bluuebunny/crossref_metadata_2025 huggingface dataset:
Solving for the Equilibrium State
Authors: Bethke Craig M.
Published: November 2020

In Chapter 3, we developed equations that govern the equilibrium state of an aqueous fluid and coexisting minerals. The principal unknowns in these equations are the mass of water nw, the concentrations mi of the basis species, and the mole numbers nk of the minerals. If the governing equations were linear in these unknowns, we could solve them directly using linear algebra. However, some of the unknowns in these equations appear raised to exponents and multiplied by each other, so the equations are nonlinear. Chemists have devised a number of numerical methods to solve such equations (e.g., van Zeggeren and Storey, 1970; Smith and Missen, 1982). All the techniques are iterative and, except for the simplest chemical systems, require a computer. The methods include optimization by steepest descent (White et al., 1958; Boynton, 1960) and gradient descent (White, 1967), back substitution (Kharaka and Barnes, 1973; Truesdell and Jones, 1974), and progressive narrowing of the range of the values allowed for each variable (the monotone sequence method; Wolery and Walters, 1975). Geochemists, however, seem to have reached a consensus (e.g., Karpov and Kaz’min, 1972; Morel and Morgan, 1972; Crerar, 1975; Reed, 1982; Wolery, 1983) that Newton-Raphson iteration is the most powerful and reliable approach, especially in systems where mass is distributed over minerals as well as dissolved species. In this chapter, we consider the special difficulties posed by the nonlinear forms of the governing equations and discuss how the Newton-Raphson method can be used in geochemical modeling to solve the equations rapidly and reliably. The governing equations are composed of two parts: mass balance equations that require mass to be conserved, and mass action equations that prescribe chemical equilibrium among species and minerals.
Equilibrium Models of Natural Waters
Authors: Bethke Craig M.
Published: November 2020

Having derived a set of equations describing the equilibrium state of a multicomponent system and devised a scheme for solving them, we can begin to model the chemistries of natural waters. In this chapter we construct four models, each posing special challenges, and look in detail at the meaning of the calculation results. In each case, we use program REACT and employ an extended form of the Debye-Hückel equation for calculating species' activity coefficients, as discussed in Chapter 7. In running REACT, you work interactively following the general procedure: • Swap into the basis any needed species, minerals, or gases. Table 6.1 shows the basis in its original configuration (as it exists when you start the program). You might want to change the basis by replacing SiO2(aq) with quartz so that equilibrium with this mineral can be used to constrain the model. Or to set a fugacity buffer you might swap CO2(g) for either H+ or HCO-3. • Set a constraint for each basis member that you want to include in the calculation. For instance, the constraint might be the total concentration of sodium in the fluid, the free mass of a mineral, or the fugacity of a gas. You may also set temperature (25°C, by default) or special program options. • Run the program by typing go. • Revise the basis or constraints and reexecute the program as often as you wish. In this book, input scripts for running the various programs are set in a "typewriter" typeface. Unless a script is marked as a continuation of the previous script, you should start the program anew or type reset to clear your previous configuration. For a first chemical model, we calculate the distribution of species in surface seawater, a problem first undertaken by Garrels and Thompson (1962; see also Thompson, 1992). We base our calculation on the major element composition of seawater (Table 6.2), as determined by chemical analysis. To set pH, we assume equilibrium with CO2 in the atmosphere (Table 6.3).
Surface Complexation
Authors: Bethke Craig M.
Published: November 2020

An important consideration in constructing certain types of geochemical models, especially those applied to environmental problems, is to account for the sorption of ions from solution onto mineral surfaces. Metal oxides and aluminosilicate minerals, as well as other phases, can sorb electrolytes strongly because of their high reactivities and large surface areas (e.g., Davis and Kent, 1990). When a fluid comes in contact with minerals such as iron or aluminum oxides and zeolites, sorption may significantly diminish the mobility of dissolved components in solution, especially those present in minor amounts. Sorption, for example, may retard the spread of radionuclides near a radioactive waste repository or the migration of contaminants away from a polluting landfill. In acid mine drainages, ferric oxide sorbs heavy metals from surface water, helping limit their downstream movement (see Chapter 23). A geochemical model useful in investigating such cases must provide an accurate assessment of the effects of surface reactions. Many of the sorption theories now in use are too simplistic to be incorporated into a geochemical model intended for general use. To be useful in modeling electrolyte sorption, a theory must account for the electrical charge on the mineral surface and provide for mass balance on the sorbing sites. In addition, an internally consistent and sufficiently broad database of sorption reactions must accompany the theory. The Freundlich and Langmuir theories, which use distribution coefficients Kd to set the ratios of sorbed to dissolved ions, are applied widely in groundwater studies (Domenico and Schwartz, 1990) and used with considerable success to describe sorption of uncharged organic molecules (Adamson, 1976). The models, however, do not account for the electrical state of the surface, which varies sharply with pH, ionic strength, and solution composition. Freundlich theory prescribes no concept of mass balance, so that a surface might be predicted to sorb from solution without limit. Both theories require that distribution coefficients be determined experimentally for individual fluid and rock compositions, and hence both theories lack generality. Ion exchange theory (Stumm and Morgan, 1981; Sposito, 1989) suffers from similar limitations. Surface complexation models, on the other hand, account explicitly for the electrical state of the sorbing surface (e.g., Adamson, 1976; Stumm, 1992).
Waste Injection Wells
Authors: Bethke Craig M.
Published: November 2020

