochemical approach for catalyst substrate engineering, as well as demonstrates the combined utility of CAM and XRR as a powerful, nondestructive, and reliable tool for rational catalyst design.

  14. Dependence of the Contact Angle on Self-Assembled Monolayer Production Method

    NASA Astrophysics Data System (ADS)

    Ollander, Brooke; Sayko, Ryan; Nutter, Jared; Petersen, Shannon; Poynor, Adele

    2015-03-01

    When water is forced in contact with a hydrophobic surface, it attempts to reduce its contact by forming a depletion layer. A depletion layer is defined as a nanometer scale low density region of water molecules at the surface. To alter the hydrophobicity of the slide, self-assembled monolayers (SAMs) are formed by utilizing the following organothiol solutions: 11-mercaptoundecanoic acid (hydrophilic) and 1-octadecanethiol (hydrophobic). The contact angle of slides with different organothiol solution exposure times is measured using a homemade goniometer and ImageJ software.

  15. On the physically based modeling of surface tension and moving contact lines with dynamic contact angles on the continuum scale

    NASA Astrophysics Data System (ADS)

    Huber, M.; Keller, F.; Säckel, W.; Hirschler, M.; Kunz, P.; Hassanizadeh, S. M.; Nieken, U.

    2016-04-01

    The description of wetting phenomena is a challenging problem on every considerable length-scale. The behavior of interfaces and contact lines on the continuum scale is caused by intermolecular interactions like the Van der Waals forces. Therefore, to describe surface tension and the resulting dynamics of interfaces and contact lines on the continuum scale, appropriate formulations must be developed. While the Continuum Surface Force (CSF) model is well-engineered for the description of interfaces, there is still a lack of treatment of contact lines, which are defined by the intersection of an ending fluid interface and a solid boundary surface. In our approach we use a balance equation for the contact line and extend the Navier-Stokes equations in analogy to the extension of a two-phase interface in the CSF model. Since this model depicts a physically motivated approach on the continuum scale, no fitting parameters are introduced and the deterministic description leads to a dynamical evolution of the system. As verification of our theory, we show a Smoothed Particle Hydrodynamics (SPH) model and simulate the evolution of droplet shapes and their corresponding contact angles.

  16. Low Voltage Electrowetting on Ferroelectric PVDF-HFP Insulator with Highly Tunable Contact Angle Range.

    PubMed

    Sawane, Yogesh B; Ogale, Satishchandra B; Banpurkar, Arun G

    2016-09-14

    We demonstrate a consistent electrowetting response on ferroelectric poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) insulator covered with a thin Teflon AF layer. This bilayer exhibits a factor of 3 enhancement in the contact angle modulation compared to that of conventional single-layered Teflon AF dielectric. On the basis of the proposed model the enhancement is attributed to the high value of effective dielectric constant (εeff ≈ 6) of the bilayer. Furthermore, the bilayer dielectric exhibits a hysteresis-free contact angle modulation over many AC voltage cycles. But the contact angle modulation for DC voltage shows a hysteresis because of the field-induced residual polarization in the ferroelectric layer. Finally, we show that a thin bilayer exhibits contact angle modulation of Δθ (U) ≈ 60° at merely 15 V amplitude of AC voltage indicating a potential dielectric for practical low voltage electrowetting applications. A proof of concept confirms electrowetting based rapid mixing of a fluorescent dye in aqueous glycerol solution for 15 V AC signal.

  17. On canonical cylinder sections for accurate determination of contact angle in microgravity

    SciTech Connect

    Concus, P.; Zabihi, F. California Univ., Berkeley, CA . Dept. of Mathematics); Finn, R. . Dept. of Mathematics)

    1992-07-01

    Large shifts of liquid arising from small changes in certain container shapes in zero gravity can be used as a basis for accurately determining contact angle. Canonical'' geometries for this purpose, recently developed mathematically, are investigated here computationally. It is found that the desired nearly- discontinuous'' behavior can be obtained and that the shifts of liquid have sufficient volume to be readily observed.

  18. On canonical cylinder sections for accurate determination of contact angle in microgravity

    SciTech Connect

    Concus, P.; Zabihi, F. |; Finn, R.

    1992-07-01

    Large shifts of liquid arising from small changes in certain container shapes in zero gravity can be used as a basis for accurately determining contact angle. ``Canonical`` geometries for this purpose, recently developed mathematically, are investigated here computationally. It is found that the desired ``nearly- discontinuous`` behavior can be obtained and that the shifts of liquid have sufficient volume to be readily observed.

  19. Low Voltage Electrowetting on Ferroelectric PVDF-HFP Insulator with Highly Tunable Contact Angle Range.

    PubMed

    Sawane, Yogesh B; Ogale, Satishchandra B; Banpurkar, Arun G

    2016-09-14

    We demonstrate a consistent electrowetting response on ferroelectric poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) insulator covered with a thin Teflon AF layer. This bilayer exhibits a factor of 3 enhancement in the contact angle modulation compared to that of conventional single-layered Teflon AF dielectric. On the basis of the proposed model the enhancement is attributed to the high value of effective dielectric constant (εeff ≈ 6) of the bilayer. Furthermore, the bilayer dielectric exhibits a hysteresis-free contact angle modulation over many AC voltage cycles. But the contact angle modulation for DC voltage shows a hysteresis because of the field-induced residual polarization in the ferroelectric layer. Finally, we show that a thin bilayer exhibits contact angle modulation of Δθ (U) ≈ 60° at merely 15 V amplitude of AC voltage indicating a potential dielectric for practical low voltage electrowetting applications. A proof of concept confirms electrowetting based rapid mixing of a fluorescent dye in aqueous glycerol solution for 15 V AC signal. PMID:27553685

  20. Contact angle and detachment energy of shape anisotropic particles at fluid-fluid interfaces.

    PubMed

    Anjali, Thriveni G; Basavaraj, Madivala G

    2016-09-15

    The three phase contact angle of particles, a measure of its wettability, is an important factor that greatly influences their behaviour at interfaces. It is one of the principal design parameters for potential applications of particles as emulsion/foam stabilizers, functional coatings and other novel materials. In the present work, the effect of size, shape and surface chemistry of particles on their contact angle is investigated using the gel trapping technique, which facilitates the direct visualization of the equilibrium position of particles at interfaces. The contact angle of hematite particles of spherocylindrical, peanut and cuboidal shapes, hematite-silica core-shell and silica shells is reported at a single particle level. The spherocylindrical and peanut shaped particles are always positioned with their major axis parallel to the interface. However, for cuboidal particles at air-water as well as decane-water interfaces, different orientations namely - face-up, edge-up and the vertex-up - are observed. The influence of gravity on the equilibrium position of the colloidal particles at the interface is studied using the hematite-silica core-shell particles and the silica shells. The measured contact angle values are utilized in the calculations of the detachment and surface energies of the hematite particles adsorbed at the interface.

  1. Tuning the Receding Contact Angle on Hydrogels by Addition of Particles.

    PubMed

    Boulogne, François; Ingremeau, François; Limat, Laurent; Stone, Howard A

    2016-06-01

    Control of the swelling, chemical functionalization, and adhesivity of hydrogels are finding new applications in a wide range of material systems. We investigate experimentally the effect of adsorbed particles on hydrogels on the depinning of contact lines. In our experiments, a water drop containing polystyrene microspheres is deposited on a swelling hydrogel, which leads to the drop absorption and particle deposition. Two regimes are observed: a decreasing drop height with a pinned contact line followed by a receding contact line. We show that increasing the particles concentration increases the duration of the first regime and significantly decreases the total absorption time. The adsorbed particles increase the pinning force at the contact line. Finally, we develop a method to measure the receding contact angle with the consideration of the hydrogel swelling. PMID:27185647

  2. Effective Darcy-Scale Contact Angles in Porous Media Imbibing Solutions of Various Surface Tensions

    SciTech Connect

    Weisbrod, Noam; McGinnis, Thomas; Rockhold, Mark L.; Niemet, Mike; Selker, John S.

    2009-10-17

    Surface tensions of high-salinity solutions are significantly different from those of pure water. Our objective was to develop and test a methodology to determine whether these surface-tension effects predictably alter imbibition into dry and moist porous media. Static and dynamic experiments were performed using four grades of quartz sand to determine the effects of solution salinity on imbibition. Results were quantified as apparent contact angles between the sand and three solutions (pure water, 5 molal NaNO3, n-hexane). Contact angles determined using a static method in initially air-dried sand ranged from 23° to 31°, with the same values found for both water and the NaNO3 solution. Effective contact angles determined for the air-dried sand using a dynamic method based on a modified version of the Green and Ampt model were about twice those found using the static method, averaging 45° and 62° for water and the NaNO3 solution, respectively. In pre-wetted sands, the dynamic imbibition data yielded apparent contact angles of 2° and 21° for water and the NaNO3 solution, respectively, with the latter value comparing well to a predicted value of 25° for the NaNO3 solution based solely on surface-tension contrast. The results of this study indicate that on the Darcy-scale, saline solutions appear to follow the relationship of non-zero contact angles with other miscible fluids of different surface tensions used to pre-wet the sand grains, in agreement with the macro-scale infiltration results of Weisbrod et al. [2004].

  3. Prediction of contact angle for hydrophobic surface fabricated with micro-machining based on minimum Gibbs free energy

    NASA Astrophysics Data System (ADS)

    Zhenyu, Shi; Zhanqiang, Liu; Hao, Song; Xianzhi, Zhang

    2016-02-01

    When an interface exists between a liquid and a solid, the angle between the surface of the liquid and the outline of the contact surface is described as the contact angle. The size of the contact angle is the metrics of the hydrophobicity of the surface. The prediction of the contact angle has significant effect on the design of hydrophobic surface and improvement of hydrophobicity. In this paper, a prediction model for contact angle has been proposed based on minimum Gibbs free energy. It considers the effects of unilateral force and area constraints of the droplets. The effect of micro-structural parameters on contact angle has also been investigated. Micro-milling experiments have been conducted to fabricate the hydrophobic surface in order to validate the predictive capability of the contact angle model. Results revealed that the established prediction model could estimate the contact angle of hydrophobic surface. The contact angle could be increased by increasing concave width or reducing convex. The outcome of this research will lead to new methodologies for preparing hydrophobic surfaces with micro-machining technology.

  4. Stokes flow inside an evaporating liquid line for any contact angle

    NASA Astrophysics Data System (ADS)

    Petsi, A. J.; Burganos, V. N.

    2008-09-01

    Evaporation of droplets or liquid films lying on a substrate induces internal viscous flow, which affects the transport of suspended particles and, thus, the final deposit profile in numerous applications. In this work, the problem of Stokes flow inside a two-dimensional droplet, representing the cross section of an evaporating liquid line lying on a flat surface, is considered. The stream function formulation is adopted, leading to the biharmonic equation in bipolar coordinates. A solution in closed form is obtained for any contact angle in (0,π) and is, thus, valid for both hydrophilic and hydrophobic substrates. The solution can be used with any type of evaporation mechanism, including diffusion, convection, or kinetically controlled modes. Both pinned and depinned contact lines are considered. For the boundary conditions to be compatible at the contact lines, the Navier slip boundary condition is applied on the substrate. Numerical results are presented for kinetically and diffusion controlled evaporation. For pinned contact lines, the flow inside the evaporating liquid line is directed towards the edges, thus, promoting the coffee stain phenomenon. In the case of depinned contact lines and contact angle less than π/2 , the flow is directed towards the center of the droplet, whereas, for strongly hydrophobic substrates it is directed outwards.

  5. Investigation of Contact Angle Behavior and Stability of Drops to Airflow Forcing on Rough Surfaces

    NASA Astrophysics Data System (ADS)

    Schmucker, Jason; White, Edward

    2011-11-01

    A method for measuring full-field, instantaneous drop interface profiles on rough surfaces has been implemented to study contact angles and stability to wind forcing on metallic surfaces with micron-scale roughness. Wind tunnel experiments are conducted to produce criteria for runback of drops and set these thresholds for measured water drops spanning a range of Bond numbers from Bo = 0 . 5 to 5 on roughness in the range of RA = 0 . 8 to 4 . 9 with drop based Reynolds numbers spanning an order of magnitude. More importantly, these stability limits are tested with particular care taken to observe their relation to the behavior of both the contact line and contact angle distribution as the drop adjusts its configuration to find a stable condition until it is no longer able to do so and is blown downstream. Results such as critical shear rates and contact angles are discussed and compared with previous numerical studies in the literature such as Dimitrakopoulos [J.Fluid.Mech. 580, 2007] and Ding and Spelt [J.Coll.Sci. 599, 2008] along with experimental results such as Milne [Langmuir 25:24, 2009].

  6. Investigations for an alternative to contact angle measurement after Hexamethyldisilazane deposition

    NASA Astrophysics Data System (ADS)

    Aßmann, H.; Krause, A.; Maurer, R.; Dankelmann, M.; Specht, M.; Usry, W.; Newcomb, R.

    2015-09-01

    The adhesion promoter Hexamethyldisilazane (HMDS) plays a crucial role in i-line lithography. According to HMDS deposition forms, a hydrophobic surface defines upwardly directed, non-polar trimethysilyl groups. This condition is of particular importance for wet chemical development and subsequent wet chemical etching processes, because the defined hydrophobic surface prevents water from creeping beneath the resist mask. Undesirable effects, such as (partial) loss of the resist structure or under etching can be prevented. Currently, a common and suitable method to control the success of HMDS deposition is the contact angle measurement. There, a drop of water is applied to the substrate and the contact angle / wetting angle is measured. As a result, conclusions can be drawn about the HMDS process. Unfortunately, however, this simple to implement measurement method raises some problems. The measurement is extremely dependent on the substrate, wherein the measurement results vary greatly. A possible reason for this is the different surface properties of the wafers which are due to adsorbate films. Typically, a contact angle measurement is performed just after the HMDS deposition. A difference between pre- and post-measurement cannot be determined. A deviation of the contact angle can be caused by either an insufficient HMDS seeding, or just as well by other, unknown surface properties. The studies presented here were performed with the measuring system ChemetriQ 5000 from Qcept Technologies. This measurement system was originally developed for Inspection on non-visible defects on the wafer level. It is able to detect differences of work functions as a result of surface coverage by thin film / adsorbate, materials or residues. The change in the surface work function due to the generated adsorbate layer during the HMDS deposition is determined by the measuring system by means of a difference between pre- and post-measurement.

  7. An analytical solution for a partially wetting puddle and the location of the static contact angle.

    PubMed

    Elena Diaz, M; Fuentes, Javier; Cerro, Ramon L; Savage, Michael D

    2010-08-01

    A model is formulated for a static puddle on a horizontal substrate taking account of capillarity, gravity and disjoining pressure arising from molecular interactions. There are three regions of interest--the molecular, transition and capillary regions with characteristic film thickness, hm, ht and hc. An analytical solution is presented for the shape of the vapour-liquid interface outside the molecular region where interfacial tension can be assumed constant. This solution is used to shed new light on the static contact angle and, specifically, it is shown that. (i) There is no point in the vapour-liquid interface where the angle of inclination, theta, is identically equal to the static contact angle, theta(o), but the angle at the point of null curvature is the closest with the difference of O(epsilon2) where epsilon2 = ht/hc is a small parameter. (ii) The liquid film is to O(epsilon) a wedge of angle theta(o) extending from a few nanometers to a few micrometers of the contact line. A second analytical solution for the shape of interface within the molecular region reveals that cos theta has a logarithmic variation with film thickness, cos theta=cos theta-ln[1-h2(m)/2h2]. The case, hm = 0, is of special significance since it refers to a unique configuration in which the effect of molecular interactions vanishes, disjoining pressure is everywhere zero and the vapour-liquid interface is now described exactly by the Young-Laplace equation and includes a wedge of angle, theta(o), extending down to the solid substrate.

  8. Relationship Between Hand Contact Angle and Shoulder Loading During Manual Wheelchair Propulsion by Individuals with Paraplegia

    PubMed Central

    Mulroy, Sara J.; Ruparel, Puja; Hatchett, Patricia E.; Haubert, Lisa Lighthall; Eberly, Valerie J.; Gronley, JoAnne K.

    2015-01-01

    Background: Shoulder loading during manual wheelchair propulsion (WCP) contributes to the development of shoulder pain in individuals with spinal cord injury (SCI). Objective: To use regression analysis to investigate the relationships between the hand contact angle (location of the hand on the pushrim at initial contact and release during the push phase of the WCP cycle) with propulsion characteristics, pushrim forces, and shoulder kinetics during WCP in individuals with paraplegia. Methods: Biomechanical data were collected from 222 individuals (198 men and 24 women) with paraplegia from SCI during WCP on a stationary ergometer at a self-selected speed. The average age of participants was 34.7 years (±9.3), mean time since SCI was 9.3 years (±6.1), and average body weight was 74.4 kg (±15.9). The majority (n = 127; 56%) of participants had lower level paraplegia (T8 to L5) and 95 (42%) had high paraplegia (T2 to T7). Results: Increased push arc (mean = 75.3°) was associated with greater velocity (R = 0.384, P < .001) and cycle distance (R = 0.658, P < .001) and reduced cadence (R = -0.419, P < .001). Initial contact angle and hand release angles were equally associated with cycle distance and cadence, whereas a more anterior release angle was associated with greater velocity (R = 0.372, P < .001). When controlling for body weight, a more posterior initial contact angle was associated with greater posterior shoulder net joint force (R = 0.229, P = .001) and greater flexor net joint moment (R = 0.204, P = .002), whereas a more anterior hand release angle was significantly associated with increased vertical (R = 0.270, P < .001) and greater lateral (R = .293, P < .001) pushrim forces; greater shoulder net joint forces in all 3 planes — posterior (R = 0.164, P = .015), superior (R = 0.176, P = .009), and medial (R = 0.284, P < .001); and greater external rotator (R = 0.176, P = .009) and adductor (R = 0.259, P = .001) net joint moments. Conclusions: Current

  9. Non-contact angle measurement based on parallel multiplex laser feedback interferometry

    NASA Astrophysics Data System (ADS)

    Zhang, Song; Tan, Yi-Dong; Zhang, Shu-Lian

    2014-11-01

    We present a novel precise angle measurement scheme based on parallel multiplex laser feedback interferometry (PLFI), which outputs two parallel laser beams and thus their displacement difference reflects the angle variation of the target. Due to its ultrahigh sensitivity to the feedback light, PLFI realizes the direct non-contact measurement of non-cooperative targets. Experimental results show that PLFI has an accuracy of 8″ within a range of 1400″. The yaw of a guide is also measured and the experimental results agree with those of the dual-frequency laser interferometer Agilent 5529A.

  10. Understanding properties of engineered catalyst supports using contact angle measurements and X-Ray reflectivity

    NASA Astrophysics Data System (ADS)

    Amama, Placidus B.; Islam, Ahmad E.; Saber, Sammy M.; Huffman, Daniel R.; Maruyama, Benji

    2016-01-01

    There is significant interest in broadening the type of catalyst substrates that support the growth of high-quality carbon nanotube (CNT) carpets. In this study, ion beam bombardment has been utilized to modify catalyst substrates for CNT carpet growth. Using a combination of contact angle measurements (CAMs) and X-ray reflectivity (XRR) for the first time, new correlations between the physicochemical properties of pristine and engineered catalyst substrates and CNT growth behavior have been established. The engineered surfaces obtained after exposure to different degrees of ion beam damage have distinct physicochemical properties (porosity, layer thickness, and acid-base properties). The CAM data were analyzed using the van Oss-Chaudhury-Good model, enabling the determination of the acid-base properties of the substrate surfaces. For the XRR data, a Fourier analysis of the interference patterns enabled extraction of layer thickness, while the atomic density and interfacial roughness were extracted by analyzing the amplitude of the interference oscillations. The dramatic transformation of the substrate from ``inactive'' to ``active'' is attributed to a combined effect of substrate porosity or damage depth and Lewis basicity. The results reveal that the efficiency of catalyst substrates can be further improved by increasing the substrate basicity, if the minimum surface porosity is established. This study advances the use of a non-thermochemical approach for catalyst substrate engineering, as well as demonstrates the combined utility of CAM and XRR as a powerful, nondestructive, and reliable tool for rational catalyst design.There is significant interest in broadening the type of catalyst substrates that support the growth of high-quality carbon nanotube (CNT) carpets. In this study, ion beam bombardment has been utilized to modify catalyst substrates for CNT carpet growth. Using a combination of contact angle measurements (CAMs) and X-ray reflectivity (XRR) for the

  11. Contact Angle of Drops Measured on Nontransparent Surfaces and Capillary Flow Visualized

    NASA Technical Reports Server (NTRS)

    Chao, David F.; Zhang, Nengli

    2003-01-01

    The spreading of a liquid on a solid surface is important for various practical processes, and contact-angle measurements provide an elegant method to characterize the interfacial properties of the liquid with the solid substrates. The complex physical processes occurring when a liquid contacts a solid play an important role in determining the performance of chemical processes and materials. Applications for these processes are in printing, coating, gluing, textile dyeing, and adhesives and in the pharmaceutical industry, biomedical research, adhesives, flat panel display manufacturing, surfactant chemistry, and thermal engineering.

  12. Contact angle measurements of a polyphenyl ether to 190 C on M-50 steel

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.

    1981-01-01

    Contact angle measurements were performed for a polyphenyl ether on steel in nitrogen. A tilting plate and a sessile drop apparatus were used. Surface tension was measured with a maximum bubble pressure apparatus. Critical surface energies of spreading were found to be 30.1 and 31.3 dynes/cm. It was concluded that the polyphenyl ether is inherently autophobic and will not spread on its own surface film.

  13. Contact angles and wetting behaviour of single micron-sized particles

    NASA Astrophysics Data System (ADS)

    Gillies, Graeme; Büscher, Karsten; Preuss, Markus; Kappl, Michael; Butt, Hans-Jürgen; Graf, Karlheinz

    2005-03-01

    A 'particle interaction apparatus' based on the technique of atomic force microscopy was constructed that allows us to measure the interaction between single micron-sized particles and the air-water interface. From the force versus distance profiles ('force curves') the contact angle of single microspheres could be determined. This new method for microsphere tensiometry was validated using a variety of materials with contact angles between 20° and 90°. Contact angles measured on single microspheres correlated well with those measured on flat substrates of the same materials. The interaction of single silica microspheres with an air bubble in the presence of surfactants (SDS and DTAB) was investigated. Depending on surfactant type and concentration, adhesion or repulsion could be induced. Adhesion forces were found to depend on the applied load, indicating possible adsorption/desorption processes at the particle-bubble interface. We have built a new set-up that combines a particle interaction apparatus with a Langmuir trough and a fluorescence microscope. This will allow study of interactions at the air-water interface in more detail, especially in the presence of a definite surface density of amphiphilic molecules. The interaction of single ZnS spheres with a bubble (modelling flotation of ZnS) was studied at different pH values. The results suggest that the isoelectric point of these spheres exists between pH 7 and 8.

  14. Use of Atomic Oxygen for Increased Water Contact Angles of Various Polymers for Biomedical Applications

    NASA Technical Reports Server (NTRS)

    Beger, Lauren; Roberts, Lily; deGroh, Kim; Banks, Bruce

    2007-01-01

    In the low Earth orbit (LEO) space environment, spacecraft surfaces can be altered during atomic oxygen exposure through oxidation and erosion. There can be terrestrial benefits of such interactions, such as the modification of hydrophobic or hydrophilic properties of polymers due to chemical modification and texturing. Such modification of the surface may be useful for biomedical applications. For example, atomic oxygen texturing may increase the hydrophilicity of polymers, such as chlorotrifluoroethylene (Aclar), thus allowing increased adhesion and spreading of cells on textured Petri dishes. The purpose of this study was to determine the effect of atomic oxygen exposure on the hydrophilicity of nine different polymers. To determine whether hydrophilicity remains static after atomic oxygen exposure or changes with exposure, the contact angles between the polymer and a water droplet placed on the polymer s surface were measured. The polymers were exposed to atomic oxygen in a radio frequency (RF) plasma asher. Atomic oxygen plasma treatment was found to significantly alter the hydrophilicity of non-fluorinated polymers. Significant decreases in the water contact angle occurred with atomic oxygen exposure. Fluorinated polymers were found to be less sensitive to changes in hydrophilicity for equivalent atomic oxygen exposures, and two of the fluorinated polymers became more hydrophobic. The majority of change in water contact angle of the non-fluorinated polymers was found to occur with very low fluence exposures, indicating potential cell culturing benefit with short treatment time.

  15. Changes in contact angle providing evidence for surface alteration in multi-component solid foods

    NASA Astrophysics Data System (ADS)

    Reinke, Svenja K.; Hauf, Katharina; Vieira, Josélio; Heinrich, Stefan; Palzer, Stefan

    2015-11-01

    Chocolate blooming, one of the major problems in the confectionery industry, is the formation of visible white spots or a greyish haze on the surface of chocolate products due to large sugar or fat crystals on the surface. This leads to aesthetic changes and deterioration of taste and thus large sales losses for the confectionery industry due to consumer complaints. Chocolate blooming is often related to migration of lipids or sugar molecules to the chocolate surface, where they recrystallize with an associated polymorphic change of crystal structure on the surface. The wetting behaviour from contact angle measurements gives further insight into surface properties and is needed to determine surface energies and to evaluate possible migration mechanisms and preferred pathways. Therefore, an equilibrium contact angle is needed which is not directly accessible and is influenced by surface texture and interaction between solid and test liquid. In this study, the surface of cocoa butter and conventional chocolates was characterized by measuring the contact angle with the sessile drop protocol. The influence of roughness, test liquid and pre-crystallization of the samples as well as the storage temperature were investigated. In case of no pre-crystallization, a change in surface properties due to storage at 20 °C was detected, whereas samples stored at 30 °C showed the same wetting behaviour as fresh samples. This is associated with polymorphic transformation from thermodynamically less stable crystals to more stable configurations.

  16. Calculation of contact angles at triple phase boundary in solid oxide fuel cell anode using the level set method

    SciTech Connect

    Sun, Xiaojun; Hasegawa, Yosuke; Kohno, Haruhiko; Jiao, Zhenjun; Hayakawa, Koji; Okita, Kohei; Shikazono, Naoki

    2014-10-15

    A level set method is applied to characterize the three dimensional structures of nickel, yttria stabilized zirconia and pore phases in solid oxide fuel cell anode reconstructed by focused ion beam-scanning electron microscope. A numerical algorithm is developed to evaluate the contact angles at the triple phase boundary based on interfacial normal vectors which can be calculated from the signed distance functions defined for each of the three phases. Furthermore, surface tension force is estimated from the contact angles by assuming the interfacial force balance at the triple phase boundary. The average contact angle values of nickel, yttria stabilized zirconia and pore are found to be 143°–156°, 83°–138° and 82°–123°, respectively. The mean contact angles remained nearly unchanged after 100 hour operation. However, the contact angles just after reduction are different for the cells with different sintering temperatures. In addition, standard deviations of the contact angles are very large especially for yttria stabilized zirconia and pore phases. The calculated surface tension forces from mean contact angles were close to the experimental values found in the literature. Slight increase of surface tensions of nickel/pore and nickel/yttria stabilized zirconia were observed after operation. Present data are expected to be used not only for the understanding of the degradation mechanism, but also for the quantitative prediction of the microstructural temporal evolution of solid oxide fuel cell anode. - Highlights: • A level set method is applied to characterize the 3D structures of SOFC anode. • A numerical algorithm is developed to evaluate the contact angles at the TPB. • Surface tension force is estimated from the contact angles. • The average contact angle values are found to be 143o-156o, 83o-138o and 82o-123o. • Present data are expected to understand degradation and predict evolution of SOFC.

  17. Thin three-dimensional droplets on an oscillating substrate with contact angle hysteresis

    NASA Astrophysics Data System (ADS)

    Bradshaw, J.; Billingham, J.

    2016-01-01

    Recent experiments [P. Brunet, J. Eggers, and R. D. Deegan, Phys. Rev. Lett. 99, 144501 (2007), 10.1103/PhysRevLett.99.144501] have shown that a liquid droplet on an inclined plane can be made to move uphill by sufficiently strong, vertical oscillations. In order to investigate this counterintuitive phenomenon we use a model in which liquid inertia and viscosity are assumed negligible so that the motion of the droplet is dominated by the applied acceleration due to the oscillation of the plate, gravity, and surface tension. We explain how the leading order motion of the droplet can be separated into a spreading mode and a swaying mode. For a linear contact line law, the maximum rise velocity occurs when these modes are in phase. We show that, both with and without contact angle hysteresis, the droplet can climb uphill and also that, for certain contact line laws, the motion of the droplet can produce footprints similar to experimental results. We show that if the two modes are out of phase when there is no contact angle hysteresis, the inclusion of hysteresis can force them into phase. This in turn increases the rise velocity of the droplet and can, in some cases, cause a sliding droplet to climb.

  18. Thin three-dimensional droplets on an oscillating substrate with contact angle hysteresis.

    PubMed

    Bradshaw, J; Billingham, J

    2016-01-01

    Recent experiments [P. Brunet, J. Eggers, and R. D. Deegan, Phys. Rev. Lett. 99, 144501 (2007)10.1103/PhysRevLett.99.144501] have shown that a liquid droplet on an inclined plane can be made to move uphill by sufficiently strong, vertical oscillations. In order to investigate this counterintuitive phenomenon we use a model in which liquid inertia and viscosity are assumed negligible so that the motion of the droplet is dominated by the applied acceleration due to the oscillation of the plate, gravity, and surface tension. We explain how the leading order motion of the droplet can be separated into a spreading mode and a swaying mode. For a linear contact line law, the maximum rise velocity occurs when these modes are in phase. We show that, both with and without contact angle hysteresis, the droplet can climb uphill and also that, for certain contact line laws, the motion of the droplet can produce footprints similar to experimental results. We show that if the two modes are out of phase when there is no contact angle hysteresis, the inclusion of hysteresis can force them into phase. This in turn increases the rise velocity of the droplet and can, in some cases, cause a sliding droplet to climb. PMID:26871170

  19. Thin three-dimensional droplets on an oscillating substrate with contact angle hysteresis.

    PubMed

    Bradshaw, J; Billingham, J

    2016-01-01

    Recent experiments [P. Brunet, J. Eggers, and R. D. Deegan, Phys. Rev. Lett. 99, 144501 (2007)10.1103/PhysRevLett.99.144501] have shown that a liquid droplet on an inclined plane can be made to move uphill by sufficiently strong, vertical oscillations. In order to investigate this counterintuitive phenomenon we use a model in which liquid inertia and viscosity are assumed negligible so that the motion of the droplet is dominated by the applied acceleration due to the oscillation of the plate, gravity, and surface tension. We explain how the leading order motion of the droplet can be separated into a spreading mode and a swaying mode. For a linear contact line law, the maximum rise velocity occurs when these modes are in phase. We show that, both with and without contact angle hysteresis, the droplet can climb uphill and also that, for certain contact line laws, the motion of the droplet can produce footprints similar to experimental results. We show that if the two modes are out of phase when there is no contact angle hysteresis, the inclusion of hysteresis can force them into phase. This in turn increases the rise velocity of the droplet and can, in some cases, cause a sliding droplet to climb.

  20. Different contact angle distributions for heterogeneous ice nucleation in the Community Atmospheric Model version 5

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Liu, X.; Hoose, C.; Wang, B.

    2014-10-01

    In order to investigate the impact of different treatments for the contact angle (α) in heterogeneous ice nucleating properties of natural dust and black carbon (BC) particles, we implement the classical-nucleation-theory-based parameterization of heterogeneous ice nucleation (Hoose et al., 2010) in the Community Atmospheric Model version 5 (CAM5) and then improve it by replacing the original single-contact-angle model with the probability-density-function-of-α (α-PDF) model to better represent the ice nucleation behavior of natural dust found in observations. We refit the classical nucleation theory (CNT) to constrain the uncertain parameters (i.e., onset α and activation energy in the single-α model; mean contact angle and standard deviation in the α-PDF model) using recent observation data sets for Saharan natural dust and BC (soot). We investigate the impact of the time dependence of droplet freezing on mixed-phase clouds and climate in CAM5 as well as the roles of natural dust and soot in different nucleation mechanisms. Our results show that, when compared with observations, the potential ice nuclei (IN) calculated by the α-PDF model show better agreement than those calculated by the single-α model at warm temperatures (T; T > -20 °C). More ice crystals can form at low altitudes (with warm temperatures) simulated by the α-PDF model than compared to the single-α model in CAM5. All of these can be attributed to different ice nucleation efficiencies among aerosol particles, with some particles having smaller contact angles (higher efficiencies) in the α-PDF model. In the sensitivity tests with the α-PDF model, we find that the change in mean contact angle has a larger impact on the active fraction at a given temperature than a change in standard deviation, even though the change in standard deviation can lead to a change in freezing behavior. Both the single-α and the α-PDF model indicate that the immersion freezing of natural dust plays a more

  1. Asymmetric and speed-dependent contact angle hysteresis and relaxation of a suddenly stopped moving contact line

    NASA Astrophysics Data System (ADS)

    Guan, Dongshi; Wang, Yong Jian; Charlaix, Elisabeth; Tong, Penger

    We report direct atomic-force-microscope measurements of capillary force hysteresis and relaxation of a circular moving contact line (CL) formed on a long micron-sized hydrophobic fiber intersecting a water-air interface. The measured capillary force hysteresis and CL relaxation show a strong asymmetric speed dependence in the advancing and receding directions. A unified model based on force-assisted barrier-crossing is utilized to find the underlying energy barrier Eb and size λ associated with the defects on the fiber surface. The experiment demonstrates that the pinning (relaxation) and depinning dynamics of the CL can be described by a common microscopic frame-work, and the advancing and receding CLs are influenced by two different sets of relatively wetting and non-wetting defects on the fiber surface. Work supported in part by the Research Grants Council of Hong Kong SAR.

  2. Effect of tibial tuberosity advancement on femorotibial contact mechanics and stifle kinematics.

    PubMed

    Kim, Stanley E; Pozzi, Antonio; Banks, Scott A; Conrad, Bryan P; Lewis, Daniel D

    2009-01-01

    Objective- To evaluate the effects of tibial tuberosity advancement (TTA) on femorotibial contact mechanics and 3-dimensional kinematics in cranial cruciate ligament (CrCL)-deficient stifles of dogs. Study Design- In vitro biomechanical study. Animals- Unpaired pelvic limbs from 8 dogs, weighing 28-35 kg. Methods- Digital pressure sensors placed subjacent to the menisci were used to measure femorotibial contact force, contact area, peak and mean contact pressure, and peak pressure location with the limb under an axial load of 30% body weight and a stifle angle of 135 degrees . Three-dimensional static poses of the stifle were obtained using a Microscribe digitizing arm. Each specimen was tested under normal, CrCL-deficient, and TTA-treated conditions. Repeated measures analysis of variance with a Tukey post hoc test (P<.05) was used for statistical comparison. Results- Significant disturbances to all measured contact mechanic parameters were evident after CrCL transection, which corresponded to marked cranial tibial subluxation and internal tibial rotation in the CrCL-deficient stifle. No significant differences in any contact mechanic and kinematic parameters were detected between normal and TTA-treated stifles. Conclusion- TTA eliminates craniocaudal stifle instability during simulated weight-bearing and concurrently restores femorotibial contact mechanics to normal. Clinical Relevance- TTA may mitigate the progression of stifle osteoarthritis in dogs afflicted with CrCL insufficiency by eliminating cranial tibial thrust while preserving the normal orientation of the proximal tibial articulating surface.

  3. Is a Knowledge of Surface Topology and Contact Angles Enough to Define the Drop Impact Outcome?

    PubMed

    Malavasi, Ileana; Veronesi, Federico; Caldarelli, Aurora; Zani, Maurizio; Raimondo, Mariarosa; Marengo, Marco

    2016-06-28

    It is well known that a superhydrophobic surface may not be able to repel impacting droplets because of the so-called Cassie-to-Wenzel transition. It has been proven that a critical value of the receding contact angle (θR) exists for the complete rebound of water, recently experimentally measured to be 100° for a large range of impact velocities. On the contrary, in the present work, no rebound was observed when low-surface-tension liquids such as hexadecane (σ = 27.5 mN/m at 25 °C) are concerned, even for very low impact velocities and very high values of θR and low contact angle hysteresis. Therefore, the critical threshold of θR ≈ 100° does not sound acceptable for all liquids and for all hydrophobic surfaces. For the same Weber numbers, a Cassie-to-Wenzel state transition occurs after the impact as a result of the easier penetration of low-surface-tension fluids in the surface structure. Hence, a criterion for the drop rebound of low-surface-tension liquids must consider not only the contact angle values with surfaces but also their surface tension and viscosity. This suggests that, even if it is possible to produce surfaces with enhanced static repellence against oils and organics, generally the realization of synthetic materials with self-cleaning and antisticking abilities in dynamic phenomena, such as spray impact, remains an unsolved task. Moreover, it is demonstrated that the chemistry of the surface, the physicochemical interactions with the liquid drops, and the possible wettability gradient of the surface asperity also play important roles in determining the critical Weber number above which impalement occurs. Therefore, the classical numerical simulations of drop impact on dry surfaces are definitively not able to capture the final outcomes of the impact for all possible fluids if the surface topology and chemistry and/or the wettability gradient in the surface structure are not properly reflected.

  4. Particle contact angles at fluid interfaces: pushing the boundary beyond hard uniform spherical colloids

    NASA Astrophysics Data System (ADS)

    Zanini, Michele; Isa, Lucio

    2016-08-01

    Micro and nanoparticles at fluid interfaces have been attracting increasing interest in the last few decades as building blocks for materials, as mechanical and structural probes for complex interfaces and as models for two-dimensional systems. The three-phase contact angle enters practically all aspects of the particle behavior at the interface: its thermodynamics (binding energy to the interface), dynamics (motion and drag at the interface) and interactions with the interface (adsorption and wetting). Moreover, many interactions among particles at the interface also strongly depend on the contact angle. These concepts have been extensively discussed for non-deformable, homogeneous and mostly spherical particles, but recent progress in particle synthesis and fabrication has instead moved in the direction of producing more complex micro and nanoscale objects, which can be responsive, deformable, heterogenous and/or anisotropic in shape, surface chemistry and material properties. These new particles have a much greater potential for applications and new science, and the study of their behavior at interfaces has only very recently started. In this paper, we critically review the current state of the art of the experimental methods available to measure the contact angle of micro and nanoparticles at fluid interfaces, indicating their strengths and limitations. We then comment on new particle systems that are currently attracting increasing interest in relation to their adsorption and assembly at fluid interfaces and discuss if and which ones of the current techniques are suited to investigate their properties at interfaces. Based on this discussion, we will finally try to indicate a direction in which new experimental methods should develop in the future to tackle the new challenges posed by the novel types of particles that more and more often are used at interfaces.

  5. Particle contact angles at fluid interfaces: pushing the boundary beyond hard uniform spherical colloids.

    PubMed

    Zanini, Michele; Isa, Lucio

    2016-08-10

    Micro and nanoparticles at fluid interfaces have been attracting increasing interest in the last few decades as building blocks for materials, as mechanical and structural probes for complex interfaces and as models for two-dimensional systems. The three-phase contact angle enters practically all aspects of the particle behavior at the interface: its thermodynamics (binding energy to the interface), dynamics (motion and drag at the interface) and interactions with the interface (adsorption and wetting). Moreover, many interactions among particles at the interface also strongly depend on the contact angle. These concepts have been extensively discussed for non-deformable, homogeneous and mostly spherical particles, but recent progress in particle synthesis and fabrication has instead moved in the direction of producing more complex micro and nanoscale objects, which can be responsive, deformable, heterogenous and/or anisotropic in shape, surface chemistry and material properties. These new particles have a much greater potential for applications and new science, and the study of their behavior at interfaces has only very recently started. In this paper, we critically review the current state of the art of the experimental methods available to measure the contact angle of micro and nanoparticles at fluid interfaces, indicating their strengths and limitations. We then comment on new particle systems that are currently attracting increasing interest in relation to their adsorption and assembly at fluid interfaces and discuss if and which ones of the current techniques are suited to investigate their properties at interfaces. Based on this discussion, we will finally try to indicate a direction in which new experimental methods should develop in the future to tackle the new challenges posed by the novel types of particles that more and more often are used at interfaces. PMID:27299800

  6. Particle contact angles at fluid interfaces: pushing the boundary beyond hard uniform spherical colloids.

    PubMed

    Zanini, Michele; Isa, Lucio

    2016-08-10

    Micro and nanoparticles at fluid interfaces have been attracting increasing interest in the last few decades as building blocks for materials, as mechanical and structural probes for complex interfaces and as models for two-dimensional systems. The three-phase contact angle enters practically all aspects of the particle behavior at the interface: its thermodynamics (binding energy to the interface), dynamics (motion and drag at the interface) and interactions with the interface (adsorption and wetting). Moreover, many interactions among particles at the interface also strongly depend on the contact angle. These concepts have been extensively discussed for non-deformable, homogeneous and mostly spherical particles, but recent progress in particle synthesis and fabrication has instead moved in the direction of producing more complex micro and nanoscale objects, which can be responsive, deformable, heterogenous and/or anisotropic in shape, surface chemistry and material properties. These new particles have a much greater potential for applications and new science, and the study of their behavior at interfaces has only very recently started. In this paper, we critically review the current state of the art of the experimental methods available to measure the contact angle of micro and nanoparticles at fluid interfaces, indicating their strengths and limitations. We then comment on new particle systems that are currently attracting increasing interest in relation to their adsorption and assembly at fluid interfaces and discuss if and which ones of the current techniques are suited to investigate their properties at interfaces. Based on this discussion, we will finally try to indicate a direction in which new experimental methods should develop in the future to tackle the new challenges posed by the novel types of particles that more and more often are used at interfaces.

  7. Investigation of the surface of implanted silicon crystal by the contact angle

    SciTech Connect

    Lebedeva, N.N.; Bakovets, V.V.; Sedymova, E.A.; Pridachin, N.B.

    1987-03-01

    The authors study the dependence of the critical contact angle of silicon upon the dose of its irradiation by argon and boron ions. It is established that the system of immiscible liquids ether-water can be successfully used to study the influence of ion implantation of silicon on its wettability by water. The change in the wettability of implanted silicon is related to the increase in the level of the defect state of the layer surface. Wetting of implanted silicon by melts at high temperatures can be used for studying the kinetics and the annealing mechanism of defects.

  8. Enhancing Condensers for Geothermal Systems: the Effect of High Contact Angles on Dropwise Condensation Heat Transfer

    SciTech Connect

    Kennedy, John M.; Kim, Sunwoo; Kim, Kwang J.

    2009-10-06

    Phase change heat transfer is notorious for increasing the irreversibility of, and therefore decreasing the efficiency of, geothermal power plants. Its significant contribution to the overall irreversibility of the plant makes it the most important source of inefficiency in the process. Recent studies here have shown the promotion of drop wise condensation in the lab by means of increasing the surface energy density of a tube with nanotechnology. The use of nanotechnology has allowed the creation of surface treatments which discourage water from wetting a tube surface during a static test. These surface treatments are unique in that they create high- contact angles on the condensing tube surfaces to promote drop wise condensation.

  9. Combined in-situ dilatometer and contact angle studies of interfacial reaction kinetics in brazing.

    SciTech Connect

    Dave, V. R.; Javernick, D. A.; Thoma, D. J.; Cola, M. J.; Hollis, K. J.; Smith, F. M.; Dauelsberg, L. B.

    2001-01-01

    Multi-component dissimilar material braze joints as shown in Figure 1 consisting of dissimilar base materials, filler materials and wetting agents are of tantamount importance in a wide variely of applications. This work combines dilatometry and contact angle measurements to characterize in-situ the multiple interfacial reaction pathways that occur in such systems. Whereas both of these methods are commonly used tools in metallurgical investigation, their combined use within the context of brazing studies is new and offers considerable additional insight. Applications are discussed to joints made between Beryllium and Monel with TiH{sub 2} as the wetting agent and Cu-28%Ag as the filler material.

  10. Extent of coverage of surfaces treated with hydrophobizing microemulsions: A mass spectrometry and contact angle study

    NASA Astrophysics Data System (ADS)

    Nagy, Andras; Kennedy, Joseph P.; Wang, Ping; Wesdemiotis, Chrys; Hanton, Scott D.

    2006-03-01

    Glass surfaces were treated with various hydrophobizing microemulsions (HME) containing mineral seal oil or polyisobutylene as hydrophobes emulsified by dimethyl dicoco ammonium chloride (i.e. mimicking commercial car wash practices) and characterized by mass spectrometry (MS) and contact angle measurements. The cationic emulsifier mediates the anchoring of hydrophobes to the polar glass surface. It is demonstrated that by the use of even very low (0.3-3.0 w%) HME concentrations the surfaces become hydrophobic and repel water even after numerous (˜20) rinsing cycles. According to MS evidence, however, the surfaces are not fully saturated with hydrophobes and the unprotected areas remain vulnerable to environmental damage.

  11. Experimental and Numerical Study of the Role of Disorder on Contact Angle Hysteresis

    NASA Astrophysics Data System (ADS)

    Sams, Angelina N.; Merten, Victoria E.; Pettersen, Michael S.

    2012-02-01

    Hysteretic behavior of the contact angle of a liquid on a solid is often ascribed to topographic or chemical heterogeneity of the surface. Recent experiments by Rolley and GuthmannootnotetextE. Rolley and C. Guthmann, Phys. Rev. Lett. 98, 166105 (2007). on liquid hydrogen on cesium suggest that both the hysteresis and the contact line dynamics might be explained in terms of the mesoscale structure of the cesium surface. We have investigated a room temperature system with similar wetting and structural properties, tetradecane on dodecanethiol-treated evaporated gold films, and compare the results with a model of the expected hysteresis due to the topographical heterogeneity as measured by AFM, and reported disorder in the thiol film.ootnotetextE. Delamarche, B. Michel, H. Kang and C.Gerber, Langmuir 10, 4103 (1994).

  12. The effect of friction and impact angle on the spermatozoa-oocyte local contact dynamics.

    PubMed

    Hedrih, Andjelka; Banić, Milan

    2016-03-21

    Although a large proportion of biomolecules involved in spermatozoa-oocyte interaction has been discovered so far, many details of fertilization mechanism remain unknown. Both biochemical and biomechanical components exist in the fertilization process. Mammalian sperm evolved a ZP (zona pelucida) thrust reduction penetration strategy probably in response to the ZP resilient elasticity. Using a biomechanical approach and FEM analysis, local contact stress, ZP deformations during impact and attempt of sperm head penetration relative to different sperm impact angles (SIA) were studied. The sperm-oocyte contact was defined as non-linear frictional contact. A transient structural analysis at 37°C revealed that, from the mechanical standpoint there are SIA that are more favorable for possible ZP penetration due to larger equivalent stress of ZP. An "slip-stick" resembling effect was identified for almost all examined SIA. The sperm head-ZP contact area increases as SIA decreases. Favorable ZP-stress state for sperm penetration regarding SIA are discussed. PMID:26780648

  13. Proactive gait strategies to mitigate risk of obstacle contact are more prevalent with advancing age.

    PubMed

    Muir, B C; Haddad, J M; Heijnen, M J H; Rietdyk, S

    2015-01-01

    The purposes of this study were to determine if healthy older adults adopt strategies to decrease the likelihood of obstacle contact, and to determine how these strategies are modified as a function of advancing age. Three age groups were examined: 20-25 yo (N = 19), 65-79 yo (N = 11), and 80-91 yo (N = 18). Participants stepped over a stationary, visible obstacle on a walkway. Step length and gait speed progressively decreased with advancing age; the shorter step length resulted in closer foot placement to the obstacle and an associated increased risk of obstacle contact. Lead (first limb to cross the obstacle) and trail (second) limb trajectories were examined for behavior that mitigated the risk of contact. (1) Consistent trail foot placement before the obstacle across all ages allowed space and time for the trail foot to clear the obstacle. (2) To avoid lead limb contact due to closer foot placement before and after the obstacle, the lead toe was raised more vertically after toe-off, and then the foot was extended beyond the landing position (termed lead overshoot) and retracted backwards to achieve the shortened step length. Lead overshoot progressively increased with advancing age. (3) Head angle was progressively lower with advancing age, an apparent attempt to gather more visual information during approach. Overall, a series of proactive strategies were adopted to mitigate risk of contact. However, the larger, more abrupt movements associated with a more vertical foot trajectory and lead overshoot may compromise whole body balance, indicating a possible trade-off between risk of contact and stability.

  14. A surface energy analysis of mucoadhesion: contact angle measurements on polycarbophil and pig intestinal mucosa in physiologically relevant fluids.

    PubMed

    Lehr, C M; Bouwstra, J A; Boddé, H E; Junginger, H E

    1992-01-01

    The possible role of surface energy thermodynamics in mucoadhesion was investigated with Polycarbophil and pig intestinal mucosa. In separate experiments, the surface energy parameters of the substrate (mucosa) and the adhesive (polymer film) were determined by contact angle measurements on captive air/octane bubbles in three physiologically relevant test fluids (isotonic saline, artificial gastric fluid, and artificial intestinal fluid). Whereas the swollen Polycarbophil films were relatively hydrophilic as indicated by small water contact angles (22, 23, and 16 degrees), the water contact angles measured on mucosal tissue were significantly larger (61, 48, and 57 degrees). Hence, mucus was found to possess an appreciable hydrophobicity. The measured adhesive performance (force of detachment) between Polycarbophil and pig small intestinal mucosa was highest in nonbuffered saline medium, intermediate in gastric fluid, and minimal in intestinal fluid. In agreement with this trend, the mismatch in surface polarities between substrate and adhesive, calculated from the contact angle data, increased in the same order.

  15. Super-mercuryphobic and hydrophobic diamond surfaces with hierarchical structures: Vanishment of the contact angle hysteresis with mercury

    NASA Astrophysics Data System (ADS)

    Escobar, Juan V.; Garza, Cristina; Alonso, Juan Carlos; Castillo, Rolando

    2013-05-01

    Increased roughness is known to enhance the natural wetting properties of surfaces, making them either more hydrophobic or more hydrophilic. In this work we study the wetting properties of water and mercury drops in contact with boron doped diamond films with progressively increased surface roughnesses. We show how thermal oxidation of a microcrystalline film creates pyramids decorated with sub-micron protrusions that turn its naturally mercuryphobic surface into super-mercuryphobic. With this liquid, we observe the vanishment of the contact angle hysteresis that is expected for rough surfaces as the contact angle approaches 180˚, making small drops of mercury roll along out of the surface at an apparent zero tilt-angle. In contrast, the incorporation of nano-globules on the oxidized surface through a silanization process is necessary to increase the hydrophobic properties of the film for which the contact angle with water reaches 138°. The wetting states that dominate in each case are discussed.

  16. Investigation of energy dissipation due to contact angle hysteresis in capillary effect

    NASA Astrophysics Data System (ADS)

    Athukorallage, Bhagya; Iyer, Ram

    2016-06-01

    Capillary action or Capillarity is the ability of a liquid to flow in narrow spaces without the assistance of, and in opposition to, external forces like gravity. Three effects contribute to capillary action, namely, adhesion of the liquid to the walls of the confining solid; meniscus formation; and low Reynolds number fluid flow. We investigate the dissipation of energy during one cycle of capillary action, when the liquid volume inside a capillary tube first increases and subsequently decreases while assuming quasi-static motion. The quasi-static assumption allows us to focus on the wetting phenomenon of the solid wall by the liquid and the formation of the meniscus. It is well known that the motion of a liquid on an non-ideal surface involves the expenditure of energy due to contact angle hysteresis. In this paper, we derive the equations for the menisci and the flow rules for the change of the contact angles for a liquid column in a capillary tube at a constant temperature and volume by minimizing the Helmholtz free energy using calculus of variations. We describe the numerical solution of these equations and present results from computations for the case of a capillary tube with 1 mm diameter.

