Other Measurements

Several other derivative measurement parameters may also of interest in the electrochromism of CPs for specialized applications. The most straightforward of these are differential measurements, e.g. of the differential Absorbance or Transmittance of various doped states of a CP with reference to its pristine, undoped state. Figs. 3-34 and 3-35 show two such differential plots. In the first, (a) shows the standard SPEL, while (b) shows its differential the differential plot simply serves to enhance the trends observed in the SPEL, but also serves to accurately pinpoint the isosbestic point. In the second, the differential absorbance monitoring a bipolaron absorption at 700 nm shows that up to an applied potential of ca. 0.6 V, the formation of bipolarons appears minimal after 0.6 V, however, bipolarons form rapidly. 

Other important derivative measurements are those of thermal Emittance, e and Solar Absorptance, Both can be derived directly from Reflectance measurements, and both have importance in radiative loss applications, e.g. in space. For instance, satellites and spacecraft ideally require high reflection of solar heat during sunfacing, implying a low a 0.2, while at the same time having high radiative capability 

The corresponding equations for the solar absorptance, as, are similar. Table 3-1 lists and as values obtained for a poly(aromatic amine) CP system, in a two-electrode mode, sealed device in the author s laboratory. 

Electrochromism can be said to encompass any property of CPs that varies with applied potential or doping. This may include conductivity. An application for conductivity electrochromism may be envisioned for instance with a Au grid on a flexible substrate on which a CP is deposited. When the CP is cycled between conductive and non-conductive states, the dielectric permittivity of the material, affecting its microwave/radar signatures, changes dramatically. We thus have a CP microwave/radar electrochromism of sorts. Such uses are dealt with in the Applications section of this book. 

TABLE 3-1 Emittance (e) and Solar Absorptance (a s) values calculated for a Poly-(aromatic Amine) system with a polymeric dopant in several device configurations (here labeled CONI, CON2, and CONS), from difriise reflectance data, as a function of applied potential in 2-electrode mode. Data courtesy of Ashwin -Ushas Corp., Inc. 

The systematic measurements for chymotrypsin and lysozyme show that these enzymes differ in the hydration level of the onset of enzyme activity. The difference is sufficiendy great that experimental arufacts related to the methods of determining the extent and onset of the reaction cannot be the explanation. The other measurements cited above, although perhaps less cleanly interpretable, show threshold hydration levels ranging from below 0.1 to above 0.3 h. Apparendy, there is no single hydration level characterisdc of the onset of enzyme activity. This is not surprising, because the way in which water of the hydration shell enters into the enzyme reaction should depend on the mechanism of the reaction. 

Micelles form when a suitable amphiphile [e.g., sodium bis(2-ethyl-hexyl)sulfosuccinate (AOT)], is introduced into a hydrocarbon solvent (e.g isooctane). Reverse micelles containing water form when water is taken up by an isooctane—AOT solution. At water contents exceeding what is needed to saturate the polar head groups forming the micelle wall, the system can properly be termed a water-in-oil microemulsion, in which water droplets stabilized by a monolayer of surfactant are dispersed in an organic solvent. For convenience, the terms reverse micelle and microemulsion are sometimes considered equivalent. There is a considerable literature on the properties of proteins, particularly enzyme activity, in reverse micelles (see Luisi and Steinmann-Hofmann, 1987, and references cited therein). 

