Effect Of Meniscus Research Articles

Effect of patellar meniscus on patellofemoral contact stress in total knee arthroplasty

The effect of a meniscus of fibrous tissue (patellar meniscus), on patellofemoral contact area and stresses was evaluated. Two knees with total knee arthroplasty and dome-shaped patellar components were retrieved at autopsy. Both had substantial fibrous menisci surrounding the dome of the patellar component. Contact area and contact stresses were measured with a digital electronic sensor, first with the patellar meniscus intact, then again after the patellar meniscus was removed. No dramatic difference was detected in patellofemoral contact area and contact stresses between the patellas with an intact or removed patellar meniscus, and there was no detectable load under the patellar meniscus. The results of this case study suggest that fibrous tissue surrounding the dome-shaped patellar component does not share compressive loads with the patellar component.

Contact of Two Carbon Surfaces Covered with a Dispersant Polymer

Using a surface force apparatus (SFA), we have studied, first the adhesive force between two smooth amorphous carbon surfaces in air, and second, the repulsive force due to the contact of two brush polymer layers adsorbed on carbon surfaces. Adhesion in dry air is compared to that due to the effect of a small meniscus formed in humid air and the partial wetting of a large water meniscus. Dispersive and acid-base contributions of carbon surfaces are also determined, using Fowkes analysis. The adsorption of a polyisobutenesuccinimide (PIB) in dilute solution with hydrocarbon solvent at 25 °C, and the resulting interactions between carbon surfaces are also characterised with the SFA. Our results show that this dispersant polymer on a carbon surface forms a 5.5 nm thick anisotropic brush layer. This anisotropy is detected mechanically and compared with that of other polymer or surfactant. The ability of PIB molecules to adsorb on carbon particles and thus stabilize them in the hydrocarbon solution, is of great implication in lubrication technology. The results clarify that this additive function by steric stabilization mechanism and not by electrostatic repulsion The results provide a basis for understanding the mechanism of action of of polyisobutenesuccinimides widely used as dispersant additives in lubricants.

Nonlinear dynamics of intermittent-contact mode atomic force microscopy

In intermittent-contact mode atomic force microscopy (AFM), the AFM tip and the harmonically driven sample only spend a brief time in contact, compared to the driving period. As a result the dynamical response of the cantilever to the shocks received on impact can be described and analyzed in terms of an instantaneous impact law specifying the loss of kinetic energy on impact. The simplest such law assumes a constant coefficient of restitution and results in the impact oscillator model. The coefficient-of-restitution law is modified to include an absolute loss of energy on impact, modeling the effects of adhesion. The stability of single-impact orbits for this impact law is analyzed. The analytical results based on these models are found to be in agreement with experiment. A model of the tip-sample interaction based on the Johnson-Kendall-Roberts model of contact incorporating the effects of a liquid meniscus between the tip and the sample is presented. The resulting impact law is found to follow the modified impact law in the presence of adhesion.

Equilibrium shape of an anisotropic crystal confined between two planar parallel walls

Experimentally, the surface-free-energy anisotropy of a crystal-liquid interface is usually inferred from the surface-shape anisotropy of a solid germ at equilibrium with the melt. However, the crystal is usually not free. For example, in thin samples, the crystal touches the two limiting glass plates:mHere, we analyze theoretically how the shape anisotropy of the crystal depends on the wetting conditions in this particular geometry. We calculate the equilibrium shape of an anisotropic crystal (of uniaxial, cubic, or hexagonal symmetry) confined between two planar parallel walls as a function of its size and of the wetting conditions on the walls. We find an analytic solution for the shape of the meniscus in the sample thickness and its anisotropy in the midplane parallel to the walls in the limit of very large radius and vanishing surface tension anisotropy. In other cases, a numerical solution is given. Neglecting the meniscus effect leads to errors as large as 25% for the inferred anisotropy.

Effects of meniscus on the directional growth of potassium niobate single crystals

The study of meniscus effects on the directional growth of single crystals of potassium niobate (KNbO 3) with a [110] pc oriented seed by the top-seeded-solution-growth technique has been described. The directional growth of KNbO 3 single crystals has been illustrated for different crystallographic orientations of the crystal. Experimental results show that the shape of the solution flux meniscus, which is determined by a number of growth parameters, has a significant effect on growth rates on different 100 pc, 010 pc and 001 pc type surfaces. Findings based on this work enable one to select a dominant growth direction and hence to engineer the geometrical shaping of resultant KNbO 3 single crystals through careful control of growth parameters. Maximum crystal dimensions for the grown KNbO 3 along [100] pc and [001] pc achieved in this work are 34.0 and 31.2 mm, respectively.