  17. Effects of dynamic contact angle on liquid withdrawal from capillary tubes: (semi)-analytical solutions.

    PubMed

    Hilpert, Markus

    2010-07-15

    The displacement of a gas by a liquid in both horizontal and inclined capillary tubes where the tube inlet is connected to a liquid reservoir of constant pressure can be described by the Lucas-Washburn theory. One can also use the Lucas-Washburn theory to model the reverse flow, that is, liquid withdrawal, even though the latter case has received relatively little attention. In this paper, we derive analytical solutions for the travel time of the gas-liquid interface as a function of interface velocity. The interface position can be obtained by numerically integrating the numerically inverted interface velocity. Therefore we refer to these solutions as (semi)-analytical. We neglect inertial forces. However, we account for a dynamic contact angle where the nondimensional non-equilibrium Young force depends on the capillary number in the form of either a power law or a power series. We explore the entire nondimensional parameter space. The analytical solutions allow us to show that five different liquid withdrawal scenarios may occur that differ in the direction of flow and the sign of the acceleration of the gas-liquid interface: horizontal, upward, steady-state downward, accelerating downward, and decelerating downward flow. In the last case, the liquid is withdrawn from the tube either completely or partially. The (semi)-analytical solutions are also valid within the limit where the contact angle is constant.

  18. The variation of surface contact angles according to the diameter of carbon nanotubes.

    PubMed

    Choi, Eun Chang; Choi, Won Seok; Hong, Byungyou

    2009-06-01

    The shape of CNTs is affected by various growth parameters such as reaction time, temperature, working power, and pressure as well as the type of catalytic layer and synthesis method. In this work, the thickness of Ni catalyst layer was varied to control the diameter of synthesized CNT. Ni catalyst layer was prepared using a DC magnetron sputtering method and the layer thickness was varied from 40 nm to 100 nm with the increment of 20 nm. And CNTs were grown on Ni catalyst layer using the hot-filament plasma enhanced chemical vapor deposition (HF-PECVD) with ammonia (NH3) gas for pretreatment and acetylene (C2H2) gas for the synthesis. The shape of the resulting CNTs was analyzed using field emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HR-TEM). The surface contact angle of well-aligned CNTs was correlated with the diameter of CNT. As determined by contact angle measurement, the surface of CNT forests became more hydrophilic as the diameter of CNT increased. PMID:19504923

  19. Contact angle and surface tension measurements of a five-ring polyphenyl ether

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.

    1985-01-01

    Contact angle measurements were performed for a five-ring polyphenyl ether isomeric mixture on M-50 steel in a dry nitrogen atmosphere. Two different techniques were used: (1) a tilting plate apparatus, and (2) a sessile drop apparatus. Measurements were made for the temperature range 25 to 190 C. Surface tension was measured by a differential maximum bubble pressure technique over the range 23 to 220C in room air. The critical surface energy of spreading (gamma (sub c)) was determined for the polyphenyl ether by plotting the cosine of the contact angle (theta) versus the surface tension (gamma (sub LV)). The straight line intercept at cosine theta = 1 is defined as gamma (sub c). Gamma (sub c) was found to be 30.1 dyn/cm for the tilting plate technique and 31.3 dyn/cm for the sessile drop technique. These results indicate that the polyphenyl ether is inherently autophobic (i.e., it will not spread on its own surface film until its surface tension is less than gamma (sub c). This phenomenon is discussed in light of the wettability and wear problems encountered with this fluid.

  20. Surface energy of silicas, grafted with alkyl chains of increasing lengths, as measured by contact angle techniques

    SciTech Connect

    Kessaissia, Z. Papirer, E.; Donnet, J.B.

    1981-08-01

    Silica, modified by esterification with linear alcohols having between 1 and 20 carbon atoms, is compacted into smooth discs. Their surface polarity, measured by contact angle techniques, decreases with increasing surface coverage and chain length of the grafts. For the longer chains, the surface energy of the grafted silicas reaches a value close to the one of poly(ethylene). The spreading pressures of water on the modified silicas were measured either by contact angle or vapor adsorption techniques. 13 references.

  1. Calculating interface curvature and contact angle with NURBS for coating flow analysis

    NASA Astrophysics Data System (ADS)

    Hong, Hyeyoung; Nam, Jaewook

    2016-03-01

    Non-Uniform Rational B-Spline (NURBS) has actively been used in various field such as modeling, rendering, production of animation and engineering analysis program, etc., because NURBS has many advantages. It can exactly describe curved surface like conics, sphere and even human body. Also, it is effective at computational calculation because storage to calculate NURBS is far less compared to the other method. Therefore, we use NURBS curve to represent interface from computational data and experiment data. By exactly describing free surface, we can obtain several physical properties for calculating coating condition and compare these results with experimental results. It leads to calculate more accurate coating condition. In this study, we make smooth curve to represent interface using NURBS curve with optimization. And we calculate curvature and contact angle with these results.

  2. The contact angle for a droplet on homogeneous and spherical concave surfaces

    NASA Astrophysics Data System (ADS)

    Hu, Ai-Jun; Lv, Bao-Zhan; Wang, Xiao-Song; Zhou, Long

    2016-03-01

    Wetting of droplets on homogeneous and spherical concave rough surfaces is investigated based on thermodynamics. In this study, neglecting the droplet gravity and the thickness of the precursor film of the liquid-vapor interface, the three-phase system is divided into six parts using Gibbs concept of dividing surface. The system Helmholtz free energy is established based on thermodynamics. Supposing the temperature and chemical potential to be constant, a new generalized Young’s equation of the equilibrium contact angle for a spherical droplet on a spherical concave rough surfaces is obtained including the line tension effects. Under certain conditions, this generalized Young’s equation is the same as the Rusanov’s equation.

  3. Use of Atomic Oxygen for Increased Water Contact Angles of Various Polymers for Biomedical Applications

    NASA Technical Reports Server (NTRS)

    deGroh, Kim; Berger, Lauren; Roberts, Lily

    2009-01-01

    The purpose of this study was to determine the effect of atomic oxygen (AO) exposure on the hydrophilicity of nine different polymers for biomedical applications. Atomic oxygen treatment can alter the chemistry and morphology of polymer surfaces, which may increase the adhesion and spreading of cells on Petri dishes and enhance implant growth. Therefore, nine different polymers were exposed to atomic oxygen and water-contact angle, or hydrophilicity, was measured after exposure. To determine whether hydrophilicity remains static after initial atomic oxygen exposure, or changes with higher fluence exposures, the contact angles between the polymer and water droplet placed on the polymer s surface were measured versus AO fluence. The polymers were exposed to atomic oxygen in a 100-W, 13.56-MHz radio frequency (RF) plasma asher, and the treatment was found to significantly alter the hydrophilicity of non-fluorinated polymers. Pristine samples were compared with samples that had been exposed to AO at various fluence levels. Minimum and maximum fluences for the ashing trials were set based on the effective AO erosion of a Kapton witness coupon in the asher. The time intervals for ashing were determined by finding the logarithmic values of the minimum and maximum fluences. The difference of these two values was divided by the desired number of intervals (ideally 10). The initial desired fluence was then multiplied by this result (2.37), as was each subsequent desired fluence. The flux in the asher was determined to be approximately 3.0 x 10(exp 15) atoms/sq cm/sec, and each polymer was exposed to a maximum fluence of 5.16 x 10(exp 20) atoms/sq cm.

  4. Linking fractional wettability and contact angle dynamics in water repellent soils

    NASA Astrophysics Data System (ADS)

    Beatty, Sarah; Smith, James

    2016-04-01

    Dynamic soil water repellency has become a highly documented soil phenomenon across a range of environmental conditions and investigated within a range of disciplines. With global climate change at the environmental science fore, there is growing concern and need for accurate quantification of fundamental soil hydraulic properties and model parameterization. In the presence of soil water repellency, however, substantial unknowns remain in terms of characterizing repellency and drawing linkages to fundamental hydraulic parameters. This is often related to the complexity of investigating soil water repellency, which is often a challenging environment because of its spatially and temporally variable nature. To help bridge this gap, this work reports on different approaches using various technologies to explore opportunities that yield greater quantification and parametrization of soil water repellency in natural hydrologic systems at different scales. These approaches include X-ray microtomography (μXCT), Axisymmetric Drop Shape Analysis (ADSA), Drop Penetration tests (MED/WDPT), and Tension Infiltrometry. This work has shown the strength of conceptually linking contact angle dynamics and fractional wettability as a means to understand the nature of infiltration in water repellent soils and provide a mechanistic foundation upon which repellency can be quantified and related to fundamental hydraulic properties. Contact angle dynamics and fractional wettability are complimentary terminology that appear in the multiphase flow and soil physics literature, but have largely/essentially only been applied in synthetic systems. Their utility in natural environments is potentially significant and conceptually useful since they can readily incorporate existing characterizations while providing greater opportunity for articulating and defining specific behaviours in systems with high spatial and temporal heterogeneity.

  5. Experiments on the contact angle of n-propanol on differently prepared silver substrates at various temperatures and implications for the properties of silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Pinterich, T.; Winkler, P. M.; Vrtala, A. E.; Wagner, P. E.

    2011-08-01

    In this paper we present the results of contact angle measurements between n-propanol and silver substrates in the temperature range from -10 °C to 30 °C. The interest in a potential temperature dependence of contact angles originates from recent experiments by S. Schobesberger et al. (Schobesberger S., Strange temperature dependence observed for heterogeneous nucleation of n-propanol vapor on NaCl particles. Master's thesis, University of Vienna, 2008; Schobesberger S. et al., Experiments on the temperature dependence of heterogeneous nucleation on NaCl and Ag particles. In preparation.) investigating the temperature dependence for heterogeneous nucleation of n-propanol vapour on NaCl and on silver particles. We determined dynamic advancing θ a and receding θ r angles on variously prepared silver probes. The Dynamic Wilhelmy method (Wilhelmy L., Über die Abhängigkeit der Capillaritäts-Constanten des Alkohols von Substanz und Gestalt des benetzten festen Körpers. Ann. Phys. Chem., 199:177-217, 1863) was applied using a Krüss K12 Tensiometer, with a refrigerated double-walled glass top. With respect to its potential influence on heterogeneous nucleation mainly the advancing angle is of interest. The uniform probe geometry required was achieved by accurate cutting and by multiple polishing stages up to the accomplishment of a 0.04 μm grain size. The original probes consist of 925 sterling silver including a 7.5% copper content. Additional coating with silver pro Analysi (p.A.) was applied making use of pure silver powder evaporation process via Physical Vapour Deposition (PVD). Results show that a surface contamination by copper cannot be neglected for the specification of contact angles. It turned out that additional PVD coatings not only change the values of θa but also their temperature dependence. With increasing the number of coatings of a plate the contact angle decreases and its temperature dependence inverts. Since the contact angle hysteresis

  6. Dynamic contact angle effects onto the maximum drop impact spreading on solid surfaces

    NASA Astrophysics Data System (ADS)

    Vadillo, D. C.; Soucemarianadin, A.; Delattre, C.; Roux, D. C. D.

    2009-12-01

    This paper reports experimental investigations of drop impacts onto chemically treated surfaces with wettability from 5° to 160°. To follow in time the drop spreading, a high speed video camera was used, and it allows us to determine precisely the expansion of the drop and the profile of the free surface at the contact line. By changing the impact velocity, between less than 0.5 and 5 m/s, and the viscosity, from 1 to 100 mPa s, at constant surface tension, a broad range of Reynolds and Weber numbers is explored. This paper is divided into two parts. In the first part, the experimental drop evolution during spreading is directly reported and compared with previous works. Secondly, the emphasis is on the importance of the apparent dynamic contact angle for the prediction of the maximum spreading diameter. This achievement is manifested at low Reynolds numbers at which the matching between the experiment and the model is improved greatly.

  7. Caustics and Caustic-Interference in Measurements of Contact Angle and Flow Visualization Through Laser Shadowgraphy

    NASA Technical Reports Server (NTRS)

    Chao, David F.; Zhang, Neng-Li

    2002-01-01

    As one of the basic elements of the shadowgraphy optical system, the image of the far field from the droplet implicates plentiful information on the droplet profile. An analysis of caustics by wave theory shows that a droplet with a cylindrically symmetric Gaussian-hill-type profile produces a circular directional caustic in far field, which arises from the singularities (inflection line on the surface). The sessile liquid droplets, which profiles are restricted by surface tension, usually have a 'protruding foot' where the surface inflects. Simple geometrical optics indicates that the circular caustic stemming from the surface inflection at the protruding-foot takes the shape of the outmost ring on the image of the far field. It is the diameter of the outmost ring that is used as one of the key parameters in the measurements of contact angle through the laser shadowgraphic method. Different surface characteristics of the droplets produce different type of caustics, and therefore, the shape of the caustics can be used to determine the surface property of the sessile droplets. The present paper describes the measurement method of contact angIe using the circular caustics and the estimation of the protruding-foot height through the caustic interference.

  8. New procedure to measure simultaneously the surface tension and contact angle

    NASA Astrophysics Data System (ADS)

    Champmartin, S.; Ambari, A.; Le Pommelec, J. Y.

    2016-05-01

    This paper proposes a new procedure to simultaneously measure the static contact angle and the surface tension of a liquid using a spherical geometry. Unlike the other existing methods, the knowledge of one of both previous parameters and the displacement of the sphere are not mandatory. The technique is based on the measurement of two simple physical quantities: the height of the meniscus formed on a sphere at the very contact with a liquid bath and the resulting vertical force exerted on this object at equilibrium. The meniscus height, whose exact value requires the numerical resolution of the Laplace equation, is often estimated with an approximate 2D model, valid only for very large spheres compared to the capillary length. We develop instead another simplified solution of the Young-Laplace equation based on the work of Ferguson for the meniscus on a cylinder and adapted for the spherical shape. This alternative model, which is less restrictive in terms of the sphere size, is successfully compared to numerical solutions of the complete Young-Laplace equation. It appears to be accurate for sphere radii larger than only two capillary lengths. Finally the feasibility of the method is experimentally tested and validated for three common liquids and two "small" steel spheres.

  9. Impact of pressure and temperature on CO2-brine-mica contact angles and CO2-brine interfacial tension: Implications for carbon geo-sequestration.

    PubMed

    Arif, Muhammad; Al-Yaseri, Ahmed Z; Barifcani, Ahmed; Lebedev, Maxim; Iglauer, Stefan

    2016-01-15

    Precise characterization of wettability of CO2-brine-rock system and CO2-brine interfacial tension at reservoir conditions is essential as they influence capillary sealing efficiency of caprocks, which in turn, impacts the structural and residual trapping during CO2 geo-sequestration. In this context, we have experimentally measured advancing and receding contact angles for brine-CO2-mica system (surface roughness ∼12nm) at different pressures (0.1MPa, 5MPa, 7MPa, 10MPa, 15MPa, 20MPa), temperatures (308K, 323K, and 343K), and salinities (0wt%, 5wt%, 10wt%, 20wt% and 30wt% NaCl). For the same experimental matrix, CO2-brine interfacial tensions have also been measured using the pendant drop technique. The results indicate that both advancing and receding contact angles increase with pressure and salinity, but decrease with temperature. On the contrary, CO2-brine interfacial tension decrease with pressure and increase with temperature. At 20MPa and 308K, the advancing angle is measured to be ∼110°, indicating CO2-wetting. The results have been compared with various published literature data and probable factors responsible for deviations have been highlighted. Finally we demonstrate the implications of measured data by evaluating CO2 storage heights under various operating conditions. We conclude that for a given storage depth, reservoirs with lower pressures and high temperatures can store larger volumes and thus exhibit better sealing efficiency.

  10. Effect of Surface Roughness on Contact Angle Measurement of Nanofluid on Surface of Stainless Steel 304 by Sessile Drop Method

    NASA Astrophysics Data System (ADS)

    Prajitno, D. H.; Maulana, A.; Syarif, D. G.

    2016-08-01

    Contact angles play an important role in the mass and heat transfer. Stainless steel 304 has been used for nuclear power plan structure material until now. An experiment to measure contact angle of demineralized aqua and nanofluid containing nano particle of zirconia on metal surface of stainless steel 304 with sessile drop method was conducted. The measurement to measure the static contact angle and drop of nano fluid containing nano particle zirconia on stainless steel with different surface roughness was carried out. It was observed that stainless steel 304 was good hydrophylic properties with decreasing surface roughness of stainless steel during drop of aqua demineralized and nano fluid respectively. As a result the contact angle of demineralized aqua is decreased from 97.39 to 78.42 and contact angle of nano fluid from 94.3 to 67.50, respectively with decreasing surface roughness of stainless stee 304. Wettability of nanofluid on surface stainless steel 304 is better than aqua demineralized.

  11. Are the knee and ankle angles at contact related to the tendon properties of lower limbs in long distance runners?

    PubMed

    Kubo, Keitaro; Miyazaki, Daisuke; Yamada, Kenji; Shimoju, Shozo; Tsunoda, Naoya

    2016-01-01

    The purpose of this study was to investigate whether the knee and ankle angles at contact during running were related to the elastic properties of tendon structures in knee extensors and plantar flexors and performance in trained long distance runners. Thirty-two highly trained male long distance runners participated in this study. Elongation of tendon structures in knee extensors and plantar flexors were measured using ultrasonography while subjects performed ramp isometric contractions up to the voluntary maximum. The relationship between estimated muscle force and tendon elongation was fit to a linear regression, the slope of which was defined as the stiffness of tendon structures. Knee and ankle angles at contact during running were determined at a speed of 18 km/h on a treadmill. Knee and ankle angles at contact were not correlated to the stiffness of tendon structures in knee extensors and plantar flexors. In addition, the best official record in a 5000-m race was not significantly correlated to knee and ankle joint angles at contact. In conclusion, knee and ankle angles at contact were not related to the elastic properties of tendon structures in knee extensors and plantar flexor and the performance of long distance running.

  12. Contact Angle Hysteresis on Graphene Surfaces and Hysteresis-free Behavior on Oil-infused Graphite Surfaces

    NASA Astrophysics Data System (ADS)

    Wu, Cyuan-Jhang; Li, Yueh-Feng; Woon, Wei-Yen; Sheng, Yu-Jane; Tsao, Heng-Kwong

    2016-11-01

    Contact angle hysteresis (CAH) on graphitic surfaces, including chemical vapor deposition (CVD) graphene, reduced electrophoretic deposition (EPD) graphene, highly oriented pyrolytic graphite (HOPG), and polished graphite sheet, has been investigated. The hysteresis loops of water drops on the first three samples are similar but the receding contact angle is particularly small for the polished graphite sheet.The significant CAH observed on CVD graphene and HOPG associated with atom-scale roughness has to be attributed mainly to adhesion hysteresis (surface relaxation), instead of roughness or defects.The difference of the wetting behavior among those four graphitic samples has been further demonstrated by hexadecane drops. On the surface of HOPG or CVD graphene,the contact line expands continuously with time, indicating total wetting for which the contact angle does not exist and contact line pinning disappears. In contrast, on the surface of reduced EPD graphene, spontaneous spreading is halted by spikes on it and partial wetting with small contact angle (θ≈4°) is obtained. On the surface of polished graphite sheet, the superlipophilicity and porous structure are demonstrated by imbibition and capillary rise of hexadecane. Consequently, an oil-infused graphite surface can be fabricated and the ultralow CAH of water (∆θ≈2°) is achieved.

  13. The effect of axial force and contact angle on the welded area of plastic tube welded by ultrasonic welding

    NASA Astrophysics Data System (ADS)

    Thinvongpituk, C.; Bootwong, A.; Watanabe, Y.

    2010-03-01

    This study was aimed to apply the use of ultrasonic welding to weld round plastic tubes. The ultrasonic welding machine was designed to be able to work with a normal ultrasonic welding transducer by rotating the tube while it is being welded. The specimens used in this study were round plastic tubes (PMMA) with diameter of 35 mm and 2 mm thickness. End of each tube was machined to have angle of 2.8, 3.8 and 5.7 degree in order to create contact angle at the interface. The specimens were welded with frequency of 28 kHz and tube rotational speeds of 25 rpm, 45 rpm and 100 rpm. The axial force was applied to the tube in order to enhance the quality of joint. The experimental result revealed that the modified ultrasonic welding machine can generate the welded area around the circumference of tube. It was found that the axial force and contact angle have some effect to the quality of joint. The contact angle of 2.8/2.8 provided highest welded area compared to 3.8/3.8 and 5.7/5.7 degree of contact angle. In addition, the axial force between 80 N - 120 N provided high value of welded area. The pattern of welded area is also presented and discussed in the paper.

  14. The effect of axial force and contact angle on the welded area of plastic tube welded by ultrasonic welding

    NASA Astrophysics Data System (ADS)

    Thinvongpituk, C.; Bootwong, A.; Watanabe, Y.

    2009-12-01

    This study was aimed to apply the use of ultrasonic welding to weld round plastic tubes. The ultrasonic welding machine was designed to be able to work with a normal ultrasonic welding transducer by rotating the tube while it is being welded. The specimens used in this study were round plastic tubes (PMMA) with diameter of 35 mm and 2 mm thickness. End of each tube was machined to have angle of 2.8, 3.8 and 5.7 degree in order to create contact angle at the interface. The specimens were welded with frequency of 28 kHz and tube rotational speeds of 25 rpm, 45 rpm and 100 rpm. The axial force was applied to the tube in order to enhance the quality of joint. The experimental result revealed that the modified ultrasonic welding machine can generate the welded area around the circumference of tube. It was found that the axial force and contact angle have some effect to the quality of joint. The contact angle of 2.8/2.8 provided highest welded area compared to 3.8/3.8 and 5.7/5.7 degree of contact angle. In addition, the axial force between 80 N - 120 N provided high value of welded area. The pattern of welded area is also presented and discussed in the paper.

  15. Advances in Non-Contact Measurement of Creep Properties

    NASA Technical Reports Server (NTRS)

    Hyers, Robert; Canepari, Stacy; White, Erica Bischoff; Cretegny, Laurent; Rogers, jan

    2009-01-01

    As the required service temperatures for superalloys increases, so do the demands on testing for development of these alloys. Non-contact measurement of creep of refractory metals using electrostatic levitation has been demonstrated at temperatures up to 2300 C using samples of only 20-40 mg. These measurements load the spherical specimen by inertial forces due to rapid rotation. However, the first measurements relied on photon pressure to accelerate the samples to the high rotational rates of thousands of rotations per second, limiting the applicability to low stresses and high temperatures. Recent advances in this area extend this measurement to higher stresses and lower-temperatures through the use of an induction motor to drive the sample to such high rotational speeds. Preliminary results on new measurements on new materials will be presented.

  16. A facile fabrication of superhydrophobic nanocomposite coating with contact angles approaching the theoretical limit

    NASA Astrophysics Data System (ADS)

    Hancer, Mehmet; Arkaz, Harun

    2015-11-01

    Although there are many viable approaches to induce hydrophobicity, a superhydrophobic surface could only be fabricated by combination of surface chemistry modification and roughness enhancement. In this study, surface roughness was obtained by 12 nm SiO2 nanoparticles (NPs) which were chemically modified using a self-assembled monolayer of perfluorodecyltrichlorosilane. The SiO2 NPs which were rendered hydrophobic, then successfully dispersed into a poly silicon (silsesquioxane) matrix at varying concentrations from 0.5 to 4%. The NPs dispersed polymer suspension was then spray coated on to glass and aluminum coupons in order to achieve polymer thin film nanocomposites. The results were revealed a superhydrophobic surface with a water contact angle exceeding 178° with low hysteresis and bouncing water droplet behavior. Furthermore the composite film reliability (hot-humid and ice build-up) was tested in an environmental control chamber by precisely adjusting both temperature (85 °C) and relative humidity (85 RH). Taber abrasion testing was applied in order to gain insights into the abrasion resistance of nanocomposite film. Finally, ice formation was simulated at -20 °C on the superhydrophobic nanocomposite film coated substrates.

  17. Zeta potential, contact angles, and AFM imaging of protein conformation adsorbed on hybrid nanocomposite surfaces.

    PubMed

    Pinho, Ana C; Piedade, Ana P

    2013-08-28

    The sputtering deposition of gold (Au) and poly(tetrafluoroethylene) (PTFE) was used to prepare a nanocomposite hybrid thin film suitable for protein adsorption while maintaining the native conformation of the biological material. The monolithic PTFE and the nanocomposite PTFE/Au thin films, with Au content up to 1 at %, were co-deposited by r.f. magnetron sputtering using argon as a discharge gas and deposited onto 316L stainless steel substrates, the most commonly used steel in biomaterials. The deposited thin films, before and after bovine serum albumin (BSA) adsorption, were thoroughly characterized with special emphasis on the surface properties/characteristics by atomic force microscopy (AFM), zeta potential, and static and dynamic contact angle measurements, in order to assess the relationship between structure and conformational changes. The influence of a pre-adsorbed peptide (RGD) was also evaluated. The nanotopographic and chemical changes induced by the presence of gold in the nanocomposite thin films enable RGD bonding, which is critical for the maintenance of the BSA native conformation after adsorption.

  18. Metastable nanobubbles at the solid-liquid interface due to contact angle hysteresis.

    PubMed

    Nishiyama, Takashi; Yamada, Yutaka; Ikuta, Tatsuya; Takahashi, Koji; Takata, Yasuyuki

    2015-01-27

    Nanobubbles exist at solid-liquid interfaces between pure water and hydrophobic surfaces with very high stability, lasting in certain cases up to several days. Not only semispherical but also other shapes, such as micropancakes, are known to exist at such interfaces. However, doubt has been raised as to whether or not the nanobubbles are gas-phase entities. In this study, surface nanobubbles at a pure water-highly ordered pyrolytic graphite (HOPG) interface were investigated by peak force quantitative nanomechanics (PF-QNM). Multiple isolated nanobubbles generated by the solvent-exchange method were present on the terraced areas, avoiding the steps of the HOPG surface. Adjacent nanobubbles coalesced and formed metastable nanobubbles. Coalescence was enhanced by the PF-QNM measurement. We determined that nanobubbles can exist for a long time because of nanoscale contact angle hysteresis at the water-HOPG interface. Moreover, the hydrophilic steps of HOPG were avoided during coalescence, providing evidence that the nanobubbles are truly gas phase.

  19. Dynamic contact angle analysis of protein adsorption on polysaccharide multilayer's films for biomaterial reendothelialization.

    PubMed

    Benni, Safiya; Avramoglou, Thierry; Hlawaty, Hanna; Mora, Laurence

    2014-01-01

    Atherosclerosis is a major cardiovascular disease. One of the side effects is restenosis. The aim of this work was to study the coating of stents by dextran derivates based polyelectrolyte's multilayer (PEM) films in order to increase endothelialization of injured arterial wall after stent implantation. Films were composed with diethylaminoethyl dextran (DEAE) as polycation and dextran sulphate (DS) as polyanion. One film was composed with 4 bilayers of (DEAE-DS)4 and was labeled D-. The other film was the same as D- but with an added terminal layer of DEAE polycation: (DEAE-DS)4-DEAE (labeled D+). The dynamic adsorption/desorption of proteins on the films were characterized by dynamic contact angle (DCA) and atomic force microscopy (AFM). Human endothelial cell (HUVEC) adhesion and proliferation were quantified and correlated to protein adsorption analyzed by DCA for fibronectin, vitronectin, and bovine serum albumin (BSA). Our results showed that the endothelial cell response was optimal for films composed of DS as external layer. Fibronectin was found to be the only protein to exhibit a reversible change in conformation after desorption test. This behavior was only observed for (DEAE-DS)4 films. (DEAE-DS)4 films could enhance HUVEC proliferation in agreement with fibronectin ability to easily change from conformation.

  20. Dynamic Contact Angle Analysis of Protein Adsorption on Polysaccharide Multilayer's Films for Biomaterial Reendothelialization

    PubMed Central

    Benni, Safiya; Mora, Laurence

    2014-01-01

    Atherosclerosis is a major cardiovascular disease. One of the side effects is restenosis. The aim of this work was to study the coating of stents by dextran derivates based polyelectrolyte's multilayer (PEM) films in order to increase endothelialization of injured arterial wall after stent implantation. Films were composed with diethylaminoethyl dextran (DEAE) as polycation and dextran sulphate (DS) as polyanion. One film was composed with 4 bilayers of (DEAE-DS)4 and was labeled D−. The other film was the same as D− but with an added terminal layer of DEAE polycation: (DEAE-DS)4-DEAE (labeled D+). The dynamic adsorption/desorption of proteins on the films were characterized by dynamic contact angle (DCA) and atomic force microscopy (AFM). Human endothelial cell (HUVEC) adhesion and proliferation were quantified and correlated to protein adsorption analyzed by DCA for fibronectin, vitronectin, and bovine serum albumin (BSA). Our results showed that the endothelial cell response was optimal for films composed of DS as external layer. Fibronectin was found to be the only protein to exhibit a reversible change in conformation after desorption test. This behavior was only observed for (DEAE-DS)4 films. (DEAE-DS)4 films could enhance HUVEC proliferation in agreement with fibronectin ability to easily change from conformation. PMID:25276808

  1. Dynamic contact angle analysis of protein adsorption on polysaccharide multilayer's films for biomaterial reendothelialization.

    PubMed

    Benni, Safiya; Avramoglou, Thierry; Hlawaty, Hanna; Mora, Laurence

    2014-01-01

    Atherosclerosis is a major cardiovascular disease. One of the side effects is restenosis. The aim of this work was to study the coating of stents by dextran derivates based polyelectrolyte's multilayer (PEM) films in order to increase endothelialization of injured arterial wall after stent implantation. Films were composed with diethylaminoethyl dextran (DEAE) as polycation and dextran sulphate (DS) as polyanion. One film was composed with 4 bilayers of (DEAE-DS)4 and was labeled D-. The other film was the same as D- but with an added terminal layer of DEAE polycation: (DEAE-DS)4-DEAE (labeled D+). The dynamic adsorption/desorption of proteins on the films were characterized by dynamic contact angle (DCA) and atomic force microscopy (AFM). Human endothelial cell (HUVEC) adhesion and proliferation were quantified and correlated to protein adsorption analyzed by DCA for fibronectin, vitronectin, and bovine serum albumin (BSA). Our results showed that the endothelial cell response was optimal for films composed of DS as external layer. Fibronectin was found to be the only protein to exhibit a reversible change in conformation after desorption test. This behavior was only observed for (DEAE-DS)4 films. (DEAE-DS)4 films could enhance HUVEC proliferation in agreement with fibronectin ability to easily change from conformation. PMID:25276808

  2. Effects of Contact Angle Hysteresis on Ice Adhesion and Growth over Superhydrophobic Surfaces under Dynamic Flow Conditions

    SciTech Connect

    Sarshar, Mohammad Amin; Swarctz, Christopher; Hunter, Scott Robert; Simpson, John T; Choi, Chang-Hwan

    2012-01-01

    In this paper, the iceophobic properties of superhydrophobic surfaces are investigated under dynamic flow conditions by using a closed loop low-temperature wind tunnel. Superhydrophobic surfaces were prepared by coating the substrates of aluminum and steel plates with nano-structured hydrophobic particles. The superhydrophobic plates along with uncoated control ones were exposed to an air flow of 12 m/s and 20 F accompanying micron-sized water droplets in the icing wind tunnel and the ice formation and accretion were probed by high-resolution CCD cameras. Results show that the superhydrophobic coatings significantly delay the ice formation and accretion even under the dynamic flow condition of the highly energetic impingement of accelerated super-cooled water droplets. It is found that there is a time scale for this phenomenon (delay of the ice formation) which has a clear correlation with the contact angle hysteresis and the length scale of surface roughness of the superhydrophobic surface samples, being the highest for the plate with the lowest contact angle hysteresis and finer surface roughness. The results suggest that the key parameter for designing iceophobic surfaces is to retain a low contact angle hysteresis (dynamic property) and the non-wetting superhydrophobic state under the hydrodynamic pressure of impinging droplets, rather than to only have a high contact angle (static property), in order to result in efficient anti-icing properties under dynamic conditions such as forced flows.

  3. The effect of solid surface heterogeneity and roughness on the contact angle/drop (bubble) size relationship

    SciTech Connect

    Drelich, J.; Miller, J.D. . Dept. of Metallurgical Engineering)

    1994-04-01

    The contact angle for varying sizes of drops and air bubbles was measured on clean, heterogeneous, and rough solid surfaces. A linear correlation of the cosine of the contact angle vs reciprocal of the drop (bubble) base radius was obtained for the tetradecane/water/quartz and air/water/polyethylene systems, in which pure single-component liquids and freshly prepared clean solid surfaces were used. It was found that solid surface imperfections, heterogeneity and/or roughness, affect the contact angle /drop (bubble) size relationship. The change in contact angle with bubble size depended on the extent of solid surface heterogeneity, as was observed for the tetradecane/water/methylated quartz system with varying degrees of quartz methylation. For the air/water/polyethylene and air/water/gold systems, it was found that the slope of a plot of cos [theta] vs 1/r increased for rough surfaces when compared to that for smooth surfaces, and that these experimental data qualitatively support the modified Wenzel equation which includes the line-tension term.

  4. Contact angles of surface nanobubbles on mixed self-assembled monolayers with systematically varied macroscopic wettability by atomic force microscopy.

    PubMed

    Song, Bo; Walczyk, Wiktoria; Schönherr, Holger

    2011-07-01

    The dependence of the properties of so-called "surface nanobubbles" at the interface of binary self-assembled monolayers (SAMs) of octadecanethiol (ODT) and 16-mercaptohexadecanoic acid (MHDA) on ultraflat template-stripped gold and water on the surface composition was studied systematically by in situ atomic force microscopy (AFM). The macroscopic water contact angle (θ(macro)) of the SAMs spanned the range between 107° ± 1° and 15° ± 3°. Surface nanobubbles were observed on all SAMs by intermittent contact-mode AFM; their size and contact angle were found to depend on the composition of the SAM. In particular, nanoscopic contact angles θ(nano) < 86° were observed for the first time for hydrophilic surfaces. From fits of the top of the bubble profile to a spherical cap in three dimensions, quantitative estimates of nanobubble height, width, and radius of curvature were obtained. Values of θ(nano) calculated from these data were found to change from 167° ± 3° to 33° ± 58°, when θ(macro) decreased from 107° ± 1° to 37° ± 3°. While the values for θ(nano) significantly exceeded those of θ(macro) for hydrophobic SAMs, which is fully in line with previous reports, this discrepancy became less pronounced and finally vanished for more hydrophilic surfaces.

  5. Piling-to-buckling transition in the drying process of polymer solution drop on substrate having a large contact angle

    NASA Astrophysics Data System (ADS)

    Kajiya, Tadashi; Nishitani, Eisuke; Yamaue, Tatsuya; Doi, Masao

    2006-01-01

    We studied the drying process of polymer solution drops placed on a substrate having a large contact angle with the drop. The drying process takes place in three stages. First, the droplet evaporates keeping the contact line fixed. Second, the droplet shrinks uniformly with receding contact line. Finally the contact line is pinned again, and the droplet starts to be deformed. The shape of the final polymer deposit changes from concave dot, to flat dot, and then to concave dot again with the increase of the initial polymer concentration. This shape change is caused by the gradual transition from the solute piling mechanism proposed by Deegan to the crust buckling mechanism proposed by de Gennes and Pauchard.

  6. A novel methodology based on contact angle hysteresis approach for surface changes monitoring in model PMMA-Corega Tabs system

    NASA Astrophysics Data System (ADS)

    Pogorzelski, Stanisław J.; Berezowski, Zdzisław; Rochowski, Paweł; Szurkowski, Janusz

    2012-02-01

    The aim of the paper is to propose a quantitative description of dental surface modifications, resulting from application of Corega and oral cavity liquids, with several surface parameters derived from liquid/solid contact angle measurements. In particular, to predict the long-term effectiveness of denture cleansers in prosthetics, it is necessary to determine surface wettability variations for model dental materials/probe liquid systems related to the contamination effect caused by substances found in the oral cavity. A novel simple low-cost methodology, based on liquid drop contact angle hysteresis CAH approach developed by Chibowski, was adopted to trace solid surface free energy changes in the model PMMA-Corega Tabs interfacial layer. Contact angle and its hysteresis were studied with a sessile drop-inclined plate method in contact with a cleanser (Corega Tabs) and model liquids found in the oral cavity. The apparent solid surface free energy, adsorptive film pressure, work of adhesion and spreading were derived from contact angle hysteresis data for both model solid surfaces (reference) and samples affected by different reactive liquids for a certain time. A time-dependent surface wettability changes of dentures were expressed quantitatively in terms of the corresponding variations of the surface energy parameters which turned out to be unequivocally related to the cleanser exposure time and polarity of the liquids applied to the dental material. The novel methodology appeared to be a useful tool for long term surface characterization of dental materials treated with surfactants-containing liquids capable of forming adhesive layers. The time of optimal use and effectiveness of cleansers are also reflected dynamically in the corresponding variations of the surface wettability parameters. Further studies on a large group of dental surface-probe liquid systems are required to specify the role played by other important factors (liquid polarity, pH and temperature).

  7. Simultaneous measurement of contact angle and surface tension using axisymmetric drop-shape analysis-no apex (ADSA-NA).

    PubMed

    Kalantarian, A; David, R; Chen, J; Neumann, A W

    2011-04-01

    Axisymmetric drop-shape analysis-no apex (ADSA-NA) is a recent drop-shape method that allows the simultaneous measurement of contact angles and surface tensions of drop configurations without an apex (i.e., a sessile drop with a capillary protruding into the drop). Although ADSA-NA significantly enhanced the accuracy of contact angle and surface tension measurements compared to that of original ADSA using a drop with an apex, it is still not as accurate as a surface tension measurement using a pendant drop suspended from a holder. In this article, the computational and experimental aspects of ADSA-NA were scrutinized to improve the accuracy of the simultaneous measurement of surface tensions and contact angles. It was found that the results are relatively insensitive to different optimization methods and edge detectors. The precision of contact angle measurement was enhanced by improving the location of the contact points of the liquid meniscus with the solid substrate to subpixel resolution. To optimize the experimental design, the capillary was replaced with an inverted sharp-edged pedestal, or holder, to control the drop height and to ensure the axisymmetry of the drops. It was shown that the drop height is the most important experimental parameter affecting the accuracy of the surface tension measurement, and larger drop heights yield lower surface tension errors. It is suggested that a minimum nondimensional drop height (drop height divided by capillary length) of 1.7 is required to reach an error of less than 0.2 mJ/m(2) for the measured surface tension. As an example, the surface tension of water was measured to be 72.46 ± 0.04 at 24 °C by ADSA-NA, compared to 72.39 ± 0.01 mJ/m(2) obtained with pendant drop experiments.

  8. Contact angle and adsorption energies of nanoparticles at the air-liquid interface determined by neutron reflectivity and molecular dynamics

    NASA Astrophysics Data System (ADS)

    Reguera, Javier; Ponomarev, Evgeniy; Geue, Thomas; Stellacci, Francesco; Bresme, Fernando; Moglianetti, Mauro

    2015-03-01

    Understanding how nanomaterials interact with interfaces is essential to control their self-assembly as well as their optical, electronic, and catalytic properties. We present here an experimental approach based on neutron reflectivity (NR) that allows the in situ measurement of the contact angles of nanoparticles adsorbed at fluid interfaces. Because our method provides a route to quantify the adsorption and interfacial energies of the nanoparticles in situ, it circumvents problems associated with existing indirect methods, which rely on the transport of the monolayers to substrates for further analysis. We illustrate the method by measuring the contact angle of hydrophilic and hydrophobic gold nanoparticles, coated with perdeuterated octanethiol (d-OT) and with a mixture of d-OT and mercaptohexanol (MHol), respectively. The contact angles were also calculated via atomistic molecular dynamics (MD) computations, showing excellent agreement with the experimental data. Our method opens the route to quantify the adsorption of complex nanoparticle structures adsorbed at fluid interfaces featuring different chemical compositions.Understanding how nanomaterials interact with interfaces is essential to control their self-assembly as well as their optical, electronic, and catalytic properties. We present here an experimental approach based on neutron reflectivity (NR) that allows the in situ measurement of the contact angles of nanoparticles adsorbed at fluid interfaces. Because our method provides a route to quantify the adsorption and interfacial energies of the nanoparticles in situ, it circumvents problems associated with existing indirect methods, which rely on the transport of the monolayers to substrates for further analysis. We illustrate the method by measuring the contact angle of hydrophilic and hydrophobic gold nanoparticles, coated with perdeuterated octanethiol (d-OT) and with a mixture of d-OT and mercaptohexanol (MHol), respectively. The contact angles were

  9. A New Approach to Measure Contact Angle and Evaporation Rate with Flow Visualization in a Sessile Drop

    NASA Technical Reports Server (NTRS)

    Zhang, Nengli; Chao, David F.

    1999-01-01

    The contact angle and the spreading process of sessile droplet are very crucial in many technological processes, such as painting and coating, material processing, film-cooling applications, lubrication, and boiling. Additionally, as it is well known that the surface free energy of polymers cannot be directly, measured for their elastic and viscous restraints. The measurements of liquid contact angle on the polymer surfaces become extremely important to evaluate the surface free energy of polymers through indirect methods linked with the contact angle data. Due to the occurrence of liquid evaporation is inevitable, the effects of evaporation on the contact angle and the spreading become very important for more complete understanding of these processes. It is of interest to note that evaporation can induce Marangoni-Benard convection in sessile drops. However, the impacts of the inside convection on the wetting and spreading processes are not clear. The experimental methods used by previous investigators cannot simultaneously measure the spreading process and visualize the convection inside. Based on the laser shadowgraphic system used by the present author, a very simple optical procedure has been developed to measure the contact angle, the spreading speed, the evaporation rate, and to visualize inside convection of a sessile drop simultaneously. Two CCD cameras were used to synchronously record the real-time diameter of the sessile drop, which is essential for determination of both spreading speed and evaporation rate, and the shadowgraphic image magnified by the sessile drop acting as a thin plano-convex lens. From the shadowgraph, the inside convection of the drop can be observed if any and the image outer diameter, which linked to the drop profile, can be measured. Simple equations have been derived to calculate the drop profile, including the instantaneous contact angle, height, and volume of the sessile drop, as well as the evaporation rate. The influence of

  10. The influence of mercury contact angle, surface tension, and retraction mechanism on the interpretation of mercury porosimetry data.

    PubMed

    Rigby, Sean P; Edler, Karen J

    2002-06-01

    The use of a semi-empirical alternative to the standard Washburn equation for the interpretation of raw mercury porosimetry data has been advocated. The alternative expression takes account of variations in both mercury contact angle and surface tension with pore size, for both advancing and retreating mercury meniscii. The semi-empirical equation presented was ultimately derived from electron microscopy data, obtained for controlled pore glasses by previous workers. It has been found that this equation is also suitable for the interpretation of raw data for sol-gel silica spheres. Interpretation of mercury porosimetry data using the alternative to the standard Washburn equation was found to give rise to pore sizes similar to those obtained from corresponding SAXS data. The interpretation of porosimetry data, for both whole and finely powdered silica spheres, using the alternative expression has demonstrated that the hysteresis and mercury entrapment observed for whole samples does not occur for fragmented samples. Therefore, for these materials, the structural hysteresis and overall level of mercury entrapment is caused by the macroscopic (> approximately 30 microm), and not the microscopic (< approximately 30 microm), properties of the porous medium. This finding suggested that mercury porosimetry may be used to obtain a statistical characterization of sample macroscopic structure similar to that obtained using MRI. In addition, from a comparison of the pore size distribution from porosimetry with that obtained using complementary nitrogen sorption data, it was found that, even in the absence of hysteresis and mercury entrapment, pore shielding effects were still present. This observation suggested that the mercury extrusion process does not occur by a piston-type retraction mechanism and, therefore, the usual method for the application of percolation concepts to mercury retraction is flawed. PMID:16290649

  11. Research on the relation between the contact angle and the interface curvature radius of electrowetting liquid zoom lens

    NASA Astrophysics Data System (ADS)

    Zhao, Cunhua; Liang, Huiqin; Cui, Dongqing; Hong, Xinhua; Wei, Daling; Gao, Changliu

    2011-08-01

    In the ultralight or ultrathin applied domain of zoom lens, the traditional glass / plastic lens is limited for manufacture technology or cost. Therefore, a liquid lens was put forward to solve the problems. The liquid zoom lens has the merits of lower cost, smaller volume, quicker response, lower energy consumption, continuous zoom and higher accuracy. In liquid zoom lens the precise focal length is obtained by the contact angle changing to affect the curvature radius of interface. In our works, the relations of the exerted voltage, the contact angle, the curvature radius and the focal length were researched and accurately calculated. The calculation of the focal length provides an important theoretical basis for instructing the design of liquid zoom lens.

  12. Studies on interfacial tension and contact angle of synthesized surfactant and polymeric from castor oil for enhanced oil recovery

    NASA Astrophysics Data System (ADS)

    Babu, Keshak; Pal, Nilanjan; Bera, Achinta; Saxena, V. K.; Mandal, Ajay

    2015-10-01

    New synthesized polymeric surfactants have immensely attracted the researchers for further development of chemical enhanced oil recovery method particularly in surfactant flooding. Contact angle and interfacial tension measurement tests are the effective ways to identify proper chemicals/surfactants for enhanced oil recovery by chemical/surfactant flooding. In the present study a new polymeric surfactant was synthesized from pre-synthesized sodium methyl ester sulfonate (surfactant) and acrylamide for application in chemical enhanced oil recovery. The synthesized surfactant and polymeric surfactant were used to measure interfacial tension between their aqueous phase and crude oil phase to investigate the efficiency of the surfactants in reduction of interfacial tension. The synthesized polymeric surfactant has also ability to control the mobility because of its viscous nature in aqueous solution. Contact angles of solid-crude oil-surfactant interface were also measured to study the effect of the synthesized surfactant and polymeric surfactant on wettability alteration mechanism. Synergistic effect was studied by using NaCl and synthesized surfactants on interfacial tension. Dynamic interfacial tensions of the surfactant and polymeric surfactant solutions with crude oil were measured at different NaCl concentrations. Interfacial tension was found to be lowered up to 10-2 to 10-3 mN/m which is effective for oil recovery. Measurement of contact angle indicates the wettability change of the quartz surface. Comparative studies on efficiencies of synthesized sodium methyl ester sulfonate surfactant and polymeric surfactant were also carried out with respect to interfacial tension reduction and contact angle change.

  13. Contact Angle Measurements by AFM on Droplets of Intermediate-Length Alkanes Adsorbed on SiO2 Surfaces

    NASA Astrophysics Data System (ADS)

    Bai, M.; Taub, H.; Knorr, K.; Volkmann, U. G.; Hansen, F. Y.

    2007-03-01

    We have recently discovered that films of intermediate-length alkanes (n-CnH2n+2; 24 < n < 40) do not completely wet a SiO2 surface on a nanometer length scale [2]. In a narrow temperature range near the bulk melting point Tb, we observe a single layer of molecules oriented with their long axis perpendicular to the surface. On heating just above Tb, these molecules undergo a delayering transition to three-dimensional droplets that remain present up to their evaporation point. Here we report measurements by noncontact Atomic Force Microscopy of the contact angle of these droplets for a film of hexatriacontane (n-C36H74 or C36). Our preliminary measurements indicate that there is a weak maximum in the contact angle at ˜Tb + 3 C. Further measurements are planned to investigate whether the weak maximum in the contact angle is consistent with the droplets supporting a surface freezing effect as at the bulk fluid/air interface. ^2M. Bai, K. Knorr, M. J. Simpson, S. Trogisch, H. Taub, S. N. Ehrlich, H. Mo, U. G. Volkmann, F. Y. Hansen, cond-mat/0611497.

  14. Contact angle anomalies indicate that surface-active eluates from silicone coatings inhibit the adhesive mechanisms of fouling organisms.

    PubMed

    Meyer, Anne; Baier, Robert; Wood, Christina Darkangelo; Stein, Judith; Truby, Kathryn; Holm, Eric; Montemarano, Jean; Kavanagh, Christopher; Nedved, Brian; Smith, Celia; Swain, Geoff; Wiebe, Deborah

    2006-01-01

    Silicone coatings with critical surface tensions (CST) between 20 and 30 mN m-1 more easily release diverse types of biofouling than do materials of higher and lower CST. Oils added to these coatings selectively further diminish the attachment strengths of different marine fouling organisms, without significantly modifying the initial CST. In a search for the mechanisms of this improved biofouling resistance, the interfacial instabilities of four silicone coatings were characterised by comprehensive contact angle analyses, using up to 12 different diagnostic fluids selected to mimic the side chain chemistries of the common amino acids of bioadhesive proteins. The surfaces of painted steel test panels were characterised both before and after exposure to freshwater, brackish water, and seawater over periods ranging from 9 months to nearly 4 years. Contact angle measurements demonstrated significant surface activity of the oil-amended coatings both before and after long-term underwater exposure. The surface activity of the control (coating without oil) increased as a result of underwater exposure, consistent with mild surface chain scission and hydrolysis imparting a self-surfactancy to the coating and providing a weak boundary layer promoting continuing easy release of attaching foulants. Coatings with additives that most effectively reduced biofouling showed both initial and persistent contact angle anomalies for the test liquid, thiodiglycol, suggesting lower-shear biofouling release mechanisms based upon diminished bioadhesive crosslinking by interfering with hydrogen- and sulfhydryl bonds. Swelling of the silicone elastomeric coatings by hydrocarbon fluids was observed for all four coatings, before and after immersion.

  15. A model for pattern deposition from an evaporating solution subject to contact angle hysteresis and finite solubility.

    PubMed

    Zigelman, Anna; Manor, Ofer

    2016-06-29

    We propose a model for the pattern deposition of the solute from an evaporating drop of a dilute solution on a horizontal substrate. In the model we take into account the three-phase contact angle hysteresis and the deposition of the solute whenever its concentration exceeds the solubility limit. The evaporating drop is governed by a film equation. We show that unless for a very small three-phase contact angle or a very rapid evaporation rate the film adopts a quasi-steady geometry, satisfying the Young-Laplace equation to leading order. The concentration profile is assumed to satisfy an advection diffusion equation subject to the standard Fick's law for the diffusive flux. We further use an integral boundary condition to describe the dynamics of the concentration in the vicinity of the three-phase contact line; we replace an exact geometric description of the vicinity of the contact line, which is usually assumed such that mathematical singularities are avoided, with general insights about the concentration and its flux. We use our model to explore the relationships between a variety of deposition patterns and the governing parameters, show that the model repeats previous findings, and suggest further insights.

  16. Soil-water contact angle of some soils of the Russian Plane

    NASA Astrophysics Data System (ADS)

    Bykova, Galina; Tyugai, Zemfira; Milanovskiy, Evgeny; Shein, Evgeny

    2016-04-01

    INTRODUCTION Soil wettability affects the aggregate water resistance, the movement of moisture and dissolved substances, preferential flows, etc. There are many factors affecting the soil's wettability (the content of organic matter (OM), soil's mineralogical composition, particle size distribution), so it can reflect changes in the soil, including results of human impact. The quantitative characteristic of soil wettability is a contact angle (CA), its measurement is a new and difficult problem because of the complexity, heterogeneity and polydispersity of the object of investigation. The aim of this work is to study soil-water CA of some soils of the Russian Plane. MATERIALS AND METHODS The objects of study were sod-podzolic (Umbric Albeluvisols Abruptic, Eutric Podzoluvisols), grey forest non-podzolised (Greyic Phaeozems Albic, Haplic Greyzems), typical Chernozems (Voronic Chernozems pachic, Haplic Chernozems) - profiles under the forest and the arable land, and the chestnut (Haplic Kastanozems Chromic, Haplic Kastanozems) soils. The CA's determination was performed by a Drop Shape Analyzer DSA100 by the static sessile drop method. For all samples was determined the content of total and organic carbon (OC and TC) by dry combustion in oxygen flow. RESULTS AND DISCUSSION There is CA increasing from 85,1° (5 cm) to 40-45° (deeper, than 45 cm) in the sod-podzolic soil; OC content is changed at the same depths from 1,44 to 0.22%. We can see the similar picture in profiles of chernozems. In the forest profile the highest OC content and CA value are achieved on the surface of profile (6,41% and 78,1°), and by 90 cm these values are 1.9% and 50.2°. In the chernozem under the arable land the OC content is almost two times less and the profile is more wettable (from 50° to 19° at 5 and 100 cm). Corresponding with the OC content, the curve describing changes of CA in the profile of grey forest soil is S-shaped with peaks at 20 and 150 cm (81,3° and 70° respectively

  17. Advances in contact algorithms and their application to tires

    NASA Technical Reports Server (NTRS)

    Noor, Ahmed K.; Tanner, John A.

