Viewpoints practice

With a typical ablated particle size of about 1 -pm diameter, the efficiency of transport of the ablated material is normally about 50% most of the lost material is deposited on contact with cold surfaces or by gravitational deposition. From a practical viewpoint, this deposition may require frequent cleaning of the ablation cell, transfer lines, and plasma torch. 

Essential Features of Optimization Problems The solution of optimization problems involves the use of various tools of mathematics. Consequently, the formulation of an optimization problem requires the use of mathematical expressions. From a practical viewpoint, it is important to mesh properly the problem statement with the anticipated solution technique. Every optimization problem contains three essential categories ... 

Package-filling and -handling machinery, workplace design, warehouse practice, and acceptability of packages from workplace and warehouse viewpoint. 

In the pH range 7-11, in which the dye itself exhibits a blue colour, many metal ions form red complexes these colours are extremely sensitive, as is shown, for example, by the fact that 10 6 — 10 7 molar solutions of magnesium ion give a distinct red colour with the indicator. From the practical viewpoint, it is more convenient to define the apparent indicator constant K ln, which varies with pH, as ... 

The availability of the initial material and its relative cheapness make this type of SAH highly attractive from a practical viewpoint. They are manufactured commercially by a number of companies for agricultural, sanitary, and hygienic applications. 

Nevertheless, from a practical viewpoint physical reasons for viscosity reduction during the surface treatment of the filler play a minor role first of all the effect of viscosity reduction itself is significant. 

From a practical viewpoint toughness is readily understood, but technically there tends to be no scientific method of measuring it. One definition of toughness is simply the energy required to break the plastic. This... 

It is noteworthy that even a separate treatment of the initial data on branched reactions (1) and (2) (hydrogenation of crotonaldehyde to butyr-aldehyde and to crotyl alcohol) results in practically the same values of the adsorption coefficient of crotonaldehyde (17 and 19 atm-1)- This indicates that the adsorbed form of crotonaldehyde is the same in both reactions. From the kinetic viewpoint it means that the ratio of the initial rates of both branched reactions of crotonaldehyde is constant, as follows from Eq. (31) simplified for the initial rate, and that the selectivity of the formation of butyraldehyde and crotyl alcohol is therefore independent of the initial partial pressure of crotonaldehyde. This may be the consequence of a very similar chemical nature of both reaction branches. 

Radical polymerization is often the preferred mechanism for forming polymers and most commercial polymer materials involve radical chemistry at some stage of their production cycle. From both economic and practical viewpoints, the advantages of radical over other forms of polymerization arc many (Chapter 1). However, one of the often-cited "problems" with radical polymerization is a perceived lack of control over the process the inability to precisely control molecular weight and distribution, limited capacity to make complex architectures and the range of undefined defect structures and other forms of "structure irregularity" that may be present in polymers prepared by this mechanism. Much research has been directed at providing answers for problems of this nature. In this, and in the subsequent chapter, we detail the current status of the efforts to redress these issues. In this chapter, wc focus on how to achieve control by appropriate selection of the reaction conditions in conventional radical polymerization. 

When the promoting, ion does not react at all with any of the reactants (e.g. Na ) then, in principle, infinite A values are expected. In practice Ais always measurable due to a very slow consumption of Na+to form surface oxides and carbonates.32,36,51 Nevertheless in all cases the most important parameter from a catalytic viewpoint is the promotion index19, PIis defined in Chapter 2 (eq. 2.19) and also shown in Table 4.1. 

One of the most interesting and potentially important from a practical viewpoint aspect of electrochemical promotion is the permanent NEMCA effect first discovered and studied by Comninellis and coworkers at Lausanne. 

It is apparent that, as in chemical systems, the magnitude of these effects will become useful and interesting from a practical viewpoint only when the pressure is increased above one kilobar. Thus for a typical electron transfer reaction with JF"=—20 cm mole , AE will be 211 mV when the pressme is ten kilobars. This shift could be important in the not uncommon situation where, at atmospheric pressure, the oxidation of a neutral substrate occurs at around the same potential as the anion of the base electrolyte. An increase in the pressure to ten kilobars will result in a separation of the processes... 