Factors affecting the dissolution and reduction of oxygen in molten carbonate electrolytes. Part II: Effect of SrCO 3, BaCO 3 and SnO 2 additives

The effect of minority SrCO 3, BaCO 3, and SnO 2 additions to various alkali carbonate electrolytes has been investigated for both oxygen reduction kinetics and also oxide ion activity. Although alkaline earth metal additives were found to assimilate into the melt with relative ease, metal oxides of higher valency were found to be fairly insoluble. In general, addition of earth metal carbonates to the electrolyte provides a means of increasing the effective oxygen solubility. The nature of the improvement appears to vary with the additive used, the amount added, and the original electrolyte composition. In all cases there was a significant increase in background current. In view of surface energy considerations, this is most probably due to increased carbon dioxide diffusion and meniscus effects. In addition to the increase in oxygen dissolution, there appears to be a concurrent increase in the oxide ion activity.

Optical interferometric studies of a confined liquid free surface: meniscus‐effect compensation and time evolution of the surface

A fruitful approach to the studies of a liquid free surface is demonstrated. Using optical interferential techniques, the free surface of nonvolatile and volatile confined liquids is analyzed. Various wall container types are investigated. Besides the classical plane wall, experiments are performed by using cylindrical and toroidal walls. In these last cases, the meniscus effect that affects the free surface of the liquid is compensated. Then, it is possible to obtain completely flat free surfaces of liquids up to 80% of their total. Interferometric experiments are also described to measure the inclination of the site with respect to the local horizon, represented by the liquid flat free surface, and to follow the temporal evolution of such free surfaces affected by different conditions.

A heterogeneous model for the MCFC cathode

A steady state agglomerate model for the MCFC cathode which takes into account the heterogeneous structure of this porous electrode is presented. The resulting model equations are solved by means of the finite element method. Calculations have been performed on two different test structures and include the influence of kinetics, porosity, outer surface area and distribution of electrolyte film. Comparisons with the filmed agglomerate model show that it is possible to obtain excellent agreement between the polarisation curves predicted by the two different models if a uniform film is used in the simulations. The tortuosity in the filmed agglomerate model is used as a fitting parameter. Other effects that evolve in the heterogeneous model due to variations in the local structure are not revealed in the pseudohomogeneous model. The effect of a non-uniform electrolyte film thickness was investigated by solving the problem for a structure with pore mouths filled by an electrolyte meniscus. Also the effect of an electrolyte meniscus between spherical agglomerates was investigated.

The Effect of the Disjoining Pressure on the Surface Evaporation of a Porous Medium

ABSTRACT The behavior of surface evaporation of a porous medium is investigated experimentally. A theoretical analysis is used to describe the experimental results in this work. Quartz sand(10–20 mesh) is packed as the porous medium. Pure water with electric resistance greater than 10 MΩ and aqueous solution with various concentration of sodium sulfate are used as working liquid in the experiments. Electric light radiation is used as the heat source. Free convection is used in the experiments. The results of the experiment show that the concentration of the salt has great influence on the rate of surface evaporation. A model of microlayer evaporation is developed to predict the drop of evaporation rate. The agreement of experimental results and theoretical results show that the evaporation of the microlayer, driven by the gradient of the disjoining pressure, as well as the interface of the liquid surface curvature due to meniscus effects is important.

The degradation of coupled stones by wet deposition processes

An investigation has been made of the influence of wet deposition of simulated acid rain, with subsequent dry/wet cycling, on the degradation of limestone, sandstone, marble and granite, interactively coupled by overlapping or butt joints to simulate architectural detail, and sloping at an angle so that run-off from the upper stone drains on to the lower one. Degradation was monitored by pH change and analysis of run-off solution and soluble extracts from the exposed stones, together with EPMA, SEM/EDX and X-ray diffraction examination of petrographic sections. Overlapping coupled stones show greater degradation of the lower stone for all stones, but particularly when it is granite and the upper stone is limestone. This is partly due to a longer time of wetness at the interface and closely adjacent areas (meniscus effect), and partly due to the deposition of ions from the upper stone and the buildup of damaging degradation products (mainly gypsum) on the lower stone and interaction with it. Butt-jointed couples scarcely show the effect due to no significant meniscus effect. This method of laboratory simulation for stones shaped and interactively coupled to reproduce protruding and re-entrant surfaces in typical architectural combinations, so that drainage from one to another occurs, can yield results similar to those found in practice, and be used to rank various stone combinations.