The properties of a protein in a reverse micelle depend strongly on water content. Typically, at mole ratios of water to surfactant (wo) of less than about 3, there is no enzyme activity. As Wg is increased the activity sharply rises, sometimes to an optimum value at Wg — 5-20. The value of kcat for chymotrypsin is as much as 5-fold greater in AOT reverse micelles than it is in aqueous solution (Barbaric and Luisi, 1981 Fletcher 

Enzymes are active in organic solvents at low water contents. Porcine pancreatic lipase in glycerin tributyrate (tributyrin) shows, for 0.015% water in the tributyrin—pentanol reaction mixture, a rate of transesterification comparable to the value in aqueous solution (Klibanov, 1986 Zaks and Klibanov, 1984). The water content of the protein in the above reaction mixture was 0.01—0.03 h. This is below the level expected for the onset of enzyme activity in protein—water powders. Nonaqueous solvents can produce change in the substrate specificity of an enzyme (Zaks and Klibanov, 1986 Zaks and Klibanov, 1988a) and possibly can lock the enzyme into a more active conformation (Russell and Klibanov, 1988). The dependence of the catalytic activity on added water has been measured for several enzymes in several solvents (Zaks and Klibanov, 1988b). 

Interesting chemistry is associated with micellar and nonaqueous environments. Three-component systems, however, can be difficult to understand, and for the present our knowledge of protein hydration in two-component systems is more likely to throw light on three-component systems than the reverse. 

Structure measures assess the accessibility, availability, and quality of resources, such as health insurance, bed capacity of a hospital, and the number of nurses with advanced training. Process measures assess the delivery of healthcare services by clinicians and providers. Outcome measures indicate the final result of care. Many useful measures can apply to different settings. Without commitment and support of senior-level leadership, even the best intended projects can fail. Champions of quality initiatives and improvement process need to be visible throughout the organization, but especially in leadership positions and on the team. 

Calibration can be done using standard sources off-line or in-situ during static preheat using a thermocouple placed in close proximity to the IR probe. The temperature reading for the IR system will be influenced by the emissivity of the polymer melt and the stem heating effects. 

Pressure and temperature are two process parameters of major importance. There are, however, various other parameters, which cannot be ignored. 

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As a consequence, other than its use in the ndM method, the refractive index is very often used in process operations because it can indicate smaii differences in product quality that would be missed by other measurements. The only restriction is that the color of the sample should be less than 5 on the ASTM D 1500 scale. 

The formation bulk density (p ) can be read directly from the density log (see Figure 5.51) and the matrix density (p J and fluid density (p,) found in tables, assuming we have already identified lithology and fluid content from other measurements. The equation can be rearranged for porosity ((])) as follows ... 

Since it is not possible to measure a single electrode potential, one electrode system must be taken as a standard and all others measured relative to it. By international agreement the hydrogen electrode has been chosen as the reference ... 

Other measurements by Adzumi [36] are often quoted as further support for this statement. However, it is doubtful whether Adzumi s results extend to low enough pressures to be sure of this. 

Measurements usually consist of a unit and a number expressing the quantity of that unit. Unfortunately, many different units may be used to express the same physical measurement. For example, the mass of a sample weighing 1.5 g also may be expressed as 0.0033 lb or 0.053 oz. For consistency, and to avoid confusion, scientists use a common set of fundamental units, several of which are listed in Table 2.1. These units are called SI units after the Systeme International d Unites. Other measurements are defined using these fundamental SI units. For example, we measure the quantity of heat produced during a chemical reaction in joules, (J), where... 

Consider, for example, the data in Table 4.1 for the mass of a penny. Reporting only the mean is insufficient because it fails to indicate the uncertainty in measuring a penny s mass. Including the standard deviation, or other measure of spread, provides the necessary information about the uncertainty in measuring mass. Nevertheless, the central tendency and spread together do not provide a definitive statement about a penny s true mass. If you are not convinced that this is true, ask yourself how obtaining the mass of an additional penny will change the mean and standard deviation. 

In practice, intermediate, Hquid resins, capable of further reaction are usually prepared. Polymerization is carried to an estabUshed end-point as determined by viscosity or other measurements. When the proper end-point has been reached, the reaction is terminated by adjusting the pH of the system to 5—8. Such hquid resins can be stored for six months or longer, then catalyzed and reacted further to obtain the final, desired product. 

