Neutrino Mass Models: impact of non-zero reactor angle
International Nuclear Information System (INIS)
King, Stephen F.
2011-01-01
In this talk neutrino mass models are reviewed and the impact of a non-zero reactor angle and other deviations from tri-bi maximal mixing are discussed. We propose some benchmark models, where the only way to discriminate between them is by high precision neutrino oscillation experiments.
Federal Laboratory Consortium — Description:The FTA32 goniometer provides video-based contact angle and surface tension measurement. Contact angles are measured by fitting a mathematical expression...
Equilibrium contact angle or the most-stable contact angle?
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. © 2013 Elsevier B.V. All rights reserved.
Neutrino mass models and the implications of a non-zero reactor angle
International Nuclear Information System (INIS)
King, S.F.
2009-01-01
In this talk we survey some of the recent promising developments in the search for the theory behind neutrino mass and mixing, and indeed all fermion masses and mixing. The talk is organized in terms of a neutrino mass models decision tree according to which the answers to experimental questions provide sign posts to guide through the maze of theoretical models eventually towards a complete theory of flavour and unification. It is also discussed the theoretical implications of the measurement of non-zero reactor angle, as hinted at by recent experimental measurements.
Contact angles on stretched solids
Mensink, Liz; Snoeijer, Jacco
2017-11-01
The surface energy of solid interfaces plays a central role in wetting, as they dictate the liquid contact angle. Yet, it has been challenging to measure the solid surface energies independently, without making use of Young's law. Here we present Molecular Dynamics (MD) simulations by which we measure the surface properties for all interfaces, including the solids. We observe change in contact angles upon stretching the solid substrates, showing that the surface energy is actually strain dependent. This is clear evidence of the so-called Shuttleworth effect, making it necessary to distinguish surface energy from surface tension. We discuss how this effect gives rise to a new class of elasto-capillary phenomena. ERC Consolidator Grant No. 616918.
A thermodynamic model of contact angle hysteresis.
Makkonen, Lasse
2017-08-14
When a three-phase contact line moves along a solid surface, the contact angle no longer corresponds to the static equilibrium angle but is larger when the liquid is advancing and smaller when the liquid is receding. The difference between the advancing and receding contact angles, i.e., the contact angle hysteresis, is of paramount importance in wetting and capillarity. For example, it determines the magnitude of the external force that is required to make a drop slide on a solid surface. Until now, fundamental origin of the contact angle hysteresis has been controversial. Here, this origin is revealed and a quantitative theory is derived. The theory is corroborated by the available experimental data for a large number of solid-liquid combinations. The theory is applied in modelling the contact angle hysteresis on a textured surface, and these results are also in quantitative agreement with the experimental data.
Apparent contact angle and contact angle hysteresis on liquid infused surfaces.
Semprebon, Ciro; McHale, Glen; Kusumaatmaja, Halim
2016-12-21
We theoretically investigate the apparent contact angle and contact angle hysteresis of a droplet placed on a liquid infused surface. We show that the apparent contact angle is not uniquely defined by material parameters, but also has a dependence on the relative size between the droplet and its surrounding wetting ridge formed by the infusing liquid. We derive a closed form expression for the contact angle in the limit of vanishing wetting ridge, and compute the correction for small but finite ridge, which corresponds to an effective line tension term. We also predict contact angle hysteresis on liquid infused surfaces generated by the pinning of the contact lines by the surface corrugations. Our analytical expressions for both the apparent contact angle and contact angle hysteresis can be interpreted as 'weighted sums' between the contact angles of the infusing liquid relative to the droplet and surrounding gas phases, where the weighting coefficients are given by ratios of the fluid surface tensions.
Apparent Contact Angle and Contact Angle Hysteresis on Liquid Infused Surfaces
Semprebon, Ciro; McHale, Glen; Kusumaatmaja, Halim
2016-01-01
We theoretically investigate the apparent contact angle and contact angle hysteresis of a droplet placed on a liquid infused surface. We show that the apparent contact angle is not uniquely defined by material parameters, but also has a strong dependence on the relative size between the droplet and its surrounding wetting ridge formed by the infusing liquid. We derive a closed form expression for the contact angle in the limit of vanishing wetting ridge, and compute the correction for small b...
Contact angle and local wetting at contact line.
Li, Ri; Shan, Yanguang
2012-11-06
This theoretical study was motivated by recent experiments and theoretical work that had suggested the dependence of the static contact angle on the local wetting at the triple-phase contact line. We revisit this topic because the static contact angle as a local wetting parameter is still not widely understood and clearly known. To further clarify the relationship of the static contact angle with wetting, two approaches are applied to derive a general equation for the static contact angle of a droplet on a composite surface composed of heterogeneous components. A global approach based on the free surface energy of a thermodynamic system containing the droplet and solid surface shows the static contact angle as a function of local surface chemistry and local wetting state at the contact line. A local approach, in which only local forces acting on the contact line are considered, results in the same equation. The fact that the local approach agrees with the global approach further demonstrates the static contact angle as a local wetting parameter. Additionally, the study also suggests that the wetting described by the Wenzel and Cassie equations is also the local wetting of the contact line rather than the global wetting of the droplet.
Contact angle of unset elastomeric impression materials.
Menees, Timothy S; Radhakrishnan, Rashmi; Ramp, Lance C; Burgess, John O; Lawson, Nathaniel C
2015-10-01
Some elastomeric impression materials are hydrophobic, and it is often necessary to take definitive impressions of teeth coated with some saliva. New hydrophilic materials have been developed. The purpose of this in vitro study was to compare contact angles of water and saliva on 7 unset elastomeric impression materials at 5 time points from the start of mixing. Two traditional polyvinyl siloxane (PVS) (Aquasil, Take 1), 2 modified PVS (Imprint 4, Panasil), a polyether (Impregum), and 2 hybrid (Identium, EXA'lence) materials were compared. Each material was flattened to 2 mm and a 5 μL drop of distilled water or saliva was dropped on the surface at 25 seconds (t0) after the start of mix. Contact angle measurements were made with a digital microscope at initial contact (t0), t1=2 seconds, t2=5 seconds, t3=50% working time, and t4=95% working time. Data were analyzed with a generalized linear mixed model analysis, and individual 1-way ANOVA and Tukey HSD post hoc tests (α=.05). For water, materials grouped into 3 categories at all time-points: the modified PVS and one hybrid material (Identium) produced the lowest contact angles, the polyether material was intermediate, and the traditional PVS materials and the other hybrid (EXA'lence) produced the highest contact angles. For saliva, Identium, Impregum, and Imprint 4 were in the group with the lowest contact angle at most time points. Modified PVS materials and one of the hybrid materials are more hydrophilic than traditional PVS materials when measured with water. Saliva behaves differently than water in contact angle measurement on unset impression material and produces a lower contact angle on polyether based materials. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.
Contact angle hysteresis on superhydrophobic stripes.
Dubov, Alexander L; Mourran, Ahmed; Möller, Martin; Vinogradova, Olga I
2014-08-21
We study experimentally and discuss quantitatively the contact angle hysteresis on striped superhydrophobic surfaces as a function of a solid fraction, ϕS. It is shown that the receding regime is determined by a longitudinal sliding motion of the deformed contact line. Despite an anisotropy of the texture the receding contact angle remains isotropic, i.e., is practically the same in the longitudinal and transverse directions. The cosine of the receding angle grows nonlinearly with ϕS. To interpret this we develop a theoretical model, which shows that the value of the receding angle depends both on weak defects at smooth solid areas and on the strong defects due to the elastic energy of the deformed contact line, which scales as ϕS(2)lnϕS. The advancing contact angle was found to be anisotropic, except in a dilute regime, and its value is shown to be determined by the rolling motion of the drop. The cosine of the longitudinal advancing angle depends linearly on ϕS, but a satisfactory fit to the data can only be provided if we generalize the Cassie equation to account for weak defects. The cosine of the transverse advancing angle is much smaller and is maximized at ϕS ≃ 0.5. An explanation of its value can be obtained if we invoke an additional energy due to strong defects in this direction, which is shown to be caused by the adhesion of the drop on solid sectors and is proportional to ϕS(2). Finally, the contact angle hysteresis is found to be quite large and generally anisotropic, but it becomes isotropic when ϕS ≤ 0.2.
Contact angle measurement with a smartphone.
Chen, H; Muros-Cobos, Jesus L; Amirfazli, A
2018-03-01
In this study, a smartphone-based contact angle measurement instrument was developed. Compared with the traditional measurement instruments, this instrument has the advantage of simplicity, compact size, and portability. An automatic contact point detection algorithm was developed to allow the instrument to correctly detect the drop contact points. Two different contact angle calculation methods, Young-Laplace and polynomial fitting methods, were implemented in this instrument. The performance of this instrument was tested first with ideal synthetic drop profiles. It was shown that the accuracy of the new system with ideal synthetic drop profiles can reach 0.01% with both Young-Laplace and polynomial fitting methods. Conducting experiments to measure both static and dynamic (advancing and receding) contact angles with the developed instrument, we found that the smartphone-based instrument can provide accurate and practical measurement results as the traditional commercial instruments. The successful demonstration of use of a smartphone (mobile phone) to conduct contact angle measurement is a significant advancement in the field as it breaks the dominate mold of use of a computer and a bench bound setup for such systems since their appearance in 1980s.
Contact angle measurement with a smartphone
Chen, H.; Muros-Cobos, Jesus L.; Amirfazli, A.
2018-03-01
In this study, a smartphone-based contact angle measurement instrument was developed. Compared with the traditional measurement instruments, this instrument has the advantage of simplicity, compact size, and portability. An automatic contact point detection algorithm was developed to allow the instrument to correctly detect the drop contact points. Two different contact angle calculation methods, Young-Laplace and polynomial fitting methods, were implemented in this instrument. The performance of this instrument was tested first with ideal synthetic drop profiles. It was shown that the accuracy of the new system with ideal synthetic drop profiles can reach 0.01% with both Young-Laplace and polynomial fitting methods. Conducting experiments to measure both static and dynamic (advancing and receding) contact angles with the developed instrument, we found that the smartphone-based instrument can provide accurate and practical measurement results as the traditional commercial instruments. The successful demonstration of use of a smartphone (mobile phone) to conduct contact angle measurement is a significant advancement in the field as it breaks the dominate mold of use of a computer and a bench bound setup for such systems since their appearance in 1980s.
Contact angle studies on anodic porous alumina.
Redón, Rocío; Vázquez-Olmos, A; Mata-Zamora, M E; Ordóñez-Medrano, A; Rivera-Torres, F; Saniger, J M
2005-07-15
The preparation of nanostructures using porous anodic aluminum oxide (AAO) as templates involves the introduction of dissolved materials into the pores of the membranes; one way to determine which materials are preferred to fill the pores involves the measurement of the contact angles (theta) of different solvents or test liquids on the AAOs. Thus, we present measurements of contact angles of nine solvents on four different AAO sheets by tensiometric and goniometric methods. From the solvents tested, we found dimethyl sulfoxide (DMSO) and N,N(')-dimethylformamide (DMF) to interact with the AAOs, the polarity of the solvents and the surfaces being the driving force.
Marek, Lindsay C.
2011-01-01
Boundary layer stability was analyzed for the HIFiRE-1 flight vehicle geometry for ground tests conducted at the CUBRC LENS I hypersonic shock test facility and the Langley Research Center (LaRC) 20- inch Mach 6 Tunnel. Boundary layer stability results were compared to transition onset location obtained from discrete heat transfer measurements from thin film gauges during the CUBRC test and spatially continuous heat transfer measurements from thermal phosphor paint data during the LaRC test. The focus of this analysis was on conditions at non-zero angles of attack as stability analysis has already been performed at zero degrees angle of attack. Also, the transition onset data obtained during flight testing was at nonzero angles of attack, so this analysis could be expanded in the future to include the results of the flight test data. Stability analysis was performed using the 2D parabolized stability software suite STABL (Stability and Transition Analysis for Hypersonic Boundary Layers) developed at the University of Minnesota and the mean flow solutions were computed using the DPLR finite volume Navier-Stokes computational fluid dynamics (CFD) solver. A center line slice of the 3D mean flow solution was used for the stability analysis to incorporate the angle of attack effects while still taking advantage of the 2D STABL software suite. The N-factors at transition onset and the value of Re(sub theta)/M(sub e), commonly used to predict boundary layer transition onset, were compared for all conditions analyzed. Ground test data was analyzed at Mach 7.2 and Mach 6.0 and angles of attack of 1deg, 3deg and 5deg. At these conditions, the flow was found to be second mode dominant for the HIFiRE-1 slender cone geometry. On the leeward side of the vehicle, a strong trend of transition onset location with angle of attack was observed as the boundary layer on the leeward side of the vehicle developed inflection points at streamwise positions on the vehicle that correlated to
Experimental Validation of the Invariance of Electrowetting Contact Angle Saturation
Chevalliot, S.; Dhindsa, M.; Kuiper, S.; Heikenfeld, J.
2011-01-01
Basic electrowetting theory predicts that a continued increase in applied voltage will allow contact angle modulation to zero degrees. In practice, the effect of contact angle saturation has always been observed to limit the contact angle modulation, often only down to a contact angle of 60 to 70°.
Dynamic contact angle cycling homogenizes heterogeneous surfaces.
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. Copyright © 2016 Elsevier B.V. All rights reserved.
Dancing droplets: Contact angle, drag, and confinement
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.
Tool Indicates Contact Angles In Bearing Raceways
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.
On accurate determination of contact angle
Concus, P.; Finn, R.
1992-01-01
Methods are proposed that exploit a microgravity environment to obtain highly accurate measurement of contact angle. These methods, which are based on our earlier mathematical results, do not require detailed measurement of a liquid free-surface, as they incorporate discontinuous or nearly-discontinuous behavior of the liquid bulk in certain container geometries. Physical testing is planned in the forthcoming IML-2 space flight and in related preparatory ground-based experiments.
Contact angles of liquid metals on quasicrystals
International Nuclear Information System (INIS)
Bergman, Claire; Girardeaux, Christophe; Perrin-Pellegrino, Carine; Gas, Patrick; Dubois, Jean-Marie; Rivier, Nicolas
2008-01-01
Wetting with μm-sized Pb droplets on thin polycrystalline films of decagonal Al 13 Co 4 is reported. The films were prepared under high vacuum conditions in order to have Pb droplets lying on a clean surface. The method used is sequential deposition and annealing of specific stackings of Al and Co layers of nanometric thicknesses. A 300 nm thick Pb slab was then deposited on top of the films and dewetting experiments were followed in situ in a scanning Auger microprobe. The contact angle between the Pb droplet and the surface of the film is measured to be 49 deg. ± 7 deg. Further investigation performed by cross section transmission electron microscopy allows us to better characterize the interface. Taking into account the rugosity of the film, it is concluded that there is partial wetting of the film, which corresponds to a smaller contact angle. The comparison with other results obtained either with pure metals or with a cubic AlCo compound leads to the conclusion that the wetting behaviour of Pb on the surface of a decagonal compound is close to that of a metal with a high melting point and not significantly different from that of a crystalline compound with a small unit cell
Contact angle distribution of particles at fluid interfaces.
Snoeyink, Craig; Barman, Sourav; Christopher, Gordon F
2015-01-27
Recent measurements have implied a distribution of interfacially adsorbed particles' contact angles; however, it has been impossible to measure statistically significant numbers for these contact angles noninvasively in situ. Using a new microscopy method that allows nanometer-scale resolution of particle's 3D positions on an interface, we have measured the contact angles for thousands of latex particles at an oil/water interface. Furthermore, these measurements are dynamic, allowing the observation of the particle contact angle with high temporal resolution, resulting in hundreds of thousands of individual contact angle measurements. The contact angle has been found to fit a normal distribution with a standard deviation of 19.3°, which is much larger than previously recorded. Furthermore, the technique used allows the effect of measurement error, constrained interfacial diffusion, and particle property variation on the contact angle distribution to be individually evaluated. Because of the ability to measure the contact angle noninvasively, the results provide previously unobtainable, unique data on the dynamics and distribution of the adsorbed particles' contact angle.
A contact angle hysteresis model based on the fractal structure of contact line.
Wu, Shuai; Ma, Ming
2017-11-01
Contact angle is one of the most popular concept used in fields such as wetting, transport and microfludics. In practice, different contact angles such as equilibrium, receding and advancing contact angles are observed due to hysteresis. The connection among these contact angles is important in revealing the chemical and physical properties of surfaces related to wetting. Inspired by the fractal structure of contact line, we propose a single parameter model depicting the connection of the three angles. This parameter is decided by the fractal structure of the contact line. The results of this model agree with experimental observations. In certain cases, it can be reduced to other existing models. It also provides a new point of view in understanding the physical nature of the contact angle hysteresis. Interestingly, some counter-intuitive phenomena, such as the binary receding angles, are indicated in this model, which are waited to be validated by experiments. Copyright © 2017 Elsevier Inc. All rights reserved.
Contact angle hysteresis: a review of fundamentals and applications
Eral, Burak; 't Mannetje, Dieter; Oh, J.M.
2013-01-01
Contact angle hysteresis is an important physical phenomenon. It is omnipresent in nature and also plays a crucial role in various industrial processes. Despite its relevance, there is a lack of consensus on how to incorporate a description of contact angle hysteresis into physical models. To
The modified Cassie’s equation and contact angle hysteresis
Xu, Xianmin; Wang, Xiaoping
2012-01-01
In this paper, we derive a modified Cassie's equation for wetting on chemically patterned surfaces from a homogenization approach. The derivation reveals that effective contact angle is a local average of the static contact angle along the contact line which describes all possible equilibrium states including the local minimum of the free energy of the system. The usual Cassie's state which corresponds to the global minimum is only a special case. We then discuss the contact angle hysteresis on chemically patterned surfaces. © 2012 Springer-Verlag.
The modified Cassie’s equation and contact angle hysteresis
Xu, Xianmin
2012-08-29
In this paper, we derive a modified Cassie\\'s equation for wetting on chemically patterned surfaces from a homogenization approach. The derivation reveals that effective contact angle is a local average of the static contact angle along the contact line which describes all possible equilibrium states including the local minimum of the free energy of the system. The usual Cassie\\'s state which corresponds to the global minimum is only a special case. We then discuss the contact angle hysteresis on chemically patterned surfaces. © 2012 Springer-Verlag.
Campbell, Darren; Carnell, Sarah Maria; Eden, Russell John
2013-05-01
Contact angle, as a representative measure of surface wettability, is often employed to interpret contact lens surface properties. The literature is often contradictory and can lead to confusion. This literature review is part of a series regarding the analysis of hydrogel contact lenses using contact angle techniques. Here we present an overview of contact angle terminology, methodology, and analysis. Having discussed this background material, subsequent parts of the series will discuss the analysis of contact lens contact angles and evaluate differences in published laboratory results. The concepts of contact angle, wettability and wetting are presented as an introduction. Contact angle hysteresis is outlined and highlights the advantages in using dynamic analytical techniques over static methods. The surface free energy of a material illustrates how contact angle analysis is capable of providing supplementary surface characterization. Although single values are able to distinguish individual material differences, surface free energy and dynamic methods provide an improved understanding of material behavior. The frequently used sessile drop, captive bubble, and Wilhelmy plate techniques are discussed. Their use as both dynamic and static methods, along with the advantages and disadvantages of each technique, is explained. No single contact angle technique fully characterizes the wettability of a material surface, and the application of complimenting methods allows increased characterization. At present, there is not an ISO standard method designed for soft materials. It is important that each contact angle technique has a standard protocol, as small protocol differences between laboratories often contribute to a variety of published data that are not easily comparable.
Measurement of Critical Contact Angle in a Microgravity Space Experiment
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.
Contact angle of sessile drops in Lennard-Jones systems.
Becker, Stefan; Urbassek, Herbert M; Horsch, Martin; Hasse, Hans
2014-11-18
Molecular dynamics simulations are used for studying the contact angle of nanoscale sessile drops on a planar solid wall in a system interacting via the truncated and shifted Lennard-Jones potential. The entire range between total wetting and dewetting is investigated by varying the solid-fluid dispersive interaction energy. The temperature is varied between the triple point and the critical temperature. A correlation is obtained for the contact angle in dependence of the temperature and the dispersive interaction energy. Size effects are studied by varying the number of fluid particles at otherwise constant conditions, using up to 150,000 particles. For particle numbers below 10,000, a decrease of the contact angle is found. This is attributed to a dependence of the solid-liquid surface tension on the droplet size. A convergence to a constant contact angle is observed for larger system sizes. The influence of the wall model is studied by varying the density of the wall. The effective solid-fluid dispersive interaction energy at a contact angle of θ = 90° is found to be independent of temperature and to decrease linearly with the solid density. A correlation is developed that describes the contact angle as a function of the dispersive interaction, the temperature, and the solid density. The density profile of the sessile drop and the surrounding vapor phase is described by a correlation combining a sigmoidal function and an oscillation term.
Contact angle control of sessile drops on a tensioned web
Park, Janghoon; Kim, Dongguk; Lee, Changwoo
2018-04-01
In this study, the influence of the change of tension applied to flexible and thin web substrate on the contact angle of sessile drop in roll-to-roll system was investigated. Graphene oxide and deionized water solutions were used in the experiments. Tension was changed to 29, 49, and 69 N, and the casting distance of the micropipette and the material was set to 10, 20, and 40 mm, and the droplet volume was set to 10, 20, and 30 μL, respectively. Statistical analysis of three variables and analysis of the variance methodology showed that the casting distance was most significant for the contact angle change, and the most interesting tension variable was also affected. The change in tension caused the maximum contact angle to change by 5.5°. The tension was not uniform in the width direction. When the droplet was applied in the same direction in the width direction, it was confirmed that the tension unevenness had great influence on the contact angle up to 11°. Finally, the casting distance, which has a large effect on the contact angle, was calibrated in the width direction to reduce the width direction contact angle deviation to 1%. This study can be applied to fine patterning research using continuous inkjet printing and aerosol jet printing, which are roll-to-roll processes based on droplet handling.
Contact angle of a nanodrop on a nanorough solid surface.
Berim, Gersh O; Ruckenstein, Eli
2015-02-21
The contact angle of a cylindrical nanodrop on a nanorough solid surface is calculated, for both hydrophobic and hydrophilic surfaces, using the density functional theory. The emphasis of the paper is on the dependence of the contact angle on roughness. The roughness is modeled by rectangular pillars of infinite length located on the smooth surface of a substrate, with fluid-pillar interactions different in strength from the fluid-substrate ones. It is shown that for hydrophobic substrates the trend of the contact angle to increase with increasing roughness, which was noted in all previous studies, is not universally valid, but depends on the fluid-pillar interactions, pillar height, interpillar distance, as well as on the size of the drop. For hydrophilic substrate, an unusual kink-like dependence of the contact angle on the nanodrop size is found which is caused by the change in the location of the leading edges of the nanodrop on the surface. It is also shown that the Wenzel and Cassie-Baxter equations can not explain all the peculiarities of the contact angle of a nanodrop on a nanorough surface.
The Influence of Dynamic Contact Angle on Wetting Dynamics
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.
Repulsion-based model for contact angle saturation in electrowetting.
Ali, Hassan Abdelmoumen Abdellah; Mohamed, Hany Ahmed; Abdelgawad, Mohamed
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.
Fabrication of zero contact angle ultra-super hydrophilic surfaces.
Jothi Prakash, C G; Clement Raj, C; Prasanth, R
2017-06-15
Zero contact angle surfaces have been created with the combined effect of nanostructure and UV illumination. The contact angle of titanium surface has been optimized to 3.25°±1°. with nanotubular structures through electrochemical surface modification. The porosity and surface energy of tubular TiO 2 layer play critical role over the surface wettability and the hydrophilicity of the surface. The surface free energy has been enhanced from 23.72mJ/m 2 (bare titanium surface) to 87.11mJ/m 2 (nanotubular surface). Similar surface with TiO 2 nanoparticles coating shows superhydrophilicity with contact angle up to 5.63°±0.95°. This implies liquid imbibition and surface curvature play a crucial role in surface hydrophilicity. The contact angle has been further reduced to 0°±0.86° by illuminating the surface with UV radiation. Results shows that by tuning the nanotube morphology, highly porous surfaces can be fabricated to reduce contact angle and enhance wettability. This study provides an insight into the inter-relationship between surface structural factors and ultra-superhydrophilic surfaces which can help to optimize thermal hydraulic and self cleaning surfaces. Copyright © 2017. Published by Elsevier Inc.
Contact angle measurements at the colemanite and realgar surfaces
Koca, Sabiha; Savas, Mehmet
2004-03-01
Colemanite is one of the most important boron minerals and covers an important part of Turkey's boron mineral deposits. The friable nature of the colemanite tends to produce a large amount of fines. Flotation appears to be a promising technique to recover colemanite from such fines. During flotation process, selectivity problem arises between colemanite and associated gangue minerals such as realgar. There is a close relationship between floatability of minerals and contact angle. Therefore, surface hydrophobicity of colemanite and realgar minerals were investigated by receding contact angle measurements in the absence and presence of flotation reagents. The water contact angle values at the colemanite surface remained almost unchanged at 32-35° in the solutions of potassium amyl xanthate (KAX), potassium ethyl xanthate (KEX) and petroleum sulphanate (R825) while another petroleum sulphanate (R840), sodium oleate and tallow amine (Armac-T) affected hydrophobicity of colemanite, and the contact angle values increased up to 47°. The contact angle values of 62, 63, 45, 46, 39, and 43° at the realgar surface were obtained in the solutions of KAX, KEX, sodium oleate, R825, R840 and Armac-T, respectively.
Non-contact measurement of rotation angle with solo camera
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.
Determination of the Contact Angle Based on the Casimir Effect
Mazuruk, Konstantin; Volz, Martin P.
2015-01-01
On a macroscopic scale, a nonreactive liquid partially covering a homogeneous solid surface will intersect the solid at an angle called the contact angle. For molten metals and semiconductors, the contact angle is materially dependent upon both the solid and liquid and typical values fall in the range 80-170 deg, depending on the crucible material. On a microscopic scale, there does not exist a precise and sharp contact angle but rather the liquid and solid surfaces merge smoothly and continuously. Consider the example of the so called detached Bridgman crystal growth process. In this technique, a small gap is formed between the growing crystal and the crucible. At the crystal/melt interface, a meniscus ring is formed. Its width can be in the range of a few micrometers, approaching a microscopic scale. It then becomes questionable to describe the shape of this meniscus by the contact angle. A more advanced treatment of the interface is needed and here we propose such a refined model. The interaction of the liquid surface with the solid can be calculated by considering two forces: a short-range repulsive force and a longer range (up to a few micrometers) Casimir or van der Waals force.
Capillary surfaces in a wedge: Differing contact angles
Concus, Paul; Finn, Robert
1994-01-01
The possible zero-gravity equilibrium configurations of capillary surfaces u(x, y) in cylindrical containers whose sections are (wedge) domains with corners are investigated mathematically, for the case in which the contact angles on the two sides of the wedge may differ. In such a situation the behavior can depart in significant qualitative ways from that for which the contact angles on the two sides are the same. Conditions are described under which such qualitative changes must occur. Numerically computed surfaces are depicted to indicate the behavior.
Dynamic Contact Angle at the Nanoscale: A Unified View.
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.
Contact Angle Measurements Using a Simplified Experimental Setup
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…
Simulation of capillary flow with a dynamic contact angle
van Mourik, S; Veldman, AEP; Dreyer, ME
2005-01-01
A number of theoretical and empirical dynamic contact angle (DCA) models have been tested in a numerical simulation of liquid reorientation in microgravity for which experimental validation data are available. It is observed that the DCA can have a large influence on liquid dynamics in microgravity.
A "Conveyor Belt" Model for the Dynamic Contact Angle
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…
Evaluation of the Contact Angle from Molecular Simulations.
Czech Academy of Sciences Publication Activity Database
Škvára, J.; Škvor, J.; Nezbeda, Ivo
2018-01-01
Roč. 44, č. 3 (2018), s. 190-199 ISSN 0892-7022 R&D Projects: GA ČR GA15-19542S Institutional support: RVO:67985858 Keywords : contact angle * argon droplet * surface molecules Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 1.254, year: 2016
Drop shape visualization and contact angle measurement on curved surfaces.
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. Copyright © 2011 Elsevier Inc. All rights reserved.
Control of polyaniline conductivity and contact angles by partial protonation
Czech Academy of Sciences Publication Activity Database
Blinova, Natalia V.; Stejskal, Jaroslav; Trchová, Miroslava; Prokeš, J.
2008-01-01
Roč. 57, č. 1 (2008), s. 66-69 ISSN 0959-8103 R&D Projects: GA MŠk ME 847; GA ČR GA202/06/0419 Institutional research plan: CEZ:AV0Z40500505 Keywords : conducting polymer * conductivity * contact angle Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.029, year: 2008
Contact angles of wetting and water stability of soil structure
Kholodov, V. A.; Yaroslavtseva, N. V.; Yashin, M. A.; Frid, A. S.; Lazarev, V. I.; Tyugai, Z. N.; Milanovskiy, E. Yu.
2015-06-01
From the soddy-podzolic soils and typical chernozems of different texture and land use, dry 3-1 mm aggregates were isolated and sieved in water. As a result, water-stable aggregates and water-unstable particles composing dry 3-1 mm aggregates were obtained. These preparations were ground, and contact angles of wetting were determined by the static sessile drop method. The angles varied from 11° to 85°. In most cases, the values of the angles for the water-stable aggregates significantly exceeded those for the water-unstable components. In terms of carbon content in structural units, there was no correlation between these parameters. When analyzing the soil varieties separately, the significant positive correlation between the carbon content and contact angle of aggregates was revealed only for the loamy-clayey typical chernozem. Based on the multivariate analysis of variance, the value of contact wetting angle was shown to be determined by the structural units belonging to water-stable or water-unstable components of macroaggregates and by the land use type. In addition, along with these parameters, the texture has an indirect effect.
Dynamic contact angle of water-based titanium oxide nanofluid
2013-01-01
This paper presents an investigation into spreading dynamics and dynamic contact angle of TiO2-deionized water nanofluids. Two mechanisms of energy dissipation, (1) contact line friction and (2) wedge film viscosity, govern the dynamics of contact line motion. The primary stage of spreading has the contact line friction as the dominant dissipative mechanism. At the secondary stage of spreading, the wedge film viscosity is the dominant dissipative mechanism. A theoretical model based on combination of molecular kinetic theory and hydrodynamic theory which incorporates non-Newtonian viscosity of solutions is used. The model agreement with experimental data is reasonable. Complex interparticle interactions, local pinning of the contact line, and variations in solid–liquid interfacial tension are attributed to errors. PMID:23759071
Contact Angles and Surface Tension of Germanium-Silicon Melts
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.
Measurement of Capillary Radius and Contact Angle within Porous Media.
Ravi, Saitej; Dharmarajan, Ramanathan; Moghaddam, Saeed
2015-12-01
The pore radius (i.e., capillary radius) and contact angle determine the capillary pressure generated in a porous medium. The most common method to determine these two parameters is through measurement of the capillary pressure generated by a reference liquid (i.e., a liquid with near-zero contact angle) and a test liquid. The rate of rise technique, commonly used to determine the capillary pressure, results in significant uncertainties. In this study, we utilize a recently developed technique for independently measuring the capillary pressure and permeability to determine the equivalent minimum capillary radii and contact angle of water within micropillar wick structures. In this method, the experimentally measured dryout threshold of a wick structure at different wicking lengths is fit to Darcy's law to extract the maximum capillary pressure generated by the test liquid. The equivalent minimum capillary radii of different wick geometries are determined by measuring the maximum capillary pressures generated using n-hexane as the working fluid. It is found that the equivalent minimum capillary radius is dependent on the diameter of pillars and the spacing between pillars. The equivalent capillary radii of micropillar wicks determined using the new method are found to be up to 7 times greater than the current geometry-based first-order estimates. The contact angle subtended by water at the walls of the micropillars is determined by measuring the capillary pressure generated by water within the arrays and the measured capillary radii for the different geometries. This mean contact angle of water is determined to be 54.7°.
Capillary Rise: Validity of the Dynamic Contact Angle Models.
Wu, Pingkeng; Nikolov, Alex D; Wasan, Darsh T
2017-08-15
The classical Lucas-Washburn-Rideal (LWR) equation, using the equilibrium contact angle, predicts a faster capillary rise process than experiments in many cases. The major contributor to the faster prediction is believed to be the velocity dependent dynamic contact angle. In this work, we investigated the dynamic contact angle models for their ability to correct the dynamic contact angle effect in the capillary rise process. We conducted capillary rise experiments of various wetting liquids in borosilicate glass capillaries and compared the model predictions with our experimental data. The results show that the LWR equations modified by the molecular kinetic theory and hydrodynamic model provide good predictions on the capillary rise of all the testing liquids with fitting parameters, while the one modified by Joos' empirical equation works for specific liquids, such as silicone oils. The LWR equation modified by molecular self-layering model predicts well the capillary rise of carbon tetrachloride, octamethylcyclotetrasiloxane, and n-alkanes with the molecular diameter or measured solvation force data. The molecular self-layering model modified LWR equation also has good predictions on the capillary rise of silicone oils covering a wide range of bulk viscosities with the same key parameter W(0), which results from the molecular self-layering. The advantage of the molecular self-layering model over the other models reveals the importance of the layered molecularly thin wetting film ahead of the main meniscus in the energy dissipation associated with dynamic contact angle. The analysis of the capillary rise of silicone oils with a wide range of bulk viscosities provides new insights into the capillary dynamics of polymer melts.
Contact angle change during evaporation of near-critical liquids
Nikolayev, Vadim; Hegseth, John; Beysens, Daniel
1998-11-01
An unexpected change of the dynamic contact angle was recently observed in a near-critical liquid-gas system in a space experiment. While the near-critical liquid completely wets a solid under equilibrium conditions, the apparent contact angle changed from 0^circ to about 120^circ during evaporation. We propose an explanation for this phenomenon by taking into account vapor recoil due to evaporation (motion of the vapor from the free liquid surface). This force is normal to the vapor-liquid interface and is directed towards the liquid. It increases sharply near the triple contact line. Near the critical point, where the surface tension force is very weak, the vapor recoil force can be important enough to change the apparent contact angle. A similar effect can also explain the drying of a heater during boiling at high heat flux. The drying greatly reduces the heat transfer to the liquid causing the heater to melt. This phenomenon is called ``boiling crisis", ``burnout" or ``Departure from Nuclear Boiling". We report the preliminary results of the numerical simulation of the liquid evaporation by the Boundary Element method.
Effect of contact angle hysteresis on moving liquid film integrity.
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.
Surfactant modified clays’ consistency limits and contact angles
Directory of Open Access Journals (Sweden)
S Akbulut
2012-07-01
Full Text Available This study was aimed at preparing a surfactant modified clay (SMC and researching the effect of surfactants on clays' contact angles and consistency limits; clay was thus modified by surfactants formodifying their engineering properties. Seven surfactants (trimethylglycine, hydroxyethylcellulose octyl phenol ethoxylate, linear alkylbenzene sulfonic acid, sodium lauryl ether sulfate, cetyl trimethylammonium chloride and quaternised ethoxylated fatty amine were used as surfactants in this study. The experimental results indicated that SMC consistency limits (liquid and plastic limits changedsignificantly compared to those of natural clay. Plasticity index and liquid limit (PI-LL values representing soil class approached the A-line when zwitterion, nonionic, and anionic surfactant percentageincreased. However, cationic SMC became transformed from CH (high plasticity clay to MH (high plasticity silt class soils, according to the unified soil classification system (USCS. Clay modifiedwith cationic and anionic surfactants gave higher and lower contact angles than natural clay, respectively.
Feng, Dong-Xia; Nguyen, Anh V
2017-10-01
The floatability of solid particles on the water surface governs many natural phenomena and industrial processes including film flotation and froth flotation separation of coal and valuable minerals. For many years, the contact angle (CA) has been postulated as the key factor in determining the particle floatability. Indeed, the maximum force (tenacity) supporting the flotation of fine spheres was conjectured to occur when the apical angle of the contact circle is equal to the contact angle. In this paper, the model predictions are reviewed and compared with experimental results. It is shown that CA can be affected by many physical and chemical factors such as surface roughness and chemical heterogeneity and can have a range of values known as the CA hysteresis. This multiple-valued CA invalidates the available theories on the floatability of spheres. Even the intuitive replacement of CA by the advancing (maximum) CA in the classical theories can be wrong. A few new examples are also reviewed and analyzed to demonstrate the significance of CA variation in controlling the particle floatability. They include the pinning of the contact line at the sharp edge, known as the Gibbs inequality condition, and the nearby interaction among floating particles, known as lateral inter-particle interaction. It is concluded that our quantitative understanding of the floatability of real particles being irregular and heterogeneous both morphologically and chemically is still far from being satisfactory. Copyright © 2017 Elsevier B.V. All rights reserved.
Contact angle of water droplet on apatite single crystals
International Nuclear Information System (INIS)
Suzuki, Takaomi; Hirose, Go; Oishi, Shuji
2004-01-01
Contact angles of water droplets on well-formed crystals of strontium and barium chlorapatites, Sr 5 Cl(PO 4 ) 3 and Ba 5 Cl(PO 4 ) 3 , were observed. The contact angles of water on (1 0 1-bar 0) and (1 0 1-bar 1) faces of Sr 5 Cl(PO 4 ) 3 were 74±8 deg. and 53±5 deg. and those on (1 0 1-bar 0) and (1 0 1-bar 1) faces of Ba 5 Cl(PO 4 ) 3 were 52±5 deg. and 33±1 deg., respectively. The surface tensions of the crystals were calculated using Neumann's equation. They were 39.2±50 and 52.0±3.0 mJ m -2 for (1 0 1-bar 0) and (1 0 1-bar 1) faces of Sr 5 Cl(PO 4 ) 3 , 52.5±2.9 and 63.0±0.5 mJ m -2 for (1 0 1-bar 0) and (1 0 1-bar 1) faces of Ba 5 Cl(PO 4 ) 3 , respectively. The (1 0 1-bar 1) face has larger surface tension than (1 0 1-bar 0) face for both crystals. The chlorapatite crystals have tendency to elongate in directions during the crystal growth process, indicating that (1 0 1-bar 0) face is more stable than (1 0 1-bar 1) face. This nature of crystal morphology is consistent with the surface tensions estimated from the water contact angles. The higher density of Ba 5 Cl(PO 4 ) 3 than Sr 5 Cl(PO 4 ) 3 is considered to cause the smaller contact angles of water droplet on Ba 5 Cl(PO 4 ) 3 crystal than that on Sr 5 Cl(PO 4 ) 3 crystal because the attractive force between the heavier atoms brings the larger surface tension of solid
Large area optical mapping of surface contact angle.
Dutra, Guilherme; Canning, John; Padden, Whayne; Martelli, Cicero; Dligatch, Svetlana
2017-09-04
Top-down contact angle measurements have been validated and confirmed to be as good if not more reliable than side-based measurements. A range of samples, including industrially relevant materials for roofing and printing, has been compared. Using the top-down approach, mapping in both 1-D and 2-D has been demonstrated. The method was applied to study the change in contact angle as a function of change in silver (Ag) nanoparticle size controlled by thermal evaporation. Large area mapping reveals good uniformity for commercial Aspen paper coated with black laser printer ink. A demonstration of the forensic and chemical analysis potential in 2-D is shown by uncovering the hidden CsF initials made with mineral oil on the coated Aspen paper. The method promises to revolutionize nanoscale characterization and industrial monitoring as well as chemical analyses by allowing rapid contact angle measurements over large areas or large numbers of samples in ways and times that have not been possible before.
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 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.
Harikrishnan, A. R.; Dhar, Purbarun; Agnihotri, Prabhat K.; Gedupudi, Sateesh; Das, Sarit K.
2018-04-01
Dynamic wettability and contact angle hysteresis can be correlated to shed insight onto any solid-liquid interaction. Complex fluids are capable of altering the expected hysteresis and dynamic wetting behavior due to interfacial interactions. We report the effect of capillary number on the dynamic advancing and receding contact angles of surfactant-based nanocolloidal solutions on hydrophilic, near hydrophobic, and superhydrophobic surfaces by performing forced wetting and de-wetting experiments by employing the embedded needle method. A segregated study is performed to infer the contributing effects of the constituents and effects of particle morphology. The static contact angle hysteresis is found to be a function of particle and surfactant concentrations and greatly depends on the nature of the morphology of the particles. An order of estimate of line energy and a dynamic flow parameter called spreading factor and the transient variations of these parameters are explored which sheds light on the dynamics of contact line movement and response to perturbation of three-phase contact. The Cox-Voinov-Tanner law was found to hold for hydrophilic and a weak dependency on superhydrophobic surfaces with capillary number, and even for the complex fluids, with a varying degree of dependency for different fluids.
Surface tension and contact angles: Molecular origins and associated microstructure
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.
Iliev, Stanimir; Pesheva, Nina; Iliev, Pavel
2018-04-01
We report here on the contact angle hysteresis, appearing when a liquid meniscus is in contact with doubly sinusoidal wavelike patterned surfaces in Wenzel's wetting regime. Using the full capillary model we obtain numerically the contact angle hysteresis as a function of the surface roughness factor and the equilibrium contact angle for a block case and a kink case contact line depinning mechanism. We find that the dependencies of the contact angle hysteresis on the surface roughness factor are different for the different contact line depinning mechanisms. These dependencies are different also for the two types of rough surfaces we studied. The relations between advancing, receding, and equilibrium contact angles are investigated. A comparison with the existing asymptotical, numerical, and experimental results is carried out.
Capillary contact angle in a completely wet groove.
Parry, A O; Malijevský, A; Rascón, C
2014-10-03
We consider the phase equilibria of a fluid confined in a deep capillary groove of width L with identical side walls and a bottom made of a different material. All walls are completely wet by the liquid. Using density functional theory and interfacial models, we show that the meniscus separating liquid and gas phases at two phase capillary coexistence meets the bottom capped end of the groove at a capillary contact angle θ(cap)(L) which depends on the difference between the Hamaker constants. If the bottom wall has a weaker wall-fluid attraction than the side walls, then θ(cap) > 0 even though all the isolated walls are themselves completely wet. This alters the capillary condensation transition which is now first order; this would be continuous in a capped capillary made wholly of either type of material. We show that the capillary contact angle θ(cap)(L) vanishes in two limits, corresponding to different capillary wetting transitions. These occur as the width (i) becomes macroscopically large, and (ii) is reduced to a microscopic value determined by the difference in Hamaker constants. This second wetting transition is characterized by large scale fluctuations and essential critical singularities arising from marginal interfacial interactions.
A Congruence Theorem for Minimal Surfaces in $S^{5}$ with Constant Contact Angle
Montes, Rodrigo Ristow; Verderesi, Jose A.
2006-01-01
We provide a congruence theorem for minimal surfaces in $S^5$ with constant contact angle using Gauss-Codazzi-Ricci equations. More precisely, we prove that Gauss-Codazzi-Ricci equations for minimal surfaces in $S^5$ with constant contact angle satisfy an equation for the Laplacian of the holomorphic angle. Also, we will give a characterization of flat minimal surfaces in $S^5$ with constant contact angle.
Diminution of contact angle hysteresis under the influence of an oscillating force.
Manor, Ofer
2014-06-17
We suggest a simple quantitative model for the diminution of contact angle hysteresis under the influence of an oscillatory force invoked by thermal fluctuations, substrate vibrations, acoustic waves, or oscillating electric fields. Employing force balance rather than the usual description of contact angle hysteresis in terms of Gibbs energy, we highlight that a wetting system, such as a sessile drop or a bubble adhered to a solid substrate, appears at long times to be partially or fully independent of contact angle hysteresis and thus independent of static friction forces, as a result of contact line pinning. We verify this theory by studying several well-known experimental observations such as the approach of an arbitrary contact angle toward the Young contact angle and the apparent decrease (or increase) in an advancing (or a receding) contact angle under the influence of an external oscillating force.
Monaghan, Gail M; Hsu, Wen-Hao; Lewis, Cara L; Saltzman, Elliot; Hamill, Joseph; Holt, Kenneth G
2014-09-01
Clinically, foot structures are assessed intrinsically - relation of forefoot to rearfoot and rearfoot to leg. We have argued that, from a biomechanical perspective, the interaction of the foot with the ground may influence forces and torques that are propagated through the lower extremity. We proposed that a more appropriate measure is an extrinsic one that may predict the angle the foot makes with ground at contact. The purposes of this study were to determine if the proposed measure predicts contact angles of the forefoot and rearfoot and assess if the magnitude of those angles influences amplitude and duration of foot eversion during running. With the individual in prone, extrinsic clinical forefoot and rearfoot angles were measured relative to the caudal edge of the examination table. Participants ran over ground while frontal plane forefoot and rearfoot contact angles, forefoot and rearfoot eversion amplitude and duration were measured. Participants were grouped twice, once based on forefoot contact inversion angle (moderatemedian) and once based on rearfoot contact inversion angle (moderatemedian). The forefoot and rearfoot extrinsic clinical angles predicted, respectively, the forefoot and rearfoot angles at ground contact. Large forefoot contact angles were associated with greater amplitudes (but not durations) of forefoot and rearfoot eversion during stance. Rearfoot contact angles, however, were associated with neither amplitudes nor durations of forefoot and rearfoot eversion. Possible mechanisms for the increased risk of running injuries associated with large forefoot angles are discussed. Copyright © 2014 Elsevier Ltd. All rights reserved.
Zhang, Bo; Wang, Jianjun; Liu, Zhiping; Zhang, Xianren
2014-01-01
The application of Cassie equation to microscopic droplets is recently under intense debate because the microdroplet dimension is often of the same order of magnitude as the characteristic size of substrate heterogeneities, and the mechanism to describe the contact angle of microdroplets is not clear. By representing real surfaces statistically as an ensemble of patterned surfaces with randomly or regularly distributed heterogeneities (patches), lattice Boltzmann simulations here show that the contact angle of microdroplets has a wide distribution, either continuous or discrete, depending on the patch size. The origin of multiple contact angles observed is ascribed to the contact line pinning effect induced by substrate heterogeneities. We demonstrate that the local feature of substrate structure near the contact line determines the range of contact angles that can be stabilized, while the certain contact angle observed is closely related to the contact line width. PMID:25059292
A method to measure internal contact angle in opaque systems by magnetic resonance imaging.
Zhu, Weiqin; Tian, Ye; Gao, Xuefeng; Jiang, Lei
2013-07-23
Internal contact angle is an important parameter for internal wettability characterization. However, due to the limitation of optical imaging, methods available for contact angle measurement are only suitable for transparent or open systems. For most of the practical situations that require contact angle measurement in opaque or enclosed systems, the traditional methods are not effective. Based upon the requirement, a method suitable for contact angle measurement in nontransparent systems is developed by employing MRI technology. In the Article, the method is demonstrated by measuring internal contact angles in opaque cylindrical tubes. It proves that the method also shows great feasibility in transparent situations and opaque capillary systems. By using the method, contact angle in opaque systems could be measured successfully, which is significant in understanding the wetting behaviors in nontransparent systems and calculating interfacial parameters in enclosed systems.
Moment-angle manifolds, intersection of quadrics and higher dimensional contact manifolds
Barreto, Yadira; Verjovsky, Alberto
2013-01-01
We construct new examples of contact manifolds in arbitrarily large dimensions. These manifolds which we call quasi moment-angle manifolds, are closely related to the classical moment-angle manifolds.
Technique to measure contact angle of micro/nanodroplets using atomic force microscopy
International Nuclear Information System (INIS)
Jung, Yong Chae; Bhushan, Bharat
2008-01-01
Contact angle is the primary parameter that characterizes wetting; however, the measurement techniques have been limited to droplets with a diameter as low as about 50 μm. The authors developed an atomic force microscopy-based technique to measure the contact angle of micro- and nanodroplets deposited using a modified nanoscale dispensing tip. The obtained contact angle results were compared with those of a macrodroplet (2.1 mm diameter). It was found that the contact angle on various surfaces decreases with decreasing the droplet size
Study of the Correlation Between Contact Angle Values with the Polarity of Liquids
Syahara, Muhammad Alwi; Kurniawan, Fredy; Anggriawan, Wahyu
2015-01-01
Contact angle measurement is a technique which can be used to determine the surface properties of a substance and observe the interaction of surfaces. When polar liquid dropped on a non-polar solid, it will make an interaction that can observed from the contact angle. In simple way, the different polarity of the solid and the liquid sample will affect to the contact angle obtained. In this work the value of contact angle will be correlated to the polarity of the sample. The results showed tha...
CONTACT ANGLE OF YUCCA MOUNTAIN WELDED TUFF WITH WATER AND BRINES
International Nuclear Information System (INIS)
H. Kalia
2006-01-01
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
Modeling contact angle hysteresis of a liquid droplet sitting on a cosine wave-like pattern surface.