Capillary–viscous forcing of surface waves

The linear excitation of straight-crested, capillary–gravity waves on the surface ( x > 0) of a deep, viscous liquid in response to the sinusoidal, vertical motion of a hydrophilic wall at x = 0 is calculated on the assumptions that: (i) the dynamical variation of the contact angle is proportional to (but not necessarily in phase with) the velocity of the contact line relative to the wall; (ii) the relative tangential velocity (slip) of the fluid below the contact line is proportional to the shear at the wall, (iii) k 0 l v [Lt ] 1 and k 0 l c = O (1), where k 0 is the wavenumber, l v is the boundary-layer thickness, and l c is the capillary length. The contact-angle and slip coefficients are complex functions of frequency that are found to be linearly related. Physical considerations suggest that the slip length l s (≡ slip velocity ÷ shear at wall) should be small compared with l v , which, in turn, implies that the motion of the contact line must be small in that parametric domain in which linearization provides a viable description of the wave motion near the wall; however, the analysis proceeds from (i) and (ii), qua phenomenological hypotheses, without a priori restrictions on the contact-line and slip coefficients. The present results include those of Wilson & Jones (1973), who assume that the amplitude and phase of the wave slope at the wall are prescribed, and those of Hocking (1987 a ), who assumes that the variation of the wave slope at the wall is in phase with the contact-line velocity and neglects viscosity. They also include a correction for the dynamical effects of the static meniscus, which is necessarily present for any static contact angle other than ½π but is neglected in the previous analyses, and have counterparts for the closely related problem (cf. Hocking 1987 b ) of the reflection of a plane wave from a stationary wall.

Immobilized pH gradients in ultrathin‐layer (100 μm) gels: Avoiding capillarity by a ‘squeezing‐sealing mold’ technique

Several procedures for casting 100 microns ultrathin immobilized pH gradients are described. When acrylate/glass molding cassettes (Pascali et al., Electrophoresis 1987, 8, 371-373) are used two main problems are encountered: (i) a tendency of polymerization solutions, at the beginning of delivery, to spread across the glass surfaces with troublesome effects on the gradient stratification, and (ii) the raising of steep menisci at both extremities of the pH intervals, originating from capillarity phenomena and resulting in nonuniform gradients with bowed electrophoretic patterns. The first shortcoming was acceptably solved by increasing the density of sucrose gradients, and pouring them into prewarmed molding cassettes. The detrimental effect of menisci could be overcome by using a 'squeezing-sealing mold' technique. A molding cassette was endowed with a continuous, squared spacer frame, the upper side being open by inserting a wedged clip. A slight excess of polymerization solution was first dispensed into the cassette and squeezed away on removal of the clip. By completely excluding air from the molding cassette, uniform and well reproducible ultrathin gels could be cast. A major advantage of ultrathin immobilized pH gradient gels is the drastically shorter focusing time.

Experiments on natural convection in complex enclosed spaces containing either two fluids or a single fluid

Heat transfer coefficients were determined experimentally for natural convection in the enclosed space between two concentrically positioned vertical cylinders having different finite heights. The space was filled with a pair of fluid layers, one atop the other. The investigated two-fluid systems included air and water, air and hexadecane, and hexadecane and water. Experiments were also performed for the case in which the intercylinder space was filled with a single fluid—air, water, or hexadecane. Parametric variations were carried out for the height of the fluid-fluid interface and for the Rayleigh number. Comparisons were made between the experimental results and predictions obtained from numerical solutions of the problem. Very good agreement prevailed for the single-fluid cases and also for the two-fluid cases where meniscus and interfacial tension effects were either negligible or small. When these effects were more significant, as for the hexadecane-water system (the only liquid-liquid system investigated), it was found possible to achieve satisfactory agreement by making use of a relatively simple interface model. For the single-fluid results, the effect of the Prandtl number variation (between 0.71 and 40) was highlighted.

Meniscus effects and fracture in Portland cement paste

Resultats d'essais de mecanique de la rupture realises sur une pâte de ciment et du verre poreux afin d'elucider le role de l'effet de menisque dans le processus de rupture

Effect of humidity and porosity on fracture of hardened portland cement

The dependence of fracture mechanics terms ( γ T, K c, G c and J c) on relative humidity and porosity is determined for hardened portland cement paste (HCP). The cardinal features of the fracture term/humidity curves and fracture term/porosity curves are discussed. Large hysteresis in fracture term/relative humidity curves is observed, the magnitude depending on the drying history of HCP. Meniscus effects, aging and moisture-assisted stress corrosion processes are thought to contribute to fracture of HCP. Unhydrated portland cement, Ca(OH) 2 particles, and pores with specific size distributions in the HCP system possibly act as crack arrestors.

