Direct or indirect measurements

A drawback to all methods discussed above, however, is that they fail to directly address the metabolic compart-mentation inherent in the brain. For example, direct or indirect measurement of oxygen metabolism using labeled... 

In addition to sampling in a sewer followed by analysis of specific components or use of a sample for further laboratory or pilot-scale experiments, a number of direct or indirect measurements must typically be performed in the sewer itself. Important measurements related to sewer process studies are DO, reaeration, biofilm characteristics and odor. 

However, it is possible to directly or indirectly measure the mass flux (mass flow) of conversion gas. Several authors have measured the mass loss of the fuel bed as function of primary air velocities and biofuel [12,33,38,53] by means of a balance. Most of them have used the over-fired batch conversion concept. They utilise the relationship illustrated by Eq. 16 (formulised in amounts instead of flows) above and the assumption that no ash is entrained. As a consequence, the mass loss of the batch bed with time equals the conversion gas. In the simple three-step model [3], an assumption of steady state is made, which is not relevant for batch studies. If it is practically possible, the method of using a balance to measure the conversion gas rate is especially appropriate for transient processes, that is, batch processes. 

Several recent and often sophisticated methods allow to make measurements of interfaciai recognition. These methods, performed either on Langmuir-Blodgett (LB) films or on vesicles allow the direct or indirect measurement of the binding... 

The Heisenberg space defines the available uncertainty space where, in quantum mechanics, it is possible to perform, direct or indirect, measurements. Outside this space, in the forbidden region, according to the orthodox quantum paradigm, it is impossible to make any measurement prediction. We shall insist that this impossibility does not result from the fact that measuring devices are inherently imperfect and therefore modify, due to the interaction, in an unpredictable way what is supposed to be measured. This results from the fact that, prior to the measurement process, the system does not really possess this property. In this model for describing nature, it is the measurement process itself that, out of a large number of possibilities, creates the physical observable properties of a quantum system. 

Pharmacokinetic Measures of Systemic Exposure Both direct (e.g., rate constant, rate profile) and indirect (e.g., Cmax, Tmax, mean absorption time, mean residence time, Cmax normalized to AUC) pharmacokinetic measures are limited in their ability to assess rate of absorption. This guidance, therefore, recommends a change in focus from these direct or indirect measures of absorption rate to measures of systemic exposure. Cmax and AUC can continue to be used as measures for product quality BA and BE, but more in terms of their capacity to assess exposure than their capacity to reflect rate and extent of absorption. Reliance on systemic exposure measures should reflect comparable rate and extent of absorption, which in turn should achieve the underlying statutory and regulatory objective of ensuring comparable therapeutic effects. Exposure measures are defined relative to early, peak, and total portions of the plasma, serum, or blood concentration-time profile, as follows ... 

These methods are based on the formation of a metal chelate complex, and then either directly or indirectly measuring its amount. Most of these methods do not differentiate between complexing agents, and are subject to interferences, and are not sufficiently sensitive for trace analysis. On the other hand, their rapidity and simplicity are unquestionable advantages. 

Photoacoustic spectroscopy (PAS) is revolutionary in the way that it is one of the few spectroscopic techniques that is not based on the direct or indirect measurement of electro-magnetic radiation. It is grounded on the ancient observation of Graham Bell, that the exposure of different solid and liquid substances to a rapidly interrupted beam of light results in the emission of acoustic energy at the same frequency as that at which the incident radiation was modulated. 

Figure 3-16 is helpful in the logical planning of a series of kinetic experiments to determine reaction orders and specific rate constants. However, it is important to remember the main goals and design of the entire experimental analysis. Table 3-5 gives methods used to determine direct or indirect measurements of a species concentration. 

In the first case, product purities are controlled indirectly by controlling front positions. In distillation columns the front positions are easily controlled with cheap, reliable and fast online temperature measurements on sensitive trays inside the column [27]. A similar procedure was recently proposed for moving-bed chromatographic processes with UV rather than temperature measurement [37]. However, the performance of such an approach is usually limited. Exact product specifications cannot be guaranteed because of this indirect approach. Furthermore, in combined reaction separation processes the relationship between the measured variable and the variable to be controlled is often non-unique, which may lead to severe operational problems as shown for reactive distillation processes [23], It was concluded that these problems could be overcome if in addition some direct or indirect measure of conversion is taken into account. 

When particle-size is obtained by direct or indirect measurement, careful consideration must be given to proper preparation of the samples. No difficulty is encountered with ordinary sieve-sizes. It is only when we are considering conglomerate material which consists of fine and coarse particles closely adhering to each other that difficulties arise. Likewise, some materials are of such a nature that they are not easily wetted and fail to disperse properly. The most essential feature of any particle-size determination is to disperse the material so that any small segment will contain sufficient particles to give a true representation of the whole. 

An updated review by Antolovich et al. (47) discusses the methods of determining antioxidant activity extensively. The methods used in measuring antioxidant activity may be categorized into three groups, which directly or indirectly measure the rate or extent of the following ... 

Direct or indirect measurements of rate constants for elementary steps therefore play a much greater role in the determination of mechanisms of one-electron than of two-electron reactions. However, there are some simplicities in radical kinetics not available to the investigator of two-electron reactions. Because radicals are electrically neutral, solvent effects are small to negligible, and absolute rate constants determined in one solvent can sometimes be applied to another, in a way impossible in two-electron chemistry. The following generalisations can be made ... 