Promraksa, Arwut; Chen, Li-Jen
2012-10-15
A liquid droplet sitting on a hydrophobic surface with a cosine wave-like square-array pattern in the Wenzel state is simulated by using the Surface Evolver to determine the contact angle. For a fixed drop volume, multiple metastable states are obtained at two different surface roughnesses. Unusual and non-circular shape of the three-phase contact line of a liquid droplet sitting on the model surface is observed due to corrugation and distortion of the contact line by structure of the roughness. The contact angle varies along the contact line for each metastable state. The maximum and minimum contact angles among the multiple metastable states at a fixed viewing angle correspond to the advancing and the receding contact angles, respectively. It is interesting to observe that the advancing/receding contact angles (and contact angle hysteresis) are a function of viewing angle. In addition, the receding (or advancing) contact angles at different viewing angles are determined at different metastable states. The contact angle of minimum energy among the multiple metastable states is defined as the most stable (equilibrium) contact angle. The Wenzel model is not able to describe the contact angle along the three-phase contact line. The contact angle hysteresis at different drop volumes is determined. The number of the metastable states increases with increasing drop volume. Drop volume effect on the contact angles is also discussed. Crown Copyright © 2012. Published by Elsevier Inc. All rights reserved.
Investigation of the Dynamic Contact Angle Using a Direct Numerical Simulation Method.
Zhu, Guangpu; Yao, Jun; Zhang, Lei; Sun, Hai; Li, Aifen; Shams, Bilal
2016-11-15
A large amount of residual oil, which exists as isolated oil slugs, remains trapped in reservoirs after water flooding. Numerous numerical studies are performed to investigate the fundamental flow mechanism of oil slugs to improve flooding efficiency. Dynamic contact angle models are usually introduced to simulate an accurate contact angle and meniscus displacement of oil slugs under a high capillary number. Nevertheless, in the oil slug flow simulation process, it is unnecessary to introduce the dynamic contact angle model because of a negligible change in the meniscus displacement after using the dynamic contact angle model when the capillary number is small. Therefore, a critical capillary number should be introduced to judge whether the dynamic contact model should be incorporated into simulations. In this study, a direct numerical simulation method is employed to simulate the oil slug flow in a capillary tube at the pore scale. The position of the interface between water and the oil slug is determined using the phase-field method. The capacity and accuracy of the model are validated using a classical benchmark: a dynamic capillary filling process. Then, different dynamic contact angle models and the factors that affect the dynamic contact angle are analyzed. The meniscus displacements of oil slugs with a dynamic contact angle and a static contact angle (SCA) are obtained during simulations, and the relative error between them is calculated automatically. The relative error limit has been defined to be 5%, beyond which the dynamic contact angle model needs to be incorporated into the simulation to approach the realistic displacement. Thus, the desired critical capillary number can be determined. A three-dimensional universal chart of critical capillary number, which functions as static contact angle and viscosity ratio, is given to provide a guideline for oil slug simulation. Also, a fitting formula is presented for ease of use.
The bifurcation diagram of drops in a sphere/plane geometry: influence of contact angle hysteresis
de Ruiter, Riëlle; van Gorcum, M.; Semprebon, C.; Duits, Michael H.G.; Brinkmann, M.; Mugele, Friedrich Gunther
2014-01-01
We study liquid drops that are present in a generic geometry, namely the gap in between a sphere and a plane. For the ideal system without contact angle hysteresis, the drop position is solely dependent on the contact angle, drop volume, and sphere/ plane separation distance. Performing a geometric
A singular perturbation limit of diffused interface energy with a fixed contact angle condition
Kagaya, Takashi; Tonegawa, Yoshihiro
2016-01-01
We study a general asymptotic behavior of critical points of a diffused interface energy with a fixed contact angle condition defined on a domain $\\Omega \\subset \\mathbb{R}^n$. We show that the limit varifold derived from the diffused energy satisfies a generalized contact angle condition on the boundary under a set of assumptions.
Li, F.; Li, F.; Mugele, Friedrich Gunther
2008-01-01
Contact angle hysteresis caused by random pinning forces is a major obstacle in moving small quantities of liquid on solid surfaces. Here, we demonstrate that the contact angle hysteresis for sessile drops in electrowetting almost disappears with increasing alternating voltage, whereas for direct
Apparent-contact-angle model at partial wetting and evaporation: impact of surface forces.
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.
Estimation of bearing contact angle in-situ by X-ray kinematography
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.
Xu, Z N
2014-12-01
In this study, an error analysis is performed to study real water drop images and the corresponding numerically generated water drop profiles for three widely used static contact angle algorithms: the circle- and ellipse-fitting algorithms and the axisymmetric drop shape analysis-profile (ADSA-P) algorithm. The results demonstrate the accuracy of the numerically generated drop profiles based on the Laplace equation. A significant number of water drop profiles with different volumes, contact angles, and noise levels are generated, and the influences of the three factors on the accuracies of the three algorithms are systematically investigated. The results reveal that the above-mentioned three algorithms are complementary. In fact, the circle- and ellipse-fitting algorithms show low errors and are highly resistant to noise for water drops with small/medium volumes and contact angles, while for water drop with large volumes and contact angles just the ADSA-P algorithm can meet accuracy requirement. However, this algorithm introduces significant errors in the case of small volumes and contact angles because of its high sensitivity to noise. The critical water drop volumes of the circle- and ellipse-fitting algorithms corresponding to a certain contact angle error are obtained through a significant amount of computation. To improve the precision of the static contact angle measurement, a more accurate algorithm based on a combination of the three algorithms is proposed. Following a systematic investigation, the algorithm selection rule is described in detail, while maintaining the advantages of the three algorithms and overcoming their deficiencies. In general, static contact angles over the entire hydrophobicity range can be accurately evaluated using the proposed algorithm. The ease of erroneous judgment in static contact angle measurements is avoided. The proposed algorithm is validated by a static contact angle evaluation of real and numerically generated water drop
Drop rebound after impact: the role of the receding contact angle.
Antonini, C; Villa, F; Bernagozzi, I; Amirfazli, A; Marengo, M
2013-12-31
Data from the literature suggest that the rebound of a drop from a surface can be achieved when the wettability is low, i.e., when contact angles, measured at the triple line (solid-liquid-air), are high. However, no clear criterion exists to predict when a drop will rebound from a surface and which is the key wetting parameter to govern drop rebound (e.g., the "equilibrium" contact angle, θeq, the advancing and the receding contact angles, θA and θR, respectively, the contact angle hysteresis, Δθ, or any combination of these parameters). To clarify the conditions for drop rebound, we conducted experimental tests on different dry solid surfaces with variable wettability, from hydrophobic to superhydrophobic surfaces, with advancing contact angles 108° contact angles 89° contact angle is the key wetting parameter that influences drop rebound, along with surface hydrophobicity: for the investigated impact conditions (drop diameter 2.4 contact angles higher than 100°. Also, the drop rebound time decreased by increasing the receding contact angle. It was also shown that in general care must be taken when using statically defined wetting parameters (such as advancing and receding contact angles) to predict the dynamic behavior of a liquid on a solid surface because the dynamics of the phenomenon may affect surface wetting close to the impact point (e.g., as a result of the transition from the Cassie-Baxter to Wenzel state in the case of the so-called superhydrophobic surfaces) and thus affect the drop rebound.
Drop deposition on surfaces with contact-angle hysteresis: Liquid-bridge stability and breakup
Akbari, Amir; Hill, Reghan J.
2015-01-01
We study the stability and breakup of liquid bridges with a free contact line on a surface with contact-angle hysteresis under zero-gravity conditions. Theoretical predictions of the stability limits are validated by experimental measurements. Experiments are conducted in a water-methanol-silicon oil system where the gravity force is offset by buoyancy. We highlight cases where stability is lost during the transition from a pinned-pinned to pinned-free interface when the receding contact angl...
Wang, Liming; Wei, Jingjing; Su, Zhaohui
2011-12-20
High contact angle hysteresis on polyelectrolyte multilayers (PEMs) ion-paired with hydrophobic perfluorooctanoate anions is reported. Both the bilayer number of PEMs and the ionic strength of deposition solutions have significant influence on contact angle hysteresis: higher ionic strength and greater bilayer number cause increased contact angle hysteresis values. The hysteresis values of ~100° were observed on smooth PEMs and pinning of the receding contact line on hydrophilic defects is implicated as the cause of hysteresis. Surface roughness can be used to further tune the contact angle hysteresis on the PEMs. A surface with extremely high contact angle hysteresis of 156° was fabricated when a PEM was deposited on a rough substrate coated with submicrometer scale silica spheres. It was demonstrated that this extremely high value of contact angle hysteresis resulted from the penetration of water into the rough asperities on the substrate. The same substrate hydrophobized by chemical vapor deposition of 1H,1H,2H,2H-perfluorooctyltriethoxysilane exhibits high advancing contact angle and low hysteresis. © 2011 American Chemical Society
Influence of Contact Angle, Growth Angle and Melt Surface Tension on Detached Solidification of InSb
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.
Contact angle adjustment in equation-of-state-based pseudopotential model.
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.
Measuring contact angle and meniscus shape with a reflected laser beam.
Eibach, T F; Fell, D; Nguyen, H; Butt, H J; Auernhammer, G K
2014-01-01
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.
Schmitt, M; Groß, K; Grub, J; Heib, F
2015-06-01
Contact angle determination by sessile drop technique is essential to characterise surface properties in science and in industry. Different specific angles can be observed on every solid which are correlated with the advancing or the receding of the triple line. Different procedures and definitions for the determination of specific angles exist which are often not comprehensible or reproducible. Therefore one of the most important things in this area is to build standard, reproducible and valid methods for determining advancing/receding contact angles. This contribution introduces novel techniques to analyse dynamic contact angle measurements (sessile drop) in detail which are applicable for axisymmetric and non-axisymmetric drops. Not only the recently presented fit solution by sigmoid function and the independent analysis of the different parameters (inclination, contact angle, velocity of the triple point) but also the dependent analysis will be firstly explained in detail. These approaches lead to contact angle data and different access on specific contact angles which are independent from "user-skills" and subjectivity of the operator. As example the motion behaviour of droplets on flat silicon-oxide surfaces after different surface treatments is dynamically measured by sessile drop technique when inclining the sample plate. The triple points, the inclination angles, the downhill (advancing motion) and the uphill angles (receding motion) obtained by high-precision drop shape analysis are independently and dependently statistically analysed. Due to the small covered distance for the dependent analysis (contact angle determination. They are characterised by small deviations of the computed values. Additional to the detailed introduction of this novel analytical approaches plus fit solution special motion relations for the drop on inclined surfaces and detailed relations about the reactivity of the freshly cleaned silicon wafer surface resulting in acceleration
DEFF Research Database (Denmark)
Andersen, Nis Korsgaard; Taboryski, Rafael J.
2017-01-01
Contact angle measurements are a fast and simple way to measure surface properties and is therefore widely used to measure surface energy and quantify wetting of a solid surface by a liquid substance. In common praxis contact angle measurements are done with sessile drops on a horizontal surface...... fitted to a drop profile derived from the Young-Laplace equation. When measuring the wetting behaviour by tilting experiments this is not possible since it involves moving drops that are not in equilibrium. Here we present a fitting technique capable of determining the contact angle of asymmetric drops...
Application and development of non contact angle-wide viewing system in vitreous retinal surgery
Directory of Open Access Journals (Sweden)
Rong-Hua He
2016-07-01
Full Text Available Wide-angle viewing system as an important auxiliary device can clearly observe the whole fundus field of vision in vitreous surgery, which enable vitreoretinal surgery more efficient, safer and more effective. So it has very high application value in ophthalmologic operation. In this paper, we studied the development and application of wide-angle viewing system in vitreoretinal surgery in recent years, from which we summed up the advantage of non-contact wide-angle viewing system in clinical field, and pointed out the shortcomings. The ultimate goal is to make the non-contact wide-angle viewing system better applied in vitreous surgery.
How pinning and contact angle hysteresis govern quasi-static liquid drop transfer.
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.
Kozbial, Andrew; Trouba, Charlie; Liu, Haitao; Li, Lei
2017-01-31
Elucidating the intrinsic water wettability of the graphitic surface has increasingly attracted research interests, triggered by the recent finding that the well-established hydrophobicity of graphitic surfaces actually results from airborne hydrocarbon contamination. Currently, static water contact angle (WCA) is often used to characterize the intrinsic water wettability of graphitic surfaces. In the current paper, we show that because of the existence of defects, static WCA does not necessarily characterize the intrinsic water wettability. Freshly exfoliated graphite of varying qualities, characterized using atomic force microscopy and Raman spectroscopy, was studied using static, advancing, and receding WCA measurements. The results showed that graphite of different qualities (i.e., defect density) always has a similar advancing WCA, but it could have very different static and receding WCAs. This finding indicates that defects play an important role in contact angle measurements, and the static contact angle does not always represent the intrinsic water wettability of pristine graphite. On the basis of the experimental results, a qualitative model is proposed to explain the effect of defects on static, advancing, and receding contact angles. The model suggests that the advancing WCA reflects the intrinsic water wettability of pristine (defect-free) graphite. Our results showed that the advancing WCA for pristine graphite is 68.6°, which indicates that graphitic carbon is intrinsically mildly hydrophilic.
Tatara, Shingo; Kuzumoto, Yasutaka; Kitamura, Masatoshi
2016-04-01
The water wettability of Au surfaces has been controlled using various benzenethiol derivatives including 4-methylbenzenethiol, pentafluorobenzenethiol, 4-flubrobenzenethiol, 4-methoxy-benzenethiol, 4-nitrobenzenethiol, and 4-hydroxybenzenethiol. The water contact angle of the Au surface modified with the benzenethiol derivative was found to vary in the wide range of 30.9° to 88.3°. The contact angle of the modified Au films annealed was also measured in order to investigate their thermal stability. The change in the contact angle indicated that the modified surface is stable at temperatures below about 400 K. Meanwhile, the activation energy of desorption from the modified surface was estimated from the change in the contact angle. The modified Au surface was also examined using X-ray photoelectron spectroscopy.
Contact angle goniometry on single micron-scale fibers for composites
DEFF Research Database (Denmark)
Hansen, Daniel; Bomholt, Niels; Jeppesen, Jonas Camillus
2017-01-01
Probing the wetting properties of microfibers by polymer resins is of significant interest for the rational design of composite materials. Here, we demonstrate the measurement of contact angles on wetted micron scale fibers by imaging the fluid meniscus with telecentric optics at a spatial...... resolution of 4 um followed by automated image analysis. The meniscus is described as a catenary in the zero gravity approximation and by fitting this to the measured profile, the contact angle is obtained at the intersection between the fluid and the fiber surface. The method is validated by measuring...... agreement between con-tact angles for the PMMA/H2O system for fibers with diameters 20–800 um and for sessile drops. The ability of the method to discriminate contact angles for a series of commercial glass fibers against epoxy resin is successfully demonstrated. AFM imaging shows that the surface...
DEFF Research Database (Denmark)
Holm, René; Borkenfelt, Simon; Allesø, Morten
2016-01-01
for a compound is determined by its contact angle to a liquid, which in the present study was measured using the sessile drop method applied to a disc compact of the compound. Precise determination of the contact angle is important should it be used to either rank compounds or selected excipients to e.......g. increase the wetting from a solid dosage form. Since surface roughness of the compact has been suggested to influence the measurement this study investigated if the surface quality, in terms of surface porosity, had an influence on the measured contact angle. A correlation to surface porosity was observed......, however for six out of seven compounds similar results were obtained by applying a standard pressure (866MPa) to the discs in their preparation. The data presented in the present work therefore suggest that a constant high pressure should be sufficient for most compounds when determining the contact angle...
Effect of the meniscus contact angle during early regimes of spontaneous imbibition in nanochannels
DEFF Research Database (Denmark)
Karna, Nabin Kumar; Oyarzua, Elton; Walther, Jens Honore
2016-01-01
study, large scale atomistic simulations are conducted to investigate capillary imbibition of water in slit silica nanochannels with heights between 4 and 18 nm. We find that the meniscus contact angle remains constant during the inertial regime and its value depends on the height of the channel. We...... also find that the meniscus velocity computed at the channel entrance is related to the particular value of the meniscus contact angle. Moreover, during the subsequent visco-inertial regime, as the influence of viscosity increases, the meniscus contact angle is found to be time dependent for all...... the channels under study. Furthermore, we propose an expression for the time evolution of the dynamic contact angle in nanochannels which, when incorporated into Bosanquet's equation, satisfactorily explains the initial capillary rise....
The rose petal effect and the role of advancing water contact angles for drop confinement
DEFF Research Database (Denmark)
Mandsberg, Nikolaj Kofoed; Taboryski, Rafael J.
2017-01-01
We studied the role of advancing water contact angles on superhydrophobic surfaces that exhibited strong pinning effects as known in nature from rose petals. Textured surfaces were engineered in silicon by lithographical techniques. The textures were comprised of hexagonal microstructures...
A Simple Approach for Local Contact Angle Determination on a Heterogeneous Surface
Wu, Jinbo; Zhang, Mengying; Wang, Xiang; Li, Shunbo; Wen, Weijia
2011-01-01
We report a simple approach for measuring the local contact angle of liquids on a heterogeneous surface consisting of intersected hydrophobic and hydrophilic patch arrays, specifically by employing confocal microscopy and the addition of a very low
Contact angles on a soft solid: from Young's law to Neumann's law.
Marchand, Antonin; Das, Siddhartha; Snoeijer, Jacco H; Andreotti, Bruno
2012-12-07
The contact angle that a liquid drop makes on a soft substrate does not obey the classical Young's relation, since the solid is deformed elastically by the action of the capillary forces. The finite elasticity of the solid also renders the contact angles differently from those predicted by Neumann's law, which applies when the drop is floating on another liquid. Here, we derive an elastocapillary model for contact angles on a soft solid by coupling a mean-field model for the molecular interactions to elasticity. We demonstrate that the limit of a vanishing elastic modulus yields Neumann's law or a variation thereof, depending on the force transmission in the solid surface layer. The change in contact angle from the rigid limit to the soft limit appears when the length scale defined by the ratio of surface tension to elastic modulus γ/E reaches the range of molecular interactions.
A review of factors that affect contact angle and implications for flotation practice.
Chau, T T; Bruckard, W J; Koh, P T L; Nguyen, A V
2009-09-30
Contact angle and the wetting behaviour of solid particles are influenced by many physical and chemical factors such as surface roughness and heterogeneity as well as particle shape and size. A significant amount of effort has been invested in order to probe the correlation between these factors and surface wettability. Some of the key investigations reported in the literature are reviewed here. It is clear from the papers reviewed that, depending on many experimental conditions such as the size of the surface heterogeneities and asperities, surface cleanliness, and the resolution of measuring equipment and data interpretation, obtaining meaningful contact angle values is extremely difficult and such values are reliant on careful experimental control. Surface wetting behaviour depends on not only surface texture (roughness and particle shape), and surface chemistry (heterogeneity) but also on hydrodynamic conditions in the preparation route. The inability to distinguish the effects of each factor may be due to the interplay and/or overlap of two or more factors in each system. From this review, it was concluded that: Surface geometry (and surface roughness of different scales) can be used to tune the contact angle; with increasing surface roughness the apparent contact angle decreases for hydrophilic materials and increases for hydrophobic materials. For non-ideal surfaces, such as mineral surfaces in the flotation process, kinetics plays a more important role than thermodynamics in dictating wettability. Particle size encountered in flotation (10-200 microm) showed no significant effect on contact angle but has a strong effect on flotation rate constant. There is a lack of a rigid quantitative correlation between factors affecting wetting, wetting behaviour and contact angle on minerals; and hence their implication for flotation process. Specifically, universal correlation of contact angle to flotation recovery is still difficult to predict from first principles
International Nuclear Information System (INIS)
Amend, Katharina; Klein, Markus
2017-01-01
The paper presents a three-dimensional numerical simulation for water running down inclined surfaces using OpenFOAM. This research project aims at developing a CFD model to describe the run down behavior of liquids and the resulting wash down of fission products on surfaces in the reactor containment. An empirical contact angle model with wetted history is introduced as well as a filtered randomized initial contact angle field. Simulation results are in good agreement with the experiments. Experimental Investigation on Passive.
Energy Technology Data Exchange (ETDEWEB)
Amend, Katharina; Klein, Markus [Univ. der Bundeswehr Muenchen, Neubiberg (Germany). Inst. for Numerical Methods in Aerospace Engineering
2017-07-15
The paper presents a three-dimensional numerical simulation for water running down inclined surfaces using OpenFOAM. This research project aims at developing a CFD model to describe the run down behavior of liquids and the resulting wash down of fission products on surfaces in the reactor containment. An empirical contact angle model with wetted history is introduced as well as a filtered randomized initial contact angle field. Simulation results are in good agreement with the experiments. Experimental Investigation on Passive.
Wang, Lijuan; Liang, Jinsheng; Di, Xingfu; Tang, Qingguo
2014-05-01
The cleanability of easy-to-clean ceramic glazes doped with nanometer far-infrared materials was compared with that of some high-quality household ceramic glazes from the market. The cleanability was evaluated by the contact angle measurement using a sessile drop method with a Dataphysics OCA-30 contact angle analyzer. The results showed that the difference of contact angles of water on the glazes before soiling and after cleaning could be used as a parameter for evaluating the cleanability of the glazes. The relationship between cleanability and surface properties, such as surface free energy and surface topography, was investigated. The surface free energy of the samples and their components were calculated using van Oss acid-base approach. By measuring advancing and receding contact angles, the contact angle hysteresis of the ceramic glazes due to the surface topography was investigated. It was shown that the cleanability of ceramic glazes containing nanometer far-infrared materials (NFIM) is better than that of household ceramic glazes from market, due to a higher ratio of electron-acceptor parameter to electron-donor parameter, which led to the effect of water hydration as well as better hydrophilic property and increased smoothness. The contact angle measurement not only accurately evaluates the cleanability of the ceramic glazes, but also has a contribution to the study of cleanability theory. Moreover, this method is simple, convenient and less sample-consumption.
van Damme, H.S.; Hogt, A.H.; Feijen, Jan
1986-01-01
Dynamic contact angles and contact-angle hysteresis of a series of poly(n-alkyl methacrylates) (PAMA) were investigated using the Wilhelmy plate technique. The mobility of polymer surface chains, segments, and side groups affected the measured contact angles and their hysteresis. A model is
A noise-resistant ADSA-PH algorithm for superhydrophobic surface’s static contact angle evaluation
Z. N. Xu
2017-01-01
The blur around the contact points significantly decreases the evaluated static contact angle for superhydrophobic surface which is clearly presented in the paper. To improve the accuracy in the evaluated static contact angle for superhydrophobic surface, an accurate static contact angle algorithm, namely ADSA-PH (axisymmetric drop shape analysis-profile and height), is proposed. It discards the extracted drop edge points close to the contact points and makes use of the residual points and th...
Effects of Evaporation/Condensation on Spreading and Contact Angle of a Volatile Liquid Drop
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.
Contact-angle hysteresis on periodic microtextured surfaces: Strongly corrugated liquid interfaces.
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.
Contact angle determination procedure and detection of an invisible surface film
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.
Directory of Open Access Journals (Sweden)
M.S. Nadiye–Tabbiruka
2009-12-01
Full Text Available Aerosil samples, heat treated and then silylated with various silanes at various temperatures have been characterised by adsorption of ethanol at 293 K. Adsorption isotherms were plotted and the BET specific surface areas were determined. Contact angles were measured by the captive bubble method at the three phase contact line in ethanol, on glass slides similarly modified. Silylation was found to alter the ethanol adsorptive properties on aerosil and increase the contact angles on the glass slides to extents that depend on the silane used as well as the concentration of residual silanols and that of surface silyl groups.
Effect of surface texturing on superoleophobicity, contact angle hysteresis, and "robustness".
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
Color-gradient lattice Boltzmann model for simulating droplet motion with contact-angle hysteresis.
Ba, Yan; Liu, Haihu; Sun, Jinju; Zheng, Rongye
2013-10-01
Lattice Boltzmann method (LBM) is an effective tool for simulating the contact-line motion due to the nature of its microscopic dynamics. In contact-line motion, contact-angle hysteresis is an inherent phenomenon, but it is neglected in most existing color-gradient based LBMs. In this paper, a color-gradient based multiphase LBM is developed to simulate the contact-line motion, particularly with the hysteresis of contact angle involved. In this model, the perturbation operator based on the continuum surface force concept is introduced to model the interfacial tension, and the recoloring operator proposed by Latva-Kokko and Rothman is used to produce phase segregation and resolve the lattice pinning problem. At the solid surface, the color-conserving wetting boundary condition [Hollis et al., IMA J. Appl. Math. 76, 726 (2011)] is applied to improve the accuracy of simulations and suppress spurious currents at the contact line. In particular, we present a numerical algorithm to allow for the effect of the contact-angle hysteresis, in which an iterative procedure is used to determine the dynamic contact angle. Numerical simulations are conducted to verify the developed model, including the droplet partial wetting process and droplet dynamical behavior in a simple shear flow. The obtained results are compared with theoretical solutions and experimental data, indicating that the model is able to predict the equilibrium droplet shape as well as the dynamic process of partial wetting and thus permits accurate prediction of contact-line motion with the consideration of contact-angle hysteresis.
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.
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.
Wetting of biopolymer coatings: contact angle kinetics and image analysis investigation.
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. © 2011 American Chemical Society
Kuchin, Igor V; Starov, Victor M
2016-05-31
A theory of contact angle hysteresis of a meniscus inside thin capillaries with smooth, homogeneous solid walls is developed in terms of surface forces (disjoining/conjoining pressure isotherm) using a quasi-equilibrium approach. The disjoining/conjoining pressure isotherm includes electrostatic, intermolecular, and structural components. The values of the static receding θr, advancing θa, and equilibrium θe contact angles in thin capillaries were calculated on the basis of the shape of the disjoining/conjoining pressure isotherm. It was shown that both advancing and receding contact angles depend on the capillary radius. The suggested mechanism of the contact angle hysteresis has a direct experimental confirmation: the process of receding is accompanied by the formation of thick β-films on the capillary walls. The effect of the transition from partial to complete wetting in thin capillaries is predicted and analyzed. This effect takes place in very thin capillaries, when the receding contact angle decreases to zero.
Chen, Cong; Zhang, Ning; Li, Weizhong; Song, Yongchen
2015-12-15
Functional groups on silica surfaces under CO2 sequestration conditions are complex due to reactions among supercritical CO2, brine and silica. Molecular dynamics simulations have been performed to investigate the effects of hydroxyl functional groups on wettability. It has been found that wettability shows a strong dependence on functional groups on silica surfaces: silanol number density, space distribution, and deprotonation/protonation degree. For neutral silica surfaces with crystalline structure (Q(3), Q(3)/Q(4), Q(4)), as silanol number density decreases, contact angle increases from 33.5° to 146.7° at 10.5 MPa and 318 K. When Q(3) surface changes to an amorphous structure, water contact angle increases 20°. Water contact angle decreases about 12° when 9% of silanol groups on Q(3) surface are deprotonated. When the deprotonation degree increases to 50%, water contact angle decreases to 0. The dependence of wettability on silica surface functional groups was used to analyze contact angle measurement ambiguity in literature. The composition of silica surfaces is complicated under CO2 sequestration conditions, the results found in this study may help to better understand wettability of CO2/brine/silica system.
Holm, René; Borkenfelt, Simon; Allesø, Morten; Andersen, Jens Enevold Thaulov; Beato, Stefania; Holm, Per
2016-02-10
Compounds wettability is critical for a number of central processes including disintegration, dispersion, solubilisation and dissolution. It is therefore an important optimisation parameter both in drug discovery but also as guidance for formulation selection and optimisation. Wettability for a compound is determined by its contact angle to a liquid, which in the present study was measured using the sessile drop method applied to a disc compact of the compound. Precise determination of the contact angle is important should it be used to either rank compounds or selected excipients to e.g. increase the wetting from a solid dosage form. Since surface roughness of the compact has been suggested to influence the measurement this study investigated if the surface quality, in terms of surface porosity, had an influence on the measured contact angle. A correlation to surface porosity was observed, however for six out of seven compounds similar results were obtained by applying a standard pressure (866 MPa) to the discs in their preparation. The data presented in the present work therefore suggest that a constant high pressure should be sufficient for most compounds when determining the contact angle. Only for special cases where compounds have poor compressibility would there be a need for a surface-quality-control step before the contact angle determination. Copyright © 2015 Elsevier B.V. All rights reserved.
A 'conveyor belt' model for the dynamic contact angle
Energy Technology Data Exchange (ETDEWEB)
Volpe C, Della; Siboni, S, E-mail: stefano.siboni@ing.unitn.it [Department of Materials Engineering and Industrial Technologies, University of Trento, Mesiano di Povo 38050 Povo, Trento (Italy)
2011-07-15
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 detected, and in a repeatable way, are advancing and receding contact angles. In this paper, we discuss a simple model which accounts for the onset of advancing and receding contact angles measured by the Wilhelmy microbalance, one of the most powerful techniques for contact angle measurements. The model also explains the experimental observation that advancing and receding contact angles become closer to each other when the system is gently 'shaken', by supplying mechanical energy in an appropriate way. The model may be pedagogically useful in introducing students and teachers to aspects of capillary phenomena which are not usually discussed in basic physics courses.
Molecular Dynamics Analyses on Microscopic Contact Angle - Effect of Wall Atom Configuration
International Nuclear Information System (INIS)
Takahiro Ito; Yosuke Hirata; Yutaka Kukita
2006-01-01
Boiling or condensing phenomena of liquid on the solid surface is greatly affected by the wetting condition of the liquid to the solid. Although the contact angle is one of the most important parameter to represent the wetting condition, the behavior of the contact angle is not understood well, especially in the dynamic condition. In this study we made molecular dynamics simulations to investigate the microscopic contact angle behavior under several conditions on the numerical density of the wall atoms. In the analyses, when the number density of the wall is lower, the changing rate of the dynamics contact angles for the variation of ΔV was higher than those for the case where the wall density is higher. This is mainly due to the crystallization of the fluid near the wall and subsequent decrease in the slip between the fluid and the wall. The analyses also show that the static contact angle decreases with increase in the number density of the wall. This was mainly induced by the increase in the number density of the wall itself. (authors)
Smoothed particle hydrodynamics study of the roughness effect on contact angle and droplet flow.
Shigorina, Elena; Kordilla, Jannes; Tartakovsky, Alexandre M
2017-09-01
We employ a pairwise force smoothed particle hydrodynamics (PF-SPH) model to simulate sessile and transient droplets on rough hydrophobic and hydrophilic surfaces. PF-SPH allows modeling of free-surface flows without discretizing the air phase, which is achieved by imposing the surface tension and dynamic contact angles with pairwise interaction forces. We use the PF-SPH model to study the effect of surface roughness and microscopic contact angle on the effective contact angle and droplet dynamics. In the first part of this work, we investigate static contact angles of sessile droplets on different types of rough surfaces. We find that the effective static contact angles of Cassie and Wenzel droplets on a rough surface are greater than the corresponding microscale static contact angles. As a result, microscale hydrophobic rough surfaces also show effective hydrophobic behavior. On the other hand, microscale hydrophilic surfaces may be macroscopically hydrophilic or hydrophobic, depending on the type of roughness. We study the dependence of the transition between Cassie and Wenzel states on roughness and droplet size, which can be linked to the critical pressure for the given fluid-substrate combination. We observe good agreement between simulations and theoretical predictions. Finally, we study the impact of the roughness orientation (i.e., an anisotropic roughness) and surface inclination on droplet flow velocities. Simulations show that droplet flow velocities are lower if the surface roughness is oriented perpendicular to the flow direction. If the predominant elements of surface roughness are in alignment with the flow direction, the flow velocities increase compared to smooth surfaces, which can be attributed to the decrease in fluid-solid contact area similar to the lotus effect. We demonstrate that classical linear scaling relationships between Bond and capillary numbers for droplet flow on flat surfaces also hold for flow on rough surfaces.
Analysis of Wetting and Contact Angle Hysteresis on Chemically Patterned Surfaces
Xu, Xianmin; Wang, Xiaoping
2011-01-01
Wetting and contact angle hysteresis on chemically patterned surfaces in two dimensionsare analyzed from a stationary phase-field model for immiscible two phase fluids. We first study the sharp-interface limit of the model by the method of matched asymptotic expansions. We then justify the results rigorously by the γ-convergence theory for the related variational problem and study the properties of the limiting minimizers. The results also provide a clear geometric picture of the equilibrium configuration of the interface. This enables us to explicitly calculate the total surface energy for the two phase systems on chemically patterned surfaces with simple geometries, namely the two phase flow in a channel and the drop spreading. By considering the quasi-staticmotion of the interface described by the change of volume (or volume fraction), we can follow the change-of-energy landscape which also reveals the mechanism for the stick-slip motion of the interface and contact angle hysteresis on the chemically patterned surfaces. As the interface passes throughpatterned surfaces, we observe not only stick-slip of the interface and switching of the contact angles but also the hysteresis of contact point and contact angle. Furthermore, as the size of the patternde creases to zero, the stick-slip becomes weaker but the hysteresis becomes stronger in the sense that one observes either the advancing contact angle or the receding contact angle (when the interface ismoving in the opposite direction) without the switching in between. © 2011 Society for Industrial and Applied Mathematics.
Kuchin, I; Starov, V
2015-05-19
A theory of contact angle hysteresis of liquid droplets on smooth, homogeneous solid substrates is developed in terms of the shape of the disjoining/conjoining pressure isotherm and quasi-equilibrium phenomena. It is shown that all contact angles, θ, in the range θr contact angle θ ≠ θe, correspond to the state of slow "microscopic" advancing or receding motion of the liquid if θe contact angle reaches the critical values θa or θr, correspondingly. The values of the static receding, θr, and static advancing, θa, contact angles in cylindrical capillaries were calculated earlier, based on the shape of disjoining/conjoining pressure isotherm. It is shown now that (i) both advancing and receding contact angles of a droplet on a on smooth, homogeneous solid substrate can be calculated based on shape of disjoining/conjoining pressure isotherm, and (ii) both advancing and receding contact angles depend on the drop volume and are not unique characteristics of the liquid-solid system. The latter is different from advancing/receding contact angles in thin capillaries. It is shown also that the receding contact angle is much closer to the equilibrium contact angle than the advancing contact angle. The latter conclusion is unexpected and is in a contradiction with the commonly accepted view that the advancing contact angle can be taken as the first approximation for the equilibrium contact angle. The dependency of hysteresis contact angles on the drop volume has a direct experimental confirmation.
Contact Stress Analysis for Gears of Different Helix Angle Using Finite Element Method
Directory of Open Access Journals (Sweden)
Patil Santosh
2014-07-01
Full Text Available The gear contact stress problem has been a great point of interest for many years, but still an extensive research is required to understand the various parameters affecting this stress. Among such parameters, helix angle is one which has played a crucial role in variation of contact stress. Numerous studies have been carried out on spur gear for contact stress variation. Hence, the present work is an attempt to study the contact stresses among the helical gear pairs, under static conditions, by using a 3D finite element method. The helical gear pairs on which the analysis is carried are 0, 5, 15, 25 degree helical gear sets. The Lagrange multiplier algorithm has been used between the contacting pairs to determine the stresses. The helical gear contact stress is evaluated using FE model and results have also been found at different coefficient of friction, varying from 0.0 to 0.3. The FE results have been further compared with the analytical calculations. The analytical calculations are based upon Hertz and AGMA equations, which are modified to include helix angle. The commercial finite element software was used in the study and it was shown that this approach can be applied to gear design efficiently. The contact stress results have shown a decreasing trend, with increase in helix angle.
Requejo, Philip Santos; Mulroy, Sara J; Ruparel, Puja; Hatchett, Patricia E; Haubert, Lisa Lighthall; Eberly, Valerie J; Gronley, JoAnne K
2015-01-01
Shoulder loading during manual wheelchair propulsion (WCP) contributes to the development of shoulder pain in individuals with spinal cord injury (SCI). 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. 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). Increased push arc (mean = 75.3°) was associated with greater velocity (R = 0.384, P 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 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 contact and hand release must be considered in WCP training. It is recommended that participants should reach back to initiate contact with the pushrim to maximize push arc but avoid a more anterior hand position at release, because this could increase shoulder load during the push phase of WCP.
International Nuclear Information System (INIS)
Seo, Kwangseok; Kim, Minyoung; Kim, Do Hyun; Ahn, Jeong Keun
2015-01-01
It is not a simple task to measure a contact angle of a water drop on a superhydrophobic surface with sessile drop method, because a roll-off angle is very low. Usually contact angle of a water drop on a superhydrophobic surface is measured by fixing a drop with intentional defects on the surface or a needle. We examined the effects of drop size and measuring condition such as the use of a needle or defects on the static contact angle measurement on superhydrophobic surface. Results showed that the contact angles on a superhydrophobic surface remain almost constant within intrinsic measurement errors unless there is a wetting transition during the measurement. We expect that this study will provide a deeper understanding on the nature of the contact angle and convenient measurement of the contact angle on the superhydrophobic surface.
Statistical contact angle analyses; "slow moving" drops on a horizontal silicon-oxide surface.
Schmitt, M; Grub, J; Heib, F
2015-06-01
Sessile drop experiments on horizontal surfaces are commonly used to characterise surface properties in science and in industry. The advancing angle and the receding angle are measurable on every solid. Specially on horizontal surfaces even the notions themselves are critically questioned by some authors. Building a standard, reproducible and valid method of measuring and defining specific (advancing/receding) contact angles is an important challenge of surface science. Recently we have developed two/three approaches, by sigmoid fitting, by independent and by dependent statistical analyses, which are practicable for the determination of specific angles/slopes if inclining the sample surface. These approaches lead to contact angle data which are independent on "user-skills" and subjectivity of the operator which is also of urgent need to evaluate dynamic measurements of contact angles. We will show in this contribution that the slightly modified procedures are also applicable to find specific angles for experiments on horizontal surfaces. As an example droplets on a flat freshly cleaned silicon-oxide surface (wafer) are dynamically measured by sessile drop technique while the volume of the liquid is increased/decreased. The triple points, the time, the contact angles during the advancing and the receding of the drop obtained by high-precision drop shape analysis are statistically analysed. As stated in the previous contribution the procedure is called "slow movement" analysis due to the small covered distance and the dominance of data points with low velocity. Even smallest variations in velocity such as the minimal advancing motion during the withdrawing of the liquid are identifiable which confirms the flatness and the chemical homogeneity of the sample surface and the high sensitivity of the presented approaches. Copyright © 2014 Elsevier Inc. All rights reserved.
A study on the contact angles of a water droplet on smooth and rough solid surfaces
International Nuclear Information System (INIS)
Park, Ju Young; Ha, Man Yeong; Choi, Ho Jin; Hong, Seung Do; Yoon, Hyun Sik
2011-01-01
We investigated the wetting characteristics such as contact angle, wetting radius and topography of water droplets on smooth and random solid surfaces. Molecular dynamic simulation is employed to analyze the wetting behavior of water droplets on smooth and rough surfaces by considering different potential energy models of bond, angle, Lennard-Jones and Coulomb to calculate the interacting forces between water molecules. The Lennard-Jones potential energy model is adopted as an interaction model between water molecules and solid surface atoms. The randomly rough surface is generated by changing the standard deviation of roughness height from 1 A to 3 A with the fixed autocorrelation length. The size of water droplet considered is in the range from 2,000 to 5,000 molecules. The contact angles increase generally with increasing number of water molecules. For a hydrophobic surface whose characteristic energy is 0.1 kcal/mol, the contact angles depend rarely on the standard deviation of the roughness height. However, when the surface energy is 0.5 and 1.0 kcal/mol, the contact angles depend on both the roughness height of surfaces and droplet size
A modified captive bubble method for determining advancing and receding contact angles
International Nuclear Information System (INIS)
Xue, Jian; Shi, Pan; Zhu, Lin; Ding, Jianfu; Chen, Qingmin; Wang, Qingjun
2014-01-01
Graphical abstract: - Highlights: • A modified captive bubble method for determining advancing and receding contact angle is proposed. • We have designed a pressure chamber with a pressure control system to the original experimental. • The modified method overcomes the deviation of the bubble in the traditional captive bubble method. • The modified captive bubble method allows a smaller error from the test. - Abstract: In this work, a modification to the captive bubble method was proposed to test the advancing and receding contact angle. This modification is done by adding a pressure chamber with a pressure control system to the original experimental system equipped with an optical angle mater equipped with a high speed CCD camera, a temperature control system and a computer. A series of samples with highly hydrophilic, hydrophilic, hydrophobic and superhydrophobic surfaces were prepared. The advancing and receding contact angles of these samples with highly hydrophilic, hydrophilic, and hydrophobic surfaces through the new methods was comparable to the result tested by the traditional sessile drop method. It is proved that this method overcomes the limitation of the traditional captive bubble method and the modified captive bubble method allows a smaller error from the test. However, due to the nature of the captive bubble technique, this method is also only suitable for testing the surface with advancing or receding contact angle below 130°
A modified captive bubble method for determining advancing and receding contact angles
Energy Technology Data Exchange (ETDEWEB)
Xue, Jian; Shi, Pan; Zhu, Lin [Key Laboratory of High Performance Polymer Materials and Technology (Nanjing University), Ministry of Eduction, Nanjing 210093 (China); Ding, Jianfu [Security and Disruptive Technologies, National Research Council Canada, 1200 Montreal Road, Ottawa, K1A 0R6, Ontario (Canada); Chen, Qingmin [Key Laboratory of High Performance Polymer Materials and Technology (Nanjing University), Ministry of Eduction, Nanjing 210093 (China); Wang, Qingjun, E-mail: njuwqj@nju.edu.cn [Key Laboratory of High Performance Polymer Materials and Technology (Nanjing University), Ministry of Eduction, Nanjing 210093 (China)
2014-03-01
Graphical abstract: - Highlights: • A modified captive bubble method for determining advancing and receding contact angle is proposed. • We have designed a pressure chamber with a pressure control system to the original experimental. • The modified method overcomes the deviation of the bubble in the traditional captive bubble method. • The modified captive bubble method allows a smaller error from the test. - Abstract: In this work, a modification to the captive bubble method was proposed to test the advancing and receding contact angle. This modification is done by adding a pressure chamber with a pressure control system to the original experimental system equipped with an optical angle mater equipped with a high speed CCD camera, a temperature control system and a computer. A series of samples with highly hydrophilic, hydrophilic, hydrophobic and superhydrophobic surfaces were prepared. The advancing and receding contact angles of these samples with highly hydrophilic, hydrophilic, and hydrophobic surfaces through the new methods was comparable to the result tested by the traditional sessile drop method. It is proved that this method overcomes the limitation of the traditional captive bubble method and the modified captive bubble method allows a smaller error from the test. However, due to the nature of the captive bubble technique, this method is also only suitable for testing the surface with advancing or receding contact angle below 130°.
On the equilibrium contact angle of sessile liquid drops from molecular dynamics simulations.
Ravipati, Srikanth; Aymard, Benjamin; Kalliadasis, Serafim; Galindo, Amparo
2018-04-28
We present a new methodology to estimate the contact angles of sessile drops from molecular simulations by using the Gaussian convolution method of Willard and Chandler [J. Phys. Chem. B 114, 1954-1958 (2010)] to calculate the coarse-grained density from atomic coordinates. The iso-density contour with average coarse-grained density value equal to half of the bulk liquid density is identified as the average liquid-vapor (LV) interface. Angles between the unit normal vectors to the average LV interface and unit normal vector to the solid surface, as a function of the distance normal to the solid surface, are calculated. The cosines of these angles are extrapolated to the three-phase contact line to estimate the sessile drop contact angle. The proposed methodology, which is relatively easy to implement, is systematically applied to three systems: (i) a Lennard-Jones (LJ) drop on a featureless LJ 9-3 surface; (ii) an SPC/E water drop on a featureless LJ 9-3 surface; and (iii) an SPC/E water drop on a graphite surface. The sessile drop contact angles estimated with our methodology for the first two systems are shown to be in good agreement with the angles predicted from Young's equation. The interfacial tensions required for this equation are computed by employing the test-area perturbation method for the corresponding planar interfaces. Our findings suggest that the widely adopted spherical-cap approximation should be used with caution, as it could take a long time for a sessile drop to relax to a spherical shape, of the order of 100 ns, especially for water molecules initiated in a lattice configuration on a solid surface. But even though a water drop can take a long time to reach the spherical shape, we find that the contact angle is well established much faster and the drop evolves toward the spherical shape following a constant-contact-angle relaxation dynamics. Making use of this observation, our methodology allows a good estimation of the sessile drop contact
Spontaneous Spreading of a Droplet: The Role of Solid Continuity and Advancing Contact Angle.
Jiang, Youhua; Sun, Yujin; Drelich, Jaroslaw W; Choi, Chang-Hwan
2018-05-01
Spontaneous spreading of a droplet on a solid surface is poorly understood from a macroscopic level down to a molecular level. Here, we investigate the effect of surface topography and wettability on spontaneous spreading of a water droplet. Spreading force is measured for a suspended droplet that minimizes interference of kinetic energy in the spontaneous spreading during its contact with solid surfaces of discontinuous (pillar) and continuous (pore) patterns with various shapes and dimensions. Results show that a droplet cannot spread spontaneously on pillared surfaces regardless of their shapes or dimensions because of the solid discontinuity. On the contrary, a droplet on pored surfaces can undergo spontaneous spreading whose force increases with a decrease in the advancing contact angle. Theoretical models based on both the system free energy and capillary force along the contact line validate the direct and universal dependency of the spontaneous spreading force on the advancing contact angle.
Oil Contact Angles in a Water-Decane-Silicon Dioxide System: Effects of Surface Charge.
Xu, Shijing; Wang, Jingyao; Wu, Jiazhong; Liu, Qingjie; Sun, Chengzhen; Bai, Bofeng
2018-04-19
Oil wettability in the water-oil-rock systems is very sensitive to the evolution of surface charges on the rock surfaces induced by the adsorption of ions and other chemical agents in water flooding. Through a set of large-scale molecular dynamics simulations, we reveal the effects of surface charge on the oil contact angles in an ideal water-decane-silicon dioxide system. The results show that the contact angles of oil nano-droplets have a great dependence on the surface charges. As the surface charge density exceeds a critical value of 0.992 e/nm 2 , the contact angle reaches up to 78.8° and the water-wet state is very apparent. The variation of contact angles can be confirmed from the number density distributions of oil molecules. With increasing the surface charge density, the adsorption of oil molecules weakens and the contact areas between nano-droplets and silicon dioxide surface are reduced. In addition, the number density distributions, RDF distributions, and molecular orientations indicate that the oil molecules are adsorbed on the silicon dioxide surface layer-by-layer with an orientation parallel to the surface. However, the layered structure of oil molecules near the silicon dioxide surface becomes more and more obscure at higher surface charge densities.
Liquid-bridge stability and breakup on surfaces with contact-angle hysteresis.
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.
Dong, Jian; Jin, Yanli; Dong, He; Liu, Jiawei; Ye, Senbin
2018-06-14
The profile, apparent contact angle (ACA), contact angle hysteresis (CAH) and wetting state transmission energy barrier (WSTEB) are important static and dynamic properties of a large volume droplet on the hierarchical surface. Understanding them can provide us with important insights to functional surfaces and promote the application in corresponding areas. In this paper, we established three theoretical models (Model 1, Model 2 and Model 3) and corresponding numerical methods, which were obtained by the free energy minimization and the nonlinear optimization algorithm, to predict the profile, ACA, CAH and WSTEB of a large volume droplet on the horizontal regular dual-rough surface. In consideration of the gravity, the energy barrier on the contact circle, the dual heterogenous structures and their roughness on the surface, the models are more universal and accurate than previous models. It showed that the predictions of the models were in good agreement with the results from the experiment or literature. The models are promising to become novel design approaches of functional surfaces, which are frequently applied in microfluidic chips, water self-catchment system and dropwise condensation heat transfer system.
Effect of Ankle Joint Contact Angle and Ground Contact Time on Depth Jump Performance.