Measurement Requirements. Any analysis of measurement requirements must begin with consideration of the particular accuracy, repeatabihty, and range needed. Depending on the appHcation, other measurement considerations might be the speed of system response and the pressure drop across the flow meter. For control appHcations repeatabihty may be the principal criterion conversely for critical measurements, the total installed system accuracy should be considered. This latter includes the accuracy of the flow meter and associated readout devices as well as the effects of piping, temperature, pressure, and fluid density. The accuracy of the system may also relate to the required measurement range. 

MohsAn early (1822) hardness comparison test involved assigning a relative number to aH known materials (usuaHy minerals and pure metals) by virtue of their relative abHity to scratch one another. The results of this classification are not relatable to other properties of materials or to other measures of hardness. As a result of this limited useflilness, the Mohs hardness test is primarily used for mineral identification. Some examples of the Mohs hardness scale, which ranks materials from 1 to 10, are Hsted in Table 6. 

Health and Safety Factors. MEK is slightly more toxic than acetone, but is not considered highly toxic, and nor does it exhibit cumulative toxicological properties. The OSHA time weighted average iu air is 200 ppm other measured toxicity values are shown iu Table 3. Methyl ethyl ketone is highly flammable. 

Other Measurements. Other tests include free moisture content, rate of dissolution and undissolved residue in acids and alkaH, resin and plasticizer absorption, suspension viscosity, and specific surface area. Test procedures for these properties are developed to satisfy appHcation-related specifications. 

The pareto chart, tool number six, is a special type of histogram (48) where the frequency data is grouped in order of decreasing occurrence or other measures of importance rather than in sequential or numerical order. The chart, an example of which is shown in Figure 6, illustrates the causes in decreasing order of importance. It enables the improvement effort to be focused where it can have the most impact and is an effective management communication tool. 

AH three parameters, the cut size, sharpness index, and apparent bypass, are used to evaluate a size separation device because these are assumed to be independent of the feed size distribution. Other measures, usually termed efficiencies, are also used to evaluate the separation achieved by a size separation device. Because these measures are dependent on the feed size distribution, they are only usefiil when making comparisons for similar feeds. AH measures reduce to either recovery efficiency, classification efficiency, or quantitative efficiency. Recovery efficiency is the ratio of the amount of material less than the cut size in the fine stream to the amount of material less than the cut size in the feed stream. Classification efficiency is defined as a corrected recovery efficiency, ie, the recovery efficiency minus the ratio of the amount of material greater than the cut size in the fine stream to the amount of material greater than the cut size in the feed stream. Quantitative efficiency is the ratio of the sum of the amount of material less than the cut size in the fine stream plus the amount of material greater than the cut size in the coarse stream, to the sum of the amount of material less than the cut size in the feed stream plus the amount of material greater than the cut size in the feed stream. Thus, if the feed stream analyzes 50% less than the cut size and the fine stream analyzes 95% less than the cut size and the fine stream flow rate is one-half the feed stream flow rate, then the recovery efficiency is 95%, the classification efficiency is 90%, and the quantitative efficiency is 95%. 

Sta.bilizers. Cyanuric acid is used to stabilize available chlorine derived from chlorine gas, hypochlorites or chloroisocyanurates against decomposition by sunlight. Cyanuric acid and its chlorinated derivatives form a complex ionic and hydrolytic equilibrium system consisting of ten isocyanurate species. The 12 isocyanurate equilibrium constants have been determined by potentiometric and spectrophotometric techniques (30). Other measurements of two of the equilibrium constants important in swimming-pool water report significantly different and/or less precise results than the above study (41—43). A critical review of these measurements is given in Reference 44. 

An important aspect of economic consideration is the prevention of egg and egg product loss to the drain or the atmosphere, eg, a checked or cracked egg may be broken in the washer, and the contents go down the drain with the wash water. Other measurable losses during egg product production are Hsted in Table 5. 

