Velocity pulling

Fig. 5. Theory vs. experiment rupture forces computed from rupture simulations at various time scales (various pulling velocities Vcant) ranging from one nanosecond (vcant = 0.015 A/ps) to 40 picoscconds (vcant = 0.375 A/ps) (black circles) compare well with the experimental value (open diamond) when extrapolated linearly (dashed line) to the experimental time scale of milliseconds.

To summarize, the most likely scaling behavior of the primary cell spacing A, depending on pulling velocities, follows Eq. (99) as a consequence of the arguments presented in this section supported by a number of recent experiments (Billia et ah, Somboonsuk, Kurowsky, Esaka, and Kurz, cited in [122]). 

Manual sampling techniques can introduce error by virtue of variations in strength and size of the human hand, from analyst to analyst. As a result, the pulling velocity through the filter may vary considerably. Too rapid a movement of liquid through the filter can compromise the filtration process itself. 

Fig. 15.4. Determination of the opened state of TK. (a) TK is unfolded to a certain state. This conformation, determined by the extension Ax, is now frozen for a time At of 200 ms. During this time, ATP has the possibihty to bind. By further unfolding, it is probed with barrier 2 whether ATP is bound or not. All states before barrier 2 can be tested by varying Ax. (b) If the time pulse At is set before barrier 1 or between barriers 1 and 2, only the low value of ATP binding is observed which is due to the finite pulling velocity (to = 6 ms). However, if the time pulse is set after barrier 2 and before 2, ATP binding shows, within the experimental error, the large saturation value. Therefore, one can conclude that the binding pocket is opened after barrier 2...

Fig. 26. Potentials of mean force as computed with SMD, SMD-NH and EXEDOS simulations. As the pulling velocity is reduced, the SMD estimates converges towards the EXEDOS results (from Rathore et al. [32])...

Problem 6-7. Coating Flows The Drag-Out Problem A very important model problem in coating theory is sometimes called the drag-out problem. In this problem, a flat plate is pulled through an interface separating a liquid and a gas at a prescribed velocity U. The primary question is to relate the pull velocity U to the thickness // of the thin film that is deposited on the moving plate. We consider the simplest case in which the plate is perpendicular to the horizontal interface that exists far from the plate. The density of the liquid is p, the viscosity //, and the surface tension y. 

An approach that is almost diametrically opposed to the earlier models of Khan and Armstrong, and Kraynik and Hansen, was advanced by Schwartz and Princen (108). In this model, the films are negligibly thin, so that all the continuous phase is contained in the Plateau borders, and the surfactant tiuns the film surfaces immobile as a result of surface-tension gradients. Hydrodynamic interaction between the films and the Plateau borders is considered to be crucial. This model, believed to be more realistic for common sur factant-stabilized emulsions and foams, draws on the work of Mysels et al. (109) on the dynamics of a planar, vertical soap film being pulled out of, or pushed into, a bulk solution via an intervening Plateau border. An important result of their analysis is commonly referred to as FrankeTs law, which relates the film thickness, 2h., to the pulling velocity, U, and may be written in the form ... 

The sample is clamped in a relaxed condition along the warp directiom Therefore, the warp yams are the opposed yams. The middle weft yam with a 10 mm free end was pulled in the pullout test. The pulling velocity was 10 nun/min and it kept Deed until the pulled yam left the weave completely. The pullout force was measured by a Zwick tensiometer model 1440-60 (made in Germany). The test was repeated Q e times for each fabric. 

Fig. 11 Simulation of the stretching of acetylenes. The upper panel shows that that shorter chain molecules rupture at lesser extensions and that the slope of the potential is greater which results in a larger rupture force. The lower panel compares decapentane at three different pulling velocities where slower velocities result in rupture at greater extensions and therefore lower rupture forces. Reprinted with permission from U. F. Rohrig and I. Frank, /. Chem. Phys., 2001, 115, 8670-8674. Copyright 2001 American Institute of Physics.

In contrast to the molecular dynamics based studies mentioned so far, this approach applies a constant force, as opposed to a constant pulling velocity to the molecule. Using the results from the simulations, a force modified potential energy surface was constructed according to ... 

Because the rupture event is a stochastic process, the rupture forces are distributed in a certain range. Therefore, as in the experimental studies, we performed a large number of simulations and analyzed the rupture force distributions and the rejoin force distributions. The mean values as a function of the pulling velocity represent the so-called force spectmm. Experimentally, often a logarithmic dependence of the mean rupture force on v is observed, but the data collected by Schlesier et al. [98] allow no definite conclusion regarding this dependence. 

The time-dependence of the force is determined by the protocol applied in the actual application of DFS. One common way to perform the experiments or simulations is the force-ramp mode, in which the applied force increases with a constant velocity, F t) = where k denotes the force constant of the pulling device. The other protocol, called force-clamp mode, crmsists in the application of a constant external force, F(t) = Fext- In the force-ramp case, one finds the logarithmic dependence of the mean rupture force and v quoted above. The simple model appears to work quite well for small pulling velocities but fails if one pulls fast. In this simation, more detailed calculations of the rupture force distributions via the computation of the mean first passage time in model free-energy landscapes give more reliable results [104]. 

Fig. 37 Rupture forces corresponding to AL fs 1 nm and AZ, 2 nm as a function of loading rate (a) 60, (b) 300, (c) 1,500, (d) 6,000, and (e) 30,000 pN/s. Generally, rupture forces increase with pulling velocity and differences in rupture forces become more distinct with higher...

An experiment with resultant pulling velocity 0.049 0.003 p,m/s, volume fraction (p = 1.00% and 1 mM NaCl was carried out in order to obtain a thin colloidal film. The... 

Figure 5a shows the stripe distance as a function of the applied pulling speed for four different volume fractions. At higher pulling velocity, the distance of the stripes becomes smaller. This is also observed decreasing the volume fraction. Both factors are related to the film thickness which can easily be seen from the following formula proposed by Nagayama [18] ... 

Fig. 5 a Stripe size as a function of the pulling velocity at several volume fractions for 590 nm PS suspensions with a salt concentration of 1 mM NaCl. b Sample thickness as a function of the pulling velocity at several volume fractions for 590 mn PS suspensions with a salt concentration of 1 mM NaCl. The thin line is a guide to the eye showing the expected 1 /ii-dependence of the sample thickness... 

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