Phillips, Joshua H; Flanagan, Sean P
2015-11-01
Athletes often need to both jump high and get off the ground quickly, but getting off the ground quickly can decrease the vertical ground reaction force (VGRF) impulse, impeding jump height. Energy stored in the muscle-tendon complex during the stretch-shortening cycle (SSC) may mitigate the effects of short ground contact times (GCTs). To take advantage of the SSC, several coaches recommend "attacking" the ground with the foot in a dorsiflexed (DF) position at contact. However, the efficacy of this technique has not been tested. This investigation tested the hypotheses that shorter GCTs would lead to smaller vertical depth jump heights (VDJH), and that this difference could be mitigated by instructing the athletes to land in a DF as opposed to a plantar flexed (PF) foot position. Eighteen healthy junior college athletes performed depth jumps from a 45-cm box onto force platforms under instruction to achieve one of the 2 objectives (maximum jump height [hmax] or minimal GCT [tmin]), with one of the 2 foot conditions (DF or PF). These variations created 4 distinct jump conditions: DF-hmax, DF-tmin, PF-hmax, and PF-tmin. For all variables examined, there were no significant interactions. For all 4 conditions, the ankle was PF during landing, but the DF condition was 28.87% less PF than the PF condition. The tmin conditions had a 23.48% shorter GCT than hmax. There were no significant main effects for jump height. The peak impact force for tmin was 22.14% greater than hmax and 19.11% greater for DF compared with PF conditions. A shorter GCT did not necessitate a smaller jump height, and a less PF foot did not lead to improvements in jump height or contact time during a depth jump from a 45-cm box. The same jump height was attained in less PF and shorter GCT conditions by larger impact forces. To decrease contact time while maintaining jump height, athletes should be instructed to "get off the ground as fast as possible." This cue seems to be more important than foot
Chen, Szu-Ying; Kaufman, Yair; Schrader, Alex M; Seo, Dongjin; Lee, Dong Woog; Page, Steven H; Koenig, Peter H; Isaacs, Sandra; Gizaw, Yonas; Israelachvili, Jacob N
2017-09-26
Measuring truly equilibrium adhesion energies or contact angles to obtain the thermodynamic values is experimentally difficult because it requires loading/unloading or advancing/receding boundaries to be measured at rates that can be slower than 1 nm/s. We have measured advancing-receding contact angles and loading-unloading adhesion energies for various systems and geometries involving molecularly smooth and chemically homogeneous surfaces moving at different but steady velocities in both directions, ±V, focusing on the thermodynamic limit of ±V → 0. We have used the Bell Theory (1978) to derive expressions for the dynamic (velocity-dependent) adhesion energies and contact angles suitable for both (i) dynamic adhesion measurements using the classic Johnson-Kendall-Roberts (JKR, 1971) theory of "contact mechanics" and (ii) dynamic contact angle hysteresis measurements of both rolling droplets and syringe-controlled (sessile) droplets on various surfaces. We present our results for systems that exhibited both steady and varying velocities from V ≈ 10 mm/s to 1 nm/s, where in all cases but one, the advancing (V > 0) and receding (V contact angles converged toward the same theoretical (thermodynamic) values as V → 0. Our equations for the dynamic contact angles are similar to the classic equations of Blake & Haynes (1969) and fitted the experimental adhesion data equally well over the range of velocities studied, although with somewhat different fitting parameters for the characteristic molecular length/dimension or area and characteristic bond formation/rupture lifetime or velocity. Our theoretical and experimental methods and results unify previous kinetic theories of adhesion and contact angle hysteresis and offer new experimental methods for testing kinetic models in the thermodynamic, quasi-static, limit. Our analyses are limited to kinetic effects only, and we conclude that hydrodynamic, i.e., viscous, and inertial effects do not play a role at the
Complex Contact Angles Calculated from Capillary Rise Measurements on Rock Fracture Faces
Perfect, E.; Gates, C. H.; Brabazon, J. W.; Santodonato, L. J.; Dhiman, I.; Bilheux, H.; Bilheux, J. C.; Lokitz, B. S.
2017-12-01
Contact angles for fluids in unconventional reservoir rocks are needed for modeling hydraulic fracturing leakoff and subsequent oil and gas extraction. Contact angle measurements for wetting fluids on rocks are normally performed using polished flat surfaces. However, such prepared surfaces are not representative of natural rock fracture faces, which have been shown to be rough over multiple scales. We applied a variant of the Wilhelmy plate method for determining contact angle from the height of capillary rise on a vertical surface to the wetting of rock fracture faces by water in the presence of air. Cylindrical core samples (5.05 cm long x 2.54 cm diameter) of Mancos shale and 6 other rock types were investigated. Mode I fractures were created within the cores using the Brazilian method. Each fractured core was then separated into halves exposing the fracture faces. One fracture face from each rock type was oriented parallel to a collimated neutron beam in the CG-1D imaging instrument at ORNL's High Flux Isotope Reactor. Neutron radiography was performed using the multi-channel plate detector with a spatial resolution of 50 μm. Images were acquired every 60 s after a water reservoir contacted the base of the fracture face. The images were normalized to the initial dry condition so that the upward movement of water on the fracture face was clearly visible. The height of wetting at equilibrium was measured on the normalized images using ImageJ. Contact angles were also measured on polished flat surfaces using the conventional sessile drop method. Equilibrium capillary rise on the exposed fracture faces was up to 8.5 times greater than that predicted for polished flat surfaces from the sessile drop measurements. These results indicate that rock fracture faces are hyperhydrophilic (i.e., the height of capillary rise is greater than that predicted for a contact angle of zero degrees). The use of complex numbers permitted calculation of imaginary contact angles for
New Method Developed to Measure Contact Angles of a Sessile Drop
Chao, David F.; Zhang, Nengli
2002-01-01
The spreading of an evaporating liquid on a solid surface occurs in many practical processes and is of importance in a number of practical situations such as painting, textile dyeing, coating, gluing, and thermal engineering. Typical processes involving heat transfer where the contact angle plays an important role are film cooling, boiling, and the heat transfer through heat pipes. The biological phenomenon of cell spreading also is analogous to a drop spreading (ref. 1). In the study of spreading, the dynamic contact angle describes the interfacial properties on solid substrates and, therefore, has been studied by physicists and fluid mechanics investigators. The dynamic contact angle of a spreading nonvolatile liquid drop provides a simple tool in the study of the free-boundary problem, but the study of the spreading of a volatile liquid drop is of more practical interest because the evaporation of common liquids is inevitable in practical processes. The most common method to measure the contact angle, the contact radius, and the height of a sessile drop on a solid surface is to view the drop from its edge through an optical microscope. However, this method gives only local information in the view direction. Zhang and Yang (ref. 2) developed a laser shadowgraphy method to investigate the evaporation of sessile drop on a glass plate. As described here, Zhang and Chao (refs. 3 and 4) improved the method and suggested a new optical arrangement to measure the dynamic contact angle and the instant evaporation rate of a sessile drop with much higher accuracy (less than 1 percent). With this method, any fluid motion in the evaporating drop can be visualized through shadowgraphy without using a tracer, which often affects the field under investigation.
Contact angle and detachment energy of shape anisotropic particles at fluid-fluid interfaces.
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. Copyright © 2016 Elsevier Inc. All rights reserved.
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.
A Langevin model for fluctuating contact angle behaviour parametrised using molecular dynamics.
Smith, E R; Müller, E A; Craster, R V; Matar, O K
2016-12-06
Molecular dynamics simulations are employed to develop a theoretical model to predict the fluid-solid contact angle as a function of wall-sliding speed incorporating thermal fluctuations. A liquid bridge between counter-sliding walls is studied, with liquid-vapour interface-tracking, to explore the impact of wall-sliding speed on contact angle. The behaviour of the macroscopic contact angle varies linearly over a range of capillary numbers beyond which the liquid bridge pinches off, a behaviour supported by experimental results. Nonetheless, the liquid bridge provides an ideal test case to study molecular scale thermal fluctuations, which are shown to be well described by Gaussian distributions. A Langevin model for contact angle is parametrised to incorporate the mean, fluctuation and auto-correlations over a range of sliding speeds and temperatures. The resulting equations can be used as a proxy for the fully-detailed molecular dynamics simulation allowing them to be integrated within a continuum-scale solver.
On canonical cylinder sections for accurate determination of contact angle in microgravity
Concus, Paul; Finn, Robert; Zabihi, Farhad
1992-01-01
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.
Effect of the meniscus contact angle during early regimes of spontaneous imbibition in nanochannels.
Karna, Nabin Kumar; Oyarzua, Elton; Walther, Jens H; Zambrano, Harvey A
2016-11-30
Nanoscale capillarity has been extensively investigated; nevertheless, many fundamental questions remain open. In spontaneous imbibition, the classical Lucas-Washburn equation predicts a singularity as the fluid enters the channel consisting of an anomalous infinite velocity of the capillary meniscus. Bosanquet's equation overcomes this problem by taking into account fluid inertia predicting an initial imbibition regime with constant velocity. Nevertheless, the initial constant velocity as predicted by Bosanquet's equation is much greater than those observed experimentally. In the present study, large scale atomistic simulations are conducted to investigate capillary imbibition of water in slit silica nanochannels with heights between 4 and 18 nm. We find that the meniscus contact angle remains constant during the inertial regime and its value depends on the height of the channel. We also find that the meniscus velocity computed at the channel entrance is related to the particular value of the meniscus contact angle. Moreover, during the subsequent visco-inertial regime, as the influence of viscosity increases, the meniscus contact angle is found to be time dependent for all the channels under study. Furthermore, we propose an expression for the time evolution of the dynamic contact angle in nanochannels which, when incorporated into Bosanquet's equation, satisfactorily explains the initial capillary rise.
Time-related contact angle measurements with human plasma on biomaterial surfaces
Rakhorst, G; Van der Mei, HC; van Oeveren, W; Spijker, HT; Busscher, HJ
Axisymmetric drop shape analysis by profile (ADSA-P) was used to assess in time contact angle changes of human plasma drops placed on four different biomaterials. Results were related with conventional blood compatibility measurements: albumin adsorption, fibrinogen adsorption and platelet adhesion.
Walz, Jenna A; Mace, Charles R
2018-06-05
Immunophenotyping is typically achieved using flow cytometry, but any influence a biomarker may have on adhesion or surface recognition cannot be determined concurrently. In this manuscript, we demonstrate the utility of lateral microscopy for correlating cell surface biomarker expression levels with quantitative descriptions of cell morphology. With our imaging system, we observed single cells from two T cell lines and two B cell lines adhere to antibody-coated substrates and quantified this adhesion using contact angle measurements. We found that SUP-T1 and CEM CD4+ cells, both of which express similar levels of CD4, experienced average changes in contact angle that were not statistically different from one another on surfaces coated in anti-CD4. However, MAVER-1 and BJAB K20 cells, both of which express different levels of CD20, underwent average changes in contact angle that were significantly different from one another on surfaces coated in anti-CD20. Our results indicate that changes in cell contact angles on antibody-coated substrates reflect the expression levels of corresponding antigens on the surfaces of cells as determined by flow cytometry. Our lateral microscopy approach offers a more reproducible and quantitative alternative to evaluate adhesion compared to commonly used wash assays and can be extended to many additional immunophenotyping applications to identify cells of interest within heterogeneous populations.
Contact angle studies on PDMS surfaces fouled by bovine serum albumin
CSIR Research Space (South Africa)
Windvoel, VT
2010-01-01
Full Text Available Polydimethylsiloxane (PDMS) has a hydrophobic surface, forming a contact angle of around 110º with deionised water. It is due to its hydrophobic nature that the elastomer is prone to bio-fouling, such as non-specific adsorption of biomaterials like...
Edge contact angle and modified Kelvin equation for condensation in open pores.
Malijevský, Alexandr; Parry, Andrew O; Pospíšil, Martin
2017-08-01
We consider capillary condensation transitions occurring in open slits of width L and finite height H immersed in a reservoir of vapor. In this case the pressure at which condensation occurs is closer to saturation compared to that occurring in an infinite slit (H=∞) due to the presence of two menisci that are pinned near the open ends. Using macroscopic arguments, we derive a modified Kelvin equation for the pressure p_{cc}(L;H) at which condensation occurs and show that the two menisci are characterized by an edge contact angle θ_{e} that is always larger than the equilibrium contact angle θ, only equal to it in the limit of macroscopic H. For walls that are completely wet (θ=0) the edge contact angle depends only on the aspect ratio of the capillary and is well described by θ_{e}≈sqrt[πL/2H] for large H. Similar results apply for condensation in cylindrical pores of finite length. We test these predictions against numerical results obtained using a microscopic density-functional model where the presence of an edge contact angle characterizing the shape of the menisci is clearly visible from the density profiles. Below the wetting temperature T_{w} we find very good agreement for slit pores of widths of just a few tens of molecular diameters, while above T_{w} the modified Kelvin equation only becomes accurate for much larger systems.
Contact angles in thin liquid films III. Interaction forces in Newton black soap films
Feijter, J.A. de; Vrij, A.
The interaction parameters of Newton black soap films stabilized by NaDS, as derived from contact angle experiments, have been interpretated in terms of the structure and the interaction forces in the films. From the film thickness and the difference between the surface excess of the salt in the
Khulbe, K.C.; Feng, C.; Matsuura, T.; Kapantaidakis, G.; Wessling, Matthias; Koops, G.H.
2003-01-01
Asymmetric blend polyethersulfone-polyimide (PES-PI) hollow fiber membranes prepared at different air gap and used for gas separation are characterized by atomic force microscopy (inside and out side surfaces) and by measuring the contact angle of out side surface. The outer surface was entirely
Edge contact angle and modified Kelvin equation for condensation in open pores
Malijevský, Alexandr; Parry, Andrew O.; Pospíšil, Martin
2017-08-01
We consider capillary condensation transitions occurring in open slits of width L and finite height H immersed in a reservoir of vapor. In this case the pressure at which condensation occurs is closer to saturation compared to that occurring in an infinite slit (H =∞ ) due to the presence of two menisci that are pinned near the open ends. Using macroscopic arguments, we derive a modified Kelvin equation for the pressure pc c(L ;H ) at which condensation occurs and show that the two menisci are characterized by an edge contact angle θe that is always larger than the equilibrium contact angle θ , only equal to it in the limit of macroscopic H . For walls that are completely wet (θ =0 ) the edge contact angle depends only on the aspect ratio of the capillary and is well described by θe≈√{π L /2 H } for large H . Similar results apply for condensation in cylindrical pores of finite length. We test these predictions against numerical results obtained using a microscopic density-functional model where the presence of an edge contact angle characterizing the shape of the menisci is clearly visible from the density profiles. Below the wetting temperature Tw we find very good agreement for slit pores of widths of just a few tens of molecular diameters, while above Tw the modified Kelvin equation only becomes accurate for much larger systems.
Experimental Investigation of Coal Dust Wettability Based on Surface Contact Angle
Directory of Open Access Journals (Sweden)
Gang Zhou
2016-01-01
Full Text Available Wettability is one of the key chemical properties of coal dust, which is very important to dedusting. In this paper, the theory of liquid wetting solid was presented firstly; then, taking the gas coal of Xinglongzhuang coal mine in China as an example, by determination of critical surface tension of coal piece, it can be concluded that only when the surface tension of surfactant solution is less than 45 mN/m can the coal sample be fully wetted. Due to the effect of particle dispersity, compared with the contact angle of milled coal particle, not all the contact angles of screened coal powder with different sizes have a tendency to increase. Furthermore, by the experiments of coal samples’ specific surface areas and porosities, it can be achieved that the volume of single-point total pore decreases with the gradual decreasing of coal’s porosity, while the ultramicropores’ dispersities and multipoint BET specific surface areas increase. Besides, by a series of contact angle experiments with different surfactants, it can be found that with the increasing of porosity and the decreasing of volume percentage of ultramicropore, the contact angle tends to reduce gradually and the coal dust is much easier to get wetted.
Directory of Open Access Journals (Sweden)
Katarzyna Boniewicz-Szmyt
2009-09-01
Full Text Available The wetting properties of solid mineral samples (by contact angles in original surfactant-containing sea water (Gulf of Gdańsk, Baltic were characterised under laboratory conditions on a large set (31 samples of well-classified stones of diverse hydrophobicity using the sessile drop (ADSA-P approach, captive bubble and inclined plate methods. An experimental relation between the static contact angle θeq and stone density ρ was obtained in the form θeq = Bρ + C, where B = 12.23 ± 0.92, C = - (19.17 ± 0.77, and r2 = 0.92. The histogram of θeq distribution for polished stone plates exhibited a multimodal feature indicating that the most abundant solid materials (hydrophilic in nature have contact angles θeq = 7.2, 10.7, 15.7 and 19.2º, which appear to be applicable to unspecified field stones as well. The contact angle, a pH-dependent quantity, appears to be a sensitive measure of stone grain size, e.g. granite. The captive bubble method gives reproducible results in studies of porous and highly hydrophilic surfaces such as stones and wood. The authors consider the adsorption of natural sea water surfactants on stone surfaces to be the process responsible for contact angle hysteresis. In the model, an equation was derived for determining the solid surface free energy from the liquid's surface tension γLV it also enabled the advancing θA and receding θR contact angles of this liquid to be calculated. Measurements of contact angle hysteresis Δθ (=θA - θR with surfactant-containing sea water and distilled water (reference on the same stone surfaces allowed the film pressure ΔΠ (1.22 to 8.80 mJ m-2, solid surface free energy ΔγS (-17.03 to -23.61 mJ m-2 and work done by spreading ΔWS (-1.23 to -11.52 mJ m-2 to be determined. The variability in these parameters is attributed to autophobing, an effect operative on a solid surface covered with an adsorptive layer of surfactants. The wetting behaviour of solid particles is of great
DEFF Research Database (Denmark)
Wijewardana, Y. N. S.; Kawamoto, Ken; Komatsu, Toshiko
2014-01-01
) mixed sands representing four different particle size fractions ranging from 0.105 to 0.84 mm. Initial soil-water contact angle (αi), and the time dependence of contact angle were measured by the sessile drop method. Results showed that the αi value for fine and middle sand fractions increased rapidly...... in contact angle (α), well captured the time dependence of α....
Incorporating contact angles in the surface tension force with the ACES interface curvature scheme
Owkes, Mark
2017-11-01
In simulations of gas-liquid flows interacting with solid boundaries, the contact line dynamics effect the interface motion and flow field through the surface tension force. The surface tension force is directly proportional to the interface curvature and the problem of accurately imposing a contact angle must be incorporated into the interface curvature calculation. Many commonly used algorithms to compute interface curvatures (e.g., height function method) require extrapolating the interface, with defined contact angle, into the solid to allow for the calculation of a curvature near a wall. Extrapolating can be an ill-posed problem, especially in three-dimensions or when multiple contact lines are near each other. We have developed an accurate methodology to compute interface curvatures that allows for contact angles to be easily incorporated while avoiding extrapolation and the associated challenges. The method, known as Adjustable Curvature Evaluation Scale (ACES), leverages a least squares fit of a polynomial to points computed on the volume-of-fluid (VOF) representation of the gas-liquid interface. The method is tested by simulating canonical test cases and then applied to simulate the injection and motion of water droplets in a channel (relevant to PEM fuel cells).
Stokes flow inside an evaporating liquid line for any contact angle
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.
Directory of Open Access Journals (Sweden)
Mohammad Jafari
2017-12-01
Full Text Available The pore-level two-phase fluids flow mechanism needs to be understood for geological CO2 sequestration as a solution to mitigate anthropogenic emission of carbon dioxide. Capillary pressure at the interface of water–CO2 influences CO2 injectability, capacity, and safety of the storage system. Wettability usually measured by contact angle is always a major uncertainty source among important parameters affecting capillary pressure. The contact angle is mostly determined on a flat surface as a representative of the rock surface. However, a simple and precise method for determining in situ contact angle at pore-scale is needed to simulate fluids flow in porous media. Recent progresses in X-ray tomography technique has provided a robust way to measure in situ contact angle of rocks. However, slow imaging and complicated image processing make it impossible to measure dynamic contact angle. In the present paper, a series of static and dynamic contact angles as well as contact angles on flat surface were measured inside a micromodel with random pattern of channels under high pressure condition. Our results showed a wide range of pore-scale contact angles, implying complexity of the pore-scale contact angle even in a highly smooth and chemically homogenous glass micromodel. Receding contact angle (RCA showed more reproducibility compared to advancing contact angle (ACA and static contact angle (SCA for repeating tests and during both drainage and imbibition. With decreasing pore size, RCA was increased. The hysteresis of the dynamic contact angle (ACA–RCA was higher at pressure of one megapascal in comparison with that at eight megapascals. The CO2 bubble had higher mobility at higher depths due to lower hysteresis which is unfavorable. CO2 bubbles resting on the flat surface of the micromodel channel showed a wide range of contact angles. They were much higher than reported contact angle values observed with sessile drop or captive bubble tests on a
Contact angles at the water-air interface of hydrocarbon-contaminated soils and clay minerals
Sofinskaya, O. A.; Kosterin, A. V.; Kosterina, E. A.
2016-12-01
Contact angles at the water-air interface have been measured for triturated preparations of clays and soils in order to assess changes in their hydrophobic properties under the effect of oil hydrocarbons. Tasks have been to determine the dynamics of contact angle under soil wetting conditions and to reveal the effect of chemical removal of organic matter from soils on the hydrophilicity of preparations. The potentialities of static and dynamic drop tests for assessing the hydrophilic-hydrophobic properties of soils have been estimated. Clays (kaolinite, gumbrine, and argillite) have been investigated, as well as plow horizons of soils from the Republic of Tatarstan: heavy loamy leached chernozem, medium loamy dark gray forest soil, and light loamy soddy-calcareous soil. The soils have been contaminated with raw oil and kerosene at rates of 0.1-3 wt %. In the uncontaminated and contaminated chernozem, capillary water capacity has been maintained for 250 days. The contact angles have been found to depend on the degree of dispersion of powdered preparation, the main type of clay minerals in the soil, the presence and amount of oxidation-resistant soil organic matter, and the soil-water contact time. Characteristic parameters of mathematical models for drop behavior on triturated preparations have been calculated. Contamination with hydrocarbons has resulted in a reliable increase in the contact angles of soil preparations. The hydrophobization of soil surface in chernozem is more active than in soils poorer in organic matter. The complete restoration of the hydrophilic properties of soils after hydrocarbon contamination is due to the oxidation of easily oxidizable organic matter at the low content of humus, or to wetting during several months in the absence of the mazut fraction.
Effect of contact angle on the orientation, stability, and assembly of dense floating cubes.
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
Contact Angle of Drops Measured on Nontransparent Surfaces and Capillary Flow Visualized
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.
Influence of Contact Angle Boundary Condition on CFD Simulation of T-Junction
Arias, S.; Montlaur, A.
2018-03-01
In this work, we study the influence of the contact angle boundary condition on 3D CFD simulations of the bubble generation process occurring in a capillary T-junction. Numerical simulations have been performed with the commercial Computational Fluid Dynamics solver ANSYS Fluent v15.0.7. Experimental results serve as a reference to validate numerical results for four independent parameters: the bubble generation frequency, volume, velocity and length. CFD simulations accurately reproduce experimental results both from qualitative and quantitative points of view. Numerical results are very sensitive to the gas-liquid-wall contact angle boundary conditions, confirming that this is a fundamental parameter to obtain accurate CFD results for simulations of this kind of problems.
Measurement of contact angle of copper-bearing shales using the captive bubble method
Directory of Open Access Journals (Sweden)
Danuta Szyszka
2014-09-01
Full Text Available This paper describes the measurement of contact angle of the natural surface of copper-bearing shales immersed in solutions of selected reagents of various concentrations using captive bubble method. It demonstrates that the copper-bearing shales coming from Legnicko-Głogwski Copper Region develop natural hydrophobic properties in surfactant (frother solutions and its hydrophobicity decreases from 82⁰ contact angle in distilled water, 78⁰ in C4E1 solutions, 76⁰ in C4E2 solutions, to 75⁰ in dodecylphenol solutions. These data show that the addition of frother causes a decrease of shale hydrophobicity but it can reduce stability of the thin film between the grain and air bubble. It means that flotation of copperbearing shales in the presence of frother will only be possible provided specific concentrations.
A Simple Approach for Local Contact Angle Determination on a Heterogeneous Surface
Wu, Jinbo
2011-05-17
We report a simple approach for measuring the local contact angle of liquids on a heterogeneous surface consisting of intersected hydrophobic and hydrophilic patch arrays, specifically by employing confocal microscopy and the addition of a very low concentration of Rhodamine-B (RB) (2 × 10 -7 mol/L). Interestingly, RB at that concentration was found to be aggregated at the air-liquid and solid (hydrophobic patch only)-liquid interfaces, which helps us to distinguish the liquid and solid interfaces as well as hydrophobic and hydrophilic patches by their corresponding fluorescent intensities. From the measured local contact angles, the line tension can be easily derived and the value is found to be (-2.06-1.53) × 10-6 J/m. © 2011 American Chemical Society.
Contact angle measurements of a polyphenyl ether to 190 C on M-50 steel
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.
Chen, Jianrong; Shen, Liguo; Zhang, Meijia; Hong, Huachang; He, Yiming; Liao, Bao-Qiang; Lin, Hongjun
2016-02-01
Concept of hydrophobicity always fails to accurately assess the interfacial interaction and membrane fouling, which calls for reliable parameters for this purpose. In this study, effects of contact angle on interfacial interactions related to membrane fouling were investigated based on thermodynamic analysis. It was found that, total interaction energy between sludge foulants and membrane monotonically decreases and increases with water and glycerol contact angle, respectively, indicating that these two parameters can be reliable indicators predicting total interaction energy and membrane fouling. Membrane roughness decreases interaction strength for over 20 times, and effects of membrane roughness on membrane fouling should consider water and glycerol contact angle on membrane. It was revealed existence of a critical water and glycerol contact angle for a given membrane bioreactor. Meanwhile, diiodomethane contact angle has minor effect on the total interaction, and cannot be regarded as an effective indicator assessing interfacial interactions and membrane fouling. Copyright © 2015 Elsevier Ltd. All rights reserved.
Changes in contact angle providing evidence for surface alteration in multi-component solid foods
International Nuclear Information System (INIS)
Reinke, Svenja K; Hauf, Katharina; Heinrich, Stefan; Vieira, Josélio; Palzer, Stefan
2015-01-01
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. (paper)
Changes in contact angle providing evidence for surface alteration in multi-component solid foods
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.
Di Mundo, Rosa; Bottiglione, Francesco; Palumbo, Fabio; Notarnicola, Michele; Carbone, Giuseppe
2016-11-15
Micro-scale textured Teflon surfaces, resulting from plasma etching modification, show extremely high water contact angle values and fairly good resistance to water penetration when hit by water drops at medium-high speed. This behavior is more pronounced when these surfaces present denser and smaller micrometric reliefs. Tailoring the top of these reliefs with a structure which further stabilizes the air may further increase resistance to wetting (water penetration) under static and dynamic conditions. Conditions of the oxygen fed plasma were tuned in order to explore the possibility of obtaining differently topped structures on the surface of the polymer. Scanning Electron Microscopy (SEM) was used to explore topography and X-ray Photoelectron Spectroscopy (XPS) to assess chemical similarity of the modified surfaces. Beside the usual advancing and receding water contact angle (WCA) measurements, surfaces were subjected to high speed impacting drops and immersion in water. At milder, i.e. shorter time and lower input power, plasma conditions formation of peculiar filaments is observed on the top of the sculpted reliefs. Filamentary topped surfaces result in a lower WCA than the spherical ones, appearing in this sense less superhydrophobic. However, these surfaces give rise to the formation of a more pronounced air layer when placed underwater. Further, when hit by water drops falling at medium/high speed, they show a higher resistance to water penetration and a sensitively lower surface-liquid contact time. The contact time is as low as previously observed only on heated solids. This behavior may be ascribed to the cavities formed beneath the filaments which, similarly with the salvinia leaf structures, require a surplus of pressure to be filled by water. Also, it suggests a different concept of superhydrophobicity, which cannot be expected on the basis of the conventional water contact angle characterization. Copyright © 2016 Elsevier Inc. All rights reserved.
Liu, Tiaotiao; Hao, Jingqiang; Yang, Baixue; Hu, Beibei; Cui, Zhixiang; Li, Sanming
2018-05-01
The addition of surfactant in tablet was a well-defined approach to improve drug dissolution rate. While the selected surfactant played a vital role in improving the wettability of tablet by medium, it was equally important to improve the dissolution rate by permeation effect due to production of pores or the reduced inter-particle adhesion. Furthermore, understanding the mechanism of dissolution rate increased was significant. In this work, contact angle measurement was taken up as an alternative approach for understanding the dissolution rate enhancement for tablet containing surfactant. Ethylcellulose, as a substrate, was used to prepare tablet. Four surfactants, sodium dodecyl sulfate (SDS), sodium dodecylbenzenesulfonate (SDBS), dodecyltrimethylammonium bromide (DTAB), and sodium lauryl sulfonate (SLS), were used. Berberine hydrochloride, metformin hydrochloride, and rutin were selected as model drugs. The contact angle of tablet in the absence and presence of surfactant was measured to explore the mechanism. The dissolution test was investigated to verify the mechanism and to establish a correlation with the contact angle. The result showed that the mechanism was the penetration effect rather than the wetting effect. The dissolution increased with a reduction in the contact angle. DTAB was found to obtain the highest level of dissolution enhancement and the lowest contact angle, while SDS, SDBS, and SLS were found to be the less effective in both dissolution enhancement and contact angle decrease. Therefore, contact angle was a good indicator for dissolution behavior besides exploring the mechanism of increased dissolution, which shows great potential in formula screening.
Evaporation-induced flow in an inviscid liquid line at any contact angle
Petsi, A. J.; Burganos, V. N.
2006-04-01
The problem of potential flow inside an evaporating liquid line, shaped as an infinitely long cylindrical segment lying on a flat surface, is considered and an analytical solution is obtained for any contact angle in (0,π) . In this way, microflow details inside linear liquid bodies evaporating on hydrophilic, hydrophobic, and strongly hydrophobic substrates can now be obtained. The mathematical formulation employs the velocity potential and stream function formulations in bipolar coordinates and the solution is obtained using the technique of Fourier transform. Both pinned and depinned contact lines are considered. The solution is applicable to any evaporation mechanism but for illustration purposes numerical results are presented here for the particular case of kinetically controlled evaporation. For hydrophilic substrates, the flow inside the evaporating liquid line is directed towards the edges for pinned contact lines, thus, promoting a coffee stain effect. The opposite flow direction is observed for depinned contact lines. However, for strongly hydrophobic substrates, flow is directed outwards for both pinned and depinned contact lines, but owing to its low magnitude compared to that on hydrophilic substrates, a craterlike colloidal deposit should be expected rather than a ringlike deposit, in agreement with experimental observations.
In Situ Local Contact Angle Measurement in a CO2-Brine-Sand System Using Microfocused X-ray CT.
Lv, Pengfei; Liu, Yu; Wang, Zhe; Liu, Shuyang; Jiang, Lanlan; Chen, Junlin; Song, Yongchen
2017-04-11
The wettability of porous media is of major interest in a broad range of natural and engineering applications. The wettability of a fluid on a solid surface is usually evaluated by the contact angle between them. While in situ local contact angle measurements are complicated by the topology of porous media, which can make it difficult to use traditional methods, recent advances in microfocused X-ray computed tomography (micro-CT) and image processing techniques have made it possible to measure contact angles on the scale of the pore sizes in such media. However, the effects of ionic strength, CO 2 phase, and flow pattern (drainage or imbibition) on pore-scale contact angle distribution are still not clear and have not been reported in detail in previous studies. In this study, we employed a micro-CT scanner for in situ investigation of local contact angles in a CO 2 -brine-sand system under various conditions. The effects of ionic strength, CO 2 phase, and flow pattern on the local contact-angle distribution were examined in detail. The results showed that the local contact angles vary over a wide range as a result of the interaction of surface contaminants, roughness, pore topology, and capillarity. The wettability of a porous surface could thus slowly weaken with increasing ionic strength, and the average contact angle could significantly increase when gaseous CO 2 (gCO 2 ) turns into supercritical CO 2 (scCO 2 ). Contact angle hysteresis also occurred between drainage and imbibition procedures, and the hysteresis was more significant under gCO 2 condition.
A fiber-optic technique for the measurement of contact angle in a clearance-fit pin-loaded hole
Prabhakaran, R.; Naik, R. A.
1987-01-01
A fiber-optic technique for measuring contact angle during pin loading of a specimen is proposed. The experimental design and procedures for loading a 49.8-mm-diameter instrumented pin into an quasi-isotropic graphite-epoxy specimen are described. The optical fiber was located just above the surface of the pin outer diameter in order to obtain accurate pin-hole contact-angle measurements at increasing load levels. The movement of the optical fiber through the no-contact, contact, and no-contact regions is discussed; the photodiode output decreased monotonically as the fiber moved from the no-contact to the contact region and then decreased monotonically as the fiber moved from the contact region to the no-contact region. Variations in the contact angle measurements are examined as function of applied load level. The measurements are compared to contact angle values obtained using a finite element analysis and an electrical technique; it is determined that the data correlate well.
Domínguez, Noemí; Castilla, Pau; Linzoain, María Eugenia; Durand, Géraldine; García, Cristina; Arasa, Josep
2018-04-01
This work presents the validation study of a method developed to measure contact angles with a confocal device in a set of hydrophobic samples. The use of this device allows the evaluation of the roughness of the surface and the determination of the contact angle in the same area of the sample. Furthermore, a theoretical evaluation of the impact of the roughness of a nonsmooth surface in the calculation of the contact angle when it is not taken into account according to Wenzel's model is also presented.
Contact angle in thick capillaries: a derivation based on energy balance
International Nuclear Information System (INIS)
Roura, Pere
2007-01-01
When a solid object is partially dipped beneath the surface of a liquid, this surface loses its horizontal shape near the solid surface and forms a meniscus. This phenomenon is governed by the general trend of any system to minimize its energy. In addition, the equilibrium of forces must be ensured for the meniscus. When both conditions (energy minimization and mechanical equilibrium) are considered together, the relationship between the contact angle and surface tensions (Young's equation) is obtained in a natural and simple way. (letters and comments)
Sensitivity enhancement by multiple-contact cross-polarization under magic-angle spinning.
Raya, J; Hirschinger, J
2017-08-01
Multiple-contact cross-polarization (MC-CP) is applied to powder samples of ferrocene and l-alanine under magic-angle spinning (MAS) conditions. The method is described analytically through the density matrix formalism. The combination of a two-step memory function approach and the Anderson-Weiss approximation is found to be particularly useful to derive approximate analytical solutions for single-contact Hartmann-Hahn CP (HHCP) and MC-CP dynamics under MAS. We show that the MC-CP sequence requiring no pulse-shape optimization yields higher polarizations at short contact times than optimized adiabatic passage through the HH condition CP (APHH-CP) when the MAS frequency is comparable to the heteronuclear dipolar coupling, i.e., when APHH-CP through a single sideband matching condition is impossible or difficult to perform. It is also shown that the MC-CP sideband HH conditions are generally much broader than for single-contact HHCP and that efficient polarization transfer at the centerband HH condition can be reintroduced by rotor-asynchronous multiple equilibrations-re-equilibrations with the proton spin bath. Boundary conditions for the successful use of the MC-CP experiment when relying on spin-lattice relaxation for repolarization are also examined. Copyright © 2017 Elsevier Inc. All rights reserved.
Nishimura, T; Doi, K; Fujimoto, H
2015-08-01
Touch-sensitive screen terminals enabling intuitive operation are used as input interfaces in a wide range of fields. Tablet terminals are one of the most common devices with a touch-sensitive screen. They have a feature of good portability, enabling use under various conditions. On the other hand, they require a GUI designed to prevent decrease of usability under various conditions. For example, the angle of fingertip contact with the display changes according to finger posture during operation and how the case is held. When a human fingertip makes contact with an object, the contact area between the fingertip and contact object increases or decreases as the contact angle changes. A touch-sensitive screen detects positions using the change in capacitance of the area touched by the fingertip; hence, differences in contact area between the touch-sensitive screen and fingertip resulting from different forefinger angles during operation could possibly affect operability. However, this effect has never been studied. We therefore conducted an experiment to investigate the relationship between size/spacing and operability, while taking the effect of fingertip contact angle into account. As a result, we have been able to specify the button size and spacing conditions that enable accurate and fast operation regardless of the forefinger contact angle.
International Nuclear Information System (INIS)
Escobar, Juan V.; Garza, Cristina; Alonso, Juan Carlos; Castillo, Rolando
2013-01-01
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.
Energy Technology Data Exchange (ETDEWEB)
Escobar, Juan V., E-mail: escobar@fisica.unam.mx [Instituto de Física, Universidad Nacional Autónoma de México, PO Box 20-364, DF, México, 01000 (Mexico); Garza, Cristina, E-mail: cgarza@fisica.unam.mx [Instituto de Física, Universidad Nacional Autónoma de México, PO Box 20-364, DF, México, 01000 (Mexico); Alonso, Juan Carlos, E-mail: alonso@unam.mx [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, PO Box 70-360, DF, México, 04510 (Mexico); Castillo, Rolando, E-mail: rolandoc@fisica.unam.mx [Instituto de Física, Universidad Nacional Autónoma de México, PO Box 20-364, DF, México, 01000 (Mexico)
2013-05-15
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.
Haagh, Martinus Everardus Johannes; Sîretanu, Igor; Duits, Michel; Mugele, Friedrich Gunther
2017-01-01
The effectiveness of water flooding oil recovery depends to an important extent on the competitive wetting of oil and water on the solid rock matrix. Here, we use macroscopic contact angle goniometry in highly idealized model systems to evaluate how brine salinity affects the balance of wetting forces and to infer the microscopic origin of the resultant contact angle alteration. We focus, in particular, on two competing mechanisms debated in the literature, namely, double-layer expansion and ...
Effect of solution and leaf surface polarity on droplet spread area and contact angle.
Nairn, Justin J; Forster, W Alison; van Leeuwen, Rebecca M
2016-03-01
How much an agrochemical spray droplet spreads on a leaf surface can significantly influence efficacy. This study investigates the effect solution polarity has on droplet spreading on leaf surfaces and whether the relative leaf surface polarity, as quantified using the wetting tension dielectric (WTD) technique, influences the final spread area. Contact angles and spread areas were measured using four probe solutions on 17 species. Probe solution polarity was found to affect the measured spread area and the contact angle of the droplets on non-hairy leaves. Leaf hairs skewed the spread area measurement, preventing investigation of the influence of surface polarity on hairy leaves. WTD-measured leaf surface polarity of non-hairy leaves was found to correlate strongly with the effect of solution polarity on spread area. For non-polar leaf surfaces the spread area decreases with increasing solution polarity, for neutral surfaces polarity has no effect on spread area and for polar leaf surfaces the spread area increases with increasing solution polarity. These results attest to the use of the WTD technique as a means to quantify leaf surface polarity. © 2015 Society of Chemical Industry. © 2015 Society of Chemical Industry.
Contact angle and surface tension measurements of a five-ring polyphenyl ether
Jones, W. R., Jr.
1986-01-01
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 220 C 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.
Adsorption of modified dextrins on molybdenite: AFM imaging, contact angle, and flotation studies.
Beaussart, Audrey; Parkinson, Luke; Mierczynska-Vasilev, Agnieszka; Beattie, David A
2012-02-15
The adsorption of three dextrins (a regular wheat dextrin, Dextrin TY, carboxymethyl (CM) Dextrin, and hydroxypropyl (HP) Dextrin) on molybdenite has been investigated using adsorption isotherms, tapping mode atomic force microscopy (TMAFM), contact angle measurements, and dynamic bubble-surface collisions. In addition, the effect of the polymers on the flotation recovery of molybdenite has been determined. The isotherms revealed the importance of molecular weight in determining the adsorbed amounts of the polymers on molybdenite at plateau coverage. TMAFM revealed the morphology of the three polymers, which consisted of randomly dispersed domains with a higher area fraction of surface coverage for the substituted dextrins. The contact angle of polymer-treated molybdenite indicated that polymer layer coverage and hydration influenced the mineral surface hydrophobicity. Bubble-surface collisions indicated that the polymers affected thin film rupture and dewetting rate differently, correlating with differences in the adsorbed layer morphology. Direct correlations were found between the surface coverage of the adsorbed layers, their impact on thin film rupture time, and their impact on flotation recovery, highlighting the paramount role of the polymer morphology in the bubble/particle attachment process and subsequent flotation. Copyright © 2011 Elsevier Inc. All rights reserved.
Relation between the size of fog droplets and their contact angles with CR39 surfaces
International Nuclear Information System (INIS)
Grosu, G; Andrzejewski, L; Veilleux, G; Ross, G G
2004-01-01
The formation of fog on CR39 surfaces has been studied. Water droplets form fog coalesce with time, especially during the first 20 s at the beginning of the formation of fog. Consequently, their mean diameter increases. Formation of fog being related to the wettability of the surfaces, the latter has been increased by the implantation of Ar ions into CR39 surfaces under an oxygen partial pressure. A very wetting CR39 surface with advancing (ACA) and receding (RCA) contact angles below 5 deg. has been obtained with an implantation dose of 1.28x10 17 Ar + cm -2 . In this condition, no formation of fog was observed. Characterization using x-ray photoelectron spectroscopy has shown that the molecular structure of CR39 is strongly modified by Ar + implantation, which would be responsible for the increase in wettability. Unfortunately, both ACA and RCA increase with time, which is called ageing, and the formation of fog is again observed. The diameter and concentration of water droplets forming fog have been plotted against the contact angle. These plots show that no formation of fog occurs for ACA 15 He + cm -2 and an energy of 2 keV, sufficient to push the ions deeper than the Ar depth profile, delays the ageing effect in such a way that ACA ≅ 40 deg. is reached after ∼2000 h and no formation of fog is observed during these first ∼2000 h
Apparent dynamic contact angle of an advancing gas--liquid meniscus
International Nuclear Information System (INIS)
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 Θ 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 Θ=7.48 Ca 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 1/3 dependence occurs only at very low Ca, where the intermolecular forces become more important and tan Θ diverges slightly from the above asymptotic behavior toward lower values
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
Directory of Open Access Journals (Sweden)
Zaitsev D.V.
2015-01-01
Full Text Available The effect of equilibrium contact angle on dynamics of dry spot spreading at disruption of a horizontal water layer heated locally from the substrate was studied using the high-speed Schlieren technique. Different methods of working surface processing were applied; this allowed variations of the equilibrium contact angle from 27±6° to 74±9° without a change in thermal properties of the system. It is found out that substrate wettability significantly affects the propagation velocity of dry spot and its final size. It is also found out that the velocity of contact line propagation is higher in the areas of substrate with a higher temperature.
Pittoni, Paola G; Lin, Chia-Hui; Yu, Teng-Shiang; Lin, Shi-Yow
2014-08-12
Could a unique receding contact angle be indicated for describing the wetting properties of a real gas-liquid-solid system? Could a receding contact angle be defined if the triple line of a sessile drop is not moving at all during the whole measurement process? To what extent is the receding contact angle influenced by the intrinsic properties of the system or the measurement procedures? In order to answer these questions, a systematic investigation was conducted in this study on the effects of substrate roughness and relative humidity on the behavior of pure water drops spreading and evaporating on polycarbonate (PC) surfaces characterized by different morphologies. Dynamic, advancing, and receding contact angles were found to be strongly affected by substrate roughness. Specifically, a receding contact angle could not be measured at all for drops evaporating on the more rugged PC surfaces, since the drops were observed strongly pinning to the substrate almost until their complete disappearance. Substrate roughness and system relative humidity were also found responsible for drastic changes in the depinning time (from ∼10 to ∼60 min). Thus, for measurement observations not sufficiently long, no movement of the triple line could be noted, with, again, the failure to find a receding contact angle. Therefore, to keep using concepts such as the receding contact angle as meaningful specifications of a given gas-liquid-solid system, the imperative to carefully investigate and report the inner characteristics of the system (substrate roughness, topography, impurities, defects, chemical properties, etc.) is pointed out in this study. The necessity of establishing methodological standards (drop size, measurement method, system history, observation interval, relative humidity, etc.) is also suggested.
The method of contact angle measurements and estimation of work of adhesion in bioleaching of metals
Directory of Open Access Journals (Sweden)
Matlakowska Renata
1999-01-01
Full Text Available In this paper, we present our method for the measurement of contact angles on the surface of minerals during the bioleaching process because the standard deviation obtained in our measurements achieved unexpectedly low error. Construction of a goniometer connected with a specially prepared computer program allowed us to repeat measurements several times over a short time course, yielding excellent results. After defining points on the outline of the image of a drop and its baseline as well of the first approximation of the outline of the drop, an iterative process is initiated that is aimed at fitting the model of the drop and baseline. In turn, after defining the medium for which measurements were made, the work of adhesion is determined according to Young-Dupré equation. Calculations were made with the use of two methods named the L-M and L-Q methods.
Energy Technology Data Exchange (ETDEWEB)
Wu, Cyuan-Jhang; Li, Yueh-Feng [Department of Chemical and Materials Engineering, National Central University, Jhongli 320, Taiwan (China); Woon, Wei-Yen [Department of Physics, National Central University, Jhongli 320, Taiwan (China); Sheng, Yu-Jane, E-mail: yjsheng@ntu.edu.tw [Department of Chemical Engineering, National Taiwan University, Taipei 106, Taiwan (China); Tsao, Heng-Kwong, E-mail: hktsao@cc.ncu.edu.tw [Department of Chemical and Materials Engineering, National Central University, Jhongli 320, Taiwan (China); Department of Physics, National Central University, Jhongli 320, Taiwan (China)
2016-11-01
Highlights: • Contact angle hysteresis(CAH) on four graphitic surfacesisinvestigated. • The hysteresis loopof water drops on the polished graphite sheetshowsparticularly small receding contact angle. • The significant CAH observed on CVD graphene and highly oriented pyrolytic graphite is attributed mainly to adhesion hysteresis. • An oil-infused surface of a graphite sheet is produced by imbibition of hexadecane into its porous structure. • The hysteresis-free property for water drops on such a surface is examined and quantitatively explained. - Abstract: 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.
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.
Kingston, David C; Acker, Stacey M
2018-01-23
In high knee flexion, contact between the posterior thigh and calf is expected to decrease forces on tibiofemoral contact surfaces, therefore, thigh-calf contact needs to be thoroughly characterized to model its effect. This study measured knee angles and intersegmental contact parameters in fifty-eight young healthy participants for six common high flexion postures using motion tracking and a pressure sensor attached to the right thigh. Additionally, we introduced and assessed the reliability of a method for reducing noise in pressure sensor output. Five repetitions of two squatting, two kneeling, and two unilateral kneeling movements were completed. Interactions of posture by sex occurred for thigh-calf and heel-gluteal center of force, and thigh-calf contact area. Center of force in thigh-calf regions was farther from the knee joint center in females, compared to males, during unilateral kneeling (82 and 67 mm respectively) with an inverted relationship in the heel-gluteal region (331 and 345 mm respectively), although caution is advised when generalizing these findings from a young, relatively fit sample to a population level. Contact area was larger in females when compared to males (mean of 155.61 and 137.33 cm 2 across postures). A posture main effect was observed in contact force and sex main effects were present in onset and max angle. Males had earlier onset (121.0°) and lower max angle (147.4°) with onset and max angles having a range between movements of 8° and 3° respectively. There was a substantial total force difference of 139 N between the largest and smallest activity means. Force parameters measured in this study suggest that knee joint contact models need to incorporate activity-specific parameters when estimating loading. Copyright © 2017 Elsevier Ltd. All rights reserved.
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.
Lattice Boltzmann simulations of the contact angle in a liquid-gas system
International Nuclear Information System (INIS)
Ryu, Seung Yeob; Park, Cheon Tae; Kim, Keung Koo
2008-01-01
Recently, the lattice Boltzmann method (LBM) has gained much attention for its ability to simulate fluid flows, and for its potential advantages over a conventional CFD method. The key advantages of LBM are, (1) suitability for parallel computations, (2) absence of the need to solve the time-consuming Poisson equation for a pressure, and (3) an ease with multiphase flows, complex geometries and interfacial dynamics may be treated. The shape of a moving droplet is difficult to investigate analytically because the classical continuum hydrodynamic equations of motion with the usual no-slip condition at the surface predict a singularity in the stress at the contact line. Briant et al. have proposed a wetting boundary condition by using the wetting potential. In this study, we introduce the wetting boundary condition into the LBM proposed by Zheng et al. The static contact angle of a droplet onto a wall in order to validate the method is calculated. By adopting a finite difference gradient operator of a sufficient isotropy, the spurious currents can be made small in the wall surface. The main objective of the present work is to establish the lattice Boltzmann method as a viable tool for the simulation of multiphase or multi-component flows
Yang, Runhua; Yang, Lixin
2018-06-01
Plasma immersion ion implantation (PIII) was used to fabricate micro/nano structures on monocrystalline Si surfaces with different ratios of mixed gases (SF6/O2). The micro/nano structures on the surfaces of the sample were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results showed that with increasing ratio of mixed gases (SF6/O2), the height of the micro/nano structures first increased and then decreased. Contact-angle measurements indicated that the surfaces' micro/nano structures have an obvious effect on the contact-angle, and could cause a change in surface wettability. The theoretical analysis of contact-angle showed that the Wenzel and Cassie theories cannot predict the contact-angle of a roughened surface accurately, and should be corrected for practical applications using an actual model. Moreover, the contact-angle first increased and then decreased with increasing ratio of mixed gases (SF6/O2), which is in accordance with the change of the height of micro/nano structures.
Bottiglione, F; Carbone, G
2015-01-14
The apparent contact angle of large 2D drops with randomly rough self-affine profiles is numerically investigated. The numerical approach is based upon the assumption of large separation of length scales, i.e. it is assumed that the roughness length scales are much smaller than the drop size, thus making it possible to treat the problem through a mean-field like approach relying on the large-separation of scales. The apparent contact angle at equilibrium is calculated in all wetting regimes from full wetting (Wenzel state) to partial wetting (Cassie state). It was found that for very large values of the roughness Wenzel parameter (r(W) > -1/ cos θ(Y), where θ(Y) is the Young's contact angle), the interface approaches the perfect non-wetting condition and the apparent contact angle is almost equal to 180°. The results are compared with the case of roughness on one single scale (sinusoidal surface) and it is found that, given the same value of the Wenzel roughness parameter rW, the apparent contact angle is much larger for the case of a randomly rough surface, proving that the multi-scale character of randomly rough surfaces is a key factor to enhance superhydrophobicity. Moreover, it is shown that for millimetre-sized drops, the actual drop pressure at static equilibrium weakly affects the wetting regime, which instead seems to be dominated by the roughness parameter. For this reason a methodology to estimate the apparent contact angle is proposed, which relies only upon the micro-scale properties of the rough surface.