In addition to this drive to look beyond manufacturing to specifications, new analytical methods such as molecular weight distribution, Mooney relaxation, and other measures of polymer processibiHty are being explored. 

Measured on extmded samples, all others measured on injection molded samples. 

The norm is useful when doing numerical calculations. If the computer s floating-point precision is 10" , then K = 10 indicates an ill-conditioned matrix. If the floating-point precision is I0" (double precision), then a matrix with K = I0 may be ill-conditioned. Two other measures are useful and are more easily calculated ... 

Consider next the problem of estimating the error in a variable that cannot be measured directly but must be calculated based on results of other measurements. Suppose the computed value Y is a hnear combination of the measured variables [yj], Y = CL y + Cioyo + Let the random variables yi, yo,. . . have means E yi), E y, . . . and variances G yi), G y, . The variable Y has mean... 

Peiformance. Depending on the application, accuracy, repeatability, or perhaps some other measure of performance is appropriate. Where closed loop control is contemplated, speed of response must be included. 

Other measures of efficiency are derived from the experimental RTD, which is characterized at least approximately by the variance This quantity is zero for plug flow and unity for complete mixing, and thus affords natural bounds to an efficiency eqiiated to the variance. It is possible, however, for the variance to fall out of the range (0,1) when stagnancy or bypassing occurs. 

Detonation arresters are typically used in conjunction with other measures to decrease the risk of flame propagation. For example, in vapor control systems, the vapor is often enriched, diluted, or inerted, with appropriate instrumentation and control (see Effluent Disposal Systems, 1993). In cases where ignition sources are present or pre-dic table (such as most vapor destruct systems), the detonation arrester is used as a last-resort method anticipating possible failure of vapor composition control. Where vent collec tion systems have several vapor/oxidant sources, stream compositions can be highly variable and... 

Systematic Measurement Error Fourth, measurements are subject to unknown systematic errors. These result from worn instruments (e.g., eroded orifice plates, improper sampling, and other causes). While many of these might be identifiable, others require confidence in all other measurements and, occasionally, the model in order to identify and evaluate. Therefore, many systematic errors go unnoticed. 

Understanding the positions of sample and other measurement locations within the equipment is also important. The presence or absence of isolation valves needs to be identified. While isolation valves may be too large for effective sampling, their absence will require that pipe fitters add them such that sample valves can be connected. This must be done in advance of any test. If analysts assume that samples are from a liquid stream when they are vapor or that temperature measurements are within a bed instead of outside it, interpretation of results could be corrupted. Analysts should also develop an understanding of control transmitters and stations. The connection between these two may be difficult to identify at this level in fully computer-controlled units. 

Validation versus Rectification The goal of both rectification and validation is the detecI ion and identification of measurements that contain systematic error. Rectification is typically done simultaneously with reconciliation using the reconciliation resiilts to identify measurements that potentially contain systematic error. Vahdation typically rehes only on other measurements and operating information. Consequently, vahdation is preferred when measurements and their supporting information are hmited. Further, prior screening of measurements limits the possibihty that the systematic errors will go undetected in the rectification step and subsequently be incorporated into any conclusions drawn during the interpretation step. 

Recommendations Once measurements are made, vahdation is the most important step for establishing a sound set of measurements. The comparisons against other measurements or other known pieces of information qmckly identify suspecl measurements. Spreadsheet analysis of constraints, particularly material and energy balances, identifies other weaknesses in the measurements and provides the opportunity for discussions with those responsible before considerable analysis effort is expended. Finally, initial adjustments provide the beginnings of the interpretation analysis. 

U.se additional mea.surement. sets that were not included in the development of the parameter e.stimate.s to te.st their accuracy. A certain subset of the raw or adjusted measurements is used to adjust the parameter estimate. Once the optimal values are attained, the model is used to predict values to compare against other measurement sets or subsets. These additional measurements provide an independent check on the parameter estimates and the model vahdity. 

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