Ripple experiment

The ripple experiment works as follows In Fig. 6, HDH and DHD are depicted by open and filled circles where the filled circles represent the deuterium labeled portions of the molecule and the open circles are the normal (protonated) portions of the chains. Initially, the average concentration vs. depth of the labeled portions of the molecules is 0.5, as seen along the normal to the interface, unless chain-end segregation exists at / = 0. If the chains reptate, the chain ends diffuse across the interface before the chain centers. This will lead to a ripple or an excess of deuterium on the HDH side and a depletion on the DHD side of the interface as indicated in the concentration profile shown at the right in Fig. 6. However, when the molecules have diffused distances comparable to Rg, the ripple will vanish and a constant concentration profile at 0.5 will again be found. 

Fig. 6. The ripple experiment at the interface between a bilayer of HDH- and DHD-labeled polystyrene, showing the interdifussion behavior of matching chains. The protonated sections of the chain are marked by filled circles. The D concentration profiles are shown on the right. Top the initial interface at / = 0. The D concentration profile is flat, since there is 50% deuteration on each side of the interface. Middle the interface after the chain ends have diffused across (x < / g). The deuterated chains from Que side enrich the deuterated centers on the other side, vice ver.sa for the protonated sections, and the ripple in the depth profile of D results. A ripple of opposite sign occurs for the H profile. Bottom the interface when the molecules have fully diffused across. The D profile becomes flat [20,56].

Fig. 8. SIMS analysi.s of the ripple experiment. Exces.s deuterium depth profiles for the HDH + DHD bilayer annealed at 118°C (a) The ripple inereasing from 30 to 1080 min. (b) The ripple amplitude deereasing with inereasing time from 1080 to 2880 min [20,57].

The Ripple Experiment Agrawaletal. (37) carried out what they called the ripple experiment, using neutron reflectometry on selectively deuterated polystyrene block copolymer chains in two layers. In one of the layers, the central 50% of the mers were deuterated, the two end 25% portions were normal, that is, bearing hydrogen. This material was denoted as HDH (1/4H-1/2D-1/4H). In the second layer, the chain labeling was reversed to make DHD (1/4D-1/2H-1/4D). The molecular weights of the two polymers were nearly identical, 2.25 x 10 g/mol, and 2.50 x 10 g/mol, respectively, synthesized by anionic polymerization to have narrow polydispersity indices. 

Welp et al. (43) continued the ripple experiment, going to 400,000 g/mol polystyrene to obtain a better definition of the ripple. They concluded that the reptation model proposed by de Gennes (44) with parallel development by Doi and Edwards (45) was the best model to describe the dynamics of polymer interdiffusion. There were six dominant ripple characteristics that were examined ... 

Figure 12.15 Ripple experiment results. Concentration profiles obtained from neutron reflection experiments are shown at several annealing times. Top profiles from 10 to 450 min. Bottom profiles from 450 to 1830 min. Here, Tbo 21 min and td = 1860 min.

How does the minor chain reptation model work with reference to the ripple experiment (Please limit description to 100 words and a drawing.)... 

Fig. 9. A correlation chart for the observed/predicted ripple characteristics for the reptation, Rouse and polymer mode coupling models. The restation model gives the best correlation ( 1) between theory and experiment.

Whereas the main challenge for the first bilayer simulations has been to obtain stable bilayers with properties (e.g., densities) which compare well with experiments, more and more complex problems can be tackled nowadays. For example, lipid bilayers were set up and compared in different phases (the fluid, the gel, the ripple phase) [67,68,76,81]. The formation of large pores and the structure of water in these water channels have been studied [80,81], and the forces acting on lipids which are pulled out of a membrane have been measured [82]. The bilayer systems themselves are also becoming more complex. Bilayers made of complicated amphiphiles such as unsaturated lipids have been considered [83,84]. The effect of adding cholesterol has been investigated [85,86]. An increasing number of studies are concerned with the important complex of hpid/protein interactions [87-89] and, in particular, with the structure of ion channels [90-92]. 

The realization that tubules may be formed on temperature reduction of polymerized SUVs, prepared from polymerizable diacetylenic phosphatidylcholines (21 where n = 7-16 and m = 5-11), represented a major breakthrough in obtaining the desired supramolecular structure [355-360]. In the initial experiments, 0.4- to 1.0-pm-diameter and 10- to 1000-pm-long tubules were prepared by the gradual lowering of the temperature (to about 38 °Q of 21 (m = 8, n = 9) SUVs [358]. The walk of the tubules had thickness of 10-40 nm and were coated by spiral ripples and helical bilayer strips. Many tubules contained trapped SUVs. Polymerization of the acetylenic moieties greatly enhanced the mechanical and thermal stabilities of the tubules [355-360]. 

Within 30 seconds ofthe initial inhalation, definite changes in the smoker s perception should be apparent. As the salvinorin A enters the bloodstream, the smoker will feel a humming and tingling which ripples in waves all over the body. The "peak" of the experience will occur within a minute, and typically continue for as long as two to three minutes. The sensation abruptly tapers off after this point, leaving one quite near baseline within seven... 

Shirotsuka et al. (Sll), 1957 Experiments on film flow in vertical channel, 8 cm. wide Nn = 100-1500 zero or countercurrent air flow. Data on local film thicknesses, wave heights, wave frequencies, increase in surface area due to rippling, with and without air flow. 

The current may be drawn from a commercially available battery charger (Note 4) or from a storage battery, each capable of operating at about 6 volts. Experiment has shown that the considerable ripple in the output of the charger has no adverse effect on the reduction. A transformer in the input to the charger, or a variable resistance in the battery circuit, and a 0-3 ampere range d.c. ammeter complete the apparatus. 

The eighth effect, "experimenter s identity," at first increases as the subject goes down to about 30 in hypnosis that is, he becomes more and more aware of the experimenter. The experimenter then seems to become more an more distant and remote, and finally the experimenter possesses no identity, he is just a voice, and at the very deep levels he is "just an amusing, tiny ripple at the far fringes of an infinite sea of consciousness." There is slight discrepancy at 50 between william s actual experience and his estimate of what he generally experienced. 

Figure 1. Neutron-scattering experiment result for the pair correlation function g(r) of liquid argon at T = 85 K and V = 28.26 cm3 mor1, near the triple point. Notice that the ripples at small r are artifacts of the data treatment. Taken from Ref. [19].

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