The contact angle of wetting of the solid phase of soil before and after chemical modification
Directory of Open Access Journals (Sweden)
Tyugai Zemfira
2015-07-01
Full Text Available Wettability of soil affects a wide variety of processes including infiltration, preferential flow and surface runoff. Wettability of surface is usually expressed in terms of contact angle (CA measurement. If the CA between liquid and solid surface is less than 90°, the surface is called hydrophilic, otherwise the surface is called hydrophobic. If the CA of water droplet on hydrophilic surface is in a range of 0-30° this surface is called superhydrophilic. In case of superhydrophobic surfaces the CA exceeds 150° that means that these surfaces are extremely difficult to wet. CA of wetting of mineral soil particles depends on the overlying organic and iron compounds. The object of study is a sample of the humus-accumulative horizon of typical chernozem (Kursk, Russia and two samples (horizons A1, B2 of red ferrallitic soils (Fr. Norfolk, NE Oceania. The soil samples were analyzed for organic carbon, forms of non-silicate iron and hydrophobic-hydrophilic composition of humic substances. CA of wetting was determined in the intact samples and after removal of organic matter (H2O2 treatment, amorphous and crystallized forms of iron. Static contact angles were determined with the sessile drop method using a digital goniometer (Drop Shape Analysis System, DSA100, Krüss GmbH, Hamburg, Germany. The contact angle was calculated by the Young–Laplace method (fitting of Young–Laplace equation to the drop shape. The measurements were repeated 10-15 times for every sample. Oxidation of organic matter (H2O2 treatment causes an increase in the values of CA of wetting (in chernozem from 9.3 to 28,0-29.5º, in ferrallitic soil from 18.0 − 27.3 to 22.4 − 33.4º. CA remained constant for chernozem and slightly decreased in the case of ferrallitic soil, when the removal of amorphous and crystallized forms of iron was performed on samples pretreated with H2O2. CA increase occurs after successive removal of nonsilicate forms of iron from soil samples of
Sopher, Ran S; Amis, Andrew A; Davies, D Ceri; Jeffers, Jonathan Rt
2017-01-01
Data about a muscle's fibre pennation angle and physiological cross-sectional area are used in musculoskeletal modelling to estimate muscle forces, which are used to calculate joint contact forces. For the leg, muscle architecture data are derived from studies that measured pennation angle at the muscle surface, but not deep within it. Musculoskeletal models developed to estimate joint contact loads have usually been based on the mean values of pennation angle and physiological cross-sectional area. Therefore, the first aim of this study was to investigate differences between superficial and deep pennation angles within each muscle acting over the ankle and predict how differences may influence muscle forces calculated in musculoskeletal modelling. The second aim was to investigate how inter-subject variability in physiological cross-sectional area and pennation angle affects calculated ankle contact forces. Eight cadaveric legs were dissected to excise the muscles acting over the ankle. The mean surface and deep pennation angles, fibre length and physiological cross-sectional area were measured. Cluster analysis was applied to group the muscles according to their architectural characteristics. A previously validated OpenSim model was used to estimate ankle muscle forces and contact loads using architecture data from all eight limbs. The mean surface pennation angle for soleus was significantly greater (54%) than the mean deep pennation angle. Cluster analysis revealed three groups of muscles with similar architecture and function: deep plantarflexors and peroneals, superficial plantarflexors and dorsiflexors. Peak ankle contact force was predicted to occur before toe-off, with magnitude greater than five times bodyweight. Inter-specimen variability in contact force was smallest at peak force. These findings will help improve the development of experimental and computational musculoskeletal models by providing data to estimate force based on both surface and deep
Jasikova, Darina; Kotek, Michal
2014-03-01
The development of industrial technology also brings with optimized surface quality, particularly where there is contact with food. Application ultra-hydrophobic surface significantly reduces the growth of bacteria and facilitates cleaning processes. Testing and evaluation of surface quality are used two methods: impinging droplet and inclined surface method optimized with high speed shadowgraphy, which give information about dynamic contact angle. This article presents the results of research into new methods of measuring ultra-hydrophobic patented technology.
Directory of Open Access Journals (Sweden)
Safiya Benni
2014-01-01
Full Text Available 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-DS4 and was labeled D−. The other film was the same as D− but with an added terminal layer of DEAE polycation: (DEAE-DS4-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-DS4 films. (DEAE-DS4 films could enhance HUVEC proliferation in agreement with fibronectin ability to easily change from conformation.
Prediction of dynamic contact angle histories of a bubble growing at a wall
International Nuclear Information System (INIS)
Geld, Cees W.M. van der
2004-01-01
A fast growing boiling bubble at the verge of detaching from a plane wall is usually shaped as a truncated sphere, and experiences various hydrodynamic forces due to its expansion and the motion of its center of mass. In a homogeneous flow field, one of the forces is the so-called bubble growth force that is essentially due to inertia. This force is usually evaluated with the aid of approximate expressions [Int. J. Heat Mass Transfer 36 (1993) 651, Int. J. Heat Mass Transfer 38 (1995) 2075]. In the present study an exact expression for the expansion force is derived for the case of a truncated sphere attached to a plane, infinite wall. The Lagrange-Thomson formalism is applied. Two Euler-Lagrange equations are derived, one governing the motion of the center of mass, the other governing expansion a kind of extended Rayleigh-Plesset equation. If a constitutive equation for the gas-vapor content of the bubble is given, initial conditions and these two differential equations determine the dynamics of the growing truncated sphere that has its foot on a plane, infinite wall. Simulations are carried out for a given expansion rate to predict the history of the dynamic contact angle. The simulations increase the understanding of mechanisms controlling detachment, and yield realistic times of detachment
Haagh, Martinus Everardus Johannes; Sîretanu, Igor; Duits, Michel; Mugele, Friedrich Gunther
2017-01-01
The effectiveness of water flooding oil recovery depends to an important extent on the competitive wetting of oil and water on the solid rock matrix. Here, we use macroscopic contact angle goniometry in highly idealized model systems to evaluate how brine salinity affects the balance of wetting
Haagh, M E J; Siretanu, I; Duits, M H G; Mugele, F
2017-04-11
The effectiveness of water flooding oil recovery depends to an important extent on the competitive wetting of oil and water on the solid rock matrix. Here, we use macroscopic contact angle goniometry in highly idealized model systems to evaluate how brine salinity affects the balance of wetting forces and to infer the microscopic origin of the resultant contact angle alteration. We focus, in particular, on two competing mechanisms debated in the literature, namely, double-layer expansion and divalent cation bridging. Our experiments involve aqueous droplets with a variable content of chloride salts of Na + , K + , Ca 2+ , and Mg 2+ , wetting surfaces of muscovite and amorphous silica, and an environment of ambient decane containing small amounts of fatty acids to represent polar oil components. By diluting the salt content in various manners, we demonstrate that the water contact angle on muscovite, not on silica, decreases by up to 25° as the divalent cation concentration is reduced from typical concentrations in seawater to zero. Decreasing the ionic strength at a constant divalent ion concentration, however, has a negligible effect on the contact angle. We discuss the consequences for the interpretation of core flooding experiments and the identification of a microscopic mechanism of low salinity water flooding, an increasingly popular, inexpensive, and environment-friendly technique for enhanced oil recovery.
Palasantzas, George
2007-01-01
Capillary condensation between the electrodes of microswitches influences the effective pull-in voltage in a manner that depends on the contact angle of the capillary meniscus and the presence of plate surface roughness. Indeed, surface roughening is shown to have a stronger influence on the pull-in
Capra, P; Musitelli, G; Perugini, P
2017-08-01
The aim of this work was to use the contact angle measurement in order to predict the behaviour of ingredients and finished cosmetic products on skin to improve skin feel and product texture. Different classes of cosmetic ingredients and formulations were evaluated. The contact angle measurements were carried out by the sessile drop method using an apparatus, designed and set up in laboratory. Glass, Teflon and human skin were the reference substrates. In a preliminary phase, TEWL parameter, sebum content and hydration of human skin were measured to set up method. Data demonstrated that glass substrate may be used as replacement of the skin:critical surface tension of skin and glass were about of 27 and 31 dyne cm -1 , respectively. Non-ionic surfactant with increasing HLB was evaluated: a correlation between contact angle measured and HLB was not observed because of different and complex molecular structure. In detail, ethylhexyl hydroxystearate (θ glass = 17.1°) showed lower contact angle value with respect to Polysorbate 20 (θ glass = 28.1°). Sodium laureth sulphate and stearalkonium chloride were also evaluated: anionic molecule showed more affinity for glass with respect to Teflon (θ glass = 21.7° and θ Teflon = 52.3°). Lipids and silicones showed different affinity for substrate according to hydrophilic groups and hydrocarbon chain: contact angles of silicones remained unchanged independently from substrate. Finished cosmetic products (O/W, W/O emulsions, cleansing oil, dry skin oil) showed different profiles according to surfactant and its affinity for continuous phase of the formulation. Comparing the values of the contact angle on skin of non-ionic surfactants, as ethylhexyl hydroxystearate and Polysorbate 20, they showed values lower (near to zero) than ones of sodium laureth sulphate and Stearalkonium Chloride (21.7° and 66.8°, respectively). Finally, finished cosmetic products tested on human skin showed different profile: corresponded contact
Lee, Sangmin; Hwang, Woonbong
2009-03-01
Superhydrophobic surfaces designed to improve hydrophobicity have high advancing contact angles corresponding to the Cassie state, but these surfaces also exhibit high contact angle hysteresis. We report here a simple and inexpensive method for fabricating superhydrophobic tangled nanofiber structures with ultralow contact angle hysteresis and no-aging degradation, based on a widening process. The resulting nanostructures are suitable for diverse applications including microfluidic devices for biological studies and industrial self-cleaning products for automobiles, ships and houses.
Kawashima, Rumi; Matsushita, Kenji; Fujimoto, Hisataka; Maeda, Naoyuki; Nishida, Kohji
2015-01-01
To report air pressure-induced corneal deformation and iridocornea contact in eyes with primary angle closure (PAC) during intraocular pressure (IOP) measurement performed using a novel noncontact tonometer. A single case report. We report a patient with bilateral angle closure. One eye had acute PAC and the other had PAC. The latter was evaluated by the movements of the cornea and iris during IOP measurement using a noncontact tonometer. During the examination, the corneal endothelium and the iris came into contact at the mid-peripheral pupillary area in the left eye with PAC during the corneal reaction to an air puff. In contrast, the corneal endothelium in the pupillary area did not come into contact with the iris. Although we observed only 1 case and there could be limitations in its interpretation, IOP measurements using a noncontact tonometer may create mechanical stress on the corneal endothelium in eyes with PAC with a very shallow anterior chamber.
Some remarks on the solid surface tension determination from contact angle measurements
Energy Technology Data Exchange (ETDEWEB)
Zdziennicka, Anna; Szymczyk, Katarzyna; Krawczyk, Joanna; Jańczuk, Bronisław, E-mail: bronislaw.janczuk@poczta.umcs.lublin.pl
2017-05-31
Graphical abstract: Surface tension of PE, nylon 6 and quartz from different approaches to the interface tension. - Highlights: • New values of water and formamide surface tension components were established. • Quartz surface tension depends on its crystal face. • Usefulness of different approaches for solid surface tension determination was tested. - Abstract: The measurements of water, formamide and diiodomethane contact angle (θ) on polytetrafluoroethylene (PTFE), polyethylene (PE), polymethyl methacrylate (PMMA), nylon 6, quartz and silica were performed. Based on the θ values of these liquids obtained on PTFE, the Lifshitz-van der Waals and acid-base and/or dispersion and polar components of their surface tension (ST) were determined. In turn, the θ values for water, formamide and diiodomethane on PMMA were applied to calculate the electron-acceptor and electron-donor parameters of the Lewis acid-base component of the formamide ST. For this calculation the same values of the electron-acceptor and electron-donor parameters for water ST were used. Taking into account the values of components and parameters of water, formamide and diiodomethane ST obtained by us, van Oss et al. and from the water(formamide)-n-alkane and water-diiodomethane interface tension, the components and parameters of studied solids ST were calculated. To this end different approaches to the interface tension were considered. The obtained values were compared with those in the literature. It was concluded that for determination of solid ST components and parameters, those of water, formamide and diiodomethane ST obtained from the θ measurements on the model solids should be used.
Effect of Annealing Temperature on the Water Contact Angle of PVD Hard Coatings
Yang, Yu-Sen; Cho, Ting-Pin
2013-01-01
Various PVD (physical vapor deposition) hard coatings including nitrides and metal-doped diamond-like carbons (Me-DLC) were applied in plastic injection and die-casting molds to improve wear resistance and reduce sticking. In this study, nitrides hcp-AlN (hexagonal close-packed AlN), Cr2N, (CrAl)2N) and Me-DLC (Si-DLC and Cr-DLC) coatings were prepared using a closed field unbalanced magnetron reactive sputtering system. The coatings were annealed in air for 2 h at various temperatures, after which the anti-sticking properties were assessed using water contact angle (WCA) measurements. The as-deposited hcp-AlN, Cr2N and (CrAl)2N coatings exhibit hydrophobic behavior and exhibit respective WCAs of 119°, 106° and 101°. The as-deposited Si-DLC and Cr-DLC coatings exhibit hydrophilic behavior and exhibit respective WCAs of 74° and 88°. The annealed Cr2N and (CrAl)2N coatings exhibit hydrophobic behavior with higher WCAs, while the annealed hcp-AlN, Si-DLC and Cr-DLC coatings are hydrophilic. The increased WCA of the annealed Cr2N and (CrAl)2N coatings is related to their crystal structure and increased roughness. The decreased WCA of the annealed hcp-AlN, Si-DLC and Cr-DLC coatings is related to their crystal structures and has little correlation with roughness. PMID:28811440
Effect of Annealing Temperature on the Water Contact Angle of PVD Hard Coatings.
Yang, Yu-Sen; Cho, Ting-Pin
2013-08-07
Various PVD (physical vapor deposition) hard coatings including nitrides and metal-doped diamond-like carbons (Me-DLC) were applied in plastic injection and die-casting molds to improve wear resistance and reduce sticking. In this study, nitrides hcp-AlN (hexagonal close-packed AlN), Cr₂N, (CrAl)₂N) and Me-DLC (Si-DLC and Cr-DLC) coatings were prepared using a closed field unbalanced magnetron reactive sputtering system. The coatings were annealed in air for 2 h at various temperatures, after which the anti-sticking properties were assessed using water contact angle (WCA) measurements. The as-deposited hcp-AlN, Cr₂N and (CrAl)₂N coatings exhibit hydrophobic behavior and exhibit respective WCAs of 119°, 106° and 101°. The as-deposited Si-DLC and Cr-DLC coatings exhibit hydrophilic behavior and exhibit respective WCAs of 74° and 88°. The annealed Cr₂N and (CrAl)₂N coatings exhibit hydrophobic behavior with higher WCAs, while the annealed hcp-AlN, Si-DLC and Cr-DLC coatings are hydrophilic. The increased WCA of the annealed Cr₂N and (CrAl)₂N coatings is related to their crystal structure and increased roughness. The decreased WCA of the annealed hcp-AlN, Si-DLC and Cr-DLC coatings is related to their crystal structures and has little correlation with roughness.
Baskaran, Mani; Ho, Sue-Wei; Tun, Tin A; How, Alicia C; Perera, Shamira A; Friedman, David S; Aung, Tin
2013-11-01
To evaluate the diagnostic performance of the iris-trabecular contact (ITC) index, a measure of the degree of angle-closure, using swept-source optical coherence tomography (SSOCT, CASIA SS-1000, Tomey Corporation, Nagoya, Japan) in comparison with gonioscopy. Prospective observational study. A total of 108 normal subjects and 32 subjects with angle-closure. The SSOCT 3-dimensional angle scans, which obtain radial scans for the entire circumference of the angle, were performed under dark conditions and analyzed using customized software by a single examiner masked to the subjects' clinical details. The ITC index was calculated as a percentage of the angle that was closed on SSOCT images. First-order agreement coefficient (AC1) statistics and area under the receiver operating characteristic curve (AUC) analyses were performed for angle-closure on the basis of the ITC index in comparison with gonioscopy. Angle-closure on gonioscopy was defined as nonvisibility of posterior trabecular meshwork for at least 2 quadrants. Agreement of the ITC index with gonioscopically defined angle-closure was assessed using the AC1 statistic. Study subjects were predominantly Chinese (95.7%) and female (70.7%), with a mean age of 59.2 (standard deviation, 8.9) years. The median ITC index was 15.24% for gonioscopically open-angle eyes (n = 108) and 48.5% for closed-angle eyes (n = 32) (P = 0.0001). The agreement for angle-closure based on ITC index cutoffs (>35% and ≥50%) and gonioscopic angle-closure was 0.699 and 0.718, respectively. The AUC for angle-closure detection using the ITC index was 0.83 (95% confidence interval, 0.76-0.89), with an ITC index >35% having a sensitivity of 71.9% and specificity of 84.3%. The ITC index is a summary measure of the circumferential extent of angle-closure as imaged with SSOCT. The index had moderate agreement and good diagnostic performance for angle-closure with gonioscopy as the reference standard. Copyright © 2013 American Academy of
Frank, Florian; Liu, Chen; Scanziani, Alessio; Alpak, Faruk O; Riviere, Beatrice
2018-08-01
We consider an energy-based boundary condition to impose an equilibrium wetting angle for the Cahn-Hilliard-Navier-Stokes phase-field model on voxel-set-type computational domains. These domains typically stem from μCT (micro computed tomography) imaging of porous rock and approximate a (on μm scale) smooth domain with a certain resolution. Planar surfaces that are perpendicular to the main axes are naturally approximated by a layer of voxels. However, planar surfaces in any other directions and curved surfaces yield a jagged/topologically rough surface approximation by voxels. For the standard Cahn-Hilliard formulation, where the contact angle between the diffuse interface and the domain boundary (fluid-solid interface/wall) is 90°, jagged surfaces have no impact on the contact angle. However, a prescribed contact angle smaller or larger than 90° on jagged voxel surfaces is amplified. As a remedy, we propose the introduction of surface energy correction factors for each fluid-solid voxel face that counterbalance the difference of the voxel-set surface area with the underlying smooth one. The discretization of the model equations is performed with the discontinuous Galerkin method. However, the presented semi-analytical approach of correcting the surface energy is equally applicable to other direct numerical methods such as finite elements, finite volumes, or finite differences, since the correction factors appear in the strong formulation of the model. Copyright © 2018 Elsevier Inc. All rights reserved.
Muthu, Satish; Childress, Amy; Brant, Jonathan
2014-08-15
Membrane fouling assessed from a fundamental standpoint within the context of the Derjaguin-Landau-Verwey-Overbeek (DLVO) model. The DLVO model requires that the properties of the membrane and foulant(s) be quantified. Membrane surface charge (zeta potential) and free energy values are characterized using streaming potential and contact angle measurements, respectively. Comparing theoretical assessments for membrane-colloid interactions between research groups requires that the variability of the measured inputs be established. The impact that such variability in input values on the outcome from interfacial models must be quantified to determine an acceptable variance in inputs. An interlaboratory study was conducted to quantify the variability in streaming potential and contact angle measurements when using standard protocols. The propagation of uncertainty from these errors was evaluated in terms of their impact on the quantitative and qualitative conclusions on extended DLVO (XDLVO) calculated interaction terms. The error introduced into XDLVO calculated values was of the same magnitude as the calculated free energy values at contact and at any given separation distance. For two independent laboratories to draw similar quantitative conclusions regarding membrane-foulant interfacial interactions the standard error in contact angle values must be⩽2.5°, while that for the zeta potential values must be⩽7 mV. Copyright © 2014 Elsevier Inc. All rights reserved.
Das, Subir K; Egorov, Sergei A; Virnau, Peter; Winter, David; Binder, Kurt
2018-06-27
Results from Monte Carlo simulations of wall-attached droplets in the three-dimensional Ising lattice gas model and in a symmetric binary Lennard-Jones fluid, confined by antisymmetric walls, are analyzed, with the aim to estimate the dependence of the contact angle [Formula: see text] on the droplet radius [Formula: see text] of curvature. Sphere-cap shape of the wall-attached droplets is assumed throughout. An approach, based purely on 'thermodynamic' observables, e.g. chemical potential, excess density due to the droplet, etc, is used, to avoid ambiguities in the decision which particles belong (or do not belong, respectively) to the droplet. It is found that the results are compatible with a variation [Formula: see text], [Formula: see text] being the contact angle in the thermodynamic limit ([Formula: see text]). The possibility to use such results to estimate the excess free energy related to the contact line of the droplet, namely the line tension, at the wall, is discussed. Various problems that hamper this approach and were not fully recognized in previous attempts to extract the line tension are identified. It is also found that the dependence of wall tensions on the difference of chemical potential of the droplet from that at the bulk coexistence provides effectively a change of the contact angle of similar magnitude. The simulation approach yields precise estimates for the excess density due to wall-attached droplets and the corresponding free energy excess, relative to a system without a droplet at the same chemical potential. It is shown that this information suffices to estimate nucleation barriers, not affected by ambiguities on droplet shape, contact angle and line tension.
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
Measurement of contact angle in a clearance-fit pin-loaded hole
Prabhakaran, R.; Naik, R. A.
1986-01-01
A technique which measures load-contact variation in a clearance-fit, pin-loaded hole is presented in detail. A steel instrumented pin, which activates a make-or-break electrical circuit in the pin-hole contact region, was inserted into one aluminum and one polycarbonate specimen. The resulting load-contact variations are indicated schematically. The ability to accurately determine the arc of contact at any load was crucial to this measurement. It is noted that this simple experimental technique is applicable to both conducting and nonconducting materials.
International Nuclear Information System (INIS)
Al-Amoudi, Ahmed; Williams, Paul; Al-Hobaib, A.S.; Lovitt, Robert W.
2008-01-01
In membrane process industries, membrane cleaning is one of the most important concerns from both economical and scientific points of view. Though cleaning is important to recover membrane performance, an inappropriate selection of cleaning agents may result into unsatisfactory cleaning or irreparable membrane. In this study the cleaning performance has been studied with measurements of membrane contact angle, Updated Donnan steric partitioning pore model (UDSPM) and salt rejection as well as flux measurement. Thin film nanofiltration (NF) membranes such as DK, HL and DL provided by GE Osmonics are used in this study. Tests were carried out with virgin DK, HL and DL as well as fouled DK membranes. Several cleaning agents were investigated; some of them were analytical grade such as HCl, NaOH and others such as SDS, mix agents were commercial grade agents that are already in use in commercial plants. Contact angle, DSPM and salt rejection as well as flux of virgin and fouled membranes before and after chemical cleaning were measured and compared. The contact angle measurements with and without chemical cleaning of different virgin and fouled membranes revealed very interesting results which may be used to characterise the membrane surface cleanliness. The contact angle results revealed that the cleaning agents are found to modify membrane surface properties (hydrophobicity/hydrophilicity) of the treated and untreated virgin and fouled membranes. The details of these results were also investigated and are reported in the paper. However, UDSPM method did not give any valuable information about pore size of the untreated and treated NF membranes. The salt rejection level of monovalent and divalent ions before and after cleaning by high and low pH cleaning agents is also investigated and is reported in the paper
Energy Technology Data Exchange (ETDEWEB)
Al-Amoudi, Ahmed [Centre for complex fluids processing, Multidisciplinary Nanotechnology Centre, School of Engineering, University of Wales, Swansea SA2 8PP (United Kingdom) and Saline Water Conversion Corporation (SWCC), Saline Water Desalination Research Institute Staff (Saudi Arabia)], E-mail: 310981@swan.ac.uk; Williams, Paul [Centre for complex fluids processing, Multidisciplinary Nanotechnology Centre, School of Engineering, University of Wales, Swansea SA2 8PP (United Kingdom); Al-Hobaib, A.S. [Institute of Atomic Energy Research, King Abdulaziz City for Science And Technology, P.O. Box 6086, Riyadh 11442 (Saudi Arabia); Lovitt, Robert W. [Centre for complex fluids processing, Multidisciplinary Nanotechnology Centre, School of Engineering, University of Wales, Swansea SA2 8PP (United Kingdom)
2008-04-30
In membrane process industries, membrane cleaning is one of the most important concerns from both economical and scientific points of view. Though cleaning is important to recover membrane performance, an inappropriate selection of cleaning agents may result into unsatisfactory cleaning or irreparable membrane. In this study the cleaning performance has been studied with measurements of membrane contact angle, Updated Donnan steric partitioning pore model (UDSPM) and salt rejection as well as flux measurement. Thin film nanofiltration (NF) membranes such as DK, HL and DL provided by GE Osmonics are used in this study. Tests were carried out with virgin DK, HL and DL as well as fouled DK membranes. Several cleaning agents were investigated; some of them were analytical grade such as HCl, NaOH and others such as SDS, mix agents were commercial grade agents that are already in use in commercial plants. Contact angle, DSPM and salt rejection as well as flux of virgin and fouled membranes before and after chemical cleaning were measured and compared. The contact angle measurements with and without chemical cleaning of different virgin and fouled membranes revealed very interesting results which may be used to characterise the membrane surface cleanliness. The contact angle results revealed that the cleaning agents are found to modify membrane surface properties (hydrophobicity/hydrophilicity) of the treated and untreated virgin and fouled membranes. The details of these results were also investigated and are reported in the paper. However, UDSPM method did not give any valuable information about pore size of the untreated and treated NF membranes. The salt rejection level of monovalent and divalent ions before and after cleaning by high and low pH cleaning agents is also investigated and is reported in the paper.
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.
Foroutan, Masumeh; Fatemi, S. Mahmood; Esmaeilian, Farshad; Fadaei Naeini, Vahid; Baniassadi, Majid
2018-05-01
In the present work, the effect of temperature gradient on the behavior of a water nano-droplet resting on a suspended graphene was studied based on a non-equilibrium molecular dynamics simulation. The acquired results indicate that the applied temperature gradient to the suspended graphene drives the water nano-droplet to the colder region. The droplet accelerates its motion toward the cold reservoir as the temperature gradient is increased. In addition to the translational motion of the nano-droplet, the vortical motion of the water molecules was also observed. Contact angle analysis was also utilized to describe the directional motion of the nano-droplet. The translational motion of the droplet leads to the estimation of contact angle hysteresis through advancing and receding contact angles while the rotational motion resulted in the advancing and receding fronts being switched with one another through the simulation. The average displacement vector of the water molecules shows that parts of the droplet seem to stagnate while other parts rotate around them. The reason behind this particular behavior was studied based on interaction energy contours between a water molecule and the suspended graphene. The obtained data indicate that the rotational motion is in agreement with the migration of the water molecules to low interaction energy regions in order to avoid high interaction energy areas.
Sharbatian, Atena; Abedini, Ali; Qi, ZhenBang; Sinton, David
2018-02-20
Carbon capture, storage, and utilization technologies target a reduction in net CO 2 emissions to mitigate greenhouse gas effects. The largest such projects worldwide involve storing CO 2 through enhanced oil recovery-a technologically and economically feasible approach that combines both storage and oil recovery. Successful implementation relies on detailed measurements of CO 2 -oil properties at relevant reservoir conditions (P = 2.0-13.0 MPa and T = 23 and 50 °C). In this paper, we demonstrate a microfluidic method to quantify the comprehensive suite of mutual properties of a CO 2 and crude oil mixture including solubility, diffusivity, extraction pressure, minimum miscibility pressure (MMP), and contact angle. The time-lapse oil swelling/extraction in response to CO 2 exposure under stepwise increasing pressure was quantified via fluorescence microscopy, using the inherent fluorescence property of the oil. The CO 2 solubilities and diffusion coefficients were determined from the swelling process with measurements in strong agreement with previous results. The CO 2 -oil MMP was determined from the subsequent oil extraction process with measurements within 5% of previous values. In addition, the oil-CO 2 -silicon contact angle was measured throughout the process, with contact angle increasing with pressure. In contrast with conventional methods, which require days and ∼500 mL of fluid sample, the approach here provides a comprehensive suite of measurements, 100-fold faster with less than 1 μL of sample, and an opportunity to better inform large-scale CO 2 projects.
Directory of Open Access Journals (Sweden)
Mamta Kaushik
2015-01-01
Materials and Methods: Seventy human mandibularfirst premolars were used and 140 longitudinal dentin slices were obtained from them. Each sample was irrigated with of 3% sodium hypochlorite (NaOCl, simulating the irrigation used during the chemomechanical preparation and then washed with 10ml of distilled water (DW. The samples were then divided into seven groups of 20 samples each. Group 1:NaOCl + DW, Group 2: QMix + DW, Group 3: 0.1% octenidine hydrochloride + DW, Group 4:Ethylenediaminetetraacetic acid (EDTA + DW + NaOCl + DW, Group 5: EDTA + DW + QMix + DW, Group 6: EDTA + DW + 0.1% Octenidine Hydrochloride + DW, and Group 7(control: DW. The contact angle between AH Plus and the samples was measured using Rame Hart Goniometer followed by statistical analysis of data. Results: Values of contact angle was least when samples were treated with QMix followed by treatment with 0.1% Octenidine Hydrochloride followed by 3% NaOCl. Removal of smear layer reduced contact angles in all cases except when samples were treated with 3% NaOCl. Results were statistically significant when 3% NaOCl was compared to 0.1% Octenidine Hydrochloride and QMix (P = 0.034. Statistically significant difference was seen before and after removal of smear layer for 3% NaOCl and 0.1% Octenidine Hydrochloride. (P = 0.003. Conclusion: Qmix is the irrigant of choice, but 0.1% octenidine hydrochloride may be recommended as a useful irrigant after further research.
Energy Technology Data Exchange (ETDEWEB)
DiStefano, Victoria H.; Cheshire, Michael C.; McFarlane, Joanna; Kolbus, Lindsay M.; Hale, Richard E.; Perfect, Edmund; Bilheux, Hassina Z.; Santodonato, Louis J.; Hussey, Daniel S.; Jacobson, David L.; LaManna, Jacob M.; Bingham, Philip R.; Starchenko, Vitaliy; Anovitz, Lawrence M.
2017-10-01
Understanding of fundamental processes and prediction of optimal parameters during the horizontal drilling and hydraulic fracturing process results in economically effective improvement of oil and natural gas extraction. Although, the modern analytical and computational models can capture fracture growth, there is a lack of experimental data on spontaneous imbibition and wettability in oil and gas reservoirs for the validation of further model development. In this work, we used neutron imaging to measure the spontaneous imbibition of water into fractures of Eagle Ford Shale with known geometries and fracture orientations. An analytical solution for a set of nonlinear second-order differential equations was applied to the measured imbibition data to determine effective contact angles. The analytical solution fit the measured imbibition data reasonably well and determined effective contact angles were slightly higher than static contact angles due to effects of in-situ changes in velocity, surface roughness, and heterogeneity of mineral surfaces on the fracture surface. Additionally, small fracture widths may have retarded imbibition and affected model fits, which suggests that average fracture widths are not satisfactory for modeling imbibition in natural systems.
Prajitno, D. H.; Trisnawan, V.; Syarif, D. G.
2017-05-01
The solid surface tension plays an important role in the heat and mass transfer system for heat exchanger equipment. In the nuclear power plant industry, the stainless steel AISI 316 and Zircalloy 4 have been used for long time as structure materials. The purpose of the experimental is to study solid state surface tension behavior by measure contact angle Nano fluid contain nano particle alumina on metal surface of stainless steel AISI 316 and Zircalloy 4 by sessile drop method. The experiment is to measure the static contact angle and drop nano fluid contains nano particle alumina on stainless steel 316 and zircalloy 4 with different spreading time from 1 to 30 minute. It was observed that stainless steel 316 and zircalloy 4 lose their hydrophobic properties with increasing elapsed time during drop of nano fluid on the surface of alloy. As a result the contact angle of nano fluid on surface of metal is decrease with increasing elapsed time. While the magnitude diameter of drop nano fluid and wetting surface is increase with increasing elapsed time on the surface of the stainless steel SS 316 and Zircalloy 4.
Directory of Open Access Journals (Sweden)
Jyh Jian Chen
2014-03-01
Full Text Available Filling of liquid samples is realized in a microfluidic device with applications including analytical systems, biomedical devices, and systems for fundamental research. The filling of a disk-shaped polydimethylsiloxane (PDMS microchamber by liquid is analyzed with reference to microstructures with inlets and outlets. The microstructures are fabricated using a PDMS molding process with an SU-8 mold. During the filling, the motion of the gas-liquid interface is determined by the competition among inertia, adhesion, and surface tension. A single ramp model with velocity-dependent contact angles is implemented for the accurate calculation of surface tension forces in a three-dimensional volume-of-fluid based model. The effects of the parameters of this functional form are investigated. The influences of non-dimensional parameters, such as the Reynolds number and the Weber number, both determined by the inlet velocity, on the flow characteristics are also examined. An oxygen-plasma-treated PDMS substrate is utilized, and the microstructure is modified to be hydrophilic. Flow experiments are conducted into both hydrophilic and hydrophobic PDMS microstructures. Under a hydrophobic wall condition, numerical simulations with imposed boundary conditions of static and dynamic contact angles can successfully predict the moving of the meniscus compared with experimental measurements. However, for a hydrophilic wall, accurate agreement between numerical and experimental results is obvious as the dynamic contact angles were implemented.
Soil-water contact angle of some soils of the Russian Plane
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
Malgarinos, Ilias; Nikolopoulos, Nikolaos; Marengo, Marco; Antonini, Carlo; Gavaises, Manolis
2014-10-01
In this study,a novel numerical implementation for the adhesion of liquid droplets impacting normally on solid dry surfaces is presented. The advantage of this new approach, compared to the majority of existing models, is that the dynamic contact angle forming during the surface wetting process is not inserted as a boundary condition, but is derived implicitly by the induced fluid flow characteristics (interface shape) and the adhesion physics of the gas-liquid-surface interface (triple line), starting only from the advancing and receding equilibrium contact angles. These angles are required in order to define the wetting properties of liquid phases when interacting with a solid surface. The physical model is implemented as a source term in the momentum equation of a Navier-Stokes CFD flow solver as an "adhesion-like" force which acts at the triple-phase contact line as a result of capillary interactions between the liquid drop and the solid substrate. The numerical simulations capture the liquid-air interface movement by considering the volume of fluid (VOF) method and utilizing an automatic local grid refinement technique in order to increase the accuracy of the predictions at the area of interest, and simultaneously minimize numerical diffusion of the interface. The proposed model is validated against previously reported experimental data of normal impingement of water droplets on dry surfaces at room temperature. A wide range of impact velocities, i.e. Weber numbers from as low as 0.2 up to 117, both for hydrophilic (θadv=10°-70°) and hydrophobic (θadv=105°-120°) surfaces, has been examined. Predictions include in addition to droplet spreading dynamics, the estimation of the dynamic contact angle; the latter is found in reasonable agreement against available experimental measurements. It is thus concluded that theimplementation of this model is an effective approach for overcoming the need of a pre-defined dynamic contact angle law, frequently adopted as
Cho, Hyun-Kyung; Kee, Changwon; Yang, Heon; Huh, Hyoun Do; Kim, Su Jin; Park, Young Min; Park, Jong Moon
2017-11-01
To compare the quantitative changes of peripheral angle after laser iridotomy (LI) alone (group A) or combined LI and Iridoplasty (group B) using iridotrabecular contact (ITC) index by swept-source anterior segment optical coherence tomography (AS-OCT). In this prospective comparative observational study, OCT images were obtained before and after the procedure. In each image frame, scleral spur (SS) and the ITC end point (EP) were marked and ITC index was calculated as a percentage of the angle closure from 360°. Age, gender, diagnosis and initial ITC index in Group B were matched with group A. Changes in ITC index, anterior chamber angle parameters, and intraocular pressure (IOP) were inspected. Thirty-three eyes (20 patients) with shallow anterior chamber were included in each group. Initial ITC index and initial IOP were not significantly different between the two groups (both p > 0.05). However, ITC index and IOP after the procedure were significantly lower in group B than those in group A (ITC index: 31.3 ± 23.2 in group A, 19.0 ± 21.3 in group B, p = 0.011, IOP: p = 0.004). All anterior chamber angle parameters in group B and all parameters in group A except nasal trabecular-iris angles (TIA) were significantly increased after the laser procedure (all p angle better than LI alone. Iridoplasty may be able to additionally relieve the peripheral angle closure caused by other mechanisms than pupillary block. © 2017 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.
Cho, Hyun-Kyung; Ahn, Dongsub; Kee, Changwon
2017-05-01
To investigate the quantitative changes of circumferential angle closure after laser iridotomy (LI) using the iridotrabecular contact (ITC) index by Swept-Source optical coherence tomography (OCT). In this prospective observational study conducted in a hospital setting, 42 eyes of 36 patients (five males, 31 females) who underwent LI were included. The mean age was 65.00 ± 8.13 years old and the diagnosis included primary angle closure (PAC, 21 eyes), PAC suspect (16 eyes) and PAC glaucoma (five eyes). Optical coherence tomography (OCT) images were obtained pre-LI and at 1 week post-LI. In each image frame, the scleral spur (SS) and the ITC end-point were marked, from which the ITC index was calculated as a percentage of the angle closure across 360°. Measurements inspected before and after LI included: central anterior chamber depth (ACD), anterior chamber volume (ACV), lens vault (LV), nasal and temporal angle opening distance (AOD), angle recess area (ARA), trabecular-iris space area (TISA), trabecular-iris angle (TIA) at 500 μm and 750 μm from the SS and intraocular pressure (IOP). The ITC index and IOP decreased significantly after LI from 71.52 ± 26.29 to 35.31 ± 27.19 and from 20.64 ± 12.72 mmHg to 14.02 ± 3.49 mmHg, respectively (p 0.05), but ACV increased significantly after LI (p angle parameters except for nasal TIAs increased significantly after LI (all p angle showed a significant decrease after LI, but part of the angle closure was not relieved after LI. Other mechanisms besides pupillary block may play a role together in causing angle closure. © 2016 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.
25G compared with 20G vitrectomy under Resight non-contact wide-angle lenses for Terson syndrome.
Mao, Xinbang; You, Zhipeng
2017-08-01
The aim of the present study was to compare the effectiveness of 25G vitrectomy to standard 20G vitrectomy for treatment of Terson syndrome under Resight non-contact wide-angle lenses. This was a case-control study of 20 patients with Terson syndrome (study group) that underwent 25G vitrectomy under Resight non-contact wide-angle lenses, with those of 20 matched patients that underwent 20G vitrectomy (control group). Medical records were reviewed from between July 2011 and October 2013. Data included results of the Early Treatment Diabetic Retinopathy Study examination, ophthalmology B-scan ultrasonography and fundus photography. The mean age, follow-up time, the preoperative visual acuity of LogMAR and the preoperative intraocular pressure (IOP) were all comparable in the two groups (all P>0.05). There were statistically significant differences in postoperative visual acuity of LogMAR compared with preoperative visual acuity (Pcontact wide-angle lenses can achieve a significantly shorter operative time and lower post-operative IOP compared with 20G Vitrectomy.
How Does a Liquid Wet a Solid? Hydrodynamics of Dynamic Contact Angles
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.
Directory of Open Access Journals (Sweden)
Danuta Szyszka
2016-01-01
Full Text Available This paper describes the measurement of contact angle of copper-bearing shales. The values of advancing and receding contact angles were determined using the sessile drop and captive bubble methods in the presence of aqueous solutions of acetal and pyridine and distilled water. Both methods demonstrated that the tested substances had only minor impact on the surface hydrophobicity of copper-bearing shales expressed by contact angle. The tests carried out proved that neither acetal nor pyridine may be classified to the collecting reagents because none of them improves hydrophobicity of copper-bearing shales. These reagents are only flotation frothers.
Pogorzelski, Stanisław J.; Rochowski, Pawel; Szurkowski, Janusz
2014-02-01
An investigation of water contact angles (CAs), contact angle hysteresis (CAH) was carried out for 1-year to 4-year old needles (Pinus sylvestris) collected in urban (Gdansk) and rural (Karsin) locations using an original measuring technique based on the geometry of the drop on a vertical filament. Concentrations of air pollutants (SO2, NOx, C6H6, and suspended particular matter - SPM) currently considered to be most important in causing direct damage to vegetation were simultaneously monitored. A set of the surface wettability parameters: the apparent surface free energy γSV, adhesive film tension Π, work of adhesion WA, and spreading WS, were determined from CAH data using the approach developed by Chibowski (2003) to quantify the surface energetics of the needle substrata affected by aging and pollution impacts. This formalism relates the total apparent surface free energy of the solid γSV with only three measurable quantities: the surface tension of the probe liquid γLV and its advancing θA and receding θR contact angle hysteresis. Since CAH depends on the outermost wax layer surface roughness and spatial physicochemical heterogeneity of a solid surface, CA data were corrected using surface architecture profiles registered with confocal scanning laser microscopy. It was found that the roughness parameter r is significantly negatively correlated (R = -0.74) with the needle age (collected at Karsin). The needle surface aging process resulted in its surface hydrophilization (CA↓ and CAH↓ with γSV↑ and WA↑). A temporal evolution of the needles wettability was traced with the data point distribution in the 2D space of CAH plotted versus WS. The wettability parameters were closely correlated to pollutant concentrations as evidenced from Spearman's rank correlation procedure (R = 0.63-0.91; p biological systems.
Jo, Jaehyuck; Moon, Byung Gil; Lee, Joo Yong
2017-12-01
To report the outcome of scleral buckling using a non-contact wide-angle viewing system with a 25-gauge chandelier endoilluminator. Retrospective analyses of medical records were performed for 17 eyes of 16 patients with primary rhegmatogenous retinal detachment (RRD) without proliferative vitreoretinopathy who had undergone conventional scleral buckling with cryoretinopexy using the combination of a non-contact wide-angle viewing system and chandelier endoillumination. The patients were eight males and five females with a mean age of 26.8 ± 10.2 (range, 11 to 47) years. The mean follow-up period was 7.3 ± 3.1 months. Baseline best-corrected visual acuity was 0.23 ± 0.28 logarithm of the minimum angle of resolution units. Best-corrected visual acuity at the final visit showed improvement (0.20 ± 0.25 logarithm of the minimum angle of resolution units), but the improvement was not statistically significant (p = 0.722). As a surgery-related complication, there was vitreous loss at the end of surgery in one eye. As a postoperative complication, increased intraocular pressure (four cases) and herpes simplex epithelial keratitis (one case) were controlled postoperatively with eye drops. One case of persistent RRD after primary surgery needed additional vitrectomy, and the retina was postoperatively attached. Scleral buckling with chandelier illumination as a surgical technique for RRD has the advantages of relieving the surgeon's neck pain from prolonged use of the indirect ophthalmoscope and sharing the surgical procedure with another surgical team member. In addition, fine retinal breaks that are hard to identify using an indirect ophthalmoscope can be easily found under the microscope by direct endoillumination. © 2017 The Korean Ophthalmological Society
DEFF Research Database (Denmark)
Subedi, Shaphal; Kawamoto, Ken; Komatsu, Toshiko
2013-01-01
with water, eventually allowing water imbibition. However, the effect of the reduction in CA with soil-water contact time on the water retention function of hydrophobic media is not yet fully understood. In this study, water retention characteristics were measured using a hanging water column apparatus...... retention curves. For both water-repellent VAS and hydrophobized sand samples, the calculated CA–SWRC increased with increasing WR. This was determined from both the water drop penetration time and the initial contact angle (CAi) by the sessile drop method. Calculated CA–SWRC values ranged from 20° to 48......-filled pore distributions under controlled wetting and drying cycles was found on calculating the soil water capacity and pore size density as a function of water potential....
Choi, Eunsuk; Sul, Onejae; Lee, Seung-Beck
2017-09-06
In this article, we report on a flexible sensor based on a sandpaper molded elastomer that simultaneously detects planar displacement, rotation angle, and vertical contact pressure. When displacement, rotation, and contact pressure are applied, the contact area between the translating top elastomer electrode and the stationary three bottom electrodes change characteristically depending on the movement, making it possible to distinguish between them. The sandpaper molded undulating surface of the elastomer reduces friction at the contact allowing the sensor not to affect the movement during measurement. The sensor showed a 0.25 mm −1 displacement sensitivity with a ±33 μm accuracy, a 0.027 degree −1 of rotation sensitivity with ~0.95 degree accuracy, and a 4.96 kP −1 of pressure sensitivity. For possible application to joint movement detection, we demonstrated that our sensor effectively detected the up-and-down motion of a human forefinger and the bending and straightening motion of a human arm.
Langohr, G Daniel G; Willing, Ryan; Medley, John B; Athwal, George S; Johnson, James A
2016-04-01
Implant design parameters can be changed during reverse shoulder arthroplasty (RSA) to improve range of motion and stability; however, little is known regarding their impact on articular contact mechanics. The purpose of this finite element study was to investigate RSA contact mechanics during abduction for different neck-shaft angles, glenosphere sizes, and polyethylene cup depths. Finite element RSA models with varying neck-shaft angles (155°, 145°, 135°), sizes (38 mm, 42 mm), and cup depths (deep, normal, shallow) were loaded with 400 N at physiological abduction angles. The contact area and maximum contact stress were computed. The contact patch and the location of maximum contact stress were typically located inferomedially in the polyethylene cup. On average for all abduction angles investigated, reducing the neck-shaft angle reduced the contact area by 29% for 155° to 145° and by 59% for 155° to 135° and increased maximum contact stress by 71% for 155° to 145° and by 286% for 155° to 135°. Increasing the glenosphere size increased the contact area by 12% but only decreased maximum contact stress by 2%. Decreasing the cup depth reduced the contact area by 40% and increased maximum contact stress by 81%, whereas increasing the depth produced the opposite effect (+52% and -36%, respectively). The location of the contact patch and maximum contact stress in this study matches the area of damage seen frequently on clinical retrievals. This finding suggests that damage to the inferior cup due to notching may be potentiated by contact stresses. Increasing the glenosphere diameter improved the joint contact area and did not affect maximum contact stress. However, although reducing the neck-shaft angle and cup depth can improve range of motion, our study shows that this also has some negative effects on RSA contact mechanics, particularly when combined. Copyright © 2016 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc
A Facile All-Solution-Processed Surface with High Water Contact Angle and High Water Adhesive Force.
Chen, Mei; Hu, Wei; Liang, Xiao; Zou, Cheng; Li, Fasheng; Zhang, Lanying; Chen, Feiwu; Yang, Huai
2017-07-12
A series of sticky superhydrophobicity surfaces with high water contact angle and high water adhesive force is facilely prepared via an all-solution-processed method based on polymerization-induced phase separation between liquid crystals (LCs) and epoxy resin, which produces layers of epoxy microspheres (EMSs) with nanofolds on the surface of a substrate. The morphologies and size distributions of EMSs are confirmed by scanning electron microscopy. Results reveal that the obtained EMS coated-surface exhibits high apparent contact angle of 152.0° and high water adhesive force up to 117.6 μN. By varying the composition of the sample or preparing conditions, the sizes of the produced EMSs can be artificially regulated and, thus, control the wetting properties and water adhesive behaviors. Also, the sticky superhydrophobic surface exhibits excellent chemical stability, as well as long-term durability. Water droplet transportation experiments further prove that the as-made surface can be effectively used as a mechanical hand for water transportation applications. Based on this, it is believed that the simple method proposed in this paper will pave a new way for producing a sticky superhydrophobic surface and obtain a wide range of use.
Energy Technology Data Exchange (ETDEWEB)
Belibel, R.; Avramoglou, T. [INSERM U1148, Laboratory for Vascular Translational Science (LVTS), Institut Galilée, Université Paris 13, Sorbonne Paris Cité, 99 Avenue Jean-Baptiste Clément, Villetaneuse F-93430 (France); Garcia, A. [CNRS UPR 3407, Laboratoire des Sciences des Procédés et des Matériau, Institut Galilée, Université Paris 13, Sorbonne Paris Cité, 99 Avenue Jean-Baptiste Clément, Villetaneuse F-93430 (France); Barbaud, C. [INSERM U1148, Laboratory for Vascular Translational Science (LVTS), Institut Galilée, Université Paris 13, Sorbonne Paris Cité, 99 Avenue Jean-Baptiste Clément, Villetaneuse F-93430 (France); Mora, L., E-mail: Laurence.mora@univ-paris13.fr [INSERM U1148, Laboratory for Vascular Translational Science (LVTS), Institut Galilée, Université Paris 13, Sorbonne Paris Cité, 99 Avenue Jean-Baptiste Clément, Villetaneuse F-93430 (France)
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. - Highlights: • We develop different polymers with various chemical compositions. • Wettability properties were calculated using Cassie corrected contact angles. • Percentage of acid groups in polymers is directly correlated to acid part of SFE. • Cassie corrections are necessary for heterogeneous polymers.
Nikhil, Vineeta; Jaiswal, Shikha; Bajpai, Gauravi
2018-01-01
The purpose of this study was evaluation and comparison of the contact angle of new root canal sealers - Hybrid Root Seal, mineral trioxide aggregate (MTA) Plus, and the conventional AH Plus sealer with dentin and gutta-percha. Two groups (Group D - dentin and Group G - gutta-percha) of 18 samples each were further randomly divided into 3 subgroups based on the type of sealer used, that is, AH Plus, Hybrid Root Seal, and MTA Plus. Contact angle measurement device (Phoenix 300) was used to measure the contact angle of the sealers on both dentin and gutta-percha. The results thus obtained were analyzed using one-way analysis of variance and Student's t -test. MTA Plus recorded significantly higher values of contact angle on both the substrates, that is, dentin and gutta-percha when compared to AH Plus and Hybrid root canal sealer. The lowest value of contact angle in gutta-percha and dentin was shown by Hybrid root canal sealer and AH Plus, respectively. Both AH Plus and Hybrid Root Seal exhibited lower contact angle values, and hence, better wettability on both dentin and gutta-percha as compared to MTA Plus.