On the spectra of high-frequency wind waves

Displacements of wind waves in the laboratory were measured with a laser displacement gauge, a recent,ly developed, optical, non-intrusive sensor, which avoids the meniscus effect's that severely limit the frequency response of conventional thin- wire gauges. The new gauge is a digital device, which has a maximum frequency response of 2.5 kHz. Its spatial resolution, which depends on the field of view, is t,ypically 0.016 cm for a 4 cm field of view. The wind-wave displacements were measured at several fetches for three wind speeds. Wave-variance spectra derived from these measurements indicate the presence of a quasi-equilibrium spectrum in the capillary-wave regime. The quasi-equilibrium spectrum follows an $f^{-\frac{7}{3}}$ power law that has been predicted on dimensional grounds. The spect'ral density increases with increasing wind speed from 4 to 10 m/s but is independent of the fetch from 3 to 5 m. In addition, the capillary-wave spectrum is practically unchanged when a, relatively long but. low-amplitude mechanical wave is superposed onto the wind- generat'cd waves.

Durability of cement and glass impregnated with sulfur and polymethyl methacrylate

Possible causes of instability of sulfur-impregnated bodies (porous glass and portland cement) have been investigated. As they are non-crystalline and have a large surface-to-volume ratio, impregnants in small pores are normally in a metastable state unless their free energy is lowered by meniscus effects or interaction with the matrix. Extrusion of sulfur on exposure to water or other adsorbing vapors occurs because of the weak interaction between impregnant and the siliceous surface and a lubricating effect created by the presence of the adsorbate on the surface of the impregnant. Non-isotropic expansion and impregnant-adsorbate interaction are suggested as the main causes of mechanical breakdown. Good interaction with the surface and resistance to flow due to cross-linking render polymethyl methacrylate a stable impregnant.

Viscosity Measurements on NaCl in the Temperature Range 1083 — 1473 K

AbstractThe viscosity of NaCl has been measured with an oscillating‐cup viscometer in the temperature range from 1083 K to 1473 K along the saturation line. The measured viscosity was lower than a currently recommended value by nearly 40%, whereas it was in accordance with other recent experimental results. To evaluate a meniscus effect of the liquid inside the cup on the viscosity, an experimental assessment was made. The results showed no appreciable viscosity change caused by changing the height of the liquid surface. The Stokes‐Einstein equation was further examined for NaCl using the present results. While an excellent agreement between the calculated self‐diffusion coefficient and that of experiment was observed for the cation, the calculated value was systematically lower than the experimental one for the anion.

回転振動法による液体金属の粘度算出式に関する実験的検討

In order to determine the viscosity of liquid by the oscillating vessel method with high accuracy, an investigation was made on the relationship between the logarithmic decrement of the oscillations of a suspended system and the viscosity of liquid.First, improvements were made on the viscosity apparatus such as the balance weight in order to obtain the precise values of measurement on the logarithmic decrement.In the equation proposed by Roscoe, which has frequently been used to calculate the absolute and accurate viscosity of liquid from the measured logarithmic decrement, corrections for the end, slipping and meniscus effects are not sufficiently discussed. Therefore, Roscoe’s formula was examined by experiment using the viscometer calibrating liquids such as Hg, In, Sn, Bi and Pb whose viscosities had been measured by a theoretically established capillary method. The results showed that Roscoe’s equation did not necessarily provide reliable viscosity values. A correction for Roscoe’s equation was made so as to derive reasonable values of viscosity. The corrected Roscoe’s formula appears to give precise values of viscosity of liquid.Based on the above investigation, the logarithmic decrement of liquid zinc was measured precisely in the temperature range from 700 to 913 K by the oscillating vessel method, and its viscosity was determined by the corrected Roscoe’s formula that connects the logarithmic decrement with the viscosity of liquid.The variation of the viscosity η (in Pa·s) with absolute temperature T is expressed by the following relationship:(This article is not displayable. Please see full text pdf.) The value of the melting-point viscosity of 3.50×10−3 Pa·s for liquid zinc was obtained from the above equation.The viscosity data of zinc determined in this work are thought to be accurate within the absolute error of about ±4%.

Multi-channel, probe colorimeter for use with the micr-ELISA test, which makes use of disposable flat-bottom microhemagglutination plates.

We describe a multiprobe colorimeter that permits the reading of enzyme-linked immunosorbent assays (ELISA) in situ, by use of microhemagglutination plates. The use of dipping probes eliminates interference from meniscus effects and air-bubble entrapment. Detailed validation tests have been done and potential sources of inaccuracy identified.