    1988-01-01

    Currently used techniques for tire contact analysis are reviewed. Discussion focuses on the different techniques used in modeling frictional forces and the treatment of contact conditions. A status report is presented on a new computational strategy for the modeling and analysis of tires, including the solution of the contact problem. The key elements of the proposed strategy are: (1) use of semianalytic mixed finite elements in which the shell variables are represented by Fourier series in the circumferential direction and piecewise polynomials in the meridional direction; (2) use of perturbed Lagrangian formulation for the determination of the contact area and pressure; and (3) application of multilevel iterative procedures and reduction techniques to generate the response of the tire. Numerical results are presented to demonstrate the effectiveness of a proposed procedure for generating the tire response associated with different Fourier harmonics.

  18. Advances in reduction techniques for tire contact problems

    NASA Technical Reports Server (NTRS)

    Noor, Ahmed K.

    1995-01-01

    Some recent developments in reduction techniques, as applied to predicting the tire contact response and evaluating the sensitivity coefficients of the different response quantities, are reviewed. The sensitivity coefficients measure the sensitivity of the contact response to variations in the geometric and material parameters of the tire. The tire is modeled using a two-dimensional laminated anisotropic shell theory with the effects of variation in geometric and material parameters, transverse shear deformation, and geometric nonlinearities included. The contact conditions are incorporated into the formulation by using a perturbed Lagrangian approach with the fundamental unknowns consisting of the stress resultants, the generalized displacements, and the Lagrange multipliers associated with the contact conditions. The elemental arrays are obtained by using a modified two-field, mixed variational principle. For the application of reduction techniques, the tire finite element model is partitioned into two regions. The first region consists of the nodes that are likely to come in contact with the pavement, and the second region includes all the remaining nodes. The reduction technique is used to significantly reduce the degrees of freedom in the second region. The effectiveness of the computational procedure is demonstrated by a numerical example of the frictionless contact response of the space shuttle nose-gear tire, inflated and pressed against a rigid flat surface. Also, the research topics which have high potential for enhancing the effectiveness of reduction techniques are outlined.

  19. How Does a Liquid Wet a Solid? Hydrodynamics of Dynamic Contact Angles

    NASA Technical Reports Server (NTRS)

    Rame, Enrique

    2001-01-01

    A contact line is defined at the intersection of a solid surface with the interface between two immiscible fluids. When one fluid displaces another immiscible fluid along a solid surface, the process is called dynamic wetting and a "moving" contact line (one whose position relative to the solid changes in time) often appears. The physics of dynamic wetting controls such natural and industrial processes as spraying of paints and insecticides, dishwashing, film formation and rupture in the eye and in the alveoli, application of coatings, printing, drying and imbibition of fibrous materials, oil recovery from porous rocks, and microfluidics.

  20. Hybrid bearing technology for advanced turbomachinery: Rolling contact fatigue testing

    SciTech Connect

    Dill, J.F.

    1996-01-01

    The purpose of this paper is to describe the basic structure and results to date of a major ARPA funded effort to provide a tribological performance database on ceramic bearing materials and their interaction with standard bearing steels. Program efforts include studies of material physical properties, machining characteristics, and tribological performance. The majority of the testing completed to date focuses on rolling contact fatigue testing of the ceramic materials, including efforts to arrive at optimum approaches to evaluating ceramic/steel hybrid combinations in rolling contact fatigue.

  1. ADVANCED CERAMIC COMPOSITES FOR MOLTEN ALUMINUM CONTACT APPLICATIONS

    SciTech Connect

    Hemrick, James Gordon; Peters, Klaus-Markus

    2009-01-01

    A new refractory material which was developed for use in molten aluminum contact applications was shown to exhibit improved corrosion and wear resistance leading to improved thermal management through reduced heat losses caused by refractory thinning and wastage. This material was developed based on an understanding of the corrosion and wear mechanisms associated with currently used aluminum contact refractories under a U.S. Department of Energy funded project to investigate multifunctional refractory materials for energy efficient handling of molten metals. This new material has been validated through an industrial trial at a commercial aluminum rod and cable mill. Material development and results of this industrial validation trial are discussed.

  2. The role of contact angle on unstable flow formation during infiltration and drainage in wettable porous media

    NASA Astrophysics Data System (ADS)

    Wallach, Rony; Margolis, Michal; Graber, Ellen R.

    2013-10-01

    The impact of contact angle on 2-D spatial and temporal water-content distribution during infiltration and drainage was experimentally studied. The 0.3-0.5 mm fraction of a quartz dune sand was treated and turned subcritically repellent (contact angle of 33°, 48°, 56°, and 75° for S33, S48, S56, and S75, respectively). The media were packed uniformly in transparent flow chambers and water was supplied to the surface as a point source at different rates (1-20 ml/min). A sequence of gray-value images was taken by CCD camera during infiltration and subsequent drainage; gray values were converted to volumetric water content by water volume balance. Narrow and long plumes with water accumulation behind the downward moving wetting front (tip) and negative water gradient above it (tail) developed in the S56 and S75 media during infiltration at lower water application rates. The plumes became bulbous with spatially uniform water-content distribution as water application rates increased. All plumes in these media propagated downward at a constant rate during infiltration and did not change their shape during drainage. In contrast, regular plume shapes were observed in the S33 and S48 media at all flow rates, and drainage profiles were nonmonotonic with a transition plane at the depth that water reached during infiltration. Given that the studied media have similar pore-size distributions, the conclusion is that imbibition hindered by the nonzero contact angle induced pressure buildup at the wetting front (dynamic water-entry value) that controlled the plume shape and internal water-content distribution during infiltration and drainage.

  3. Prediction of Unsteady Blade Surface Pressures on an Advanced Propeller at an Angle of Attack

    NASA Technical Reports Server (NTRS)

    Nallasamy, M.; Groeneweg, J. F.

    1989-01-01

    The numerical solution of the unsteady, three-dimensional, Euler equations is considered in order to obtain the blade surface pressures of an advanced propeller at an angle of attack. The specific configuration considered is the SR7L propeller at cruise conditions with a 4.6 deg inflow angle corresponding to the plus 2 deg nacelle tilt of the Propeller Test Assessment (PTA) flight test condition. The results indicate nearly sinusoidal response of the blade loading, with angle of attack. For the first time, detailed variations of the chordwise loading as a function of azimuthal angle are presented. It is observed that the blade is lightly loaded for part of the revolution and shocks appear from hub to about 80 percent radial station for the highly loaded portion of the revolution.

  4. In situ spectral calibration method for the impurity influx monitor (divertor) for ITER using angled physical contact fibers.

    PubMed

    Iwamae, A; Ogawa, H; Sugie, T; Kusama, Y

    2011-03-01

    The in situ calibration method for the impurity influx monitor (divertor) is experimentally examined. The total reflectance of the optical path from the focal point of the Cassegrain telescope to the first mirror is derived using a micro retroreflector array. An optical fiber with angled physical contact (APC) connectors reduces the return edge reflection. APC fibers and a multimode coupler increase the signal-to-noise ratio by about one order compared to that of triple-branched fibers and enable measurement of the wavelength dependence of the total reflectance of the optical system even after potential deterioration of mirror surfaces reduces reflectance.

  5. Spontaneous changes in contact angle of water and oil on novel flip-flop-type hydrophobic multilayer coatings

    NASA Astrophysics Data System (ADS)

    Kawamura, Go; Ema, Tomoyuki; Sakamoto, Hisatoshi; Wei, Xing; Muto, Hiroyuki; Matsuda, Atsunori

    2014-04-01

    Multilayer structures composed of poly(allylamine hydrochloride) (PAH) and Nafion were fabricated on glass substrates by layer-by-layer assembly. Some of the multilayers demonstrated spontaneous changes in contact angle of water and oil due to flip-flop movements of free sulfo groups in the Nafion layer, and the multilayers eventually possessed water repellency in air and oil repellency in water. The repellencies were enhanced by applying primer layers that were formed using SiO2 fine particles to increase surface roughness. Compared to typical hydrophobic and oleophobic surfaces, the multilayers showed practical levels for a use as soil release coatings.

  6. Low Angle Contact Between the Oaxaca and Juárez Terranes Deduced From Magnetotelluric Data

    NASA Astrophysics Data System (ADS)

    Arzate-Flores, Jorge A.; Molina-Garza, Roberto; Corbo-Camargo, Fernando; Márquez-Ramírez, Víctor

    2016-10-01

    We present the electrical resistivity model along a profile perpendicular to the Middle America trench in southern Mexico that reveals previously unrecognized tectonic features at upper to mid-crustal depths. Our results support the hypotheses that the upper crust of the Oaxaca terrane is a residual ~20 km thick crust composed by an ~10 km thick faulted crustal upper layer and an ~10 km thick hydrated and/or mineralized layer. Oaxaca basement overthrust the younger Juárez (or Cuicateco) terrane. The electrical resistivity model supports the interpretation of a slab subducting at a low angle below Oaxaca. Uplift in the Oaxaca region appears to be related to fault reactivation induced by low angle subduction. In the Juárez terrane, isostatic forces may contribute to uplift because it is largely uncompensated. In the Sierra Madre del Sur, closer to the coast, uplift is facilitated by slab-dehydration driven buoyancy. Both gravity and resistivity models are consistent with a thinned upper crust in the northeast end of the profile.

  7. Thickness dependence of surface energy and contact angle of water droplets on ultrathin MoS2 films.

    PubMed

    Guo, Yanhua; Wang, Zhengfei; Zhang, Lizhi; Shen, Xiaodong; Liu, Feng

    2016-06-01

    We have performed a systematic density functional study of surface energy of MoS2 films as a function of thickness from one to twelve layers with the consideration of van der Waals (vdW) interactions using the vdW-DF and DFT-D2 methods. Both vdW schemes show that the surface energy will increase with the increase of the number of atomic layers and converge to a constant value at about six layers. Based on the calculated surface energies, we further analyze the surface contact angle of water droplets on the MoS2 film surface using Young's equation as a function of thickness in comparison with experiments, from which the water-MoS2 interfacial energy is derived to be independent of MoS2 thickness. Our calculations indicate that the vdW interactions between the MoS2 layers play an important role in determining surface energy, and results in the thickness dependence of the contact angle of water droplets on the MoS2 film surface. Our results explain well the recent wetting experiment [Nano Lett., 2014, 14(8), 4314], and will be useful for future studies of physical and chemical properties of ultrathin MoS2 films.

  8. Contact angle hysteresis of liquid drops as means to measure adhesive energy of zein on solid substrates

    NASA Astrophysics Data System (ADS)

    Muthuselvi, L.; Dhathathreyan, Aruna

    2006-03-01

    Adhesion of zein to solid substrates has been studied using surface energy profiles as indices and by adhesion mapping using atomic force microscopy (AFM). Different plasticizers like glycerol and sorbitol have been used to form mixed films with zein and properties of these films are studied using surface energy profiles. Comparison of the results from the different mixed samples with those from the pure zein films showed that force mapping could identify areas rich in protein. The adhesion maps produced were deconvoluted from sample topography and contrasted with the data obtained from contact angle measurements. A comparison of the two methods shows that the extent of contact angle hysteresis is indicative of both hydrophobicity of the surface as well as the force of adhesion. Mechanical properties and microstructure of zein films prepared by casting from solutions and using Langmuir--Blodgett film technique have been investigated. Pure zein seemed brittle and exhibited an essentially linear relationship between stress and strain. Films with plasticizer were tougher than these films. In general, mixed films showed better mechanical properties than pure films and had higher ultimate tensile strength and increased per cent elongation. Further, the mixed films of zein showed a higher force of adhesion compared to the pure films.

  9. Thickness dependence of surface energy and contact angle of water droplets on ultrathin MoS2 films.

    PubMed

    Guo, Yanhua; Wang, Zhengfei; Zhang, Lizhi; Shen, Xiaodong; Liu, Feng

    2016-06-01

    We have performed a systematic density functional study of surface energy of MoS2 films as a function of thickness from one to twelve layers with the consideration of van der Waals (vdW) interactions using the vdW-DF and DFT-D2 methods. Both vdW schemes show that the surface energy will increase with the increase of the number of atomic layers and converge to a constant value at about six layers. Based on the calculated surface energies, we further analyze the surface contact angle of water droplets on the MoS2 film surface using Young's equation as a function of thickness in comparison with experiments, from which the water-MoS2 interfacial energy is derived to be independent of MoS2 thickness. Our calculations indicate that the vdW interactions between the MoS2 layers play an important role in determining surface energy, and results in the thickness dependence of the contact angle of water droplets on the MoS2 film surface. Our results explain well the recent wetting experiment [Nano Lett., 2014, 14(8), 4314], and will be useful for future studies of physical and chemical properties of ultrathin MoS2 films. PMID:27173479

  10. Evaluation of the surface properties of PTFE foam coating filter media using XPS and contact angle measurements

    NASA Astrophysics Data System (ADS)

    Park, Byung Hyun; Lee, Myong-Hwa; Kim, Sang Bum; Jo, Young Min

    2011-02-01

    A newly developed PTFE foam coating filter was developed which can be used for hot gas cleaning at temperatures up to 250 °C. The emulsion-type PTFE was coated onto a woven glass fiber using a foam coating method. The filter surface was closely examined using X-ray photoelectron spectroscopy (XPS) and contact angle measurements. The XPS results were used to determine the binding force between the carbon and fluorine of PTFE, which imparts coating stability to the filter medium. More than 95% of the bonds of the PTFE foam coating filter were between carbon and fluorine, and this filter demonstrated excellent hydrophobic and good oleophobic properties at the same time. The contact angles of liquid droplets on the filter surface were used to predict the potential wetability of the filter against water or oil. In addition, the very low surface free energy of the filter medium, which was evaluated using the Owens-Wendt method, demonstrates a very stable surface and a high de-dusting quality.

  11. The comparison between two irrigation regimens on the dentine wettability for an epoxy resin based sealer by measuring its contact angle formed to the irrigated dentine

    PubMed Central

    Mohan, Rayapudi Phani; Pai, Annappa Raghavendra Vivekananda

    2015-01-01

    Aim: The aim was to assess the influence of two irrigation regimens having ethylenediaminetetraacetic acid (EDTA) and ethylenediaminetetraacetic acid with cetrimide (EDTAC) as final irrigants, respectively, on the dentine wettability for AH Plus sealer by comparing its contact angle formed to the irrigated dentine. Materials and Methods: Study samples were divided into two groups (n = 10). The groups were irrigated with 3% sodium hypochlorite (NaOCl) solution followed by either 17% EDTA or 17% EDTAC solution. AH Plus was mixed, and controlled volume droplet (0.1 mL) of the sealer was placed on the dried samples. The contact angle was measured using a Dynamic Contact Angle Analyzer and results were analyzed using SPSS 21.0 and 2 sample t-test. Results: There was a significant difference in the contact angle of AH Plus formed to the dentine irrigated with the above two regimens. AH Plus showed significantly lower contact angle with the regimen having EDTAC as a final irrigant than the one with EDTA (P < 0.05). Conclusion: An irrigation regimen consisting of NaOCl with either EDTA or EDTAC solution as a final irrigant influences the dentine wettability and contact angle of a sealer. EDTAC as a final irrigant facilitates better dentin wettability than EDTA for AH Plus to promote its better flow and adhesion. PMID:26180409

  12. Photoinduced superhydrophilicity: a kinetic study of time dependent photoinduced contact angle changes on TiO2 surfaces.

    PubMed

    Foran, Philip S; Boxall, Colin; Denison, Kieth R

    2012-12-21

    Transparent TiO(2) thin films were prepared on quartz substrates via a reverse micelle, sol-gel, spin-coating technique. The time dependence of the TiO(2) film photoinduced superhydrophilicity (PISH) was measured by goniometric observation of the contact angle, θ, of sessile water drops at the film surfaces. In these measurements, the TiO(2) substrate was illuminated by 315 nm light and drops were sequentially applied at a range of illumination times. Using a model for the wetting of heterogeneous surfaces derived by Israelachvili and Gee, these measurements were used to calculate the time dependence of f(2), the fractional surface coverage of the TiO(2) surface by adventitious contaminating organics (Israelachvili, J. N.; Gee, M. L. Contact angles on chemically heterogeneous surfaces. Langmuir 1989, 5, 288). Extending this model to include a Langmuir-Hinshelwood based kinetic analysis of f(2) as a function of time allowed for calculation of an expected value for θ immediately prior to illumination, that is, at illumination time t = 0. Such expected values of θ at t = 0 were calculated using two possible values of θ(1), the contact angle on a pristine unilluminated homogeneous TiO(2) surface: (i) θ(1) = 4° as suggested by, inter alia, Zubkov et al. (Zubkov, T.; Stahl, D.; Thompson, T. L.; Panayotov, D.; Diwald, O.; Yates, J. T. Ultraviolet Light-Induced Hydrophilicity Effect on TiO(2)(110)(1 × 1). Dominant Role of the Photooxidation of Adsorbed Hydrocarbons Causing Wetting by Water Droplets. J. Phys. Chem. B2005, 109, 15454); and (ii) where θ(1) = 25°, as suggested by Fujishima et al., representative of a more hydrophobic homogeneous TiO(2) surface that reconstructs upon exposure to ultraband gap illumination into a hydrophilic surface where θ(1) → 0° (Fujishima, A.; Zhang, X.; Tryk, D. A. TiO(2) photocatalysis and related surface phenomena Surf. Sci. Rep.2008, 63, 515). Analysis of data from our experiments and from selected literature sources

  13. Determining Chiral Configuration of Diamines via Contact Angle Measurements on Enantioselective Alanine-Appended Benzene-Tricarboxamide Gelators.

    PubMed

    Jung, Sung Ho; Kim, Ka Young; Ahn, Ahreum; Choi, Myong Yong; Jaworski, Justyn; Jung, Jong Hwa

    2016-06-01

    Spectroscopic techniques exist that may discern between enantiomers and assess chiral purity. A nonspectroscopic approach that may be directly observed could provide numerous benefits. Using chiral alanine-appended benzene-tricarboxamide gelators, we reveal a methanol gel system that is capable of providing visual discrimination between enantiomers of various diamines. Specifically, gelation is induced by supramolecular nanofiber assembly resulting from interaction between a chiral gelator and a diamine of opposing chirality (i.e., a heterochiral system). Upon further implementing the chiral gelator in electrospun fibers as solid state films, we revealed enantioselective surface wetting properties that allowed for determining chirality through contact angle measurements. While these two approaches of observable gelation and surface wetting offer nonspectroscopic approaches, we also find that the supramolecular nanofiber assembly was able to enhance the induced circular dichroism signal resulting from addition of chiral diamines, allowing precise quantification of their enantiomeric purity.

  14. Utilization of profilometry, SEM, AFM and contact angle measurements in describing surfaces of plastic floor coverings and explaining their cleanability

    NASA Astrophysics Data System (ADS)

    Kuisma, R.; Pesonen-Leinonen, E.; Redsven, I.; Kymäläinen, H.-R.; Saarikoski, I.; Sjöberg, A.-M.; Hautala, M.

    2005-06-01

    The tendency to soil and cleanability of ten commercial plastic floor coverings: eight vinyl (PVC) floor coverings, one vinyl composite tile and one plastic composite tile, were examined. Floor coverings were soiled with inorganic, organic and biological soil. The cleanability was measured both by bioluminescence of ATP (adenosine triphosphate) and colorimetrically. The surface topography was studied by AFM, SEM and with a profilometer. From the 2D- and 3D-profilometric measurements several characteristic parameters of the surface profiles were extracted. The tendency to soil and cleanability were compared with the characteristics of the surface. A weak correlation was found between roughness and soilability but no correlation between roughness and cleanability. Roughness had no correlation with contact angle.

  15. Combustion behaviors of a compression-ignition engine fueled with diesel/methanol blends under various fuel delivery advance angles.

    PubMed

    Huang, Zuohua; Lu, Hongbing; Jiang, Deming; Zeng, Ke; Liu, Bing; Zhang, Junqiang; Wang, Xibin

    2004-12-01

    A stabilized diesel/methanol blend was described and the basic combustion behaviors based on the cylinder pressure analysis was conducted in a compression-ignition engine. The study showed that increasing methanol mass fraction of the diesel/methanol blends would increase the heat release rate in the premixed burning phase and shorten the combustion duration of the diffusive burning phase. The ignition delay increased with the advancing of the fuel delivery advance angle for both the diesel fuel and the diesel/methanol blends. For a specific fuel delivery advance angle, the ignition delay increased with the increase of the methanol mass fraction (oxygen mass fraction) in the fuel blends and the behaviors were more obvious at low engine load and/or high engine speed. The rapid burn duration and the total combustion duration increased with the advancing of the fuel delivery advance angle. The centre of the heat release curve was close to the top-dead-centre with the advancing of the fuel delivery advance angle. Maximum cylinder gas pressure increased with the advancing of the fuel delivery advance angle, and the maximum cylinder gas pressure of the diesel/methanol blends gave a higher value than that of the diesel fuel. The maximum mean gas temperature remained almost unchanged or had a slight increase with the advancing of the fuel delivery advance angle, and it only slightly increased for the diesel/methanol blends compared to that of the diesel fuel. The maximum rate of pressure rise and the maximum rate of heat release increased with the advancing of the fuel delivery advance angle of the diesel/methanol blends and the value was highest for the diesel/methanol blends.

  16. Imaging of oil layers, curvature and contact angle in a mixed-wet and a water-wet carbonate rock

    NASA Astrophysics Data System (ADS)

    Singh, Kamaljit; Bijeljic, Branko; Blunt, Martin J.

    2016-03-01

    We have investigated the effect of wettability of carbonate rocks on the morphologies of remaining oil after sequential oil and brine injection in a capillary-dominated flow regime at elevated pressure. The wettability of Ketton limestone was altered in situ using an oil phase doped with fatty acid which produced mixed-wet conditions (the contact angle where oil contacted the solid surface, measured directly from the images, θ=180°, while brine-filled regions remained water-wet), whereas the untreated rock (without doped oil) was weakly water-wet (θ=47 ± 9°). Using X-ray micro-tomography, we show that the brine displaces oil in larger pores during brine injection in the mixed-wet system, leaving oil layers in the pore corners or sandwiched between two brine interfaces. These oil layers, with an average thickness of 47 ± 17 µm, may provide a conductive flow path for slow oil drainage. In contrast, the oil fragments into isolated oil clusters/ganglia during brine injection under water-wet conditions. Although the remaining oil saturation in a water-wet system is about a factor of two larger than that obtained in the mixed-wet rock, the measured brine-oil interfacial area of the disconnected ganglia is a factor of three smaller than that of oil layers.

  17. Correlation of Oil-Water and Air-Water Contact Angles of Diverse Silanized Surfaces and Relationship to Fluid Interfacial Tensions

    SciTech Connect

    Grate, Jay W.; Dehoff, Karl J.; Warner, Marvin G.; Pittman, Jonathan W.; Wietsma, Thomas W.; Zhang, Changyong; Oostrom, Martinus

    2012-02-24

    The use of air-water, {Theta}{sub wa}, or air-liquid contact angles is customary in surface science, while oil-water contact angles {Theta}{sub ow}, are of paramount importance in subsurface multiphase flow phenomena including petroleum reocovery, nonaqueous phase liquid fate and transport, and geological carbon sequestration. In this paper we determine both the air-water and oil-water contact angles of silica surfaces modified with a diverse selection of silanes, using hexadecane as the oil. The silanes included alkylsilanes, alkylarylsilanes, and silanes with alkyl or aryl groups that are functionalized with heteroatoms such as N, O, and S. These silanes yielded surfaces with wettabilities from water-wet to oil wet, including specific silanized surfaces functionalized with heteroatoms that yield intermediate wet surfaces. The oil-water contact angles for clean and silanized surfaces, excluding one partially fluorinated surface, correlate linearly with air-water contact angles with a slope of 1.41 (R = 0.981, n = 13). These data were used to examine a previously untested theoretical treatment relating air-water and oil-water contact angles in terms of fluid interfacial energies. Plotting the cosines of these contact angles against one another, we obtain a linear relationship in excellent agreement with the theoretical treatment; the data fit cos {Theta}{sub ow} = 0.667 cos {Theta}{sub ow} + 0.384 (R = 0.981, n = 13), intercepting cos {Theta}{sub ow} = -1 at -0.284. The theoretical slope, based on the fluid interfacial tensions {Theta}{sub wa}, {Theta}{sub ow}, and {Theta}{sub oa}, is 0.67. We also demonstrate how silanes can be used to alter the wettability of the interior of a pore network micromodel device constructed in silicon/silica with a glass cover plate. Such micromodels are used to study multiphase flow phenomena. The contact angle of the resulting interior was determined in situ. An intermediate wet micromodel gave a contact angle in excellent agreement

  18. Experimental studies of contact angle hysteresis phenomena on polymer surfaces – Toward the understanding and control of wettability for different applications.

    PubMed

    Grundke, K; Pöschel, K; Synytska, A; Frenzel, R; Drechsler, A; Nitschke, M; Cordeiro, A L; Uhlmann, P; Welzel, P B

    2015-08-01

    Contact angle hysteresis phenomena on polymer surfaces have been studied by contact angle measurements using sessile liquid droplets and captive air bubbles in conjunction with a drop shape method known as Axisymmetric Drop Shape Analysis - Profile (ADSA-P). In addition, commercially available sessile drop goniometer techniques were used. The polymer surfaces were characterized with respect to their surface structure (morphology, roughness, swelling) and surface chemistry (elemental surface composition, acid-base characteristics) by scanning electron microscopy (SEM), scanning force microscopy (SFM), ellipsometry, X-ray photoelectron spectroscopy (XPS) and streaming potential measurements. Heterogeneous polymer surfaces with controlled roughness and chemical composition were prepared by different routes using plasma etching and subsequent dip coating or grafting of polymer brushes, anodic oxidation of aluminium substrates coated with thin polymer films, deposition techniques to create regular patterned and rough fractal surfaces from core-shell particles, and block copolymers. To reveal the effects of swelling and reorientation at the solid/liquid interface contact angle hysteresis phenomena on polyimide surfaces, cellulose membranes, and thermo-responsive hydrogels have been studied. The effect of different solutes in the liquid (electrolytes, surfactants) and their impact on contact angle hysteresis were characterized for solid polymers without and with ionizable functional surface groups in aqueous electrolyte solutions of different ion concentrations and pH and for photoresist surfaces in cationic aqueous surfactant solutions. The work is an attempt toward the understanding of contact angle hysteresis phenomena on polymer surfaces aimed at the control of wettability for different applications.

  19. Fitting an MSD (mini scleral design) rigid contact lens in advanced keratoconus with INTACS.

    PubMed

    Dalton, Kristine; Sorbara, Luigina

    2011-12-01

    Keratoconus is a bilateral degenerative disease characterized by a non-inflammatory, progressive central corneal ectasia (typically asymmetric) and decreased vision. In its early stages it may be managed with spectacles and soft contact lenses but more commonly it is managed with rigid contact lenses. In advanced stages, when contact lenses can no longer be fit, have become intolerable, or corneal damage is severe, a penetrating keratoplasty is commonly performed. Alternative surgical techniques, such as the use of intra-stromal corneal ring segments (INTACS) have been developed to try and improve the fit of rigid contact lenses in keratoconic patients and avoid penetrating keratoplasties. This case report follows through the fitting of rigid contact lenses in an advanced keratoconic cornea after an INTACS procedure and discusses clinical findings, treatment options, and the use of mini-scleral and scleral lens designs as they relate to the challenges encountered in managing such a patient. Mini-scleral and scleral lenses are relatively easy to fit, and can be of benefit to many patients, including advanced keratoconic patients, post-INTAC patients and post-penetrating keratoplasty patients. PMID:21664856

  20. Tungsten Contact and Line Resistance Reduction with Advanced Pulsed Nucleation Layer and Low Resistivity Tungsten Treatment

    NASA Astrophysics Data System (ADS)

    Chandrashekar, Anand; Chen, Feng; Lin, Jasmine; Humayun, Raashina; Wongsenakhum, Panya; Chang, Sean; Danek, Michal; Itou, Takamasa; Nakayama, Tomoo; Kariya, Atsushi; Kawaguchi, Masazumi; Hizume, Shunichi

    2010-09-01

    This paper describes electrical testing results of new tungsten chemical vapor deposition (CVD-W) process concepts that were developed to address the W contact and bitline scaling issues on 55 nm node devices. Contact resistance (Rc) measurements in complementary metal oxide semiconductor (CMOS) devices indicate that the new CVD-W process for sub-32 nm and beyond - consisting of an advanced pulsed nucleation layer (PNL) combined with low resistivity tungsten (LRW) initiation - produces a 20-30% drop in Rc for diffused NiSi contacts. From cross-sectional bright field and dark field transmission electron microscopy (TEM) analysis, such Rc improvement can be attributed to improved plugfill and larger in-feature W grain size with the advanced PNL+LRW process. More experiments that measured contact resistance for different feature sizes point to favorable Rc scaling with the advanced PNL+LRW process. Finally, 40% improvement in line resistance was observed with this process as tested on 55 nm embedded dynamic random access memory (DRAM) devices, confirming that the advanced PNL+LRW process can be an effective metallization solution for sub-32 nm devices.

  1. Advances and applications of dynamic-angle spinning nuclear magnetic resonance

    SciTech Connect

    Baltisberger, J.H.

    1993-06-01

    This dissertation describes nuclear magnetic resonance experiments and theory which have been developed to study quadrupolar nuclei (those nuclei with spin greater than one-half) in the solid state. Primarily, the technique of dynamic-angle spinning (DAS) is extensively reviewed and expanded upon in this thesis. Specifically, the improvement in both the resolution (two-dimensional pure-absorptive phase methods and DAS angle choice) and sensitivity (pulse-sequence development), along with effective spinning speed enhancement (again through choice of DAS conditions or alternative multiple pulse schemes) of dynamic-angle spinning experiment was realized with both theory and experimental examples. The application of DAS to new types of nuclei (specifically the {sup 87}Rb and {sup 85}Rb nuclear spins) and materials (specifically amorphous solids) has also greatly expanded the possibilities of the use of DAS to study a larger range of materials. This dissertation is meant to demonstrate both recent advances and applications of the DAS technique, and by no means represents a comprehensive study of any particular chemical problem.

  2. Effect of chemical heterogeneity of biodegradable polymers on surface energy: A static contact angle analysis of polyester model films.

    PubMed

    Belibel, R; Avramoglou, T; Garcia, A; Barbaud, C; Mora, L

    2016-02-01

    Biodegradable and bioassimilable poly((R,S)-3,3 dimethylmalic acid) (PDMMLA) derivatives were synthesized and characterized in order to develop a new coating for coronary endoprosthesis enabling the reduction of restenosis. The PDMMLA was chemically modified to form different custom groups in its side chain. Three side groups were chosen: the hexyl group for its hydrophobic nature, the carboxylic acid and alcohol groups for their acid and neutral hydrophilic character, respectively. The sessile drop method was applied to characterize the wettability of biodegradable polymer film coatings. Surface energy and components were calculated. The van Oss approach helped reach not only the dispersive and polar acid-base components of surface energy but also acid and basic components. Surface topography was quantified by atomic force microscopy (AFM) and subnanometer average values of roughness (Ra) were obtained for all the analyzed surfaces. Thus, roughness was considered to have a negligible effect on wettability measurements. In contrast, heterogeneous surfaces had to be corrected by the Cassie-Baxter equation for copolymers (10/90, 20/80 and 30/70). The impact of this correction was quantified for all the wettability parameters. Very high relative corrections (%) were found, reaching 100% for energies and 30% for contact angles. PMID:26652458

  3. Characterization of critically cleaned sapphire single-crystal substrates by atomic force microscopy, XPS and contact angle measurements

    NASA Astrophysics Data System (ADS)

    Zhang, Dan; Wang, You; Gan, Yang

    2013-06-01

    A contaminant-free surface of single-crystal α-Al2O3 (or sapphire) substrates is key to the experimental studies of its surface and interfacial properties at ambient conditions. Here we critically evaluated methods reported in the literature using comprehensive surface analysis techniques including atomic force microscopy, XPS and contact angle measurements. We found that reported methods did not perform well in terms of removing both organic and particulate contaminants from the (0 0 0 1) basal surface. After thoroughly examining the cleaning effect of various chemical solutions and UV light and plasma irradiation, and based on modified RCA cleaning protocols, we proposed a new wet-cleaning method showing outstanding cleaning performance. This new reliable method will be very useful for the next-step surface chemistry study of single-crystal α-Al2O3. It was also demonstrated that AFM, due to its high spatial resolution and sensitivity as a local probe technique, was an indispensable tool for surface contamination control studies.

  4. Effects of various chair-side surface treatment methods on dental restorative materials with respect to contact angles and surface roughness.

    PubMed

    Sturz, Candida R C; Faber, Franz-Josef; Scheer, Martin; Rothamel, Daniel; Neugebauer, Jörg

    2015-01-01

    Available chair-side surface treatment methods may adversely affect prosthetic materials and promote plaque accumulation. This study investigated the effects of treatment procedures on three resin restorative materials, zirconium-dioxide and polyetheretherketone in terms of surface roughness and hydrophobicity. Treatments were grinding with silicon carbide paper or white Arkansas stone, blasting with prophylaxis powder and polishing with diamond paste. Surface roughness was assessed using confocal laser scanning. Hydrophobicity as measured by water contact angle was determined by computerized image analysis using the sessile drop technique. All of the specific surface treatments performed led to significant changes in contact angle values and surface roughness (Ra) values. Median contact angle values ranged from 51.6° to 114°. Ra values ranged from 0.008 µm to 2.917 µm. Air-polishing as well as other polishing procedures increased surface roughness values in all materials except zirconium dioxide. Polyetheretherketone displayed greatest change in contact angle values after air-polishing treatment. PMID:26632228

  5. Surface characterization of poly(L-lactic acid)-methoxy poly(ethylene glycol) diblock copolymers by static and dynamic contact angle measurements, FTIR, and ATR-FTIR.

    PubMed

    Mert, O; Doganci, E; Erbil, H Y; Demir, A S

    2008-02-01

    The surface composition and surface free energy properties of two types of amphiphilic and semicrystalline diblock copolymers consisting of poly(L-lactic acid) coupled to (methoxy poly(ethylene glycol) (PLLA-MePEG) having differing block lengths of PEG were investigated by using static and dynamic contact angle measurements, transmission Fourier infrared spectroscopy (FTIR), and attenuated total reflection spectroscopy (ATR-FTIR) and compared with results obtained from PLLA and MePEG homopolymers. The contact angle results were evaluated by using the van Oss-Good method (acid-base method), and it was determined that the Lewis base surface tension coefficient (gamma-) of the copolymers increased with an increase of the PEG molar content at the copolymer surface. This result is in good agreement with the transmission FTIR and ATR-FTIR results but not proportional to them, indicating that the surfaces of the copolymers are highly mobile and that the molecular rearrangement takes place upon contact with a polar liquid drop. The dynamic contact angle measurements showed that the strong acid-base interaction between the oxygen atoms in the copolymer backbone of the relatively more hydrophilic PEG segments with the Lewis acidic groups of the polar and hydrogen-bonding water molecules enabled the surface molecules to restructure (conformational change) at the contact area, so that the PEG segments moved upward, whereas the apolar methyl pendant groups of PLLA segments buried downward.

  6. To Investigate the Absorption, Dynamic Contact Angle and Printability Effects of Synthetic Zeolite Pigments in an Inkjet Receptive Coating

    NASA Astrophysics Data System (ADS)

    Jalindre, Swaraj Sunil

    Ink absorption performance in inkjet receptive coatings containing synthetic zeolite pigments was studied. Coating pigment pore and particle size distribution are the key parameters that influence in modifying media surface properties, thus affecting the rate of ink penetration and drying time (Scholkopf, et al. 2004). The primary objective of this study was: (1) to investigate the synthetic zeolite pigment effects on inkjet ink absorption, dynamic contact angle and printability, and (2) to evaluate these novel synthetic zeolite pigments in replacing the fumed silica pigments in conventional inkjet receptive coatings. In this research study, single pigment coating formulations (in equal P:B ratio) were prepared using microporous synthetic zeolite pigments (5A, Organophilic and 13X) and polyvinyl alcohol (PVOH) binder. The laboratory-coated samples were characterized for absorption, air permeance, roughness, drying time, wettability and print fidelity. Based on the rheological data, it was found that the synthetic zeolite formulated coatings depicted a Newtonian flow behavior at low shear; while the industry accepted fumed silica based coatings displayed a characteristically high pseudoplastic flow behavior. Our coated samples generated using microporous synthetic zeolite pigments produced low absorption, reduced wettability and accelerated ink drying characteristics. These characteristics were caused due to the synthetic zeolite pigments, which resulted in relatively closed surface structure coated samples. The research suggested that no single selected synthetic zeolite coating performed better than the conventional fumed silica based coatings. Experimental data also showed that there was no apparent relationship between synthetic zeolite pigment pore sizes and inkjet ink absorption. For future research, above coated samples should be evaluated for pore size distribution using Mercury Porosimeter, which quantifies surface porosity of coated samples. This presented

  7. Size-dependent contact angle and the wetting and drying transition of a droplet adsorbed onto a spherical substrate: Line-tension effect

    NASA Astrophysics Data System (ADS)

    Iwamatsu, Masao

    2016-10-01

    The size-dependent contact angle and the drying and wetting morphological transition are studied with respect to the volume change for a spherical cap-shaped droplet placed on a spherical substrate. The line-tension effect is included using the rigorous formula for the Helmholtz free energy in the droplet capillary model. A morphological drying transition from a cap-shaped to a spherical droplet occurs when the substrate is hydrophobic and the droplet volume is small, similar to the transition predicted on a flat substrate. In addition, a morphological wetting transition from a cap-shaped to a wrapped spherical droplet occurs for a hydrophilic substrate and a large droplet volume. The contact angle depends on the droplet size: it decreases as the droplet volume increases when the line tension is positive, whereas it increases when the line tension is negative. The spherical droplets and wrapped droplets are stable when the line tension is positive and large.

  8. Determination of the solid surface critical exponent β1 from contact-angle variation on approach to a wetting transition: Cyclohexane/aniline/quartz

    NASA Astrophysics Data System (ADS)

    Pallas, Norman R.

    2016-03-01

    The three-phase contact angle (θ) for the system cyclohexane/aniline/quartz has been measured from drop shapes as a function of temperature on approach to the cyclohexane/aniline upper consolute solution temperature Tc. The experiments employed exacting criteria previously established for thermodynamic-quality measurements at fluid interfaces. A first-order wetting transition from partial wetting to complete wetting was observed at a temperature Tw, 2.12 K below Tc. The contact angle vanishes at Tw, scaling as cos θ ˜ |T - Tc|β1-μ for T < Tw and cos θ = 1.0 for Tw < T < Tc. The experimental results give a value for β1 = 0.74 ± 0.03, in agreement with theoretical calculations. The data clearly rule out higher order contributions to the change in the contact angle near the critical point for this system. These results are in marked contrast to previous measurements on this system from measurements of capillary rise and meniscus curvature.

  9. Determination of the solid surface critical exponent β1 from contact-angle variation on approach to a wetting transition: Cyclohexane/aniline/quartz.

    PubMed

    Pallas, Norman R

    2016-03-21

    The three-phase contact angle (θ) for the system cyclohexane/aniline/quartz has been measured from drop shapes as a function of temperature on approach to the cyclohexane/aniline upper consolute solution temperature Tc. The experiments employed exacting criteria previously established for thermodynamic-quality measurements at fluid interfaces. A first-order wetting transition from partial wetting to complete wetting was observed at a temperature Tw, 2.12 K below Tc. The contact angle vanishes at Tw, scaling as cos θ ∼ |T - Tc|(β1-μ) for T < Tw and cos θ = 1.0 for Tw < T < Tc. The experimental results give a value for β1 = 0.74 ± 0.03, in agreement with theoretical calculations. The data clearly rule out higher order contributions to the change in the contact angle near the critical point for this system. These results are in marked contrast to previous measurements on this system from measurements of capillary rise and meniscus curvature.

  10. 193 nm excimer laser sclerostomy in pseudophakic patients with advanced open angle glaucoma.

    PubMed Central

    Allan, B D; van Saarloos, P P; Cooper, R L; Constable, I J

    1994-01-01

    A modified open mask system incorporating an en face air jet to dry the target area during ablation and a conjunctival plication mechanism, which allows ab externo delivery of the 193 nm excimer laser without prior conjunctival dissection, has been developed to form small bore sclerostomies accurately and atraumatically. Full thickness sclerostomies, and sclerostomies guarded by a smaller internal ostium can be created. A pilot therapeutic trial was conducted in pseudophakic patients with advanced open angle glaucoma. Six full thickness sclerostomies (200 microns and 400 microns diameter) and three guarded sclerostomies were created in nine patients by 193 nm excimer laser ablation (fluence per pulse 400 mJ/cm2, pulse rate 16 Hz, air jet pressure intraocular pressure +25 mm Hg). After 6 months' follow up, intraocular pressure was controlled (< or = 16 mm Hg) in eight of the nine patients (6/9 without medication). Early postoperative complications included hyphaema (trace--2.5 mm) (6/9), temporary fibrinous sclerostomy occlusion (4/9), profound early hypotony (all patients without fibrinous occlusion), and suprachoroidal haemorrhage in one case. Conjunctival laser wounds were self sealing. Small bore laser sclerostomy procedures are functionally equivalent to conventional full thickness procedures, producing early postoperative hypotony, with an increased risk of suprachoroidal haemorrhage in association with this. Further research is required to improve control over internal guarding in excimer laser sclerostomy before clinical trials of this technique can safely proceed. Images PMID:8148335

  11. Derivation of Incident Angle and Sweeping Voltage Design on Advanced Ionospheric Probe onboard FORMOSAT-5

    NASA Astrophysics Data System (ADS)

    Lin, Z. W.; Chao, C. K.; Chang, Y. S.

    2014-12-01

    Advanced Ionospheric Probe (AIP) developed by the National Central University (NCU), Taiwan, has been selected to install on FORMOSAT-5 satellite. It is an all-in-one plasma sensor with the sampling rate up to 8,192 Hz to measure ionospheric plasma concentrations, velocities, and temperatures over a wide range of spatial scales. The design of AIP sensor allows it to sequentially perform as a Retarding Potential Analyzer (RPA), an Ion Drift Meter (IDM), an Ion Trap (IT), or a Planer Langmuir Probe (PLP). Unlike the inherited payload IPEI onboard FORMOSAT-1/ROCSAT-1, the entrance opening of IDM of AIP is circular instead of square shape, causes the difference in the geometry calculation of the projection area. New method is present to obtain the incident angle from the incoming plasma beam. Meanwhile, a set of sweeping voltage pattern is defined to get a better result of plasma parameters from RPA function. Upon the requirement of the mission, several sweeping voltage patterns are designed to fit the specified species of plasma to increase the accuracy in the derivation of ram speed and temperature. A simulation is present to show the fitting result in different assumptions and conditions for each sweeping pattern.

  12. Contact investigations for outbreaks of Mycobacterium tuberculosis: advances through whole genome sequencing.

    PubMed

    Walker, T M; Monk, P; Smith, E Grace; Peto, T E A

    2013-09-01

    The control of tuberculosis depends on the identification and treatment of infectious patients and their contacts, who are currently identified through a combined approach of genotyping and epidemiological investigation. However, epidemiological data are often challenging to obtain, and genotyping data are difficult to interpret without them. Whole genome sequencing (WGS) technology is increasingly affordable, and offers the prospect of identifying plausible transmission events between patients without prior recourse to epidemiological data. We discuss the current approaches to tuberculosis control, and how WGS might advance public health efforts in the future. PMID:23432709

  13. A numerical approach for the direct computation of flows including fluid-solid interaction: Modeling contact angle, film rupture, and dewetting

    NASA Astrophysics Data System (ADS)

    Mahady, K.; Afkhami, S.; Kondic, L.

    2016-06-01

    In this paper, we present a computationally efficient method for including fluid-solid interactions into direct numerical simulations of the Navier-Stokes equations. This method is found to be as powerful as our earlier formulation [K. Mahady et al., "A volume of fluid method for simulating fluid/fluid interfaces in contact with solid boundaries," J. Comput. Phys. 294, 243 (2015)], while outperforming the earlier method in terms of computational efficiency. The performance and efficacy of the presented method are demonstrated by computing contact angles of droplets at equilibrium. Furthermore, we study the instability of films due to destabilizing fluid-solid interactions, and discuss the influence of contact angle and inertial effects on film breakup. In particular, direct simulation results show an increase in the final characteristic length scales when compared to the predictions of a linear stability analysis, suggesting significant influence of nonlinear effects. Our results also show that emerging length scales differ, depending on a number of physical dimensions considered.

  14. Modeling and experimental study of oil/water contact angle on biomimetic micro-parallel-patterned self-cleaning surfaces of selected alloys used in water industry

    NASA Astrophysics Data System (ADS)

    Nickelsen, Simin; Moghadam, Afsaneh Dorri; Ferguson, J. B.; Rohatgi, Pradeep

    2015-10-01

    In the present study, the wetting behavior of surfaces of various common metallic materials used in the water industry including C84400 brass, commercially pure aluminum (99.0% pure), Nickle-Molybdenum alloy (Hastelloy C22), and 316 Stainless Steel prepared by mechanical abrasion and contact angles of several materials after mechanical abrasion were measured. A model to estimate roughness factor, Rf, and fraction of solid/oil interface, ƒso, for surfaces prepared by mechanical abrasion is proposed based on the assumption that abrasive particles acting on a metallic surface would result in scratches parallel to each other and each scratch would have a semi-round cross-section. The model geometrically describes the relation between sandpaper particle size and water/oil contact angle predicted by both the Wenzel and Cassie-Baxter contact type, which can then be used for comparison with experimental data to find which regime is active. Results show that brass and Hastelloy followed Cassie-Baxter behavior, aluminum followed Wenzel behavior and stainless steel exhibited a transition from Wenzel to Cassie-Baxter. Microstructural studies have also been done to rule out effects beyond the Wenzel and Cassie-Baxter theories such as size of structural details.

  15. In-situ surface wettability parameters of submerged in brackish water surfaces derived from captive bubble contact angle studies as indicators of surface condition level

    NASA Astrophysics Data System (ADS)

    Pogorzelski, S. J.; Mazurek, A. Z.; Szczepanska, A.

    2013-06-01

    The characterization of wetting properties (by contact angles) of several undersea artificial (glass plates,) and natural (stones, sand layers, soft-bottom structures, aquatic macrophytes, sediments, and seafloor communities) solid substrata in the Baltic Sea brackish water (Gulf of Gdansk). The studies were performed under laboratory and field conditions using a novel captive bubble air-pipette computer microscope system. A set of the surface wettability parameters: the apparent surface free energy γSV, adhesive layer film pressure Π, work of adhesion WA, and work of spreading WS were determined to quantify the wetting properties of model substrata using the contact angle hysteresis (CAH) approach. The useful technique to measure in situ the contact angle giving reproducible and accurate values of CA turned out to be a captive bubble method, for fully hydrated interfacial layers of highly hydrophilic and porous nature met at seabed (Rodrigues-Valverde et al., 2002). CA measurements revealed mostly hydrophilic nature of the studied solid material (CA < 90°) where the presence of adsorbed organic matter layer or crude oil film covering lead to surface hydrophobization (CA↑, γSV ↓,WA↓, WS more negative). The adhesion of biofouling was correlated both with CAH and the dispersive interaction term γSVd of the total γSV. Monitoring of the artificial substrata of the hydrophilic nature with a CA technique can be used to observe the development of the organisms community i.e., microfouling, and to carry out a comprehensive study of surfaces of the submerged macrophytes (Potamogeton lucens in particular). Since aquatic macrophytes can act as bio-indicators of water chemistry their surface wettability may reflect plant surface erosion and organic matter accumulation state being of particular value in biological assessment of ecosystems status.

  16. Surface modification of Sylgard 184 polydimethylsiloxane by 254 nm excimer radiation and characterization by contact angle goniometry, infrared spectroscopy, atomic force and scanning electron microscopy

    NASA Astrophysics Data System (ADS)

    Waddell, Emanuel A.; Shreeves, Stephen; Carrell, Holly; Perry, Christopher; Reid, Branden A.; McKee, James

    2008-06-01

    The modification of polydimethylsiloxane (PDMS) by narrow band 254 nm excimer radiation under a nitrogen atmosphere was characterized by contact angle goniometry, attenuated total reflectance infrared spectroscopy, atomic force and scanning electron microscopy. UV irradiation results in the formation of the carboxylic acids that influences the wettability of the surface. Continued exposure results in the formation of an inorganic surface (SiO x (1 < x < 2)) which hinders the ability to continually increase the wettability. The continuity of this inorganic layer is disrupted by the formation of surface cracks. These results have implications in the fabrication and chemical modification of microfluidic or micro-electro-mechanical systems.

  17. Application of advanced shearing techniques to the calibration of autocollimators with small angle generators and investigation of error sources.

    PubMed

    Yandayan, T; Geckeler, R D; Aksulu, M; Akgoz, S A; Ozgur, B

    2016-05-01

    The application of advanced error-separating shearing techniques to the precise calibration of autocollimators with Small Angle Generators (SAGs) was carried out for the first time. The experimental realization was achieved using the High Precision Small Angle Generator (HPSAG) of TUBITAK UME under classical dimensional metrology laboratory environmental conditions. The standard uncertainty value of 5 mas (24.2 nrad) reached by classical calibration method was improved to the level of 1.38 mas (6.7 nrad). Shearing techniques, which offer a unique opportunity to separate the errors of devices without recourse to any external standard, were first adapted by Physikalisch-Technische Bundesanstalt (PTB) to the calibration of autocollimators with angle encoders. It has been demonstrated experimentally in a clean room environment using the primary angle standard of PTB (WMT 220). The application of the technique to a different type of angle measurement system extends the range of the shearing technique further and reveals other advantages. For example, the angular scales of the SAGs are based on linear measurement systems (e.g., capacitive nanosensors for the HPSAG). Therefore, SAGs show different systematic errors when compared to angle encoders. In addition to the error-separation of HPSAG and the autocollimator, detailed investigations on error sources were carried out. Apart from determination of the systematic errors of the capacitive sensor used in the HPSAG, it was also demonstrated that the shearing method enables the unique opportunity to characterize other error sources such as errors due to temperature drift in long term measurements. This proves that the shearing technique is a very powerful method for investigating angle measuring systems, for their improvement, and for specifying precautions to be taken during the measurements.

  18. Advanced video extensometer for non-contact, real-time, high-accuracy strain measurement.

    PubMed

    Pan, Bing; Tian, Long

    2016-08-22

    We developed an advanced video extensometer for non-contact, real-time, high-accuracy strain measurement in material testing. In the established video extensometer, a "near perfect and ultra-stable" imaging system, combining the idea of active imaging with a high-quality bilateral telecentric lens, is constructed to acquire high-fidelity video images of the test sample surface, which is invariant to ambient lighting changes and small out-of-plane motions occurred between the object surface and image plane. In addition, an efficient and accurate inverse compositional Gauss-Newton algorithm incorporating a temporal initial guess transfer scheme and a high-accuracy interpolation method is employed to achieve real-time, high-accuracy displacement tracking with negligible bias error. Tensile tests of an aluminum sample and a carbon fiber filament sample were performed to demonstrate the efficiency, repeatability and accuracy of the developed advanced video extensometer. The results indicate that longitudinal and transversal strains can be estimated and plotted at a rate of 117 fps and with a maximum strain error less than 30 microstrains. PMID:27557188

  19. Development and testing of new biologically-based polymers as advanced biocompatible contact lenses

    SciTech Connect

    Bertozzi, Carolyn R.