These results suggest that we need to have direct (or indirect) measurement of compositions in the reaction section. This is discussed more fully in the next section, where a generic rule is proposed ... 

As alluded to earlier, copolymer composition measurement can be achieved by direct and indirect measurements. In some cases, one can infer the copolymer composition by measuring the amounts of monomers consumed in the process. Alternatively, one can directly measure the composition by sensing the characteristic moieties of the individual monomers bound in the copolymer chains. Several techniques are available for each of the direct or indirect measurement of the copolymer composition. 

In view of its occurrence in man and the higher apes, many have speculated on the possible correlation of uric acid levels and intelligence. Several papers have been published showing apparent positive correlation between the serum uric acid levels and either direct or indirect measurements of mental ability (D6, S15). In the year 1975, however, it would probably be improper to discuss these correlations since men, in general, have a higher uric acid level than women. 

This next section reviews and compares the different processing tests that arc used in the rubber industry today. These process tests either directly or indirectly measure one or more of the ten fundamental rubber properties just discussed. 

In the second part of this chapter, focus was on control of continuously operated RD processes. So far most control studies focus on processes that are operated close to chemical equilibrium. Emphasis was on the well-known esterification and etherification systems. The methods employed are similar to non-RD column control. It is worth noting that this is consistent with our conclusions on open-loop dynamics as drawn above. Additional problems may rise in indirect control schemes, where product compositions are inferred from temperature measurements. It was shown that these problems can be handled if in addition some direct or indirect measure of conversion is taken into account. 

In a narrower sense, however, the term kinetic method is confined to methods based on direct or indirect measurements of the rate of a chemical reaction, which ought to be called reaction-rate methods . This view is followed in this article. 

The determination of a given species using a kinetic method based on direct or indirect measurements of its reaction rate entails monitoring changes in the reactant or product concentration. The reaction rate is defined as the number of moles of substance that is consumed or formed per unit volume per unit time. Thus, for a straightforward reaction of the type... 

In many analytical techniques the response of the measurement system depends on a variety of experimental factors under the control of the operator. For example, enzyme assays involve the direct or indirect measurement of reaction rates. In a given experiment the reaction rate will depend on factors such as the temperature, the pH, ionic strength, and chemical composition of the buffer solution, the enzyme concentration, and so on. For a particular application it will be important to set the levels of these factors to ensure that (for example) the reaction rate is as high as possible. The process of finding these optimum factor levels is known as optimization. Several methods of optimization are discussed in detail in subsequent sections. But before an optimization process can begin we must determine which factors, and which interactions between them, are important in affecting the response it is also valuable to know which factors have little or no effect, so that time and resources are not wasted on unnecessary experiments. 

As Sutton noted (103), pacing appears to be a very effective means of symptom control, and there is no doubt that it does work in some patients. Based on the physiological processes at play in neurocardiogenic syncope, it should be remembered that a fall in blood pressure usually precedes the fall in heart rate. Thus, pacing determined by rate criteria alone may represent too little too late. The development of newer sensor technology that allows for the direct or indirect measurement of blood pressure would permit the onset of pacing at the earliest point in the syncopal episode. 

Soil concentration in the immersion cleaning bath and emulsion rinse vessel can be a significant issue. This is because the soil removal capability of a solvent mixture and a surfactant with semi-aqueous technology Is considerably greater than when only a surfactant is employed with conventional aqueous technology. So soil concentration Is 5 to 10 wt% vs. only Vi to 1 wt%. Hence, management of rinse quality is essential to success. That s why on-line direct or indirect measurements of soil concentration are (or should be) commonly done. 

As such, these methods cannot be readily applied to hard interfaces, whether between a solid and a vapor or between a solid and a liquid, because the elastic energy stored in the solid far exceeds the interface energy associated with any distortion. As a result, measuring the surface tension of solids is generally perceived as an impossible task. Nevertheless, there exist a few examples of direct or indirect measurements that are worth mentioning. 

The number and variety of ion-specific electrodes is rapidly increasing with no end in sight. At the present writing, it is possible to use such electrodes to determine, either by direct or indirect measurement, ionic concentrations of the following species ammonia, bromide, cadmium, calcium, chloride, cupric, cyanide, fluoride, fluoroborate, iodide, lead, nitrate, perchlorate, potassium, sulfide, sodium, sulfur dioxide, and thiocyanate, all by direct measurement, and by titration methods aluminum, boron, chromium, cobalt, magnesium, mercury, nickel, phosphate, silver, sulfate, and zinc. 

Direct or indirect measurements provide information about the amount(s) of radionuclides present in the body, in parts of the body such as specific organs or tissues, in a biological sample or in a sample from the working enviromnent. The first use of these data is likely to be an estimation of the intake of the radionuclide by the worker. Biokinetic models which describe body and organ contents, and activity in excreta, as a function of time following intake, and exposure models which relate intake to workplace conditions, are used for this purpose. Alternatively, measurements of activity in the body can be used to estimate dose rates directly. The calculation of committed doses from direct measurements still involves the assumption of a biokinetic model if sufficient measurements are not available to determine retention functions. 

An extensive class of experimental methods for the determination of transition probabilities is based on direct or indirect measurements of the... 

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