Mohan, Rayapudi Phani; Pai, Annappa Raghavendra Vivekananda
2015-01-01
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. 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. 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 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.
International Nuclear Information System (INIS)
Al-Yaseri, Ahmed Z.; Lebedev, Maxim; Barifcani, Ahmed; Iglauer, Stefan
2016-01-01
Highlights: • (Water + CO_2) contact angle on quartz increases substantially with pressure and salinity. • (Water + CO_2) contact angle on quartz increases slightly with temperature. • Surface roughness has only a minor influence on (water + CO_2 + quartz) contact angles. - Abstract: The wetting characteristics of CO_2 in rock are of vital importance in carbon geo-storage as they determine fluid dynamics and storage capacities. However, the current literature data has a high uncertainty, which translates into uncertain predictions in terms of containment security and economic project feasibility. We thus measured contact angles for the CO_2/water/quartz system at relevant reservoir conditions, and analysed the effects of pressure (0.1 to 20) MPa, temperature (296 to 343) K, surface roughness (56 to 1300) nm, salt type (NaCl, CaCl_2, and MgCl_2) and brine salinities (0 to 35) wt%. Water contact angles decreased with surface roughness, but increased with pressure, temperature, and brine salinity. Overall the contact angles were significantly increased at storage conditions (∼50°) when compared to ambient conditions (always 0°). Consequently quartz is weakly water-wet (not completely water-wet) at storage conditions, and structural and residual trapping capacities are reduced accordingly.
International Nuclear Information System (INIS)
Heib, F.; Hempelmann, R.; Munief, W.M.; Ingebrandt, S.; Fug, F.; Possart, W.; Groß, K.; Schmitt, M.
2015-01-01
Highlights: • Analysis of the triple line motion on surfaces with nanoscale surface topographies. • Analysis of the triple line motion is performed in sub-pixel resolution. • A special fitting and statistical approach for contact angle analysis is applied. • The analyses result set of contact angle data which is independent of “user-skills”. • Characteristically density distributions in dependence on the surface properties. - Abstract: 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 θ a and the receding θ r 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
Energy Technology Data Exchange (ETDEWEB)
Heib, F., E-mail: f.heib@mx.uni-saarland.de [Department of Physical Chemistry, Saarland University, 66123 Saarbrücken (Germany); Hempelmann, R. [Department of Physical Chemistry, Saarland University, 66123 Saarbrücken (Germany); Munief, W.M.; Ingebrandt, S. [Department of Informatics and Microsystem Technology, University of Applied Sciences, Kaiserslautern, 66482 Zweibrücken (Germany); Fug, F.; Possart, W. [Department of Adhesion and Interphases in Polymers, Saarland University, 66123 Saarbrücken (Germany); Groß, K.; Schmitt, M. [Department of Physical Chemistry, Saarland University, 66123 Saarbrücken (Germany)
2015-07-01
Highlights: • Analysis of the triple line motion on surfaces with nanoscale surface topographies. • Analysis of the triple line motion is performed in sub-pixel resolution. • A special fitting and statistical approach for contact angle analysis is applied. • The analyses result set of contact angle data which is independent of “user-skills”. • Characteristically density distributions in dependence on the surface properties. - Abstract: 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 θ{sub a} and the receding θ{sub r} 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
Huang, Yan-Ming; Yan, Hua; Cai, Jin-Hong; Li, Hai-Bo
2017-01-01
To introduce a novel approach in removal of anterior chamber angle foreign body (ACFB) using a prism contact lens and 23-gauge foreign body forceps. Data of 42 eyes of 42 patients who had undergone removal of ACFB using a prism contact lens and 23-gauge foreign body forceps from January 2008 to October 2013 were collected and analyzed. Twenty eyes in group A received the conventional approach by using toothed forceps through corneal limbus incision, and 22 eyes in group B underwent the novel method through the opposite corneal limbus incision. The success rate of ACFB once removal was 75% (15/20) in group A, and 100% (22/22) in group B. The average operation time of group A was significantly longer compared with group B (34.9±9.88min vs 22.13±8.85min; P contact lens and 23-gauge foreign body forceps is a safer, more effective, and convenient technique compared with the conventional approach.
Koishi, Takahiro; Yasuoka, Kenji; Fujikawa, Shigenori; Zeng, Xiao Cheng
2011-09-27
We perform large-scale molecular dynamics simulations to measure the contact-angle hysteresis for a nanodroplet of water placed on a nanopillared surface. The water droplet can be in either the Cassie state (droplet being on top of the nanopillared surface) or the Wenzel state (droplet being in contact with the bottom of nanopillar grooves). To measure the contact-angle hysteresis in a quantitative fashion, the molecular dynamics simulation is designed such that the number of water molecules in the droplets can be systematically varied, but the number of base nanopillars that are in direct contact with the droplets is fixed. We find that the contact-angle hysteresis for the droplet in the Cassie state is weaker than that in the Wenzel state. This conclusion is consistent with the experimental observation. We also test a different definition of the contact-angle hysteresis, which can be extended to estimate hysteresis between the Cassie and Wenzel state. The idea is motivated from the appearance of the hysteresis loop typically seen in computer simulation of the first-order phase transition, which stems from the metastability of a system in different thermodynamic states. Since the initial shape of the droplet can be controlled arbitrarily in the computer simulation, the number of base nanopillars that are in contact with the droplet can be controlled as well. We show that the measured contact-angle hysteresis according to the second definition is indeed very sensitive to the initial shape of the droplet. Nevertheless, the contact-angle hystereses measured based on the conventional and new definition seem converging in the large droplet limit. © 2011 American Chemical Society
Li, Caoxiong; Shen, Yinghao; Ge, Hongkui; Zhang, Yanjun; Liu, Tao
2018-03-02
Shales have abundant micro-nano pores. Meanwhile, a considerable amount of fracturing liquid is imbibed spontaneously in the hydraulic fracturing process. The spontaneous imbibition in tortuous micro-nano pores is special to shale, and dynamic contact angle and slippage are two important characteristics. In this work, we mainly investigate spontaneous imbibition considering dynamic contact angle and slip effect in fractal tortuous capillaries. We introduce phase portrait analysis to analyse the dynamic state and stability of imbibition. Moreover, analytical solutions to the imbibition equation are derived under special situations, and the solutions are verified by published data. Finally, we discuss the influences of slip length, dynamic contact angle and gravity on spontaneous imbibition. The analysis shows that phase portrait is an ideal tool for analysing spontaneous imbibition because it can evaluate the process without solving the complex governing ordinary differential equations. Moreover, dynamic contact angle and slip effect play an important role in fluid imbibition in fractal tortuous capillaries. Neglecting slip effect in micro-nano pores apparently underestimates imbibition capability, and ignoring variations in contact angle causes inaccuracy in predicting imbibition speed at the initial stage of the process. Finally, gravity is one of the factors that control the stabilisation of the imbibition process.
McClements, Jake; Buffone, Cosimo; Shaver, Michael P; Sefiane, Khellil; Koutsos, Vasileios
2017-09-20
The self-assembly of poly(styrene-co-butadiene) random copolymers on mica surfaces was studied by varying solution concentrations and polymer molecular weights. Toluene solutions of the poly(styrene-co-butadiene) samples were spin coated onto a mica surface and the resulting polymer morphology was investigated by atomic force microscopy. At higher concentrations, thin films formed with varying thicknesses; some dewetting was observed which depended on the molecular weight. Total dewetting did not occur despite the polymer's low glass transition temperature. Instead, partial dewetting was observed suggesting that the polymer was in a metastable equilibrium state. At lower concentrations, spherical cap shaped nanodroplets formed with varying sizes from single polymer chains to aggregates containing millions of chains. As the molecular weight was increased, fewer aggregates were observed on the surface, albeit with larger sizes resulting from increased solution viscosities and more chain entanglements at higher molecular weights. The contact angles of the nanodroplets were shown to be size dependent. A minimum contact angle occurs for droplets with radii of 100-250 nm at each molecular weight. Droplets smaller than 100 nm showed a sharp increase in contact angle; attributed to an increase in the elastic modulus of the droplets, in addition, to a positive line tension value. Droplets larger than 250 nm also showed an increased contact angle due to surface heterogeneities which cannot be avoided for larger droplets. This increase in contact angle plateaus as the droplet size reaches the macroscopic scale.
Canonical ensembles and nonzero density quantum chromodynamics
International Nuclear Information System (INIS)
Hasenfratz, A.; Toussaint, D.
1992-01-01
We study QCD with nonzero chemical potential on 4 4 lattices by averaging over the canonical partition functions, or sectors with fixed quark number. We derive a condensed matrix of size 2x3xL 3 whose eigenvalues can be used to find the canonical partition functions. We also experiment with a weight for configuration generation which respects the Z(3) symmetry which forces the canonical partition function to be zero for quark numbers that are not multiples of three. (orig.)
Motion of particles of non-zero rest masses exterior to ...
African Journals Online (AJOL)
In this article, we extend the metric tensor exterior to astrophysically real or imaginary spherical distributions of mass whose tensor field varies with polar angle only; to derive equations of motion for test particles in this field. The time, radial, polar and azimuthal equations of motion for particles of non-zero rest masses moving ...
Schmitt, Michael; Heib, Florian
2013-10-07
Drop shape analysis is one of the most important and frequently used methods to characterise surfaces in the scientific and industrial communities. An especially large number of studies, which use contact angle measurements to analyse surfaces, are characterised by incorrect or misdirected conclusions such as the determination of surface energies from poorly performed contact angle determinations. In particular, the characterisation of surfaces, which leads to correlations between the contact angle and other effects, must be critically validated for some publications. A large number of works exist concerning the theoretical and thermodynamic aspects of two- and tri-phase boundaries. The linkage between theory and experiment is generally performed by an axisymmetric drop shape analysis, that is, simulations of the theoretical drop profiles by numerical integration onto a number of points of the drop meniscus (approximately 20). These methods work very well for axisymmetric profiles such as those obtained by pendant drop measurements, but in the case of a sessile drop onto real surfaces, additional unknown and misunderstood effects on the dependence of the surface must be considered. We present a special experimental and practical investigation as another way to transition from experiment to theory. This procedure was developed to be especially sensitive to small variations in the dependence of the dynamic contact angle on the surface; as a result, this procedure will allow the properties of the surface to be monitored with a higher precession and sensitivity. In this context, water drops onto a 111 silicon wafer are dynamically measured by video recording and by inclining the surface, which results in a sequence of non-axisymmetric drops. The drop profiles are analysed by commercial software and by the developed and presented high-precision drop shape analysis. In addition to the enhanced sensitivity for contact angle determination, this analysis technique, in
Shojai Kaveh, Narjes; Rudolph, E Susanne J; Wolf, Karl-Heinz A A; Ashrafizadeh, Seyed Nezameddin
2011-12-01
Geological sequestration of pure carbon dioxide (CO(2)) in coal is one of the methods to sequester CO(2). In addition, injection of CO(2) or flue gas into coal enhances coal bed methane production (ECBM). The success of this combined process depends strongly on the wetting behavior of the coal, which is function of coal rank, ash content, heterogeneity of the coal surface, pressure, temperature and composition of the gas. The wetting behavior can be evaluated from the contact angle of a gas bubble, CO(2) or flue gas, on a coal surface. In this study, contact angles of a synthetic flue gas, i.e. a 80/20 (mol%) N(2)/CO(2) mixture, and pure CO(2) on a Warndt Luisenthal (WL) coal have been determined using a modified pendant drop cell in a pressure range from atmospheric to 16 MPa and a constant temperature of 318 K. It was found that the contact angles of flue gas on WL coal were generally smaller than those of CO(2). The contact angle of CO(2) changes from water-wet to gas-wet by increasing pressure above 8.5 MPa while the one for the flue gas changes from water-wet to intermediate-wet by increasing pressure above 10 MPa. Copyright © 2011 Elsevier Inc. All rights reserved.
Lorbach, Olaf; Zumbansen, Nikolaus; Kieb, Matthias; Efe, Turgay; Pizanis, Antonius; Kohn, Dieter; Haupert, Alexander
2018-04-01
Objective evaluation of the optimal graft tension angle to fully restore patellofemoral contact pressure in reconstruction of the medial patellofemoral ligament (MPFL) in comparison to the native knee. Twelve cadaveric knee specimens were fixed in a custom-made fixation device. A sensitive pressure film (Tekscan) was fixed in the patellofemoral joint, and patellofemoral contact pressure was assessed during a dynamic flexion movement from 0° to 90°. The MPFL was cut and measurements were repeated. Reconstruction of the MPFL was performed with the gracilis tendon subsequently fixed in the femur at 15°, 30°, 45°, 60°, 75°, and 90° of knee flexion under controlled tension (2 N). The sequence of the flexion angles was alternated. Pressure measurements were repeated after every fixation of the graft. No significant differences were seen in the overall patellofemoral contact pressure compared to the native knee (P > .05). However, medial patellofemoral pressure showed a significant increased patellofemoral contact pressure after MPFL reconstruction at a knee flexion angle during graft fixation of 15° (P = .027), 45° (P = .050, P = .044), and 75° (P = .039). Moreover, proximal/distal patellofemoral contact pressure revealed a significantly reduced contact pressure at 15° (P = .003), 30° (P = .009), 45° (P = .025), 75° (P = .021), and 90° (P = .022) of flexion distal after MPFL reconstruction compared with the intact knee. Lateral patellofemoral contact pressure was significantly reduced in all performed reconstructions (P angle during graft fixation for MPFL reconstruction did not have a significant impact on the overall patellofemoral contact pressure. However, selective medial, proximal, distal, and lateral patellofemoral contact pressure was significantly altered for all reconstructions. Fixation of the MPFL graft at 60° of flexion was able to most closely restore patellofemoral contact pressure compared with the intact knee. Based on the
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. Copyright © 2014 Elsevier B.V. All rights reserved.
Lee, Jinkyu; Song, Yongnam; Shin, Choongsoo S
2018-05-01
During landing, the ankle angle at initial contact (IC) exhibits relatively wide individual variation compared to the knee and hip angles. However, little is known about the effect of different IC ankle angles on energy dissipation. The purpose of this study was to investigate the relationship between individual ankle angles at IC and energy dissipation in the lower extremity joints. Twenty-seven adults performed single-leg landings from a 0.3-m height. Kinetics and kinematics of the lower extremity joints were measured. The relationship between ankle angles at IC and negative work, range of motion, the time to peak ground reaction force, and peak loading rate were analyzed. The ankle angle at IC was positively correlated with ankle negative work (r = 0.80, R 2 = 0.64, p angle was negatively correlated with hip negative work (r = -0.46, R 2 = 0.21, p = 0.01) and the contribution of the hip to total negative work (r = -0.61, R 2 = 0.37, p angle at IC. The ankle angle at IC was positively correlated with total negative work (r = 0.50, R 2 = 0.25, p angle at IC increased, such that the ankle energy dissipation increased and redistributed the energy dissipation in the ankle and hip joints. Further, these results suggest that increased ankle energy dissipation with a higher IC plantar flexion angle may be a potential landing technique for reducing the risk of injury to the anterior cruciate ligament and hip musculature. Copyright © 2018 Elsevier B.V. All rights reserved.
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
Scanziani, Alessio; Singh, Kamaljit; Blunt, Martin J; Guadagnini, Alberto
2017-06-15
Multiphase flow in porous media is strongly influenced by the wettability of the system, which affects the arrangement of the interfaces of different phases residing in the pores. We present a method for estimating the effective contact angle, which quantifies the wettability and controls the local capillary pressure within the complex pore space of natural rock samples, based on the physical constraint of constant curvature of the interface between two fluids. This algorithm is able to extract a large number of measurements from a single rock core, resulting in a characteristic distribution of effective in situ contact angle for the system, that is modelled as a truncated Gaussian probability density distribution. The method is first validated on synthetic images, where the exact angle is known analytically; then the results obtained from measurements within the pore space of rock samples imaged at a resolution of a few microns are compared to direct manual assessment. Finally the method is applied to X-ray micro computed tomography (micro-CT) scans of two Ketton cores after waterflooding, that display water-wet and mixed-wet behaviour. The resulting distribution of in situ contact angles is characterized in terms of a mixture of truncated Gaussian densities. Crown Copyright © 2017. Published by Elsevier Inc. All rights reserved.
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
Directory of Open Access Journals (Sweden)
Mohammad-Reza Ahmadian-Yazdi
2018-02-01
Full Text Available Perovskite solar cells (PSCs are currently under vigorous research and development, owing to their compelling power conversion efficiencies. PSCs are solution-processed and, therefore, are fabricated using casting and printing methods, such as spin, spray and blade coating. The coating characteristics significantly depend on the physical and rheological properties of the solutions. Thus, due to the scarcity of such properties, in this work, we report the surface tension, viscosity, density, and contact angle of selected methylammonium lead halide perovskite solutions, in order to gain insight into the behavior of the perovskite solutions and the range of such physical properties. The contact angles were measured on PEDOT:PSS and compact TiO2 (c-TiO2 substrates, commonly used as the underneath layers of the perovskite film. In total, 12 solutions of CH3NH3PbI3 and CH3NH3PbI3-xClx dissolved in common solvents, as well as solutions of PbI2, PbCl2, and CH3NH3I were tested. Among the results, it is shown that the tested perovskite solutions are Newtonian, the apparent contact angles on the mesoporous TiO2 (m-TiO2 are close to zero, on the PEDOT:PSS are around 10°, and on the c-TiO2 are around 30°. Also, contact angle hysteresis is observed in the case of the c-TiO2 substrates. Representative impact dynamics and spreading of perovskite solution droplets are also studied, to demonstrate the importance of the solution properties and process parameters on the coating process.
Ahmadian-Yazdi, Mohammad-Reza; Rahimzadeh, Amin; Chouqi, Zineb; Miao, Yihe; Eslamian, Morteza
2018-02-01
Perovskite solar cells (PSCs) are currently under vigorous research and development, owing to their compelling power conversion efficiencies. PSCs are solution-processed and, therefore, are fabricated using casting and printing methods, such as spin, spray and blade coating. The coating characteristics significantly depend on the physical and rheological properties of the solutions. Thus, due to the scarcity of such properties, in this work, we report the surface tension, viscosity, density, and contact angle of selected methylammonium lead halide perovskite solutions, in order to gain insight into the behavior of the perovskite solutions and the range of such physical properties. The contact angles were measured on PEDOT:PSS and compact TiO2 (c-TiO2) substrates, commonly used as the underneath layers of the perovskite film. In total, 12 solutions of CH3NH3PbI3 and CH3NH3PbI3-xClx dissolved in common solvents, as well as solutions of PbI2, PbCl2, and CH3NH3I were tested. Among the results, it is shown that the tested perovskite solutions are Newtonian, the apparent contact angles on the mesoporous TiO2 (m-TiO2) are close to zero, on the PEDOT:PSS are around 10°, and on the c-TiO2 are around 30°. Also, contact angle hysteresis is observed in the case of the c-TiO2 substrates. Representative impact dynamics and spreading of perovskite solution droplets are also studied, to demonstrate the importance of the solution properties and process parameters on the coating process.
Large Nc QCD at nonzero chemical potential
International Nuclear Information System (INIS)
Cohen, Thomas D.
2004-01-01
The general issue of large N c QCD at nonzero chemical potential is considered with a focus on understanding the difference between large N c QCD with an isospin chemical potential and large N c QCD with a baryon chemical potential. A simple diagrammatic analysis analogous to 't Hooft's analysis at μ=0 implies that the free energy with a given baryon chemical potential is equal to the free energy with an isospin chemical potential of the same value plus 1/N c corrections. Phenomenologically, these two systems behave quite differently. A scenario to explain this difference in light of the diagrammatic analysis is explored. This scenario is based on a phase transition associated with pion condensation when the isospin chemical potential exceeds m π /2; associated with this transition there is breakdown of the 1/N c expansion--in the pion condensed phase there is a distinct 1/N c expansion including a larger set of diagrams. While this scenario is natural, there are a number of theoretical issues which at least superficially challenge it. Most of these can be accommodated. However, the behavior of quenched QCD which raises a number of apparently analogous issues cannot be easily understood completely in terms of an analogous scenario. Thus, the overall issue remains open
Fu, Yi; Lau, Yiu-Ting R; Weng, Lu-Tao; Ng, Kai-Mo; Chan, Chi-Ming
2014-10-01
Poly (2, 3, 4, 5, 6-pentafluorostyrene) (5FPS) was prepared by bulk radical polymerization. The spin-cast films of this polymer were analyzed using time-of-flight secondary ion mass spectrometry (ToF-SIMS) at various temperatures ranging from room temperature to 120°C. Principal component analysis (PCA) of the ToF-SIMS data revealed a transition temperature (T(T)) at which the surface structure of 5FPS was rearranged. A comparison between the results of the PCA of ToF-SIMS spectra obtained on 5FPS and polystyrene (PS) indicate that the pendant groups of 5FPS and PS moved in exactly opposite directions as the temperature increased. More pendant groups of 5FPS and PS migrated from the bulk to the surface and verse versa, respectively, as the temperature increased. These results clearly support the view that the abrupt changes in the normalized principal component 1 value was caused by the surface reorientation of the polymers and not by a change in the ion fragmentation mechanism at temperatures above the T(T). Contact angle measurement, which is another extremely surface sensitive technique, was used to monitor the change in the surface tension as a function of temperature. A clear T(T) was determined by the contact angle measurements. The T(T) values determined by contact angle measurements and ToF-SIMS were very similar. Copyright © 2014 Elsevier Inc. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Pallas, Norman R., E-mail: Sam-7-iam@hotmail.com [BP Research Centre Warrensville, 4440 Warrensville Center Road, Cleveland, Ohio 44128 (United States)
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 T{sub c}. 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 T{sub w}, 2.12 K below T{sub c}. The contact angle vanishes at T{sub w}, scaling as cos θ ∼ |T − T{sub c}|{sup β{sub 1}−μ} for T < T{sub w} and cos θ = 1.0 for T{sub w} < T < T{sub c}. The experimental results give a value for β{sub 1} = 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.
McCarty, C A; Thomason, J J; Gordon, K; Hurtig, M; Bignell, W
2015-11-01
To add to the existing data on impact loading of the metacarpophalangeal (MCP) joint as a precursor to assessing the potential role of impact in joint disease. To examine the effect of impact loading on contact areas of the first phalanx (P1) and proximal sesamoids (PS) with the third metacarpal (McIII) under 3 hoof-strike conditions (toe-first, flat, heel-first). Randomised, repeated controlled experiment using cadaver material. Eight cadaver limbs were subjected to randomised, repeated controlled trials where the hoof was struck by a pendulum impact machine (impact velocity 3.55 m/s) under 3 strike conditions. Data from pressure sensitive film placed over medial and lateral McIII condyles and lateromedially across the dorsal aspect of McIII were quantified: total areas of P1 and PS contact (cm(2) ) at maximum recorded pressure; centroid locations of contact areas relative to the sagittal ridge (cm) and transverse ridge (cm) and dispersion of pixels (cm(4) ) for each McIII condyle (medial/lateral). The effect of the strike conditions on each variable were statistically tested using repeated-measures ANOVA (α = 0.05). Contact area between P1 and McIII condyles fell in well-defined areas bounded by the sagittal and transverse ridge, contact areas from PS were smaller and widely dispersed across McIII palmar border. Ratio of contact area of P1 to PS was 2.83 (Pcontact area (P>0.54) CONCLUSIONS: Contact at impact (primarily from P1 and distally situated on McIII), contrasts with contact areas at midstance from both P1 and PS, symmetrically placed. Under impact, the greatest contact area was on the dorsal aspect of the medial condyle and coincides with the area subjected to the greatest increase in subchondral bone stiffening in joint disease. © 2014 EVJ Ltd.
Non-zero total correlation means non-zero quantum correlation
International Nuclear Information System (INIS)
Li, Bo; Chen, Lin; Fan, Heng
2014-01-01
We investigated the super quantum discord based on weak measurements. The super quantum discord is an extension of the standard quantum discord defined by projective measurements and also describes the quantumness of correlations. We provide some equivalent conditions for zero super quantum discord by using quantum discord, classical correlation and mutual information. In particular, we find that the super quantum discord is zero only for product states, which have zero mutual information. This result suggests that non-zero correlations can always be detected using the quantum correlation with weak measurements. As an example, we present the assisted state-discrimination method.
Energy Technology Data Exchange (ETDEWEB)
Nickelsen, Simin; Moghadam, Afsaneh Dorri, E-mail: afsaneh@uwm.edu; Ferguson, J.B.; Rohatgi, Pradeep
2015-10-30
Graphical abstract: - Highlights: • Wetting behavior of four metallic materials as a function of surface roughness has been studied. • A model to predict the abrasive particle size and water/oil contact angles relationship is proposed. • Active wetting regime is determined in different materials using the proposed model. - Abstract: 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, R{sub f}, and fraction of solid/oil interface, ƒ{sub so}, 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.
Rouhiainen, H; Teräsvirta, M
1990-06-01
New equipment for measuring intraocular pressure have been introduced lately. One of these is the Keeler Pulsair non-contact tonometer which uses pressurized air in measurement. It is found to be safe and easy to use in practice, but it seems to give 1.5-2.0 mmHg lower reading than the Goldmann applanation tonometer. This was confirmed by the present study, where non-contact tonometry was controlled by applanation tonometry with a 2-3 week delay between the measurements. However, for screening procedures the accuracy of the apparatus can be considered as sufficient.
Zhu, Chongqin; Gao, Yurui; Li, Hui; Meng, Sheng; Li, Lei; Francisco, Joseph S; Zeng, Xiao Cheng
2016-11-15
Hydrophobicity of macroscopic planar surface is conventionally characterized by the contact angle of water droplets. However, this engineering measurement cannot be directly extended to surfaces of proteins, due to the nanometer scale of amino acids and inherent nonplanar structures. To measure the hydrophobicity of side chains of proteins quantitatively, numerous parameters were developed to characterize behavior of hydrophobic solvation. However, consistency among these parameters is not always apparent. Herein, we demonstrate an alternative way of characterizing hydrophobicity of amino acid side chains in a protein environment by constructing a monolayer of amino acids (i.e., artificial planar peptide network) according to the primary and the β-sheet secondary structures of protein so that the conventional engineering measurement of the contact angle of a water droplet can be brought to bear. Using molecular dynamics simulations, contact angles θ of a water nanodroplet on the planar peptide network, together with excess chemical potentials of purely repulsive methane-sized Weeks-Chandler-Andersen solute, are computed. All of the 20 types of amino acids and the corresponding planar peptide networks are studied. Expectedly, all of the planar peptide networks with nonpolar amino acids are hydrophobic due to θ [Formula: see text] 90°, whereas all of the planar peptide networks of the polar and charged amino acids are hydrophilic due to θ [Formula: see text] 90°. Planar peptide networks of the charged amino acids exhibit complete-wetting behavior due to θ [Formula: see text] 0°. This computational approach for characterization of hydrophobicity can be extended to artificial planar networks of other soft matter.
Energy Technology Data Exchange (ETDEWEB)
Shubina, V., E-mail: varvara.shubina2014@gmail.com [LUNAM Université, IFSTTAR, MAST, SMC, F-44340 Bouguenais (France); Gaillet, L. [LUNAM Université, IFSTTAR, MAST, SMC, F-44340 Bouguenais (France); Ababou-Girard, S. [Institut de Physique de Rennes, Département Matériaux et Nanosciences, UMR 6251 CNRS, Université Rennes 1, 35000 Rennes-Cedex (France); Gaudefroy, V. [LUNAM Université, IFSTTAR, MAST, SMC, F-44340 Bouguenais (France); Chaussadent, T.; Farças, F. [Université Paris-Est, IFSTTAR, MAST, CPDM, F-77447 Marne-la-Vallée (France); Meylheuc, T. [INRA, UMR1319 Micalis, F-78352 Jouy-en-Josas (France); AgroParisTech, UMR Micalis, F-78352 Jouy-en-Josas (France); Dagbert, C. [2 Chemin de la Grand’côte, 36270 Éguzon-Chantôme (France); Creus, J. [LaSIE, UMR7356, Université de La Rochelle, Pôle Sciences et Technologie, Bâtiment Marie Curie, Avenue Michel Crépeau, 17000 La Rochelle (France)
2015-10-01
Highlights: • Surface modifications to carbon steel surfaces due to the adsorption of a biosurfactant derived from Pseudomonas fluorescens bacteria cells were investigated using contact angle measurements (CAM) and X-ray photoelectron spectroscopy (XPS). • CAM allowed to establish an increase of electron-donating properties of steel surface due to the biosurfactant adsorption. • XPS demonstrated that biosurfactant molecules change the stoichiometry of mixted-oxide layer and the new outer layer mostly composed of magnetite. • Thickness and density of adsorbed biosurfactants layers were highlighted using a semiquantitative approach for 3 different concentrations of biomolecules. - Abstract: We investigated modifications to carbon steel surfaces due to the adsorption of a biosurfactant derived from Pseudomonas fluorescens bacteria cells using contact angle measurements (CAM) and X-ray photoelectron spectroscopy (XPS). After conditioning carbon steel in solutions with three different concentrations of biosurfactant molecules: 0.05, 0.3 and 1 g L{sup −1}, the average thickness of the biosurfactant layer on the carbon steel specimens was 7.9 ± 0.3, 12.1 ± 0.5 and 16.4 ± 0.7 Å, respectively. The biosurfactants changed the composition of both the Fe{sup 2+} and Fe{sup 3+} mixed-oxide layer and the outer layer, mostly composed of Fe{sup 3+} associated with magnetite. Contact angle measurements indicate decreased hydrophobic properties after the carbon steel was modified by biosurfactant. It was shown that the carbon steel surface free energy depends on the biosurfactant concentration, due to an acquisition of strong electron-donating properties.
International Nuclear Information System (INIS)
Shubina, V.; Gaillet, L.; Ababou-Girard, S.; Gaudefroy, V.; Chaussadent, T.; Farças, F.; Meylheuc, T.; Dagbert, C.; Creus, J.
2015-01-01
Highlights: • Surface modifications to carbon steel surfaces due to the adsorption of a biosurfactant derived from Pseudomonas fluorescens bacteria cells were investigated using contact angle measurements (CAM) and X-ray photoelectron spectroscopy (XPS). • CAM allowed to establish an increase of electron-donating properties of steel surface due to the biosurfactant adsorption. • XPS demonstrated that biosurfactant molecules change the stoichiometry of mixted-oxide layer and the new outer layer mostly composed of magnetite. • Thickness and density of adsorbed biosurfactants layers were highlighted using a semiquantitative approach for 3 different concentrations of biomolecules. - Abstract: We investigated modifications to carbon steel surfaces due to the adsorption of a biosurfactant derived from Pseudomonas fluorescens bacteria cells using contact angle measurements (CAM) and X-ray photoelectron spectroscopy (XPS). After conditioning carbon steel in solutions with three different concentrations of biosurfactant molecules: 0.05, 0.3 and 1 g L −1 , the average thickness of the biosurfactant layer on the carbon steel specimens was 7.9 ± 0.3, 12.1 ± 0.5 and 16.4 ± 0.7 Å, respectively. The biosurfactants changed the composition of both the Fe 2+ and Fe 3+ mixed-oxide layer and the outer layer, mostly composed of Fe 3+ associated with magnetite. Contact angle measurements indicate decreased hydrophobic properties after the carbon steel was modified by biosurfactant. It was shown that the carbon steel surface free energy depends on the biosurfactant concentration, due to an acquisition of strong electron-donating properties
Directory of Open Access Journals (Sweden)
Mehrdad Barekatain
2016-03-01
Full Text Available Introduction: The aim of this study was to investigate the effect of dentinal pretreatment on the static contact angle of a bonding agent as a measure of dentin surface wettability. Materials &Methods: Twenty mid-coronal dentin surfaces were prepared and randomly allocated to four groups (n=5 according to the priming solutions. All segments were etched with 35% phosphoric acid gel for 15 s, rinsed for 30 s and dried. Each group was rehydrated with 10 µL of distilled water, 0.2 % chlorhexidine, 70% ethanol and 5.25% Sodium Hypochlorite respectively and the excess solution was removed after 60 sec using an absorbent paper. Using a micro syringe, a droplet of the Adper Single Bond 2 was placed on each prepared surface. Then the profile and the static contact angle of the droplet were analyzed with a video-based optical contact angle measuring system. The statistical analysis was performed using One-way ANOVA and Dunnett’s t tests (p<0.05. Results: There was a statistically significant difference between the water and sodium hypochlorite groups which indicates the negative effect sodium hypochlorite may have on dentinal surface energy. (p=0.013. The differences between the water and ethanol groups (p=0.168 and between the water and chlorhexidine groups (p=0.665 were not significant. Conclusion: The use of 5.25% sodium hypochlorite as a priming solution in bonding procedure is not recommended. There is no improvement in dentinal surface wettability by using 70% ethanol or 0.2% chlorhexidine instead of water and the recommendation for use of any of the two should be based on other long-term or short-term effects they may have on the bonding procedure.
Deleurence, Rémi; Parneix, Caroline; Monteux, Cécile
2014-09-28
We investigate the stabilization of air-water interfaces by mixtures of negatively charged latex particles (sulfate polystyrene) and cationic surfactants (alkyl trimethylammonium bromides). First we report results concerning the binding of surfactant molecules to the latex particles. As the surfactant concentration increases, the charge of the particles reverses, from negative to positive, because CnTAB first binds electrostatically to the latex particles and then through hydrophobic interaction with the monolayer already adsorbed on the particles as well as directly with the hydrophobic surface of the latex. Over a large range of surfactant concentrations around the charge inversion, a strong flocculation is observed and 100 μm large aggregates form in the suspension. Unlike previous studies published on mixtures of inorganic particles with oppositely charged surfactants, we show that we can vary the sign of the zeta potential of the particles without changing the contact angle of the particles over a large range of surfactant concentrations. Indeed, the latex particles that we study are more hydrophobic than inorganic particles, hence adding moderate concentrations of the surfactant results in a weak variation of the contact angle while the charge of the particles can be reversed. This enables decoupling of the effect of zeta potential and contact angle on the interfacial properties of the mixtures. Our study shows that the contact angle and the charge of the particles are not sufficient parameters to control the foam properties, and the key-parameters are the flocculation state and the shear energy applied to produce the foam. Indeed, flocculated samples, whatever the sign of the zeta potential, enable production of a stable armour at the interface. The large aggregates do not adsorb spontaneously at the interface because of their large size, however when a large shear energy is used to produce the foam very stable foam is obtained, where particles are trapped
Dey, Tania; Naughton, Daragh
2017-05-01
Glass surface cleaning is the very first step in advanced coating deposition and it also finds use in conserving museum objects. However, most of the wet chemical methods of glass cleaning use toxic and corrosive chemicals like concentrated sulfuric acid (H 2 SO 4 ), piranha (a mixture of concentrated sulfuric acid and 30% hydrogen peroxide), and hydrogen fluoride (HF). On the other hand, most of the dry cleaning techniques like UV-ozone, plasma, and laser treatment require costly instruments. In this report, five eco-friendly wet chemical methods of glass cleaning were evaluated in terms of contact angle (measured by optical tensiometer), nano-scale surface roughness (measured by atomic force microscopy or AFM), and elemental composition (measured by energy dispersive x-ray spectroscopy or SEM-EDX). These glass cleaning methods are devoid of harsh chemicals and costly equipment, hence can be applied in situ in close proximity with plantation such as greenhouse or upon subtle objects such as museum artifacts. Out of these five methods, three methods are based on the chemical principle of chelation. It was found that the citric acid cleaning method gave the greatest change in contact angle within the hydrophilic regime (14.25° for new glass) indicating effective cleansing and the least surface roughness (0.178 nm for new glass) indicating no corrosive effect. One of the glass sample showed unique features which were traced backed to the history of the glass usage.
Directory of Open Access Journals (Sweden)
S. Dobbie
2010-01-01
Full Text Available 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 was observed that the spread in the onset relative humidities with respect to ice (RHi for Saharan dust particles varied 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 the spread in the onset RHi for the three Saharan dust samples were in agreement, the active fractions and nucleation time-lags calculated at various temperature and RHi conditions were found to differ. This could be due to the subtle variation in the elemental composition of the dust samples, and 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 on the nucleability parameter, contact angle that is widely used in ice cloud modeling. These calculations show that the surface irregularities can reduce the contact angle by approximately 10 degrees.
Energy Technology Data Exchange (ETDEWEB)
Felix, T., E-mail: tsfelix81@gmail.com [Chemistry Department, Federal University of Santa Catarina, Campus Trindade, 88040-900 Florianópolis, SC (Brazil); Cassini, F.A.; Benetoli, L.O.B. [Chemistry Department, Federal University of Santa Catarina, Campus Trindade, 88040-900 Florianópolis, SC (Brazil); Dotto, M.E.R. [Physics Department, Federal University of Santa Catarina, Campus Trindade, 88040-900 Florianópolis, SC (Brazil); Debacher, N.A. [Chemistry Department, Federal University of Santa Catarina, Campus Trindade, 88040-900 Florianópolis, SC (Brazil)
2017-05-01
Highlights: • Polymeric surfaces were etched using non-thermal plasma at different intensities. • Polymers of low mechanical hardness reached the saturation level faster. • A mathematical model based on scaling laws was proposed. - Abstract: The experiments presented in this communication have the purpose to elaborate an explanation for the morphological evolution of the growth of polymeric surfaces provided by the treatment of non-thermal plasma. According to the roughness analysis and the model proposed by scaling laws it is possible relate to a predictable or merely random effect. Polyethylene terephthalate (PET) and poly(etherether)ketone (PEEK) samples were exposed to a non-thermal plasma discharge and the resulting surfaces roughness were analyzed based on the measurements from contact angle, scanning electron microscopy and atomic force microscopy coupled with scaling laws analysis which can help to describe and understand the dynamic of formation of a wide variety of rough surfaces. The roughness, R{sub RMS} (RMS- Root Mean Square) values for polymer surface range between 19.8 nm and 110.9 nm. The contact angle and the AFM (Atomic Force Microscopy) measurements as a function of the plasma exposure time were in agreement with both polar and dispersive components according to the surface roughness and also with the morphology evaluated described by Wolf-Villain model, with proximate values of α between 0.91{sub (PET)} and 0.88{sub (PEEK)}, β = 0.25{sub (PET)} and z = 3,64{sub (PET)}.
Directory of Open Access Journals (Sweden)
2007-06-01
Full Text Available In this study, the surface characteristics of blends and composites of epoxy resin were investigated. Poly(styrene-co-acylonitrile (SAN was used to modify diglycedyl ether of bisphenol-A (DGEBA type epoxy resin cured with diamino diphenyl sulfone (DDS and the modified epoxy resin was used as the matrix for fibre reinforced composites (FRP’s. E-glass fibre was used as the fibre reinforcement. The scanning electron micrographs of the fractured surfaces of the blends and composites were analyzed. Morphological analysis revealed different morphologies such as dispersed, cocontinuous and phase-inverted structures for the blends. Contact angle studies were carried out using water and methylene iodide at room temperature. The solid surface energy was calculated using harmonic mean equations. Blending of epoxy resin increases its contact angle. The surface free energy, work of adhesion, interfacial free energy, spreading coefficient and Girifalco-Good’s interaction parameter were changed significantly in the case of blends and composites. The incorporation of thermoplastic and glass fibre reduces the wetting and hydrophilicity of epoxy resin.
International Nuclear Information System (INIS)
Diaz, M. Elena; Cerro, Ramon L.
2005-01-01
The effects of pH and counterions on the type of deposition of Langmuir-Blodgett (LB) arachidic acid films onto hydrophobic glass slides is revisited. Unusually large differences in contact angles and transfer ratios (TR) were observed for subphase containing 10 -4 M of zinc sulfate and 2.10 -4 M of cadmium chloride, respectively, for a wide range of pH. Variations in TR occur at the same pH for different subphase cations and at different pH for the same divalent cations. These large variations in dynamic contact angles and TR as a function of pH point to the crucial role of electrical double layer forces in LB deposition phenomena. Transitions from Y- to X-type deposition are reported for pH larger or smaller than the pK A of the fatty acid-subphase salt system. Experimental results are compared with data reported in literature showing Z- to Y-transitions at pH close to the pK A of docosanoic acid monolayers
Felix, T.; Cassini, F. A.; Benetoli, L. O. B.; Dotto, M. E. R.; Debacher, N. A.
2017-05-01
The experiments presented in this communication have the purpose to elaborate an explanation for the morphological evolution of the growth of polymeric surfaces provided by the treatment of non-thermal plasma. According to the roughness analysis and the model proposed by scaling laws it is possible relate to a predictable or merely random effect. Polyethylene terephthalate (PET) and poly(etherether)ketone (PEEK) samples were exposed to a non-thermal plasma discharge and the resulting surfaces roughness were analyzed based on the measurements from contact angle, scanning electron microscopy and atomic force microscopy coupled with scaling laws analysis which can help to describe and understand the dynamic of formation of a wide variety of rough surfaces. The roughness, RRMS (RMS- Root Mean Square) values for polymer surface range between 19.8 nm and 110.9 nm. The contact angle and the AFM (Atomic Force Microscopy) measurements as a function of the plasma exposure time were in agreement with both polar and dispersive components according to the surface roughness and also with the morphology evaluated described by Wolf-Villain model, with proximate values of α between 0.91(PET) and 0.88(PEEK), β = 0.25(PET) and z = 3,64(PET).
Park, Taehyung; Joo, Hyun-Woo; Kim, Gyeong-Yeong; Kim, Seunghee; Yoon, Sukhwan; Kwon, Tae-Hyuk
2017-01-01
Injecting and storing of carbon dioxide (CO 2 ) in deep geologic formations is considered as one of the promising approaches for geologic carbon storage. Microbial wettability alteration of injected CO 2 is expected to occur naturally by microorganisms indigenous to the geologic formation or microorganisms intentionally introduced to increase CO 2 storage capacity in the target reservoirs. The question as to the extent of microbial CO 2 wettability alteration under reservoir conditions still warrants further investigation. This study investigated the effect of a lipopeptide biosurfactant-surfactin, on interfacial tension (IFT) reduction and contact angle alteration in CO 2 /water/quartz systems under a laboratory setup simulating in situ reservoir conditions. The temporal shifts in the IFT and the contact angle among CO 2 , brine, and quartz were monitored for different CO 2 phases (3 MPa, 30°C for gaseous CO 2 ; 10 MPa, 28°C for liquid CO 2 ; 10 MPa, 37°C for supercritical CO 2 ) upon cultivation of Bacillus subtilis strain ATCC6633 with induced surfactin secretion activity. Due to the secreted surfactin, the IFT between CO 2 and brine decreased: from 49.5 to 30 mN/m, by ∼39% for gaseous CO 2 ; from 28.5 to 13 mN/m, by 54% for liquid CO 2 ; and from 32.5 to 18.5 mN/m, by ∼43% for supercritical CO 2 , respectively. The contact angle of a CO 2 droplet on a quartz disk in brine increased: from 20.5° to 23.2°, by 1.16 times for gaseous CO 2 ; from 18.4° to 61.8°, by 3.36 times for liquid CO 2 ; and from 35.5° to 47.7°, by 1.34 times for supercritical CO 2 , respectively. With the microbially altered CO 2 wettability, improvement in sweep efficiency of injected and displaced CO 2 was evaluated using 2-D pore network model simulations; again the increment in sweep efficiency was the greatest in liquid CO 2 phase due to the largest reduction in capillary factor. This result provides novel insights as to the role of naturally occurring biosurfactants in CO 2
Directory of Open Access Journals (Sweden)
Taehyung Park
2017-07-01
Full Text Available Injecting and storing of carbon dioxide (CO2 in deep geologic formations is considered as one of the promising approaches for geologic carbon storage. Microbial wettability alteration of injected CO2 is expected to occur naturally by microorganisms indigenous to the geologic formation or microorganisms intentionally introduced to increase CO2 storage capacity in the target reservoirs. The question as to the extent of microbial CO2 wettability alteration under reservoir conditions still warrants further investigation. This study investigated the effect of a lipopeptide biosurfactant—surfactin, on interfacial tension (IFT reduction and contact angle alteration in CO2/water/quartz systems under a laboratory setup simulating in situ reservoir conditions. The temporal shifts in the IFT and the contact angle among CO2, brine, and quartz were monitored for different CO2 phases (3 MPa, 30°C for gaseous CO2; 10 MPa, 28°C for liquid CO2; 10 MPa, 37°C for supercritical CO2 upon cultivation of Bacillus subtilis strain ATCC6633 with induced surfactin secretion activity. Due to the secreted surfactin, the IFT between CO2 and brine decreased: from 49.5 to 30 mN/m, by ∼39% for gaseous CO2; from 28.5 to 13 mN/m, by 54% for liquid CO2; and from 32.5 to 18.5 mN/m, by ∼43% for supercritical CO2, respectively. The contact angle of a CO2 droplet on a quartz disk in brine increased: from 20.5° to 23.2°, by 1.16 times for gaseous CO2; from 18.4° to 61.8°, by 3.36 times for liquid CO2; and from 35.5° to 47.7°, by 1.34 times for supercritical CO2, respectively. With the microbially altered CO2 wettability, improvement in sweep efficiency of injected and displaced CO2 was evaluated using 2-D pore network model simulations; again the increment in sweep efficiency was the greatest in liquid CO2 phase due to the largest reduction in capillary factor. This result provides novel insights as to the role of naturally occurring biosurfactants in CO2 storage and
International Nuclear Information System (INIS)
Felix, T.; Cassini, F.A.; Benetoli, L.O.B.; Dotto, M.E.R.; Debacher, N.A.
2017-01-01
Highlights: • Polymeric surfaces were etched using non-thermal plasma at different intensities. • Polymers of low mechanical hardness reached the saturation level faster. • A mathematical model based on scaling laws was proposed. - Abstract: The experiments presented in this communication have the purpose to elaborate an explanation for the morphological evolution of the growth of polymeric surfaces provided by the treatment of non-thermal plasma. According to the roughness analysis and the model proposed by scaling laws it is possible relate to a predictable or merely random effect. Polyethylene terephthalate (PET) and poly(etherether)ketone (PEEK) samples were exposed to a non-thermal plasma discharge and the resulting surfaces roughness were analyzed based on the measurements from contact angle, scanning electron microscopy and atomic force microscopy coupled with scaling laws analysis which can help to describe and understand the dynamic of formation of a wide variety of rough surfaces. The roughness, R_R_M_S (RMS- Root Mean Square) values for polymer surface range between 19.8 nm and 110.9 nm. The contact angle and the AFM (Atomic Force Microscopy) measurements as a function of the plasma exposure time were in agreement with both polar and dispersive components according to the surface roughness and also with the morphology evaluated described by Wolf-Villain model, with proximate values of α between 0.91_(_P_E_T_) and 0.88_(_P_E_E_K_), β = 0.25_(_P_E_T_) and z = 3,64_(_P_E_T_).
Wang, Shuai; Li, Yapeng; Fei, Xiaoliang; Sun, Mingda; Zhang, Chaoqun; Li, Yaoxian; Yang, Qingbiao; Hong, Xia
2011-07-15
A durable superhydrophobic surface with low water sliding angle (SA) and high water contact angle (CA) was obtained by electrospinning poly (vinylidene fluoride) (PVDF) which was mixed with epoxy-siloxane modified SiO(2) nanoparticles. To increase the roughness, modified SiO(2) nanoparticles were introduced into PVDF precursor solution. Then in the electrospinning process, nano-sized SiO(2) particles irregularly inlayed (it could also be regard as self-assembly) in the surface of the micro-sized PVDF mini-islands so as to form a dual-scale structure. This structure was responsible for the superhydrophobicity and self-cleaning property. In addition, epoxy-siloxane copolymer was used to modify the surface of SiO(2) nanoparticles so that the SiO(2) nanoparticles could stick to the surface of the micro-sized PVDF mini-islands. Through the underwater immersion test, the SiO(2) nanoparticles cannot be separated from PVDF easily so as to achieve the effect of durability. We chiefly explore the surface wettability and the relationship between the mass ratio of modified SiO(2) nanoparticles/PVDF and the CA, SA of electrospun mat. As the content of modified SiO(2) nanoparticles increased, the value of CA increased, ranging from 145.6° to 161.2°, and the water SA decreased to 2.17°, apparently indicating that the membrane we fabricated has a perfect effect of superhydrophobicity. Copyright © 2011 Elsevier Inc. All rights reserved.
Nonzero θ13 and neutrino masses from the modified tri-bi-maximal neutrino mixing matrix
International Nuclear Information System (INIS)
Damanik, A.