    2000-06-01

    Nature has evolved complex and elegant materials well suited to fulfill a myriad of functions. Lubricants, structural scaffolds and protective sheaths can all be found in nature, and these provide a rich source of inspiration for the rational design of materials for biomedical applications. Many biological materials are based in some fashion on hydrogels, the crosslinked polymers that absorb and hold water. Biological hydrogels contribute to processes as diverse as mineral nucleation during bone growth and protection and hydration of the cell surface. The carbohydrate layer that coats all living cells, often referred to as the glycocalyx, has hydrogel-like properties that keep cell surfaces well hydrated, segregated from neighboring cells, and resistant to non-specific protein deposition. With the molecular details of cell surface carbohydrates now in hand, adaptation of these structural motifs to synthetic materials is an appealing strategy for improving biocompatibility. The goal of this collaborative project between Prof. Bertozzi's research group, the Center for Advanced Materials at Lawrence Berkeley National Laboratory and Sunsoft Corporation was the design, synthesis and characterization of novel hydrogel polymers for improved soft contact lens materials. Our efforts were motivated by the urgent need for improved materials that allow extended wear, and essential feature for those whose occupation requires the use of contact lenses rather than traditional spectacles. Our strategy was to transplant the chemical features of cell surface molecules into contact lens materials so that they more closely resemble the tissue in which they reside. Specifically, we integrated carbohydrate molecules similar to those found on cell surfaces, and sulfoxide materials inspired by the properties of the carbohydrates, into hydrogels composed of biocompatible and manufacturable substrates. The new materials were characterized with respect to surface and bulk hydrophilicity, and

  20. Ice nucleation properties of mineral dust particles: Determination of onset RHi, IN active fraction, nucleation time-lag, and the effect of active sites on contact angles

    SciTech Connect

    Kulkarni, Gourihar R.; Dobbie, Steven

    2010-01-08

    A newly developed ice nucleation experimental set up was used to investigate the heterogeneous ice nucleation properties of three Saharan and one Spanish dust particle samples. It is observed that the spread in the onset relative humidities with respect to ice (RHi) for Saharan dust particles varies from 104% to 110%, whereas for the Spanish dust from 106% to 110%. The elemental composition analysis shows a prominent Ca feature in the Spanish dust sample which could potentially explain the differences in nucleation threshold. Although spread in the onset RHi for Saharan dust samples were in agreement, their active fractions and nucleation time-lags calculated at various temperature and RHi conditions, for two Saharan dust samples, were not found to be in complete agreement. This could be because of the subtle variation in the elemental composition of the dust samples, and the surface irregularities like steps, cracks, cavities etc. A combination of classical nucleation theory and active site theory is used to understand the importance of these surface irregularities, expressed in terms of active sites, on the nucleability parameter (contact angle) that is widely used in the ice cloud modeling studies. These calculations show that the surface irregularities reduce the contact angle by approximately 10 degrees.

  1. Model calculations on vertical common black equilibrium soap films: the relation of contact angle to Fresnel diffraction patterns from the film-border transition

    SciTech Connect

    Agterof, W.G.M.

    1982-04-01

    The surface tension of a thin liquid (soap) film is often different from that of the bulk solution from which the film is made. This is a consequence of the action of long-range interation forces in the film. In general, 2 forces are considered. The first is the electric double-layer repulsion which is a result of the overlap of the double-layer buildup in the central aqueous core of the film by the ionic detergent molecules at the surfaces. The second is the London-Van der Waals attraction due to the fact that a molecule in the film has a smaller number of other molecules in its interaction sphere than a molecule in the bulk solution. Both forces, which are functions of the thickness of the film, compose the disjoining pressure. From the profiles Fresnel diffraction patterns were calculated and the following conclusions were drawn: (1) they are not very sensitive for the details of the transition region, between a film and its meniscus; (2) for contact angles larger than 16 ft, the results of Princen and Frankel coincide within 5%; and (3) this optical method will not result in reliable contact angles when they are smaller than 10 ft. 22 references.

  2. The effects of oxygen plasma and humidity on surface roughness, water contact angle and hardness of silicon, silicon dioxide and glass

    NASA Astrophysics Data System (ADS)

    Alam, A. U.; Howlader, M. M. R.; Deen, M. J.

    2014-03-01

    For heterogeneous integration in many More-than-Moore applications, surface preparation is the key step to realizing well-bonded multiple substrates for electronics, photonics, fluidics and/or mechanical components without a degradation in performance. Therefore, it is critical to understand how various processing and environmental conditions affect their surface properties. In this paper, we investigate the effects of oxygen plasma and humidity on some key surface properties such as the water contact angle, roughness and hardness of three materials: silicon (Si), silicon dioxide (SiO2) and glass, and their impact on bondability. The low surface roughness, high surface reactivity and high hydrophilicity of Si, SiO2 and glass at lower activation times can result in better bondability. Although, the surface reactivity of plasma-ambient-humidity-treated Si and SiO2 is considerably reduced, their reduction of roughness and increase of hydrophilicity may enable good bonding at low temperature heating due to augmented hydroxyl groups. The decrease of hardness of Si and SiO2 with increased activation time is attributed to higher surface roughness and the formation of amorphous layers of Si. While contact angle and surface roughness results show a correlation with bondability, the role of hardness on bondability requires further investigation.

  3. Review of Advances in Cobb Angle Calculation and Image-Based Modelling Techniques for Spinal Deformities

    NASA Astrophysics Data System (ADS)

    Giannoglou, V.; Stylianidis, E.

    2016-06-01

    Scoliosis is a 3D deformity of the human spinal column that is caused from the bending of the latter, causing pain, aesthetic and respiratory problems. This internal deformation is reflected in the outer shape of the human back. The golden standard for diagnosis and monitoring of scoliosis is the Cobb angle, which refers to the internal curvature of the trunk. This work is the first part of a post-doctoral research, presenting the most important researches that have been done in the field of scoliosis, concerning its digital visualisation, in order to provide a more precise and robust identification and monitoring of scoliosis. The research is divided in four fields, namely, the X-ray processing, the automatic Cobb angle(s) calculation, the 3D modelling of the spine that provides a more accurate representation of the trunk and the reduction of X-ray radiation exposure throughout the monitoring of scoliosis. Despite the fact that many researchers have been working on the field for the last decade at least, there is no reliable and universal tool to automatically calculate the Cobb angle(s) and successfully perform proper 3D modelling of the spinal column that would assist a more accurate detection and monitoring of scoliosis.

  4. Recent advancements of wide-angle polarization analysis with 3He neutron spin filters

    NASA Astrophysics Data System (ADS)

    Chen, W. C.; Gentile, T. R.; Ye, Q.; Kirchhoff, A.; Watson, S. M.; Rodriguez-Rivera, J. A.; Qiu, Y.; Broholm, C.

    2016-09-01

    Wide-angle polarization analysis with polarized 3He based neutron spin filters (NSFs) has recently been employed on the Multi-Axis Crystal Spectrometer (MACS) at the National Institute of Standards and Technology Center for Neutron Research (NCNR). Over the past several years, the apparatus has undergone many upgrades to address the fundamental requirements for wide angle polarization analysis using spin exchange optical pumping based 3He NSFs. In this paper, we report substantial improvements in the on-beam-line performance of the apparatus and progress toward routine user capability. We discuss new standard samples used for 3He NSF characterization and the flipping ratio measurement on MACS. We further discuss the management of stray magnetic fields produced by operation of superconducting magnets on the MACS instrument, which can significantly reduce the 3He polarization relaxation time. Finally, we present the results of recent development of horseshoe-shaped wide angle cells.

  5. The combined effect of frontal plane tibiofemoral knee angle and meniscectomy on the cartilage contact stresses and strains.

    PubMed

    Yang, Nicholas; Nayeb-Hashemi, Hamid; Canavan, Paul K

    2009-11-01

    Abnormal tibiofemoral alignment can create loading conditions at the knee that may lead to the initiation and progression of knee osteoarthritis (OA). The degenerative changes of the articular cartilage may occur earlier and with greater severity in individuals with abnormal frontal plane tibiofemoral alignment who undergo a partial or total meniscectomy. In this investigation, subject specific 3D finite element knee models were created from magnetic resonance images of two female subjects to study the combined effect of frontal plane tibiofemoral alignment and total and partial meniscectomy on the stress and strain at the knee cartilage. Different amounts of medial and lateral meniscectomies were modeled and subject specific loading conditions were determined from motion analysis and force platform data during single-leg support. The results showed that the maximum stresses and strains occurred on the medial tibial cartilage after medial meniscectomy but a greater percentage change in the contact stresses and strains occurred in the lateral cartilage after lateral meniscectomy for both subjects due to the resultant greater load bearing role of the lateral meniscus. The results indicate that individual's frontal plane knee alignment and their unique local force distribution between the cartilage and meniscus play an important role in the biomechanical effects of total and partial meniscectomy.

  6. The Effects of Void Geometry and Contact Angle on the Absorption of Liquids into Porous Calcium Carbonate Structures.

    PubMed

    Ridgway, Cathy J.; Schoelkopf, Joachim; Matthews, G. Peter; Gane, Patrick A. C.; James, Philip W.

    2001-07-15

    The absorption (permeation) of alcohols into porous blocks of calcium carbonate has been studied experimentally and with a computer model. The experimental measurement was of change in apparent weight of a block with time after contact with liquid. The modeling used the previously developed 'Pore-Cor' model, based on unit cells of 1000 cubic pores connected by cylindrical throats. To gain some insight into absorption into voids of complex geometry, and to provide a representation of heterogeneities in surface interaction energy, the cylindrical throats were converted to double cones. Relative to cylinders, such geometries caused hold-ups of the percolation of nonwetting fluids with respect to increasing applied pressure, and a change in the rate of absorption of wetting fluids. Both the measured absorption of the alcohols and the simulated absorption of the alcohols and of water showed significant deviations from that predicted by an effective hydraulic radius approximation. The simulation demonstrated the development of a highly heterogeneous wetting front, and of preferred wetting pathways that were perturbed by inertial retardation. The findings are useful in the design of high-performance, low-waste pigments for paper coatings, and environmentally friendly printing inks, as well as in wider industrial, environmental, and geological contexts. Copyright 2001 Academic Press.

  7. Plasma and laser kinetics and field emission from carbon nanotube fibers for an Advanced Noble Gas Laser (ANGL)

    NASA Astrophysics Data System (ADS)

    Moran, Paul J.; Lockwood, Nathaniel P.; Lange, Matthew A.; Hostutler, David A.; Guild, Eric M.; Guy, Matthew R.; McCord, John E.; Pitz, Greg A.

    2016-03-01

    A metastable argon laser operating at 912 nm has been demonstrated by optically pumping with a pulsed titanium sapphire laser to investigate the temporal dynamics of an Advanced Noble Gas Laser (ANGL). Metastable argon concentrations on the order of 1011 cm-3 were maintained with the use of a radio frequency (RF) capacitively coupled discharge. The end-pumped laser produced output powers under 2 mW of average power with pulse lengths on the order of 100 ns. A comparison between empirical results and a four level laser model using longitudinally average pump and inter-cavity intensities is made. An alternative, highly-efficient method of argon metastable production for ANGL was explored using carbon nanotube (CNT) fibers.

  8. The Effect of Contact Angles and Capillary Dimensions on the Burst Frequency of Super Hydrophilic and Hydrophilic Centrifugal Microfluidic Platforms, a CFD Study

    PubMed Central

    Kazemzadeh, Amin; Ganesan, Poo; Ibrahim, Fatimah; He, Shuisheng; Madou, Marc J.

    2013-01-01

    This paper employs the volume of fluid (VOF) method to numerically investigate the effect of the width, height, and contact angles on burst frequencies of super hydrophilic and hydrophilic capillary valves in centrifugal microfluidic systems. Existing experimental results in the literature have been used to validate the implementation of the numerical method. The performance of capillary valves in the rectangular and the circular microfluidic structures on super hydrophilic centrifugal microfluidic platforms is studied. The numerical results are also compared with the existing theoretical models and the differences are discussed. Our experimental and computed results show a minimum burst frequency occurring at square capillaries and this result is useful for designing and developing more sophisticated networks of capillary valves. It also predicts that in super hydrophilic microfluidics, the fluid leaks consistently from the capillary valve at low pressures which can disrupt the biomedical procedures in centrifugal microfluidic platforms. PMID:24069169

  9. Systematic Oxidation of Polystyrene by Ultraviolet-Ozone, Characterized by Near-Edge X-ray Absorption Fine Structure and Contact Angle

    SciTech Connect

    Klein,R.; Fischer, D.; Lenhart, J.

    2008-01-01

    The process of implanting oxygen in polystyrene (PS) via exposure to ultraviolet-ozone (UV-O) was systematically investigated using the characterization technique of near-edge X-ray absorption fine structure (NEXAFS). Samples of PS exposed to UV-O for 10-300 s and washed with isopropanol were analyzed using the carbon and oxygen K-edge NEXAFS partial electron yields, using various retarding bias voltages to depth-profile the oxygen penetration into the surface. Evaluation of reference polymers provided a scale to quantify the oxygen concentration implanted by UV-O treatment. We find that ozone initially reacts with the double bonds on the phenyl rings, forming carbonyl groups, but within 1 min of exposure, the ratio of double to single oxygen bonds stabilizes at a lower value. Oxygen penetrates the film with relative ease, creating a fairly uniform distribution of oxygen within at least the first 4 nm (the effective depth probed by NEXAFS here). Before oxygen accumulates in large concentrations, however, it preferentially degrades the uppermost layer of the film by removing oxygenated low-molecular-weight oligomers. The failure to accumulate high concentrations of oxygen is seen in the nearly constant carbon edge jump, the low concentration of oxygen even at 5 min exposure (58% of that in poly(4-acetoxystyrene), the polymer with the most similarities to UV-O-treated PS), and the relatively high contact angles. At 5 min exposure the oxygen concentration contains ca. 7 atomic % oxygen. The oxygen species that are implanted consist predominantly of single O-C bonds and double OC bonds but also include a small fraction of O-H. UV-O treatment leads a plateau after 2 min exposure in the water contact angle hysteresis, at a value of 67 {+-} 2, due primarily to chemical heterogeneity. Annealing above Tg allows oxygenated species to move short distances away from the surface but not diffuse further than 1-2 nm.

  10. Simultaneous decay of contact-angle and surface-tension during the rehydration of air-dried root mucilage

    NASA Astrophysics Data System (ADS)

    Arye, Gilboa; Chen, Fengxian

    2016-04-01

    Plants can extract or exude water and solutes at their root surface. Among the root exudates, the mucilage exhibits a surfactant like properties - depressing the surface-tension (ST, mN/m) at the water-air interface. The amphipathic nature of some of the mucilage molecules (e.g. lipids) is thought to be the reason for its surfactant like behavior. As the rhizosphere dries out, re-orientation and/or re-configuration of amphipathic molecules at the solid-air interface, may impart hydrophobic nature to the rhizosphere. Our current knowledge on the ST of natural and/or model root mucilage is based on measurements of the equilibrium ST. However, adsorption of amphipathic molecules at the water-air interface is not reached instantaneously. The hydrophobic nature of the rhizosphere was deduced from the initial advancing CA, commonly calculated from the first few milliseconds up to few seconds (depending on the method employed). We hypothesized that during the rehydration of the root mucilage; both quantities are dynamic. Processes such as water absorbance and dissolution, may vary the interfacial tensions as a function of time. Consequently, simultaneous reduction of both CA and ST as a function of time can be expected. The main objective of this study was to characterize and quantify the extent, persistency and dynamic of the CA and ST during rehydration of air-dried root mucilage. The study was involved with measurements of dynamic and equilibrium ST using the pedant drop or Wilhelmy plate method, respectively. Glass slides were coated with naturally occurring or model root mucilage and the CA of a sessile drop was measured optically, as a function of time. The results were analyzed based on the Young-Dupré and Young-Laplace equations, from which the simultaneous decay of CA and ST was deduced. The implication for the wettability and water flow in the rhizosphere will be discussed.

  11. Nanorods of Co/Pd multilayers fabricated by glancing angle deposition for advanced media

    SciTech Connect

    Su, Hao; Gupta, Subhadra; Natarajarathinam, Anusha

    2013-05-28

    Perpendicular anisotropy magnetic nanorods composed of Co/Pd multilayers have been successfully fabricated by glancing angle deposition (GLAD) in a planetary sputtering system. Co and Pd layer thickness, ratio, and bilayer number were optimized for both normal and GLAD depositions. Scanning electron micrographs estimated the nanorods to be about 12 nm in diameter. M-H loops showed that the coercivity for the GLAD nanorods increased from 1.3 kOe for the normally deposited continuous films to 2.9 kOe for the GLAD nanorod array, a 123% increase.

  12. Advanced slow-magic angle spinning probe for magnetic resonance imaging and spectroscopy

    DOEpatents

    Wind, Robert A.; Hu, Jian Zhi; Minard, Kevin R.; Rommereim, Donald N.

    2006-01-24

    The present invention relates to a probe and processes useful for magnetic resonance imaging and spectroscopy instruments. More particularly, the invention relates to a MR probe and processes for obtaining resolution enhancements of fluid objects, including live specimens, using an ultra-slow (magic angle) spinning (MAS) of the specimen combined with a modified phase-corrected magic angle turning (PHORMAT) pulse sequence. Proton NMR spectra were measured of the torso and the top part of the belly of a female BALBc mouse in a 2T field, while spinning the animal at a speed of 1.5 Hz. Results show that even in this relatively low field with PHORMAT, an isotropic spectrum is obtained with line widths that are a factor 4.6 smaller than those obtained in a stationary mouse. Resolution of 1H NMR metabolite spectra are thus significantly enhanced. Results indicate that PHORMAT has the potential to significantly increase the utility of 1H NMR spectroscopy for in vivo biochemical, biomedical and/or medical applications involving large-sized biological objects such as mice, rats and even humans within a hospital setting. For small-sized objects, including biological objects, such as excised tissues, organs, live bacterial cells, and biofilms, use of PASS at a spinning rate of 30 Hz and above is preferred.

  13. On the theory for the arrest of an advancing molten contact line on a cold solid of the same material

    NASA Astrophysics Data System (ADS)

    Schiaffino, Stefano; Sonin, Ain A.

    1997-08-01

    We show that a conventional continuum formulation of the equations and boundary conditions for the spreading of a pure molten material over a cold, solid substrate of its own kind has no meaningful solution for the angle of attack θs of the fusion front at the contact line, which is the quantity that determines contact-line arrest. θs is determined by the heat flux just behind the contact line, and the heat flux in the mathematical model is singular at the contact line. The scale of the physical mechanism which limits the heat flux at the contact line and removes the singularity is estimated by computing the point where the continuum model must be cut off in order to bring it into agreement with the experimental data for a microcrystalline wax. The cutoff scale is in the range 0.1-1 μm, that is, much larger than molecular dimensions, but of order 10-2-10-1 times the convective thermal length scale α/U.

  14. Enabling the 14nm node contact patterning using advanced RET solutions

    NASA Astrophysics Data System (ADS)

    Zeggaoui, N.; Landie, G.; Villaret, A.; Farys, V.; Yesilada, E.; Tritchkov, A.; Word, J.

    2015-09-01

    The 14nm node designs is getting more sophisticated, and printability issues become more critical which need more advanced techniques to fix. One of the most critical processes is the contact patterning due to the very aggressive design rules and the process window which becomes quickly limited. Despite the large number of RET applied, some hotspot configurations remain challenging. It becomes increasingly challenging to achieve sufficient process windows around the hot spots just using conventional process such as OPC and rule-based SRAF insertion. Although, it might be desirable to apply Inverse Lithography Technique (ILT) on all hot spots to guarantee ideal mask quality. However, because of the high number of hot spots to repair in the design, that solution might be much time consuming in term of OPC and mask processing. In this paper we present a hybrid OPC solution based on local ILT usage around hot spots. It is named as Local Printability Enhancement (LPE) flow. First, conventional OPC and SRAF placement is applied on the whole design. Then, we apply LPE solution only on the remaining problematic hot spots of the design. The LPE flow also takes into account the mask rules so that it maintains the mask rule check (MRC) compliance through the borders of the repaired hot spot's areas. We will demonstrate that the LPE flow enlarges the process window around hot spots and gives better lithography quality than baseline. The simulation results are confirmed on silicon wafer where all the hot spots are printed. We will demonstrate that LPE flow enlarges the depth of focus of the most challenging hot spot by 30nm compared to POR conventional solution. Because the proposed flow applies ILT solution on very local hot spot areas, the total OPC run time remains acceptable from manufacturing side.

  15. Advancement of the Wide-angle JEM-EUSO Optical System with Holographic and Fresnel Lenses

    NASA Technical Reports Server (NTRS)

    Takizawa, Y.; Adams, J.H.

    2007-01-01

    JEM-EUSO is a space mission to observe extremely high-energy cosmic rays, evolved from the previous design studies of EUSO. It is adjusted for the Japan Experiment Module (JEM) of the International Space Station (ISS). JEM-EUSO uses a wide-angle refractive telescope in near-ultraviolet wavelength region to observe from ISS the time-and-space-resolved atmospheric fluorescence images of the extensive air showers. The JEM-EUSO optics is re-designed after the ESA-Phase A studies to upgrade the light-collecting-power by using a new material CYTOP, and its overall light-collecting power is about 1.5 times higher than the ESA-Phase A baseline optics. We describe in this paper an optimized optics design that maximizes the sensitivity of JEM-EUSO, and the results of the optics manufacturing tests.

  16. Selective laser trabeculoplasty in treating post-trabeculectomy advanced primary open-angle glaucoma

    PubMed Central

    ZHANG, HONGYANG; YANG, YANGFAN; XU, JIANGANG; YU, MINBIN

    2016-01-01

    The aim of this study was to investigate the safety and efficacy of selective laser trabeculoplasty (SLT) treatment of patients with primary open-angle glaucoma (POAG) who could not obtain target intraocular pressure (IOP) through post-trabeculectomy medication. Sixteen patients with POAG (18 eyes), who could not obtain target IOP following medication and surgery, were treated with 360° SLT. The IOP, anterior chamber inflammation, and daytime and long-term IOP fluctuations before and 2 h, 1 day, 7 days, 1 month, 3 months, 6 months and 9 months after SLT were documented. SLT treatment success was defined as >20% IOP reduction compared with the baseline IOP at 6 and 9 months after the laser treatment date. Prior to SLT, the patients were administered different types (average, 2.8±0.8) of anti-glaucoma drugs and had an average IOP of 21.3±3.4 mmHg. Following SLT, the average IOP decreased to 16.2±3.0 mmHg and the success rate was 77.7%. The pre-SLT daytime IOP fluctuation was 4.1±1.4 mmHg, which decreased to 2.6±1.1 mmHg following the laser treatment (P<0.05). In conclusion, this study demonstrated that SLT could reduce the IOP in post-trabeculectomy patients with POAG, and reduce the daytime IOP fluctuations. PMID:26998042

  17. Systematic oxidation of polystyrene by ultraviolet-ozone, characterized by near-edge X-ray absorption fine structure and contact angle.

    PubMed

    Klein, Robert J; Fischer, Daniel A; Lenhart, Joseph L

    2008-08-01

    The process of implanting oxygen in polystyrene (PS) via exposure to ultraviolet-ozone (UV-O) was systematically investigated using the characterization technique of near-edge X-ray absorption fine structure (NEXAFS). Samples of PS exposed to UV-O for 10-300 s and washed with isopropanol were analyzed using the carbon and oxygen K-edge NEXAFS partial electron yields, using various retarding bias voltages to depth-profile the oxygen penetration into the surface. Evaluation of reference polymers provided a scale to quantify the oxygen concentration implanted by UV-O treatment. We find that ozone initially reacts with the double bonds on the phenyl rings, forming carbonyl groups, but within 1 min of exposure, the ratio of double to single oxygen bonds stabilizes at a lower value. Oxygen penetrates the film with relative ease, creating a fairly uniform distribution of oxygen within at least the first 4 nm (the effective depth probed by NEXAFS here). Before oxygen accumulates in large concentrations, however, it preferentially degrades the uppermost layer of the film by removing oxygenated low-molecular-weight oligomers. The failure to accumulate high concentrations of oxygen is seen in the nearly constant carbon edge jump, the low concentration of oxygen even at 5 min exposure (58% of that in poly(4-acetoxystyrene), the polymer with the most similarities to UV-O-treated PS), and the relatively high contact angles. At 5 min exposure the oxygen concentration contains ca. 7 atomic % oxygen. The oxygen species that are implanted consist predominantly of single O-C bonds and double O=C bonds but also include a small fraction of O-H. UV-O treatment leads a plateau after 2 min exposure in the water contact angle hysteresis, at a value of 67 +/- 2 degrees , due primarily to chemical heterogeneity. Annealing above T(g) allows oxygenated species to move short distances away from the surface but not diffuse further than 1-2 nm.

  18. Comparison of advanced and intermediate 200-m backstroke swimmers' dominant and non-dominant shoulder entry angles across various swimming speeds.

    PubMed

    Andrews, Claire; Bakewell, James; Scurr, Joanna C

    2011-04-01

    During backstroke, an optimum shoulder entry angle of 180° has been anecdotally suggested; however, this has yet to be investigated biomechanically. The aim of this study was to quantify shoulder entry angles for advanced and intermediate backstroke swimmers. Six advanced (season's best <150 s) and six intermediate (season's best >160 s) 200-m backstroke swimmers had markers applied to the medial humeral epicondyles and glenoid cavities. Following a familarization period, participants completed backstroke swimming trials (90 s each) in a swimming flume at 50%, 60%, 70%, and 80% of their season's best 200-m velocity. A camera positioned above the flume recorded frontal plane motion, which was digitized and analysed in Simi Motion Systems. The mean peak angle between the upper arm and the line of progression was established in ten strokes for each participant. The results showed backstroke shoulder entry angles for advanced swimmers (170°) were significantly closer to the suggested optimum 180° compared with those of intermediate swimmers (161°). The non-dominant arm displayed values closer to the optimum (171°), while swimming speed had no effect on backstroke shoulder entry angle. In conclusion, backstroke shoulder entry angle may help discriminate between advanced and intermediate backstroke swimmers and may be influenced by laterality dominance, being independent of swimming speed. PMID:21416447

  19. Increase in the water contact angle of composite film surfaces caused by the assembly of hydrophilic nanocellulose fibrils and nanoclay platelets.

    PubMed

    Wu, Chun-Nan; Saito, Tsuguyuki; Yang, Quanling; Fukuzumi, Hayaka; Isogai, Akira

    2014-08-13

    Controlling the assembly modes of different crystalline nanoparticles in composites is important for the expression of specific characteristics of the assembled structures. We report a unique procedure for increasing water contact angles (CAs) of composite film surfaces via the assembly of two different hydrophilic components, nanocellulose fibrils and nanoclay platelets. The nanocellulose fibrils and nanoclay platelets used have ionic groups on their surfaces in high densities (∼1 mmol g(-1)) and have no hydrophobic surface. The increase in the CA of the nanocellulose/nanoclay composite films was thus analyzed on the basis of the air area fractions of their nanostructured surfaces following Cassie's law. The air area fractions were geographically estimated from the atomic force microscopy height profiles of the composite film surfaces. The CAs of the composite film surfaces were found to be well described by Cassie's law. Interestingly, the composite films consisting of two hydrophilic nanoelements with different shapes exhibited CAs larger than those of the individual neat films. PMID:24977651

  20. Angle dependence on the anisotropic magnetoresistance amplitude of a single-contacted Ni nanowire subjected to a thermo-mechanical strain

    NASA Astrophysics Data System (ADS)

    Melilli, G.; Madon, B.; Wegrowe, J.-E.; Clochard, M.-C.

    2015-12-01

    The effects of thermoelastic and piezoelectric strain of an active track-etched β-PVDF polymer matrix on an electrodeposited single-contacted Ni nanowire (NW) are investigated at the nanoscale by measuring the change of magnetization (i.e. using the inverse magnetostriction effect). The magnetization state is measured locally by anisotropic magnetoresistance (AMR). The ferromagnetic NW plays thus the role of a mechanical probe that allows the effects of mechanical strain to be characterized and described qualitatively and quantitatively. The inverse magnetostriction was found to be responsible for a quasi-disappearance of the AMR signal for a variation of the order of ΔT ≈ 10 K. In other terms, the variation of the magnetization due to the stress compensates the effect of external magnetic field applied on the NW resistance. The induced stress field in a single Ni NW was found 1000 time higher than the bulk stress field (due to thermal expansion measured on the PVDF). This amplification could be attributed to three nanoscopic effects: (1) a stress mismatch between the Ni NW and the membrane, (2) a non-negligible role of the surface tension on Ni NW Young modulus, and (3) the possibility of non-linear stress-strain law. We investigate here the role of these different contributions using track-etched polymer membranes irradiated at various angles (αirrad) leading to, after electrodeposition, embedded Ni NWs of different orientations.

  1. Contact allergy to topical medicaments becomes more common with advancing age: an age-stratified study.

    PubMed

    Green, Carl M; Holden, Catherine R; Gawkrodger, David J

    2007-04-01

    Eczema is common in the elderly people who often use topical medicaments. Previous studies in the elderly people have noted allergic positive patch tests in between 43% and 64% of those tested. We set out to assess whether medicament contact allergies are more common in elderly patients. We undertook a retrospective age-stratified study of all patients patch tested at the Royal Hallamshire Hospital, Sheffield, between January 1994 and July 2005. We confirmed that contact allergy to topical medicaments is more common in those aged more than 70 years compared with the younger age groups. There was no sex difference. The commonest problematic allergen types found in medicaments were fragrances and preservatives. The most frequent individual allergens were fragrance mix, Myroxylon pereirae, lanolins, local anaesthetic agents, neomycin and gentamicin, and tixocortol pivolate. The pattern of medicament contact allergens was similar to that of the younger age groups except that multiple allergic positives were more frequent and sensitivities to local anaesthetics and Myroxylon pereirae were proportionally more common. Elderly patients were more likely to have multiple contact allergies than the younger ones. Care needs to be taken when prescribing topical medicaments to elderly patients with eczema, especially for preparations that contain perfumes, lanolins, and local anaesthetics.

  2. Evaluation of advanced microelectronic fluxless solder-bump contacts for hybrid microcircuits

    NASA Technical Reports Server (NTRS)

    Mandal, R. P.

    1976-01-01

    Technology for interconnecting monolithic integrated circuit chips with other components is investigated. The advantages and disadvantages of the current flip-chip approach as compared to other interconnection methods are outlined. A fluxless solder-bump contact technology is evaluated. Multiple solder-bump contacts were formed on silicon integrated circuit chips. The solder-bumps, comprised of a rigid nickel under layer and a compliant solder overlayer, were electroformed onto gold device pads with the aid of thick dry film photomasks. Different solder alloys and the use of conductive epoxy for bonding were explored. Fluxless solder-bump bond quality and reliability were evaluated by measuring the effects of centrifuge, thermal cycling, and high temperature storage on bond visual characteristics, bond electrical continuity, and bond shear tests. The applicability and suitability of this technology for hybrid microelectronic packaging is discussed.

  3. Some Effects of Injection Advance Angle, Engine-Jacket Temperature, and Speed on Combustion in a Compression-Ignition Engine

    NASA Technical Reports Server (NTRS)

    Rothrock, A M; Waldron, C D

    1936-01-01

    An optical indicator and a high-speed motion-picture camera capable of operating at the rate of 2,000 frames per second were used to record simultaneously the pressure development and the flame formation in the combustion chamber of the NACA combustion apparatus. Tests were made at engine speeds of 570 and 1,500 r.p.m. The engine-jacket temperature was varied from 100 degrees to 300 degrees F. And the injection advance angle from 13 degrees after top center to 120 degrees before top center. The results show that the course of the combustion is largely controlled by the temperature and pressure of the air in the chamber from the time the fuel is injected until the time at which combustion starts and by the ignition lag. The conclusion is presented that in a compression-ignition engine with a quiescent combustion chamber the ignition lag should be the longest that can be used without excessive rates of pressure rise; any further shortening of the ignition lag decreased the effective combustion of the engine.

  4. Studies of dynamic contact of ceramics and alloys for advanced heat engines. Final report

    SciTech Connect

    Gaydos, P.A.; Dufrane, K.F.

    1993-06-01

    Advanced materials and coatings for low heat rejection engines have been investigated for almost a decade. Much of the work has concentrated on the critical wear interface between the piston ring and cylinder liner. Simplified bench tests have identified families of coatings with high temperature wear performance that could meet or exceed that of conventional engine materials at today`s operating temperatures. More recently, engine manufacturers have begun to optimize material combinations and manufacturing processes so that the materials not only have promising friction and wear performance but are practical replacements for current materials from a materials and manufacturing cost standpoint. In this study, the advanced materials supplied by major diesel engine manufacturers were evaluated in an experimental apparatus that simulates many of the in-cylinder conditions of a low heat rejection diesel engine. Results include ring wear factors and average dynamic friction coefficients measured at intervals during the test. These results are compared with other advanced materials tested in the past as well as the baseline wear of current engines. Both fabricated specimens and sections of actual ring and cylinder liners were used in the testing. Observations and relative friction and wear performance of the individual materials are provided.

  5. Modern methods for investigating functional surfaces of advanced materials by mechanical contact testing

    NASA Astrophysics Data System (ADS)

    Petrzhik, M. I.; Levashov, E. A.

    2007-11-01

    Modern methods for determining the hardness, Young’s modulus, elastic recovery, adhesive/cohesive strength, friction coefficient, and wear resistance of thin films, coatings, multilayer materials, and bulk materials are considered. The experimental data obtained in instrumented indentation, instrumented scratching, and tribological tests of nanostructured and quasicrystalline coatings and composite materials are analyzed. It is noted that the elastic recovery of a number of advanced materials is higher than the elastic recovery of metal alloys by a factor of 2-3. The coefficients of sliding friction of sintered samples and thin films containing Al-Cu-Fe quasicrystals are found to be relatively low. An increase in the fraction of quasicrystalline particles to 30% in composites with an aluminum matrix leads to an increase in the wear resistance.

  6. Process Knowledge Summary Report for Advanced Test Reactor Complex Contact-Handled Transuranic Waste Drum TRA010029

    SciTech Connect

    B. R. Adams; R. P. Grant; P. R. Smith; J. L. Weisgerber

    2013-09-01

    This Process Knowledge Summary Report summarizes information collected to satisfy the transportation and waste acceptance requirements for the transfer of one drum containing contact-handled transuranic (TRU) actinide standards generated by the Idaho National Laboratory at the Advanced Test Reactor (ATR) Complex to the Advanced Mixed Waste Treatment Project (AMWTP) for storage and subsequent shipment to the Waste Isolation Pilot Plant for final disposal. The drum (i.e., Integrated Waste Tracking System Bar Code Number TRA010029) is currently stored at the Materials and Fuels Complex. The information collected includes documentation that addresses the requirements for AMWTP and applicable sections of their Resource Conservation and Recovery Act permits for receipt and disposal of this TRU waste generated from ATR. This Process Knowledge Summary Report includes information regarding, but not limited to, the generation process, the physical form, radiological characteristics, and chemical contaminants of the TRU waste, prohibited items, and packaging configuration. This report, along with the referenced supporting documents, will create a defensible and auditable record for this TRU waste originating from ATR.

  7. How Water Advances on Superhydrophobic Surfaces

    NASA Astrophysics Data System (ADS)

    Schellenberger, Frank; Encinas, Noemí; Vollmer, Doris; Butt, Hans-Jürgen

    2016-03-01

    Superliquid repellency can be achieved by nano- and microstructuring surfaces in such a way that protrusions entrap air underneath the liquid. It is still not known how the three-phase contact line advances on such structured surfaces. In contrast to a smooth surface, where the contact line can advance continuously, on a superliquid-repellent surface, the contact line has to overcome an air gap between protrusions. Here, we apply laser scanning confocal microscopy to get the first microscopic videos of water drops advancing on a superhydrophobic array of micropillars. In contrast to common belief, the liquid surface gradually bends down until it touches the top face of the next micropillars. The apparent advancing contact angle is 180°. On the receding side, pinning to the top faces of the micropillars determines the apparent receding contact angle. Based on these observations, we propose that the apparent receding contact angle should be used for characterizing superliquid-repellent surfaces rather than the apparent advancing contact angle and hysteresis.

  8. Jointed magnetic skyrmion lattices at a small-angle grain boundary directly visualized by advanced electron microscopy

    PubMed Central

    Matsumoto, Takao; So, Yeong-Gi; Kohno, Yuji; Sawada, Hidetaka; Ishikawa, Ryo; Ikuhara, Yuichi; Shibata, Naoya

    2016-01-01

    The interactions between magnetic skyrmions and structural defects, such as edges, dislocations, and grain boundaries (GBs), which are all considered as topological defects, will be important issues when magnetic skyrmions are utilized for future memory device applications. To investigate such interactions, simultaneous visualization of magnetic skyrmions and structural defects at high spatial resolution, which is not feasible by conventional techniques, is essential. Here, taking advantages of aberration-corrected differential phase-contrast scanning transmission electron microscopy, we investigate the interaction of magnetic skyrmions with a small-angle GB in a thin film of FeGe1−xSix. We found that the magnetic skyrmions and the small-angle GB can coexist each other, but a domain boundary (DB) was formed in the skyrmion lattice along the small-angle GB. At the core of the DB, unexpectedly deformed magnetic skrymions, which appear to be created by joining two portions of magnetic skyrmions in the adjacent lattices, were formed to effectively compensate misorientations between the two adjacent magnetic skyrmion lattices. These observations strongly suggest the flexible nature of individual magnetic skyrmions, and also the significance of defect engineering for future device applications. PMID:27775056

  9. The Apparent Contact Angle and Wetted Area of Active Alloys on Silicon Carbide as a Function of the Temperature and the Surface Roughness: A Multivariate Approach

    NASA Astrophysics Data System (ADS)

    Tillmann, Wolfgang; Pfeiffer, Jan; Wojarski, Lukas

    2015-08-01

    Despite the broad field of applications for active filler alloys for brazing ceramics, as well as intense research work on the wetting and spreading behavior of these alloys on ceramic surfaces within the last decades, the manufactured joints still exhibit significant variations in their properties due to the high sensitivity of the alloys to changing brazing conditions. This increases the need for investigations of the wetting and spreading behavior of filler alloys with regard to the dominating influences combined with their interdependencies, instead of solely focusing on single parameter investigations. In this regard, measurements of the wetting angle and area were conducted at solidified AgCuTi and CuSnTi alloys on SiC substrates. Based on these measurements, a regression model was generated, illustrating the influence of the brazing temperature, the roughness of the faying surfaces, the furnace atmosphere, and their interdependencies on the wetting and spreading behavior of the filler alloys. It was revealed that the behavior of the melts was significantly influenced by the varied brazing parameters, as well as by their interdependencies. This result was also predicted by the developed model and showed a high accuracy.

  10. Dynamics of the Molten Contact Line

    NASA Technical Reports Server (NTRS)

    Sonin, Ain A.; Schiaffino, Stefano

    1996-01-01

    In contrast to the ordinary contact line problem, virtually no information is available on the similar problem associated with a molten material spreading on a solid which is below the melt's fusion point. The latter is a more complex problem which heat transfer and solidification take place simultaneously with spreading, and requires answers not only for the hot melt's advance speed over the cold solid as a function of contact angle, but also for how one is to predict the point of the molten contact line's arrest by freezing. This issues are of importance in evolving methods of materials processing. The purpose of our work is to develop, based on both experiments and theory, an understanding of the dynamic processes that occur when a molten droplet touches a subcooled solid, spreads partly over it by capillary action, and freezes. We seek answers to the following basic questions. First, what is the relationship between the melt's contact line speed and the apparent (dynamic) contact angle? Secondly, at what point will the contact line modon be arrested by freezing? The talk will describe three components of our work: (1) deposition experiments with small molten droplets; (2) investigation of the dynamics of the molten contact line by means of a novel forced spreading method; and (3) an attempt to provide a theoretical framework for answering the basic questions posed above.

  11. Measurement of Systemic Mitochondrial Function in Advanced Primary Open-Angle Glaucoma and Leber Hereditary Optic Neuropathy.

    PubMed

    Van Bergen, Nicole J; Crowston, Jonathan G; Craig, Jamie E; Burdon, Kathryn P; Kearns, Lisa S; Sharma, Shiwani; Hewitt, Alex W; Mackey, David A; Trounce, Ian A

    2015-01-01

    Primary Open Angle Glaucoma (POAG) is a common neurodegenerative disease characterized by the selective and gradual loss of retinal ganglion cells (RGCs). Aging and increased intraocular pressure (IOP) are glaucoma risk factors; nevertheless patients deteriorate at all levels of IOP, implying other causative factors. Recent evidence presents mitochondrial oxidative phosphorylation (OXPHOS) complex-I impairments in POAG. Leber Hereditary Optic Neuropathy (LHON) patients suffer specific and rapid loss of RGCs, predominantly in young adult males, due to complex-I mutations in the mitochondrial genome. This study directly compares the degree of OXPHOS impairment in POAG and LHON patients, testing the hypothesis that the milder clinical disease in POAG is due to a milder complex-I impairment. To assess overall mitochondrial capacity, cells can be forced to produce ATP primarily from mitochondrial OXPHOS by switching the media carbon source to galactose. Under these conditions POAG lymphoblasts grew 1.47 times slower than controls, whilst LHON lymphoblasts demonstrated a greater degree of growth impairment (2.35 times slower). Complex-I enzyme specific activity was reduced by 18% in POAG lymphoblasts and by 29% in LHON lymphoblasts. We also assessed complex-I ATP synthesis, which was 19% decreased in POAG patients and 17% decreased in LHON patients. This study demonstrates both POAG and LHON lymphoblasts have impaired complex-I, and in the majority of aspects the functional defects in POAG were milder than LHON, which could reflect the milder disease development of POAG. This new evidence places POAG in the spectrum of mitochondrial optic neuropathies and raises the possibility for new therapeutic targets aimed at improving mitochondrial function.

  12. Measurement of Systemic Mitochondrial Function in Advanced Primary Open-Angle Glaucoma and Leber Hereditary Optic Neuropathy

    PubMed Central

    Van Bergen, Nicole J; Crowston, Jonathan G.; Craig, Jamie E.; Burdon, Kathryn P.; Kearns, Lisa S.; Sharma, Shiwani; Hewitt, Alex W.; Mackey, David A.; Trounce, Ian A.

    2015-01-01

    Primary Open Angle Glaucoma (POAG) is a common neurodegenerative disease characterized by the selective and gradual loss of retinal ganglion cells (RGCs). Aging and increased intraocular pressure (IOP) are glaucoma risk factors; nevertheless patients deteriorate at all levels of IOP, implying other causative factors. Recent evidence presents mitochondrial oxidative phosphorylation (OXPHOS) complex-I impairments in POAG. Leber Hereditary Optic Neuropathy (LHON) patients suffer specific and rapid loss of RGCs, predominantly in young adult males, due to complex-I mutations in the mitochondrial genome. This study directly compares the degree of OXPHOS impairment in POAG and LHON patients, testing the hypothesis that the milder clinical disease in POAG is due to a milder complex-I impairment. To assess overall mitochondrial capacity, cells can be forced to produce ATP primarily from mitochondrial OXPHOS by switching the media carbon source to galactose. Under these conditions POAG lymphoblasts grew 1.47 times slower than controls, whilst LHON lymphoblasts demonstrated a greater degree of growth impairment (2.35 times slower). Complex-I enzyme specific activity was reduced by 18% in POAG lymphoblasts and by 29% in LHON lymphoblasts. We also assessed complex-I ATP synthesis, which was 19% decreased in POAG patients and 17% decreased in LHON patients. This study demonstrates both POAG and LHON lymphoblasts have impaired complex-I, and in the majority of aspects the functional defects in POAG were milder than LHON, which could reflect the milder disease development of POAG. This new evidence places POAG in the spectrum of mitochondrial optic neuropathies and raises the possibility for new therapeutic targets aimed at improving mitochondrial function. PMID:26496696

  13. CONTACT URTICARIA: PRESENT SCENARIO

    PubMed Central

    Bhatia, Ruchi; Alikhan, Ali; Maibach, Howard I

    2009-01-01

    Immunological contact urticaria is a hypersensitivity reaction that appears on the skin following contact with an eliciting substance. Recent advances in our understanding of the molecular mechanism and pathogenesis of this reaction have altered its classification, diagnosis, and treatment. We discuss classification, epidemiology, diagnosis, testing, and treatment options that are available to patients with contact urticaria. PMID:20161861

  14. 76 FR 62678 - Table Saw Blade Contact Injuries; Advance Notice of Proposed Rulemaking; Request for Comments and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-11

    ... accidental contact with the blade. In the Federal Register of July 9, 2003 (68 FR 40912) and September 5, 2003 (68 FR 52753), we invited comments on the issues raised by the petition (Petition No. CP03-2). We... injury, followed by fractures (12.4%), amputation (12.0%), and avulsion (8.5%). The rate...

  15. Characterization of laser-fired contacts in PERC solar cells: SIMS and TEM analysis applying advanced preparation techniques

    NASA Astrophysics Data System (ADS)

    Zastrow, U.; Houben, L.; Meertens, D.; Grohe, A.; Brammer, T.; Schneiderlöchner, E.

    2006-07-01

    In this study we apply ion-beam supported preparation techniques for both mesa formation by trench sputtering and FIB 'lift-out' lamella cutting for dynamic SIMS and TEM analysis of laser-fired Al point contacts on Si, respectively. Detailed compositional and structural informations about the metallurgical contact formation process are obtained combining both characterization techniques. While TEM micrographs and microdiffraction patterns reveal a mixture of Al- and Si-crystals within the ˜1 μm thick Al rich re-solidified surface layer according to the Al-Si phase diagram, spatially resolved SIMS depth profiling indicates ppm-range Al-diffusion a few hundred nm into the buried, substantially undisturbed Si-lattice.

  16. Simulations and surface quality testing of high asymmetry angle x-ray crystal monochromators for advanced x-ray imaging applications

    NASA Astrophysics Data System (ADS)

    Zápražný, Z.; Korytár, D.; Šiffalovič, P.; Jergel, M.; Demydenko, M.; Mikulík, P.; Dobročka, E.; Ferrari, C.; Vagovič, P.; Mikloška, M.

    2014-09-01

    Advanced X-ray imaging techniques of weakly absorbing structures require an increase of the sensitivity to small refractive angles considering that they are based more on coherent X-ray phase contrast than on X-ray absorption one. Simulations of diffraction properties of germanium (Ge) X-ray crystal monochromators and of analyzer based imaging (ABI) method were performed for various asymmetry factors and several lattice plane orientations using an X-ray energy range from 8 keV to 20 keV. Using an appropriate phase/amplitude retrieval method one can recover the phase information from the ABI image, which is directly proportional to the projected electron density. We are using germanium based optics for X-ray imaging or image magnification. The use of Ge crystals offers several advantages over silicon crystals. The integrated reflectivity of Ge crystals is two to three times larger than that of Si crystals. The spatial resolution of Ge magnifiers is typically two times better than the spatial resolution of Si magnifiers. We used high asymmetry diffractions to increase effectively the propagation distance and decrease the effective pixel size of the detector, to achieve a sufficient magnification of the sample and to improve coherence and increase output intensity. The most important parameter of a highly asymmetric monochromators as image magnifiers is the crystal surface quality. We have applied several crystal surface finishing methods including conventional mechanical lapping, chemical polishing, chemo-mechanical polishing and advanced nano-machining using single point diamond turning (SPDT), and we have evaluated these methods by means of AFM, diffractometry, reciprocal space mapping and others.

  17. Implementation and performance of SIBYLS: a dual endstation small-angle X-ray scattering and macromolecular crystallography beamline at the Advanced Light Source.

    PubMed

    Classen, Scott; Hura, Greg L; Holton, James M; Rambo, Robert P; Rodic, Ivan; McGuire, Patrick J; Dyer, Kevin; Hammel, Michal; Meigs, George; Frankel, Kenneth A; Tainer, John A

    2013-02-01

    The SIBYLS beamline (12.3.1) of the Advanced Light Source at Lawrence Berkeley National Laboratory, supported by the US Department of Energy and the National Institutes of Health, is optimized for both small-angle X-ray scattering (SAXS) and macromolecular crystallography (MX), making it unique among the world's mostly SAXS or MX dedicated beamlines. Since SIBYLS was commissioned, assessments of the limitations and advantages of a combined SAXS and MX beamline have suggested new strategies for integration and optimal data collection methods and have led to additional hardware and software enhancements. Features described include a dual mode monochromator [containing both Si(111) crystals and Mo/B(4)C multilayer elements], rapid beamline optics conversion between SAXS and MX modes, active beam stabilization, sample-loading robotics, and mail-in and remote data collection. These features allow users to gain valuable insights from both dynamic solution scattering and high-resolution atomic diffraction experiments performed at a single synchrotron beamline. Key practical issues considered for data collection and analysis include radiation damage, structural ensembles, alternative conformers and flexibility. SIBYLS develops and applies efficient combined MX and SAXS methods that deliver high-impact results by providing robust cost-effective routes to connect structures to biology and by performing experiments that aid beamline designs for next generation light sources. PMID:23396808

  18. Implementation and performance of SIBYLS: a dual endstation small-angle X-ray scattering and macromolecular crystallography beamline at the Advanced Light Source

    PubMed Central

    Classen, Scott; Hura, Greg L.; Holton, James M.; Rambo, Robert P.; Rodic, Ivan; McGuire, Patrick J.; Dyer, Kevin; Hammel, Michal; Meigs, George; Frankel, Kenneth A.; Tainer, John A.

    2013-01-01

    The SIBYLS beamline (12.3.1) of the Advanced Light Source at Lawrence Berkeley National Laboratory, supported by the US Department of Energy and the National Institutes of Health, is optimized for both small-angle X-ray scattering (SAXS) and macromolecular crystallography (MX), making it unique among the world’s mostly SAXS or MX dedicated beamlines. Since SIBYLS was commissioned, assessments of the limitations and advantages of a combined SAXS and MX beamline have suggested new strategies for integration and optimal data collection methods and have led to additional hardware and software enhancements. Features described include a dual mode monochromator [containing both Si(111) crystals and Mo/B4C multilayer elements], rapid beamline optics conversion between SAXS and MX modes, active beam stabilization, sample-loading robotics, and mail-in and remote data collection. These features allow users to gain valuable insights from both dynamic solution scattering and high-resolution atomic diffraction experiments performed at a single synchrotron beamline. Key practical issues considered for data collection and analysis include radiation damage, structural ensembles, alternative conformers and flexibility. SIBYLS develops and applies efficient combined MX and SAXS methods that deliver high-impact results by providing robust cost-effective routes to connect structures to biology and by performing experiments that aid beamline designs for next generation light sources. PMID:23396808

  19. Optical design of the short pulse x-ray imaging and microscopy time-angle correlated diffraction beamline at the Advanced Photon Source

    SciTech Connect

    Reininger, R.; Dufresne, E. M.; Borland, M.; Beno, M. A.; Young, L.; Kim, K.-J.; Evans, P. G.

    2013-05-15

    The short pulse x-ray imaging and microscopy beamline is one of the two x-ray beamlines that will take full advantage of the short pulse x-ray source in the Advanced Photon Source (APS) upgrade. A horizontally diffracting double crystal monochromator which includes a sagittally focusing second crystal will collect most of the photons generated when the chirped electron beam traverses the undulator. A Kirkpatrick-Baez mirror system after the monochromator will deliver to the sample a beam which has an approximately linear correlation between time and vertical beam angle. The correlation at the sample position has a slope of 0.052 ps/{mu}rad extending over an angular range of 800 {mu}rad for a cavity deflection voltage of 2 MV. The expected time resolution of the whole system is 2.6 ps. The total flux expected at the sample position at 10 keV with a 0.9 eV energy resolution is 5.7 Multiplication-Sign 10{sup 12} photons/s at a spot having horizontal and vertical full width at half maximum of 33 {mu}m horizontal by 14 {mu}m vertical. This new beamline will enable novel time-dispersed diffraction experiments on small samples using the full repetition rate of the APS.

  20. Simulation model of the F/A-18 high angle-of-attack research vehicle utilized for the design of advanced control laws

    NASA Technical Reports Server (NTRS)

    Strickland, Mark E.; Bundick, W. Thomas; Messina, Michael D.; Hoffler, Keith D.; Carzoo, Susan W.; Yeager, Jessie C.; Beissner, Fred L., Jr.

    1996-01-01

    The 'f18harv' six degree-of-freedom nonlinear batch simulation used to support research in advanced control laws and flight dynamics issues as part of NASA's High Alpha Technology Program is described in this report. This simulation models an F/A-18 airplane modified to incorporate a multi-axis thrust-vectoring system for augmented pitch and yaw control power and actuated forebody strakes for enhanced aerodynamic yaw control power. The modified configuration is known as the High Alpha Research Vehicle (HARV). The 'f18harv' simulation was an outgrowth of the 'f18bas' simulation which modeled the basic F/A-18 with a preliminary version of a thrust-vectoring system designed for the HARV. The preliminary version consisted of two thrust-vectoring vanes per engine nozzle compared with the three vanes per engine actually employed on the F/A-18 HARV. The modeled flight envelope is extensive in that the aerodynamic database covers an angle-of-attack range of -10 degrees to +90 degrees, sideslip range of -20 degrees to +20 degrees, a Mach Number range between 0.0 and 2.0, and an altitude range between 0 and 60,000 feet.

