Mobility values

Concerning the nature of electronic traps for this class of ladder polymers, we would like to recall the experimental facts. On comparing the results of LPPP to those of poly(para-phenylene vinylene) (PPV) [38] it must be noted that the appearance of the maximum current at 167 K, for heating rates between 0.06 K/s and 0.25 K/s, can be attributed to monomolecular kinetics with non-retrapping traps [26]. In PPV the density of trap states is evaluated on the basis of a multiple trapping model [38], leading to a trap density which is comparable to the density of monomer units and very low mobilities of 10-8 cm2 V-1 s l. These values for PPV have to be compared to trap densities of 0.0002 and 0.00003 traps per monomer unit in the LPPP. As a consequence of the low trap densities, high mobility values of 0.1 cm2 V-1 s-1 for the LPPPs are obtained [39]. 

The Effect of Surfactant Concentrations, The effect of surfactant concentrations on CC -foam mobility is plotted on a log-log scale in Figure 3. The presented data points are the average mobility values obtained from a superficial velocity range of 2-10 ft/day, with the CC -foam fraction was kept constant around 80%. With Berea sandstone, ZS and AEGS surfactants were used. The measured average permeability of the Berea sandstone with 1% brine was 305 md. With Baker dolomite, AEGS was used to make comparison with Berea sandstone. The permeability of the Baker dolomite was 6.09 md measured with 1% brine solution. 

Experimental mobility values, 1.2 X 10-2 cm2/v.s. for eam and 1.9 x 10-3 cm2/v.s. for eh, indicate a localized electron with a low-density first solvation layer. This, together with the temperature coefficient, is consistent with the semicontinuum models. Considering an effective radius given by the ground state wave-function, the absolute mobility calculated in a brownian motion model comes close to the experimental value. The activation energy for mobility, attributed to that of viscosity in this model, also is in fair agreement with experiment, although a little lower. 

Figure 5.14 and Table 5.4 show the electrical characteristics of the fabricated TFTs (W/L = lOpm/lOpm). TFT-4 and 5 (Gox, UDL and channel Si are solution-processed) have the mobility values, 23,0cm2/Vs and 9.9cm2/Vs, respectively. They are lower than that of TFT-6 (only the channel silicon was solution-processed). In this experiment, however, the mobility of the reference TFT (TFT-6) is also relatively poor, as expected, because the laser power and other conditions under which the channel silicon was solution-processed were not optimized. Thus, the mobilities of TFT-4 and TFT-5 were also affected by the channel silicon and were much lower than the mobilities of TFT-1 and TFT-2. With optimization of the conditions under which the channel silicon is deposited, we believe that higher mobility values can be achieved in the devices with solution-processed Gox, UDL, and channel Si. 

The CBD CdS was also applied in other areas of device fabrication and application. Mereu et al.32 fabricated thin-film field-effect transistors using CBD CdS on Si02/Si (n-type) substrates. Meth et al.33 fabricated thin-film transistors (TFTs) that incorporated patterned CBD cadmium sulfide as the active layer. Mobility in the =1 -cm2/Vs range with on/off ratios of =105 are needed for practical TFTs (e.g., for displays). Mobility values of 0.1 -1 cm2/Vs with on/off ratios exceeding 107 have been reported for these types of TFTs using CBD CdS. 

Figure 12.3. Benchmark of peer-reviewed academic reports of organic semiconductor device field-effect mobility versus time of report. All data points are for spin-coated organic semiconducting transistors. Solid points are derived from the benchmark study completed in 2002 by Brazis and Dyrc at Motorola (unpublished). The curve is a calculated estimation, based on these data, of what the expected mobility values will be in the future. The open points are data derived in 2005 from the public journals for verification of the 2002 prediction.6 38... 

Up to this point, water mobility values obtained are average values for an entire sample. However, if magnetic field gradients in the x, y, and z directions are incorporated into a pulsed NMR experimental setup, the spatial distribution aspects of water mobility (7), T2, and D) can also be measured via the use of magnetic resonance imaging (MRI) techniques. 

Table 2 lists limiting equivalent conductance and association constant values for a number of 1 1 electrolytes in the solvents of Table 1, and Table 3 gives single ion mobility values. The data include results that appear to have sufficient precision to give meaningful values when treated by the Fuoss-On-sager conductance equation. In a few cases data of somewhat lower precision have been included to indicate the magnitude of the association constants, which can often be determined with fair accuracy from such data. 