Increasingly since the 1930s, various industries around the world that generate large volumes of liquid byproducts have disposed of their wastes by injecting them into the subsurface of sedimentary basins. In the United States, according to a 1985 survey by Brower et al. (1989), 411 “Class I” wells were licensed to inject hazardous and nonhazardous waste into deep strata, and 48 more were proposed or under construction. Legal restrictions on the practice vary geographically, as does the suitability of geologic conditions. Nonetheless, the practice of deep-well injection had increased over time, partly in response to environmental laws that emphasize protection of surface water and shallow groundwater. More restrictive regulations introduced in the late 1980s and 1990s have begun to cause a decrease in the number of operating Class I wells. Some injected wastes are persistent health hazards that need to be isolated from the biosphere indefinitely. For this reason, and because of the environmental and operational problems posed by loss of permeability or formation caving, well operators seek to avoid deterioration of the formation accepting the wastes and its confining layers. When wastes are injected, they are commonly far from chemical equilibrium with the minerals in the formation and, therefore, can be expected to react extensively with them (Boulding, 1990). The potential for subsurface damage by chemical reaction, nonetheless, has seldom been considered in the design of injection wells. According to Brower et al. (1989; Fig. 21.1), nine wells at seven industrial sites throughout the state of Illinois were in use in the late 1980s for injecting industrial wastes into deeply buried formations; these wells accepted about 300 million gallons of liquid wastes per year. In this chapter, we look at difficulties stemming from reaction between waste water and rocks of the host formation at several of these wells and consider how geochemical modeling might be used to help predict deterioration and prevent blowouts. Velsicol Chemical Corporation maintained two injection wells at its plant near Marshall, Illinois, to dispose of caustic wastes from pesticide production, as well as contaminated surface runoff. In September 1965, the company began to inject the wastes into Devonian dolomites of the Grand Tower Formation at a depth of about 2600 feet.
The Role of Process In Integrated CASE Environments
Authors: Brown Alan W. , Carney David J. , Morris Edwin J. , Smith Dennis B. , Zarrella Paul F.
Published: November 2020

Early work on CASE environment integration concentrated on the mechanistic aspects of integration between tools. The process context in which those integrated tools would be used was less of a concern. In recent years, however, the process aspect of integration has grown in importance in the eyes of most members of the software community. The role of process, and hence of process integration, is now generally regarded as critical. Such issues as determining the impact of process on the choice of tools to be integrated, how those integrations should be implemented, and how a CASE environment will be used in the overall life of an enterprise are now increasingly seen as being of paramount importance. As an example, while one could assert that a particular analysis tool should be integrated with a documentation tool, this is of little real value. A more meaningful assertion is that the analysis tool must make use of documentation services to generate documentation in some standard life-cycle model form (e.g., DoD-STD-2167 document sets). The three-level model of integration proposed in this book reflects this interest in process. In our three-level model, process integration is orthogonal to mechanism- level integration and service-level integration. In this view, we see that integration is not just an amalgamation of related tools, but is the combination of several integrating mechanisms, used over some set of services (as implemented by tools) to achieve some specific process objective. Put another way, we view software processes as defining a design context, i.e., a set of integration requirements. When implemented, they can be expressed as a coordinated set of environment services, i.e., unified through a combination of control, data, and presentation mechanisms. In this chapter, we explore the broad subject of process integration in more detail. We first consider several divergent views on the nature of process integration itself, and particularly the question of process in the context of “process improvement.” We then examine the relationships between process integration and CASE tools and environments. We next look at some idealized examples of how processes and tools interact, and some issues raised by these examples.
CASE Environments in Practice
Authors: Brown Alan W. , Carney David J. , Morris Edwin J. , Smith Dennis B. , Zarrella Paul F.
Published: November 2020