From the practical viewpoint it is important to be able to distinguish infants and children with this condition from less benign disorders such as the spinal muscular atrophies. Careful histochemical assessment of muscle biopsies with histographic analysis is recommended. Most biopsies from CFTD patients show type 1 fibers which are small in relation to type 2 fibers. A revised definition of CFTD states that... 

All of the reactions discussed up till now involve the autoxidation of methylbenzenes to the corresponding carboxylic acids. From a practical viewpoint it would also be interesting to devise a process for the production of the corresponding aldehyde. Unfortunately, as noted earlier, the oxidizability of ArCHO is about four orders of magnitude higher than ArCH3 which essentially precludes the selective production of the aldehyde when O2 is the oxidant. With all other oxidants, on the other hand, the rate of oxidation of ArCHO is lower than that of ArCH3 (ref. 24) (Fig. 21). 

Reaction rates almost always increase with temperature. Thus, the best temperature for a single, irreversible reaction, whether elementary or complex, is the highest possible temperature. Practical reactor designs must consider limitations of materials of construction and economic tradeoffs between heating costs and yield, but there is no optimal temperature from a strictly kinetic viewpoint. Of course, at sufficiently high temperatures, a competitive reaction or reversibility will emerge. 

The central difficulty in applying Equations (11.42) and (11.43) is the usual one of estimating parameters. Order-of-magnitude values for the liquid holdup and kiA are given for packed beds in Table 11.3. Empirical correlations are unusually difficult for trickle beds. Vaporization of the liquid phase is common. From a formal viewpoint, this effect can be accounted for through the mass transfer term in Equation (11.42) and (11.43). In practice, results are specific to a particular chemical system and operating mode. Most models are proprietary. 

To date, many theories and models have been proposed by various researchers, such as Atobiloye and Britter [14], Ashurust [15], Asato et al. [16], and Umemura [17,18]. Numerical simulations have also been conducted by Hasegawa and coworkers [19,20]. Recently, the phenomenon of rapid flame propagation has received keen interest from a practical viewpoint, to realize a new engine operated at increased compression ratios, far from the knock limit [21]. 

We should not minimize the effects that electronic searching of patents has had on the business of research. In 1990, CAS introduced MARPAT, which is a database of Markush (generic) structures found in patent documents [1]. This database provided a valuable tool for patent searching in a more comprehensive way than had been available previously. In 1995, CAS launched SciFinder, which provided access to the patent literature for chemists on their desktops. Using the SciFinder interface, one may search for research topics, authors, companies, or structures/reactions. From a practical viewpoint, SciFinder did more to enhance the searching capabilities of the medicinal chemist than any other tool. Even today, SciFinder continues to provide a first pass through the patent literature when chemists want to include patents in their searching. Indeed, when a search is performed, patent references are included in the answer set. Only very recently have there been additional tools to search the patent literature that have found widespread use. 

Electrolytic conductivity has also been measured in many binary systems. " Although data on conductivities in binary mixtures are very useful for practical purposes, the information from such data alone is limited from the viewpoint of elucidation of the mechanism. For example, the empirical Markov rule is well known for the electrical conductivity of binary mixtures. However, many examples have been presented where this rule does not hold well. 

It is important from a practical viewpoint to predict the shear viscosity of mixtures from those of pure melts. For alkali nitrate melts, a linear dependence has been found between the reorientational line width obtained by Raman measurements and the ratio of temperature divided by shear viscosity.For NO3 ions, the depolarized Raman scattering from 1050cm" total stretching vibrational mode (Al) has a contribution to the line width L, which is caused by the reorientational relaxation time of the Csv axis of this ion. The Stokes-Einstein-Debye(SED) relation establishes a relation between the shear viscosity r of a melt and the relaxation time for the reorientation of a particle immersed in it ... 

GP 11] [R 19] The third explosion limit is discussed in detail in [9] as it is important from both practical and mechanistic viewpoints (230-950 °C 10-10 Pa). This limit is normally responsible for the occurrence of explosions imder ambient pressure conditions. In addition, these explosions are known to be kinetically induced by radical formation. The formation of these species is sensitive to size reduction of the processing volume owing to the impact of the wall specific surface area on radical chain termination. It turns out that the wall temperature has a noticeable, but not decisive influence on the position of the third limit The thermal explosion limit lies below the kinetic limit for all conditions specified above (Figure 3.50) [9]. 

---