2014-01-01
There are 3 types of neutrino mixing matrices: tri-bi-maximal, bi-maximal and democratic. These 3 types of neutrino mixing matrices predict that the mixing angle θ 13 should be null. Motivated by the recent experimental evidence of nonzero and relatively large θ 13 , we modified the tribimaximal mixing matrix by introducing a simple perturbation matrix into tribimaximal neutrino mixing matrix. In this scenario, we obtained nonzero mixing angle θ 13 =7.9 degrees which is in agreement with the present experimental results. By imposing 2 zeros texture into the obtained neutrino mass matrix from modified tribimaximal mixing matrix, we then have the neutrino mass spectrum in normal hierarchy. Some phenomenological implications are also discussed. It appears that if we use the solar neutrino squared-mass difference to determine the values of neutrino masses, then we cannot have the correct value for the atmospheric squared-mass difference. Conversely, if we use the experimental value of the squared-mass difference to determine the neutrino masses, then we cannot have the correct value for the solar neutrino squared-mass difference
On Reggeon field theories and nonzero vacuum expectation values
International Nuclear Information System (INIS)
Venturi, G.
1976-01-01
In this note it is obtained a satisfactory ''nonrelativistic'' reggeon theory by starting from a ''relativistic'' one, examining its ''nonrelativistic'' limit and allowing a nonzero vacuum expectation value for the pomeron field. In such a context the introduction of secondary trajectories is also studied
Energy Technology Data Exchange (ETDEWEB)
Hofmeister, Caroline, E-mail: caroline.hofmeister@de.bosch.com [Robert Bosch GmbH, Postfach 30 02 40, 70442 Stuttgart (Germany); Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM, Wiener Str. 12, 28359 Bremen (Germany); Maaß, Sebastian [Robert Bosch GmbH, Postfach 30 02 40, 70442 Stuttgart (Germany); Fladung, Thorsten; Mayer, Bernd [Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM, Wiener Str. 12, 28359 Bremen (Germany)
2017-01-01
Epoxy acrylate based solder mask formulations were conditioned by different printed circuit board (PCB) manufacturing and PCB assembly process stages. Depending on these different influences the chemistry of the solder mask surface was investigated regarding adhesion to possible adhesion partners. The combination of X-ray photoelectron spectrometry (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and the contact angle method, for surface energy determination, provided a detailed understanding of the surface near region up to the topmost monolayer, which forms the contact zone in which adhesion takes place. The combination of ToF-SIMS and XPS provided molecular information of surface components comprising quantitative information. The influences of all process steps, like UV, chemical and thermal treatment, on the chemical surface composition and appearance were identified. Based on the results a chemical surface model could be created regarding the different adhesion mechanisms. It has been shown that an enrichment of siloxanes at the surface is generated by different mechanisms that were distinguished based on ToF-SIMS. Even though an oxidation process in the surface near region (10 nm) was indicated by XPS, no increase of the surface polar groups and thus no polarity increase could be observed within the first monolayer. A surface model derived from the analysis results shows generation and occupation of free sites at the surface through all stages of the process. An occupation of free sites by siloxanes from additives in the solder mask formulation results in a siloxane dominated topmost monolayer. - Highlights: • A surface model describing the process influences is proposed. • Detailed siloxane reaction analysis was possible with ToF-SIMS. • Photo-chemical, chemical and thermal surface modification occur during PCB manufacturing.
International Nuclear Information System (INIS)
Schusser, S.; Menzel, S.; Bäcker, M.; Leinhos, M.; Poghossian, A.; Wagner, P.; Schöning, M.J.
2013-01-01
For the development of new biopolymers and implantable biomedical devices with predicted biodegradability, simple, non-destructive, fast and inexpensive techniques capable for real-time in situ testing of the degradation kinetics of polymers are highly appreciated. In this work, a capacitive field-effect electrolyte–insulator–semiconductor (EIS) sensor has been applied for real-time in situ monitoring of degradation of thin poly(D,L-lactic acid) (PDLLA) films over a long-time period of one month. Generally, the polymer-modified EIS (PMEIS) sensor is capable of detecting any changes in the bulk, surface and interface properties of the polymer (e.g., thickness, coverage, dielectric constant, surface potential) induced by degradation processes. The time-dependent capacitance–voltage (C–V) characteristics of PMEIS structures were used as an indicator of the polymer degradation. To accelerate the PDLLA degradation, experiments were performed in alkaline buffer solution of pH 10.6. The results of these degradation measurements with the EIS sensor were verified by the detection of lactic acid (product of the PDLLA degradation) in the degradation medium. In addition, the micro-structural and morphological changes of the polymer surface induced by the polymer degradation have been systematically studied by means of scanning-electron microscopy, atomic-force microscopy, optical microscopy, and contact-angle measurements
Energy Technology Data Exchange (ETDEWEB)
Melilli, G.; Madon, B.; Wegrowe, J.-E., E-mail: jean-eric.wegrowe@polytechnique.edu; Clochard, M.-C., E-mail: clochard@cea.fr
2015-12-15
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 (α{sub irrad}) leading to, after electrodeposition, embedded Ni NWs of different orientations.
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.
International Nuclear Information System (INIS)
Melilli, G.; Madon, B.; Wegrowe, J.-E.; Clochard, M.-C.
2015-01-01
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 (α irrad ) leading to, after electrodeposition, embedded Ni NWs of different orientations.
Phase diagram of the Dirac spectrum at nonzero chemical potential
International Nuclear Information System (INIS)
Osborn, J. C.; Splittorff, K.; Verbaarschot, J. J. M.
2008-01-01
The Dirac spectrum of QCD with dynamical fermions at nonzero chemical potential is characterized by three regions: a region with a constant eigenvalue density, a region where the eigenvalue density shows oscillations that grow exponentially with the volume and the remainder of the complex plane where the eigenvalue density is zero. In this paper we derive the phase diagram of the Dirac spectrum from a chiral Lagrangian. We show that the constant eigenvalue density corresponds to a pion condensed phase while the strongly oscillating region is given by a kaon condensed phase. The normal phase with nonzero chiral condensate but vanishing Bose condensates coincides with the region of the complex plane where there are no eigenvalues.
Fluctuation induced critical behavior at nonzero temperature and chemical potential
International Nuclear Information System (INIS)
Splittorff, K.; Lenaghan, J.T.; Wirstam, J.
2003-01-01
We discuss phase transitions in relativistic systems as a function of both the chemical potential and temperature. The presence of a chemical potential explicitly breaks Lorentz invariance and may additionally break other internal symmetries. This introduces new subtleties in the determination of the critical properties. We discuss separately three characteristic effects of a nonzero chemical potential. First, we consider only the explicit breaking of Lorentz invariance using a scalar field theory with a global U(1) symmetry. Second, we study the explicit breaking of an internal symmetry in addition to Lorentz invariance using two-color QCD at nonzero baryonic chemical potential. Finally, we consider the spontaneous breaking of a symmetry using three-color QCD at nonzero baryonic and isospin chemical potential. For each case, we derive the appropriate three-dimensional effective theory at criticality and study the effect of the chemical potential on the fixed point structure of the β functions. We find that the order of the phase transition is not affected by the explicit breaking of Lorentz invariance but is sensitive to the breaking of additional symmetries by the chemical potential
Nonthreshold D-brane bound states and black holes with nonzero entropy
International Nuclear Information System (INIS)
Costa, M.S.; Cvetic, M.
1997-01-01
We start with Bogomol close-quote nyi-Prasad-Sommerfield- (BPS) saturated configurations of two (orthogonally) intersecting M-branes and use the electromagnetic duality or dimensional reduction along a boost, in order to obtain new p-brane bound states. In the first case the resulting configurations are interpreted as BPS-saturated nonthreshold bound states of intersecting p-branes, and in the second case as p-branes intersecting at angles and their duals. As a by-product we deduce the enhancement of supersymmetry as the angle approaches zero. We also comment on the D-brane theory describing these new bound states, and a connection between the angle and the world-volume gauge fields of the D-brane system. We use these configurations to find new embeddings of the four- and five-dimensional black holes with nonzero entropy, whose entropy now also depends on the angle and world-volume gauge fields. The corresponding D-brane configuration sheds light on the microscopic entropy of such black holes. copyright 1997 The American Physical Society
Bayesian evidence for non-zero θ 13 and CP-violation in neutrino oscillations
Bergström, Johannes
2012-08-01
We present the Bayesian method for evaluating the evidence for a non-zero value of the leptonic mixing angle θ 13 and CP-violation in neutrino oscillation experiments. This is an application of the well-established method of Bayesian model selection, of which we give a concise and pedagogical overview. When comparing the hypothesis θ 13 = 0 with hypotheses where θ 13 > 0 using global data but excluding the recent reactor measurements, we obtain only a weak preference for a non-zero θ 13, even though the significance is over 3 σ. We then add the reactor measurements one by one and show how the evidence for θ 13 > 0 quickly increases. When including the D ouble C hooz, D aya B ay, and RENO data, the evidence becomes overwhelming with a posterior probability of the hypothesis θ 13 = 0 below 10-11. Owing to the small amount of information on the CP-phase δ, very similar evidences are obtained for the CP-conserving and CP-violating hypotheses. Hence, there is, not unexpectedly, neither evidence for nor against leptonic CP-violation. However, when future experiments aiming to search for CP-violation have started taking data, this question will be of great importance and the method described here can be used as an important complement to standard analyses.
Helicity-dependent generalized parton distributions for nonzero skewness
Energy Technology Data Exchange (ETDEWEB)
Mondal, Chandan [Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou (China)
2017-09-15
We investigate the helicity-dependent generalized parton distributions (GPDs) in momentum as well as transverse position (impact) spaces for the u and d quarks in a proton when the momentum transfer in both the transverse and the longitudinal directions are nonzero. The GPDs are evaluated using the light-front wave functions of a quark-diquark model for nucleon where the wave functions are constructed by the soft-wall AdS/QCD correspondence. We also express the GPDs in the boost-invariant longitudinal position space. (orig.)
Design objectives with non-zero prescribed support displacements
DEFF Research Database (Denmark)
Pedersen, Pauli; Pedersen, Niels Leergaard
2011-01-01
When non-zero prescribed support displacements are involved in addition to design independent loads for a continuum/structure, then the objectives of minimum compliance (total elastic energy) and of maximum strength lead to different designs. This is verified by the presented sensitivities. Designs...... minimization as well as that of direct strength maximization; we choose the objective of obtaining uniform energy density and show by examples that the obtained solutions are close to fulfilling also strength maximization, with the price of increased compliance. Optimal design examples are presented...
Implications of nonzero θ13 for the neutrino mass hierarchy
International Nuclear Information System (INIS)
Ernst, D J; Cogswell, B K; Burroughs, H R; Escamilla-Roa, J; Latimer, D C
2012-01-01
The Daya Bay, RENO, and Double Chooz experiments have discovered a large non-zero value for θ 13 . We present a global analysis that includes these three experiments, Chooz, the Super-K atmospheric data, and the ν μ → ν e T2K and MINOS experiments that are sensitive to the hierarchy and the sign of θ 13 . We report preliminary results in which we fix the mixing parameters other than θ 13 to those from a recent global analysis. Given there is no evidence for a non-zero CP violation, we assume δ = 0. T2K and MINOS lie in a region of L/E where there is a hierarchy degeneracy in the limit of θ 13 → 0 and no matter interaction. For nonzero θ 13 , the symmetry is partially broken, but a degeneracy under the simultaneous exchange of both hierarchy and the sign of θ 13 remains. Matter effects break this symmetry such that the positions of the peaks in the oscillation probabilities maintain the two-fold symmetry, while the magnitude of the oscillations is sensitive to the hierarchy. This renders T2K and NOvA, with different baselines and different matter effects, better able in combination to distinguish the hierarchy and the sign of θ 13 . The present T2K and MINOS data do not distinguish between hierarchies or the sign of θ 13 , but the large value of θ 13 yields effects from atmospheric data that do. We find for normal hierarchy, positive θ 13 , sin 2 2θ 13 = 0.090 ± 0.020 and is 0.2% probable it is the correct combination; for normal hierarchy, negative θ 13 , sin 2 2θ 13 = 0.108 ± 0.023 and is 2.2% probable; for inverse hierarchy, positive θ 13 , sin 2 2θ 13 = 0.110±0.022 and is 7.1% probable; for inverse hierarchy, negative θ 13 , sin 2 2θ 13 = 0.113 ± 0.022 and is 90.5% probable, results that are inconsistent with two similar analyses.
Corrigan-Ramond Extension of QCD at Nonzero Baryon Density
DEFF Research Database (Denmark)
T. Frandsen, M.; Kouvaris, Christoforos; Sannino, F.
2006-01-01
We investigate the Corrigan-Ramond extension of one massless flavor Quantum Chromo Dynamics at nonzero quark chemical potential. Since the extension requires the fermions to transform in the two index antisymmetric representation of the gauge group, one finds that the number of possible channels ......-Grigoriev-Rubakov chiral waves. We discover, differently from the 't Hooft limit, the possibility of a colored chiral wave breaking the color symmetry as well as translation invariance....... is richer than in the 't Hooft limit. We first discuss the diquark channels and show that for a number of colors larger than three a new diquark channel appears. We then study the infinite number of color limit and show that the Fermi surface is unstable to the formation of the Deryagin...
Hopping magnetotransport via nonzero orbital momentum states and organic magnetoresistance.
Alexandrov, Alexandre S; Dediu, Valentin A; Kabanov, Victor V
2012-05-04
In hopping magnetoresistance of doped insulators, an applied magnetic field shrinks the electron (hole) s-wave function of a donor or an acceptor and this reduces the overlap between hopping sites resulting in the positive magnetoresistance quadratic in a weak magnetic field, B. We extend the theory of hopping magnetoresistance to states with nonzero orbital momenta. Different from s states, a weak magnetic field expands the electron (hole) wave functions with positive magnetic quantum numbers, m>0, and shrinks the states with negative m in a wide region outside the point defect. This together with a magnetic-field dependence of injection/ionization rates results in a negative weak-field magnetoresistance, which is linear in B when the orbital degeneracy is lifted. The theory provides a possible explanation of a large low-field magnetoresistance in disordered π-conjugated organic materials.
Performance of heat engines with non-zero heat capacity
International Nuclear Information System (INIS)
Odes, Ron; Kribus, Abraham
2013-01-01
Highlights: ► Finite heat capacity is a second irreversibility mechanism in addition to thermal resistance. ► Heat capacity introduces thermal transients and reverse heat flow. ► Engine maximum power and efficiency are lower for finite heat capacity. ► Implementing the optimal engine cycle requires active control. - Abstract: The performance of a heat engine is analyzed subject to two types of irreversibility: a non-zero heat capacity, together with the more common finite heat transfer rate between the engine and the external heat reservoirs. The heat capacity represents an engine body that undergoes significant temperature variations during the engine cycle. An option to cut off the heat exchange between the engine and the external surrounding for part of the engine cycle is also explored. A variational approach was taken to find the engine’s internal temperature profile (which defines the internal thermodynamic cycle) that would produce maximum power. The maximum power is shown to be lower than the case of zero heat capacity, due to a loss of heat that is stored in the engine body and then lost, bypassing the thermodynamic cycle. The maximum efficiency and the efficiency at maximum power are also lower than the zero heat capacity case. Similar to the Curzon–Ahlborn analysis, power can be traded for increased efficiency, but for high heat capacity, the range of efficiency that is available for such a trade is diminished. Isolating the engine during part of the cycle reduces maximum power, but the efficiency at maximum power and the maximum efficiency are improved, due to better exploitation of heat stored in the engine body. This might be useful for real engines that are limited by the internal energy change during a single engine cycle or by the operating frequency, leading to a broader power–efficiency curve.
Should tsunami simulations include a nonzero initial horizontal velocity?
Lotto, Gabriel C.; Nava, Gabriel; Dunham, Eric M.
2017-08-01
Tsunami propagation in the open ocean is most commonly modeled by solving the shallow water wave equations. These equations require initial conditions on sea surface height and depth-averaged horizontal particle velocity or, equivalently, horizontal momentum. While most modelers assume that initial velocity is zero, Y.T. Song and collaborators have argued for nonzero initial velocity, claiming that horizontal displacement of a sloping seafloor imparts significant horizontal momentum to the ocean. They show examples in which this effect increases the resulting tsunami height by a factor of two or more relative to models in which initial velocity is zero. We test this claim with a "full-physics" integrated dynamic rupture and tsunami model that couples the elastic response of the Earth to the linearized acoustic-gravitational response of a compressible ocean with gravity; the model self-consistently accounts for seismic waves in the solid Earth, acoustic waves in the ocean, and tsunamis (with dispersion at short wavelengths). Full-physics simulations of subduction zone megathrust ruptures and tsunamis in geometries with a sloping seafloor confirm that substantial horizontal momentum is imparted to the ocean. However, almost all of that initial momentum is carried away by ocean acoustic waves, with negligible momentum imparted to the tsunami. We also compare tsunami propagation in each simulation to that predicted by an equivalent shallow water wave simulation with varying assumptions regarding initial velocity. We find that the initial horizontal velocity conditions proposed by Song and collaborators consistently overestimate the tsunami amplitude and predict an inconsistent wave profile. Finally, we determine tsunami initial conditions that are rigorously consistent with our full-physics simulations by isolating the tsunami waves from ocean acoustic and seismic waves at some final time, and backpropagating the tsunami waves to their initial state by solving the
International Nuclear Information System (INIS)
Thompson, J R; Christen, D K; Zhang Yifei; Zuev, Y L; Cantoni, C; Sinclair, J W; Chen Yimin; Selvamanickam, V
2010-01-01
Applications of coated conductors based on high- T c superconductors often require detailed knowledge of their critical current density J c as a function of magnetic field orientation as well as field strength and temperature. This work demonstrates experimental methods for obtaining the angularly dependent J c using contact-free magnetic measurements, and qualifies those methods using several well defined conditions. The studies complement traditional transport techniques and are readily extended to conditions of field and temperature where the current density is very large and transport methods become difficult. Results on representative materials are presented.
Energy Technology Data Exchange (ETDEWEB)
Thompson, James R [ORNL; Sinclair IV, John W [ORNL; Christen, David K [ORNL; Zhang, Yifei [ORNL; Zuev, Yuri L [ORNL; Cantoni, Claudia [ORNL; Chen, Y [SuperPower Incorporated, Schenectady, New York; Selvamanickam, V. [SuperPower Incorporated, Schenectady, New York
2010-01-01
Applications of coated conductors based on high-Tc superconductors often require detailed knowledge of their critical current density Jc as a function of magnetic field orientation as well as field strength and temperature. This work demonstrates experimental methods to obtain the angularly dependent Jc using contact-free magnetic measurements, and qualifies those methods using several well defined conditions. The studies complement traditional transport techniques and are readily extended to conditions of field and temperature where the current density is very large and transport methods become difficult. Results on representative materials are presented.
Energy Technology Data Exchange (ETDEWEB)
Thompson, J R; Christen, D K; Zhang Yifei; Zuev, Y L; Cantoni, C [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6092 (United States); Sinclair, J W [Department of Physics, University of Tennessee, Knoxville, TN 37996-1200 (United States); Chen Yimin; Selvamanickam, V [SuperPower, Incorporated, 450 Duane Avenue, Schenectady, NY 12304 (United States)
2010-01-15
Applications of coated conductors based on high- T{sub c} superconductors often require detailed knowledge of their critical current density J{sub c} as a function of magnetic field orientation as well as field strength and temperature. This work demonstrates experimental methods for obtaining the angularly dependent J{sub c} using contact-free magnetic measurements, and qualifies those methods using several well defined conditions. The studies complement traditional transport techniques and are readily extended to conditions of field and temperature where the current density is very large and transport methods become difficult. Results on representative materials are presented.
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.
Ergodic Capacity Analysis of Free-Space Optical Links with Nonzero Boresight Pointing Errors
Ansari, Imran Shafique; Alouini, Mohamed-Slim; Cheng, Julian
2015-01-01
A unified capacity analysis of a free-space optical (FSO) link that accounts for nonzero boresight pointing errors and both types of detection techniques (i.e. intensity modulation/ direct detection as well as heterodyne detection) is addressed
Lr-Lp Stability of the Incompressible Flows with Nonzero Far-Field Velocity
Directory of Open Access Journals (Sweden)
Jaiok Roh
2011-01-01
Full Text Available We consider the stability of stationary solutions w for the exterior Navier-Stokes flows with a nonzero constant velocity u∞ at infinity. For u∞=0 with nonzero stationary solution w, Chen (1993, Kozono and Ogawa (1994, and Borchers and Miyakawa (1995 have studied the temporal stability in Lp spaces for 11 and obtain Lr-Lp stability as Kozono and Ogawa and Borchers and Miyakawa obtained for u∞=0.
Chiral properties of two-flavour QCD at zero and non-zero temperature
Energy Technology Data Exchange (ETDEWEB)
Brandt, Bastian Benjamin
2012-11-22
radius are used to test chiral perturbation theory (χPT) and are thereby extrapolated to the physical point and the continuum. The final result in units of the hadronic radius r{sub 0} is left angle r{sup 2}{sub π} right angle {sup phys}/r{sub 0}{sup 2}=1.87({sup +12}{sub -10})({sup +4}{sub -15}) or left angle r{sub π}{sup 2} right angle {sup phys}=0.473({sup +30}{sub -26})({sup +10}{sub -38})(10) fm, which agrees well with the results from other measurements in LQCD and experiment. Note, that this is the first continuum extrapolated result for the charge radius from LQCD which has been extracted from measurements of the form factor in the region of small q{sup 2}. The order of the phase transition in the chiral limit of two-flavour QCD and the associated transition temperature are the last unknown features of the phase diagram at zero chemical potential. The two possible scenarios are a second order transition in the O(4)-universality class or a first order transition. Since direct simulations in the chiral limit are not possible the transition can only be investigated by simulating at non-zero quark mass with a subsequent chiral extrapolation, guided by the universal scaling in the vicinity of the critical point. The thesis presents the setup and first results from a study on this topic. The study provides the ideal platform to test the potential and limits of todays simulation algorithms at finite temperature. The results from a first scan at a constant zero-temperature pion mass of about 290 MeV are promising, and it appears that simulations down to physical quark masses are feasible. Of particular relevance for the order of the chiral transition is the strength of the anomalous breaking of the U{sub A}(1) symmetry at the transition point. It can be studied by looking at the degeneracies of the correlation functions in scalar and pseudoscalar channels. For the temperature scan reported in this thesis the breaking is still pronounced in the transition region and
Chiral properties of two-flavour QCD at zero and non-zero temperature
International Nuclear Information System (INIS)
Brandt, Bastian Benjamin
2012-01-01
test chiral perturbation theory (χPT) and are thereby extrapolated to the physical point and the continuum. The final result in units of the hadronic radius r 0 is left angle r 2 π right angle phys /r 0 2 =1.87( +12 -10 )( +4 -15 ) or left angle r π 2 right angle phys =0.473( +30 -26 )( +10 -38 )(10) fm, which agrees well with the results from other measurements in LQCD and experiment. Note, that this is the first continuum extrapolated result for the charge radius from LQCD which has been extracted from measurements of the form factor in the region of small q 2 . The order of the phase transition in the chiral limit of two-flavour QCD and the associated transition temperature are the last unknown features of the phase diagram at zero chemical potential. The two possible scenarios are a second order transition in the O(4)-universality class or a first order transition. Since direct simulations in the chiral limit are not possible the transition can only be investigated by simulating at non-zero quark mass with a subsequent chiral extrapolation, guided by the universal scaling in the vicinity of the critical point. The thesis presents the setup and first results from a study on this topic. The study provides the ideal platform to test the potential and limits of todays simulation algorithms at finite temperature. The results from a first scan at a constant zero-temperature pion mass of about 290 MeV are promising, and it appears that simulations down to physical quark masses are feasible. Of particular relevance for the order of the chiral transition is the strength of the anomalous breaking of the U A (1) symmetry at the transition point. It can be studied by looking at the degeneracies of the correlation functions in scalar and pseudoscalar channels. For the temperature scan reported in this thesis the breaking is still pronounced in the transition region and the symmetry becomes effectively restored only above 1.16 T C . The thesis also provides an extensive
Vilardy, Juan M.; Millán, María S.; Pérez-Cabré, Elisabet
2017-02-01
A novel nonlinear image encryption scheme based on a fully phase nonzero-order joint transform correlator architecture (JTC) in the Gyrator domain (GD) is proposed. In this encryption scheme, the two non-overlapping data distributions of the input plane of the JTC are fully encoded in phase and this input plane is transformed using the Gyrator transform (GT); the intensity distribution captured in the GD represents a new definition of the joint Gyrator power distribution (JGPD). The JGPD is modified by two nonlinear operations with the purpose of retrieving the encrypted image, with enhancement of the decrypted signal quality and improvement of the overall security. There are three keys used in the encryption scheme, two random phase masks and the rotation angle of the GT, which are all necessary for a proper decryption. Decryption is highly sensitivity to changes of the rotation angle of the GT as well as to little changes in other parameters or keys. The proposed encryption scheme in the GD still preserves the shift-invariance properties originated in the JTC-based encryption in the Fourier domain. The proposed encryption scheme is more resistant to brute force attacks, chosen-plaintext attacks, known-plaintext attacks, and ciphertext-only attacks, as they have been introduced in the cryptanalysis of the JTC-based encryption system. Numerical results are presented and discussed in order to verify and analyze the feasibility and validity of the novel encryption-decryption scheme.
The quenched limit of lattice QCD at non-zero baryon number
International Nuclear Information System (INIS)
Engels, J.; Kaczmarek, O.; Karsch, F.; Laermann, E.
1999-01-01
We discuss the thermodynamics of gluons in the background of static quark sources. In order to do so we formulate the quenched limit of QCD at non-zero baryon number. A first numerical analysis of this system shows that it undergoes a smooth deconfining transition. We find evidence for a region of coexisting phases that becomes broader with increasing baryon number density. Although the action is in our formulation explicitly Z(3) symmetric the Polyakov loop expectation value becomes non-zero already in the low temperature phase. It indicates that the heavy quark potential stays finite at large distances, i.e. the string between static quarks breaks at non-zero baryon number density already in the hadronic phase
S-parameter at Non-Zero Temperature and Chemical Potential
DEFF Research Database (Denmark)
Søndergaard, Ulrik Ishøj; Sannino, Francesco; Pica, Claudio
2011-01-01
We compute the finite-temperature and matter density corrections to the S-parameter at the one loop level. At non-zero temperature T and matter density Lorentz symmetry breaks and therefore we suggest a suitable generalization of the S-parameter. By computing the plasma correction, we discover...... a reduction of the S-parameter in the physically relevant region of small external momenta for any non-zero chemical potential and T. In particular, the S-parameter vanishes at small m/T, where m is the mass of the fermions, due to the finite extent of the temporal direction. Our results are directly...
On the proposed second law paradox in a nonzero floating potential
International Nuclear Information System (INIS)
Cruden, Brett A.
2001-01-01
A second law paradox was previously proposed for a plasma contained within an infinite blackbody. The proposed second law paradox was dependent on the plasma having a nonzero floating potential [D. P. Sheehan and J. D. Means, Phys. Plasmas 5, 2469 (1998)]. This work demonstrates that a nonzero floating potential is indicative of some energy contained within the plasma that can be withdrawn from the plasma without violation of the second law. Furthermore, it is shown from the probe theory that the plasma in this hypothetical configuration must have a floating potential of zero at steady state
International Nuclear Information System (INIS)
Bruk, Yulii M; Voloshchuk, Aleksandr N
2012-01-01
The functional Pais equation for scattering phases with nonzero orbital momenta is solved in the case of low-energy particles. For short-range screened potentials, in particular, Yukawa or Thomas-Fermi potentials, the Pais equation is shown to reduce to transcendental equations. For the potentials varying ∼r - n , n > 0, simple algebraic equations are obtained for determining the phases δ l , l≠0. Possible applications of the Pais approximation to the problem of finding resonance regimes in the scattering of low-energy particles with nonzero orbital momenta are discussed. (methodological notes)
International Nuclear Information System (INIS)
Marklund, T.
1978-01-01
The most commonly used methods of assessing the scoliotic deviation measure angles that are not clearly defined in relation to the anatomy of the patient. In order to give an anatomic basis for such measurements it is proposed to define the scoliotic deviation as the deviation the vertebral column makes with the sagittal plane. Both the Cobb and the Ferguson angles may be based on this definition. The present methods of measurement are then attempts to measure these angles. If the plane of these angles is parallel to the film, the measurement will be correct. Errors in the measurements may be incurred by the projection. A hypothetical projection, called a 'rectified orthogonal projection', is presented, which correctly represents all scoliotic angles in accordance with these principles. It can be constructed in practice with the aid of a computer and by performing measurements on two projections of the vertebral column; a scoliotic curve can be represented independent of the kyphosis and lordosis. (Auth.)
Energy Technology Data Exchange (ETDEWEB)
Davila Pulido, G. I.; Uribe Salas, A.
2011-07-01
This article presents results of an experimental study on the sphalerite activation with Cu(II) and Pb(II), whose main objective was to investigate the activation mechanisms and to evaluate the magnitude of the hydrophobization achieved with both chemical species. The hydrophobicity acquired by the mineral due to the interaction with the activator and collector (sodium isopropyl xanthate) is characterized making use of the contact angle technique. The results show that Cu(II) replaces the Zn of the external layers of the mineral, promoting the sulfide (S{sup 2}-) oxidation to produce a mixture of CuS, Cu{sub 2}S and S{sup o}, of hydrophobic nature. The subsequent interaction with xanthate increases the hydrophobicity of the mineral surface. In turn, Pb(II) activation of sphalerite is due to the formation of a PbS layer that reacts with xanthate to produce hydrophobic species (e.g., PbX{sub 2}). It is also observed that the hydrophobicity of sphalerite activated with Pb(II) is favored under air atmospheres, as compared to that obtained under nitrogen atmospheres. It is concluded that the hydrophobicity achieved by lead activation may be of the same order of magnitude to that deliverately induced by copper activation. (Author) 11 refs.
Beam-beam collisions and crossing angles in RHIC
International Nuclear Information System (INIS)
Peggs, S.
1999-01-01
This paper evaluates the strength of head on and parasitic beam-beam collisions in RHIC when the crossing angle is zero. A non-zero crossing angle is not required in normal operation with 120 bunches, thanks to the early separation of the two beams. The RHIC lattice is shown to easily accommodate even conservatively large crossing angles, for example in beam dynamics studies, or in future operational upgrades to as many as 360 bunches per ring. A modest loss in luminosity is incurred when gold ions collide at an angle after 10 hours of storage
Gravitational radiation in relativistic theory of gravity with a nonzero graviton mass
International Nuclear Information System (INIS)
Vlasov, A.A.; Chugreev, Yu.V.
1987-01-01
Radiation of gravitation waves have been analysed in the linear approximation of the relative theory of gravity, with the mass of graviton being nonzero. It is shown that the main contribution to the energy loss due to gravitational radiation has been described by the well-known quadrupole formula. Linear approximation applicability conditions have been analysed
First non-zero terms for the Taylor expansion at 1 of the Conway potential function
Buryak, A.Y.
2011-01-01
The Conway potential function ∇ L (t 1,...,t l ) of an ordered oriented link L = L 1 ∪ L 2 ∪ ... ∪ L l ⊂ S 3 is considered. In general, this function is not determined by the linking numbers and the Conway potential functions of the components. However, the first two nonzero terms of the Taylor
Generalized quantization scheme for two-person non-zero sum games
International Nuclear Information System (INIS)
Nawaz, Ahmad; Toor, A H
2004-01-01
We proposed a generalized quantization scheme for non-zero sum games which can be reduced to the two existing quantization schemes under an appropriate set of parameters. Some other important situations are identified which are not apparent in the two existing quantization schemes
Heffernan, Rhys; Yang, Yuedong; Paliwal, Kuldip; Zhou, Yaoqi
2017-09-15
The accuracy of predicting protein local and global structural properties such as secondary structure and solvent accessible surface area has been stagnant for many years because of the challenge of accounting for non-local interactions between amino acid residues that are close in three-dimensional structural space but far from each other in their sequence positions. All existing machine-learning techniques relied on a sliding window of 10-20 amino acid residues to capture some 'short to intermediate' non-local interactions. Here, we employed Long Short-Term Memory (LSTM) Bidirectional Recurrent Neural Networks (BRNNs) which are capable of capturing long range interactions without using a window. We showed that the application of LSTM-BRNN to the prediction of protein structural properties makes the most significant improvement for residues with the most long-range contacts (|i-j| >19) over a previous window-based, deep-learning method SPIDER2. Capturing long-range interactions allows the accuracy of three-state secondary structure prediction to reach 84% and the correlation coefficient between predicted and actual solvent accessible surface areas to reach 0.80, plus a reduction of 5%, 10%, 5% and 10% in the mean absolute error for backbone ϕ , ψ , θ and τ angles, respectively, from SPIDER2. More significantly, 27% of 182724 40-residue models directly constructed from predicted C α atom-based θ and τ have similar structures to their corresponding native structures (6Å RMSD or less), which is 3% better than models built by ϕ and ψ angles. We expect the method to be useful for assisting protein structure and function prediction. The method is available as a SPIDER3 server and standalone package at http://sparks-lab.org . yaoqi.zhou@griffith.edu.au or yuedong.yang@griffith.edu.au. Supplementary data are available at Bioinformatics online. © The Author (2017). Published by Oxford University Press. All rights reserved. For Permissions, please email
Geometry-Dependent Electrostatics near Contact Lines
International Nuclear Information System (INIS)
Chou, Tom
2001-01-01
Long-ranged electrostatic interactions in electrolytes modify contact angles on charged substrates in a scale and geometry-dependent manner. For angles measured at scales smaller than the typical Debye screening length, the wetting geometry near the contact line must be explicitly considered. Using variational and asymptotic methods, we derive new transcendental equations for the contact angle as functions of the electrostatic potential only at the three phase contact line. Analytic expressions are found in certain limits and compared with predictions for contact angles measured with lower resolution. An estimate for electrostatic contributions to line tension is also given
Kreiss, Gunilla; Holmgren, Hanna; Kronbichler, Martin; Ge, Anthony; Brant, Luca
2017-11-01
The conventional no-slip boundary condition leads to a non-integrable stress singularity at a moving contact line. This makes numerical simulations of two-phase flow challenging, especially when capillarity of the contact point is essential for the dynamics of the flow. We will describe a modeling methodology, which is suitable for numerical simulations, and present results from numerical computations. The methodology is based on combining a relation between the apparent contact angle and the contact line velocity, with the similarity solution for Stokes flow at a planar interface. The relation between angle and velocity can be determined by theoretical arguments, or from simulations using a more detailed model. In our approach we have used results from phase field simulations in a small domain, but using a molecular dynamics model should also be possible. In both cases more physics is included and the stress singularity is removed.
Wang, Xuezhi; Huang, Xiaotao; Suvorova, Sofia; Moran, Bill
2018-01-01
Golay complementary waveforms can, in theory, yield radar returns of high range resolution with essentially zero sidelobes. In practice, when deployed conventionally, while high signal-to-noise ratios can be achieved for static target detection, significant range sidelobes are generated by target returns of nonzero Doppler causing unreliable detection. We consider signal processing techniques using Golay complementary waveforms to improve radar detection performance in scenarios involving multiple nonzero Doppler targets. A signal processing procedure based on an existing, so called, Binomial Design algorithm that alters the transmission order of Golay complementary waveforms and weights the returns is proposed in an attempt to achieve an enhanced illumination performance. The procedure applies one of three proposed waveform transmission ordering algorithms, followed by a pointwise nonlinear processor combining the outputs of the Binomial Design algorithm and one of the ordering algorithms. The computational complexity of the Binomial Design algorithm and the three ordering algorithms are compared, and a statistical analysis of the performance of the pointwise nonlinear processing is given. Estimation of the areas in the Delay–Doppler map occupied by significant range sidelobes for given targets are also discussed. Numerical simulations for the comparison of the performances of the Binomial Design algorithm and the three ordering algorithms are presented for both fixed and randomized target locations. The simulation results demonstrate that the proposed signal processing procedure has a better detection performance in terms of lower sidelobes and higher Doppler resolution in the presence of multiple nonzero Doppler targets compared to existing methods. PMID:29324708
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)
Perturbative estimates of lepton mixing angles in unified models
International Nuclear Information System (INIS)
Antusch, Stefan; King, Stephen F.; Malinsky, Michal
2009-01-01
Many unified models predict two large neutrino mixing angles, with the charged lepton mixing angles being small and quark-like, and the neutrino masses being hierarchical. Assuming this, we present simple approximate analytic formulae giving the lepton mixing angles in terms of the underlying high energy neutrino mixing angles together with small perturbations due to both charged lepton corrections and renormalisation group (RG) effects, including also the effects of third family canonical normalization (CN). We apply the perturbative formulae to the ubiquitous case of tri-bimaximal neutrino mixing at the unification scale, in order to predict the theoretical corrections to mixing angle predictions and sum rule relations, and give a general discussion of all limiting cases. We also discuss the implications for the sum rule relations of the measurement of a non-zero reactor angle, as hinted at by recent experimental measurements.
Neutron transport assembly calculation with non-zero net current boundary condition
International Nuclear Information System (INIS)
Jo, Chang Keun
1993-02-01
Fuel assembly calculation for the homogenized group constants is one of the most important parts in the reactor core analysis. The homogenized group constants of one a quarter assembly are usually generated for the nodal calculation of the reactor core. In the current nodal calculation, one or a quarter of the fuel assembly corresponds to a unit node. The homogenized group constant calculation for a fuel assembly proceeds through cell spectrum calculations, group condensation and cell homogenization calculations, two dimensional fuel assembly calculation, and then depletion calculations of fuel rods. To obtain the assembly wise homogenized group constants, the two dimensional transport calculation is usually performed. Most codes for the assembly wise homogenized group constants employ a zero net current boundary condition. CASMO-3 is such a code that is in wide use. The zero net current boundary condition is plausible and valid in an infinite reactor composed of the same kind of assemblies. However, the reactor is finite and the core is constructed by different kinds of assemblies. Hence, the assumption of the zero net current boundary condition is not valid in the actual reactor. The objective of this study is to develop a homogenization methodology that can treat any actual boundary condition, i.e. non-zero net current boundary condition. In order to treat the non-zero net current boundary condition, we modify CASMO-3. For the two-dimensional treatment in CASMO-3, a multigroup integral transport routine based on the method of transmission probability is used. The code performs assembly calculation with zero net current boundary condition. CASMO-3 is modified to consider the inhomogeneous source at the assembly boundary surface due to the non-zero net current. The modified version of CASMO-3 is called CASMO-3M. CASMO-3M is applied to several benchmark problems. In order to obtain the inhomogeneous source, the global calculation is performed. The local calculation
Two observable features of the staggered-flux phase at nonzero doping
International Nuclear Information System (INIS)
Hsu, T.C.; Marston, J.B.; Affleck, I.
1991-01-01
We investigate whether the staggered-flux phase (SFP) is realized in slightly doped phases of the Cu-O high-T c superconductors. Using a mean-field solution of the t-J model, we calculate the size of circulating currents in the CuO 2 planes. For realistic parameters we find nonzero currents when the doping δ 2-x Sr x CuO 4 samples but additional structure along the (Q x ,0) and (0,Q y ) directions has not been seen. The absence of magnetic fields when δ>0.12 is consistent with the limits set by the muon experiments on superconducting samples
Monte Carlo simulations of the NJL model near the nonzero temperature phase transition
International Nuclear Information System (INIS)
Strouthos, Costas; Christofi, Stavros
2005-01-01
We present results from numerical simulations of the Nambu-Jona-Lasinio model with an SU(2)xSU(2) chiral symmetry and N c = 4,8, and 16 quark colors at nonzero temperature. We performed the simulations by utilizing the hybrid Monte Carlo and hybrid Molecular Dynamics algorithms. We show that the model undergoes a second order phase transition. The critical exponents measured are consistent with the classical 3d O(4) universality class and hence in accordance with the dimensional reduction scenario. We also show that the Ginzburg region is suppressed by a factor of 1/N c in accordance with previous analytical predictions. (author)
Calculation of nonzero-temperature Casimir forces in the time domain
International Nuclear Information System (INIS)
Pan, Kai; Reid, M. T. Homer; McCauley, Alexander P.; Rodriguez, Alejandro W.; White, Jacob K.; Johnson, Steven G.
2011-01-01
We show how to compute Casimir forces at nonzero temperatures with time-domain electromagnetic simulations, for example, using a finite-difference time-domain (FDTD) method. Compared to our previous zero-temperature time-domain method, only a small modification is required, but we explain that some care is required to properly capture the zero-frequency contribution. We validate the method against analytical and numerical frequency-domain calculations, and show a surprising high-temperature disappearance of a nonmonotonic behavior previously demonstrated in a pistonlike geometry.
International Nuclear Information System (INIS)
Batishchev, Pavel A.; Tolstikhin, Oleg I.
2007-01-01
The Siegert pseudostate (SPS) formulation of scattering theory, originally developed by Tolstikhin, Ostrovsky, and Nakamura [Phys. Rev. A, 58, 2077 (1998)] for s-wave scattering in a spherically symmetric finite-range potential, is generalized to nonzero angular momenta. The orthogonality and completeness properties of SPSs are established and SPS expansions for the outgoing-wave Green's function, physical states, and scattering matrix are obtained. The present formulation completes the theory of SPSs in the one-channel case, making its application to three-dimensional problems possible. The results are illustrated by calculations for several model potentials
Two-color QCD with non-zero chiral chemical potential
Energy Technology Data Exchange (ETDEWEB)
Braguta, V.V. [Institute for High Energy Physics NRC “Kurchatov Institute' ,142281 Protvino (Russian Federation); Far Eastern Federal University, School of Biomedicine,690950 Vladivostok (Russian Federation); Goy, V.A. [Far Eastern Federal University, School of Natural Sciences,690950 Vladivostok (Russian Federation); Ilgenfritz, E.M. [Joint Institute for Nuclear Research,BLTP, 141980 Dubna (Russian Federation); Kotov, A.Yu. [Institute of Theoretical and Experimental Physics,117259 Moscow (Russian Federation); Molochkov, A.V. [Far Eastern Federal University, School of Biomedicine,690950 Vladivostok (Russian Federation); Müller-Preussker, M.; Petersson, B. [Humboldt-Universität zu Berlin, Institut für Physik,12489 Berlin (Germany)
2015-06-16
The phase diagram of two-color QCD with non-zero chiral chemical potential is studied by means of lattice simulation. We focus on the influence of a chiral chemical potential on the confinement/deconfinement phase transition and the breaking/restoration of chiral symmetry. The simulation is carried out with dynamical staggered fermions without rooting. The dependences of the Polyakov loop, the chiral condensate and the corresponding susceptibilities on the chiral chemical potential and the temperature are presented. The critical temperature is observed to increase with increasing chiral chemical potential.
International Nuclear Information System (INIS)
Blum, T.; Creutz, M.
1999-01-01
The RIKEN BNL Research Center hosted its 19th workshop April 27th through May 1, 1999. The topic was Numerical Algorithms at Non-Zero Chemical Potential. QCD at a non-zero chemical potential (non-zero density) poses a long-standing unsolved challenge for lattice gauge theory. Indeed, it is the primary unresolved issue in the fundamental formulation of lattice gauge theory. The chemical potential renders conventional lattice actions complex, practically excluding the usual Monte Carlo techniques which rely on a positive definite measure for the partition function. This ''sign'' problem appears in a wide range of physical systems, ranging from strongly coupled electronic systems to QCD. The lack of a viable numerical technique at non-zero density is particularly acute since new exotic ''color superconducting'' phases of quark matter have recently been predicted in model calculations. A first principles confirmation of the phase diagram is desirable since experimental verification is not expected soon. At the workshop several proposals for new algorithms were made: cluster algorithms, direct simulation of Grassman variables, and a bosonization of the fermion determinant. All generated considerable discussion and seem worthy of continued investigation. Several interesting results using conventional algorithms were also presented: condensates in four fermion models, SU(2) gauge theory in fundamental and adjoint representations, and lessons learned from strong; coupling, non-zero temperature and heavy quarks applied to non-zero density simulations
Homogenization via the strong-permittivity-fluctuation theory with nonzero depolarization volume
Mackay, Tom G.
2004-08-01
The depolarization dyadic provides the scattering response of a single inclusion particle embedded within a homogenous background medium. These dyadics play a central role in formalisms used to estimate the effective constitutive parameters of homogenized composite mediums (HCMs). Conventionally, the inclusion particle is taken to be vanishingly small; this allows the pointwise singularity of the dyadic Green function associated with the background medium to be employed as the depolarization dyadic. A more accurate approach is pursued in this communication by taking into account the nonzero spatial extent of inclusion particles. Depolarization dyadics corresponding to inclusion particles of nonzero volume are incorporated within the strong-permittivity-fluctuation theory (SPFT). The linear dimensions of inclusion particles are assumed to be small relative to the electromagnetic wavelength(s) and the SPFT correlation length. The influence of the size of inclusion particles upon SPFT estimates of the HCM constitutive parameters is investigated for anisotropic dielectric HCMs.In particular, the interplay between correlation length and inclusion size is explored.
Generalization of the Child-Langmuir law for nonzero injection velocities in a planar diode
International Nuclear Information System (INIS)
Puri, R.R.; Biswas, Debabrata; Kumar, Raghwendra
2004-01-01
The Child-Langmuir law relates the voltage applied across a planar diode to the saturation value J CL of current density that can be transmitted through it in case the injection velocity of electrons is zero. The Child-Langmuir current density J CL is, at the same time: (i) the maximum current density that can be transmitted through a planar diode, (ii) the current density below which the flow is steady and unidirectional in the long time limit, and (iii) the average transmitted current density for any value of injected current density above J CL . Existing generalizations of Child-Langmuir law to nonzero velocities of injection are based on the characteristics (i) and (ii) of J CL . This paper generalizes the law to nonzero velocities of injection based on the characteristic (iii) by deriving an analytical expression for the saturation value of current density. The analytical expression for the saturation current density is found to be well supported by numerical computations. A reason behind preferring the saturation property of the Child-Langmuir current density as the basis for its generalization is the importance of that property in numerical simulations of high current diode devices
Nonzero-Sum Stochastic Differential Portfolio Games under a Markovian Regime Switching Model
Directory of Open Access Journals (Sweden)
Chaoqun Ma
2015-01-01
Full Text Available We consider a nonzero-sum stochastic differential portfolio game problem in a continuous-time Markov regime switching environment when the price dynamics of the risky assets are governed by a Markov-modulated geometric Brownian motion (GBM. The market parameters, including the bank interest rate and the appreciation and volatility rates of the risky assets, switch over time according to a continuous-time Markov chain. We formulate the nonzero-sum stochastic differential portfolio game problem as two utility maximization problems of the sum process between two investors’ terminal wealth. We derive a pair of regime switching Hamilton-Jacobi-Bellman (HJB equations and two systems of coupled HJB equations at different regimes. We obtain explicit optimal portfolio strategies and Feynman-Kac representations of the two value functions. Furthermore, we solve the system of coupled HJB equations explicitly in a special case where there are only two states in the Markov chain. Finally we provide comparative statics and numerical simulation analysis of optimal portfolio strategies and investigate the impact of regime switching on optimal portfolio strategies.
Quantum Quench Dynamics in the Transverse Field Ising Model at Non-zero Temperatures
Abeling, Nils; Kehrein, Stefan
The recently discovered Dynamical Phase Transition denotes non-analytic behavior in the real time evolution of quantum systems in the thermodynamic limit and has been shown to occur in different systems at zero temperature [Heyl et al., Phys. Rev. Lett. 110, 135704 (2013)]. In this talk we present the extension of the analysis to non-zero temperature by studying a generalized form of the Loschmidt echo, the work distribution function, of a quantum quench in the transverse field Ising model. Although the quantitative behavior at non-zero temperatures still displays features derived from the zero temperature non-analyticities, it is shown that in this model dynamical phase transitions do not exist if T > 0 . This is a consequence of the system being initialized in a thermal state. Moreover, we elucidate how the Tasaki-Crooks-Jarzynski relation can be exploited as a symmetry relation for a global quench or to obtain the change of the equilibrium free energy density. This work was supported through CRC SFB 1073 (Project B03) of the Deutsche Forschungsgemeinschaft (DFG).
Nonzero-Sum Relationships in Mitigating Urban Carbon Emissions: A Dynamic Network Simulation.
Chen, Shaoqing; Chen, Bin; Su, Meirong
2015-10-06
The "stove-pipe" way of thinking has been mostly used in mitigating carbon emissions and managing socioeconomics because of its convenience of implementation. However, systems-oriented approaches become imperative in pursuit of an efficient regulation of carbon emissions from systems as complicated as urban systems. The aim of this paper is to establish a dynamic network approach that is capable of assessing the effectiveness of carbon emissions mitigation in a more holistic way. A carbon metabolic network is constructed by modeling the carbon flows between economic sectors and environment. With the network shocked by interventions to the sectoral carbon flows, indirect emissions from the city are accounted for under certain carbon mitigation strategies. The nonzero-sum relationships between sectors and environmental components are identified based on utility analysis, which synthesize the nature of direct and indirect network interactions. The results of the case study of Beijing suggest that the stove-pipe mitigation strategies targeted the economic sectors might be not as efficient as they were expected. A direct cutting in material or energy import to the sectors may result in a rebound in indirect emissions and thus fails to achieve the carbon mitigation goal of the city as a whole. A promising way of foreseeing the dynamic mechanism of emissions is to analyze the nonzero-sum relationships between important urban components. Thinking cities as systems of interactions, the network approach is potentially a strong tool for appraising and filtering mitigation strategies of carbon emissions.