Several cell lines were screened for their response to three standard chemotherapy drugs fludarabine, vincristine, and Gleevec decreases in the mean optophoretic distance of Bcr-Abl positive cell line K-562 with no effect in the other cell lines demonstrate that the downshift in mean displacement is specific to the presence of the Bcr-Abl oncoprotein fludarabine, however, was ineffective in causing a decrease in the optophoretic displacement of the K-562 cell line, but showed an effect in the other four cell lines mobility values for each cell in the population have been taken and averaged, but data on subsets of the cells can still be extracted and further analyzed. 

In the case of Nafion, a similar situation occurs. There is a sharp increase in proton conductivity and proton concentration as a function of water content followed by a decrease at A > 20. At these higher water contents, Nafion undergoes a similar dilution of proton concentration per BAM membrane in conjunction with a lower mobility value versus ETFE-g-PSSA. However,... 

It is interesting to note, however, that even though the SPEEKK sample shown in Figure 3.22 has a higher lEC content (1.46 meq/g) than sPS02-781 (1.28 meq/g), it exhibits overall lower conductivity for a given water content. Based on an examination of the proton mobility values for these polymers, it was suggested that this may be due to some microstructural differences between the two different systems. Proton conductivity as a function of... 

Electrokinetic Measurements. Electrophoretic mobilities were measured with a flat-cell apparatus manufactured by Rank Brothers, Cambridge, England. In addition, several mobility values were checked for accuracy with a Zeta Meter, New York. Mobilities were determined with a small volume of the suspension (approximately 25 cc) that had been prepared for the adsorption experiments. The pH of the solution was measured prior to determining the electrophoretic mobilities, which involved measuring the velocities of five to ten particles in each direction. An average value of the mobilities was recorded. Samples containing the flocculated particles were dipped into an ultrasonic bath for approximately one second prior to making the pH and mobility measurements. 

Since all electrophoretic mobility values are proportional to the reciprocal viscosity of the buffer, as derived in Chapter 1, the experimental mobility values n must be normalized to the same buffer viscosity to eliminate all other influences on the experimental data besides the association equilibrium. Some commercial capillary zone electrophoresis (CZE) instruments allow the application of a constant pressure to the capillary. With such an instrument the viscosity of the buffer can be determined by injecting a neutral marker into the buffer and then calculating the viscosity from the time that the marker needs to travel through the capillary at a set pressure. During this experiment the high voltage is switched off. 

The first work on pKa determination by zone electrophoresis using paper strips was described by Waldron-Edward in 1965 (15). Also, Kiso et al. in 1968 showed the relationship between pH, mobility, and p/C, using a hyperbolic tangent function (16). Unfortunately, these methods had not been widely accepted because of the manual operation and lower reproducibility of the paper electrophoresis format. The automated capillary electrophoresis (CE) instrument allows rapid and accurate pKa determination. Beckers et al. showed that thermodynamic pATt, (pATf) and absolute ionic mobility values of several monovalent weak acids were determined accurately using effective mobility and activity at two pH points (17). Cai et al. reported pKa values of two monovalent weak bases and p-aminobenzoic acid (18). Cleveland et al. established the thermodynamic pKa determination method using nonlinear regression analysis for monovalent compounds (19). We derived the general equation and applied it to multivalent compounds (20). Until then, there were many reports on pKa determination by CE for cephalosporins (21), sulfonated azo-dyes (22), ropinirole and its impurities (23), cyto-kinins (24), and so on. 

Unlike inorganic semiconductors whose mobility ranges from a few cm2/Vsec up to jjhn =77,000 cm2/Vsec (in InSb), organic dyes because of the influence of the high density of traps and narrow energy bands have mobility values that lie between very low values (< 10-4 cm2/Vsec) and values of 1—50 cm2/Vsec. 

A major remaining problem is that many systems of interest in colloid chemistry do not correspond to either of these two limiting cases. The situation is summarized in Figure 12.4, which maps the particle radii Rs and 1 1 electrolyte concentrations that correspond to various kRs values. Clearly, there is a significant domain of particle size and/or electrolyte concentration for which neither the Huckel nor the Helmholtz-Smoluchowski equations can be used to evaluate f from experimental mobility values. The relationship between f and u for intermediate values of kRs is the topic of the following section. 

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