Detachment angle

Anticholinesterase agents are potent drugs with many potential adverse effects iris cysts and anterior subcapsu-lar lens cataracts are the most serious and well known. Other significant but less common ocular manifestations include retinal detachment, angle-closure glaucoma, and uveitis. Common but less serious adverse effects include... 

Figure 21. Model of dislocation string detachment from point defect. Pinning in A and B points supposed rigid /i, /j are lengths of vibrating dislocation segments. Arrow shows direction of dislocation slipping and outer stress (p is critical detachment angle.

Notice that, unlike what one might have guessed from Eq. (18), the potential (and thus the force) is not proportional to the product of the two detachment angles. The actual form of the prefactor, + of, is highly suggestive of an entirely... 

The various linear calculations show that two axisymmetric colloids on a membrane should repel. But, as the detachment angles a,- increase, it becomes harder to justify the linearization. The expansion in Eq. (3) ultimately rests on the smallness of IV/il, an expression that should be compared to tan a,. But, once higher order terms matter, Monge parametrization not only becomes technically impenetrable, it is even incapable of dealing with membrane shapes that display overhangs. It is hence preferable to discard it in favor of a more general numerical surface triangulation. 

The experiments by Koltover et al. claim that isotropic colloids on membranes experience a surface-mediated (presumably, curvature-mediated) attraction. All theories we have discussed so far claim that the force is repulsive, unless one goes to large detachment angles. Can simulaticMis shed more light onto the problem If so, it will not be necessary to represent the bilayer in any greater detail because only fluid curvature elasticity needs to be captured. 

In general, a shear force of at least double the adhesive force is required for the adhesive force to be maintained, and measurements from isolated setae of 200 )U.N of shear force and 40 /U-N of adhesive force suggest that that this factor may often be exceeded. This frictional adhesion model also helps to explain how detachment of the setae occurs. The relationship between the two forces is consistent with a critical detachment angle of 30° (see below). At shear forces less than twice the adhesive force, and an angle of greater than 30°, adhesive forces will no longer be able to be maintained and setae will detach from the surface with no measurable detachment forces. The model, therefore, is defined as ... 

A vacuum force is built up in the vicinity of the detachment line which is dependent on the detachment angle as well as on the machine speed. 

A zero or near-zero contact angle is necessary otherwise results will be low. This was found to be the case with surfactant solutions where adsorption on the ring changed its wetting characteristics, and where liquid-liquid interfacial tensions were measured. In such cases a Teflon or polyethylene ring may be used [47]. When used to study monolayers, it may be necessary to know the increase in area at detachment, and some calculations of this are available [48]. Finally, an alternative method obtains y from the slope of the plot of W versus z, the elevation of the ring above the liquid surface [49]. 

The basic observation is that a thin plate, such as a microscope cover glass or piece of platinum foil, will support a meniscus whose weight both as measured statically or by detachment is given very accurately by the ideal equation (assuming zero contact angle) ... 

The basic phenomenon involved is that particles of ore are carried upward and held in the froth by virtue of their being attached to an air bubble, as illustrated in the inset to Fig. XIII-4. Consider, for example, the gravity-free situation indicated in Fig. XIII-5 for the case of a spherical particle. The particle may be entirely in phase A or entirely in phase B. Alternatively, it may be located in the interface, in which case both 7sa nnd 7sb contribute to the total surface free energy of the system. Also, however, some liquid-liquid interface has been eliminated. It may be shown (see Problem XIII-12) that if there is a finite contact angle, 0sab> the stable position of the particle is at the interface, as shown in Fig. XIII-5Z>. Actual measured detachment forces are in the range of 5 to 20 dyn [60]. 

The cleaning process proceeds by one of three primary mechanisms solubilization, emulsification, and roll-up [229]. In solubilization the oily phase partitions into surfactant micelles that desorb from the solid surface and diffuse into the bulk. As mentioned above, there is a body of theoretical work on solubilization [146, 147] and numerous experimental studies by a variety of spectroscopic techniques [143-145,230]. Emulsification involves the formation and removal of an emulsion at the oil-water interface the removal step may involve hydrodynamic as well as surface chemical forces. Emulsion formation is covered in Chapter XIV. In roll-up the surfactant reduces the contact angle of the liquid soil or the surface free energy of a solid particle aiding its detachment and subsequent removal by hydrodynamic forces. Adam and Stevenson s beautiful photographs illustrate roll-up of lanoline on wood fibers [231]. In order to achieve roll-up, one requires the surface free energies for soil detachment illustrated in Fig. XIII-14 to obey... 

This test measures the ability of a tape to resist creep under applied load. The test is covered in ASTM D-3654 and PSTC-7. A specified area (typically 12.7 mmx 12.7 mm) of conditioned tape is rolled down with a specified pressure on the substrate of choice, such as polished 302 stainless steel. The panel is fixed in the vertical position or up to 2° tilted back so that there is no element of low angle peel in the test (Fig. lb). A weight (often 1000 g) is fixed to the end of the tape and the time to failure, i.e. complete detachment from the plate, is measured. Infrequently, the time required for the tape to creep a given distance is measured and reported. 

For our initial geometry for the transition structure, we ll detach one hydrogen from the carbon and increase the O-C-H bond angle. We specified the Opt=(TS,CalcFC) keyword in the route section, requesting an optimization to a transition state. The CalcFC option is used to compute the initial force constants, a technique which is generally helpful for transition state optimizations. We ve also included the Freq keyword so that a frequency calculation will automatically be run at the optimized geometry. 

Depending on its subtraction from or addition to the buoyancy force, the continuous phase velocity can either increase or decrease the bubble volume. Normally, this velocity is such that the bubble detaches prematurely from the nozzle tip. Maier (M2) has shown that the shear force experienced by the bubble, which causes its premature detachment, is a maximum when the continuous phase flows at right angles to the nozzle axis. 

Fig. C-2(a) shows an attached shock wave on the tip of a wedge. This is a weak shock wave formed when the associated pressure difference is small. On the other hand, as shown in Fig. C-2(b), a detached shock wave is formed when the pressure difference becomes large. An attached shock wave becomes a detached shock wave when the wedge angle becomes large.

In peel separation, the adhesive simply peels away from the surface. Lap shear occurs when the adhered material is subjected to a force that is applied parallel to the bonding plane. Here, the bond becomes deformed and stretched after initial rupture of some portion of the bond. It is a sliding type of failure. In tensile detachment, bond disruption occurs as force is applied at right angles to the bonding surface. Tensile detachment is a ripping type of bond disruption. 

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