  1. Analysis of release kinetics of ocular therapeutics from drug releasing contact lenses: Best methods and practices to advance the field.

    PubMed

    Tieppo, Arianna; Boggs, Aarika C; Pourjavad, Payam; Byrne, Mark E

    2014-08-01

    Several methods have been proposed to achieve an extended and controlled release of ocular therapeutics via contact lenses; however, the experimental conditions used to study the drug release vary greatly and significantly influence the release kinetics. In this paper, we examine variations in the release conditions and their effect on the release of both hydrophilic and hydrophobic drugs (ketotifen fumarate, diclofenac sodium, timolol maleate and dexamethasone) from conventional hydrogel and silicone hydrogel lenses. Drug release was studied under different conditions, varying volume, mixing rates, and temperature. Volume had the biggest effect on the release profile, which ironically is the least consistent variable throughout the literature. When a small volume (2-30 mL) was used with no forced mixing and solvent exchange every 24 h, equilibrium was reached promptly much earlier than solvent exchange, significantly damping the drug release rate and artificially extending the release duration, leading to false conclusions. Using a large volume (200-400 mL) with a 30 rpm mixing rate and no solvent exchange, the release rate and total mass released was significantly increased. In general, the release performed in small volumes with no force mixing exhibited cumulative mass release amounts of 3-12 times less than the cumulative release amounts in large volumes with mixing. Increases in mixing rate and temperature resulted in relatively small increases of 1.4 and 1.2 times, respectively in fractional mass released. These results strongly demonstrate the necessity of proper and thorough analysis of release data to assure that equilibrium is not affecting release kinetics. This is paramount for comparison of various controlled drug release methods of therapeutic contact lenses, validation of the potential of lenses as an efficient and effective means of drug delivery, as well as increasing the likelihood of only the most promising methods reaching in vivo studies. PMID

  2. Contact Dermatitis

    MedlinePlus

    ... care Kids’ zone Video library Find a dermatologist Contact dermatitis Overview Contact dermatitis: Many health care workers ... to touching her face while wearing latex gloves. Contact dermatitis: Overview Almost everyone gets this type of ...

  3. Language Contact.

    ERIC Educational Resources Information Center

    Nelde, Peter Hans

    1995-01-01

    Examines the phenomenon of language contact and recent trends in linguistic contact research, which focuses on language use, language users, and language spheres. Also discusses the role of linguistic and cultural conflicts in language contact situations. (13 references) (MDM)

  4. 'Magic Angle Precession'

    SciTech Connect

    Binder, Bernd

    2008-01-21

    An advanced and exact geometric description of nonlinear precession dynamics modeling very accurately natural and artificial couplings showing Lorentz symmetry is derived. In the linear description it is usually ignored that the geometric phase of relativistic motion couples back to the orbital motion providing for a non-linear recursive precession dynamics. The high coupling strength in the nonlinear case is found to be a gravitomagnetic charge proportional to the precession angle and angular velocity generated by geometric phases, which are induced by high-speed relativistic rotations and are relevant to propulsion technologies but also to basic interactions. In the quantum range some magic precession angles indicating strong coupling in a phase-locked chaotic system are identified, emerging from a discrete time dynamical system known as the cosine map showing bifurcations at special precession angles relevant to heavy nuclei stability. The 'Magic Angle Precession' (MAP) dynamics can be simulated and visualized by cones rolling in or on each other, where the apex and precession angles are indexed by spin, charge or precession quantum numbers, and corresponding magic angles. The most extreme relativistic warping and twisting effect is given by the Dirac spinor half spin constellation with 'Hyperdiamond' MAP, which resembles quark confinement.

  5. Interferometric control of contact line, shape, and aberrations of liquid lenses

    NASA Astrophysics Data System (ADS)

    Voitenko, Igor; Storm, Ronald; Westfall, Raymond; Rogers, Stanley

    2007-09-01

    An optical system consisting of an aqueous electrolyte resting on a polymer/gold/indium-tin-oxide (ITO) layer deposited onto a glass substrate is analyzed to acquire contact angle - focal distance data as a function of applied voltage. The shape factor of a liquid lens and its dependence on the perimeter of contact line and contact angle was analyzed in the presence of an electrical field applied between the electrolyte and planar electrode system. The contact angle of a liquid on a thin, transparent film of gold (20 nm thick) - on ITO under electrolyte solution could be varied from 110 +/- 3° when the gold was held at -2.4 V to 41 +/- 3° without voltage. The behavior of a water-based electrolyte and water-soluble polymer blend and its influence on the shape of contact line and profile of the lens were investigated by employing a holographic setup at wavelengths of 632.8 and 543.5 nm. Optical micrographs showing the profile of the lens, aberration-less aperture, deformation of contact line, and shape of the liquid lens, respectively, were analyzed in reflection and transmission. Both the advancing and receding contact angles were measured directly from digitized images of the profile of the lens. The dynamic range of linear beam steering and dependence of the focal length of the liquid lens on the applied voltage are discussed.

  6. Angle detector

    NASA Technical Reports Server (NTRS)

    Parra, G. T. (Inventor)

    1978-01-01

    An angle detector for determining a transducer's angular disposition to a capacitive pickup element is described. The transducer comprises a pendulum mounted inductive element moving past the capacitive pickup element. The capacitive pickup element divides the inductive element into two parts L sub 1 and L sub 2 which form the arms of one side of an a-c bridge. Two networks R sub 1 and R sub 2 having a plurality of binary weighted resistors and an equal number of digitally controlled switches for removing resistors from the networks form the arms of the other side of the a-c bridge. A binary counter, controlled by a phase detector, balances the bridge by adjusting the resistance of R sub 1 and R sub 2. The binary output of the counter is representative of the angle.

  7. The impact of contact

    NASA Astrophysics Data System (ADS)

    Finney, B.

    1986-10-01

    Scenarios of the impact on human society of radio contact with an extraterrestrial civilization are presented. Some believe that contact with advanced extraterrestrials would quickly devastate the human spirit, while others believe that these super-intelligent beings would show the inhabitants of the earth how to live in peace. It is proposed that the possible existence of extraterrestrial civilizations and the development of means of studying and communicating with them need to be considered.

  8. Advanced Observation Operators for GPS Radio Occultation. Part 1; Validation of the 2D Ray Tracing Approach with CHAMP and SAC-C bending angle and refractivity data

    NASA Technical Reports Server (NTRS)

    Poli, P.; Joiner, J.

    2003-01-01

    Global Positioning System (GPS) Radio Occultations (RO) bending angles and refractivity data characterize mostly the vertical structure of the Earth's atmosphere. We answer the question whether proper simulation of GPS RO data for data assimilation can be obtained with one-dimensional vertical operators, or if accounting also for horizontal atmospheric structures via ray-tracing makes a positive difference when compared with real data. We present a detailed implementation of a geometrical optics multi-plane two-dimensional (2D) ray-tracing as an observation operator to simulate GPS RO bending angles and refractivities within the Finite Volume Data Assimilation System (FVDAS). Comparisons of the outputs of that 2D observation operator with those of simpler ID observation operators are used to generate estimates of errors induced by neglecting tangent point drift (TPD) and horizontal gradients (HG). These error estimates are then confronted with errors estimates derived using 6335 real CHAMP and SAC-C occultations. The agreement for TPD-induced (HG-induced) errors is remarkably positive at altitudes 10-30 km (below 10 km). Comparisons in bending angles O - B STD of the outputs of the multi-plane 2D ray-tracer with those of a vertical Abel transform show reductions of about 8% of the usual O - B bending angle STD due to TPD in the stratosphere (3% due to HG, in the troposphere only). In terms of refractivity, the O - B STD reductions are about 1520% for TPD and 3-5% for HG in the same regions. These reductions are obtained using either 6-hour forecasts or analyses as backgrounds, and using Geometrical Optics (GO) or Canonical Transform (CT) data.

  9. Flow analysis for the nacelle of an advanced ducted propeller at high angle-of-attack and at cruise with boundary layer control

    NASA Technical Reports Server (NTRS)

    Hwang, D. P.; Boldman, D. R.; Hughes, C. E.

    1994-01-01

    An axisymmetric panel code and a three dimensional Navier-Stokes code (used as an inviscid Euler code) were verified for low speed, high angle of attack flow conditions. A three dimensional Navier-Stokes code (used as an inviscid code), and an axisymmetric Navier-Stokes code (used as both viscous and inviscid code) were also assessed for high Mach number cruise conditions. The boundary layer calculations were made by using the results from the panel code or Euler calculation. The panel method can predict the internal surface pressure distributions very well if no shock exists. However, only Euler and Navier-Stokes calculations can provide a good prediction of the surface static pressure distribution including the pressure rise across the shock. Because of the high CPU time required for a three dimensional Navier-Stokes calculation, only the axisymmetric Navier-Stokes calculation was considered at cruise conditions. The use of suction and tangential blowing boundary layer control to eliminate the flow separation on the internal surface was demonstrated for low free stream Mach number and high angle of attack cases. The calculation also shows that transition from laminar flow to turbulent flow on the external cowl surface can be delayed by using suction boundary layer control at cruise flow conditions. The results were compared with experimental data where possible.

  10. From plane to spatial angles: PTB's spatial angle autocollimator calibrator

    NASA Astrophysics Data System (ADS)

    Kranz, Oliver; Geckeler, Ralf D.; Just, Andreas; Krause, Michael; Osten, Wolfgang

    2015-10-01

    Electronic autocollimators are utilised versatilely for non-contact angle measurements in applications like straightness measurements and profilometry. Yet, no calibration of the angle measurement of an autocollimator has been available when both its measurement axes are engaged. Additionally, autocollimators have been calibrated at fixed distances to the reflector, although its distance may vary during the use of an autocollimator. To extend the calibration capabilities of the Physikalisch-Technische Bundesanstalt (PTB) regarding spatial angles and variable distances, a novel calibration device has been set up: the spatial angle autocollimator calibrator (SAAC). In this paper, its concept and its mechanical realisation will be presented. The focus will be on the system's mathematical modelling and its application in spatial angle calibrations. The model considers the misalignments of the SAAC's components, including the non-orthogonalities of the measurement axes of the autocollimators and of the rotational axes of the tilting unit. It allows us to derive specific measurement procedures to determine the misalignments in situ and, in turn, to correct the measurements of the autocollimators. Finally, the realisation and the results of a traceable spatial angle calibration of an autocollimator will be presented. This is the first calibration of this type worldwide.

  11. Extracting magnetic cluster size and its distributions in advanced perpendicular recording media with shrinking grain size using small angle x-ray scattering

    SciTech Connect

    Mehta, Virat; Ikeda, Yoshihiro; Takano, Ken; Terris, Bruce D.; Hellwig, Olav; Wang, Tianhan; Wu, Benny; Graves, Catherine; Dürr, Hermann A.; Scherz, Andreas; Stöhr, Jo

    2015-05-18

    We analyze the magnetic cluster size (MCS) and magnetic cluster size distribution (MCSD) in a variety of perpendicular magnetic recording (PMR) media designs using resonant small angle x-ray scattering at the Co L{sub 3} absorption edge. The different PMR media flavors considered here vary in grain size between 7.5 and 9.5 nm as well as in lateral inter-granular exchange strength, which is controlled via the segregant amount. While for high inter-granular exchange, the MCS increases rapidly for grain sizes below 8.5 nm, we show that for increased amount of segregant with less exchange the MCS remains relatively small, even for grain sizes of 7.5 and 8 nm. However, the MCSD still increases sharply when shrinking grains from 8 to 7.5 nm. We show evidence that recording performance such as signal-to-noise-ratio on the spin stand correlates well with the product of magnetic cluster size and magnetic cluster size distribution.

  12. Direct determination of three-phase contact line properties on nearly molecular scale

    PubMed Central

    Winkler, P. M.; McGraw, R. L.; Bauer, P. S.; Rentenberger, C.; Wagner, P. E.

    2016-01-01

    Wetting phenomena in multi-phase systems govern the shape of the contact line which separates the different phases. For liquids in contact with solid surfaces wetting is typically described in terms of contact angle. While in macroscopic systems the contact angle can be determined experimentally, on the molecular scale contact angles are hardly accessible. Here we report the first direct experimental determination of contact angles as well as contact line curvature on a scale of the order of 1nm. For water nucleating heterogeneously on Ag nanoparticles we find contact angles around 15 degrees compared to 90 degrees for the corresponding macroscopically measured equilibrium angle. The obtained microscopic contact angles can be attributed to negative line tension in the order of −10−10 J/m that becomes increasingly dominant with increasing curvature of the contact line. These results enable a consistent theoretical description of heterogeneous nucleation and provide firm insight to the wetting of nanosized objects. PMID:27183880

  13. Direct determination of three-phase contact line properties on nearly molecular scale

    NASA Astrophysics Data System (ADS)

    Winkler, P. M.; McGraw, R. L.; Bauer, P. S.; Rentenberger, C.; Wagner, P. E.

    2016-05-01

    Wetting phenomena in multi-phase systems govern the shape of the contact line which separates the different phases. For liquids in contact with solid surfaces wetting is typically described in terms of contact angle. While in macroscopic systems the contact angle can be determined experimentally, on the molecular scale contact angles are hardly accessible. Here we report the first direct experimental determination of contact angles as well as contact line curvature on a scale of the order of 1nm. For water nucleating heterogeneously on Ag nanoparticles we find contact angles around 15 degrees compared to 90 degrees for the corresponding macroscopically measured equilibrium angle. The obtained microscopic contact angles can be attributed to negative line tension in the order of -10-10 J/m that becomes increasingly dominant with increasing curvature of the contact line. These results enable a consistent theoretical description of heterogeneous nucleation and provide firm insight to the wetting of nanosized objects.

  14. Calculations and surface quality measurements of high-asymmetry angle x-ray crystal monochromators for advanced x-ray imaging and metrological applications

    NASA Astrophysics Data System (ADS)

    Zápražný, Zdenko; Korytár, Dušan; Jergel, Matej; Šiffalovič, Peter; Dobročka, Edmund; Vagovič, Patrik; Ferrari, Claudio; Mikulík, Petr; Demydenko, Maksym; Mikloška, Marek

    2015-03-01

    We present the numerical optimization and the technological development progress of x-ray optics based on asymmetric germanium crystals. We show the results of several basic calculations of diffraction properties of germanium x-ray crystal monochromators and of an analyzer-based imaging method for various asymmetry factors using an x-ray energy range from 8 to 20 keV. The important parameter of highly asymmetric monochromators as image magnifiers or compressors is the crystal surface quality. We have applied several crystal surface finishing methods, including advanced nanomachining using single-point diamond turning (SPDT), conventional mechanical lapping, chemical polishing, and chemomechanical polishing, and we have evaluated these methods by means of atomic force microscopy, diffractometry, reciprocal space mapping, and others. Our goal is to exclude the chemical etching methods as the final processing technique because it causes surface undulations. The aim is to implement very precise deterministic methods with a control of surface roughness down to 0.1 nm. The smallest roughness (˜0.3 nm), best planarity, and absence of the subsurface damage were observed for the sample which was machined using an SPDT with a feed rate of 1 mm/min and was consequently polished using a fine polishing 15-min process with a solution containing SiO2 nanoparticles (20 nm).

  15. Singularity-free description of moving contact lines for volatile liquids

    NASA Astrophysics Data System (ADS)

    Rednikov, Alexey; Colinet, Pierre

    2013-01-01

    For a liquid advancing or receding on a flat bare solid in a vapor atmosphere, we show that no singularities in fact arise at the contact (triple) line. Contrary to common expectations, this does not require any “regularizing” microscopic effect (such as slip at the substrate, disjoining pressure or precursor films). The key here is the Kelvin effect, i.e., a curvature-induced variation of saturation conditions. Importantly, no evaporation-related singularities appear either. We proceed within the lubrication approximation and a classical one-sided model for zero or finite contact angle.

  16. Spray coating of superhydrophobic and angle-independent coloured films.

    PubMed

    Ge, Dengteng; Yang, Lili; Wu, Gaoxiang; Yang, Shu

    2014-03-01

    Angle-independent coloured films with superhydrophobicity were fabricated from quasi-amorphous arrays of monodispersed fluorinated silica nanoparticles via one-step spray coating. The film exhibited a high contact angle (>150°) and a low roll-off angle (~2°) and the colour could be tuned to blue, green and moccasin by varying the size of the nanoparticles.

  17. Contact hysteroscopy.

    PubMed

    Baggish, M S; Barbot, J

    1983-06-01

    In 1907 innovations in optics and illumination made by Maximilian Nitze were applied to hysteroscopy by Charles David, who wrote a treatise of hysteroscopy. David improved illumination by placing an electric incandescent bulb at the intrauterine end of his endoscope and also sealed the distal end of the tube with a piece of glass. The history of the contact endoscope that the authors personally used is connected to the invention by Vulmiere (1952) of a revolutionary illumination process in endoscopy--the "cold light" process. The components of cold light consist of a powerful external light source that is transmitted via a special optical guide into the endometrial cavity. The 1st application of his principle (1963) was an optical trochar contained in a metallic sheath. This simple endoscope was perfected, and in 1973 Barbot and Parent, in France, began to use it to examine the uterine cavity. Discussion focuses on methods, instrumentation, method for examination (grasping the instrument, setup, light source, anesthesia, dilatation, technique, and normal endometrium); cervical neoplasia; nonneoplastic lesions of the endometrium (endometrial polyp, submucous myoma, endometrial hyperplasia); intrauterine device localization; neoplastic lesions of the endometrium; precursors (adenocarcinoma); hysteroscopy in pregnancy (embryoscopy, hydatidiform mole, postpartum hemorrhage, incomplete abortion, spontaneous abortion, induced abortions, and amnioscopy); and examinations of children and infants. The contact endoscope must make light contact with the structure to be viewed. The principles of contact endoscopy depend on an interpretation of color, contour, vascular pattern, and a sense of touch. These are computed together and a diagnosis is made on the basis of previously learned clinical pathologic correlations. The contact endoscope is composed of 3 parts: an optical guide; a cylindric chamber that collects and traps ambient light; and a magnifying eyepiece. The phase of

  18. Contact activation of blood-plasma coagulation

    NASA Astrophysics Data System (ADS)

    Golas, Avantika

    Surface engineering of biomaterials with improved hemocompatibility is an imperative, given the widespread global need for cardiovascular devices. Research summarized in this dissertation focuses on contact activation of FXII in buffer and blood plasma frequently referred to as autoactivation. The extant theory of contact activation imparts FXII autoactivation ability to negatively charged, hydrophilic surfaces. According to this theory, contact activation of plasma involves assembly of proteins comprising an "activation complex" on activating surfaces mediated by specific chemical interactions between complex proteins and the surface. This work has made key discoveries that significantly improve our core understanding of contact activation and unravel the existing paradigm of plasma coagulation. It is shown herein that contact activation of blood factor XII (FXII, Hageman factor) in neat-buffer solution exhibits a parabolic profile when scaled as a function of silanized-glass-particle activator surface energy (measured as advancing water adhesion tension t°a=g° Iv costheta in dyne/cm, where g°Iv is water interfacial tension in dyne/cm and theta is the advancing contact angle). Nearly equal activation is observed at the extremes of activator water-wetting properties --36 < t°a < 72 dyne/cm (O° ≤ theta < 120°), falling sharply through a broad minimum within the 20 < t°a < 40 dyne/cm (55° < theta < 75°). Furthermore, contact activation of FXII in buffer solution produces an ensemble of protein fragments exhibiting either procoagulant properties in plasma (proteolysis of blood factor XI or prekallikrein), amidolytic properties (cleavage of s-2302 chromogen), or the ability to suppress autoactivation through currently unknown biochemistry. The relative proportions of these fragments depend on activator surface chemistry/energy. We have also discovered that contact activation is moderated by adsorption of plasma proteins unrelated to coagulation through an

  19. Fabricating customized hydrogel contact lens

    PubMed Central

    Childs, Andre; Li, Hao; Lewittes, Daniella M.; Dong, Biqin; Liu, Wenzhong; Shu, Xiao; Sun, Cheng; Zhang, Hao F.

    2016-01-01

    Contact lenses are increasingly used in laboratories for in vivo animal retinal imaging and pre-clinical studies. The lens shapes often need modification to optimally fit corneas of individual test subjects. However, the choices from commercially available contact lenses are rather limited. Here, we report a flexible method to fabricate customized hydrogel contact lenses. We showed that the fabricated hydrogel is highly transparent, with refractive indices ranging from 1.42 to 1.45 in the spectra range from 400 nm to 800 nm. The Young’s modulus (1.47 MPa) and hydrophobicity (with a sessile drop contact angle of 40.5°) have also been characterized experimentally. Retinal imaging using optical coherence tomography in rats wearing our customized contact lenses has the quality comparable to the control case without the contact lens. Our method could significantly reduce the cost and the lead time for fabricating soft contact lenses with customized shapes, and benefit the laboratorial-used contact lenses in pre-clinical studies. PMID:27748361

  20. Fabricating customized hydrogel contact lens

    NASA Astrophysics Data System (ADS)

    Childs, Andre; Li, Hao; Lewittes, Daniella M.; Dong, Biqin; Liu, Wenzhong; Shu, Xiao; Sun, Cheng; Zhang, Hao F.

    2016-10-01

    Contact lenses are increasingly used in laboratories for in vivo animal retinal imaging and pre-clinical studies. The lens shapes often need modification to optimally fit corneas of individual test subjects. However, the choices from commercially available contact lenses are rather limited. Here, we report a flexible method to fabricate customized hydrogel contact lenses. We showed that the fabricated hydrogel is highly transparent, with refractive indices ranging from 1.42 to 1.45 in the spectra range from 400 nm to 800 nm. The Young’s modulus (1.47 MPa) and hydrophobicity (with a sessile drop contact angle of 40.5°) have also been characterized experimentally. Retinal imaging using optical coherence tomography in rats wearing our customized contact lenses has the quality comparable to the control case without the contact lens. Our method could significantly reduce the cost and the lead time for fabricating soft contact lenses with customized shapes, and benefit the laboratorial-used contact lenses in pre-clinical studies.

  1. Types of Contact Lenses

    MedlinePlus

    ... Consumer Devices Consumer Products Contact Lenses Types of Contact Lenses Share Tweet Linkedin Pin it More sharing ... Orthokeratology (Ortho-K) Decorative (Plano) Contact Lenses Soft Contact Lenses Soft contact lenses are made of soft, ...

  2. Prioritized Contact Transport Stream

    NASA Technical Reports Server (NTRS)

    Hunt, Walter Lee, Jr. (Inventor)

    2015-01-01

    A detection process, contact recognition process, classification process, and identification process are applied to raw sensor data to produce an identified contact record set containing one or more identified contact records. A prioritization process is applied to the identified contact record set to assign a contact priority to each contact record in the identified contact record set. Data are removed from the contact records in the identified contact record set based on the contact priorities assigned to those contact records. A first contact stream is produced from the resulting contact records. The first contact stream is streamed in a contact transport stream. The contact transport stream may include and stream additional contact streams. The contact transport stream may be varied dynamically over time based on parameters such as available bandwidth, contact priority, presence/absence of contacts, system state, and configuration parameters.

  3. Perception of Perspective Angles.

    PubMed

    Erkelens, Casper J

    2015-06-01

    We perceive perspective angles, that is, angles that have an orientation in depth, differently from what they are in physical space. Extreme examples are angles between rails of a railway line or between lane dividers of a long and straight road. In this study, subjects judged perspective angles between bars lying on the floor of the laboratory. Perspective angles were also estimated from pictures taken from the same point of view. Converging and diverging angles were judged to test three models of visual space. Four subjects evaluated the perspective angles by matching them to nonperspective angles, that is, angles between the legs of a compass oriented in the frontal plane. All subjects judged both converging and diverging angles larger than the physical angle and smaller than the angles in the proximal stimuli. A model of shallow visual space describes the results. According to the model, lines parallel to visual lines, vanishing at infinity in physical space, converge to visual lines in visual space. The perceived shape of perspective angles is incompatible with the perceived length and width of the bars. The results have significance for models of visual perception and practical implications for driving and flying in poor visibility conditions. PMID:27433312

  4. Contact lens management of keratoconus.

    PubMed

    Downie, Laura E; Lindsay, Richard G

    2015-07-01

    Contact lenses are the primary form of visual correction for patients with keratoconus. Contemporary advances in contact lens designs and materials have significantly expanded the available fitting options for patients with corneal ectasia. Furthermore, imaging technology, such as corneal topography and anterior segment optical coherence tomography, can be applied to both gain insight into corneal microstructural changes and to guide contact lens fitting. This paper provides a comprehensive review of the range of contact lens modalities, including soft lenses, hybrid designs, rigid lenses, piggyback configurations, corneo-scleral, mini-scleral and scleral lenses that are currently available for the optical management of keratoconus. The review also discusses the importance of monitoring for disease progression in patients with keratoconus, in particular children, who tend to undergo more rapid progressive changes, so as to facilitate appropriate modification to contact lens fitting and/or potential referral for corneal collagen cross-linking treatment, as appropriate. PMID:26104589

  5. Detachment of deposited colloids by advancing and receding air-water interfaces.

    PubMed

    Aramrak, Surachet; Flury, Markus; Harsh, James B

    2011-08-16

    Moving air-water interfaces can detach colloidal particles from stationary surfaces. The objective of this study was to quantify the effects of advancing and receding air-water interfaces on colloid detachment as a function of interface velocity. We deposited fluorescent, negatively charged, carboxylate-modified polystyrene colloids (diameter of 1 μm) into a cylindrical glass channel. The colloids were hydrophilic with an advancing air-water contact angle of 60° and a receding contact angle of 40°. After colloid deposition, two air bubbles were sequentially introduced into the glass channel and passed through the channel at different velocities (0.5, 7.7, 72, 982, and 10,800 cm/h). The passage of the bubbles represented a sequence of receding and advancing air-water interfaces. Colloids remaining in the glass channel after each interface passage were visualized with confocal microscopy and quantified by image analysis. The advancing air-water interface was significantly more effective in detaching colloids from the glass surface than the receding interface. Most of the colloids were detached during the first passage of the advancing air-water interface, while the subsequent interface passages did not remove significant amounts of colloids. Forces acting on the colloids calculated from theory corroborate our experimental results, and confirm that the detachment forces (surface tension forces) during the advancing air-water interface movement were stronger than during the receding movement. Theory indicates that, for hydrophilic colloids, the advancing interface movement generally exerts a stronger detachment force than the receding, except when the hysteresis of the colloid-air-water contact angle is small and that of the channel-air-water contact angle is large.

  6. EDITORIAL: Close contact Close contact

    NASA Astrophysics Data System (ADS)

    Demming, Anna

    2010-07-01

    The development of scanning probe techniques, such as scanning tunnelling microscopy [1], has often been touted as the catalyst for the surge in activity and progress in nanoscale science and technology. Images of nanoscale structural detail have served as an invaluable investigative resource and continue to fascinate with the fantastical reality of an intricate nether world existing all around us, but hidden from view of the naked eye by a disparity in scale. As is so often the case, the invention of the scanning tunnelling microscope heralded far more than just a useful new apparatus, it demonstrated the scope for exploiting the subtleties of electronic contact. The shrinking of electronic devices has been a driving force for research into molecular electronics, in which an understanding of the nature of electronic contact at junctions is crucial. In response, the number of experimental techniques in molecular electronics has increased rapidly in recent years. Scanning tunnelling microscopes have been used to study electron transfer through molecular films on a conducting substrate, and the need to monitor the contact force of scanning tunnelling electrodes led to the use of atomic force microscopy probes coated in a conducting layer as studied by Cui and colleagues in Arizona [2]. In this issue a collaboration of researchers at Delft University and Leiden University in the Netherlands report a new device architecture for the independent mechanical and electrostatic tuning of nanoscale charge transport, which will enable thorough studies of molecular transport in the future [3]. Scanning probes can also be used to pattern surfaces, such as through spatially-localized Suzuki and Heck reactions in chemical scanning probe lithography. Mechanistic aspects of spatially confined Suzuki and Heck chemistry are also reported in this issue by researchers in Oxford [4]. All these developments in molecular electronics fabrication and characterization provide alternative

  7. Modelling PTB's spatial angle autocollimator calibrator

    NASA Astrophysics Data System (ADS)

    Kranz, Oliver; Geckeler, Ralf D.; Just, Andreas; Krause, Michael

    2013-05-01

    The accurate and traceable form measurement of optical surfaces has been greatly advanced by a new generation of surface profilometers which are based on the reflection of light at the surface and the measurement of the reflection angle. For this application, high-resolution electronic autocollimators provide accurate and traceable angle metrology. In recent years, great progress has been made at the Physikalisch-Technische Bundesanstalt (PTB) in autocollimator calibration. For an advanced autocollimator characterisation, a novel calibration device has been built up at PTB: the Spatial Angle Autocollimator Calibrator (SAAC). The system makes use of an innovative Cartesian arrangement of three autocollimators (two reference autocollimators and the autocollimator to be calibrated), which allows a precise measurement of the angular orientation of a reflector cube. Each reference autocollimator is sensitive primarily to changes in one of the two relevant tilt angles, whereas the autocollimator to be calibrated is sensitive to both. The distance between the reflector cube and the autocollimator to be calibrated can be varied flexibly. In this contribution, we present the SAAC and aspects of the mathematical modelling of the system for deriving analytical expressions for the autocollimators' angle responses. These efforts will allow advancing the form measurement substantially with autocollimator-based profilometers and approaching fundamental measurement limits. Additionally, they will help manufacturers of autocollimators to improve their instruments and will provide improved angle measurement methods for precision engineering.

  8. Revisiting mask contact hole measurements

    NASA Astrophysics Data System (ADS)

    Higuchi, Masaru; Gallagher, Emily; Ceperley, Daniel; Brunner, Timothy; Bowley, Reg; McGuire, Anne

    2006-10-01

    Contact holes represent one of the biggest critical dimension (CD) mask metrology challenges for 45nm technology mask development. The challenge is a consequence of both wafer and mask sensitivities. Large mask error factors and the small process windows found when contact holes are imaged on wafers impose very tight mask specifications for CD uniformity. The resultant CD error budget leaves little room for mask metrology. Current advanced mask metrology deploys a CD-SEM to characterize the mask contact hole CD uniformity. Measuring a contact hole is complex since it is inherently two-dimensional and is not always well-characterized by one-dimensional x- and y-axis measurements. This paper will investigate contact metrics such as line edge roughness (LER), region of interest (ROI) size, area, and CD sampling methods. The relative merits of each will be explored. Ultimately, an understanding of the connection between what is physically measured on the mask and what impacts wafer imaging must be understood. Simulations will be presented to explore the printability of a contact hole's physical attributes. The results will be summarized into a discussion of optimal contact hole metrology for 45nm technology node masks.

  9. Reading Angles in Maps

    ERIC Educational Resources Information Center

    Izard, Véronique; O'Donnell, Evan; Spelke, Elizabeth S.

    2014-01-01

    Preschool children can navigate by simple geometric maps of the environment, but the nature of the geometric relations they use in map reading remains unclear. Here, children were tested specifically on their sensitivity to angle. Forty-eight children (age 47:15-53:30 months) were presented with fragments of geometric maps, in which angle sections…

  10. Diffuse interface simulation of ternary fluids in contact with solid

    NASA Astrophysics Data System (ADS)

    Zhang, Chun-Yu; Ding, Hang; Gao, Peng; Wu, Yan-Ling

    2016-03-01

    In this article we developed a geometrical wetting condition for diffuse-interface simulation of ternary fluid flows with moving contact lines. The wettability of the substrate in the presence of ternary fluid flows is represented by multiple contact angles, corresponding to the different material properties between the respective fluid and the substrate. Displacement of ternary fluid flows on the substrate leads to the occurrence of moving contact point, at which three moving contact lines meet. We proposed a weighted contact angle model, to replace the jump in contact angle at the contact point by a relatively smooth transition of contact angle over a region of 'diffuse contact point' of finite size. Based on this model, we extended the geometrical formulation of wetting condition for two-phase flows with moving contact lines to ternary flows with moving contact lines. Combining this wetting condition, a Navier-Stokes solver and a ternary-fluid model, we simulated two-dimensional spreading of a compound droplet on a substrate, and validated the numerical results of the drop shape at equilibrium by comparing against the analytical solution. We also checked the convergence rate of the simulation by investigating the axisymmetric drop spreading in a capillary tube. Finally, we applied the model to a variety of applications of practical importance, including impact of a circular cylinder into a pool of two layers of different fluids and sliding of a three-dimensional compound droplet in shear flows.

  11. Salt deposition at particle contact points

    NASA Astrophysics Data System (ADS)

    Nie, Xiaodong; Evitts, Richard W.; Besant, Robert W.; Kennell, Glyn F.

    2015-09-01

    Caking may occur when granular potash fertilizer with a moisture content greater than 0.25 % (w/w) undergoes drying. Since cake strength is proportional to the mass of crystal deposited per unit volume near contact points (and other factors) the modelling of mass deposition near contact points is important. The Young-Laplace equation for the air-salt-solution interface is used to determine the geometry of a 2-D planar saline film between two cubic potash particles. A 2-D theoretical model is developed and applied for ion diffusion and deposition near the contact point during drying. The numerical predictions of ion diffusion in an initially saturated salt illustrate the transient spatial distribution of new KCl deposits along the solid surfaces near the contact line. These results indicate the average salt deposition commences at the air-liquid-solid intersection, where the liquid film is thinnest, and moves toward the particle contact point with increasing area averaged KCl deposits, causing the formation of crystal deposits and bridges near contact points. It is concluded that the average salt deposit height increases inversely with distance from the contact point and decreases with initial contact angle of the contact region, but the deposition is nearly independent of the evaporation or drying rate near each contact region. Caking strength depends on, among other parameters, the amount of salt deposition near contact points.

  12. An experimental analysis of elliptical adhesive contact

    NASA Astrophysics Data System (ADS)

    Sümer, Bilsay; Onal, Cagdas D.; Aksak, Burak; Sitti, Metin

    2010-06-01

    The elliptical adhesive contact is studied experimentally utilizing two hemicylinders of elastomeric poly(dimethylsiloxane) (PDMS). Experimental results are compared with the recent approximate Johnson-Kendall-Roberts (JKR) theory for elliptical contacts, and the deviation of the experiments from this theory is discussed in detail. To do this, the cylinders are placed with different skew angles with respect to each other in order to emulate the effect of orientation. The maximum adhesion force and the size of the contact zone are determined experimentally under the action of surface energy. The difference of the maximum adhesion force between experiments and theory is found to increase as the contact area goes from mildly elliptical to slim elliptical contact. Similarly, it is observed that the contact area can be approximated to have elliptical geometry for a wide range of skew angles while a deviation is observed for slim elliptical contacts. Moreover, the reduction in the contact area is observed to be nonself-similar during detachment from an elliptical shape to a circular one.

  13. Angles, Time, and Proportion

    ERIC Educational Resources Information Center

    Pagni, David L.

    2005-01-01

    This article describes an investigation making connections between the time on an analog clock and the angle between the minute hand and the hour hand. It was posed by a middle school mathematics teacher. (Contains 8 tables and 6 figures.)

  14. Reading angles in maps.

    PubMed

    Izard, Véronique; O'Donnell, Evan; Spelke, Elizabeth S

    2014-01-01

    Preschool children can navigate by simple geometric maps of the environment, but the nature of the geometric relations they use in map reading remains unclear. Here, children were tested specifically on their sensitivity to angle. Forty-eight children (age 47:15-53:30 months) were presented with fragments of geometric maps, in which angle sections appeared without any relevant length or distance information. Children were able to read these map fragments and compare two-dimensional to three-dimensional angles. However, this ability appeared both variable and fragile among the youngest children of the sample. These findings suggest that 4-year-old children begin to form an abstract concept of angle that applies both to two-dimensional and three-dimensional displays and that serves to interpret novel spatial symbols. PMID:23647223

  15. Irritant Contact Dermatitis

    MedlinePlus

    ... and rashes clinical tools newsletter | contact Share | Irritant Contact Dermatitis Information for adults A A A This ... severe involvement in the patient's armpit. Overview Irritant contact dermatitis is an inflammatory rash caused by direct ...

  16. Contact Lens Risks

    MedlinePlus

    ... Health and Consumer Devices Consumer Products Contact Lenses Contact Lens Risks Share Tweet Linkedin Pin it More ... redness blurred vision swelling pain Serious Hazards of Contact Lenses Symptoms of eye irritation can indicate a ...

  17. Contact Lens Care

    MedlinePlus

    ... For Consumers Consumer Information by Audience For Women Contact Lens Care Share Tweet Linkedin Pin it More ... 1088, www.fda.gov/medwatch Learn More about Contact Lens Care Other Tips on Contact Lenses Decorative ...

  18. Contact Lens Solution Toxicity

    MedlinePlus

    ... rash and rashes clinical tools newsletter | contact Share | Contact Lens Solution Toxicity Information for adults A A A This image shows a reaction to contact lens solution. The prominent blood vessels and redness ...

  19. Numerical analysis of contact line dynamics passing over a single wettable defect on a wall

    NASA Astrophysics Data System (ADS)

    Yamamoto, Yasufumi; Higashida, Shohei; Tanaka, Hiroyuki; Wakimoto, Tatsuro; Ito, Takahiro; Katoh, Kenji

    2016-08-01

    In this study, the dynamics of a contact line passing a single defect, which was represented by a locally wettable part (whose static contact angle is less than the other part, namely, chemically heterogeneous and physically flat part), was analyzed using numerical simulations employing the front-tracking method and the generalized Navier boundary condition. We observed that the contact line was distorted with a logarithmic shape far from the defect; however, the distortion was dependent on the wall velocity. The apparent (averaged) dynamic contact angle of the wall with a defect was evaluated using a macroscopic energy balance. The apparent dynamic contact angles estimated from the energy balance agree well with the arithmetic averaged angles obtained from the present simulations. The macroscopic energy balance is useful to consider the effect of heterogeneity or roughness of the wall on the relation between the dynamic contact angle and contact line speed.

  20. Pose and motion from contact

    SciTech Connect

    Jia, Y.B.; Erdmann, M.

    1999-05-01

    In the absence of vision, grasping an object often relies on tactile feedback from the fingertips. As the finger pushes the object, the fingertip can feel the contact point move. If the object is known in advance, from this motion the finger may infer the location of the contact point on the object, and thereby, the object pose. This paper primarily investigates the problem of determining the pose (orientation and position) and motion (velocity and angular velocity) of a planar object with known geometry from such contact motion generated by pushing. A dynamic analysis of pushing yields a nonlinear system that relates through contact the object pose and motion to the finger motion. The contact motion on the fingertip thus encodes certain information about the object pose. Nonlinear observability theory is employed to show that such information is sufficient for the finger to observe not only the pose, but also the motion of the object. Therefore, a sensing strategy can be realized as an observer of the nonlinear dynamic system. Two observers are subsequently introduced. The first observer, based on the work of Gautheir, Hammouri, and Othman (1992), has its gain determined by the solution of a Lyapunov-like equation; it can be activated at any time instant during a push. The second observer, based on Newton`s method, solves for the initial (motionless) object pose from three intermediate contact points during a push. Under the Coulomb-friction model, the paper deals with support friction in the plane and/or contact friction between the finger and the object. Extensive simulations have been done to demonstrate the feasibility of the two observers. Preliminary experiments (with an Adept robot) have also been conducted. A contact sensor has been implemented using strain gauges.

  1. Studies on contact lens materials.

    PubMed

    Alyanak, H; Aksoy, S; Hasirci, N

    1991-02-01

    The development of plastics with the optical properties of glass led promptly to their use as contact lenses and intra-ocular lenses to rectify certain visual defects. Research to improve these polymeric materials is continuous but there is not much in the literature since most of the findings are patented. In this work, polymethyl methacrylate, the most commonly used lens material was chosen as the base material and its co and terpolymers were prepared using 2-hydroxyethyl methacrylate, N-vinyl-2-pyrrolidinone, hexamethyl disiloxane, and polypropylene glycol. The transparency, refractive index, contact angle, density, equilibrium water content, and percent hydration properties were examined. Theoretical values were calculated for linear expansion and oxygen permeation from the density and hydration values.

  2. Thoughts on some outstanding issues in the physics of equilibrium wetting and conceptual understanding of contact lines

    NASA Astrophysics Data System (ADS)

    Sefiane, K.

    2011-08-01

    Equilibrium wetting is a fundamental phenomenon, relevant to many scientific areas. Since the pioneering work on equilibrium wetting of Thomas Young (1805) [1], researchers strived to advance our understanding of this fundamental problem. Despite its apparent simplicity, equilibrium wetting phenomenon still holds many unanswered questions and represents a challenge to modern physicists and engineers. The relationship between quantities amenable to measurements, like macroscopic wetting contact angle, and other surface ener- gies and physical properties remains to be fully elucidated. Wetting is a physical problem which spans over two length scales, inner region ("microscopic") length scale and outer region ("macroscopic"). The three-phase contact line, where the macroscopic region meets the micro- scopic one, and underlying surface forces, represents a challenge to fully understand and model. In this paper, a brief review of the basics of wetting and existing concepts is first presented. Then two important questions are discussed in the light of the latest experimental findings: first the relevance of the continuum concept when describing interfaces near the three-phase contact line, and second the effect of adsorption on interfacial energies and its use to explain some interesting observations like the dependence of equilibrium contact angle on pressure and size of droplets. These recent observations raise some fundamental questions about how the three-phase contact line is conceptualised.

  3. The inner region of the moving contact line - diffusive and nanoscale models

    NASA Astrophysics Data System (ADS)

    Nold, Andreas; Sibley, David N.; Goddard, Ben D.; Kalliadasis, Serafim

    2015-11-01

    Much of the work within the Complex Multiphase Systems group at Imperial College London for the last number of years has been to understand the moving contact line problem. In, it was shown that contrary to the classical asymptotic theory at the moving contact line, the intermediate region is in fact an overlap region between the inner and the outer regions. Here, we investigate the inner region independently for the Navier-Stokes/ Cahn-Hilliard (NS/CH) model for binary fluids, as well as dynamic density functional theory (DDFT) for a simple fluid. We show that in the NS/CH model, the overlap region is recovered in the sharp-interface limit, and we link the slip length to the mobility of the system. In contrast, DDFT, which is based on statistical mechanics of fluids, allows to incorporate nanoscale details. Results are presented for advancing and receding contact lines for a wide range of contact angles. The numerical method employs spectral methods in an unbounded domain along the surface. Advantages are discussed, both for differential and integral DDFT equations. We acknowledge financial support from ERC Advanced Grant No. 247031 and Imperial College through a DTG International Studentship.

  4. Dynamics of the Molten Contact Line

    NASA Technical Reports Server (NTRS)

    Sonin, Ain A.; Duthaler, Gregg; Liu, Michael; Torresola, Javier; Qiu, Taiqing

    1999-01-01

    The purpose of this program is to develop a basic understanding of how a molten material front spreads over a solid that is below its melting point, arrests, and freezes. Our hope is that the work will contribute toward a scientific knowledge base for certain new applications involving molten droplet deposition, including the "printing" of arbitrary three-dimensional objects by precise deposition of individual molten microdrops that solidify after impact. Little information is available at this time on the capillarity-driven motion and arrest of molten contact line regions. Schiaffino and Sonin investigated the arrest of the contact line of a molten microcrystalline wax spreading over a subcooled solid "target" of the same material. They found that contact line arrest takes place at an apparent liquid contact angle that depends primarily on the Stefan number S=c(T(sub f) -T(sub t)/L based on the temperature difference between the fusion point and the target temperature, and proposed that contact line arrest occurs when the liquid's dynamic contact angle approaches the angle of attack of the solidification front just behind the contact line. They also showed, however, that the conventional continuum equations and boundary conditions have no meaningful solution for this angle. The solidification front angle is determined by the heat flux just behind the contact line, and the heat flux is singular at that point. By comparing experiments with numerical computations, Schiaffino and Sonin estimated that the conventional solidification model must break down within a distance of order 0.1 - 1 microns of the contact line. The physical mechanism for this breakdown is as yet undetermined, and no first-principles theory exists for the contact angle at arrest. Schiaffino and Sonin also presented a framework for understanding how to moderate Weber number molten droplet deposition in terms of similarity laws and experimentation. The study is based on experiments with three molten

  5. Contact Dermatitis in Pediatrics.

    PubMed

    Pelletier, Janice L; Perez, Caroline; Jacob, Sharon E

    2016-08-01

    Contact dermatitis is an umbrella term that describes the skin's reaction to contacted noxious or allergenic substances. The two main categories of contact dermatitis are irritant type and allergic type. This review discusses the signs, symptoms, causes, and complications of contact dermatitis. It addresses the testing, treatment, and prevention of contact dermatitis. Proper management of contact dermatitis includes avoidance measures for susceptible children. Implementation of a nickel directive (regulating the use of nickel in jewelry and other products that come into contact with the skin) could further reduce exposure to the most common allergens in the pediatric population. [Pediatr Ann. 2016;45(8):e287-e292.]. PMID:27517356

  6. Impact of pinning of the triple contact line on electrowetting performance.

    PubMed

    Gupta, Rohini; Sheth, Danica M; Boone, Teno K; Sevilla, Arianne B; Fréchette, Joëlle

    2011-12-20

    Pinning of the triple contact line adversely affects electrowetting on dielectric. Electrowetting response of substrates with contact angle hysteresis ranging from 1° to 30° has been characterized, and the results are interpreted within the framework of electromechanics corrected for pinning. The relationship between contact angle hysteresis, threshold potential for liquid actuation, and electrowetting hysteresis is quantified. Our results demonstrate that a modified electrowetting equation, based on balance of forces (including the pinning forces) acting on the triple contact line and on the drop, describes the electrowetting response of substrates with significant contact angle hysteresis. Finally, the surface properties of PDMS Sylgard 184 were found to be influenced by the electric field.

  7. Simple Method For Testing Of The 90° Angle Of A Reflecting Prism

    NASA Astrophysics Data System (ADS)

    Ghodgaonkar, A. M.; Tiwari, R. D.; Ramani, K.

    1982-12-01

    A simple method for testing the 90° angle of a reflecting prism by placing two prisms in contact with one another on a standard test plate and counting the number of fringes is outlined. An angle accuracy of less than a second for the angle of a 90° reflecting prism has been obtained.

  8. Casting and Angling.

    ERIC Educational Resources Information Center

    Smith, Julian W.

    As part of a series of books and pamphlets on outdoor education, this manual consists of easy-to-follow instructions for fishing activities dealing with casting and angling. The manual may be used as a part of the regular physical education program in schools and colleges or as a club activity for the accomplished weekend fisherman or the…

  9. An Iterative Angle Trisection

    ERIC Educational Resources Information Center

    Muench, Donald L.

    2007-01-01

    The problem of angle trisection continues to fascinate people even though it has long been known that it can't be done with straightedge and compass alone. However, for practical purposes, a good iterative procedure can get you as close as you want. In this note, we present such a procedure. Using only straightedge and compass, our procedure…

  10. Interferometric measurement of angles.

    PubMed

    Malacara, D; Harris, O

    1970-07-01

    A new interferometric device for measuring small angles or rotations with high accuracy is described. This instrument works by counting fringes formed by the rotation of a flat-parallel plate of glass illuminated with a collimated beam from a gas laser. Some possible applications are given.

  11. Visualizing the shape of soft solid and fluid contacts between two surfaces

    NASA Astrophysics Data System (ADS)

    Pham, Jonathan; Schellenberger, Frank; Kappl, Michael; Vollmer, Doris; Butt, Hans-Jürgen

    The soft contact between two surfaces is fundamentally interesting for soft materials and fluid mechanics and relevant for friction and wear. The deformation of soft solid interfaces has received much interest because it interestingly reveals similarities to fluid wetting. We present an experimental route towards visualizing the three-dimensional contact geometry of either liquid-solid (i.e., oil and glass) or solid-solid (i.e., elastomer and glass) interfaces using a home-built combination of confocal microscopy and atomic force microscopy. We monitor the shape of a fluid capillary bridge and the depth of indentation in 3D while simultaneously measuring the force. In agreement with theoretical predictions, the height of the capillary bridge depends on the interfacial tensions. By using a slowly evaporating solvent, we quantify the temporal evolution of the capillary bridge and visualized the influence of pinning points on its shape. The position dependence of the advancing and receding contact angle along the three-phase contact line, particle-liquid-air, is resolved. Extending our system, we explore the contact deformation of soft solids where elasticity, in addition to surface tension, becomes an important factor.

  12. A new wetting mechanism based upon triple contact line pinning.

    PubMed

    Liu, Jianlin; Mei, Yue; Xia, Re

    2011-01-01

    The classical Wenzel and Cassie models fail to give a physical explanation of such phenomenon as the macroscopic contact angle actually being equal to the Young's contact angle if there is a spot (surface defect) inside the droplet. Here, we derive the expression of the macroscopic contact angle for this special substrate in use of the principle of least potential energy, and our analytical results are in good agreement with the experimental data. Our findings also suggest that it is the triple contact line (TCL) rather than the contact area that dominates the contact angle. Therefore a new model based upon the TCL pinning is developed to explain the different wetting properties of the Wenzel and Cassie models for hydrophilic and hydrophobic cases. Moreover, the new model predicts the macroscopic contact angle in a broader range accurately, which is consistent with the existing experimental findings. This study revisits the fundamentals of wetting on rough substrates. The new model derived will help to design better superhydrophobic materials and provide the prediction required to engineer novel microfluidic devices. PMID:21117687

  13. Relationship between maximum shoulder external rotation angle during throwing and physical variables.

    PubMed

    Miyashita, Koji; Urabe, Yukio; Kobayashi, Hirokazu; Yokoe, Kiyoshi; Koshida, Sentaro; Kawamura, Morio; Ida, Kunio

    2008-01-01

    The amount of stress imposed on shoulder and elbow appears to be directly correlated with the degree of maximum shoulder external rotation (MER) during throwing motions. Therefore, identifying risk factors contributing to the increase of MER angle may help to decrease the throwing injuries occurrence in baseball players. The purpose of the present study was to demonstrate the correlation between MER and the kinematic variables at stride foot contact (SFC) during the early cocking phase, the passive range of motion (ROM), and the shoulder strength. The subjects were 40 high school baseball players. Each subject carried out five throwing tasks with his maximum effort. A three-dimensional analysis was performed to obtain the MER, and the shoulder angles of external rotation (ER), extension and abduction at SFC in the early cocking phase. The ROM and muscle strength of the shoulder ER and internal rotation (IR) were also measured. Significant moderate linear correlations were found between the MER and the ER (r = -0.32, p = 0.04) at SFC, extension angle ( r= 0.35, p = 0.03) at SFC, IR strength (r = -0.30, p = 0.04) and passive ROM of ER (r = 0.46, p = 0.01). The shoulder IR and extension angles at SFC may determine the degree of the MER angle. Furthermore, weak IR muscle strength and excessive ROM of ER might be risk factors for shoulder and elbow injuries. The finding will enable us to establish better prevention and rehabilitation strategies for throwing injuries in baseball players. Key pointsIt has been reported that the amount of stress imposed on shoulder and elbow joints is correlated with the degree of maximum shoulder external rotation angle (MER) during throwing. Therefore, controlling MER within a normal range plays a key role in the prevention for throwing-related injuries in baseball players.Physical and biomechanical factors related to the degree of MER must be addressed to advance the current prevention and rehabilitation strategies for the shoulder and

  14. A Different Angle on Perspective

    ERIC Educational Resources Information Center

    Frantz, Marc

    2012-01-01

    When a plane figure is photographed from different viewpoints, lengths and angles appear distorted. Hence it is often assumed that lengths, angles, protractors, and compasses have no place in projective geometry. Here we describe a sense in which certain angles are preserved by projective transformations. These angles can be constructed with…

  15. Angle Sense: A Valuable Connector.

    ERIC Educational Resources Information Center

    Rubenstein, Rheta N.; And Others

    1993-01-01

    Proposes angle sense as a fundamental connector between mathematical concepts for middle grade students. Introduces the use of pattern blocks and a goniometer, a tool to measure angles, to help students develop angle sense. Discusses connections between angle measurement and the concepts of rational numbers, circles, area, number theory,…

  16. Contact lens sensors in ocular diagnostics.

    PubMed

    Farandos, Nicholas M; Yetisen, Ali K; Monteiro, Michael J; Lowe, Christopher R; Yun, Seok Hyun

    2015-04-22

    Contact lenses as a minimally invasive platform for diagnostics and drug delivery have emerged in recent years. Contact lens sensors have been developed for analyzing the glucose composition of tears as a surrogate for blood glucose monitoring and for the diagnosis of glaucoma by measuring intraocular pressure. However, the eye offers a wider diagnostic potential as a sensing site and therefore contact lens sensors have the potential to improve the diagnosis and treatment of many diseases and conditions. With advances in polymer synthesis, electronics and micro/nanofabrication, contact lens sensors can be produced to quantify the concentrations of many biomolecules in ocular fluids. Non- or minimally invasive contact lens sensors can be used directly in a clinical or point-of-care setting to monitor a disease state continuously. This article reviews the state-of-the-art in contact lens sensor fabrication, their detection, wireless powering, and readout mechanisms, and integration with mobile devices and smartphones. High-volume manufacturing considerations of contact lenses are also covered and a case study of an intraocular pressure contact lens sensor is provided as an example of a successful product. This Review further analyzes the contact lens market and the FDA regulatory requirements for commercialization of contact lens sensors.