Wetting dynamics at high values of contact line speed
Пономарев, К. О.; Феоктистов, Дмитрий Владимирович; Орлова, Евгения Георгиевна
2015-01-01
Experimental results analyses of dynamic contact angle change under the conditions of substrate wetting by distilled water at high values of the contact line speed was conducted. Three spreading modes for copper substrates with different roughness were selected: drop formation, spreading and equilibrium contact angle formation. Peculiarity of droplet spreading on superhydrophobic surface is found. It consists in a monotonic increase of the advancing dynamic contact angle. The effect of the dr...
Double beta decay and majorana neutrinos. Right-handed currents or nonzero masses
International Nuclear Information System (INIS)
Rosen, S.P.; Perlmutter, A.
1981-01-01
This chapter describes some new developments concerning the mechanism for lepton number nonconservation in no-neutrino double beta decay. Explains that lepton number nonconservation in no-neutrino double beta decay comes about either because both left- and right-handed components of a Majorano neutrino are coupled to the electron in the weak leptonic current, or because the neutrino has nonzero mass. Shows that while nuclear ground-state to ground-state transitions arise from right-handed currents and from neutrino mass terms, transitions to low-lying excited states with J /SUP P/ =2 + can arise only from right-handed currents. Emphasizes that the possibilities of detecting small admixtures of right-handed currents, and of setting limits on neutrino masses that are either very small or very large, make double beta decay a most rewarding phenomenon to study
Ergodic Capacity Analysis of Free-Space Optical Links with Nonzero Boresight Pointing Errors
Ansari, Imran Shafique
2015-04-01
A unified capacity analysis of a free-space optical (FSO) link that accounts for nonzero boresight pointing errors and both types of detection techniques (i.e. intensity modulation/ direct detection as well as heterodyne detection) is addressed in this work. More specifically, an exact closed-form expression for the moments of the end-to-end signal-to-noise ratio (SNR) of a single link FSO transmission system is presented in terms of well-known elementary functions. Capitalizing on these new moments expressions, we present approximate and simple closedform results for the ergodic capacity at high and low SNR regimes. All the presented results are verified via computer-based Monte-Carlo simulations.
Maximum run-up behavior of tsunamis under non-zero initial velocity condition
Directory of Open Access Journals (Sweden)
Baran AYDIN
2018-03-01
Full Text Available The tsunami run-up problem is solved non-linearly under the most general initial conditions, that is, for realistic initial waveforms such as N-waves, as well as standard initial waveforms such as solitary waves, in the presence of initial velocity. An initial-boundary value problem governed by the non-linear shallow-water wave equations is solved analytically utilizing the classical separation of variables technique, which proved to be not only fast but also accurate analytical approach for this type of problems. The results provide important information on maximum tsunami run-up qualitatively. We observed that, although the calculated maximum run-ups increase significantly, going as high as double that of the zero-velocity case, initial waves having non-zero fluid velocity exhibit the same run-up behavior as waves without initial velocity, for all wave types considered in this study.
Chiral condensate at nonzero chemical potential in the microscopic limit of QCD
International Nuclear Information System (INIS)
Osborn, J. C.; Splittorff, K.; Verbaarschot, J. J. M.
2008-01-01
The chiral condensate in QCD at zero temperature does not depend on the quark chemical potential (up to one-third the nucleon mass), whereas the spectral density of the Dirac operator shows a strong dependence on the chemical potential. The cancellations which make this possible also occur on the microscopic scale, where they can be investigated by means of a random matrix model. We show that they can be understood in terms of orthogonality properties of orthogonal polynomials. In the strong non-Hermiticity limit they are related to integrability properties of the spectral density. As a by-product we find exact analytical expressions for the partially quenched chiral condensate in the microscopic domain at nonzero chemical potential.
Parity doubling structure of nucleon at non-zero density in the holographic mean field theory
Directory of Open Access Journals (Sweden)
He Bing-Ran
2014-06-01
Full Text Available We summarize our recent work in which we develope the holographic mean field approach to study the dense baryonic matter in a bottom-up holographic QCD model including baryons and scalar mesons in addition to vector mesons. We first show that, at zero density, the rate of the chiral invariant mass of nucleon is controlled by the ratio of the infrared boundary values of two baryon fields included in the model. Then, at non-zero density, we find that the chiral condensate decreases with the increasing density indicating the partial restoration of the chiral symmetry. Our result shows that the more amount of the proton mass comes from the chiral symmetry breaking, the faster the effective nucleon mass decrease with density.
Floating potential in electronegative plasmas for non-zero ion temperatures
Regodón, Guillermo Fernando; Fernández Palop, José Ignacio; Tejero-del-Caz, Antonio; Díaz-Cabrera, Juan Manuel; Carmona-Cabezas, Rafael; Ballesteros, Jerónimo
2018-02-01
The floating potential of a Langmuir probe immersed in an electronegative plasma is studied theoretically under the assumption of radial positive ion fluid movement for non-zero positive ion temperature: both cylindrical and spherical geometries are studied. The model is solvable exactly. The special characteristics of the electronegative pre-sheath are found and the influence of the stratified electronegative pre-sheath is shown to be very small in practical applications. It is suggested that the use of the floating potential in the measurement of negative ions population density is convenient, in view of the numerical results obtained. The differences between the two radial geometries, which become very important for small probe radii of the order of magnitude of the Debye length, are studied.
Correlation Decay in Fermionic Lattice Systems with Power-Law Interactions at Nonzero Temperature
Hernández-Santana, Senaida; Gogolin, Christian; Cirac, J. Ignacio; Acín, Antonio
2017-09-01
We study correlations in fermionic lattice systems with long-range interactions in thermal equilibrium. We prove a bound on the correlation decay between anticommuting operators and generalize a long-range Lieb-Robinson-type bound. Our results show that in these systems of spatial dimension D with, not necessarily translation invariant, two-site interactions decaying algebraically with the distance with an exponent α ≥2 D , correlations between such operators decay at least algebraically to 0 with an exponent arbitrarily close to α at any nonzero temperature. Our bound is asymptotically tight, which we demonstrate by a high temperature expansion and by numerically analyzing density-density correlations in the one-dimensional quadratic (free, exactly solvable) Kitaev chain with long-range pairing.
Interferometry with particles of non-zero rest mass: topological experiments
International Nuclear Information System (INIS)
Opat, G.I.
1994-01-01
Interferometry as a space-time process is described, together with its topology. Starting from this viewpoint, a convenient unified formalism for the phase shifts which arise in particle interferometry is developed. This formalism is based on a covariant form of Hamilton's action principle and Lagrange's equations of motion. It will be shown that this Lorentz invariant formalism yields a simple perturbation theoretic expression for the general phase shift that arises in matter-wave interferometry. The Lagrangian formalism is compared with the more usual formalism based on the wave propagation vector and frequency. The resulting formalism will be used to analyse the Sagnac effect, gravitational field measurements, and several Aharonov-Bohm-like topological phase shifts. Several topological interferometric experiments using particles of non-zero rest mass are discussed. These experiments involve the use of electrons, neutrons and neutral atoms. Neutron experiments will be emphasised. 45 refs., 15 figs
Vector tomography for reconstructing electric fields with non-zero divergence in bounded domains
Koulouri, Alexandra; Brookes, Mike; Rimpiläinen, Ville
2017-01-01
In vector tomography (VT), the aim is to reconstruct an unknown multi-dimensional vector field using line integral data. In the case of a 2-dimensional VT, two types of line integral data are usually required. These data correspond to integration of the parallel and perpendicular projection of the vector field along the integration lines and are called the longitudinal and transverse measurements, respectively. In most cases, however, the transverse measurements cannot be physically acquired. Therefore, the VT methods are typically used to reconstruct divergence-free (or source-free) velocity and flow fields that can be reconstructed solely from the longitudinal measurements. In this paper, we show how vector fields with non-zero divergence in a bounded domain can also be reconstructed from the longitudinal measurements without the need of explicitly evaluating the transverse measurements. To the best of our knowledge, VT has not previously been used for this purpose. In particular, we study low-frequency, time-harmonic electric fields generated by dipole sources in convex bounded domains which arise, for example, in electroencephalography (EEG) source imaging. We explain in detail the theoretical background, the derivation of the electric field inverse problem and the numerical approximation of the line integrals. We show that fields with non-zero divergence can be reconstructed from the longitudinal measurements with the help of two sparsity constraints that are constructed from the transverse measurements and the vector Laplace operator. As a comparison to EEG source imaging, we note that VT does not require mathematical modeling of the sources. By numerical simulations, we show that the pattern of the electric field can be correctly estimated using VT and the location of the source activity can be determined accurately from the reconstructed magnitudes of the field.
Analytic two-loop results for self-energy- and vertex-type diagrams with one non-zero mass
International Nuclear Information System (INIS)
Fleischer, J.; Kotikov, A.V.; Veretin, O.L.
1999-01-01
For a large class of two-loop self-energy- and vertex-type diagrams with only one non-zero mass (m) and the vertices also with only one non-zero external momentum squared (q 2 ) the first few expansion coefficients are calculated by the large mass expansion. This allows us to 'guess' the general structure of these coefficients and to verify them in terms of certain classes of 'basis elements', which are essentially harmonic sums. Since for this case with only one non-zero mass the large mass expansion and the Taylor series in terms of q 2 are identical, this approach yields analytic expressions of the Taylor coefficients, from which the diagram can be easily evaluated numerically in a large domain of the complex q 2 -plane by well known methods. It is also possible to sum the Taylor series and present the results in terms of polylogarithms
Directory of Open Access Journals (Sweden)
H. Wang
2008-06-01
Full Text Available This study concentrates on the FACs distribution for the varying northward and duskward interplanetary magnetic field (IMF conditions when the dipole tilt is nonzero. A global MHD simulation (the Space Weather Modeling Framework, SWMF has been used to perform this study. Hemispheric asymmetry of the time evolution of northward IMF Bz (NBZ FACs is found. As the IMF changes from strictly northward to duskward, NBZ FACs shift counterclockwise in both summer and winter hemispheres. However, in the winter hemisphere, the counterclockwise rotation prohibits the duskward NBZ FACs from evolving into the midday R1 FACs. The midday R1 FACs seem to be an intrusion of dawnside R1 FACs. In the summer hemisphere, the NBZ FACs can evolve into the DPY FACs, consisting of the midday R0 and R1 FACs, after the counterclockwise rotation. The hemispheric asymmetry is due to the fact that the dipole tilt favors more reconnection between the IMF and the summer magnetosphere. When mapping the NBZ and DPY FACs into the magnetosphere it is found that the NBZ currents are located on both open and closed field lines, irrespective of the IMF direction. For the DPY FACs the hemispheric asymmetry emerges: the midday R1 FACs and a small part of R0 FACs are on closed field lines in the winter hemisphere, while a small part of the midday R1 FACs and all the R0 FACs are on open field lines in the summer hemisphere. Both IMF By and dipole tilt cause the polar cap hemispheric and local time asymmetric. When the IMF is northward, the summer polar cap is closed on the nightside while the winter polar cap is open. The polar cap boundary tends to move equatorward as the IMF rotates from northward to duskward, except in the summer hemisphere, the polar cap on the dawnside shifts poleward when the clock angle is less than 10°. The further poleward displacement of the polar cap boundary on one oval side is caused by the twist of the tail plasma sheet, which is in accordance with the
Vector tomography for reconstructing electric fields with non-zero divergence in bounded domains
Energy Technology Data Exchange (ETDEWEB)
Koulouri, Alexandra, E-mail: koulouri@uni-muenster.de [Institute for Computational and Applied Mathematics, University of Münster, Einsteinstrasse 62, D-48149 Münster (Germany); Department of Electrical and Electronic Engineering, Imperial College London, Exhibition Road, London SW7 2BT (United Kingdom); Brookes, Mike [Department of Electrical and Electronic Engineering, Imperial College London, Exhibition Road, London SW7 2BT (United Kingdom); Rimpiläinen, Ville [Institute for Biomagnetism and Biosignalanalysis, University of Münster, Malmedyweg 15, D-48149 Münster (Germany); Department of Mathematics, University of Auckland, Private bag 92019, Auckland 1142 (New Zealand)
2017-01-15
In vector tomography (VT), the aim is to reconstruct an unknown multi-dimensional vector field using line integral data. In the case of a 2-dimensional VT, two types of line integral data are usually required. These data correspond to integration of the parallel and perpendicular projection of the vector field along the integration lines and are called the longitudinal and transverse measurements, respectively. In most cases, however, the transverse measurements cannot be physically acquired. Therefore, the VT methods are typically used to reconstruct divergence-free (or source-free) velocity and flow fields that can be reconstructed solely from the longitudinal measurements. In this paper, we show how vector fields with non-zero divergence in a bounded domain can also be reconstructed from the longitudinal measurements without the need of explicitly evaluating the transverse measurements. To the best of our knowledge, VT has not previously been used for this purpose. In particular, we study low-frequency, time-harmonic electric fields generated by dipole sources in convex bounded domains which arise, for example, in electroencephalography (EEG) source imaging. We explain in detail the theoretical background, the derivation of the electric field inverse problem and the numerical approximation of the line integrals. We show that fields with non-zero divergence can be reconstructed from the longitudinal measurements with the help of two sparsity constraints that are constructed from the transverse measurements and the vector Laplace operator. As a comparison to EEG source imaging, we note that VT does not require mathematical modeling of the sources. By numerical simulations, we show that the pattern of the electric field can be correctly estimated using VT and the location of the source activity can be determined accurately from the reconstructed magnitudes of the field. - Highlights: • Vector tomography is used to reconstruct electric fields generated by dipole
Flavor origin of dark matter and its relation with leptonic nonzero θ{sub 13} and Dirac CP phase δ
Energy Technology Data Exchange (ETDEWEB)
Bhattacharya, Subhaditya; Karmakar, Biswajit [Department of Physics, Indian Institute of Technology Guwahati,781039 Assam (India); Sahu, Narendra [Department of Physics, Indian Institute of Technology,Hyderabad, Kandi, Sangareddy 502285, Medak, Telengana (India); Sil, Arunansu [Department of Physics, Indian Institute of Technology Guwahati,781039 Assam (India)
2017-05-12
We propose a minimal extension of the standard model by including a U(1) flavor symmetry to establish a correlation between the relic abundance of dark matter, measured by WMAP and PLANCK satellite experiments and non-zero value of sin θ{sub 13} observed at DOUBLE CHOOZ, Daya Bay, RENO and T2K. The flavour symmetry is allowed to be broken at a high scale to a remnant Z{sub 2} symmetry, which not only ensures the stability to the dark matter, but also gives rise to a modification to the existing A{sub 4}-based tri-bimaximal neutrino mixing. This deviation in turn suggests the required non-zero value of sin θ{sub 13}. We assume the dark matter to be neutral under the existing A{sub 4} symmetry while charged under the U(1) flavor symmetry. Hence in this set-up, the non-zero value of sin θ{sub 13} predicts the dark matter charge under U(1), which can be tested at various ongoing and future direct and collider dark matter search experiments. We also point out the involvement of nonzero leptonic CP phase δ, which plays an important role in the analysis.
The effect of non-zero radial velocity on the impulse and circulation of starting jets
Krieg, Michael; Mohseni, Kamran
2011-11-01
Vortex ring formation dynamics are generally studied using two basic types of vortex generators. Piston cylinder vortex generators eject fluid through a long tube which ensures a purely axial jet; whereas, vortex ring generators which expel fluid through a flat plate with a circular orifice produce 2-D jets (non-zero radial velocity). At the nozzle exit plane of the orifice type vortex generator the radial component of velocity is linearly proportional to the radial distance from the axis of symmetry, reaching a maximum at the edge of the orifice with a magnitude around 10 % of the piston velocity (the ratio of the volume flux and the nozzle area). As the jet advances downstream the radial velocity quickly dissipates, and becomes purely axial less than a diameter away from the nozzle exit plane. The radial velocity gradient in the axial direction plays a key role in the rate at which circulation and impulse are ejected from the vortex generator. Though the radial component of velocity is small compared to the axial velocity, it has a significant effect on both the circulation and impulse of the starting jet because of this gradient. The extent of circulation and impulse enhancement is investigated through experimental DPIV data showing that the orifice device produces nearly double both circulation and energy (with identical piston velocity and stroke ratios).
Gravitational instabilities of the cosmic neutrino background with non-zero lepton number
Directory of Open Access Journals (Sweden)
Neil D. Barrie
2017-09-01
Full Text Available We argue that a cosmic neutrino background that carries non-zero lepton charge develops gravitational instabilities. Fundamentally, these instabilities are related to the mixed gravity-lepton number anomaly. We have explicitly computed the gravitational Chern–Simons term which is generated quantum-mechanically in the effective action in the presence of a lepton number asymmetric neutrino background. The induced Chern–Simons term has a twofold effect: (i gravitational waves propagating in such a neutrino background exhibit birefringent behaviour leading to an enhancement/suppression of the gravitational wave amplitudes depending on the polarisation, where the magnitude of this effect is related to the size of the lepton asymmetry; (ii Negative energy graviton modes are induced in the high frequency regime, which leads to very fast vacuum decay producing, e.g., positive energy photons and negative energy gravitons. From the constraint on the present radiation energy density, we obtain an interesting bound on the lepton asymmetry of the universe.
International Nuclear Information System (INIS)
Boche, H.; Nötzel, J.
2014-01-01
This work is motivated by a quite general question: Under which circumstances are the capacities of information transmission systems continuous? The research is explicitly carried out on finite arbitrarily varying quantum channels (AVQCs). We give an explicit example that answers the recent question whether the transmission of messages over AVQCs can benefit from assistance by distribution of randomness between the legitimate sender and receiver in the affirmative. The specific class of channels introduced in that example is then extended to show that the unassisted capacity does have discontinuity points, while it is known that the randomness-assisted capacity is always continuous in the channel. We characterize the discontinuity points and prove that the unassisted capacity is always continuous around its positivity points. After having established shared randomness as an important resource, we quantify the interplay between the distribution of finite amounts of randomness between the legitimate sender and receiver, the (nonzero) probability of a decoding error with respect to the average error criterion and the number of messages that can be sent over a finite number of channel uses. We relate our results to the entanglement transmission capacities of finite AVQCs, where the role of shared randomness is not yet well understood, and give a new sufficient criterion for the entanglement transmission capacity with randomness assistance to vanish
Varotsos, G. K.; Nistazakis, H. E.; Petkovic, M. I.; Djordjevic, G. T.; Tombras, G. S.
2017-11-01
Over the last years terrestrial free-space optical (FSO) communication systems have demonstrated an increasing scientific and commercial interest in response to the growing demands for ultra high bandwidth, cost-effective and secure wireless data transmissions. However, due the signal propagation through the atmosphere, the performance of such links depends strongly on the atmospheric conditions such as weather phenomena and turbulence effect. Additionally, their operation is affected significantly by the pointing errors effect which is caused by the misalignment of the optical beam between the transmitter and the receiver. In order to address this significant performance degradation, several statistical models have been proposed, while particular attention has been also given to diversity methods. Here, the turbulence-induced fading of the received optical signal irradiance is studied through the M (alaga) distribution, which is an accurate model suitable for weak to strong turbulence conditions and unifies most of the well-known, previously emerged models. Thus, taking into account the atmospheric turbulence conditions along with the pointing errors effect with nonzero boresight and the modulation technique that is used, we derive mathematical expressions for the estimation of the average bit error rate performance for SIMO FSO links. Finally, proper numerical results are given to verify our derived expressions and Monte Carlo simulations are also provided to further validate the accuracy of the analysis proposed and the obtained mathematical expressions.
Experience Replay for Optimal Control of Nonzero-Sum Game Systems With Unknown Dynamics.
Zhao, Dongbin; Zhang, Qichao; Wang, Ding; Zhu, Yuanheng
2016-03-01
In this paper, an approximate online equilibrium solution is developed for an N -player nonzero-sum (NZS) game systems with completely unknown dynamics. First, a model identifier based on a three-layer neural network (NN) is established to reconstruct the unknown NZS games systems. Moreover, the identifier weight vector is updated based on experience replay technique which can relax the traditional persistence of excitation condition to a simplified condition on recorded data. Then, the single-network adaptive dynamic programming (ADP) with experience replay algorithm is proposed for each player to solve the coupled nonlinear Hamilton- (HJ) equations, where only the critic NN weight vectors are required to tune for each player. The feedback Nash equilibrium is provided by the solution of the coupled HJ equations. Based on the experience replay technique, a novel critic NN weights tuning law is proposed to guarantee the stability of the closed-loop system and the convergence of the value functions. Furthermore, a Lyapunov-based stability analysis shows that the uniform ultimate boundedness of the closed-loop system is achieved. Finally, two simulation examples are given to verify the effectiveness of the proposed control scheme.
On finitely generated modules whose first nonzero Fitting ideals are regular
Directory of Open Access Journals (Sweden)
Somayeh Hadjirezaei
2018-01-01
Full Text Available A finitely generated $R$-module is said to be a module of type ($F_r$ if its $(r-1$-th Fitting ideal is the zero ideal and its $r$-th Fitting ideal is a regular ideal. Let $R$ be a commutative ring and $N$ be a submodule of $R^n$ which is generated by columns of a matrix $A=(a_{ij}$ with $a_{ij}in R$ for all $1leq ileq n$, $jin Lambda$, where $Lambda $ is a (possibly infinite index set. Let $M=R^n/N$ be a module of type ($F_{n-1}$ and ${rm T}(M$ be the submodule of $M$ consisting of all elements of $M$ that are annihilated by a regular element of $R$. For $ lambdain Lambda $, put $M_lambda=R^n/$. The main result of this paper asserts that if $M_lambda $ is a regular $R$-module, for some $lambdainLambda$, then $M/{rm T}(Mcong M_lambda/{rm T}(M_lambda$. Also it is shown that if $M_lambda$ is a regular torsionfree $R$-module, for some $lambdain Lambda$, then $ Mcong M_lambda. $ As a consequence we characterize all non-torsionfree modules over a regular ring, whose first nonzero Fitting ideals are maximal.
Approximate N-Player Nonzero-Sum Game Solution for an Uncertain Continuous Nonlinear System.
Johnson, Marcus; Kamalapurkar, Rushikesh; Bhasin, Shubhendu; Dixon, Warren E
2015-08-01
An approximate online equilibrium solution is developed for an N -player nonzero-sum game subject to continuous-time nonlinear unknown dynamics and an infinite horizon quadratic cost. A novel actor-critic-identifier structure is used, wherein a robust dynamic neural network is used to asymptotically identify the uncertain system with additive disturbances, and a set of critic and actor NNs are used to approximate the value functions and equilibrium policies, respectively. The weight update laws for the actor neural networks (NNs) are generated using a gradient-descent method, and the critic NNs are generated by least square regression, which are both based on the modified Bellman error that is independent of the system dynamics. A Lyapunov-based stability analysis shows that uniformly ultimately bounded tracking is achieved, and a convergence analysis demonstrates that the approximate control policies converge to a neighborhood of the optimal solutions. The actor, critic, and identifier structures are implemented in real time continuously and simultaneously. Simulations on two and three player games illustrate the performance of the developed method.
Sharper angle, higher risk? The effect of cutting angle on knee mechanics in invasion sport athletes
Schreurs, Mervin J.; Benjaminse, Anne; Lemmink, Koen A. P. M.
2017-01-01
Introduction: Cutting is an important skill in team-sports, but unfortunately is also related to non-contact ACL injuries. The purpose was to examine knee kinetics and kinematics at different cutting angles. Material and methods: 13 males and 16 females performed cuts at different angles (45°, 90°,
Schreurs, Mervin J; Benjaminse, Anne; Lemmink, Koen A P M
2017-10-03
Cutting is an important skill in team-sports, but unfortunately is also related to non-contact ACL injuries. The purpose was to examine knee kinetics and kinematics at different cutting angles. 13 males and 16 females performed cuts at different angles (45°, 90°, 135° and 180°) at maximum speed. 3D kinematics and kinetics were collected. To determine differences across cutting angles (45°, 90°, 135° and 180°) and sex (female, male), a 4×2 repeated measures ANOVA was conducted followed by post hoc comparisons (Bonferroni) with alpha level set at α≤0.05a priori. At all cutting angles, males showed greater knee flexion angles than females (pcutting angles with no differences in the amount of knee flexion -42.53°±8.95°, females decreased their knee flexion angle from -40.6°±7.2° when cutting at 45° to -36.81°±9.10° when cutting at 90°, 135° and 180° (pcutting towards sharper angles (pcutting angles and then stabilized compared to the 45° cutting angle (pcutting to sharper angles (pcutting angles demand different knee kinematics and kinetics. Sharper cutting angles place the knee more at risk. However, females and males handle this differently, which has implications for injury prevention. Copyright © 2017 Elsevier Ltd. All rights reserved.
Generalization of Penrose's helicity theorem for space-times with nonzero dual mass
International Nuclear Information System (INIS)
Magnon, A.
1986-01-01
An algebraic definition of the helicity operator H is proposed for vacuum stationary and asymptotically flat wormholes (i.e., space-times where the manifold of orbits of the stationary Killing field has S 2 x R topology). The definition avoids the use of momentum space or Fourier decomposition of the gravitational degrees of freedom into positive and negative frequency parts, and is essentially geared to emphasize the role of nontrivial topology. It is obtained via the introduction of a total spin vector S/sup α/ derived from the dual Bondi four-momentum *P/sup α/, both vectors originating in the presence of nontrivial homotopy groups. (Space-times with nonzero dual mass can be characterized by a conformal null boundary I having the topology of an S 1 fiber bundle over S 2 with possible identifications along the fiber: lens space: or equivalently vanishing Bondi--News.) It is shown that S/sup α/ is a constant multiple of P/sup α/, the total Bondi four-momentum, and if in addition the space-time admits a point at spacelike infinity, there is strong support for the past limit of S/sup α/ to be a null vector. This can be viewed as a generalization of Penrose's result on the Pauli--Lubanski vector for classical zero rest-mass particles. The helicity operator at null infinity is rooted in the topology and turns out to be essentially the Hodge duality operator(*). The notion of duality appears as a global concept. Under such conditions, self- and anti-self-dual modes of the Weyl curvature could be viewed as states originating in the nontrivial topology
Should tsunami models use a nonzero initial condition for horizontal velocity?
Nava, G.; Lotto, G. C.; Dunham, E. M.
2017-12-01
Tsunami propagation in the open ocean is most commonly modeled by solving the shallow water wave equations. These equations require two initial conditions: one on sea surface height and another on depth-averaged horizontal particle velocity or, equivalently, horizontal momentum. While most modelers assume that initial velocity is zero, Y.T. Song and collaborators have argued for nonzero initial velocity, claiming that horizontal displacement of a sloping seafloor imparts significant horizontal momentum to the ocean. They show examples in which this effect increases the resulting tsunami height by a factor of two or more relative to models in which initial velocity is zero. We test this claim with a "full-physics" integrated dynamic rupture and tsunami model that couples the elastic response of the Earth to the linearized acoustic-gravitational response of a compressible ocean with gravity; the model self-consistently accounts for seismic waves in the solid Earth, acoustic waves in the ocean, and tsunamis (with dispersion at short wavelengths). We run several full-physics simulations of subduction zone megathrust ruptures and tsunamis in geometries with a sloping seafloor, using both idealized structures and a more realistic Tohoku structure. Substantial horizontal momentum is imparted to the ocean, but almost all momentum is carried away in the form of ocean acoustic waves. We compare tsunami propagation in each full-physics simulation to that predicted by an equivalent shallow water wave simulation with varying assumptions regarding initial conditions. We find that the initial horizontal velocity conditions proposed by Song and collaborators consistently overestimate the tsunami amplitude and predict an inconsistent wave profile. Finally, we determine tsunami initial conditions that are rigorously consistent with our full-physics simulations by isolating the tsunami waves (from ocean acoustic and seismic waves) at some final time, and backpropagating the tsunami
International Nuclear Information System (INIS)
Steinberg, R.I.; Liaud, P.; Vignon, B.; Hughes, V.W.
1976-01-01
A detailed description of an experimental test of time-reversal invariance in the β decay of the polarized free neutron is presented. The experiment consists of a measurement of the triple-correlation coefficient D between the neutron polarization vector and the electron and antineutrino momentum vectors. A nonzero value for this coefficient would imply T violation, since final-state interactions and other corrections may be neglected at the present level of precision. The experiment was performed using a cold-neutron beam at the High Flux Reactor of the Institut Laue-Langevin, Grenoble. A polarizing neutron guide tube yielded a beam intensity of 10 9 neutrons/sec with a polarization of 70%. Our result, based upon observation of approximately 6 x 10 6 decays, is D = (-1.1 +- 1.7) x 10 -3 , consistent with time-reversal invariance in the ΔS = 0 weak interaction. In terms of the relative phase angle between axial-vector and vector coupling constants, the result may be expressed as phi = 180.14 +- 0.22 0
... Home » Statistics and Data » Glaucoma, Open-angle Listen Glaucoma, Open-angle Open-angle Glaucoma Defined In open-angle glaucoma, the fluid passes ... 2010 2010 U.S. Age-Specific Prevalence Rates for Glaucoma by Age and Race/Ethnicity The prevalence of ...
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Zhang, Huaguang; Jiang, He; Luo, Chaomin; Xiao, Geyang
2017-10-01
In this paper, we investigate the nonzero-sum games for a class of discrete-time (DT) nonlinear systems by using a novel policy iteration (PI) adaptive dynamic programming (ADP) method. The main idea of our proposed PI scheme is to utilize the iterative ADP algorithm to obtain the iterative control policies, which not only ensure the system to achieve stability but also minimize the performance index function for each player. This paper integrates game theory, optimal control theory, and reinforcement learning technique to formulate and handle the DT nonzero-sum games for multiplayer. First, we design three actor-critic algorithms, an offline one and two online ones, for the PI scheme. Subsequently, neural networks are employed to implement these algorithms and the corresponding stability analysis is also provided via the Lyapunov theory. Finally, a numerical simulation example is presented to demonstrate the effectiveness of our proposed approach.
Finding Non-Zero Stable Fixed Points of the Weighted Kuramoto model is NP-hard
Taylor, Richard
2015-01-01
The Kuramoto model when considered over the full space of phase angles [$0,2\\pi$) can have multiple stable fixed points which form basins of attraction in the solution space. In this paper we illustrate the fundamentally complex relationship between the network topology and the solution space by showing that determining the possibility of multiple stable fixed points from the network topology is NP-hard for the weighted Kuramoto Model. In the case of the unweighted model this problem is shown...
Small angle spectrometers: Summary
International Nuclear Information System (INIS)
Courant, E.; Foley, K.J.; Schlein, P.E.
1986-01-01
Aspects of experiments at small angles at the Superconducting Super Collider are considered. Topics summarized include a small angle spectrometer, a high contingency spectrometer, dipole and toroid spectrometers, and magnet choices
Fabricating customized hydrogel contact lens
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.
Updated BBN bounds on the cosmological lepton asymmetry for non-zero θ13
International Nuclear Information System (INIS)
Mangano, Gianpiero; Miele, Gennaro; Pastor, Sergio; Pisanti, Ofelia; Sarikas, Srdjan
2012-01-01
We discuss the bounds on the cosmological lepton number from Big Bang Nucleosynthesis (BBN), in light of recent evidences for a large value of the neutrino mixing angle θ 13 , sin 2 θ 13 ≥0.01 at 2σ. The largest asymmetries for electron and μ, τ neutrinos compatible with 4 He and 2 H primordial yields are computed versus the neutrino mass hierarchy and mixing angles. The flavour oscillation dynamics is traced till the beginning of BBN and neutrino distributions after decoupling are numerically computed. The latter contains in general, non-thermal distortion due to the onset of flavour oscillations driven by solar squared mass difference in the temperature range where neutrino scatterings become inefficient to enforce thermodynamical equilibrium. Depending on the value of θ 13 , this translates into a larger value for the effective number of neutrinos, N eff . Upper bounds on this parameter are discussed for both neutrino mass hierarchies. Values for N eff which are large enough to be detectable by the Planck experiment are found only for the (presently disfavoured) range sin 2 θ 13 ≤0.01.
Prioritized Contact Transport Stream
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.
Directory of Open Access Journals (Sweden)
Washington Azevêdo da Silva
2007-02-01
starch in biofilms. The aim of this work was to study the color variation, the topographic superficial surface by scanning electron microscopy and the water absorption by contact angle of biofilms produced with three different starch sources: potato starch film (PSF, cassava starch film (CSF and maize starch film (MSF with varied concentration: 1, 2 and 3% to prepare biofilms using a complete randomize design with three repetitions. The interaction between starch source and concentration was statistically significant for contact angle whereas it was not significant for color. The color difference was affected by starch source being higher for CSF. As concentration increased in biofilms of potato and cassava, the contact angle decreased in contrast to maize biofilms which remained constant.
Bianchi type I universe in brane world scenario with non-zero Weyl tensor of the bulk
Energy Technology Data Exchange (ETDEWEB)
Chaudhuri, S. [University of Burdwan, Department of Physics, Burdwan (India)
2017-09-15
In the paper, we present exact solutions of gravitational field equations for an anisotropic brane with a Bianchi type I universe with perfect fluid having non-vanishing Weyl tensor of the bulk. It is assumed that the thermodynamic pressure bears a linear relation with the energy density. For a particular non-zero value of the pressure the solutions are obtained in an exact analytic form with and without the cosmological constant for a Bianchi type I universe. The relevant physical quantities associated with the evolution of the universe are also derived in the two cases. (orig.)
Contact Angle Influence on Geysering Jets in Microgravity Investigated
Chato, David J.
2004-01-01
Microgravity poses many challenges to the designer of spacecraft tanks. Chief among these are the lack of phase separation and the need to supply vapor-free liquid or liquid-free vapor to the spacecraft processes that require fluid. One of the principal problems of phase separation is the creation of liquid jets. A jet can be created by liquid filling, settling of the fluid to one end of the tank, or even closing a valve to stop the liquid flow. Anyone who has seen a fountain knows that jets occur in normal gravity also. However, in normal gravity, the gravity controls and restricts the jet flow. In microgravity, with gravity largely absent, surface tension forces must be used to contain jets. To model this phenomenon, a numerical method that tracks the fluid motion and the surface tension forces is required. Jacqmin has developed a phase model that converts the discrete surface tension force into a barrier function that peaks at the free surface and decays rapidly away. Previous attempts at this formulation were criticized for smearing the interface. This can be overcome by sharpening the phase function, double gridding the fluid function, and using a higher-order solution for the fluid function. The solution of this equation can be rewritten as two coupled Poisson equations that also include the velocity.
Contact angle dependence on the fluid-wall dispersive energy
Horsch, M.; Heitzig, M.; Dan, C.M.; Harting, J.D.R.; Hasse, H.; Vrabec, J.
2010-01-01
Menisci of the truncated and shifted Lennard-Jones fluid between parallel planar walls are investigated by molecular dynamics simulation. Thereby, the characteristic energy of the unlike dispersive interaction between fluid molecules and wall atoms is systematically varied to determine its influence
Contact angle determination in multicomponent lattice Boltzmann simultations
Schmieschek, S.M.P.; Harting, J.D.R.
2011-01-01
Droplets on hydrophobic surfaces are ubiquitous in microfluidic applications and there exists a number of commonly used multicomponent and multiphase lattice Boltzmann schemes to study such systems. In this paper we focus on a popular implementation of a multicomponent model as introduced by Shan
Capillary Contact Angle in a Completely Wet Groove
Czech Academy of Sciences Publication Activity Database
Parry, A.O.; Malijevský, Alexandr; Rascón, C.
2014-01-01
Roč. 113, č. 14 (2014), s. 146101 ISSN 0031-9007 R&D Projects: GA ČR GA13-09914S Grant - others:EPSRC UK(GB) EP/J009636/1; SSF(ES) FIS2010-22047-C05 Institutional support: RVO:67985858 Keywords : phase equilibria * wetting transitions * narrow pores Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 7.512, year: 2014
Contact angle hysteresis of liquid drops as means to measure ...
Indian Academy of Sciences (India)
ferent plasticizers like glycerol and sorbitol have been used to form mixed films with zein and properties of these ... many applications including lubrication, coating, printing, water proofing and de- tergency [1–3]. ..... [2] P Hiemencz and R Rajagopalan, Principles of colloid and surface chemistry (Dekker,. New York, 1997) p.
Crystalline misfit-angle implications for solid sliding
International Nuclear Information System (INIS)
Manini, Nicola; Braun, O.M.
2011-01-01
For the contact of two finite portions of interacting rigid crystalline surfaces, we compute the pinning energy barrier dependency on the misfit angle and contact area. This simple model allows us to investigate a broad contact-size and angular range, thus obtaining the statistical properties of the energy barriers opposing sliding for a single asperity. These data are used to generate the distribution of static frictional thresholds for the contact of polycrystals, as in dry or even lubricated friction. This distribution is used as the input of a master equation to predict the sliding properties of macroscopic contacts. -- Highlights: → The pinning energy barrier depends on the misfit angle and contact area. → We compute this dependence for a idealized rigid model. → We obtain a distribution of static frictional thresholds. → It is used as input of a master-equation model for macroscopic surfaces in contact. → Overall we predict a transition from stick-slip to smooth sliding.
Optical fibre angle sensor used in MEMS
International Nuclear Information System (INIS)
Golebiowski, J; Milcarz, Sz; Rybak, M
2014-01-01
There is a need for displacement and angle measurements in many movable MEMS structures. The use of fibre optical sensors helps to measure micrometre displacements and small rotation angles. Advantages of this type of transducers are their simple design, high precision of processing, low costs and ability of a non-contact measurement. The study shows an analysis of a fibre-optic intensity sensor used for MEMS movable structure rotation angle measurement. An intensity of the light in the photodetector is basically dependent on a distance between a reflecting surface and a head surface of the fibre transmitting arm, and the deflection angle. Experimental tests were made for PMMA 980/1000 plastic fibres, Θ NA =33°. The study shows both analytical and practical results. It proves that calculated and experimental characteristics for the analysed transducers are similar.
The long-term stability of self-esteem: its time-dependent decay and nonzero asymptote.
Kuster, Farah; Orth, Ulrich
2013-05-01
How stable are individual differences in self-esteem? We examined the time-dependent decay of rank-order stability of self-esteem and tested whether stability asymptotically approaches zero or a nonzero value across long test-retest intervals. Analyses were based on 6 assessments across a 29-year period of a sample of 3,180 individuals aged 14 to 102 years. The results indicated that, as test-retest intervals increased, stability exponentially decayed and asymptotically approached a nonzero value (estimated as .43). The exponential decay function explained a large proportion of variance in observed stability coefficients, provided a better fit than alternative functions, and held across gender and for all age groups from adolescence to old age. Moreover, structural equation modeling of the individual-level data suggested that a perfectly stable trait component underlies stability of self-esteem. The findings suggest that the stability of self-esteem is relatively large, even across very long periods, and that self-esteem is a trait-like characteristic.
Energy Technology Data Exchange (ETDEWEB)
Quintella, Cristina M.; Castro, Martha T.P.O.; Musse, Ana Paula S. [Universidade Federal da Bahia, Salvador, BA (Brazil)
2003-07-01
This work evaluated the formation of paraffin deposits as a function of the chemical constitution of the pipeline walls. Two low cost polymers, available in the Brazilian market either as solids or as extruded films, were studied: polypropylene (PP) and high density polyethylene (PEAD). The static interfacial interactions were evaluated by contact angle and showed that the interaction between crude oil and PEAD was 16% stronger than with PP. For the dynamic studies a flow cell was developed in order to observe mainly the boundary layers. The paraffin deposits were identified through the decrease of the intermolecular alignment within the flowing oil. PEAD proved to be 43% more efficient that PP in interacting with the crude oil. Under flowing conditions, the chemical interfacial effects became more pronounced due to the molecular effects overcoming the hydrodynamic effects. Photos of the cell walls showed globular paraffin deposits on PEAD and their absence on PP. As both polymers are linear, the higher tendency of PEAD to yield paraffin deposits was attributed to the absence of lateral branches of methyl groups. There by PP was found to be better than PEAD to avoid paraffin deposition. (author)
International Nuclear Information System (INIS)
Cook, G.O. Jr.; Knight, L.
1979-07-01
The question of optimal projection angles has recently become of interest in the field of reconstruction from projections. Here, studies are concentrated on the n x n pixel space, where literative algorithms such as ART and direct matrix techniques due to Katz are considered. The best angles are determined in a Gauss--Markov statistical sense as well as with respect to a function-theoretical error bound. The possibility of making photon intensity a function of angle is also examined. Finally, the best angles to use in an ART-like algorithm are studied. A certain set of unequally spaced angles was found to be preferred in several contexts. 15 figures, 6 tables
... Consumers Consumer Information by Audience For Women Contact Lens Care Share Tweet Linkedin Pin it More sharing ... www.fda.gov/medwatch Learn More about Contact Lens Care Other Tips on Contact Lenses Decorative Contact ...
Semileptonic B to D Decays at Nonzero Recoil with 2+1 Flavors of Improved Staggered Quarks
International Nuclear Information System (INIS)
Qiu, Si-Wei; DeTar, Carleton; Du, Daping; Kronfeld, Andreas S.; Laiho, Jack; Van de Water, Ruth S.
2011-01-01
The Fermilab Lattice-MILC collaboration is completing a comprehensive program of heavy-light physics on the MILC (2+1)-flavor asqtad ensembles with lattice spacings as small as 0.045 fm and light-to-strange-quark mass ratios as low as 1/20. We use the Fermilab interpretation of the clover action for heavy valence quarks and the asqtad action for light valence quarks. The central goal of the program is to provide ever more exacting tests of the unitarity of the CKM matrix. We give a progress report on one part of the program, namely the analysis of the semileptonic decay B to D at both zero and nonzero recoil. Although final results are not presented, we discuss improvements in the analysis methods, the statistical errors, and the parameter coverage that we expect will lead to a significant reduction in the final error for |V cb | from this decay channel.
International Nuclear Information System (INIS)
Akemann, Gernot; Bittner, Elmar
2006-01-01
We compare analytic predictions of non-Hermitian chiral random matrix theory with the complex Dirac operator eigenvalue spectrum of two-color lattice gauge theory with dynamical fermions at nonzero chemical potential. The Dirac eigenvalues come in complex conjugate pairs, making the action of this theory real and positive for our choice of two staggered flavors. This enables us to use standard Monte Carlo simulations in testing the influence of the chemical potential and quark mass on complex eigenvalues close to the origin. We find excellent agreement between the analytic predictions and our data for two different volumes over a range of chemical potentials below the chiral phase transition. In particular, we detect the effect of unquenching when going to very small quark masses
DEFF Research Database (Denmark)
Risager, Morten S.; Södergren, Carl Anders
2017-01-01
It is well known that the angles in a lattice acting on hyperbolic n -space become equidistributed. In this paper we determine a formula for the pair correlation density for angles in such hyperbolic lattices. Using this formula we determine, among other things, the asymptotic behavior of the den......It is well known that the angles in a lattice acting on hyperbolic n -space become equidistributed. In this paper we determine a formula for the pair correlation density for angles in such hyperbolic lattices. Using this formula we determine, among other things, the asymptotic behavior...... of the density function in both the small and large variable limits. This extends earlier results by Boca, Pasol, Popa and Zaharescu and Kelmer and Kontorovich in dimension 2 to general dimension n . Our proofs use the decay of matrix coefficients together with a number of careful estimates, and lead...
Occupational contact urticaria and protein contact dermatitis.
Doutre, Marie-Sylvie
2005-01-01
Irritant dermatitis and eczema are the most prevalent occupational skin diseases. Less common are immediate contact reactions such as contact urticaria and protein contact dermatitis. Occupational contact urticaria can be subdivided into two categories, immunological and non immunological. However, some agents can induce these two types of reactions. Contact urticaria to natural rubber latex is particularly frequent among health care personnel, but contact urticaria to a wide variety of other substances occurs in many other occupations. Among those at risk are cooks, bakers, butchers, restaurant personnel, veterinarians, hairdressers, florists, gardeners, and forestry workers. Protein contact dermatitis in some of these occupations is caused principally by proteins of animal or plant origin, especially among individuals with a history of atopic dermatitis. Diagnosis requires careful interrogation, clinical examination and skin tests (open tests and prick tests with immediate lecture) to identify a particular contact allergen.
Beam dynamics of the interaction region solenoid in a linear collider due to a crossing angle
Directory of Open Access Journals (Sweden)
P. Tenenbaum
2003-06-01
Full Text Available Future linear colliders may require a nonzero crossing angle between the two beams at the interaction point (IP. This requirement in turn implies that the beams will pass through the strong interaction region solenoid with an angle, and thus that the component of the solenoidal field perpendicular to the beam trajectory is nonzero. The interaction of the beam and the solenoidal field in the presence of a crossing angle will cause optical effects not observed for beams passing through the solenoid on axis; these effects include dispersion, deflection of the beam, and synchrotron radiation effects. For a purely solenoidal field, the optical effects which are relevant to luminosity exactly cancel at the IP when the influence of the solenoid’s fringe field is taken into account. Beam size growth due to synchrotron radiation in the solenoid is proportional to the fifth power of the product of the solenoidal field, the length of the solenoid, and the crossing angle. Examples based on proposed linear collider detector solenoid configurations are presented.
Full Text Available ... One Use Facts About Colored Contacts and Halloween Safety Colored Contact Lens Facts Over-the-Counter Costume ... Costume Contact Lenses Can Ruin Vision Eye Makeup Safety In fact, it is illegal to sell colored ...
Full Text Available ... One Use Facts About Colored Contacts and Halloween Safety Colored Contact Lens Facts Over-the-Counter Costume ... use of colored contact lenses , from the U.S. Food and Drug Administration (FDA). Are the colored lenses ...
DEFF Research Database (Denmark)
Miles, James Edward; Frederiksen, Jane V.; Jensen, Bente Rona
2012-01-01
: Pelvic limbs from red foxes (Vulpes vulpes). METHODS: Q angles were measured on hip dysplasia (HD) and whole limb (WL) view radiographs of each limb between the acetabular rim, mid-point (Q1: patellar center, Q2: femoral trochlea), and tibial tuberosity. Errors of 0.5-2.0 mm at measurement landmarks...
African Journals Online (AJOL)
there is a build up of pressure due to poor outflow of aqueous humor. The outflow obstruction could occur at the trabecular meshwork of the anterior chamber angle or subsequently in the episcleral vein due to raised venous pressure. Such build up of pressure results in glaucoma . Elevated intraocular pressure remains the ...
DEFF Research Database (Denmark)
Morgan, Jeannie; Lynnerup, Niels; Hoppa, R.D.
2013-01-01
measurements taken from computed tomography (CT) scans. Previous reports have observed that the lateral angle size in females is significantly larger than in males. The method was applied to an independent series of 77 postmortem CT scans (42 males, 35 females) to validate its accuracy and reliability...... method appears to be of minimal practical use in forensic anthropology and archeology....
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 17; Issue 9. At Right Angles. Shailesh A Shirali. Information and Announcements Volume 17 Issue 9 September 2012 pp 920-920. Fulltext. Click here to view fulltext PDF. Permanent link: https://www.ias.ac.in/article/fulltext/reso/017/09/0920-0920 ...
International Nuclear Information System (INIS)
Kantrowitz, A.
1976-01-01
A method and apparatus is described for particle separation. The method uses a wide angle radially expanding vapor of a particle mixture. In particular, selective ionization of one isotope type in the particle mixture is produced in a multichamber separator and the ionized isotope type is accelerated out of the path of the vapor expansion for separate collection
Maelger, J.; Reinosa, U.; Serreau, J.
2018-04-01
We extend a previous investigation [U. Reinosa et al., Phys. Rev. D 92, 025021 (2015), 10.1103/PhysRevD.92.025021] of the QCD phase diagram with heavy quarks in the context of background field methods by including the two-loop corrections to the background field effective potential. The nonperturbative dynamics in the pure-gauge sector is modeled by a phenomenological gluon mass term in the Landau-DeWitt gauge-fixed action, which results in an improved perturbative expansion. We investigate the phase diagram at nonzero temperature and (real or imaginary) chemical potential. Two-loop corrections yield an improved agreement with lattice data as compared to the leading-order results. We also compare with the results of nonperturbative continuum approaches. We further study the equation of state as well as the thermodynamic stability of the system at two-loop order. Finally, using simple thermodynamic arguments, we show that the behavior of the Polyakov loops as functions of the chemical potential complies with their interpretation in terms of quark and antiquark free energies.
International Nuclear Information System (INIS)
Lenaghan, J.T.; Rischke, D.H.
2000-01-01
The temperature dependence of the sigma meson and pion masses is studied in the framework of the O(N ) model. The Cornwall-Jackiw-Tomboulis formalism is applied to derive gap equations for the masses in the Hartree and large-N approximations. Renormalization of the gap equations is carried out within the cut-off and counter-term renormalization schemes. A consistent renormalization of the gap equations within the cut-off scheme is found to be possible only in the large-N approximation and for a finite value of the cut-off. On the other hand, the counter-term scheme allows for a consistent renormalization of both the large-N and Hartree approximations. In these approximations, the meson masses at a given nonzero temperature depend in general on the choice of the cut-off or renormalization scale. As an application, we also discuss the in-medium on-shell decay widths for sigma mesons and pions at rest. (author)
A two-component wave equation for particles of spin 1/2 and non-zero rest mass
International Nuclear Information System (INIS)
Srivastava, T.