While there have been automated tools to support software engineers from the earliest days of computer programming, it was the concept of an IPSE developed in the late 1970s and early 1980s that directly focused attention on the central role played by integration in a support environment. The Stoneman report [16] defining the architecture of an Ada programming support environment (APSE) has proven to be a seminal work on environments, influencing a range of research and activities that have attempted to develop an integrated environment supporting all aspects of software development. However, in the 15 years since the Stoneman report, it can be argued that no commercially successful full life-cycle CASE environment has been developed. There are many reasons for this lack of success. Perhaps the most obvious is that CASE environment technology has proven to be far more complex than initially anticipated. Additional reasons may include the rapid technological changes in workstations, client-server technology, open systems, and rapid growth in the numbers of commercial CASE tools and integration technology. As discussed in earlier chapters, these trends have led to a more recent movement away from efforts to develop full life-cycle CASE environments from scratch toward efforts to build limited collections of CASE tool solutions from combinations of commercially available tools and integrating frameworks. It is instructive to evaluate the progress made during the 1980s and to reflect on likely directions as we head toward the year 2000. Among the questions we can ask are: • How much progress has been made since Stoneman? • What lessons have we learned about good and bad approaches to the development of CASE environments? • What do we see as the key issues for the future? Two important data points for answering these questions are the historical record and current state of previous CASE environment efforts. To gather data, we completed two studies of experts involved in building and/or using such environments. The results of these studies are the basis for this chapter.
Fields
Authors: Oertel Gerhard
Published: November 2020

A scalar determined at every point in a given domain, analytically or otherwise, constitutes a scalar field. Vectors similarly determined constitute a vector field. The defining analytical expressions of a three-dimensional field are commonly differentiable with respect to space; hence in a cartesian coordinate system they are amenable to partial differentiation with respect to x1, x2, and x3. In this context it is useful to define several differential operators. The operator ∇ is called the “del” or the “nabla” and is defined as follows: . . . ∇ ≡ i 𝜕/𝜕x1+j 𝜕/𝜕x2+k 𝜕/𝜕x3, (2.1) . . . or: . . . (∇)i ≡ 𝜕/𝜕xi. (2.2) . . . It can be seen that the del is a vector. By convention, however, it is not rendered in boldface. Before we define additional differential operators, we extend the subscript notation further and let a subscribed comma indicate partial differentiation. A comma preceding a letter subscript, say i, is taken to imply differentiation with respect to xi. Thus, if φ (xi) is a scalar function of position and thus defines a scalar field, its gradient, another differential operator, is defined by the equation: . . . (grad φ)i ≡ φ,i≡ 𝜕 φ/𝜕xi. (2.3) . . . Thus the gradient of a scalar is a vector.
Infinitesimal Strain
Authors: Oertel Gerhard
Published: November 2020

An elastic material responds to a stress by a change of volume and shape, or strain, which stays constant as long as the stress is maintained. Materials for which strains are completely reversible and proportional to the stresses that cause them are called ideally elastic and are said to follow Hooke’s law. Many actual materials are nearly ideally elastic as long as the stress-induced strains are small. Strain in such materials is the usual means of observing stress, which itself is an abstraction and not directly observable. Strain, as treated in continuum mechanics, is also an abstraction, but one that more closely approaches observable reality. The element of abstraction comes from treating the deformed body as a continuum, with the implication that neighboring material points in an undeformed body remain arbitrarily close neighbors after deformation. Let one point on a stretchable material line (imagine a rubber band) be held in place at the origin of a one-dimensional coordinate system and stretched, throughout but not necessarily uniformly (the rubber band may vary in thickness), by pulling on its free end with the position Δ x. Let the end, as a consequence of the stretching, be moved by the displacement Δ u. Then any original length element Δ x of the line will be changed to a new length Δx+Δu, say, the particular segment starting at the points P before and P′ after the deformation.
Policy and Practical Considerations in Land-Use Strategies for Biodiversity Conservation
Authors: Brandon Katrina
Published: November 2020