  17. Complete 360° circumferential SSOCT gonioscopy of the iridocorneal angle

    NASA Astrophysics Data System (ADS)

    McNabb, Ryan P.; Kuo, Anthony N.; Izatt, Joseph A.

    2014-02-01

    The ocular iridocorneal angle is generally an optically inaccessible area when viewed directly through the cornea due to the high angle of incidence required and the large index of refraction difference between air and cornea (nair = 1.000 and ncornea = 1.376) resulting in total internal reflection. Gonioscopy allows for viewing of the angle by removing the aircornea interface through the use of a special contact lens on the eye. Gonioscopy is used clinically to visualize the angle directly but only en face. Optical coherence tomography (OCT) has been used to image the angle and deeper structures via an external approach. Typically, this imaging technique is performed by utilizing a conventional anterior segment OCT scanning system. However, instead of imaging the apex of the cornea, either the scanner or the subject is tilted such that the corneoscleral limbus is orthogonal to the optical axis of the scanner requiring multiple volumes to obtain complete circumferential coverage of the ocular angle. We developed a novel gonioscopic OCT (GOCT) system that images the entire ocular angle within a single volume via an "internal" approach through the use of a custom radially symmetric gonioscopic contact lens. We present, to our knowledge, the first complete 360° circumferential volumes of the iridocorneal angle from a direct, internal approach.

  18. Angles in the Sky?

    NASA Astrophysics Data System (ADS)

    Behr, Bradford

    2005-09-01

    Tycho Brahe lived and worked in the late 1500s before the telescope was invented. He made highly accurate observations of the positions of planets, stars, and comets using large angle-measuring devices of his own design. You can use his techniques to observe the sky as well. For example, the degree, a common unit of measurement in astronomy, can be measured by holding your fist at arm's length up to the sky. Open your fist and observe the distance across the sky covered by the width of your pinky fingernail. That is, roughly, a degree! After some practice, and knowing that one degree equals four minutes, you can measure elapsed time by measuring the angle of the distance that the Moon appears to have moved and multiplying that number by four. You can also figure distances and sizes of things. These are not precise measurements, but rough estimates that can give you a "close-enough" answer.

  19. Laser angle sensor

    NASA Technical Reports Server (NTRS)

    Pond, C. R.; Texeira, P. D.

    1985-01-01

    A laser angle measurement system was designed and fabricated for NASA Langley Research Center. The instrument is a fringe counting interferometer that monitors the pitch attitude of a model in a wind tunnel. A laser source and detector are mounted above the model. Interference fringes are generated by a small passive element on the model. The fringe count is accumulated and displayed by a processor in the wind tunnel control room. This report includes optical and electrical schematics, system maintenance and operation procedures.

  20. Contact reactions to food.

    PubMed

    Killig, Claudia; Werfel, Thomas

    2008-05-01

    Cutaneous adverse reactions to foods, spices, and food additives can occur both in occupational and nonoccupational settings in those who grow, handle, prepare, or cook food. Because spices are also utilized in cosmetics and perfumes, other exposures are encountered that can result in adverse cutaneous reactions. This article describes the reaction patterns that can occur upon contact with foods, including irritant contact dermatitis and allergic contact dermatitis. The ingestion of culprit foods by sensitized individuals can provoke a generalized eczematous rash, referred to as systemic contact dermatitis. Other contact reactions to food include contact urticaria and protein contact dermatitis provoked by high-molecular-weight food proteins often encountered in patients with atopic dermatitis. Phototoxic and photoallergic contact dermatitis are also considered.

  1. Allergic Contact Dermatitis

    MedlinePlus

    ... causes of allergic contact dermatitis include nickel, chromates, rubber chemicals, and topical antibiotic ointments and creams. Frequent ... construction workers who are in contact with cement. Rubber chemicals are found in gloves, balloons, elastic in ...

  2. Colored Contact Lens Dangers

    MedlinePlus

    ... Halloween Hazard: The Hidden Dangers of Buying Decorative Contact Lenses Without a Prescription Sep. 26, 2013 It ... the truth." Real People, Real Problems with Colored Contact Lenses Julian: Teenager Blinded In One Eye By ...

  3. Dynamic wettability properties of a soft contact lens hydrogel.

    PubMed

    Ketelson, Howard A; Meadows, David L; Stone, Ralph P

    2005-01-15

    The wettability of poly[2-hydroxyethyl methacrylate-co-methacrylic acid] (pHEMA-MAA) soft contact lenses was investigated in the absence and presence of block copolymer surfactants and lysozyme using the sessile drop method. The advancing dynamic contact angles (Thetaw/a) values are reported for water as a function of sequential wetting and drying cycles. The Thetaw/a values for the pHEMA-MAA in the absence of surfactant and lysozyme increased from approximately 20 degrees to 100 degrees as the number of cycles increased from two to ten, and they were independent of the pHEMA-MAA bulk water content. The change from the highly hydrophilic to hydrophobic pHEMA-MAA surface could not be reversed using the sequential wetting and drying cycles even under repeated exposures to saline solution. The effect of block copolymer surfactants with different molecular weights (MW) and hydrophilic-lipophilic balance (HLB) values on the pHEMA-MAA wettability were also studied. Low Theta(w/a) values were observed for pHEMA-MAA hydrogels that were treated with T1304 (MW 10500, HLB 14) and T904 (MW 6700, HLB 15). The surface tension data indicated that these surfactants were incompletely desorbed from the pHEMA-MAA and that the rate of desorption was slow in the timescale of the cycling experiments. Comparatively, poor wettability was observed for pHEMA-MAA surfaces presoaked in T304 (MW 1650, HLB 16) and T1107 (MW 15000, HLB 24) as Thetaw/a values greater than 90 degrees were measured for these surfactants. The surface tension data indicated that the rate of desorption of T304 and T1107 from the pHEMA-MAA was rapid and that they had a low affinity to the pHEMA-MAA. High contact angles were observed for the pHEMA-MAA hydrogels treated with lysozyme and also for the T1107 presoaked pHEMA-MAA that was also treated with lysozyme. Zero wetting angles throughout the sequential cycling were observed for the T1304 pre-treated pHEMA-MAA that had been treated with lysozyme. These results

  4. Moving contact line on chemically patterned surfaces

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Ping; Qian, Tiezheng; Sheng, Ping

    We simulate the moving contact line in two-dimensional chemically patterned channels using a diffuse-interface model with the generalized Navier boundary condition. The motion of the fluidslip behaviour of the contact line. The extra dissipation induced by this oscillatory contact-line motion is significant and increases rapidly with the wettability contrast of the pattern. A critical value of the wettability contrast is identified above which the effect of diffusion becomes important, leading to the interesting behaviour of fluid-fluid interface breaking, with the transport of the non-wetting fluid being assisted and mediated by rapid diffusion through the wetting fluid. Near the critical value, the time-averaged extra dissipation scales as U, the displacement velocity. By decreasing the period of the pattern, we show the solid surface to be characterized by an effective contact angle whose value depends on the material characteristics and composition of the patterned surfaces.

  5. Contact solution algorithms

    NASA Technical Reports Server (NTRS)

    Tielking, John T.

    1989-01-01

    Two algorithms for obtaining static contact solutions are described in this presentation. Although they were derived for contact problems involving specific structures (a tire and a solid rubber cylinder), they are sufficiently general to be applied to other shell-of-revolution and solid-body contact problems. The shell-of-revolution contact algorithm is a method of obtaining a point load influence coefficient matrix for the portion of shell surface that is expected to carry a contact load. If the shell is sufficiently linear with respect to contact loading, a single influence coefficient matrix can be used to obtain a good approximation of the contact pressure distribution. Otherwise, the matrix will be updated to reflect nonlinear load-deflection behavior. The solid-body contact algorithm utilizes a Lagrange multiplier to include the contact constraint in a potential energy functional. The solution is found by applying the principle of minimum potential energy. The Lagrange multiplier is identified as the contact load resultant for a specific deflection. At present, only frictionless contact solutions have been obtained with these algorithms. A sliding tread element has been developed to calculate friction shear force in the contact region of the rolling shell-of-revolution tire model.

  6. Glasses and Contact Lenses

    MedlinePlus

    ... Here's Help White House Lunch Recipes Glasses and Contact Lenses KidsHealth > For Kids > Glasses and Contact Lenses Print A A A Text Size What's ... together the way they should. But eyeglasses or contact lenses, also called corrective lenses, can help most ...

  7. Contact lens in keratoconus

    PubMed Central

    Rathi, Varsha M; Mandathara, Preeji S; Dumpati, Srikanth

    2013-01-01

    Contact lenses are required for the visual improvement in patients with keratoconus. Various contact lens options, such as rigid gas permeable (RGP) lenses, soft and soft toric lenses, piggy back contact lenses (PBCL), hybrid lenses and scleral lenses are availble. This article discusses about selection of a lens depending on the type of keratoconus and the fitting philosophies of various contact lenses including the starting trial lens. A Medline search was carried out for articles in the English language with the keywords keratoconus and various contact lenses such as Rose k lens, RGP lens, hybrid lens, scleral lens and PBCL. PMID:23925325

  8. Effect of contact ratio on spur gear dynamic load

    NASA Technical Reports Server (NTRS)

    Liou, Chuen-Huei; Lin, Hsiang Hsi; Oswald, Fred B.; Townsend, Dennis P.

    1992-01-01

    A computer simulation is presented which shows how the gear contact ratio affects the dynamic load on a spur gear transmission. The contact ratio can be affected by the tooth addendum, the pressure angle, the tooth size (diametral pitch), and the center distance. The analysis presented was performed using the NASA gear dynamics code, DANST. In the analysis, the contact ratio was varied over the range 1.20 to 2.40 by changing the length of the tooth addendum. In order to simplify the analysis, other parameters related to contact ratio were held constant. The contact ratio was found to have a significant influence on gear dynamics. Over a wide range of operating speeds, a contact ratio close to 2.0 minimized dynamic load. For low contact ratio gears (contact ratio less than 2.0), increasing the contact ratio reduced the gear dynamic load. For high contact ratio gears (contact ratio = or greater than 2.0), the selection of contact ratio should take into consideration the intended operating speeds. In general, high contact ratio gears minimized dynamic load better than low contact ratio gears.

  9. Wide Angle Movie

    NASA Technical Reports Server (NTRS)

    1999-01-01

    This brief movie illustrates the passage of the Moon through the Saturn-bound Cassini spacecraft's wide-angle camera field of view as the spacecraft passed by the Moon on the way to its closest approach with Earth on August 17, 1999. From beginning to end of the sequence, 25 wide-angle images (with a spatial image scale of about 14 miles per pixel (about 23 kilometers)were taken over the course of 7 and 1/2 minutes through a series of narrow and broadband spectral filters and polarizers, ranging from the violet to the near-infrared regions of the spectrum, to calibrate the spectral response of the wide-angle camera. The exposure times range from 5 milliseconds to 1.5 seconds. Two of the exposures were smeared and have been discarded and replaced with nearby images to make a smooth movie sequence. All images were scaled so that the brightness of Crisium basin, the dark circular region in the upper right, is approximately the same in every image. The imaging data were processed and released by the Cassini Imaging Central Laboratory for Operations (CICLOPS)at the University of Arizona's Lunar and Planetary Laboratory, Tucson, AZ.

    Photo Credit: NASA/JPL/Cassini Imaging Team/University of Arizona

    Cassini, launched in 1997, is a joint mission of NASA, the European Space Agency and Italian Space Agency. The mission is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Space Science, Washington DC. JPL is a division of the California Institute of Technology, Pasadena, CA.

  10. Dynamics of contact line depinning during droplet evaporation based on thermodynamics.

    PubMed

    Yu, Dong In; Kwak, Ho Jae; Doh, Seung Woo; Ahn, Ho Seon; Park, Hyun Sun; Kiyofumi, Moriyama; Kim, Moo Hwan

    2015-02-17

    For several decades, evaporation phenomena have been intensively investigated for a broad range of applications. However, the dynamics of contact line depinning during droplet evaporation has only been inductively inferred on the basis of experimental data and remains unclear. This study focuses on the dynamics of contact line depinning during droplet evaporation based on thermodynamics. Considering the decrease in the Gibbs free energy of a system with different evaporation modes, a theoretical model was developed to estimate the receding contact angle during contact line depinning as a function of surface conditions. Comparison of experimentally measured and theoretically modeled receding contact angles indicated that the dynamics of contact line depinning during droplet evaporation was caused by the most favorable thermodynamic process encountered during constant contact radius (CCR mode) and constant contact angle (CCA mode) evaporation to rapidly reach an equilibrium state during droplet evaporation.

  11. Numerical simulations of the moving contact line problem using a diffuse-interface model

    NASA Astrophysics Data System (ADS)

    Afzaal, Muhammad; Sibley, David; Duncan, Andrew; Yatsyshin, Petr; Duran-Olivencia, Miguel A.; Nold, Andreas; Savva, Nikos; Schmuck, Markus; Kalliadasis, Serafim

    2015-11-01

    Moving contact lines are a ubiquitous phenomenon both in nature and in many modern technologies. One prevalent way of numerically tackling the problem is with diffuse-interface (phase-field) models, where the classical sharp-interface model of continuum mechanics is relaxed to one with a finite thickness fluid-fluid interface, capturing physics from mesoscopic lengthscales. The present work is devoted to the study of the contact line between two fluids confined by two parallel plates, i.e. a dynamically moving meniscus. Our approach is based on a coupled Navier-Stokes/Cahn-Hilliard model. This system of partial differential equations allows a tractable numerical solution to be computed, capturing diffusive and advective effects in a prototypical case study in a finite-element framework. Particular attention is paid to the static and dynamic contact angle of the meniscus advancing or receding between the plates. The results obtained from our approach are compared to the classical sharp-interface model to elicit the importance of considering diffusion and associated effects. We acknowledge financial support from European Research Council via Advanced Grant No. 247031.

  12. Resistivity of Rotated Graphite-Graphene Contacts.

    PubMed

    Chari, Tarun; Ribeiro-Palau, Rebeca; Dean, Cory R; Shepard, Kenneth

    2016-07-13

    Robust electrical contact of bulk conductors to two-dimensional (2D) material, such as graphene, is critical to the use of these 2D materials in practical electronic devices. Typical metallic contacts to graphene, whether edge or areal, yield a resistivity of no better than 100 Ω μm but are typically >10 kΩ μm. In this Letter, we employ single-crystal graphite for the bulk contact to graphene instead of conventional metals. The graphite contacts exhibit a transfer length up to four-times longer than in conventional metallic contacts. Furthermore, we are able to drive the contact resistivity to as little as 6.6 Ω μm(2) by tuning the relative orientation of the graphite and graphene crystals. We find that the contact resistivity exhibits a 60° periodicity corresponding to crystal symmetry with additional sharp decreases around 22° and 39°, which are among the commensurate angles of twisted bilayer graphene.

  13. Glancing angle RF sheaths

    NASA Astrophysics Data System (ADS)

    D'Ippolito, D. A.; Myra, J. R.

    2013-10-01

    RF sheaths occur in tokamaks when ICRF waves encounter conducting boundaries. The sheath plays an important role in determining the efficiency of ICRF heating, the impurity influxes from the edge plasma, and the plasma-facing component damage. An important parameter in sheath theory is the angle θ between the equilibrium B field and the wall. Recent work with 1D and 2D sheath models has shown that the rapid variation of θ around a typical limiter can lead to enhanced sheath potentials and localized power deposition (hot spots) when the B field is near glancing incidence. The physics model used to obtain these results does not include some glancing-angle effects, e.g. possible modification of the angular dependence of the Child-Langmuir law and the role of the magnetic pre-sheath. Here, we report on calculations which explore these effects, with the goal of improving the fidelity of the rf sheath BC used in analytical and numerical calculations. Work supported by US DOE grants DE-FC02-05ER54823 and DE-FG02-97ER54392.

  14. Variable angle correlation spectroscopy

    SciTech Connect

    Lee, Y K

    1994-05-01

    In this dissertation, a novel nuclear magnetic resonance (NMR) technique, variable angle correlation spectroscopy (VACSY) is described and demonstrated with {sup 13}C nuclei in rapidly rotating samples. These experiments focus on one of the basic problems in solid state NMR: how to extract the wealth of information contained in the anisotropic component of the NMR signal while still maintaining spectral resolution. Analysis of the anisotropic spectral patterns from poly-crystalline systems reveal information concerning molecular structure and dynamics, yet in all but the simplest of systems, the overlap of spectral patterns from chemically distinct sites renders the spectral analysis difficult if not impossible. One solution to this problem is to perform multi-dimensional experiments where the high-resolution, isotropic spectrum in one dimension is correlated with the anisotropic spectral patterns in the other dimensions. The VACSY technique incorporates the angle between the spinner axis and the static magnetic field as an experimental parameter that may be incremented during the course of the experiment to help correlate the isotropic and anisotropic components of the spectrum. The two-dimensional version of the VACSY experiments is used to extract the chemical shift anisotropy tensor values from multi-site organic molecules, study molecular dynamics in the intermediate time regime, and to examine the ordering properties of partially oriented samples. The VACSY technique is then extended to three-dimensional experiments to study slow molecular reorientations in a multi-site polymer system.

  15. Non-contact measurement of contact wire

    NASA Astrophysics Data System (ADS)

    Yi, Yaxing; Ye, Xuemei; Li, Zhongke; Yue, Kaiduan

    2008-12-01

    The overhead contact system is the power supply unit of the electric locomotive. This article is to introduce our newly developed method to measure the height and pull out value of the contact wire. A carema dolly which can move on railway is applied to bear the weight of the measure equipment; two linear CCD cameras are installed on the dolly symmetrically about the midline of two rails. While the dolly move along the railway, two CCD cameras grasp the image synchronously, and a computer real-time process the images, the height and pull out value can be calculate out from the images.

  16. Contact Whiskers for Millimeter Wave Diodes

    NASA Technical Reports Server (NTRS)

    Kerr, A. R.; Grange, J. A.; Lichtenberger, J. A.

    1978-01-01

    Several techniques are investigated for making short conical tips on wires (whiskers) used for contacting millimeter-wave Schottky diodes. One procedure, using a phosphoric and chromic acid etching solution (PCE), is found to give good results on 12 microns phosphor-bronze wires. Full cone angles of 60 degrees-80 degrees are consistently obtained, compared with the 15 degrees-20 degrees angles obtained with the widely used sodium hydroxide etch. Methods are also described for cleaning, increasing the tip diameter (i.e. blunting), gold plating, and testing the contact resistance of the whiskers. The effects of the whisker tip shape on the electrical resistance, inductance, and capacitance of the whiskers are studied, and examples given for typical sets of parameters.

  17. [Contact dermatitis in Dakar].

    PubMed

    Niang, S O

    2007-01-01

    Because of the widespread repartition of allergens, allergic contact dermatitis is the most common inflammatory skin disease. It's the best model of dilated hypersensibility mediated by T lymphocytes cells. Atopic dermatitis and irritative dermatitis are to be distinguished to contact dermatitis. The aetiological diagnosis is the most important step of management of patients with that disease because it's the best way to avoid recurrences. The identification of cause is based on aetiological interrogatory and epicutaneous tests with 23 allergens completed with personnel products and specialised tests. Contact dermatitis can be classified according to results of aetiological management. In occupational contact dermatitis, contact dermatitis due to drugs, to metals, cosmetics, clothes and accessory and proteins. Management of patients with contact dermatitis is based on individual eviction, protection, cosmetovigilance, declaration of occupational dermatosis and allergovigilance. PMID:19102084

  18. Cerebellopontine Angle Lipoma

    PubMed Central

    Schuhmann, Martin U.; Lüdemann, Wolf O.; Schreiber, Hartwig; Samii, Madjid

    1997-01-01

    Intracranial lipomas in an infratentorial and extra-axial location are extremely rare. The presented case of an extensive lipoma of the cerebellopontine angle (CPA) represents 0.05% of all CPA tumors operated on in our department from 1978 to 1996. The lipoma constitutes an important differential diagnosis because the clinical management differs significantly from other CPA lesions. The clinical presentation and management of the presented case are analyzed in comparison to all previously described cases of CPA lipomas. The etiology and the radiological features of CPA lipomas are reviewed and discussed. CPA lipomas are maldevelopmental lesions that may cause slowly progressive symptoms. Neuroradiology enables a reliable preoperative diagnosis. Attempts of complete lipoma resection usually result in severe neurological deficits. Therefore, we recommend a conservative approach in managing these patients. Limited surgery is indicated if the patient has an associated vascular compression syndrome or suffers from disabling vertigo. ImagesFigure 1Figure 2Figure 3Figure 4 PMID:17171031

  19. Heterodyne Interferometer Angle Metrology

    NASA Technical Reports Server (NTRS)

    Hahn, Inseob; Weilert, Mark A.; Wang, Xu; Goullioud, Renaud

    2010-01-01

    A compact, high-resolution angle measurement instrument has been developed that is based on a heterodyne interferometer. The common-path heterodyne interferometer metrology is used to measure displacements of a reflective target surface. In the interferometer setup, an optical mask is used to sample the measurement laser beam reflecting back from a target surface. Angular rotations, around two orthogonal axes in a plane perpendicular to the measurement- beam propagation direction, are determined simultaneously from the relative displacement measurement of the target surface. The device is used in a tracking telescope system where pitch and yaw measurements of a flat mirror were simultaneously performed with a sensitivity of 0.1 nrad, per second, and a measuring range of 0.15 mrad at a working distance of an order of a meter. The nonlinearity of the device is also measured less than one percent over the measurement range.

  20. Narrow Angle movie

    NASA Technical Reports Server (NTRS)

    1999-01-01

    This brief three-frame movie of the Moon was made from three Cassini narrow-angle images as the spacecraft passed by the Moon on the way to its closest approach with Earth on August 17, 1999. The purpose of this particular set of images was to calibrate the spectral response of the narrow-angle camera and to test its 'on-chip summing mode' data compression technique in flight. From left to right, they show the Moon in the green, blue and ultraviolet regions of the spectrum in 40, 60 and 80 millisecond exposures, respectively. All three images have been scaled so that the brightness of Crisium basin, the dark circular region in the upper right, is the same in each image. The spatial scale in the blue and ultraviolet images is 1.4 miles per pixel (2.3 kilometers). The original scale in the green image (which was captured in the usual manner and then reduced in size by 2x2 pixel summing within the camera system) was 2.8 miles per pixel (4.6 kilometers). It has been enlarged for display to the same scale as the other two. The imaging data were processed and released by the Cassini Imaging Central Laboratory for Operations (CICLOPS) at the University of Arizona's Lunar and Planetary Laboratory, Tucson, AZ.

    Photo Credit: NASA/JPL/Cassini Imaging Team/University of Arizona

    Cassini, launched in 1997, is a joint mission of NASA, the European Space Agency and Italian Space Agency. The mission is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Space Science, Washington DC. JPL is a division of the California Institute of Technology, Pasadena, CA.

  1. Optical contact micrometer

    SciTech Connect

    Jacobson, Steven D.

    2014-08-19

    Certain examples provide optical contact micrometers and methods of use. An example optical contact micrometer includes a pair of opposable lenses to receive an object and immobilize the object in a position. The example optical contact micrometer includes a pair of opposable mirrors positioned with respect to the pair of lenses to facilitate viewing of the object through the lenses. The example optical contact micrometer includes a microscope to facilitate viewing of the object through the lenses via the mirrors; and an interferometer to obtain one or more measurements of the object.

  2. Development of a high-resolution soft x-ray (30--1500 eV) beamline at the Advanced Light Source and its use for the study of angle-resolved photoemission extended fine structure

    SciTech Connect

    Huff, W R.A.

    1996-02-01

    ALS Bending magnet beamline 9.3.2 is for high resolution spectroscopy, with circularly polarized light. Fixed included-angle SGM uses three gratings for 30--1500 eV photons; circular polarization is produced by an aperture for selecting the beam above or below the horizontal plane. Photocurrent from upper and lower jaws of entrance slit sets a piezoelectric drive feedback loop on the vertically deflecting mirror for stable beam. End station has a movable platform. With photomeission data from Stanford, structure of c(2{times}2)P/Fe(100) was determined using angle-resolved photoemission extended fine structure (ARPEFS). Multiple-scattering spherical-wave (MSSW) calculations indicate that P atoms adsorb in fourfold hollow sites 1.02A above the first Fe layer. Self-consistent-field X{alpha} scattered wave calculation confirm that the Fe{sub 1}-Fe{sub 2} space is contracted for S/Fe but not for P/Fe; comparison is made to atomic N and O on Fe(100). Final-state effects on ARPEFS curves used literature data from the S 1s and 2p core levels of c(2{times}2)S/Ni(001); a generalized Ramsauer-Townsend splitting is present in the 1s but not 2p data. An approximate method for analyzing ARPEFS data from a non-s initial state using only the higher-{ell} partial wave was tested successfully. ARPEFS data from clean surfaces were collected normal to Ni(111) (3p core levels) and 5{degree} off-normal from Cu(111)(3s, 3p). Fourier transforms (FT) resemble adsorbate systems, showing backscattering signals from atoms up to 4 layers below emitters. 3p FTs show scattering from 6 nearest neighbors in the same crystal layer as the emitters. MSSW calulation indicate that Cu 3p photoemission is mostly d-wave. FTs also indicate double-scattering and single-scattering from laterally distant atoms; calculations indicate that the signal is dominated by photoemission from the first 2 crystal layers.

  3. Stride angle as a novel indicator of running economy in well-trained runners.

    PubMed

    Santos-Concejero, Jordan; Tam, Nicholas; Granados, Cristina; Irazusta, Jon; Bidaurrazaga-Letona, Iraia; Zabala-Lili, Jon; Gil, Susana M

    2014-07-01

    The main purpose of this study was to investigate the relationship between a novel biomechanical variable, the stride angle, and running economy (RE) in a homogeneous group of long-distance athletes. Twenty-five well-trained male runners completed 4-minute running stages on a treadmill at different set velocities. During the test, biomechanical variables such as stride angle, swing time, ground contact time, stride length, stride frequency, and the different sub-phases of ground contact were recorded using an optical measurement system. VO2 values at velocities below the lactate threshold were measured to calculate RE. Stride angle was negatively correlated with RE at every speed (p < 0.001, large effect sizes). Running economy was also negatively correlated with swing phase and positively correlated with ground contact time and running performance according to the best 10-km race time (p ≤ 0.05, moderate and large effect sizes). Last, stride angle was correlated with ground contact time at every speed (p < 0.001, large effect sizes). In conclusion, it seems that optimal execution of stride angle allows runners to minimize contact time during ground contact, whereby facilitating a better RE. Coaches and/or athletes may find stride angle a useful and easily obtainable measure to track and make alterations to running technique, because changes in stride angle may influence the energy cost of running and lead to improved performance.

  4. Asymptotic solutions for the relaxation of the contact line in the Wilhelmy-plate geometry: The contact line dissipation approach.

    PubMed

    Iliev, Stanimir; Pesheva, Nina; Iliev, Dimitar

    2010-01-01

    The relaxation of straight contact lines is considered in the context of the Wilhelmy-plate experiment: a homogeneous solid plate is moving vertically at constant velocity in a tank of liquid in the partial wetting regime. We apply the contact line dissipation approach to describe the quasistatic relaxation of the contact line toward the stationary state (below the entrainment transition). Asymptotic solutions are derived from the differential equations describing the capillary rise height and the contact angle relaxation for small initial deviations of the height from the final stationary value in the model considering the friction dissipation at the moving contact line, in the model considering the viscous flow dissipation in the wedge, and in the combined model taking into account both channels of dissipation. We find that for all models the time relaxation of the height and the cosine of the contact angle are given by sums of exponential functions up to a second order in the expansion of the small parameter. We analyze the implications which follow when only one dissipation channel is taken into account and compare them to the case when both dissipation channels are included. The asymptotic solutions are compared with experimental results and with numerically obtained solutions which are based on hydrodynamic approach in lubrication approximation with and without a correction factor for finite contact angles. The best description of the experimental data, based on multicriteria testing, is obtained with the combined contact line dissipation model which takes into account both channels of dissipation. PMID:20365384

  5. Language Contact: An Introduction.

    ERIC Educational Resources Information Center

    Thomason, Sarah G.

    This book surveys situations in which language contact arises and focuses on what happens to the languages themselves: sometimes nothing, sometimes the incorporation of new words, sometimes the spread of new sounds and sentence structures across many languages and wide swathes of territory. It outlines the origins and results of contact-induced…

  6. Predictive models for moving contact line flows

    NASA Technical Reports Server (NTRS)

    Rame, Enrique; Garoff, Stephen

    2003-01-01

    Modeling flows with moving contact lines poses the formidable challenge that the usual assumptions of Newtonian fluid and no-slip condition give rise to a well-known singularity. This singularity prevents one from satisfying the contact angle condition to compute the shape of the fluid-fluid interface, a crucial calculation without which design parameters such as the pressure drop needed to move an immiscible 2-fluid system through a solid matrix cannot be evaluated. Some progress has been made for low Capillary number spreading flows. Combining experimental measurements of fluid-fluid interfaces very near the moving contact line with an analytical expression for the interface shape, we can determine a parameter that forms a boundary condition for the macroscopic interface shape when Ca much les than l. This parameter, which plays the role of an "apparent" or macroscopic dynamic contact angle, is shown by the theory to depend on the system geometry through the macroscopic length scale. This theoretically established dependence on geometry allows this parameter to be "transferable" from the geometry of the measurement to any other geometry involving the same material system. Unfortunately this prediction of the theory cannot be tested on Earth.

  7. Noneczematous Contact Dermatitis

    PubMed Central

    Foti, Caterina; Vestita, Michelangelo; Angelini, Gianni

    2013-01-01

    Irritant or allergic contact dermatitis usually presents as an eczematous process, clinically characterized by erythematoedematovesicous lesions with intense itching in the acute phase. Such manifestations become erythematous-scaly as the condition progresses to the subacute phase and papular-hyperkeratotic in the chronic phase. Not infrequently, however, contact dermatitis presents with noneczematous features. The reasons underlying this clinical polymorphism lie in the different noxae and contact modalities, as well as in the individual susceptibility and the various targeted cutaneous structures. The most represented forms of non-eczematous contact dermatitis include the erythema multiforme-like, the purpuric, the lichenoid, and the pigmented kinds. These clinical entities must obviously be discerned from the corresponding “pure” dermatitis, which are not associated with contact with exogenous agents. PMID:24109520

  8. Contact dermatitis in athletes.

    PubMed

    Kockentiet, Brett; Adams, Brian B

    2007-06-01

    Athletes face numerous hazards in their daily activities. An athlete's skin, in particular, endures repeated exposure to trauma, heat, moisture, and numerous allergens and chemicals. These factors combine with other unique and less well-defined genetically predisposing factors in the athlete's skin to cause both allergic contact dermatitis (ACD) and irritant contact dermatitis (ICD). As with other cases of contact dermatitis, these eruptions in athletes present as a spectrum of acute to subacute to chronic dermatitis. Recognizing the unique environmental irritants and allergens encountered by athletes is paramount to facilitate appropriate therapy and prevention. This review comprehensively examines the literature on contact dermatitis in athletes. The different types of contact dermatitis have been classified under sport-specific subheadings. Furthermore, within each subheading, both ACD and ICD types are discussed.

  9. Thermally activated depinning motion of contact lines in pseudopartial wetting.

    PubMed

    Du, Lingguo; Bodiguel, Hugues; Colin, Annie

    2014-07-01

    We investigate pressure-driven motion of liquid-liquid menisci in circular tubes, for systems in pseudopartial wetting conditions. The originality of this type of wetting lies in the coexistence of a macroscopic contact angle with a wetting liquid film covering the solid surface. Focusing on small capillary numbers, we report observations of an apparent contact angle hysteresis at first sight similar to the standard partial wetting case. However, this apparent hysteresis exhibits original features. We observe very long transient regimes before steady state, up to several hundreds of seconds. Furthermore, in steady state, the velocities are nonzero, meaning that the contact line is not strongly pinned to the surface defects, but are very small. The velocity of the contact line tends to vanish near the equilibrium contact angle. These observations are consistent with the thermally activated depinning theory that has been proposed to describe partial wetting systems on disordered substrates and suggest that a single physical mechanism controls both the hysteresis (or the pinning) and the motion of the contact line. The proposed analysis leads to the conclusion that the depinning activated energy is lower with pseudopartial wetting systems than with partial wetting ones, allowing the direct observation of the thermally activated motion of the contact line. PMID:25122310

  10. Allergic contact dermatitis.

    PubMed

    Becker, Detlef

    2013-07-01

    Allergic contact dermatitis is a frequent inflammatory skin disease. The suspected diagnosis is based on clinical symptoms, a plausible contact to allergens and a suitable history of dermatitis. Differential diagnoses should be considered only after careful exclusion of any causal contact sensitization. Hence, careful diagnosis by patch testing is of great importance. Modifications of the standardized test procedure are the strip patch test and the repeated open application test. The interpretation of the SLS (sodium lauryl sulfate) patch test as well as testing with the patients' own products and working materials are potential sources of error. Accurate patch test reading is affected in particular by the experience and individual factors of the examiner. Therefore, a high degree of standardization and continuous quality control is necessary and may be supported by use of an online patch test reading course made available by the German Contact Dermatitis Research Group. A critical relevance assessment of allergic patch test reactions helps to avoid relapses and the consideration of differential diagnoses. Any allergic test reaction should be documented in an allergy ID card including the INCI name, if appropriate. The diagnostics of allergic contact dermatitis is endangered by a seriously reduced financing of patch testing by the German statutory health insurances. Restrictive regulations by the German Drug Law block the approval of new contact allergens for routine patch testing. Beside the consistent avoidance of allergen contact, temporary use of systemic and topical corticosteroids is the therapy of first choice.

  11. Can Imagined Interactions Produce Positive Perceptions?: Reducing Prejudice through Simulated Social Contact

    ERIC Educational Resources Information Center

    Crisp, Richard J.; Turner, Rhiannon N.

    2009-01-01

    The contact hypothesis states that, under the right conditions, contact between members of different groups leads to more positive intergroup relations. The authors track recent trends in contact theory to the emergence of extended, or indirect, forms of contact. These advances lead to an intriguing proposition: that simply imagining intergroup…

  12. Small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Cousin, Fabrice

    2015-10-01

    Small Angle Neutron Scattering (SANS) is a technique that enables to probe the 3-D structure of materials on a typical size range lying from ˜ 1 nm up to ˜ a few 100 nm, the obtained information being statistically averaged on a sample whose volume is ˜ 1 cm3. This very rich technique enables to make a full structural characterization of a given object of nanometric dimensions (radius of gyration, shape, volume or mass, fractal dimension, specific area…) through the determination of the form factor as well as the determination of the way objects are organized within in a continuous media, and therefore to describe interactions between them, through the determination of the structure factor. The specific properties of neutrons (possibility of tuning the scattering intensity by using the isotopic substitution, sensitivity to magnetism, negligible absorption, low energy of the incident neutrons) make it particularly interesting in the fields of soft matter, biophysics, magnetic materials and metallurgy. In particular, the contrast variation methods allow to extract some informations that cannot be obtained by any other experimental techniques. This course is divided in two parts. The first one is devoted to the description of the principle of SANS: basics (formalism, coherent scattering/incoherent scattering, notion of elementary scatterer), form factor analysis (I(q→0), Guinier regime, intermediate regime, Porod regime, polydisperse system), structure factor analysis (2nd Virial coefficient, integral equations, characterization of aggregates), and contrast variation methods (how to create contrast in an homogeneous system, matching in ternary systems, extrapolation to zero concentration, Zero Averaged Contrast). It is illustrated by some representative examples. The second one describes the experimental aspects of SANS to guide user in its future experiments: description of SANS spectrometer, resolution of the spectrometer, optimization of spectrometer

  13. Critical dimension small angle X-ray scattering measurements of FinFET and 3D memory structures

    NASA Astrophysics Data System (ADS)

    Settens, Charles; Bunday, Benjamin; Thiel, Brad; Kline, R. Joseph; Sunday, Daniel; Wang, Chengqing; Wu, Wen-li; Matyi, Richard

    2013-04-01

    We have demonstrated that transmission critical dimension small angle X-ray scattering (CD-SAXS) provides high accuracy and precision CD measurements on advanced 3D microelectronic architectures. The competitive advantage of CD-SAXS over current 3D metrology methods such as optical scatterometry is that CD-SAXS is able to decouple and fit cross-section parameters without any significant parameter cross-correlations. As the industry aggressively scales beyond the 22 nm node, CD-SAXS can be used to quantitatively measure nanoscale deviations in the average crosssections of FinFETs and high-aspect ratio (HAR) memory devices. Fitting the average cross-section of 18:1 isolated HAR contact holes with an effective trapezoid model yielded an average pitch of 796.9 +/- 0.4 nm, top diameter of 70.3 +/- 0.9 nm, height of 1088 +/- 4 nm, and sidewall angle below 0.1°. Simulations of dense 40:1 HAR contact holes and FinFET fin-gate crossbar structures have been analyzed using CD-SAXS to inquire the theoretical precision of the technique to measure important process parameters such as fin CD, height, and sidewall angle; BOX etch recess, thickness of hafnium oxide and titanium nitride layers; gate CD, height, and sidewall angle; and hafnium oxide and titanium nitride etch recess. The simulations of HAR and FinFET structures mimic the characteristics of experimental data collected at a synchrotron x-ray source. Using the CD-SAXS simulator, we estimate the measurement capabilities for smaller similar structures expected at future nodes to predict the applicability of this technique to fulfill important CD metrology needs.

  14. Toward patient-specific articular contact mechanics

    PubMed Central

    Ateshian, Gerard A.; Henak, Corinne R.; Weiss, Jeffrey A.

    2015-01-01

    The mechanics of contacting cartilage layers is fundamentally important to understanding the development, homeostasis and pathology of diarthrodial joints. Because of the highly nonlinear nature of both the materials and the contact problem itself, numerical methods such as the finite element method are typically incorporated to obtain solutions. Over the course of five decades, we have moved from an initial qualitative understanding of articular cartilage material behavior to the ability to perform complex, three-dimensional contact analysis, including multiphasic material representations. This history includes the development of analytical and computational contact analysis methods that now provide the ability to perform highly nonlinear analyses. Numerical implementations of contact analysis based on the finite element method are rapidly advancing and will soon enable patient-specific analysis of joint contact mechanics using models based on medical image data. In addition to contact stress on the articular surfaces, these techniques can predict variations in strain and strain through the cartilage layers, providing the basis to predict damage and failure. This opens up exciting areas for future research and application to patient-specific diagnosis and treatment planning applied to a variety of pathologies that affect joint function and cartilage homeostasis. PMID:25698236

  15. Toward patient-specific articular contact mechanics.

    PubMed

    Ateshian, Gerard A; Henak, Corinne R; Weiss, Jeffrey A

    2015-03-18

    The mechanics of contacting cartilage layers is fundamentally important to understanding the development, homeostasis and pathology of diarthrodial joints. Because of the highly nonlinear nature of both the materials and the contact problem itself, numerical methods such as the finite element method are typically incorporated to obtain solutions. Over the course of five decades, we have moved from an initial qualitative understanding of articular cartilage material behavior to the ability to perform complex, three-dimensional contact analysis, including multiphasic material representations. This history includes the development of analytical and computational contact analysis methods that now provide the ability to perform highly nonlinear analyses. Numerical implementations of contact analysis based on the finite element method are rapidly advancing and will soon enable patient-specific analysis of joint contact mechanics using models based on medical image data. In addition to contact stress on the articular surfaces, these techniques can predict variations in strain and strain through the cartilage layers, providing the basis to predict damage and failure. This opens up exciting areas for future research and application to patient-specific diagnosis and treatment planning applied to a variety of pathologies that affect joint function and cartilage homeostasis.

  16. Telescopic vision contact lens

    NASA Astrophysics Data System (ADS)

    Tremblay, Eric J.; Beer, R. Dirk; Arianpour, Ashkan; Ford, Joseph E.

    2011-03-01

    We present the concept, optical design, and first proof of principle experimental results for a telescopic contact lens intended to become a visual aid for age-related macular degeneration (AMD), providing magnification to the user without surgery or external head-mounted optics. Our contact lens optical system can provide a combination of telescopic and non-magnified vision through two independent optical paths through the contact lens. The magnified optical path incorporates a telescopic arrangement of positive and negative annular concentric reflectors to achieve 2.8x - 3x magnification on the eye, while light passing through a central clear aperture provides unmagnified vision.

  17. Optical contacting of quartz

    NASA Technical Reports Server (NTRS)

    Payne, L. L.

    1982-01-01

    The strength of the bond between optically contacted quartz surfaces was investigated. The Gravity Probe-B (GP-B) experiment to test the theories of general relativity requires extremely precise measurements. The quartz components of the instruments to make these measurements must be held together in a very stable unit. Optical contacting is suggested as a possible method of joining these components. The fundamental forces involved in optical contacting are reviewed and relates calculations of these forces to the results obtained in experiments.

  18. Probe Without Moving Parts Measures Flow Angle

    NASA Technical Reports Server (NTRS)

    Corda, Stephen; Vachon, M. Jake

    2003-01-01

    The measurement of local flow angle is critical in many fluid-dynamic applications, including the aerodynamic flight testing of new aircraft and flight systems. Flight researchers at NASA Dryden Flight Research Center have recently developed, flight-tested, and patented the force-based flow-angle probe (FLAP), a novel, force-based instrument for the measurement of local flow direction. Containing no moving parts, the FLAP may provide greater simplicity, improved accuracy, and increased measurement access, relative to conventional moving vane-type flow-angle probes. Forces in the FLAP can be measured by various techniques, including those that involve conventional strain gauges (based on electrical resistance) and those that involve more advanced strain gauges (based on optical fibers). A correlation is used to convert force-measurement data to the local flow angle. The use of fiber optics will enable the construction of a miniature FLAP, leading to the possibility of flow measurement in very small or confined regions. This may also enable the tufting of a surface with miniature FLAPs, capable of quantitative flow-angle measurements, similar to attaching yarn tufts for qualitative measurements. The prototype FLAP was a small, aerodynamically shaped, low-aspect-ratio fin about 2 in. (approximately equal to 5 cm) long, 1 in. (approximately equal to 2.5 cm) wide, and 0.125 in. (approximately equal to 0.3 cm) thick (see Figure 1). The prototype FLAP included simple electrical-resistance strain gauges for measuring forces. Four strain gauges were mounted on the FLAP; two on the upper surface and two on the lower surface. The gauges were connected to form a full Wheatstone bridge, configured as a bending bridge. In preparation for a flight test, the prototype FLAP was mounted on the airdata boom of a flight-test fixture (FTF) on the NASA Dryden F-15B flight research airplane.

  19. [Angle-closure chronic glaucoma].

    PubMed

    Lachkar, Y

    2003-10-01

    The incidence of chronic angle closure glaucoma is considerably greater than the incidence of the acute type. This type of glaucoma may mimic primary open angle glaucoma with visual field deterioration, optic nerve alteration and intraocular pressure elevation with a quiet painless eye. Its diagnosis is based on indentation gonioscopy showing peripheral anterior synechiae. The mechanisms of angle closure are the pupillary block, the plateau iris configuration and the creeping form. The treatment of chronic angle closure glaucoma is based on laser peripheral iridotomy. PMID:14646832

  20. The Critical Angle Can Override the Brewster Angle

    ERIC Educational Resources Information Center

    Froehle, Peter H.

    2009-01-01

    As a culminating activity in their study of optics, my students investigate polarized light and the Brewster angle. In this exercise they encounter a situation in which it is impossible to measure the Brewster angle for light reflecting from a particular surface. This paper describes the activity and explains the students' observations.

  1. Magic angle spinning NMR of viruses.

    PubMed

    Quinn, Caitlin M; Lu, Manman; Suiter, Christopher L; Hou, Guangjin; Zhang, Huilan; Polenova, Tatyana

    2015-04-01

    Viruses, relatively simple pathogens, are able to replicate in many living organisms and to adapt to various environments. Conventional atomic-resolution structural biology techniques, X-ray crystallography and solution NMR spectroscopy provided abundant information on the structures of individual proteins and nucleic acids comprising viruses; however, viral assemblies are not amenable to analysis by these techniques because of their large size, insolubility, and inherent lack of long-range order. In this article, we review the recent advances in magic angle spinning NMR spectroscopy that enabled atomic-resolution analysis of structure and dynamics of large viral systems and give examples of several exciting case studies. PMID:25919197

  2. Magic Angle Spinning NMR of Viruses

    PubMed Central

    Quinn, Caitlin; Lu, Manman; Suiter, Christopher L.; Hou, Guangjin; Zhang, Huilan; Polenova, Tatyana

    2015-01-01

    Viruses, relatively simple pathogens, are able to replicate in many living organisms and to adapt to various environments. Conventional atomic-resolution structural biology techniques, X-ray crystallography and solution NMR spectroscopy provided abundant information on the structures of individual proteins and nucleic acids comprising viruses; however, viral assemblies are not amenable to analysis by these techniques because of their large size, insolubility, and inherent lack of long-range order. In this article, we review the recent advances in magic angle spinning NMR spectroscopy that enabled atomic-resolution analysis of structure and dynamics of large viral systems and give examples of several exciting case studies. PMID:25919197

  3. Fragrance allergic contact dermatitis.

    PubMed

    Cheng, Judy; Zug, Kathryn A

    2014-01-01

    Fragrances are a common cause of allergic contact dermatitis in Europe and in North America. They can affect individuals at any age and elicit a spectrum of reactions from contact urticaria to systemic contact dermatitis. Growing recognition of the widespread use of fragrances in modern society has fueled attempts to prevent sensitization through improved allergen identification, labeling, and consumer education. This review provides an overview and update on fragrance allergy. Part 1 discusses the epidemiology and evaluation of suspected fragrance allergy. Part 2 reviews screening methods, emerging fragrance allergens, and management of patients with fragrance contact allergy. This review concludes by examining recent legislation on fragrances and suggesting potential additions to screening series to help prevent and detect fragrance allergy.

  4. Occupational Contact Dermatitis

    PubMed Central

    2008-01-01

    Occupational contact dermatitis accounts for 90% of all cases of work-related cutaneous disorders. It can be divided into irritant contact dermatitis, which occurs in 80% of cases, and allergic contact dermatitis. In most cases, both types will present as eczematous lesions on exposed parts of the body, notably the hands. Accurate diagnosis relies on meticulous history taking, thorough physical examination, careful reading of Material Safety Data Sheets to distinguish between irritants and allergens, and comprehensive patch testing to confirm or rule out allergic sensitization. This article reviews the pathogenesis and clinical manifestations of occupational contact dermatitis and provides diagnostic guidelines and a rational approach to management of these often frustrating cases. PMID:20525126

  5. Contacting American Overseas Schools.

    ERIC Educational Resources Information Center

    Engelhardt, David

    1993-01-01

    Provides contacts for architects or educational consultants who wish to work overseas. Cites a directory, newsletters, newspapers, and associations focused on educators involved with independent overseas schools that are organized around the United States curriculum. (MLF)

  6. Relay contact monitoring system

    SciTech Connect

    Mehta, V.

    1994-01-11

    A switching system for switching on and off heating and air conditioning units in an environmental control system. The switching system includes a thermostat and a relay conductively coupled to the thermostat. The relay has a contact, which is responsive to a change signal for changing its position. The system further includes a programmable monitor having predetermined positions stored in a memory. The monitor is conductively coupled to the contact and to the thermostat for continually determining the position of the contact, and for sending a change signal to the relay for switching the position of the contact, as needed, to be in conformance with a predetermined position stored in the memory. 3 figs.

  7. Thermal conductance of carbon nanotube contacts: Molecular dynamics simulations and general description of the contact conductance

    NASA Astrophysics Data System (ADS)

    Salaway, Richard N.; Zhigilei, Leonid V.

    2016-07-01

    The contact conductance of carbon nanotube (CNT) junctions is the key factor that controls the collective heat transfer through CNT networks or CNT-based materials. An improved understanding of the dependence of the intertube conductance on the contact structure and local environment is needed for predictive computational modeling or theoretical description of the effective thermal conductivity of CNT materials. To investigate the effect of local structure on the thermal conductance across CNT-CNT contact regions, nonequilibrium molecular dynamics (MD) simulations are performed for different intertube contact configurations (parallel fully or partially overlapping CNTs and CNTs crossing each other at different angles) and local structural environments characteristic of CNT network materials. The results of MD simulations predict a stronger CNT length dependence present over a broader range of lengths than has been previously reported and suggest that the effect of neighboring junctions on the conductance of CNT-CNT junctions is weak and only present when the CNTs that make up the junctions are within the range of direct van der Waals interaction with each other. A detailed analysis of the results obtained for a diverse range of intertube contact configurations reveals a nonlinear dependence of the conductance on the contact area (or number of interatomic intertube interactions) and suggests larger contributions to the conductance from areas of the contact where the density of interatomic intertube interactions is smaller. An empirical relation accounting for these observations and expressing the conductance of an arbitrary contact configuration through the total number of interatomic intertube interactions and the average number of interatomic intertube interactions per atom in the contact region is proposed. The empirical relation is found to provide a good quantitative description of the contact conductance for various CNT configurations investigated in the MD

  8. ELECTRIC CONTACT MEANS

    DOEpatents

    Grear, J.W. Jr.

    1959-03-10

    A switch adapted to maintain electrical connections under conditions of vibration or acceleration is described. According to the invention, thc switch includes a rotatable arm carrying a conductive bar arranged to close against two contacts spaced in the same plane. The firm and continuous engagement of the conductive bar with the contacts is acheived by utilizeing a spring located betwenn the vbar and athe a rem frzme and slidable mounting the bar in channel between two arms suspendef from the arm frame.

  9. Lettuce contact allergy.

    PubMed

    Paulsen, Evy; Andersen, Klaus E

    2016-02-01

    Lettuce (Lactuca sativa L.) and its varieties are important vegetable crops worldwide. They are also well-known, rarely reported, causes of contact allergy. As lettuce allergens and extracts are not commercially available, the allergy may be underdiagnosed. The aims of this article are to present new data on lettuce contact allergy and review the literature. Lettuce is weakly allergenic, and occupational cases are mainly reported. Using aimed patch testing in Compositae-allergic patients, two recent Danish studies showed prevalence rates of positive lettuce reactions of 11% and 22%. The majority of cases are non-occupational, and may partly be caused by cross-reactivity. The sesquiterpene lactone mix seems to be a poor screening agent for lettuce contact allergy, as the prevalence of positive reactions is significantly higher in non-occupationally sensitized patients. Because of the easy degradability of lettuce allergens, it is recommended to patch test with freshly cut lettuce stem and supplement this with Compositae mix. As contact urticaria and protein contact dermatitis may present as dermatitis, it is important to perform prick-to-prick tests, and possibly scratch patch tests as well. Any person who is occupationally exposed to lettuce for longer periods, especially atopics, amateur gardeners, and persons keeping lettuce-eating pets, is potentially at risk of developing lettuce contact allergy.

  10. A superconducting large-angle magnetic suspension

    NASA Astrophysics Data System (ADS)

    Downer, James R.; Anastas, George V., Jr.; Bushko, Dariusz A.; Flynn, Frederick J.; Goldie, James H.; Gondhalekar, Vijay; Hawkey, Timothy J.; Hockney, Richard L.; Torti, Richard P.