1981-11-01
We have discussed here the qualifications of the equation (delta 0 +sigmasup(k)deltasub(k))psi = -kappaTpsi, where deltasub(μ) is identical to delta/deltaxsup(μ), sigmasup(k) are the Pauli spin matrices, T is the linear operator which changes the sign of t, kappa=m 0 c/(h/2π) and psi a function with two components, as a suitable wave equation for a spin 1/2 particle with non-zero rest mass. We have established that both components of all its solutions satisfy the Klein-Gordon equation and that a 1-1 correspondence can be set up between its solutions and the positive energy solutions of the Dirac equation which preserves inner products (suitably defined for our case). We have then gone on to show covariance under transformations of the proper Lorentz group as also under space and time inversions and translations. Eigenfunctions of energy-momentum and spin have been explicitly found and it is shown that causality is preserved and a Green's function exists. A list appears, at the end, of points to be discussed in Part II of this paper, points which, it is hoped, will complete the acceptability of the theory. (author)
Klimchitskaya, G. L.; Mostepanenko, V. M.; Petrov, V. M.
2017-12-01
The complete theory of electrical conductivity of graphene at arbitrary temperature is developed with taking into account mass-gap parameter and chemical potential. Both the in-plane and out-of-plane conductivities of graphene are expressed via the components of the polarization tensor in (2+1)-dimensional space-time analytically continued to the real frequency axis. Simple analytic expressions for both the real and imaginary parts of the conductivity of graphene are obtained at zero and nonzero temperature. They demonstrate an interesting interplay depending on the values of mass gap and chemical potential. In the local limit, several results obtained earlier using various approximate and phenomenological approaches are reproduced, refined, and generalized. The numerical computations of both the real and imaginary parts of the conductivity of graphene are performed to illustrate the obtained results. The analytic expressions for the conductivity of graphene obtained in this paper can serve as a guide in the comparison between different theoretical approaches and between experiment and theory.
Phonon self-energy corrections to non-zero wavevector phonon modes in single-layer graphene
Araujo, Paulo; Mafra, Daniela; Sato, Kentaro; Saito, Richiiro; Kong, Jing; Dresselhaus, Mildred
2012-02-01
Phonon self-energy corrections have mostly been studied theoretically and experimentally for phonon modes with zone-center (q = 0) wave-vectors. Here, gate-modulated Raman scattering is used to study phonons of a single layer of graphene (1LG) in the frequency range from 2350 to 2750 cm-1, which shows the G* and the G'-band features originating from a double-resonant Raman process with q 0. The observed phonon renormalization effects are different from what is observed for the zone-center q = 0 case. To explain our experimental findings, we explored the phonon self-energy for the phonons with non-zero wave-vectors (q 0) in 1LG in which the frequencies and decay widths are expected to behave oppositely to the behavior observed in the corresponding zone-center q = 0 processes. Within this framework, we resolve the identification of the phonon modes contributing to the G* Raman feature at 2450 cm-1 to include the iTO+LA combination modes with q 0 and the 2iTO overtone modes with q = 0, showing both to be associated with wave-vectors near the high symmetry point K in the Brillouin zone.
Phonon Self-Energy Corrections to Nonzero Wave-Vector Phonon Modes in Single-Layer Graphene
Araujo, P. T.; Mafra, D. L.; Sato, K.; Saito, R.; Kong, J.; Dresselhaus, M. S.
2012-07-01
Phonon self-energy corrections have mostly been studied theoretically and experimentally for phonon modes with zone-center (q=0) wave vectors. Here, gate-modulated Raman scattering is used to study phonons of a single layer of graphene originating from a double-resonant Raman process with q≠0. The observed phonon renormalization effects are different from what is observed for the zone-center q=0 case. To explain our experimental findings, we explored the phonon self-energy for the phonons with nonzero wave vectors (q≠0) in single-layer graphene in which the frequencies and decay widths are expected to behave oppositely to the behavior observed in the corresponding zone-center q=0 processes. Within this framework, we resolve the identification of the phonon modes contributing to the G⋆ Raman feature at 2450cm-1 to include the iTO+LA combination modes with q≠0 and also the 2iTO overtone modes with q=0, showing both to be associated with wave vectors near the high symmetry point K in the Brillouin zone.
The chiral critical line of $N_{f}=2+1$ QCD at ero and non-zero baryon density
De Forcrand, Philippe; Forcrand, Philippe de; Philipsen, Owe
2007-01-01
We present numerical results for the location of the chiral critical line at finite temperature and zero and non-zero baryon density for QCD with N_f=2+1 flavours of staggered fermions on lattices with temporal extent N_t=4. For degenerate quark masses, we compare our results obtained with the exact RHMC algorithm with earlier, inexact R-algorithm results and find a reduction of 25% in the critical quark mass, for which the first order phase transition changes to a smooth crossover. Extending our analysis to non-degenerate quark masses, we map out the chiral critical line up to the neighbourhood of the physical point, which we confirm to be in the crossover region. Our data are consistent with a tricritical point at a strange quark mass of ~500 MeV. Finally, we investigate the shift of the critical line with finite baryon density, by simulating with an imaginary chemical potential for which there is no sign problem. We observe this shift to be very small or, conversely, the critical endpoint \\mu^c(m_{u,d},m_s...
Directory of Open Access Journals (Sweden)
Mei-Yu LEE
2014-11-01
Full Text Available This paper investigates the effect of the nonzero autocorrelation coefficients on the sampling distributions of the Durbin-Watson test estimator in three time-series models that have different variance-covariance matrix assumption, separately. We show that the expected values and variances of the Durbin-Watson test estimator are slightly different, but the skewed and kurtosis coefficients are considerably different among three models. The shapes of four coefficients are similar between the Durbin-Watson model and our benchmark model, but are not the same with the autoregressive model cut by one-lagged period. Second, the large sample case shows that the three models have the same expected values, however, the autoregressive model cut by one-lagged period explores different shapes of variance, skewed and kurtosis coefficients from the other two models. This implies that the large samples lead to the same expected values, 2(1 – ρ0, whatever the variance-covariance matrix of the errors is assumed. Finally, comparing with the two sample cases, the shape of each coefficient is almost the same, moreover, the autocorrelation coefficients are negatively related with expected values, are inverted-U related with variances, are cubic related with skewed coefficients, and are U related with kurtosis coefficients.
Dynamics of the Molten Contact Line
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
Deep learning methods for protein torsion angle prediction.
Li, Haiou; Hou, Jie; Adhikari, Badri; Lyu, Qiang; Cheng, Jianlin
2017-09-18
Deep learning is one of the most powerful machine learning methods that has achieved the state-of-the-art performance in many domains. Since deep learning was introduced to the field of bioinformatics in 2012, it has achieved success in a number of areas such as protein residue-residue contact prediction, secondary structure prediction, and fold recognition. In this work, we developed deep learning methods to improve the prediction of torsion (dihedral) angles of proteins. We design four different deep learning architectures to predict protein torsion angles. The architectures including deep neural network (DNN) and deep restricted Boltzmann machine (DRBN), deep recurrent neural network (DRNN) and deep recurrent restricted Boltzmann machine (DReRBM) since the protein torsion angle prediction is a sequence related problem. In addition to existing protein features, two new features (predicted residue contact number and the error distribution of torsion angles extracted from sequence fragments) are used as input to each of the four deep learning architectures to predict phi and psi angles of protein backbone. The mean absolute error (MAE) of phi and psi angles predicted by DRNN, DReRBM, DRBM and DNN is about 20-21° and 29-30° on an independent dataset. The MAE of phi angle is comparable to the existing methods, but the MAE of psi angle is 29°, 2° lower than the existing methods. On the latest CASP12 targets, our methods also achieved the performance better than or comparable to a state-of-the art method. Our experiment demonstrates that deep learning is a valuable method for predicting protein torsion angles. The deep recurrent network architecture performs slightly better than deep feed-forward architecture, and the predicted residue contact number and the error distribution of torsion angles extracted from sequence fragments are useful features for improving prediction accuracy.
Complete 360° circumferential SSOCT gonioscopy of the iridocorneal angle
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.
Contact Dermatitis in Pediatrics.
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.]. Copyright 2016, SLACK Incorporated.
Anterior Segment Imaging Predicts Incident Gonioscopic Angle Closure.
Baskaran, Mani; Iyer, Jayant V; Narayanaswamy, Arun K; He, Yingke; Sakata, Lisandro M; Wu, Renyi; Liu, Dianna; Nongpiur, Monisha E; Friedman, David S; Aung, Tin
2015-12-01
To investigate the incidence of gonioscopic angle closure after 4 years in subjects with gonioscopically open angles but varying degrees of angle closure detected on anterior segment optical coherence tomography (AS OCT; Visante; Carl Zeiss Meditec, Dublin, CA) at baseline. Prospective, observational study. Three hundred forty-two subjects, mostly Chinese, 50 years of age or older, were recruited, of whom 65 were controls with open angles on gonioscopy and AS OCT at baseline, and 277 were cases with baseline open angles on gonioscopy but closed angles (1-4 quadrants) on AS OCT scans. All subjects underwent gonioscopy and AS OCT at baseline (horizontal and vertical single scans) and after 4 years. The examiner performing gonioscopy was masked to the baseline and AS OCT data. Angle closure in a quadrant was defined as nonvisibility of the posterior trabecular meshwork by gonioscopy and visible iridotrabecular contact beyond the scleral spur in AS OCT scans. Gonioscopic angle closure in 2 or 3 quadrants after 4 years. There were no statistically significant differences in age, ethnicity, or gender between cases and controls. None of the control subjects demonstrated gonioscopic angle closure after 4 years. Forty-eight of the 277 subjects (17.3%; 95% confidence interval [CI], 12.8-23; P < 0.0001) with at least 1 quadrant of angle closure on AS OCT at baseline demonstrated gonioscopic angle closure in 2 or more quadrants, whereas 28 subjects (10.1%; 95% CI, 6.7-14.6; P < 0.004) demonstrated gonioscopic angle closure in 3 or more quadrants after 4 years. Individuals with more quadrants of angle closure on baseline AS OCT scans had a greater likelihood of gonioscopic angle closure developing after 4 years (P < 0.0001, chi-square test for trend for both definitions of angle closure). Anterior segment OCT imaging at baseline predicts incident gonioscopic angle closure after 4 years among subjects who have gonioscopically open angles and iridotrabecular contact on AS OCT at
Small angle neutron scattering
International Nuclear Information System (INIS)
Bernardini, G.; Cherubini, G.; Fioravanti, A.; Olivi, A.
1976-09-01
A method for the analysis of the data derived from neutron small angle scattering measurements has been accomplished in the case of homogeneous particles, starting from the basic theory without making any assumption on the form of particle size distribution function. The experimental scattering curves are interpreted with the aid the computer by means of a proper routine. The parameters obtained are compared with the corresponding ones derived from observations at the transmission electron microscope
International Nuclear Information System (INIS)
Qiu, S.; Amano, H.; Kasai, A.
1988-01-01
The solid angle in extended alpha source measurement for a series of counting geometries has been obtained by two methods: (1) calculated by means of the Nelson Blachmen series; (2) interpolated from the data table given by Gardner. A particular consequence of the application of the Nelson Blachmen series was deduced which was different from that given by the original author. The applicability of these two methods, as well as an experimentally measured method, is also evaluated. (author)
Contact mechanics: contact area and interfacial separation from small contact to full contact
International Nuclear Information System (INIS)
Yang, C; Persson, B N J
2008-01-01
We present a molecular dynamics study of the contact between a rigid solid with a randomly rough surface and an elastic block with a flat surface. The numerical calculations mainly focus on the contact area and the interfacial separation from small contact (low load) to full contact (high load). For a small load the contact area varies linearly with the load and the interfacial separation depends logarithmically on the load. For a high load the contact area approaches the nominal contact area (i.e. complete contact), and the interfacial separation approaches zero. The numerical results have been compared with analytical theory and experimental results. They are in good agreement with each other. The present findings may be very important for soft solids, e.g. rubber, or for very smooth surfaces, where complete contact can be reached at moderately high loads without plastic deformation of the solids
Directory of Open Access Journals (Sweden)
Chokri Hadj Belgacem
2017-03-01
Full Text Available Using the Lambert W function, the quadratic resisted projectile motion with an approximation of low-angle trajectory has been studied where the launching point is assumed to be higher than the landing point. Analytical solutions for the range and the time of flight are presented in terms of the secondary branch of the Lambert function W−1.
The influence of flip angle on the magic angle effect
International Nuclear Information System (INIS)
Zurlo, J.V.; Blacksin, M.F.; Karimi, S.
2000-01-01
Objective. To assess the impact of flip angle with gradient sequences on the ''magic angle effect''. We characterized the magic angle effect in various gradient echo sequences and compared the signal- to-noise ratios present on these sequences with the signal-to-noise ratios of spin echo sequences.Design. Ten normal healthy volunteers were positioned such that the flexor hallucis longus tendon remained at approximately at 55 to the main magnetic field (the magic angle). The tendon was imaged by a conventional spin echo T1- and T2-weighted techniques and by a series of gradient techniques. Gradient sequences were altered by both TE and flip angle. Signal-to-noise measurements were obtained at segments of the flexor hallucis longus tendon demonstrating the magic angle effect to quantify the artifact. Signal-to-noise measurements were compared and statistical analysis performed. Similar measurements were taken of the anterior tibialis tendon as an internal control.Results and conclusions. We demonstrated the magic angle effect on all the gradient sequences. The intensity of the artifact was affected by both the TE and flip angle. Low TE values and a high flip angle demonstrated the greatest magic angle effect. At TE values less than 30 ms, a high flip angle will markedly increase the magic angle effect. (orig.)
Bacterial adhesion capacity on food service contact surfaces.
Fink, Rok; Okanovič, Denis; Dražič, Goran; Abram, Anže; Oder, Martina; Jevšnik, Mojca; Bohinc, Klemen
2017-06-01
The aim of this study was to analyse the adhesion of E. coli, P. aeruginosa and S. aureus on food contact materials, such as polyethylene terephthalate, silicone, aluminium, Teflon and glass. Surface roughness, streaming potential and contact angle were measured. Bacterial properties by contact angle and specific charge density were characterised. The bacterial adhesion analysis using staining method and scanning electron microscopy showed the lowest adhesion on smooth aluminium and hydrophobic Teflon for most of the bacteria. However, our study indicates that hydrophobic bacteria with high specific charge density attach to those surfaces more intensively. In food services, safety could be increased by selecting material with low adhesion to prevent cross contamination.
Directory of Open Access Journals (Sweden)
T.-T. Phu
2016-12-01
Full Text Available In this paper, we evaluate probability of non-zero secrecy capacity of multi-hop relay networks over Nakagami-m fading channels in presence of hardware impairments. In the considered protocol, a source attempts to transmit its data to a destination by using multi-hop randomize-and-forward (RF strategy. The data transmitted by the source and relays are overheard by an eavesdropper. For performance evaluation, we derive exact expressions of probability of non-zero secrecy capacity (PoNSC, which are expressed by sums of infinite series of exponential functions and exponential integral functions. We then perform Monte Carlo simulations to verify the theoretical analysis.
Chen, Jiangwei; Dai, Yuyao; Yan, Lin; Zhao, Huimin
2018-04-01
In this paper, we shall demonstrate theoretically that steady bound electromagnetic eigenstate can arise in an infinite homogeneous isotropic linear metamaterial with zero-real-part-of-impedance and nonzero-imaginary-part-of-wave-vector, which is partly attributed to that, here, nonzero-imaginary-part-of-wave-vector is not involved with energy losses or gain. Altering value of real-part-of-impedance of the metamaterial, the bound electromagnetic eigenstate may become to be a progressive wave. Our work may be useful to further understand energy conversion and conservation properties of electromagnetic wave in the dispersive and absorptive medium and provides a feasible route to stop, store and release electromagnetic wave (light) conveniently by using metamaterial with near-zero-real-part-of-impedance.
Spin Valve Systems for Angle Sensor Applications
Johnson, Andrew
2004-01-01
A contact-less sensor with the ability to measure over a 360° range has been long sought after in the automotive industry. Such a sensor could be realized by utilizing the angle dependence of the Giant Magneto Resistance (GMR) Effect in a special type of magnetic multilayer called a spin valve arranged in a wheatstone bridge circuit [Spo96]. A spin valve consists of two ferromagnetic layers separated by nonmagnetic spacer layer where the magnetization of one of the ferromagnetic layers is pin...
Full Text Available ... Cleveland. "This is far from the truth." Real People, Real Problems with Colored Contact Lenses Julian: Teenager ... about the members of the eye-care team . Consumer warning about the improper use of colored contact ...
Full Text Available ... One Use Facts About Colored Contacts and Halloween Safety Colored Contact Lens Facts Over-the-Counter Costume ... new application of artificial intelligence shows whether a patient’s eyes point to high blood pressure or risk ...
Full Text Available ... Costume Contacts May Contain Chemicals Harmful to Eyes Four Ways Over-the-Counter Costume Contact Lenses Can ... was in severe pain and on medication for four weeks, and couldn't see well enough to ...
Full Text Available ... sell contacts without a prescription are breaking the law, and may be fined $11,000 per violation. " ... wear any kind of contact lens. In Butler's case, the lenses caused an infection and left her ...
Full Text Available ... Hazard: The Hidden Dangers of Buying Decorative Contact Lenses Without a Prescription Leer en Español: Peligros asociados ... truth." Real People, Real Problems with Colored Contact Lenses Julian: Teenager Blinded In One Eye By Non- ...
... Hazard: The Hidden Dangers of Buying Decorative Contact Lenses Without a Prescription Leer en Español: Peligros asociados ... truth." Real People, Real Problems with Colored Contact Lenses Julian: Teenager Blinded In One Eye By Non- ...
Full Text Available ... Cleveland. "This is far from the truth." Real People, Real Problems with Colored Contact Lenses Julian: Teenager ... the lenses. Never share contact lenses with another person. Get follow up exams with your eye care ...
Full Text Available ... like a suction cup." Halloween is a popular time for people to use colored contact lenses to ... wear costume contact lenses for Halloween or any time of year, follow these guidelines: Get an eye ...
Full Text Available ... glow-in-the-dark lizard lenses, costume contacts can certainly add a spooky, eye-popping touch. But ... consideration as a standard contact lens because they can be purchased over-the-counter or on the ...
Full Text Available ... contact lenses , from the U.S. Food and Drug Administration (FDA). Are the colored lenses you are considering ... Follow The Academy Professionals: Education Guidelines News Multimedia Public & Patients: Contact Us About the Academy Jobs at ...
Full Text Available ... not require the same level of care or consideration as a standard contact lens because they can ... sell contacts without a prescription are breaking the law, and may be fined $11,000 per violation. " ...
This picture shows a skin inflammation (dermatitis) caused by contact with a material that causes an allergic reaction in this person. Contact dermatitis is a relatively common condition, and can be caused ...
Contact materials for nanoelectronics
Alshareef, Husam N.; Quevedo-Ló pez, Manuel Angel Quevedo; Majhi, Prashant
2011-01-01
In this article, we review current research activities in contact material development for electronic and nanoelectronic devices. A fundamental issue in contact materials research is to understand and control interfacial reactions and phenomena
Full Text Available ... the United States. All contact lenses are medical devices that require a prescription and proper fitting by an eye-care professional. Retailers that sell contacts without a ...
Full Text Available ... prescription. Follow the contact lens care directions for cleaning, disinfecting, and wearing the lenses. Never share contact ... with Industry Medical Disclaimer Privacy Policy Terms of Service For Advertisers For Media Ophthalmology Job Center © American ...
Effect of meniscus constact angle during early regimes of spontaneous capillarity in nanochannels
DEFF Research Database (Denmark)
Karna, N.K.; Oyarzua, Elton; Walther, Jens Honore
2016-01-01
4 and 18 nm. We alsofind that the meniscus contact angle remains constant during the inertial regime and its value depends upon the height of the channel. We also find that the meniscus velocity computed at the channel entrance is related to the particular value of themeniscus contact angle....... Moreover, after the inertial regime, the meniscus contactangle is found to be time dependent for all the channels under study. We propose an expression for the time evolution of the dynamic contact angle in nanochannels which, when incorporated in Bosanquets equation, satisfactorily explains the initial...
Variable angle correlation spectroscopy
International Nuclear Information System (INIS)
Lee, Y.K.; Lawrence Berkeley Lab., CA
1994-05-01
In this dissertation, a novel nuclear magnetic resonance (NMR) technique, variable angle correlation spectroscopy (VACSY) is described and demonstrated with 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
... There is a risk of eye infection from bacteria in swimming pool water, hot tubs, lakes and the ocean Replace your contact lens storage case every 3 months or as directed by your eye care professional. Other Risks of Contact Lenses Other risks of contact lenses include pink eye ( ...
Hydrogenation of passivated contacts
Energy Technology Data Exchange (ETDEWEB)
Nemeth, William; Yuan, Hao-Chih; LaSalvia, Vincenzo; Stradins, Pauls; Page, Matthew R.
2018-03-06
Methods of hydrogenation of passivated contacts using materials having hydrogen impurities are provided. An example method includes applying, to a passivated contact, a layer of a material, the material containing hydrogen impurities. The method further includes subsequently annealing the material and subsequently removing the material from the passivated contact.
Mixed Lubricated Line Contacts
Faraon, I.C.
2005-01-01
The present work deals with friction in mixed lubricated line contacts. Components in systems are becoming smaller and due to, for instance power transmitted, partial contact may occur. In industrial applications, friction between the moving contacting surfaces cannot be avoided, therefore it is
New Cosmetic Contact Allergens
Directory of Open Access Journals (Sweden)
An Goossens
2015-02-01
Full Text Available Allergic and photo-allergic contact dermatitis, and immunologic contact urticaria are potential immune-mediated adverse effects from cosmetics. Fragrance components and preservatives are certainly the most frequently observed allergens; however, all ingredients must be considered when investigating for contact allergy.
Dorville, Nicolas; Belmont, Gérard; Aunai, Nicolas; Dargent, Jérémy; Rezeau, Laurence
2015-09-01
, 110702 (2013)], and more recently in a fully kinetic simulation as well [J. Dargent and N. Aunai, Phys. Plasmas (submitted)]. Nevertheless, in most asymmetric layers like the terrestrial magnetopause, one would indeed expect a magnetic field rotation from one direction to another without going through zero [J. Berchem and C. T. Russell, J. Geophys. Res. 87, 8139-8148 (1982)], and a non-zero normal electric field. In this paper, we propose the corresponding generalization: in the model presented, the profiles can be freely imposed for the magnetic field rotation (although restricted to a 180 rotation hitherto) and for the normal electric field. As it was done previously, the equilibrium is tested with a hybrid simulation.
International Nuclear Information System (INIS)
Dorville, Nicolas; Belmont, Gérard; Aunai, Nicolas; Dargent, Jérémy; Rezeau, Laurence
2015-01-01
) 20, 110702 (2013)], and more recently in a fully kinetic simulation as well [J. Dargent and N. Aunai, Phys. Plasmas (submitted)]. Nevertheless, in most asymmetric layers like the terrestrial magnetopause, one would indeed expect a magnetic field rotation from one direction to another without going through zero [J. Berchem and C. T. Russell, J. Geophys. Res. 87, 8139–8148 (1982)], and a non-zero normal electric field. In this paper, we propose the corresponding generalization: in the model presented, the profiles can be freely imposed for the magnetic field rotation (although restricted to a 180 rotation hitherto) and for the normal electric field. As it was done previously, the equilibrium is tested with a hybrid simulation
Dynamics of contact line depinning during droplet evaporation based on thermodynamics.
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.
Energy Technology Data Exchange (ETDEWEB)
Ellingsen, Simen Andreas Aadnoey
2011-01-15
The present thesis focuses on several topics within three separate but related branches of the overall field of dispersion forces. The three branches are: temperature corrections to the Casimir force between real materials (Part 1), explicit calculation of Casimir energy in wedge geometries (Part 2), and Casimir-Polder forces on particles out of thermal equilibrium (Part 3). Part 1 deals primarily with analysis of a previously purported thermodynamic inconsistency in the Casimir-Lifshitz free energy of the interaction of two plane mirrors - violation of the third law of thermodynamics - when the latter's dielectric response is described with dissipative models. It is shown analytically and numerically that the Casimir entropy of the interaction between two metallic mirrors described by the Drude model does tend to zero at zero temperature, provided electronic relaxation does not vanish. The leading order terms at low temperature are found. A similar calculation is carried out for the interaction of semiconductors with small but non-zero DC conductivity. In a generalisation, it is shown that a violation of the third law can only occur for permittivities whose low-frequency behaviour is temperature dependent near zero temperature. A calculation using path integral methods shows that the low temperature behaviour of the interaction of fluctuating Foucault currents in two mirrors of Drude metal is identical to that of the full Casimir-Lifshitz free energy, reasserting a previous finding by Intravaia and Henkel that such fluctuating bulk currents are the physical reason for the anomalous entropy behaviour. In a related effort, an analysis of the frequency dependence of the Casimir force by Ford is generalised to imperfectly reflecting mirrors. A paradox is pointed out, in that the effects of a perturbation of the reflecting properties of the mirrors in a finite frequency window can be calculated in two ways giving different results. It is concluded that optimistic
Presentation of Primary Open Angle Glaucoma (POAG) at Lions ...
African Journals Online (AJOL)
eye hospital in Malawi and serves as the main teaching eye hospital for the ... anterior chamber angle by a Goldmann three-mirror contact lens. IOPs of all the .... Traditional healers play a role in the health care of patients with eye problems.
Lei, Da; Lin, Mian; Li, Yun; Jiang, Wenbin
2018-06-15
An accurate model of the dynamic contact angle θ d is critical for the calculation of capillary force in applications like enhanced oil recovery, where the capillary number Ca ranges from 10 -10 to 10 -5 and the Bond number Bo is less than 10 -4 . The rate-dependence of the dynamic contact angle under such conditions remains blurred, and is the main target of this study. Featuring with pressure control and interface tracking, the innovative experimental system presented in this work achieves the desired ranges of Ca and Bo, and enables the direct optical measurement of dynamic contact angles in capillaries as tiny as 40 × 20 (width × height) μm and 80 × 20 μm. The advancing and receding processes of wetting and nonwetting liquids were tested. The dynamic contact angle was confirmed velocity-independent with 10 -9 contact line velocity V = 0.135-490 μm/s) and it can be described by a two-angle model with desirable accuracy. A modified two-angle model was developed and an empirical form was obtained from experiments. For different liquids contacting the same surface, the advancing angle θ adv approximately equals the static contact angle θ o . The receding angle θ rec was found to be a linear function of θ adv , in good agreement with our and other experiments from the literature. Copyright © 2018 Elsevier Inc. All rights reserved.
Wettability and Contact Time on a Biomimetic Superhydrophobic Surface
Liang, Yunhong; Peng, Jian; Li, Xiujuan; Huang, Jubin; Qiu, Rongxian; Zhang, Zhihui; Ren, Luquan
2017-01-01
Inspired by the array microstructure of natural superhydrophobic surfaces (lotus leaf and cicada wing), an array microstructure was successfully constructed by high speed wire electrical discharge machining (HS-WEDM) on the surfaces of a 7075 aluminum alloy without any chemical treatment. The artificial surfaces had a high apparent contact angle of 153° ± 1° with a contact angle hysteresis less than 5° and showed a good superhydrophobic property. Wettability, contact time, and the corresponding superhydrophobic mechanism of artificial superhydrophobic surface were investigated. The results indicated that the micro-scale array microstructure was an important factor for the superhydrophobic surface, while different array microstructures exhibited different effects on the wettability and contact time of the artificial superhydrophobic surface. The length (L), interval (S), and height (H) of the array microstructure are the main influential factors on the wettability and contact time. The order of importance of these factors is H > S > L for increasing the apparent contact angle and reducing the contact time. The method, using HS-WEDM to fabricate superhydrophobic surface, is simple, low-cost, and environmentally friendly and can easily control the wettability and contact time on the artificial surfaces by changing the array microstructure. PMID:28772613
Directory of Open Access Journals (Sweden)
S. V. LOSKUTOV
2018-05-01
Full Text Available Purpose. To determine the contribution of the real contact spots distribution in the total conductivity of the conductors contact. Methodology. The electrical contact resistance research was carried out on models. The experimental part of this work was done on paper with a graphite layer with membranes (the first type and conductive liquids with discrete partitions (the second type. Findings. It is shown that the contact electrical resistance is mainly determined by the real area of metal contact. The experimental dependence of the electrical resistance of the second type model on the distance between the electrodes and the potential distribution along the sample surface for the first type model were obtained. The theoretical model based on the principle of electric field superposition was considered. The dependences obtained experimentally and calculated by using the theoretical model are in good agreement. Originality. The regularity of the electrical contact resistance formation on a large number of membranes was researched for the first time. A new model of discrete electrical contact based on the liquid as the conducting environment with nuclear membrane partitions was developed. The conclusions of the additivity of contact and bulk electrical resistance were done. Practical value. Based on these researches, a new experimental method of kinetic macroidentation that as a parameter of the metal surface layer deformation uses the real contact area was developed. This method allows to determine the value of average contact stresses, yield point, change of the stress on the depth of deformation depending on the surface treatment.
Contact and symplectic topology
Colin, Vincent; Stipsicz, András
2014-01-01
Symplectic and contact geometry naturally emerged from the mathematical description of classical physics. The discovery of new rigidity phenomena and properties satisfied by these geometric structures launched a new research field worldwide. The intense activity of many European research groups in this field is reflected by the ESF Research Networking Programme "Contact And Symplectic Topology" (CAST). The lectures of the Summer School in Nantes (June 2011) and of the CAST Summer School in Budapest (July 2012) provide a nice panorama of many aspects of the present status of contact and symplectic topology. The notes of the minicourses offer a gentle introduction to topics which have developed in an amazing speed in the recent past. These topics include 3-dimensional and higher dimensional contact topology, Fukaya categories, asymptotically holomorphic methods in contact topology, bordered Floer homology, embedded contact homology, and flexibility results for Stein manifolds.
Introduction to contact mechanics
Fischer-Cripps, Anthony C
2000-01-01
Contact mechanics deals with the elastic or plastic contact between two solid objects, and is thus intimately connected with such topics as fracture, hardness, and elasticity.This text, intended for advanced undergraduates, begins with an introduction to the mechanical properties of materials, general fracture mechanics, and fractures in brittle solids.This is followed by a detailed discussion of stresses and the nature of elastic and elastic-plastic contact.
There is no non-zero stable fixed point for dense networks in the homogeneous Kuramoto model
International Nuclear Information System (INIS)
Taylor, Richard
2012-01-01
This paper is concerned with the existence of multiple stable fixed point solutions of the homogeneous Kuramoto model. We develop a necessary condition for the existence of stable fixed points for the general network Kuramoto model. This condition is applied to show that for sufficiently dense n-node networks, with node degrees at least 0.9395(n−1), the homogeneous (equal frequencies) model has only one stable fixed point solution over the full space of phase angles in the range −π to π. This is the zero fixed point solution defined by all phase angle differences being zero. This result, together with existing research, proves a conjecture of Verwoerd and Mason (2007 Proc. of the American Control Conf. pp 4613–8) that for the complete network and the homogeneous model, the zero fixed point has a basin of attraction consisting of the entire space minus a set of measure zero. The necessary conditions are also tested to see how close to sufficiency they might be by applying them to a class of regular degree networks studied by Wiley et al (2006 Chaos 16 015103). (paper)
Full Text Available ... also available in Spanish . Follow The Academy Professionals: Education Guidelines News Multimedia Public & Patients: Contact Us About the Academy Jobs at the Academy Financial ...
Directory of Open Access Journals (Sweden)
Meltem Önder
2009-03-01
Full Text Available Allergic contact dermatitis is the delayed type hypersensitivity reaction to exogenous agents. Allergic contact dermatitis may clinically present acutely after allergen exposure and initial sensitization in a previously sensitized individual. Acute phase is characterized by erythematous, scaly plaques. In severe cases vesiculation and bullae in exposed areas are very characteristic. Repeated or continuous exposure of sensitized individual with allergen result in chronic dermatitis. Lichenification, erythematous plaques, hyperkeratosis and fissuring may develop in chronic patients. Allergic contact dermatitis is very common dermatologic problem in dermatology daily practice. A diagnosis of contact dermatitis requires the careful consideration of patient history, physical examination and patch testing. The knowledge of the clinical features of the skin reactions to various contactans is important to make a correct diagnosis of contact dermatitis. It can be seen in every age, in children textile product, accessories and touch products are common allergens, while in adults allergic contact dermatitis may be related with topical medicaments. The contact pattern of contact dermatitis depends on fashion and local traditions as well. The localization of allergic reaction should be evaluated and patients’ occupation and hobbies should be asked. The purpose of this review is to introduce to our collaques up dated allergic contact dermatitis literatures both in Turkey and in the World.
Colors and contact dermatitis.
Bonamonte, Domenico; Foti, Caterina; Romita, Paolo; Vestita, Michelangelo; Angelini, Gianni
2014-01-01
The diagnosis of skin diseases relies on several clinical signs, among which color is of paramount importance. In this review, we consider certain clinical presentations of both eczematous and noneczematous contact dermatitis in which color plays a peculiar role orientating toward the right diagnosis. The conditions that will be discussed include specific clinical-morphologic subtypes of eczematous contact dermatitis, primary melanocytic, and nonmelanocytic contact hyperchromia, black dermographism, contact chemical leukoderma, and others. Based on the physical, chemical, and biologic factors underlying a healthy skin color, the various skin shades drawing a disease picture are thoroughly debated, stressing their etiopathogenic origins and histopathologic aspects.
Design of a self-calibration high precision micro-angle deformation optical monitoring scheme
Gu, Yingying; Wang, Li; Guo, Shaogang; Wu, Yun; Liu, Da
2018-03-01
In order to meet the requirement of high precision and micro-angle measurement on orbit, a self-calibrated optical non-contact real-time monitoring device is designed. Within three meters, the micro-angle variable of target relative to measuring basis can be measured in real-time. The range of angle measurement is +/-50'', the angle measurement accuracy is less than 2''. The equipment can realize high precision real-time monitoring the micro-angle deformation, which caused by high strength vibration and shock of rock launching, sun radiation and heat conduction on orbit and so on.
The double Brewster angle effect
Thirion-Lefevre, Laetitia; Guinvarc'h, Régis
2018-01-01
The Double Brewster angle effect (DBE) is an extension of the Brewster angle to double reflection on two orthogonal dielectric surfaces. It results from the combination of two pseudo-Brewster angles occurring in complementary incidence angles domains. It can be observed for a large range of incidence angles provided that double bounces mechanism is present. As a consequence of this effect, we show that the reflection coefficient at VV polarization can be at least 10 dB lower than the reflection coefficient at HH polarization over a wide range of incidence angle - typically from 20 to 70∘. It is experimentally demonstrated using a Synthetic Aperture Radar (SAR) image that this effect can be seen on buildings and forests. For large buildings, the difference can reach more than 20 dB. xml:lang="fr"
Angle Performance on Optima XE
International Nuclear Information System (INIS)
David, Jonathan; Satoh, Shu
2011-01-01
Angle control on high energy implanters is important due to shrinking device dimensions, and sensitivity to channeling at high beam energies. On Optima XE, beam-to-wafer angles are controlled in both the horizontal and vertical directions. In the horizontal direction, the beam angle is measured through a series of narrow slits, and any angle adjustment is made by steering the beam with the corrector magnet. In the vertical direction, the beam angle is measured through a high aspect ratio mask, and any angle adjustment is made by slightly tilting the wafer platen during implant.Using a sensitive channeling condition, we were able to quantify the angle repeatability of Optima XE. By quantifying the sheet resistance sensitivity to both horizontal and vertical angle variation, the total angle variation was calculated as 0.04 deg. (1σ). Implants were run over a five week period, with all of the wafers selected from a single boule, in order to control for any crystal cut variation.
Small angle neutron scattering
Directory of Open Access Journals (Sweden)
Cousin Fabrice
2015-01-01
Full Text Available 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
Non-zero θ{sub 13} and leptonic CP phase with A{sub 4} symmetry
Energy Technology Data Exchange (ETDEWEB)
Sruthilaya, M.; Mohanta, R. [University of Hyderabad, School of Physics, Hyderabad (India)
2017-03-15
We consider a model based on A{sub 4} symmetry to explain the phenomenon of neutrino mixing. The spontaneous symmetry breaking of A{sub 4} symmetry leads to a co-bimaximal mixing matrix at leading order. We consider the effect of higher order corrections in neutrino sector and find that the mixing angles thus obtained, come well within the 3σ ranges of their experimental values. We study the implications of this formalism on the other phenomenological observables, such as CP violating phase, Jarlskog invariant and the effective Majorana mass vertical stroke M{sub ee} vertical stroke. We also obtain the branching ratio of the lepton flavour violating decay μ → eγ in the context of this model and find that it can be less than its present experimental upper bound. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Stasyuk, I.V.; Krasnov, V.O., E-mail: krasnoff@icmp.lviv.ua
2017-04-15
Phase transitions at non-zero temperatures in ultracold Bose- and Fermi-particles mixture in optical lattices using the Bose-Fermi-Hubbard model in the mean field and hard-core boson approximations are investigated. The case of infinitely small fermion transfer and the repulsive on-site boson-fermion interaction is considered. The possibility of change of order (from the 2nd to the 1st one) of the phase transition to the superfluid phase in the regime of fixed values of the chemical potentials of Bose- and Fermi-particles is established. The relevant phase diagrams determining the conditions at which such a change takes place, are built.
Yang, Liang; Alouini, Mohamed-Slim; Ansari, Imran Shafique
2018-01-01
In this correspondence, an asymptotic performance analysis for two-way relaying free-space optical (FSO) communication systems with nonzero boresight pointing errors over double-generalized gamma fading channels is presented. Assuming amplify-and-forward (AF) relaying, two nodes having the FSO ability can communicate with each other through the optical links. With this setup, an approximate cumulative distribution function (CDF) expression for the overall signal-to-noise ratio (SNR) is presented. With this statistic distribution, we derive the asymptotic analytical results for the outage probability and average bit error rate. Furthermore, we provide the asymptotic average capacity analysis for high SNR by using the momentsbased method.
Yang, Liang
2018-05-07
In this correspondence, an asymptotic performance analysis for two-way relaying free-space optical (FSO) communication systems with nonzero boresight pointing errors over double-generalized gamma fading channels is presented. Assuming amplify-and-forward (AF) relaying, two nodes having the FSO ability can communicate with each other through the optical links. With this setup, an approximate cumulative distribution function (CDF) expression for the overall signal-to-noise ratio (SNR) is presented. With this statistic distribution, we derive the asymptotic analytical results for the outage probability and average bit error rate. Furthermore, we provide the asymptotic average capacity analysis for high SNR by using the momentsbased method.
Full Text Available ... eye-care professional. Retailers that sell contacts without a prescription are breaking the law, and may be fined $11,000 per violation. "Many of the lenses found online or in beauty salons, novelty shops or in pop-up ... contact lenses from a retailer that does not ask for a prescription. ...
International Nuclear Information System (INIS)
Cuthrell, R.E.
1976-01-01
Electrical contacts must function properly in many types of components used in nuclear weapon systems. Design, application, and testing of these components require detailed knowledge of chemical and physical phenomena associated with stockpile storage, stockpile testing, and operation. In the past, investigation of these phenomena has led to significant discoveries on the effects of surface contaminants, friction and wear, and the mechanics of closure on contact performance. A recent investigation of contact arcing phenomena which revealed that, preceding contact closure, arcs may occur at voltages lower than had been previously known is described. This discovery is important, since arcing may damage contacts, and repetitive testing of contacts performed as part of a quality assurance program might produce cumulative damage that would yield misleading life-test data and could prevent proper operation of the contacts at some time in the future. This damage can be avoided by determining the conditions under which arcing occurs, and ensuring that these conditions are avoided in contact testing
Full Text Available ... Get follow up exams with your eye care provider. If you notice redness, swelling, excessive discharge, pain or discomfort from wearing contact lenses, remove the lenses and seek immediate medical attention from an ophthalmologist. Related resources: Learn how to properly care for contact lenses . ...
African Journals Online (AJOL)
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Full Text Available ... eye-care team . Consumer warning about the improper use of colored contact lenses , from the U.S. Food and Drug Administration (FDA). Are the colored lenses you are considering buying approved by the FDA? Check the FDA's database of approved contact lenses . Related Stories Prevent Infection ...
DEFF Research Database (Denmark)
Andersen, Klaus Ejner; Benezra, C; Burrows, D
1987-01-01
In recent years, there has been a dramatic rise in our understanding of contact dermatitis. This paper is a review of our knowledge of the mechanisms involved in contact dermatitis and related phenomena, the investigation of these events and the emergence of significant new allergens during...
Energy Technology Data Exchange (ETDEWEB)
Bravetti, Alessandro, E-mail: alessandro.bravetti@iimas.unam.mx [Instituto de Investigaciones en Matemáticas Aplicadas y en Sistemas, Universidad Nacional Autónoma de México, A. P. 70543, México, DF 04510 (Mexico); Cruz, Hans, E-mail: hans@ciencias.unam.mx [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, A. P. 70543, México, DF 04510 (Mexico); Tapias, Diego, E-mail: diego.tapias@nucleares.unam.mx [Facultad de Ciencias, Universidad Nacional Autónoma de México, A.P. 70543, México, DF 04510 (Mexico)
2017-01-15
In this work we introduce contact Hamiltonian mechanics, an extension of symplectic Hamiltonian mechanics, and show that it is a natural candidate for a geometric description of non-dissipative and dissipative systems. For this purpose we review in detail the major features of standard symplectic Hamiltonian dynamics and show that all of them can be generalized to the contact case.
Contact Quality in Participation
DEFF Research Database (Denmark)
Simonsen, Jesper; Jensen, Olav Storm
2016-01-01
We investigate the concept of participation from the perspective of quality of the contact in the communicative interactions between participants. We argue for the need for an academic-personal competence that qualifies the human contact central in all Participatory Design (PD) activities as a way...
Nigerian Food Journal: Contact
African Journals Online (AJOL)
Nigerian Food Journal. ... Nigerian Food Journal: Contact. Journal Home > About the Journal > Nigerian Food Journal: Contact. Log in or Register to get access to full text downloads. ... Mailing Address. Department of Food Science and Technology University of Agriculture, Makurdi, Nigeria ...
Full Text Available ... like a suction cup." Halloween is a popular time for people to use colored contact lenses to enhance their costumes. From ... MD, professor of ophthalmology at Case Western Reserve University in Cleveland. "This is far ... Use Facts About Colored Contacts and Halloween Safety Colored ...
Automated analysis of angle closure from anterior chamber angle images.
Baskaran, Mani; Cheng, Jun; Perera, Shamira A; Tun, Tin A; Liu, Jiang; Aung, Tin
2014-10-21
To evaluate a novel software capable of automatically grading angle closure on EyeCam angle images in comparison with manual grading of images, with gonioscopy as the reference standard. In this hospital-based, prospective study, subjects underwent gonioscopy by a single observer, and EyeCam imaging by a different operator. The anterior chamber angle in a quadrant was classified as closed if the posterior trabecular meshwork could not be seen. An eye was classified as having angle closure if there were two or more quadrants of closure. Automated grading of the angle images was performed using customized software. Agreement between the methods was ascertained by κ statistic and comparison of area under receiver operating characteristic curves (AUC). One hundred forty subjects (140 eyes) were included, most of whom were Chinese (102/140, 72.9%) and women (72/140, 51.5%). Angle closure was detected in 61 eyes (43.6%) with gonioscopy in comparison with 59 eyes (42.1%, P = 0.73) using manual grading, and 67 eyes (47.9%, P = 0.24) with automated grading of EyeCam images. The agreement for angle closure diagnosis between gonioscopy and both manual (κ = 0.88; 95% confidence interval [CI), 0.81-0.96) and automated grading of EyeCam images was good (κ = 0.74; 95% CI, 0.63-0.85). The AUC for detecting eyes with gonioscopic angle closure was comparable for manual and automated grading (AUC 0.974 vs. 0.954, P = 0.31) of EyeCam images. Customized software for automated grading of EyeCam angle images was found to have good agreement with gonioscopy. Human observation of the EyeCam images may still be needed to avoid gross misclassification, especially in eyes with extensive angle closure. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.
Contact materials for nanoelectronics
Alshareef, Husam N.
2011-02-01
In this article, we review current research activities in contact material development for electronic and nanoelectronic devices. A fundamental issue in contact materials research is to understand and control interfacial reactions and phenomena that modify the expected device performance. These reactions have become more challenging and more difficult to control as new materials have been introduced and as device sizes have entered the deep nanoscale. To provide an overview of this field of inquiry, this issue of MRS Bulletin includes articles on gate and contact materials for Si-based devices, junction contact materials for Si-based devices, and contact materials for alternate channel substrates (Ge and III-V), nanodevices. © 2011 Materials Research Society.
Noneczematous Contact Dermatitis
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
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
Measurement of the angle gamma
International Nuclear Information System (INIS)
Aleksan, R.; Sphicas, P.; Massachusetts Inst. of Tech., Cambridge, MA
1993-12-01
The angle γ as defined in the Wolfenstein approximation is not completely out of reach of current or proposed dedicated B experiments. This work represents but a first step in the direction of extracting the third angle of the unitarity triangle by study the feasibility of using new decay modes in a hadronic machine. (A.B.). 11 refs., 1 fig., 7 tabs
Nucleation of small angle boundaries
CSIR Research Space (South Africa)
Nabarro, FRN
1996-12-01
Full Text Available The internal stresses induced by the strain gradients in an array of lattice cells delineated by low-angle dislocation boundaries are partially relieved by the creation of new low-angle boundaries. This is shown to be a first-order transition...
International Nuclear Information System (INIS)
Tove, P.A.
1975-08-01
Contacts to semiconductors play an important role in most semiconductor devices. These devices range from microelectronics to power components, from high-sensitivity light or radiation detectors to light-emitting of microwave-generating components. Silicon is the dominating material but compound semiconductors are increasing in importance. The following survey is an attempt to classify contact properties and the physical mechanisms involved, as well as fabrication methods and methods of investigation. The main interest is in metal-semiconductor type contacts where a few basic concepts are dealt with in some detail. (Auth.)
Bhabha vs. Moeller scattering as a contact-interaction analyzer at a polarized linear collider
Pankov, A A
2002-01-01
We discuss electron-electron contact-interaction searches in the processes e sup + e sup -->e sup + e sup - and e sup - e sup -->e sup - e sup - at planned Linear Colliders run in the e sup + e sup - and e sup - e sup - modes with both beams longitudinally polarized. Our analysis is based on the measurement, for the two processes, of polarized differential cross sections, and allows to simultaneously take into account the general set of electron contact interaction couplings as independent, non-zero, parameters thus avoiding the simplifying choice of a model. We evaluate the corresponding model-independent constraints on the contact coupling constants, emphasizing the role of the available beam polarization and the complementarity, as far as the chirality of the constants is concerned, of the two processes in giving the best constraints. We also make a comparison with the potential of e sup + e sup --> mu supmu sup - at the same energy and initial beams polarization.
Bhabha vs. Moeller scattering as a contact-interaction analyzer at a polarized linear collider
International Nuclear Information System (INIS)
Pankov, A.; Paver, N.
2002-10-01
We discuss electron-electron contact-interaction searches in the processes e + e - →e + e - and e - e - →e - e - at planned Linear Colliders run in the e + e - and e - e - modes with both beams longitudinally polarized. Our analysis is based on the measurement, for the two processes, of polarized differential cross sections, and allows to simultaneously take into account the general set of electron contact interaction couplings as independent, non-zero, parameters thus avoiding the simplifying choice of a model. We evaluate the corresponding model-independent constraints on the contact coupling constants, emphasizing the role of the available beam polarization and the complementarity, as far as the chirality of the constants is concerned, of the two processes in giving the best constraints. We also make a comparison with the potential of e + e - →μ μ- at the same energy and initial beams polarization. (author)
Relationship between the Angle of Repose and Angle of Internal ...
African Journals Online (AJOL)
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DEFF Research Database (Denmark)
Alberti, Mark; la Cour, Morten
2018-01-01
PURPOSE: To compare gas-foveal contact in face-down positioning (FDP) and nonsupine positioning (NSP), to analyze causes of gas-foveal separation and to determine how gas-foveal contact affects clinical outcome after idiopathic macular hole repair. METHODS: Single center, randomized controlled...... study. Participants with an idiopathic macular hole were allocated to either FDP or NSP. Primary outcome was gas-foveal contact, calculated by analyzing positioning in relation to intraocular gas fill. Positioning was measured with an electronic device recording positioning for 72 hours postoperatively....... RESULTS: Positioning data were available for 33/35 in the FDP group and 35/37 in the NSP group, thus results are based on 68 analyzed participants. Median gas-foveal contact was 99.82% (range 73.6-100.0) in the FDP group and 99.57% (range 85.3-100.0) in the NSP group (P = 0.22). In a statistical model...
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