    1992-12-01

    SatCon Technology Corporation has completed a Small Business Innovation Research (SBIR) Phase 2 program to develop a Superconducting Large-Angle Magnetic Suspension (LAMS) for the NASA Langley Research Center. The Superconducting LAMS was a hardware demonstration of the control technology required to develop an advanced momentum exchange effector. The Phase 2 research was directed toward the demonstration for the key technology required for the advanced concept CMG, the controller. The Phase 2 hardware consists of a superconducting solenoid ('source coils') suspended within an array of nonsuperconducting coils ('control coils'), a five-degree-of-freedom positioning sensing system, switching power amplifiers, and a digital control system. The results demonstrated the feasibility of suspending the source coil. Gimballing (pointing the axis of the source coil) was demonstrated over a limited range. With further development of the rotation sensing system, enhanced angular freedom should be possible.

  11. A superconducting large-angle magnetic suspension

    NASA Technical Reports Server (NTRS)

    Downer, James R.; Anastas, George V., Jr.; Bushko, Dariusz A.; Flynn, Frederick J.; Goldie, James H.; Gondhalekar, Vijay; Hawkey, Timothy J.; Hockney, Richard L.; Torti, Richard P.

    1992-01-01

    SatCon Technology Corporation has completed a Small Business Innovation Research (SBIR) Phase 2 program to develop a Superconducting Large-Angle Magnetic Suspension (LAMS) for the NASA Langley Research Center. The Superconducting LAMS was a hardware demonstration of the control technology required to develop an advanced momentum exchange effector. The Phase 2 research was directed toward the demonstration for the key technology required for the advanced concept CMG, the controller. The Phase 2 hardware consists of a superconducting solenoid ('source coils') suspended within an array of nonsuperconducting coils ('control coils'), a five-degree-of-freedom positioning sensing system, switching power amplifiers, and a digital control system. The results demonstrated the feasibility of suspending the source coil. Gimballing (pointing the axis of the source coil) was demonstrated over a limited range. With further development of the rotation sensing system, enhanced angular freedom should be possible.

  12. Effect of leaning angle of gecko-inspired slanted polymer nanohairs on dry adhesion

    NASA Astrophysics Data System (ADS)

    Jeong, Hoon Eui; Lee, Jin-Kwan; Kwak, Moon Kyu; Moon, Sang Heup; Suh, Kahp Yang

    2010-01-01

    We present analysis of adhesion properties of angled polymer nanohairs with a wide range of leaning angles from 0° to 45° and ultraviolet (UV)-curable polyurethane acrylate (PUA) materials of two different elastic moduli (19.8 and 320 MPa). It is demonstrated that shear adhesion and adhesion hysteresis can be greatly enhanced by increasing the leaning angle of nanohairs both for soft and hard materials due to increased contact area and reduced structural stiffness.

  13. Ramp Angle, Not Plateau Height, Influences Transition Strategies.

    PubMed

    Sheehan, Riley C; Gottschall, Jinger S

    2016-10-01

    In a previous study, we found that participants modified how they transitioned onto and off of ramp configurations depending upon the incline. While the transition strategies were originally attributed to ramp angles, it is possible that the plateau influenced the strategies since the final surface height also differed. Ultimately, for the current study, we hypothesized that an individual's transition strategies would have significant main effects for ramp angle, but not plateau height. Twelve healthy, young adults transitioned onto 3 distinct ramp configurations, a 2.4-m ramp angled at 12.5° ending at a plateau height of 53 cm, a 1.2-m ramp angled at 23.5° ending at a plateau height of 53 cm, and a 2.4-m ramp angled at 23.5° ending at a plateau height of 99.5 cm. Kinematics, kinetics, and muscle activity were measured during the stance phase before contacting the ramp. In support of our hypothesis, impact peak, active peak, and all of the muscle activity variables had a significant main effect for ramp angle, with greater vertical force peaks and muscle activity on steeper ramp transitions. These findings support our previous interpretation that individuals use estimations of ramp angle, not plateau height, to determine their transition strategies.

  14. Measuring Angles in Physical Therapy.

    ERIC Educational Resources Information Center

    Greeley, Nansee; Offerman, Theresa Reardon

    1997-01-01

    Features articles about physical therapy and its history as related to geometry through measurement of body angles. Includes open-ended worksheets for mathematics activities that introduce students to angle measurement, data analysis, and mathematical tools. Activities include: (1) Making Your Own Goniometer; (2) Range of Motion; (3) Active versus…

  15. Effect of acetabular cup abduction angle on wear of ultrahigh-molecular-weight polyethylene in hip simulator testing.

    PubMed

    Korduba, Laryssa A; Essner, Aaron; Pivec, Robert; Lancin, Perry; Mont, Michael A; Wang, Aiguo; Delanois, Ronald E

    2014-10-01

    The effect of acetabular component positioning on the wear rates of metal-on-polyethylene articulations has not been extensively studied. Placement of acetabular cups at abduction angles of more than 40° has been noted as a possible reason for early failure caused by increased wear. We conducted a study to evaluate the effects of different acetabular cup abduction angles on polyethylene wear rate, wear area, contact pressure, and contact area. Our in vitro study used a hip joint simulator and finite element analysis to assess the effects of cup orientation at 4 angles (0°, 40°, 50°, 70°) on wear and contact properties. Polyethylene bearings with 28-mm cobalt-chrome femoral heads were cycled in an environment mimicking in vivo joint fluid to determine the volumetric wear rate after 10 million cycles. Contact pressure and contact area for each cup abduction angle were assessed using finite element analysis. Results were correlated with cup abduction angles to determine if there were any differences among the 4 groups. The inverse relationship between volumetric wear rate and acetabular cup inclination angle demonstrated less wear with steeper cup angles. The largest abduction angle (70°) had the lowest contact area, largest contact pressure, and smallest head coverage. Conversely, the smallest abduction angle (0°) had the most wear and most head coverage. Polyethylene wear after total hip arthroplasty is a major cause of osteolysis and aseptic loosening, which may lead to premature implant failure. Several studies have found that high wear rates for cups oriented at steep angles contributed to their failure. Our data demonstrated that larger cup abduction angles were associated with lower, not higher, wear. However, this potentially "protective" effect is likely counteracted by other complications of steep cup angles, including impingement, instability, and edge loading. These factors may be more relevant in explaining why implants fail at a higher rate if

  16. Effect of acetabular cup abduction angle on wear of ultrahigh-molecular-weight polyethylene in hip simulator testing.

    PubMed

    Korduba, Laryssa A; Essner, Aaron; Pivec, Robert; Lancin, Perry; Mont, Michael A; Wang, Aiguo; Delanois, Ronald E

    2014-10-01

    The effect of acetabular component positioning on the wear rates of metal-on-polyethylene articulations has not been extensively studied. Placement of acetabular cups at abduction angles of more than 40° has been noted as a possible reason for early failure caused by increased wear. We conducted a study to evaluate the effects of different acetabular cup abduction angles on polyethylene wear rate, wear area, contact pressure, and contact area. Our in vitro study used a hip joint simulator and finite element analysis to assess the effects of cup orientation at 4 angles (0°, 40°, 50°, 70°) on wear and contact properties. Polyethylene bearings with 28-mm cobalt-chrome femoral heads were cycled in an environment mimicking in vivo joint fluid to determine the volumetric wear rate after 10 million cycles. Contact pressure and contact area for each cup abduction angle were assessed using finite element analysis. Results were correlated with cup abduction angles to determine if there were any differences among the 4 groups. The inverse relationship between volumetric wear rate and acetabular cup inclination angle demonstrated less wear with steeper cup angles. The largest abduction angle (70°) had the lowest contact area, largest contact pressure, and smallest head coverage. Conversely, the smallest abduction angle (0°) had the most wear and most head coverage. Polyethylene wear after total hip arthroplasty is a major cause of osteolysis and aseptic loosening, which may lead to premature implant failure. Several studies have found that high wear rates for cups oriented at steep angles contributed to their failure. Our data demonstrated that larger cup abduction angles were associated with lower, not higher, wear. However, this potentially "protective" effect is likely counteracted by other complications of steep cup angles, including impingement, instability, and edge loading. These factors may be more relevant in explaining why implants fail at a higher rate if

  17. Spinning angle optical calibration apparatus

    DOEpatents

    Beer, Stephen K.; Pratt, II, Harold R.

    1991-01-01

    An optical calibration apparatus is provided for calibrating and reproducing spinning angles in cross-polarization, nuclear magnetic resonance spectroscopy. An illuminated magnifying apparatus enables optical setting an accurate reproducing of spinning "magic angles" in cross-polarization, nuclear magnetic resonance spectroscopy experiments. A reference mark scribed on an edge of a spinning angle test sample holder is illuminated by a light source and viewed through a magnifying scope. When the "magic angle" of a sample material used as a standard is attained by varying the angular position of the sample holder, the coordinate position of the reference mark relative to a graduation or graduations on a reticle in the magnifying scope is noted. Thereafter, the spinning "magic angle" of a test material having similar nuclear properties to the standard is attained by returning the sample holder back to the originally noted coordinate position.

  18. Spinning angle optical calibration apparatus

    SciTech Connect

    Beer, S.K.; Pratt, H.R. II.

    1989-09-12

    An optical calibration apparatus is provided for calibrating and reproducing spinning angles in cross-polarization, nuclear magnetic resonance spectroscopy. An illuminated magnifying apparatus enables optical setting and accurate reproducing of spinning magic angles in cross-polarization, nuclear magnetic resonance spectroscopy experiments. A reference mark scribed on an edge of a spinning angle test sample holder is illuminated by a light source and viewed through a magnifying scope. When the magic angle of a sample material used as a standard is attained by varying the angular position of the sample holder, the coordinate position of the reference mark relative to a graduation or graduations on a reticle in the magnifying scope is noted. Thereafter, the spinning magic angle of a test material having similar nuclear properties to the standard is attained by returning the sample holder back to the originally noted coordinate position. 2 figs.

  19. The contact caveat: negative contact predicts increased prejudice more than positive contact predicts reduced prejudice.

    PubMed

    Barlow, Fiona Kate; Paolini, Stefania; Pedersen, Anne; Hornsey, Matthew J; Radke, Helena R M; Harwood, Jake; Rubin, Mark; Sibley, Chris G

    2012-12-01

    Contact researchers have largely overlooked the potential for negative intergroup contact to increase prejudice. In Study 1, we tested the interaction between contact quantity and valence on prejudice toward Black Australians (n = 1,476), Muslim Australians (n = 173), and asylum seekers (n = 293). In all cases, the association between contact quantity and prejudice was moderated by its valence, with negative contact emerging as a stronger and more consistent predictor than positive contact. In Study 2, White Americans (n = 441) indicated how much positive and negative contact they had with Black Americans on separate measures. Although both quantity of positive and negative contact predicted racism and avoidance, negative contact was the stronger predictor. Furthermore, negative (but not positive) contact independently predicted suspicion about Barack Obama's birthplace. These results extend the contact hypothesis by issuing an important caveat: Negative contact may be more strongly associated with increased racism and discrimination than positive contact is with its reduction.

  20. Contact Lenses for Vision Correction

    MedlinePlus

    ... Contact Lenses Colored Contact Lenses Contact Lenses for Vision Correction Written by: Kierstan Boyd Reviewed by: Brenda ... on the surface of the eye. They correct vision like eyeglasses do and are safe when used ...

  1. Contact Interface Verification for DYNA3D Scenario 1: Basic Contact

    SciTech Connect

    McMichael, L D

    2006-05-10

    A suite of test problems has been developed to examine contact behavior within the nonlinear, three-dimensional, explicit finite element analysis (FEA) code DYNA3D (Lin, 2005). The test problems address the basic functionality of the contact algorithms, including the behavior of various kinematic, penalty, and Lagrangian enforcement formulations. The results from the DYNA3D analyses are compared to closed form solutions to verify the contact behavior. This work was performed as part of the Verification and Validation efforts of LLNL W Program within the NNSA's Advanced Simulation and Computing (ASC) Program. DYNA3D models the transient dynamic response of solids and structures including the interactions between disjoint bodies (parts). A wide variety of contact surfaces are available to represent the diverse interactions possible during an analysis, including relative motion (sliding), separation and gap closure (voids), and fixed relative position (tied). The problem geometry may be defined using a combination of element formulations, including one-dimensional beam and truss elements, two-dimensional shell elements, and three-dimensional solid elements. Consequently, it is necessary to consider various element interactions for each contact algorithm being verified. Most of the contact algorithms currently available in DYNA3D are examined; the exceptions are the Type 4--Single Surface Contact and Type 11--SAND algorithms. It is likely that these algorithms will be removed since their functionality is embodied in other, more robust, contact algorithms. The automatic contact algorithm is evaluated using the Type 12 interface. Two other variations of automatic contact, Type 13 and Type 14, offer additional means to adapt the interface domain, but share the same search and restoration algorithms as Type 12. The contact algorithms are summarized in Table 1. This report and associated test problems examine the scenario where one contact surface exists between two

  2. Shoe allergic contact dermatitis.

    PubMed

    Matthys, Erin; Zahir, Amir; Ehrlich, Alison

    2014-01-01

    Foot dermatitis is a widespread condition, affecting men and women of all ages. Because of the location, this condition may present as a debilitating problem to those who have it. Allergic contact dermatitis involving the feet is frequently due to shoes or socks. The allergens that cause shoe dermatitis can be found in any constituent of footwear, including rubber, adhesives, leather, dyes, metals, and medicaments. The goal of treatment is to identify and minimize contact with the offending allergen(s). The lack of product information released from shoe manufacturers and the continually changing trends in footwear present a challenge in treating this condition. The aim of this study is to review the current literature on allergic contact shoe dermatitis; clinical presentation, allergens, patch testing, and management will be discussed. PubMed and MEDLINE databases were used for the search, with a focus on literature updates from the last 15 years.

  3. Acrylate Systemic Contact Dermatitis.

    PubMed

    Sauder, Maxwell B; Pratt, Melanie D

    2015-01-01

    Acrylates, the 2012 American Contact Dermatitis Society allergen of the year, are found in a range of products including the absorbent materials within feminine hygiene pads. When fully polymerized, acrylates are nonimmunogenic; however, if not completely cured, the monomers can be potent allergens.A 28-year-old woman is presented, who had her teeth varnished with Isodan (Septodont, Saint-Maur-des-Fossés, France) containing HEMA (2-hydroxyethyl methacrylate) with no initial reaction. Approximately 1 month later, the patient developed a genital dermatitis secondary to her feminine hygiene pads. The initial reaction resolved, but 5 months later, the patient developed a systemic contact dermatitis after receiving a second varnishing.The patient was dramatically patch test positive to many acrylates. This case demonstrates a reaction to likely unpolymerized acrylates within a feminine hygiene pad, as well as broad cross-reactivity or cosensitivity to acrylates, and possibly a systemic contact dermatitis with systemic re-exposure to unpolymerized acrylates.

  4. Ring magnet firing angle control

    DOEpatents

    Knott, M.J.; Lewis, L.G.; Rabe, H.H.

    1975-10-21

    A device is provided for controlling the firing angles of thyratrons (rectifiers) in a ring magnet power supply. A phase lock loop develops a smooth ac signal of frequency equal to and in phase with the frequency of the voltage wave developed by the main generator of the power supply. A counter that counts from zero to a particular number each cycle of the main generator voltage wave is synchronized with the smooth AC signal of the phase lock loop. Gates compare the number in the counter with predetermined desired firing angles for each thyratron and with coincidence the proper thyratron is fired at the predetermined firing angle.

  5. Colloid retention at the meniscus-wall contact line in an open microchannel.

    PubMed

    Zevi, Yuniati; Gao, Bin; Zhang, Wei; Morales, Verónica L; Cakmak, M Ekrem; Medrano, Evelyn A; Sang, Wenjing; Steenhuis, Tammo S

    2012-02-01

    Colloid retention mechanisms in partially saturated porous media are currently being researched with an array of visualization techniques. These visualization techniques have refined our understanding of colloid movement and retention at the pore scale beyond what can be obtained from breakthrough experiments. One of the remaining questions is what mechanisms are responsible for colloid immobilization at the triple point where air, water, and soil grain meet. The objective of this study was to investigate how colloids are transported to the air-water-solid (AWS) contact line in an open triangular microchannel, and then retained as a function of meniscus contact angle with the wall and solution ionic strength. Colloid flow path, meniscus shape and meniscus-wall contact angle, and colloid retention at the AWS contact line were visualized and quantified with a confocal microscope. Experimental results demonstrated that colloid retention at the AWS contact line was significant when the meniscus-wall contact angle was less than 16°, but was minimal for the meniscus-wall contact angles exceeding 20°. Tracking of individual colloids and computational hydrodynamic simulation both revealed that for small contact angles (e.g., 12.5°), counter flow and flow vortices formed near the AWS contact line, but not for large contact angles (e.g., 28°). This counter flow helped deliver the colloids to the wall surface just below the contact line. In accordance with DLVO and hydrodynamic torque calculations, colloid movement may be stopped when the colloid reached the secondary minimum at the wall near the contact line. However, contradictory to the prediction of the torque analysis, colloid retention at the AWS contact line decreased with increasing ionic strength for contact angles of 10-20°, indicating that the air-water interface was involved through both counter flow and capillary force. We hypothesized that capillary force pushed the colloid through the primary energy

  6. Contact Modelling of Large Radius Air Bending with Geometrically Exact Contact Algorithm

    NASA Astrophysics Data System (ADS)

    Vorkov, V.; Konyukhov, A.; Vandepitte, D.; Duflou, J. R.

    2016-08-01

    Usage of high-strength steels in conventional air bending is restricted due to limited bendability of these metals. Large-radius punches provide a typical approach for decreasing deformations during the bending process. However, as deflection progresses the loading scheme changes gradually. Therefore, modelling of the contact interaction is essential for an accurate description of the loading scheme. In the current contribution, the authors implemented a plane frictional contact element based on the penalty method. The geometrically exact contact algorithm is used for the penetration determination. The implementation is done using the OOFEM - open source finite element solver. In order to verify the simulation results, experiments have been conducted on a bending press brake for 4 mm Weldox 1300 with a punch radius of 30 mm and a die opening of 80 mm. The maximum error for the springback calculation is 0.87° for the bending angle of 144°. The contact interaction is a crucial part of large radius bending simulation and the implementation leads to a reliable solution for the springback angle.

  7. Three-phase contact line and line tension of electrolyte solutions in contact with charged substrates

    NASA Astrophysics Data System (ADS)

    Ibagon, Ingrid; Bier, Markus; Dietrich, S.

    2016-06-01

    The three-phase contact line formed by the intersection of a liquid–vapor interface of an electrolyte solution with a charged planar substrate is studied in terms of classical density functional theory applied to a lattice model. The influence of the substrate charge density and of the ionic strength of the solution on the intrinsic structure of the three-phase contact line and on the corresponding line tension is analyzed. We find a negative line tension for all values of the surface charge density and of the ionic strength considered. The strength of the line tension decreases upon decreasing the contact angle via varying either the temperature or the substrate charge density.

  8. Two Comments on Bond Angles

    NASA Astrophysics Data System (ADS)

    Glaister, P.

    1997-09-01

    Tetrahedral Bond Angle from Elementary Trigonometry The alternative approach of using the scalar (or dot) product of vectors enables the determination of the bond angle in a tetrahedral molecule in a simple way. There is, of course, an even more straightforward derivation suitable for students who are unfamiliar with vectors, or products thereof, but who do know some elementary trigonometry. The starting point is the figure showing triangle OAB. The point O is the center of a cube, and A and B are at opposite corners of a face of that cube in which fits a regular tetrahedron. The required bond angle alpha = AÔB; and using Pythagoras' theorem, AB = 2(square root 2) is the diagonal of a face of the cube. Hence from right-angled triangle OEB, tan(alpha/2) = (square root 2) and therefore alpha = 2tan-1(square root 2) is approx. 109° 28' (see Fig. 1).

  9. Spinning angle optical calibration apparatus

    SciTech Connect

    Beer, S.K.; Pratt, H.R.

    1991-02-26

    This patent describes an optical calibration apparatus provided for calibrating and reproducing spinning angles in cross-polarization, nuclear magnetic resonance spectroscopy. An illuminated magnifying apparatus enables optical setting an accurate reproducing of spinning magic angles in cross-polarization, nuclear magnetic resonance spectroscopy experiments. A reference mark scribed on an edge of a spinning angle test sample holder is illuminated by a light source and viewed through a magnifying scope. When the magic angle of a sample material used as a standard is attained by varying the angular position of the sample holder, the coordinate position of the reference mark relative to a graduation or graduations on a reticle in the magnifying scope is noted.

  10. Relativistic Transformation of Solid Angle.

    ERIC Educational Resources Information Center

    McKinley, John M.

    1980-01-01

    Rederives the relativistic transformations of light intensity from compact sources (stars) to show where and how the transformation of a solid angle contributes. Discusses astrophysical and other applications of the transformations. (Author/CS)

  11. In Vivo Measurement of Glenohumeral Joint Contact Patterns

    NASA Astrophysics Data System (ADS)

    Bey, Michael J.; Kline, Stephanie K.; Zauel, Roger; Kolowich, Patricia A.; Lock, Terrence R.

    2009-12-01

    The objectives of this study were to describe a technique for measuring in-vivo glenohumeral joint contact patterns during dynamic activities and to demonstrate application of this technique. The experimental technique calculated joint contact patterns by combining CT-based 3D bone models with joint motion data that were accurately measured from biplane x-ray images. Joint contact patterns were calculated for the repaired and contralateral shoulders of 20 patients who had undergone rotator cuff repair. Significant differences in joint contact patterns were detected due to abduction angle and shoulder condition (i.e., repaired versus contralateral). Abduction angle had a significant effect on the superior/inferior contact center position, with the average joint contact center of the repaired shoulder 12.1% higher on the glenoid than the contralateral shoulder. This technique provides clinically relevant information by calculating in-vivo joint contact patterns during dynamic conditions and overcomes many limitations associated with conventional techniques for quantifying joint mechanics.

  12. Have Confidence in Contact

    ERIC Educational Resources Information Center

    Crisp, Richard J.; Turner, Rhiannon N.

    2010-01-01

    In an article in the May-June 2009 "American Psychologist," we discussed a new approach to reducing prejudice and encouraging more positive intergroup relations (Crisp & Turner, 2009). We named the approach imagined intergroup contact and defined it as "the mental simulation of a social interaction with a member or members of an outgroup category"…

  13. The Language Contact Profile

    ERIC Educational Resources Information Center

    Freed, Barbara F.; Dewey, Dan P.; Segalowitz, Norman; Halter, Randall

    2004-01-01

    Efforts to gather data of various sorts--demographics, language-learning history, contact with native speakers, use of the language in the field--as they relate to participants in SLA research studies are inherent to understanding more about language acquisition and use. Scholars frequently develop questionnaires of their own, which are rarely…

  14. Thermal Contact Conductance

    NASA Technical Reports Server (NTRS)

    Salerno, Louis J.; Kittel, Peter

    1997-01-01

    The performance of cryogenic instruments is often a function of their operating temperature. Thus, designers of cryogenic instruments often are required to predict the operating temperature of each instrument they design. This requires accurate thermal models of cryogenic components which include the properties of the materials and assembly techniques used. When components are bolted or otherwise pressed together, a knowledge of the thermal performance of such joints are also needed. In some cases, the temperature drop across these joints represents a significant fraction of the total temperature difference between the instrument and its cooler. While extensive databases exist on the thermal properties of bulk materials, similar databases for pressed contacts do not. This has often lead to instrument designs that avoid pressed contacts or to the over-design of such joints at unnecessary expense. Although many people have made measurements of contact conductances at cryogenic temperatures, this data is often very narrow in scope and even more often it has not been published in an easily retrievable fashion, if published at all. This paper presents a summary of the limited pressed contact data available in the literature.

  15. [Contact allergies in musicians].

    PubMed

    Gasenzer, E R; Neugebauer, E A M

    2012-12-01

    During the last years, the problem of allergic diseases has increased. Allergies are errant immune responses to a normally harmless substance. In musicians the allergic contact dermatitis to exotic woods is a special problem. Exotic rosewood contains new flavonoids, which trigger an allergic reaction after permanent contact with the instrument. High quality woodwind instruments such as baroque flute or clarinets are made in ebony or palisander because of its great sound. Today instruments for non-professional players are also made in these exotic materials and non-professionals may have the risk to develop contact dermatitis, too. Brass-player has the risk of an allergic reaction to the different metals contained in the metal sheets of modern flutes and brass instruments. Specially nickel and brass alloys are used to product flute tubes or brass instruments. Special problem arises in children: patients who are allergic to plants or foods have a high risk to develop contact dermatitis. Parents don't know the materials of low-priced instruments for beginners. Often unknown cheap woods from exotic areas are used. Low-priced brass instruments contain high amount of brass and other cheap metals. Physicians should advice musician-patients or parents about the risks of the different materials and look for the reason of eczema on mouth, face, or hands. PMID:23233303

  16. Contact sensitivity to proflavine.

    PubMed

    Goh, C L

    1986-09-01

    Proflavine lotion is a commonly used topical antiseptic in the tropics, but its sensitizing potential was never emphasized and many who developed allergic contact dermatitis were never aware of it. In a study of 45 patients, most presented with acute or subacute dermatitis which started on the arms and legs. Concomitant cutaneous sensitivity to other medicaments and lanolin occurred in 66% of the patients.

  17. [Current contact allergens].

    PubMed

    Geier, J; Uter, W; Lessmann, H; Schnuch, A

    2011-10-01

    Ever-changing exposure to contact allergens, partly due to statutory directives (e.g. nickel, chromate, methyldibromo glutaronitrile) or recommendations from industrial associations (e.g. hydroxyisohexyl 3-cyclohexene carboxaldehyde), requires on-going epidemiologic surveillance of contact allergy. In this paper, the current state with special focus in fragrances and preservatives is described on the basis of data of the Information Network of Departments of Dermatology (IVDK) of the year 2010. In 2010, 12,574 patients were patch tested in the dermatology departments belonging to the IVDK. Nickel is still the most frequent contact allergen. However the continuously improved EU nickel directive already has some beneficial effect; sensitization frequency in young women is dropping. In Germany, chromate-reduced cement has been in use now for several years, leading to a decline in chromate sensitization in brick-layers. Two fragrance mixes are part of the German baseline series; they are still relevant. The most important fragrances in these mixes still are oak moss absolute and hydroxyisohexyl 3-cyclohexene carboxaldehyde. However, in relation to these leading allergens, sensitization frequency to other fragrances contained in the mixes seems to be increasing. Among the preservatives, MCI/MI has not lost its importance as contact allergen, in contrast to MDBGN. Sources of MCI/MI sensitization obviously are increasingly found in occupational context. Methylisothiazolinone is a significant allergen in occupational settings, and less frequently in body care products.

  18. Contact Efflorescence on Demand

    NASA Astrophysics Data System (ADS)

    Davis, R. D.; Lance, S.; Gordon, J. A.; Ushijima, S.; Tolbert, M. A.

    2014-12-01

    The phase state of atmospheric aerosols (liquid vs solid) plays an important role in particle growth, cloud formation, climate impact and visibility degradation. In the atmosphere, changes in relative humidity (RH) and temperature cause phase transitions in the atmospheric particulate. Efflorescence, the process of salt crystal nucleation from an aqueous electrolyte solution upon decreasing RH, often occurs at a lower RH than the reverse process of deliquescence. It has been shown that the efflorescence RH can occur at a higher RH in the presence of a heterogeneous surface immersed in a liquid particle. Here we present a new laboratory technique using optically levitated particles to study heterogeneous efflorescence initiated by contact with an external particle. In this work, collisions between aqueous microdroplets and heterogeneous nuclei are monitored in situ using scattered laser light to quantify the number of collisions and to detect phase transitions. We find that when contact initiates the phase transition, efflorescence occurs at a higher RH than when the same heterogeneous nucleus is immersed in the particle. The results of these experiments will be discussed in the context of understanding contact nucleation on a mechanistic level and predicting the relative importance of contact efflorescence in the atmosphere.

  19. Multigrid contact detection method

    NASA Astrophysics Data System (ADS)

    He, Kejing; Dong, Shoubin; Zhou, Zhaoyao

    2007-03-01

    Contact detection is a general problem of many physical simulations. This work presents a O(N) multigrid method for general contact detection problems (MGCD). The multigrid idea is integrated with contact detection problems. Both the time complexity and memory consumption of the MGCD are O(N) . Unlike other methods, whose efficiencies are influenced strongly by the object size distribution, the performance of MGCD is insensitive to the object size distribution. We compare the MGCD with the no binary search (NBS) method and the multilevel boxing method in three dimensions for both time complexity and memory consumption. For objects with similar size, the MGCD is as good as the NBS method, both of which outperform the multilevel boxing method regarding memory consumption. For objects with diverse size, the MGCD outperform both the NBS method and the multilevel boxing method. We use the MGCD to solve the contact detection problem for a granular simulation system based on the discrete element method. From this granular simulation, we get the density property of monosize packing and binary packing with size ratio equal to 10. The packing density for monosize particles is 0.636. For binary packing with size ratio equal to 10, when the number of small particles is 300 times as the number of big particles, the maximal packing density 0.824 is achieved.

  20. Compact contacting device

    NASA Technical Reports Server (NTRS)

    Acharya, Arun (Inventor); Gottzmann, Christian F. (Inventor); Lockett, Michael J. (Inventor); Schneider, James S. (Inventor); Victor, Richard A. (Inventor); Zawierucha, Robert (Inventor)

    1994-01-01

    An apparatus comprising a rotatable mass of structured packing for mass or heat transfer between two contacting fluids of different densities wherein the packing mass is made up of corrugated sheets of involute shape relative to the axis of the packing mass and form a logarithmic spiral curved counter to the direction of rotation.

  1. [Contact allergies in musicians].

    PubMed

    Gasenzer, E R; Neugebauer, E A M

    2012-12-01

    During the last years, the problem of allergic diseases has increased. Allergies are errant immune responses to a normally harmless substance. In musicians the allergic contact dermatitis to exotic woods is a special problem. Exotic rosewood contains new flavonoids, which trigger an allergic reaction after permanent contact with the instrument. High quality woodwind instruments such as baroque flute or clarinets are made in ebony or palisander because of its great sound. Today instruments for non-professional players are also made in these exotic materials and non-professionals may have the risk to develop contact dermatitis, too. Brass-player has the risk of an allergic reaction to the different metals contained in the metal sheets of modern flutes and brass instruments. Specially nickel and brass alloys are used to product flute tubes or brass instruments. Special problem arises in children: patients who are allergic to plants or foods have a high risk to develop contact dermatitis. Parents don't know the materials of low-priced instruments for beginners. Often unknown cheap woods from exotic areas are used. Low-priced brass instruments contain high amount of brass and other cheap metals. Physicians should advice musician-patients or parents about the risks of the different materials and look for the reason of eczema on mouth, face, or hands.

  2. Contact: Releasing the news

    NASA Astrophysics Data System (ADS)

    Pinotti, Roberto

    The problem of mass behavior after man's future contacts with other intelligences in the universe is not only a challenge for social scientists and political leaders all over the world, but also a cultural time bomb as well. In fact, since the impact of CETI (Contact with Extraterrestrial Intelligence) on human civilization, with its different cultures, might cause a serious socio-anthropological shock, a common and predetermined worldwide strategy is necessary in releasing the news after the contact, in order to keep possible manifestations of fear, panic and hysteria under control. An analysis of past studies in this field and of parallel historical situations as analogs suggests a definite "authority crisis" in the public as a direct consequence of an unexpected release of the news, involving a devastating "chain reaction" process (from both the psychological and sociological viewpoints) of anomie and maybe the collapse of today's society. The only way to prevent all this is to prepare the world's public opinion concerning contact before releasing the news, and to develop a long-term strategy through the combined efforts of scientists, political leaders, intelligence agencies and the mass media, in order to create the cultural conditions in which a confrontation with ETI won't affect mankind in a traumatic way. Definite roles and tasks in this multi-level model are suggested.

  3. Microparticle assembly and contact line dynamics

    NASA Astrophysics Data System (ADS)

    Ghosh, Moniraj

    This thesis addresses three topics. First, microparticle assembly on solid surfaces from an evaporative suspension is studied. It is well known that microparticles collect near three phase contact lines owing to evaporative fluxes. In a dip coating configuration, if the evaporative flux and plate withdrawal velocity U are matched, large colloidal crystals form. Here, I investigate the consequences of varying the plate withdrawal rate, and find that periodic striped patterns emerge which depend strongly on U. The stripes form when three phase contact lines "jump", or recede rapidly, upon detaching from well-wet particle aggregates on less wet substrates. Stripe width, spacing and height change abruptly at a transition velocity which can be related to a Landau-Levich transition in the flow. The second part of my thesis is a numerical simulation of drop spreading and retraction as a function of drop scale. The drop moves over a thin liquid film, and drop motion is initiated by an impulsive change in surface wettability. Owing to the presence of the film, these simulations require no closure condition at the 'apparent' contact line. Rather, relationships emerge between the contact line velocity and the dynamic contact angle. For nanoscopic drops, molecular effects dominate the drop motion. For drops an order of magnitude larger than the thin film, regimes emerge in which drops move according to Tanner's law, a relationship derived for macroscopic drops. Drop retraction is considerably more rapid than spreading owing to rapid dewetting events near the contact line. This thesis concludes with a discussion of a technique for creating multifunctional surfaces presenting discrete patches of several proteins. The technique relies on microcontact printing (microCP) to define active regions, and the use of a microfluidics device to deliver proteins to those regions. The surfaces are used to capture cells from a suspension, to sort cells from a mixed suspension, and to study

  4. An oilspill trajectory analysis model with a variable wind deflection angle

    USGS Publications Warehouse

    Samuels, W.B.; Huang, N.E.; Amstutz, D.E.

    1982-01-01

    The oilspill trajectory movement algorithm consists of a vector sum of the surface drift component due to wind and the surface current component. In the U.S. Geological Survey oilspill trajectory analysis model, the surface drift component is assumed to be 3.5% of the wind speed and is rotated 20 degrees clockwise to account for Coriolis effects in the Northern Hemisphere. Field and laboratory data suggest, however, that the deflection angle of the surface drift current can be highly variable. An empirical formula, based on field observations and theoretical arguments relating wind speed to deflection angle, was used to calculate a new deflection angle at each time step in the model. Comparisons of oilspill contact probabilities to coastal areas calculated for constant and variable deflection angles showed that the model is insensitive to this changing angle at low wind speeds. At high wind speeds, some statistically significant differences in contact probabilities did appear. ?? 1982.

  5. 76 FR 31945 - Advanced Scientific Computing Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-02

    ... Advanced Scientific Computing Advisory Committee AGENCY: Department of Energy, Office of Science. ACTION... the Advanced Scientific Computing Advisory Committee (ASCAC). The Federal Advisory Committee Act (Pub... INFORMATION CONTACT: Melea Baker, Office of Advanced Scientific Computing Research; SC-21/Germantown...

  6. Direct-contact heat exchanger

    NASA Astrophysics Data System (ADS)

    Bricard, A.

    The working principle of direct contact heat exchanger, where heat transfer takes place between two immiscible fluids coming into direct contact, is described. Typical direct contact devices are outlined. A better understanding of the principles involved and the development of computational models for multiphase subsytems are concluded as stimulus for direct contact heat and mass transfer applications.

  7. Variable-angle high-angle annular dark-field imaging: application to three-dimensional dopant atom profiling.

    PubMed

    Zhang, Jack Y; Hwang, Jinwoo; Isaac, Brandon J; Stemmer, Susanne

    2015-07-24

    Variable-angle high-angle annular dark-field (HAADF) imaging in scanning transmission electron microscopy is developed for precise and accurate determination of three-dimensional (3D) dopant atom configurations. Gd-doped SrTiO3 films containing Sr columns containing zero, one, or two Gd dopant atoms are imaged in HAADF mode using two different collection angles. Variable-angle HAADF significantly increases both the precision and accuracy of 3D dopant profiling. Using image simulations, it is shown that the combined information from the two detectors reduces the uncertainty in the dopant depth position measurement and can uniquely identify certain atomic configurations that are indistinguishable with a single detector setting. Additional advances and applications are discussed.

  8. Variable-angle high-angle annular dark-field imaging: application to three-dimensional dopant atom profiling

    PubMed Central

    Zhang, Jack Y.; Hwang, Jinwoo; Isaac, Brandon J.; Stemmer, Susanne

    2015-01-01

    Variable-angle high-angle annular dark-field (HAADF) imaging in scanning transmission electron microscopy is developed for precise and accurate determination of three-dimensional (3D) dopant atom configurations. Gd-doped SrTiO3 films containing Sr columns containing zero, one, or two Gd dopant atoms are imaged in HAADF mode using two different collection angles. Variable-angle HAADF significantly increases both the precision and accuracy of 3D dopant profiling. Using image simulations, it is shown that the combined information from the two detectors reduces the uncertainty in the dopant depth position measurement and can uniquely identify certain atomic configurations that are indistinguishable with a single detector setting. Additional advances and applications are discussed. PMID:26206489

  9. Orientation angle and the adhesion of single gecko setae.

    PubMed

    Hill, Ginel C; Soto, Daniel R; Peattie, Anne M; Full, Robert J; Kenny, T W

    2011-07-01

    We investigated the effects of orientation angle on the adhesion of single gecko setae using dual-axis microelectromechanical systems force sensors to simultaneously detect normal and shear force components. Adhesion was highly sensitive to the pitch angle between the substrate and the seta's stalk. Maximum lateral adhesive force was observed with the stalk parallel to the substrate, and adhesion decreased smoothly with increasing pitch. The roll orientation angle only needed to be roughly correct with the spatular tuft of the seta oriented grossly towards the substrate for high adhesion. Also, detailed measurements were made to control for the effect of normal preload forces. Higher normal preload forces caused modest enhancement of the observed lateral adhesive force, provided that adequate contact was made between the seta and the substrate. These results should be useful in the design and manufacture of gecko-inspired synthetic adhesives with anisotropic properties, an area of substantial recent research efforts.

  10. Orientation angle and the adhesion of single gecko setae

    PubMed Central

    Hill, Ginel C.; Soto, Daniel R.; Peattie, Anne M.; Full, Robert J.; Kenny, T. W.

    2011-01-01

    We investigated the effects of orientation angle on the adhesion of single gecko setae using dual-axis microelectromechanical systems force sensors to simultaneously detect normal and shear force components. Adhesion was highly sensitive to the pitch angle between the substrate and the seta's stalk. Maximum lateral adhesive force was observed with the stalk parallel to the substrate, and adhesion decreased smoothly with increasing pitch. The roll orientation angle only needed to be roughly correct with the spatular tuft of the seta oriented grossly towards the substrate for high adhesion. Also, detailed measurements were made to control for the effect of normal preload forces. Higher normal preload forces caused modest enhancement of the observed lateral adhesive force, provided that adequate contact was made between the seta and the substrate. These results should be useful in the design and manufacture of gecko-inspired synthetic adhesives with anisotropic properties, an area of substantial recent research efforts. PMID:21288955

  11. The Semiotic and Conceptual Genesis of Angle

    ERIC Educational Resources Information Center

    Tanguay, Denis; Venant, Fabienne

    2016-01-01

    In the present study, we try to understand how students at the end of primary school conceive of angle: Is an angle a magnitude for them or a geometric figure, and how do they manage to coordinate the two aspects in their understanding of the concepts of angle and of angle measurement? With the aim of better grasping the way "angle" is…

  12. Contact Graph Routing

    NASA Technical Reports Server (NTRS)

    Burleigh, Scott C.

    2011-01-01

    Contact Graph Routing (CGR) is a dynamic routing system that computes routes through a time-varying topology of scheduled communication contacts in a network based on the DTN (Delay-Tolerant Networking) architecture. It is designed to enable dynamic selection of data transmission routes in a space network based on DTN. This dynamic responsiveness in route computation should be significantly more effective and less expensive than static routing, increasing total data return while at the same time reducing mission operations cost and risk. The basic strategy of CGR is to take advantage of the fact that, since flight mission communication operations are planned in detail, the communication routes between any pair of bundle agents in a population of nodes that have all been informed of one another's plans can be inferred from those plans rather than discovered via dialogue (which is impractical over long one-way-light-time space links). Messages that convey this planning information are used to construct contact graphs (time-varying models of network connectivity) from which CGR automatically computes efficient routes for bundles. Automatic route selection increases the flexibility and resilience of the space network, simplifying cross-support and reducing mission management costs. Note that there are no routing tables in Contact Graph Routing. The best route for a bundle destined for a given node may routinely be different from the best route for a different bundle destined for the same node, depending on bundle priority, bundle expiration time, and changes in the current lengths of transmission queues for neighboring nodes; routes must be computed individually for each bundle, from the Bundle Protocol agent's current network connectivity model for the bundle s destination node (the contact graph). Clearly this places a premium on optimizing the implementation of the route computation algorithm. The scalability of CGR to very large networks remains a research topic

  13. [Contact dermatitis from Agave americana].

    PubMed

    de la Cueva, Pablo; González-Carrascosa, Mateo; Campos, Minia; Leis, Vicente; Suárez, Ricardo; Lázaro, Pablo

    2005-10-01

    Numerous plant species and their derivatives can cause skin reactions through a variety of mechanisms: irritative contact dermatitis, allergic contact dermatitis, contact urticaria and photodermatitis. We present a case of irritative contact dermatitis after exposure to the sap of Agave americana. The skin symptoms in this case have only been described on rare occasions; although this condition usually presents with a papulovesicular rash, in this patient it appeared as purpuric lesions in the contact area.

  14. Semiconductor ohmic contact

    NASA Technical Reports Server (NTRS)

    Hawrylo, Frank Zygmunt (Inventor); Kressel, Henry (Inventor)

    1977-01-01

    A semiconductor device has one surface of P type conductivity material having a wide energy bandgap and a large crystal lattice parameter. Applied to the P type surface of the semiconductor device is a degenerate region of semiconductor material, preferably a group III-V semiconductor material, having a narrower energy bandgap. The degenerate region is doped with tin to increase the crystal lattice of the region to more closely approximate the crystal lattice of the one surface of the semiconductor device. The degenerate region is compensatingly doped with a P type conductivity modifier. An electrical contact is applied to one surface of the degenerate region forming an ohmic contact with the semiconductor device.

  15. Contact dynamics math model

    NASA Technical Reports Server (NTRS)

    Glaese, John R.; Tobbe, Patrick A.

    1986-01-01

    The Space Station Mechanism Test Bed consists of a hydraulically driven, computer controlled six degree of freedom (DOF) motion system with which docking, berthing, and other mechanisms can be evaluated. Measured contact forces and moments are provided to the simulation host computer to enable representation of orbital contact dynamics. This report describes the development of a generalized math model which represents the relative motion between two rigid orbiting vehicles. The model allows motion in six DOF for each body, with no vehicle size limitation. The rotational and translational equations of motion are derived. The method used to transform the forces and moments from the sensor location to the vehicles' centers of mass is also explained. Two math models of docking mechanisms, a simple translational spring and the Remote Manipulator System end effector, are presented along with simulation results. The translational spring model is used in an attempt to verify the simulation with compensated hardware in the loop results.

  16. /Au Back Contacts

    NASA Astrophysics Data System (ADS)

    Paudel, Naba R.; Compaan, Alvin D.; Yan, Yanfa

    2014-08-01

    We report on the fabrication and characterization of CdTe thin-film solar cells with Cu-free MoO3- x /Au back contacts. CdTe solar cells with sputtered CdTe absorbers of thicknesses from 0.5 to 1.75 μm were fabricated on Pilkington SnO2:F/SnO2-coated soda-lime glasses coated with a 60- to 80-nm sputtered CdS layer. The MoO3- x /Au back contact layers were deposited by thermal evaporation. The incorporation of MoO3- x layer was found to improve the open circuit voltage ( V OC) but reduce the fill factor of the ultrathin CdTe cells. The V OC was found to increase as the CdTe thickness increased.

  17. [Contact allergy to cosmetics].

    PubMed

    Goossens, A; Merckx, L

    1997-12-01

    This article gives the results of contact allergic reactions to cosmetics seen between 1985 and 1990 (462 patients investigated) and between 1991 and 1996 (486 patients investigated). Perfume components remain the most frequently occurring allergens in cosmetics. They are followed by preservative agents, a class within which important shifts have occurred over time (e.g. as with the isothiazolinone mixture). Excipients and certainly emulsifiers (e.g. cocamidopropylbetaine) are potentially not only irritants but also allergens. Among the "active" or category-specific ingredients, oxidative hair dyes, based on paraphenylenediamine and derivatives, and nail care products, based on (meth)acrylates are particularly apt to cause professional dermatoses. Finally, the share of sunscreens as cosmetic allergens remains limited, which may well be because a contact or photocontactallergy is often not recognized since the differential diagnosis with a primary sun intolerance is not always obvious.

  18. Contact dermatitis from propolis.

    PubMed

    Wanscher, B

    1976-04-01

    Two patients with contact dermatitis due to the natural product propolis (bee glue) are reported. They presented perioral eczema and stomatitis which were recalcitrant until propolis was considered as the cause. Patch tests with propolis preparations were positive in both patients, and, furthermore, in the second patient the lesions relapsed after provocation tests. European standard patch test including balsam of Peru were negative. The complexity of propolis, its supposed anti-inflammatory effect due to flavonoids, and the sensitizing agents originating mainly from the poplar trees are discussed together with the cross-sensitization to balsam of Peru. Contact dermatitis due to propolis should be considered in unexplained eczemas, mainly perioral but also in other areas, as propolis preparations are available also as ointments and cosmetic creams.

  19. Contact dermatitis in children

    PubMed Central

    2010-01-01

    Contact dermatitis in pediatric population is a common but (previously) under recognized disease. It is usually divided into the allergic and the irritant forms. The diagnosis is usually obtained with the patch test technique after conducting a thorough medical history and careful physical examination but patch testing in infants may be particularly difficult, and false-positive reactions may occur. This study also provides an overview of the most common allergens in pediatric population and discusses various therapeutic modalities. PMID:20205907

  20. Contact dermatitis in children.

    PubMed

    Rademaker, M; Forsyth, A

    1989-02-01

    125 children under the age of 12 years were patch tested over a period of 7 years. 60 (48%) of the children had 1 or more positive (+ve) reactions, of which 92% (55/60) were considered relevant. The most common allergens were metals (35 + ves), fragrances (24 + ves) and rubber compounds (11 + ves). 40 of the children were also tested for contact urticaria against food additives and fragrances, of whom 20 were positive (benzoic acid 14, cinnamaldehyde 12).

  1. Contact stress sensor

    DOEpatents

    Kotovsky, Jack

    2012-02-07

    A contact stress sensor includes one or more MEMS fabricated sensor elements, where each sensor element of includes a thin non-recessed portion, a recessed portion and a pressure sensitive element adjacent to the recessed portion. An electric circuit is connected to the pressure sensitive element. The circuit includes a thermal compensator and a pressure signal circuit element configured to provide a signal upon movement of the pressure sensitive element.

  2. Contact stress sensor

    DOEpatents

    Kotovsky, Jack

    2014-02-11

    A method for producing a contact stress sensor that includes one or more MEMS fabricated sensor elements, where each sensor element of includes a thin non-recessed portion, a recessed portion and a pressure sensitive element adjacent to the recessed portion. An electric circuit is connected to the pressure sensitive element. The circuit includes a pressure signal circuit element configured to provide a signal upon movement of the pressure sensitive element.

  3. Functional modular contact lens

    NASA Astrophysics Data System (ADS)

    Shum, Angela J.; Cowan, Melissa; Lähdesmäki, Ilkka; Lingley, Andrew; Otis, Brian; Parviz, Babak A.

    2009-08-01

    Tear fluid offers a potential route for non-invasive sensing of physiological parameters. Utilization of this potential depends on the ability to manufacture sensors that can be placed on the surface of the eye. A contact lens makes a natural platform for such sensors, but contact lens polymers present a challenge for sensor fabrication. This paper describes a microfabrication process for constructing sensors that can be integrated into the structure of a functional contact lens in the future. To demonstrate the capabilities of the process, an amperometric glucose sensor was fabricated on a polymer substrate. The sensor consists of platinum working and counter electrodes, as well as a region of indium-tin oxide (ITO) for glucose oxidase immobilization. An external silver-silver chloride electrode was used as the reference electrode during the characterization experiments. Sensor operation was validated by hydrogen peroxide measurements in the 10- 20 μM range and glucose measurements in the 0.125-20 mM range.

  4. PREDITOR: a web server for predicting protein torsion angle restraints

    PubMed Central

    Berjanskii, Mark V.; Neal, Stephen; Wishart, David S.

    2006-01-01

    Every year between 500 and 1000 peptide and protein structures are determined by NMR and deposited into the Protein Data Bank. However, the process of NMR structure determination continues to be a manually intensive and time-consuming task. One of the most tedious and error-prone aspects of this process involves the determination of torsion angle restraints including phi, psi, omega and chi angles. Most methods require many days of additional experiments, painstaking measurements or complex calculations. Here we wish to describe a web server, called PREDITOR, which greatly accelerates and simplifies this task. PREDITOR accepts sequence and/or chemical shift data as input and generates torsion angle predictions (with predicted errors) for phi, psi, omega and chi-1 angles. PREDITOR combines sequence alignment methods with advanced chemical shift analysis techniques to generate its torsion angle predictions. The method is fast (<40 s per protein) and accurate, with 88% of phi/psi predictions being within 30° of the correct values, 84% of chi-1 predictions being correct and 99.97% of omega angles being correct. PREDITOR is 35 times faster and up to 20% more accurate than any existing method. PREDITOR also provides accurate assessments of the torsion angle errors so that the torsion angle constraints can be readily fed into standard structure refinement programs, such as CNS, XPLOR, AMBER and CYANA. Other unique features to PREDITOR include dihedral angle prediction via PDB structure mapping, automated chemical shift re-referencing (to improve accuracy), prediction of proline cis/trans states and a simple user interface. The PREDITOR website is located at: . PMID:16845087

  5. Metrology of angles in astronomy

    NASA Astrophysics Data System (ADS)

    Kovalevsky, Jean

    2004-10-01

    In astronomy, measurements of angles play a major role. After defining the units in use in astronomy, three methods of measuring angles are presented, with an application to the transit instrument. The interferometric techniques for measuring large angles are described in optical and radio wavelengths. Due to the atmospheric and mechanical limitation on ground, space astrometry has multiple advantages. The satellite Hipparcos is described and the data reduction procedures and results obtained are sketched. In the future, two new astrometric space missions are approved: GAIA, based on Hipparcos principles and SIM, a space interferometer. They are described and the expected accuracies are presented. To cite this article: J. Kovalevsky, C. R. Physique 5 (2004).

  6. Dual contact pogo pin assembly

    DOEpatents

    Hatch, Stephen McGarry

    2015-01-20

    A contact assembly includes a base and a pair of electrical contacts supported by the base. A first end of the first electrical contact corresponds to a first end of the base and is configured to engage a first external conductive circuit element. A first end of the second electrical contact also corresponds to the first end of the base and is configured to engage a second external conductive circuit element. The first contact and the second contact are electrically isolated from one another and configured to compress when engaging an external connector element. The base includes an aperture positioned on a second end of the base outboard of a second end of the first and second electrical contacts. The aperture presents a narrowing shape with a wide mouth distal the electrical contacts and a narrow internal through-hole proximate the electrical contacts.

  7. Dual contact pogo pin assembly

    DOEpatents

    Hatch, Stephen McGarry

    2016-06-21

    A contact assembly includes a base and a pair of electrical contacts supported by the base. A first end of the first electrical contact corresponds to a first end of the base and is configured to engage a first external conductive circuit element. A first end of the second electrical contact also corresponds to the first end of the base and is configured to engage a second external conductive circuit element. The first contact and the second contact are electrically isolated from one another and configured to compress when engaging an external connector element. The base includes an aperture positioned on a second end of the base outboard of a second end of the first and second electrical contacts. The aperture presents a narrowing shape with a wide mouth distal the electrical contacts and a narrow internal through-hole proximate the electrical contacts.

  8. Compression failure of angle-ply laminates

    NASA Technical Reports Server (NTRS)

    Peel, L. D.; Hyer, M. W.; Shuart, M. J.

    1992-01-01

    Test results from the compression loading of (+ or - Theta/ - or + Theta)(sub 6s) angle-ply IM7-8551-7a specimens, 0 less than or = Theta less than or = 90 degs, are presented. The observed failure strengths and modes are discussed, and typical stress-strain relations shown. Using classical lamination theory and the maximum stress criterion, an attempt is made to predict failure stress as a function of Theta. This attempt results in poor correlation with test results and thus a more advanced model is used. The model, which is based on a geometrically nonlinear theory, and which was taken from previous work, includes the influence of observed layer waviness. The waviness is described by the wave length and the wave amplitude. The theory is briefly described and results from the theory are correlated with test results. It is shown that by using levels of waviness observed in the specimens, the correlation between predictions and observations is good.

  9. Large angle magnetic suspension test fixture

    NASA Technical Reports Server (NTRS)

    Britcher, Colin P.

    1993-01-01

    Progress made under the subject grant in the period from 1 Nov. 1992 to 31 May 1993 is presented. The research involves the continued development of the Large Angle Magnetic Suspension Test Fixture (LAMSTF) and also the recommissioning of an additional piece of exisiting hardware. During the period in question, the initial configuration of LAMSTF was completed and made routinely and reliably operational. A digital phase advance controller was completed and documented. The goal of a controlled 360 deg rotation was achieved. Work started on the recommissioning of the Annular Suspension and Pointing System (ASPS). Work completed during the report period included: modeling; position sensing; controller; support of the Second International Symposium on Magnetic Suspension Technology; and recommissioning of the Annular Suspension and Pointing System.

  10. A superconducting large-angle magnetic suspension

    NASA Technical Reports Server (NTRS)

    Downer, James; Goldie, James; Torti, Richard

    1991-01-01

    The component technologies were developed required for an advanced control moment gyro (CMG) type of slewing actuator for large payloads. The key component of the CMG is a large-angle magnetic suspension (LAMS). The LAMS combines the functions of the gimbal structure, torque motors, and rotor bearings of a CMG. The LAMS uses a single superconducting source coil and an array of cryoresistive control coils to produce a specific output torque more than an order of magnitude greater than conventional devices. The designed and tested LAMS system is based around an available superconducting solenoid, an array of twelve room-temperature normal control coils, and a multi-input, multi-output control system. The control laws were demonstrated for stabilizing and controlling the LAMS system.

  11. From natural to biomimetic: The superhydrophobicity and the contact time.

    PubMed

    Liang, Yun-Hong; Peng, Jian; Li, Xiu-Juan; Xu, Jin-Kai; Zhang, Zhi-Hui; Ren, Lu-Quan

    2016-08-01

    The superhydrophobicities and the contact time of lotus leaf and reed leaf were investigated. The results indicated that both lotus leaf and reed leaf have good superhydrophobic properties, and the water contact time was 12.7 and 14.7 ms on the surface of lotus leaf and reed leaf, respectively. Surface structure plays a key role in the different contacting times. Homogeneous distribution of papillae on the surface of lotus leaf was more helpful to reduce the contact time than anisotropic groove-shape on the surface of reed leaf. Based on the bionics coupling theory, the bionics sample possessing similar lotus-leaf-like surface structure on the aluminum alloy was designed and fabricated successfully. The water contact angle was about 153 ± 2°, sliding angle less than 5°, and the water contact time was 13.4 ms on the surface of bionics sample, which presented excellent superhydrophobic property, and achieved the aim of bionic design. Microsc. Res. Tech. 79:712-720, 2016. © 2016 Wiley Periodicals, Inc. PMID:27252147

  12. From natural to biomimetic: The superhydrophobicity and the contact time.

    PubMed

    Liang, Yun-Hong; Peng, Jian; Li, Xiu-Juan; Xu, Jin-Kai; Zhang, Zhi-Hui; Ren, Lu-Quan

    2016-08-01

    The superhydrophobicities and the contact time of lotus leaf and reed leaf were investigated. The results indicated that both lotus leaf and reed leaf have good superhydrophobic properties, and the water contact time was 12.7 and 14.7 ms on the surface of lotus leaf and reed leaf, respectively. Surface structure plays a key role in the different contacting times. Homogeneous distribution of papillae on the surface of lotus leaf was more helpful to reduce the contact time than anisotropic groove-shape on the surface of reed leaf. Based on the bionics coupling theory, the bionics sample possessing similar lotus-leaf-like surface structure on the aluminum alloy was designed and fabricated successfully. The water contact angle was about 153 ± 2°, sliding angle less than 5°, and the water contact time was 13.4 ms on the surface of bionics sample, which presented excellent superhydrophobic property, and achieved the aim of bionic design. Microsc. Res. Tech. 79:712-720, 2016. © 2016 Wiley Periodicals, Inc.

  13. A robust algorithm for the contact of viscoelastic materials

    NASA Astrophysics Data System (ADS)

    Spinu, S.; Cerlinca, D.

    2016-08-01

    Existing solutions for the contact problem involving viscoelastic materials often require numerical differentiation and integration, as well as resolution of transcendental equations, which can raise convergence issues. The algorithm advanced in this paper can tackle the contact behaviour of the viscoelastic materials without any convergence problems, for arbitrary contact geometry, arbitrary loading programs and complex constitutive models of linear viscoelasticity. An updated algorithm for the elastic frictionless contact, coupled with a semi-analytical method for the computation of viscoelastic displacement, is employed to solve the viscoelastic contact problem at a series of small time increments. The number of equations in the linear system resulting from the geometrical condition of deformation is set by the number of cells in the contact area, which is a priori unknown. A trial-and-error approach is implemented, resulting in a series of linear systems which are solved on evolving contact areas, until static equilibrium equations and complementarity conditions are fully satisfied for every cell in the computational domain. At any iteration, cells with negative pressure are excluded from the contact area, while cells with negative gap (i.e. cells where the contacting bodies are predicted to overlap) are reincluded. The solution is found when pressure is stabilized in relation to the imposed normal load. This robust algorithm is expected to solve a large variety of contact problems involving viscoelastic materials.

  14. Method for producing angled optical fiber tips in the laboratory

    NASA Astrophysics Data System (ADS)

    Davenport, John J.; Hickey, Michelle; Phillips, Justin P.; Kyriacou, Panicos A.

    2016-02-01

    A simple laboratory method is presented for producing optical fibers with tips polished at various angles. Angled optical fiber tips are used in applications such as optical sensing and remote laser surgery, where they can be used to control the angle of light leaving the fiber or direct it to the side. This allows for greater control and allows areas to be reached that otherwise could not. Optical fibers were produced with tip angles of 45 deg using a Perspex mounting block with an aluminum base plate. The dispersion of light leaving the tip was tested using a blue (470 nm) LED. The angle imposed an angular shift on the light diffracting out of the tip of approximately 30 deg. Additionally, some light reflected from the tip surface to diffract at 90 deg through the side of the fiber. These observations are consistent with theory and those seen by other studies, validating the method. The method was simple to perform and does not require advanced manufacturing tools. The method is suitable for producing small quantities of angle-tipped optical fibers for research applications.

  15. Large angle measurement by interferometry

    NASA Astrophysics Data System (ADS)

    Apostol, Dan; Blanaru, Constantin; Damian, Victor S.; Logofatu, Petre-Catalin; Tumbar, R.; Dobroiu, Adrian

    1995-03-01

    An interferometric set-up able to measure angles as large as +180 degree(s) is presented. The principle of the method is to measure a linear displacement (translation) produced by a crank-gear mechanism which converts the angular movement of a rotating table. The optical scheme and consideration on the accuracy of the method are presented.

  16. Discovering the Inscribed Angle Theorem

    ERIC Educational Resources Information Center

    Roscoe, Matt B.

    2012-01-01

    Learning to play tennis is difficult. It takes practice, but it also helps to have a coach--someone who gives tips and pointers but allows the freedom to play the game on one's own. Learning to act like a mathematician is a similar process. Students report that the process of proving the inscribed angle theorem is challenging and, at times,…

  17. Contact dermatitis to methylisothiazolinone*

    PubMed Central

    Scherrer, Maria Antonieta Rios; Rocha, Vanessa Barreto; Andrade, Ana Regina Coelho

    2015-01-01

    Methylisothiazolinone (MI) is a preservative found in cosmetic and industrial products. Contact dermatitis caused by either methylchloroisothiazolinone/methylisothiazolinone (MCI/MI or Kathon CG) or MI has shown increasing frequency. The latter is preferably detected through epicutaneous testing with aqueous MI 2000 ppm, which is not included in the Brazilian standard tray. We describe a series of 23 patients tested using it and our standard tray. A case with negative reaction to MCI/MI and positive to MI is emphasized. PMID:26734880

  18. Adhesion in hydrogel contacts

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  19. Adhesive Contact Sweeper

    NASA Technical Reports Server (NTRS)

    Patterson, Jonathan D.

    1993-01-01

    Adhesive contact sweeper removes hair and particles vacuum cleaner leaves behind, without stirring up dust. Also cleans loose rugs. Sweeper holds commercially available spools of inverted adhesive tape. Suitable for use in environments in which air kept free of dust; optics laboratories, computer rooms, and areas inhabited by people allergic to dust. For carpets, best used in tandem with vacuum cleaner; first pass with vacuum cleaner removes coarse particles, and second pass with sweeper extracts fine particles. This practice extends useful life of adhesive spools.

  20. Effect of surface modification on interfacial nanobubble morphology and contact line tension.

    PubMed

    Rangharajan, Kaushik K; Kwak, Kwang J; Conlisk, A T; Wu, Yan; Prakash, Shaurya

    2015-07-14

    Past research has confirmed the existence of surface nanobubbles on various hydrophobic substrates (static contact angle >90°) when imaged in air-equilibrated water. Additionally, the use of solvent exchange techniques (based on the difference in saturation levels of air in various solvents) also introduced surface nanobubbles on hydrophilic substrates (static contact angle <90°). In this work, tapping mode atomic force microscopy was used to image interfacial nanobubbles formed on bulk polycarbonate (static contact angle of 81.1°), bromo-terminated silica (BTS; static contact angle of 85.5°), and fluoro-terminated silica (FTS; static contact angle of 105.3°) surfaces when immersed in air-equilibrated water without solvent exchange. Nanobubbles formed on the above three substrates were characterized on the basis of Laplace pressure, bubble density, and contact line tension. Results reported here show that (1) the Laplace pressures of all nanobubbles formed on both BTS and polycarbonate were an order of magnitude higher than those of FTS, (2) the nanobubble number density per unit area decreased with an increase in substrate contact angle, and (3) the contact line tension of the nanobubbles was calculated to be positive for both BTS and polycarbonate (lateral radius, Rs < 50 nm for all nanobubbles), and negative for FTS (Rs > 50 nm for all nanobubbles). The nanobubble morphology and distribution before and after using the solvent exchange method (ethanol-water), on the bulk polycarbonate substrate was also characterized. Analysis for these polycarbonate surface nanobubbles showed that both the Laplace pressure and nanobubble density reduced by ≈98% after ethanol-water exchange, accompanied by a flip in the magnitude of contact line tension from positive (0.19 nN) to negative (-0.11 nN). PMID:26041331

  1. Effect of surface modification on interfacial nanobubble morphology and contact line tension.

    PubMed

    Rangharajan, Kaushik K; Kwak, Kwang J; Conlisk, A T; Wu, Yan; Prakash, Shaurya

    2015-07-14

    Past research has confirmed the existence of surface nanobubbles on various hydrophobic substrates (static contact angle >90°) when imaged in air-equilibrated water. Additionally, the use of solvent exchange techniques (based on the difference in saturation levels of air in various solvents) also introduced surface nanobubbles on hydrophilic substrates (static contact angle <90°). In this work, tapping mode atomic force microscopy was used to image interfacial nanobubbles formed on bulk polycarbonate (static contact angle of 81.1°), bromo-terminated silica (BTS; static contact angle of 85.5°), and fluoro-terminated silica (FTS; static contact angle of 105.3°) surfaces when immersed in air-equilibrated water without solvent exchange. Nanobubbles formed on the above three substrates were characterized on the basis of Laplace pressure, bubble density, and contact line tension. Results reported here show that (1) the Laplace pressures of all nanobubbles formed on both BTS and polycarbonate were an order of magnitude higher than those of FTS, (2) the nanobubble number density per unit area decreased with an increase in substrate contact angle, and (3) the contact line tension of the nanobubbles was calculated to be positive for both BTS and polycarbonate (lateral radius, Rs < 50 nm for all nanobubbles), and negative for FTS (Rs > 50 nm for all nanobubbles). The nanobubble morphology and distribution before and after using the solvent exchange method (ethanol-water), on the bulk polycarbonate substrate was also characterized. Analysis for these polycarbonate surface nanobubbles showed that both the Laplace pressure and nanobubble density reduced by ≈98% after ethanol-water exchange, accompanied by a flip in the magnitude of contact line tension from positive (0.19 nN) to negative (-0.11 nN).

  2. Contact Lenses in the Laboratory.

    ERIC Educational Resources Information Center

    Kingston, David W.

    1981-01-01

    Summarizes results of a three-item questionnaire returned by 43 Michigan institutions expressing views on wearing contact lenses in chemical laboratories. Questions focused on eye protection, type of protection, and use of contact lenses. (SK)

  3. Design of a structure with low incident and viewing angle dependence inspired by Morpho butterflies

    PubMed Central

    Wang, Wanlin; Zhang, Wang; Gu, Jiajun; Liu, Qinglei; Deng, Tao; Zhang, Di; Lin, Hai-Qing

    2013-01-01

    Morpho butterflies are well known for their brilliant iridescent colors, which arise from periodic arrays of scales. These brilliant colors have a low angle dependence, in contrast to similar phenomena that are commonly caused by the periodic structures. We designed a structure with a low incident and viewing angle dependence inspired by Morpho butterflies. This structure was studied using the finite-difference time-domain method. The lamellae distribution of tree-like structure was found to be the determining factor for producing a low incident angle dependence. Two advanced models were designed to produce a low viewing angle dependence. Model I was constructed using two layers of scales. The particle swarm optimization algorithm was used to construct Model II. The angle dependence of Model II exhibited a large viewing angle range under various incident angles. PMID:24305852

  4. The Application of a Contact Lens Sensor in Detecting 24-Hour Intraocular Pressure-Related Patterns

    PubMed Central

    2016-01-01

    Glaucoma is one of the leading causes of blindness worldwide. Recent studies suggest that intraocular pressure (IOP) fluctuations, peaks, and rhythm are important factors in disease advancement. Yet, current glaucoma management remains hinged on single IOP measurements during clinic hours. To overcome this limitation, 24-hour IOP monitoring devices have been employed and include self-tonometry, permanent IOP, and temporary IOP monitoring. This review discusses each IOP measuring strategy and focuses on the recently FDA-approved contact lens sensor (CLS). The CLS records IOP-related ocular patterns for 24 hours continuously. Using the CLS, IOP-related parameters have been found to be associated with the rate of visual field progression in primary open-angle glaucoma, disease progression in primary angle-closure glaucoma, and various clinical variables in ocular hypertension. The CLS has been used to quantify blink rate and limbal strain and measure the circadian rhythm in a variety of disease states including normal-tension glaucoma and thyroid eye disease. The effects of various IOP-lowering interventions were also characterized using the CLS. CLS provides a unique, safe, and well-tolerated way to study IOP-related patterns in a wide range of disease states. IOP-related patterns may help identify patients most at risk for disease progression and assist with the development of tailored treatments. PMID:27525110

  5. The Application of a Contact Lens Sensor in Detecting 24-Hour Intraocular Pressure-Related Patterns.

    PubMed

    Xu, Sarah C; Gauthier, Angela C; Liu, Ji

    2016-01-01

    Glaucoma is one of the leading causes of blindness worldwide. Recent studies suggest that intraocular pressure (IOP) fluctuations, peaks, and rhythm are important factors in disease advancement. Yet, current glaucoma management remains hinged on single IOP measurements during clinic hours. To overcome this limitation, 24-hour IOP monitoring devices have been employed and include self-tonometry, permanent IOP, and temporary IOP monitoring. This review discusses each IOP measuring strategy and focuses on the recently FDA-approved contact lens sensor (CLS). The CLS records IOP-related ocular patterns for 24 hours continuously. Using the CLS, IOP-related parameters have been found to be associated with the rate of visual field progression in primary open-angle glaucoma, disease progression in primary angle-closure glaucoma, and various clinical variables in ocular hypertension. The CLS has been used to quantify blink rate and limbal strain and measure the circadian rhythm in a variety of disease states including normal-tension glaucoma and thyroid eye disease. The effects of various IOP-lowering interventions were also characterized using the CLS. CLS provides a unique, safe, and well-tolerated way to study IOP-related patterns in a wide range of disease states. IOP-related patterns may help identify patients most at risk for disease progression and assist with the development of tailored treatments. PMID:27525110

  6. [Systemic contact dermatitis].

    PubMed

    Nowak, Daria; Gomułka, Krzysztof; Dziemieszonek, Paulina; Panaszek, Bernard

    2016-01-01

    Systemic contact dermatitis (SCD) is a skin inflammation occurring in a patient after systemic administration of a hapten, which previously caused an allergic contact skin reaction in the same person. Most frequently, hypersensitivity reactions typical for SCD occur after absorption of haptens with food or inhalation. Haptens occur mainly in the forms of metals and compounds present in natural resins, preservatives, food thickeners, flavorings and medicines. For many years, several studies have been conducted on understanding the pathogenesis of SCD in which both delayed type hypersensitivity (type IV) and immediate type I are observed. Components of the complement system are also suspected to attend there. Helper T cells (Th) (Th1 and Th2), cytotoxic T lymphocytes (Tc), and NK cells play a crucial role in the pathogenesis of SCD. They secrete a number of pro-inflammatory cytokines. In addition, regulatory T cells (Tregs) have an important role. They control and inhibit activity of the immune system during inflammation. Tregs release suppressor cytokines and interact directly with a target cell through presentation of immunosuppressive particles at the cell surface. Diagnostic methods are generally the patch test, oral provocation test, elimination diet and lymphocyte stimulation test. There are many kinds of inflammatory skin reactions caused by systemic haptens' distribution. They are manifested in a variety of clinical phenotypes of the disease. PMID:26943310

  7. Allergic Contact Dermatitis

    PubMed Central

    Nelson, Jenny L.

    2010-01-01

    Epicutaneous patch testing is the gold standard method for the diagnosis of allergic contact dermatitis. Despite this knowledge, many clinical dermatologists do not offer patch testing in their offices or offer testing with only a limited number of allergens. Introduced in 1995, the Thin-Layer Rapid Use Epicutaneous Test originally contained 23 allergens and one control. In 2007, five additional allergens were added. This United States Food and Drug Administration-approved patch testing system made patch testing more convenient, and after its introduction, more dermatologists offered patch testing services. However, the number of allergens in the Thin-Layer Rapid Use Epicutaneous Test remains relatively low. Every two years, the North American Contact Dermatitis Group collects and reports the data from patch testing among its members to a standardized series of allergens. In 2005-2006, the Group used a series of 65 allergens. Of the top 30 allergens reported in 2005-2006, 10 were not included in the Thin-Layer Rapid Use Epicutaneous Test. Knowledge of and testing for additional allergens such as these may increase patch testing yield. PMID:20967194

  8. [Genetics of contact allergy].

    PubMed

    Schnuch, A

    2011-10-01

    The genetics of contact allergy (CA) is still only partly understood, despite decades of research. This might be due to inadequately defined phenotypes used in the past. Therefore we suggested studying an extreme phenotype, namely, polysensitization (sensitization to 3 or more unrelated allergens). Another approach to unravel the genetics of CA has been the study of candidate genes. In this review, we summarize studies on the associations between genetic variation (e.g. SNPs) in certain candidate genes and CA. The following polymorphisms and mutations were studied: (1) filaggrin, (2) N-acetyltransferase (NAT1 and 2), (3) glutathione-S-transferase (GST M and T), (4) manganese superoxide dismutase, (5) angiotensin-converting enzyme (ACE), (6) tumor necrosis factor (TNF), and (7) interleukin-16 (IL16). The polymorphisms of NAT1/2, GST M/T, ACE, TNF, and IL16 were shown to be associated with an increased risk of CA. In one of our studies, the increased risk conferred by the TNF and IL16 polymorphisms was confined to polysensitized individuals. Other relevant candidate genes may be identified by studying diseases related to CA in terms of clinical symptoms, a more general pathology (inflammation) and possibly an overlapping genetic background, such as irritant contact dermatitis. PMID:21904893

  9. Determination of the Actual Contact Surface of a Brush Contact

    NASA Technical Reports Server (NTRS)

    Holm, Ragnar

    1944-01-01

    The number of partial contact surfaces of a brush-ring contact is measured by means of a statistical method. The particular brush is fitted with wicks - that is, insulated and cemented cylinders of brush material, terminating in the brush surface. The number of partial contact surfaces can be computed from the length of the rest periods in which such wicks remain without current. Resistance measurements enable the determination of the size of the contact surfaces. The pressure in the actual contact surface of a recently bedded brush is found to be not much lower than the Brinell hardness of the brush.

  10. Negative intergroup contact makes group memberships salient: explaining why intergroup conflict endures.

    PubMed

    Paolini, Stefania; Harwood, Jake; Rubin, Mark

    2010-12-01

    Drawing from the intergroup contact model and self-categorization theory, the authors advanced the novel hypothesis of a valence-salience effect, whereby negative contact causes higher category salience than positive contact. As predicted, in a laboratory experiment of interethnic contact, White Australians (N = 49) made more frequent and earlier reference to ethnicity when describing their ethnic contact partner if she had displayed negative (vs. positive, neutral) nonverbal behavior. In a two-wave experimental study of retrieved intergenerational contact, American young adults (N = 240) reported age to be more salient during negative (vs. positive) contact and negative contact predicted increased episodic and chronic category salience over time. Some evidence for the reverse salience-valence effect was also found. Because category salience facilitates contact generalization, these results suggest that intergroup contact is potentially biased toward worsening intergroup relations; further implications for theory and policy making are discussed.

  11. Receding contact lines: From sliding drops to immersion lithography

    NASA Astrophysics Data System (ADS)

    Winkels, K. G.; Peters, I. R.; Evangelista, F.; Riepen, M.; Daerr, A.; Limat, L.; Snoeijer, J. H.

    2011-02-01

    Instabilities of receding contact lines often occur through the formation of a corner with a very sharp tip. These dewetting structures also appear in the technology of Immersion Lithography, where water is put between the lens and the silicon wafer to increase the optical resolution. In this paper we aim to compare corners appearing in Immersion Lithography to those at the tail of gravity driven-drops sliding down an incline. We use high speed recordings to measure the dynamic contact angle and the sharpness of the corner, for varying contact line velocity. It is found that these quantities behave very similarly for Immersion Lithography and drops on an incline. In addition, the results agree well with predictions by a lubrication model for cornered contact lines, hinting at a generic structure of dewetting corners.

  12. Combined non-contact coordinate measurement system and calibration method

    NASA Astrophysics Data System (ADS)

    Fan, Yiyan; Zhao, Bin

    2015-07-01

    A combined non-contact measurement system comprising attitude angle sensor, angle encoder, laser rangefinder, and total station is adopted to measure the spatial coordinate of the hidden zones in large-scale space. The laser from the total station is aimed at the optical system of the attitude angle sensor to obtain the spatial coordinate and the spatial attitude angles. Then, the angle encoder driven by a stepping motor is rotated to drive the laser rangefinder to direct at the measured point. This approach is used to obtain the distance from the rangefinder to the measured point and the angle of the angle encoder. Finally, the spatial coordinates of the measured point can be calculated by using these measured parameters. For the measurement system, we propose a weighted least squares (WLS) calibration method, in which weights are determined for the angular distribution density. Experimental results show that the measurement system could expand the scale and achieve reliable precision during combined measurement and the measurement error of the weighted least squares method is less than that of the ordinary least square (OLS) method.

  13. Contact position sensor using constant contact force control system

    NASA Technical Reports Server (NTRS)

    Sturdevant, Jay (Inventor)

    1995-01-01

    A force control system (50) and method are provided for controlling a position contact sensor (10) so as to produce a constant controlled contact force therewith. The system (50) includes a contact position sensor (10) which has a contact probe (12) for contacting the surface of a target to be measured and an output signal (V.sub.o) for providing a position indication thereof. An actuator (30) is provided for controllably driving the contact position sensor (10) in response to an actuation control signal (I). A controller (52) receives the position indication signal (V.sub.o) and generates in response thereto the actuation control signal (I) so as to provide a substantially constant selective force (F) exerted by the contact probe (12). The actuation drive signal (I) is generated further in response to substantially linear approximation curves based on predetermined force and position data attained from the sensor (10) and the actuator (30).

  14. Thermal singularity and contact line motion in pool boiling: Effects of substrate wettability.

    PubMed

    Taylor, M T; Qian, Tiezheng

    2016-03-01

    The dynamic van der Waals theory [Phys. Rev. E 75, 036304 (2007)] is employed to model the growth of a single vapor bubble in a superheated liquid on a flat homogeneous substrate. The bubble spreading dynamics in the pool boiling regime has been numerically investigated for one-component van der Waals fluids close to the critical point, with a focus on the effect of the substrate wettability on bubble growth and contact line motion. The substrate wettability is found to control the apparent contact angle and the rate of bubble growth (the rate of total evaporation), through which the contact line speed is determined. An approximate expression is derived for the contact line speed, showing good agreement with the simulation results. This demonstrates that the contact line speed is primarily governed by (1) the circular shape of interface (for slow bubble growth), (2) the constant apparent contact angle, and (3) the constant bubble growth rate. It follows that the contact line speed has a sensitive dependence on the substrate wettability via the apparent contact angle which also determines the bubble growth rate. Compared to hydrophilic surfaces, hydrophobic surfaces give rise to a thinner shape of bubble and a higher rate of total evaporation, which combine to result in a much faster contact line speed. This can be linked to the earlier formation of a vapor film and hence the onset of boiling crisis.

  15. Thermal singularity and contact line motion in pool boiling: Effects of substrate wettability

    NASA Astrophysics Data System (ADS)

    Taylor, M. T.; Qian, Tiezheng

    2016-03-01

    The dynamic van der Waals theory [Phys. Rev. E 75, 036304 (2007), 10.1103/PhysRevE.75.036304] is employed to model the growth of a single vapor bubble in a superheated liquid on a flat homogeneous substrate. The bubble spreading dynamics in the pool boiling regime has been numerically investigated for one-component van der Waals fluids close to the critical point, with a focus on the effect of the substrate wettability on bubble growth and contact line motion. The substrate wettability is found to control the apparent contact angle and the rate of bubble growth (the rate of total evaporation), through which the contact line speed is determined. An approximate expression is derived for the contact line speed, showing good agreement with the simulation results. This demonstrates that the contact line speed is primarily governed by (1) the circular shape of interface (for slow bubble growth), (2) the constant apparent contact angle, and (3) the constant bubble growth rate. It follows that the contact line speed has a sensitive dependence on the substrate wettability via the apparent contact angle which also determines the bubble growth rate. Compared to hydrophilic surfaces, hydrophobic surfaces give rise to a thinner shape of bubble and a higher rate of total evaporation, which combine to result in a much faster contact line speed. This can be linked to the earlier formation of a vapor film and hence the onset of boiling crisis.

  16. Thermal singularity and contact line motion in pool boiling: Effects of substrate wettability.

    PubMed

    Taylor, M T; Qian, Tiezheng

    2016-03-01

    The dynamic van der Waals theory [Phys. Rev. E 75, 036304 (2007)] is employed to model the growth of a single vapor bubble in a superheated liquid on a flat homogeneous substrate. The bubble spreading dynamics in the pool boiling regime has been numerically investigated for one-component van der Waals fluids close to the critical point, with a focus on the effect of the substrate wettability on bubble growth and contact line motion. The substrate wettability is found to control the apparent contact angle and the rate of bubble growth (the rate of total evaporation), through which the contact line speed is determined. An approximate expression is derived for the contact line speed, showing good agreement with the simulation results. This demonstrates that the contact line speed is primarily governed by (1) the circular shape of interface (for slow bubble growth), (2) the constant apparent contact angle, and (3) the constant bubble growth rate. It follows that the contact line speed has a sensitive dependence on the substrate wettability via the apparent contact angle which also determines the bubble growth rate. Compared to hydrophilic surfaces, hydrophobic surfaces give rise to a thinner shape of bubble and a higher rate of total evaporation, which combine to result in a much faster contact line speed. This can be linked to the earlier formation of a vapor film and hence the onset of boiling crisis. PMID:27078445

  17. Angle interferometer cross axis errors

    SciTech Connect

    Bryan, J.B.; Carter, D.L.; Thompson, S.L.

    1994-01-01

    Angle interferometers are commonly used to measure surface plate flatness. An error can exist when the centerline of the double comer cube mirror assembly is not square to the surface plate and the guide bar for the mirror sled is curved. Typical errors can be one to two microns per meter. A similar error can exist in the calibration of rotary tables when the centerline of the double comer cube mirror assembly is not square to the axes of rotation of the angle calibrator and the calibrator axis is not parallel to the rotary table axis. Commercial double comer cube assemblies typically have non-parallelism errors of ten milli-radians between their centerlines and their sides and similar values for non-squareness between their centerlines and end surfaces. The authors have developed a simple method for measuring these errors and correcting them by remachining the reference surfaces.

  18. SEDIMENTATION IN THE ANGLE CENTRIFUGE.

    PubMed

    Pickels, E G

    1943-01-20

    1. Using hemocyanin from Limulus polyphemus as a test material, the process of sedimentation in the angle centrifuge, operating both in vacuum and in the open air, has been investigated. 2. Sedimentation in a given field of force was found less efficient when centrifugation was conducted in the open air, because of thermal convection. 3. Correlations have been made with results obtained in the analytical ultracentrifuge, and a theory of sedimentation in inclined tubes has been presented to explain the experimental results. 4. It has been shown that under proper conditions the angle centrifuge may be used for approximate determinations of particle size. 5. Recommendations, based mostly on experimental evidence, have been made for improving sedimentation and interpreting results. 6. To counteract convective disturbances of either thermal or inertial origin, a satisfactory method has been developed which consists of furnishing the fluid under study with a synthetic density gradient, formed with sucrose or some other non-sedimentable material.

  19. Contact dermatitis in blacks.

    PubMed

    Berardesca, E; Maibach, H I

    1988-07-01

    Black skin is characterized by structural and functional differences such as increased stratum corneum cohesion, melanin content, and stratum corneum layers. These differences seem to make black skin difficult for irritants and light to penetrate, thus explaining the common opinion that skin in blacks is harder and develops contact dermatitis less frequently. The paucity of interpretable epidemiologic data and of clinical and experimental studies does not permit confirmation of this hypothesis, and the few data available are controversial. This article describes the main physiologic differences between black and white barrier function and reviews the literature on irritation, sensitization, and transcutaneous penetration. We found that the data are still too incomplete to generalize on the resistance, or lack thereof, of black skin (versus white skin) to chemical irritation, sensitization, and penetration. PMID:3048818

  20. Update on contact lithotripsy.

    PubMed

    Michel, M S; Köhrmann, K U; Alken, P

    2000-11-01

    Despite the development of extracorporeal shockwave lithotripsy, endoscopic stone removal, with or without intracorporeal lithotripsy, is still an effective minimally invasive alternative for special indications. There is no defined all-purpose lithotripsy procedure for contact lithotripsy. The choice of the lithotripsy procedure for endoscopic stone disintegration depends on a number of different factors, the main one being stone localization. Small calibre, flexible probes (electrohydraulic, pneumatic, laser) are especially appropriate for ureterorenoscopy, but the speed of stone disintegration is a limiting factor. In contrast, large calibre rigid probes (ultrasound) are clearly more effective, but are unsuitable in size for flexible ureterorenoscopy. This indicates that the type and size of the endoscope decisively influences the choice of devices for endoscopic stone disintegration. Additional inhibiting factors are the flexibility or the rigidity of the instrument and the diameter of the working channel. It must be noted that total costs are not only calculated on the purchase of the equipment, but must also cover disposable materials.

  1. Contact dermatitis to fragrances.

    PubMed

    Santucci, B; Cristaudo, A; Cannistraci, C; Picardo, M

    1987-02-01

    2 groups of patients (1200 and 1500 respectively) were patch tested with different concentrations of perfume mix and fragrance raw materials. The study was to evaluate the incidence of contact dermatitis to fragrances in Roma, Italy, and the influence of limited variations in fragrance and perfume mix concentrations on patch test responses. The results showed that a decrease in the perfume mix concentration from 16% to 8% correlated with a decrease in the % of positive patients (from 5.2% to 3.6%). Variations in the concentration of fragrance raw materials did not influence the % of positive reactions in the 2 groups. The perfume mixture at 16% or 8% gave some positive results, without a corresponding reaction to any of the constituents, that were not related to an excited skin syndrome.

  2. Contact dermatitis in blacks.

    PubMed

    Berardesca, E; Maibach, H I

    1988-07-01

    Black skin is characterized by structural and functional differences such as increased stratum corneum cohesion, melanin content, and stratum corneum layers. These differences seem to make black skin difficult for irritants and light to penetrate, thus explaining the common opinion that skin in blacks is harder and develops contact dermatitis less frequently. The paucity of interpretable epidemiologic data and of clinical and experimental studies does not permit confirmation of this hypothesis, and the few data available are controversial. This article describes the main physiologic differences between black and white barrier function and reviews the literature on irritation, sensitization, and transcutaneous penetration. We found that the data are still too incomplete to generalize on the resistance, or lack thereof, of black skin (versus white skin) to chemical irritation, sensitization, and penetration.

  3. Contact dermatitis to Alstroemeria.

    PubMed

    Santucci, B; Picardo, M; Iavarone, C; Trogolo, C

    1985-04-01

    A study was carried out on 50 workers in a floriculture centre to evaluate the incidence of contact dermatitis to Alstroemeria. 3 subjects gave positive reactions to aqueous and ethanolic extracts of cut flowers, stems and leaves. By column chromatography, the allergen was isolated and its chemical structure identified as 6-tuliposide A by proton magnetic resonance and carbon-13 magnetic resonance. Only 6-tuliposide A was isolated from cut flowers, and this gave positive reactions when patch tested at 0.01%; a-methylene-gamma-butyrolactone at 10(-5) (v/v) was positive in the same 3 subjects. Other lactones (gamma-methylene-gamma-butyrolactone, alantolactone, isoalantolactone) were negative at all concentrations used.

  4. Contact sensing from force measurements

    NASA Technical Reports Server (NTRS)

    Bicchi, Antonio; Salisbury, J. K.; Brock, David L.

    1993-01-01

    This article addresses contact sensing (i.e., the problem of resolving the location of a contact, the force at the interface, and the moment about the contact normals). Called 'intrinsic' contact sensing for the use of internal force and torque measurements, this method allows for practical devices that provide simple, relevant contact information in practical robotic applications. Such sensors have been used in conjunction with robot hands to identify objects, determine surface friction, detect slip, augment grasp stability, measure object mass, probe surfaces, and control collision and for a variety of other useful tasks. This article describes the theoretical basis for their operation and provides a framework for future device design.

  5. Organelle remodeling at membrane contact sites.

    PubMed

    Henne, W Mike

    2016-10-01

    Cellular organelles must execute sophisticated biological processes to persist, and often communicate with one another to exchange metabolites and information. Recent studies suggest inter-organelle membrane contact sites (MCSs) are hubs for this cellular cross-talk. MCSs also govern membrane remodeling, thus controlling aspects of organelle shape, identity, and function. Here, we summarize three emerging phenomena that MCSs appear to govern: 1) organelle identity via the non-vesicular exchange of lipids, 2) mitochondrial shape and division, and 3) endosomal migration in response to sterol trafficking. We also discuss the role for ER-endolysosomal contact sites in cholesterol metabolism, and the potential biomedical importance this holds. Indeed, the emerging field inter-organellar cross-talk promises substantial advances in the fields of lipid metabolism and cell signaling.

  6. Angle-resolved scattering spectroscopy of explosives using an external cavity quantum cascade laser

    SciTech Connect

    Suter, Jonathan D.; Bernacki, Bruce E.; Phillips, Mark C.

    2012-04-01

    Investigation of angle-resolved scattering from solid explosives residues on a car door for non-contact sensing geometries. Illumination with a mid-infrared external cavity quantum cascade laser tuning between 7 and 8 microns was detected both with a sensitive single point detector and a hyperspectral imaging camera. Spectral scattering phenomena were discussed and possibilities for hyperspectral imaging at large scattering angles were outlined.

  7. Gaia basic angle monitoring system

    NASA Astrophysics Data System (ADS)

    Gielesen, W.; de Bruijn, D.; van den Dool, T.; Kamphues, F.; Mekking, J.; Calvel, B.; Laborie, A.; Coatantiec, C.; Touzeau, S.; Erdmann, M.; Gare, P.; Monteiro, D.

    2013-09-01

    The Gaia mission1 will create an extraordinarily precise three-dimensional map of more than one billion stars in our Galaxy. The Gaia spacecraft2, built by EADS Astrium, is part of ESA's Cosmic Vision programme and scheduled for launch in 2013. Gaia measures the position, distance and motion of stars with an accuracy of 24 micro-arcsec using two telescopes at a fixed mutual angle of 106.5°, named the `Basic Angle', at an operational temperature of 100 K. This accuracy requires ultra-high stability at cryogenic conditions, which can only be achieved by using Silicon Carbide for both the optical bench and the telescopes. TNO has developed, built and space qualified the Silicon carbide Basic Angle Monitoring (BAM) on-board metrology system3 for this mission, measuring the relative motion of Gaia's telescopes with accuracies in the range of 0.5 micro-arcsec. This is achieved by a system of two laser interferometers able to detect Optical Path Differences (OPD) as small as 1.5 picometer rms. Following a general introduction on Gaia and the use of Silicon Carbide as base material this paper addresses the specific challenges towards the cryogenic application of the Gaia BAM including design, integration and verification/qualification by testing.

  8. OPENING ANGLES OF COLLAPSAR JETS

    SciTech Connect

    Mizuta, Akira; Ioka, Kunihito

    2013-11-10

    We investigate the jet propagation and breakout from the stellar progenitor for gamma-ray burst (GRB) collapsars by performing two-dimensional relativistic hydrodynamic simulations and analytical modeling. We find that the jet opening angle is given by θ{sub j} ∼ 1/5Γ{sub 0} and infer the initial Lorentz factor of the jet at the central engine, Γ{sub 0}, is a few for existing observations of θ{sub j}. The jet keeps the Lorentz factor low inside the star by converging cylindrically via collimation shocks under the cocoon pressure and accelerates at jet breakout before the free expansion to a hollow-cone structure. In this new picture, the GRB duration is determined by the sound crossing time of the cocoon, after which the opening angle widens, reducing the apparent luminosity. Some bursts violating the maximum opening angle θ{sub j,{sub max}} ∼ 1/5 ∼ 12° imply the existence of a baryon-rich sheath or a long-acting jet. We can explain the slopes in both Amati and Yonetoku spectral relations using an off-centered photosphere model, if we make only one assumption that the total jet luminosity is proportional to the initial Lorentz factor of the jet. We also numerically calibrate the pre-breakout model (Bromberg et al.) for later use.

  9. Reducing contact resistance in graphene devices through contact area patterning.

    PubMed

    Smith, Joshua T; Franklin, Aaron D; Farmer, Damon B; Dimitrakopoulos, Christos D

    2013-04-23

    Performance of graphene electronics is limited by contact resistance associated with the metal-graphene (M-G) interface, where unique transport challenges arise as carriers are injected from a 3D metal into a 2D-graphene sheet. In this work, enhanced carrier injection is experimentally achieved in graphene devices by forming cuts in the graphene within the contact regions. These cuts are oriented normal to the channel and facilitate bonding between the contact metal and carbon atoms at the graphene cut edges, reproducibly maximizing "edge-contacted" injection. Despite the reduction in M-G contact area caused by these cuts, we find that a 32% reduction in contact resistance results in Cu-contacted, two-terminal devices, while a 22% reduction is achieved for top-gated graphene transistors with Pd contacts as compared to conventionally fabricated devices. The crucial role of contact annealing to facilitate this improvement is also elucidated. This simple approach provides a reliable and reproducible means of lowering contact resistance in graphene devices to bolster performance. Importantly, this enhancement requires no additional processing steps.

  10. Point contacts in encapsulated graphene

    SciTech Connect

    Handschin, Clevin; Fülöp, Bálint; Csonka, Szabolcs; Makk, Péter; Blanter, Sofya; Weiss, Markus; Schönenberger, Christian; Watanabe, Kenji; Taniguchi, Takashi

    2015-11-02

    We present a method to establish inner point contacts with dimensions as small as 100 nm on hexagonal boron nitride (hBN) encapsulated graphene heterostructures by pre-patterning the top-hBN in a separate step prior to dry-stacking. 2- and 4-terminal field effect measurements between different lead combinations are in qualitative agreement with an electrostatic model assuming point-like contacts. The measured contact resistances are 0.5–1.5 kΩ per contact, which is quite low for such small contacts. By applying a perpendicular magnetic field, an insulating behaviour in the quantum Hall regime was observed, as expected for inner contacts. The fabricated contacts are compatible with high mobility graphene structures and open up the field for the realization of several electron optical proposals.

  11. A Prototype Antifungal Contact Lens

    PubMed Central

    Ciolino, Joseph B.; Hudson, Sarah P.; Mobbs, Ashley N.; Hoare, Todd R.; Iwata, Naomi G.; Fink, Gerald R.

    2011-01-01

    Purpose. To design a contact lens to treat and prevent fungal ocular infections. Methods. Curved contact lenses were created by encapsulating econazole-impregnated poly(lactic-co-glycolic) acid (PLGA) films in poly(hydroxyethyl methacrylate) (pHEMA) by ultraviolet photopolymerization. Release studies were conducted in phosphate-buffered saline at 37°C with continuous shaking. The contact lenses and their release media were tested in an antifungal assay against Candida albicans. Cross sections of the pre- and postrelease contact lenses were characterized by scanning electron microscopy and by Raman spectroscopy. Results. Econazole-eluting contact lenses provided extended antifungal activity against Candida albicans fungi. Fungicidal activity varied in duration and effectiveness depending on the mass of the econazole-PLGA film encapsulated in the contact lens. Conclusions. An econazole-eluting contact lens could be used as a treatment for fungal ocular infections. PMID:21527380

  12. Effects of bolt-hole contact on bearing-bypass damage-onset strength

    NASA Technical Reports Server (NTRS)

    Crews, John H., Jr.; Naik, Rajiv A.

    1991-01-01

    A combined experimental and analytical study was conducted to investigate the effects of bolt-hole contact on the bearing bypass strength of a graphite-epoxy laminate. Tests were conducted on specimens consisting of 16-ply quasi-isotropic T300/5208 laminates with a centrally located hole. Bearing loads were applied through a clearance-fit steel bolt. Damage onset strength and damage mode were determined for each test case. A finite element procedure was used to calculate the bolt-hole stresses and bolt contact for each test case. A finite element procedure was used to calculate the bolt-hole stresses and bolt contact for each measured damage-onset strength. For the tension bearing-bypass cases tested, the bolt contact half-angle was approximately 60 degrees at damage onset. For compression, the contact angle was 20 degrees as the bypass load increased. A corresponding decrease in the bearing damage onset strength was attributed to the decrease in contact angle which made the bearing loads more severe. Hole boundary stresses were also computed by superimposing stresses for separate bearing and bypass loading. Stresses at the specimen net section were accurately approximated by the superposition procedure. However, the peak bearing stresses had large errors because the bolt contact angles were not represented correctly. For compression, peak bearing stress errors of nearly 50 percent were calculated.

  13. Ultrafast angle-resolved photoemission spectroscopy of quantum materials

    NASA Astrophysics Data System (ADS)

    Smallwood, Christopher L.; Kaindl, Robert A.; Lanzara, Alessandra

    2016-07-01

    Techniques in time- and angle-resolved photoemission spectroscopy have facilitated a number of recent advances in the study of quantum materials. We review developments in this field related to the study of incoherent nonequilibrium electron dynamics, the analysis of interactions between electrons and collective excitations, the exploration of dressed-state physics, and the illumination of unoccupied band structure. Future prospects are also discussed.

  14. A Direct analysis of elastic contact using super elements

    NASA Astrophysics Data System (ADS)

    Pedersen, Pauli

    2006-02-01

    Solutions to contact problems are important in mechanical as well as in civil engineering, and even for the most simple problems there is still a need for research results. In the present paper we suggest an alternative finite element procedure and by examples show the need for more knowledge related to the compliance of contact surfaces. The most simple solutions are named Hertz solutions from 1882, and we use some of these solutions for comparison with our finite element results. As a function of the total contact force we find the size of the contact area, the distribution of the contact pressure, and the contact compliance. In models of finite size the compliance depends on the flexibility of the total model, including the boundary condition of the model, and therefore disagreement with the locally based analytical models is expected and found. With computational contact mechanics we can solve more advanced contact problems and treat models that are closer to physical reality. The finite element method is widely used and solutions are obtained by incrementation and/or iteration for these non-linear problems with unknown boundary conditions. Still with these advanced tools the solution is difficult because of extreme sensitivity. Here we present a direct analysis of elastic contact without incrementation and iteration, and the procedure is based on a finite element super element technique. This means that the contacting bodies can be analyzed independently, and are only coupled through a direct analysis with low order super element stiffness matrices. The examples of the present paper are restricted to axisymmetric problems with isotropic, elastic materials and excluding friction. Direct extensions to cases of non-isotropy, including laminates, and to plane and general 3D models are possible.

  15. Thermal contact resistance across a copper-silicon interface

    SciTech Connect

    Khounsary, A.M.; Chojnowski, D.; Assoufid, L.; Worek, W.M.

    1997-10-01

    The issue of thermal contact resistance across metallic interfaces has been investigated for many situations over the past several decades. The application in the present case is contact cooling of high heat load optical substrates. High heat load x-ray mirrors and other optical components used at the Advanced Photon Source (APS) are either internally cooled or contact cooled. In the internally cooled mirrors, a coolant flows through passages configured in the optical substrate. In the contact-cooled case, cooling is provided by placing cooling plates in contact with the mirror to extract the heat. Here, an experimental setup to measure the thermal contact conductance across a silicon-copper (Si-Cu) interface is described, and the results obtained are presented. The resulting thermal contact resistance data are used in estimating the thermo-mechanical and optical performance of optical substrates cooled by interfaced copper cooling blocks. Several factors influence the heat transfer across solid interfaces. These include the material properties, interface pressure, flatness and roughness of the contacting surfaces, temperature, and interstitial material, if any. Results presented show the variation of thermal contact conductance as a function of applied interface pressure for a Cu-Si interface. Various interstitial materials investigated include indium foil, silver foil and a liquid eutectic (Ga-In-Sn). As expected, thermal contact resistance decreases as interface pressure increases, except in the case of the eutectic, in which it was nearly constant. The softer the interstitial material, the lower the thermal contact resistance. Liquid metal provides the lowest thermal contact resistance across the Cu-Si interface, followed by the indium foil, and then the silver foil.

  16. Determining a Surrogate Contact Pair in a Hertzian Contact Problem.

    PubMed

    Sanders, Anthony P; Brannon, Rebecca M

    2011-04-01

    Laboratory testing of contact phenomena can be prohibitively expensive if the interacting bodies are geometrically complicated. This work demonstrates means to mitigate such problems by exploiting the established observation that two geometrically dissimilar contact pairs may exhibit the same contact mechanics. Specific formulas are derived that allow a complicated Hertzian contact pair to be replaced with an inexpensively manufactured and more easily fixtured surrogate pair, consisting of a plane and a spheroid, which has the same (to second-order accuracy) contact area and pressure distribution as the original complicated geometry. This observation is elucidated by using direct tensor notation to review a key assertion in Hertzian theory; namely, geometrically complicated contacting surfaces can be described to second-order accuracy as contacting ellipsoids. The surrogate spheroid geometry is found via spectral decomposition of the original pair's combined Hessian tensor. Some numerical examples using free-form surfaces illustrate the theory, and a laboratory test validates the theory under a common scenario of normally compressed convex surfaces. This theory for a Hertzian contact substitution may be useful in simplifying the contact, wear, or impact testing of complicated components or of their constituent materials.

  17. Pinning of the Contact Line during Evaporation on Heterogeneous Surfaces: Slowdown or Temporary Immobilization? Insights from a Nanoscale Study.

    PubMed

    Zhang, Jianguo; Müller-Plathe, Florian; Leroy, Frédéric

    2015-07-14

    The question of the effect of surface heterogeneities on the evaporation of liquid droplets from solid surfaces is addressed through nonequilibrium molecular dynamics simulations. The mechanism behind contact line pinning which is still unclear is discussed in detail on the nanoscale. Model systems with the Lennard-Jones interaction potential were employed to study the evaporation of nanometer-sized cylindrical droplets from a flat surface. The heterogeneity of the surface was modeled through alternating stripes of equal width but two chemical types. The first type leads to a contact angle of 67°, and the other leads to a contact angle of 115°. The stripe width was varied between 2 and 20 liquid-particle diameters. On the surface with the narrowest stripes, evaporation occurred at constant contact angle as if the surface was homogeneous, with a value of the contact angle as predicted by the regular Cassie-Baxter equation. When the width was increased, the contact angle oscillated during evaporation between two boundaries whose values depend on the stripe width. The evaporation behavior was thus found to be a direct signature of the typical size of the surface heterogeneity domains. The contact angle both at equilibrium and during evaporation could be predicted from a local Cassie-Baxter equation in which the surface composition within a distance of seven fluid-particle diameters around the contact line was considered, confirming the local nature of the interactions that drive the wetting behavior of droplets. More importantly, we propose a nanoscale explanation of pinning during evaporation. Pinning should be interpreted as a drastic slowdown of the contact line dynamics rather than a complete immobilization of it during a transition between two contact angle boundaries.

  18. Fast Grasp Contact Computation for a Serial Robot

    NASA Technical Reports Server (NTRS)

    Shi, Jianying (Inventor); Hargrave, Brian (Inventor); Diftler, Myron A. (Inventor)

    2015-01-01

    A system includes a controller and a serial robot having links that are interconnected by a joint, wherein the robot can grasp a three-dimensional (3D) object in response to a commanded grasp pose. The controller receives input information, including the commanded grasp pose, a first set of information describing the kinematics of the robot, and a second set of information describing the position of the object to be grasped. The controller also calculates, in a two-dimensional (2D) plane, a set of contact points between the serial robot and a surface of the 3D object needed for the serial robot to achieve the commanded grasp pose. A required joint angle is then calculated in the 2D plane between the pair of links using the set of contact points. A control action is then executed with respect to the motion of the serial robot using the required joint angle.

  19. Non Contact Measuring Machine

    NASA Astrophysics Data System (ADS)

    Carvalho, Fernando D.; Sebastiao, Pedro; Henriques, Bernardo G.

    1989-01-01

    One of the problems of the production of cables is the measurement of the thickness plastic cover at the production line. If for some reason the thickness of the plastic is smaller than the minimum necessary several meters of cable may be lost. If the problem exists in the middle of a long cable and the default is not detected in time, the loss will be significant. To solve this problem it is possible to use automatic measuring machines which may detect a default as soon as it happens. It is also possible to interact with the production line in order to avoid any losses. In this paper it is presented a non contact measuring machine, developed for this purpose. The machine uses a laser which is scanned through a field of 80 mm. The interruption of the beam gives information about the external dimension of the object. The technical study of the resolution, sensitivity and precision are presented on the paper. Also the hardware solution and the software are presented. The machine has an interface which allows communication with a PC. The PC may receive information from several measuring units and to interact with machines installed at the production line. The prototype is finished and is going to be tested in the industry.

  20. The Use of Accelerometers and Gyroscopes to Estimate Hip and Knee Angles on Gait Analysis

    PubMed Central

    Alonge, Francesco; Cucco, Elisa; D'Ippolito, Filippo; Pulizzotto, Alessio

    2014-01-01

    In this paper the performance of a sensor system, which has been developed to estimate hip and knee angles and the beginning of the gait phase, have been investigated. The sensor system consists of accelerometers and gyroscopes. A new algorithm was developed in order to avoid the error accumulation due to the gyroscopes drift and vibrations due to the ground contact at the beginning of the stance phase. The proposed algorithm have been tested and compared to some existing algorithms on over-ground walking trials with a commercial device for assisted gait. The results have shown the good accuracy of the angles estimation, also in high angle rate movement. PMID:24828578