Much attention has been given to the issues of sustainable use, sustainable development, and biodiversity conservation, as well as to the relationships among them. Some observers express a sense of optimism that implementing sustainable activities worldwide will lead to the conservation of biodiversity. In the popular media, there are examples almost daily of conservation success stories. But publicity for conservation and attention on biodiversity are being mistaken for solutions. What is perhaps more sobering than equating publicity with actions, or actions with solutions, is that the entire rubric of sustainability, in the rural context, has a set of questionable assumptions that underlies the portfolio of activities being implemented to conserve biodiversity. These assumptions have had a major impact in shaping the range of activities that have been developed to address the conservation of biodiversity— from policies (such as the Biodiversity Convention adopted at the 1992 Earth Summit) to projects implemented by conservation and development organizations worldwide (such as the Global Environmental Facility). The questionable assumptions fit into the following seven broad categories: • Method. Biodiversity conservation can best be accomplished through field-based activities, such as establishing parks and reserves. • Use. Sustainable use is possible under a variety of management regimes ranging from private to communal. Dependence on wildlands resources is most likely to ensure their long-term conservation. • Incentives. Appropriate sets of incentives can be readily defined and will influence people to conserve biodiversity. • Management. Management should be devolved to local control whenever possible. • Technology. Technical and organizational solutions exist to improve resource management and production activities in areas with great biodiversity. • Poverty Mitigation and Development. Rural poverty-mitigation and development strategies will lead to conservation and maintain biodiversity. • Social. Local people are cooperative and live in harmony with one another and with nature. These assumptions, and their implications, are increasingly being questioned as concern mounts that their implementation may lead to serious loss of biodiversity (see Ludwig et al., 1993; Robinson, 1993).
Biodiversity Politics and the Contest for Ownership of the World's Biota
Authors: Sanderson Steven E. , Redford Kent H.
Published: November 2020

In the course of the past decade, biodiversity has become one of the most important concepts guiding conservation and development at the global level. From the 1972 U.N. Conference on the Human Environment, held in Stockholm, to the 1992 U.N. Conference on Environment and Development, held in Rio de Janeiro, concern for biodiversity loss has spawned international treaties, national laws, and community conservation strategies. This concern for biodiversity, however, has not been clearly translated into increased conservation of biodiversity, for a variety of fundamental reasons. Biodiversity has traditionally been the domain of natural scientists and conservation activists. The first group has focused on the importance of biological diversity for scientific inquiry; the second group has concentrated on the impact of lost biological diversity on social and ecological systems, and has advocated policies to conserve the earth’s biota. Increasingly, both groups-and many other constituencies, from sport hunters and fishers to pharmaceutical companies—have fought out the battle over biodiversity in public arenas. The weapons have included national parks and protected areas, species and genetic conservation programs in the field and in other locations such as zoos, private nongovernmental organizations chartered for “‘genetic prospecting” activities, and integrated small-scale development programs that have a putative conservation side-benefit. Even as this battle continues, some agreement—if not a consensushas begun to emerge about biodiversity, which has provided a foundation for common cause among the various constituencies described above. Conservation has become use. The value of biodiversity has come to be determined according to economic criteria alone. Conservation and sustainable development, it is declared, not only can go together but are part of the same cloth. Ecological values and economic values are purported to be congruent. This position masks two disturbing realities that underpin the specific tasks of this chapter. The first reality is that the concerns that fostered the original concept of biodiversity have been surrendered—even forgotten—in the struggle for common ground, to the detriment of science and conservation. The second is that biodiversity and sustainability are far from scientific concepts.
Conservation in the Monteverde Zone: Contributions of Conservation Organizations
Authors: Burlingame Leslie j.
Published: November 2020

Monteverde is renowned among tropical biologists, conservationists, and ecotourists for its cloud forests, quetzals, and Golden Toads. These forest ecosystems have been preserved while many other rain forests in Latin America have been destroyed for agriculture, wood products, and development. Initially, the area was preserved because it was nearly inaccessible; it remains protected because of dedicated efforts by local inhabitants, the development of effective grassroots organizations, and funds and expertise from the international scientific and conservation communities. In this chapter I document the development and contributions of grassroots conservation organizations that promote conservation practices and thinking. Four organizations preserved forested areas that now constitute the Monteverde Reserve Complex (see Fig. 1.7): (a) Bosqueterno, a reserve and organization formed by the Quaker settlers to protect their watershed; (b) the Monteverde Cloud Forest Preserve (MCFP) managed by the San José-based Tropical Science Center (TSC); (c) Bosque Eterno de los Niños (Children’s Eternal Forest; BEN), whose land was acquired by the Monteverde Conservation League (MCL); and (d) the Santa Elena High School Cloud Forest Reserve (SER) established by the local high school (colegio). Other activities discussed in this chapter are efforts to (1) protect reserve areas, (2) protect forest fragments outside the reserves and create corridors to link forested areas, (3) reforest and rehabilitate damaged land, (4) develop environmental education at all levels, (5) develop complementarity and cooperation among organizations, and (6) establish projects in sustainable development. These topics are linked with the growth of scientific knowledge and the development of ecotourism in the zone. The thesis of this chapter is that conservation organizations emerged as a series of responses to newly perceived environmental needs and opportunities. I identify successes and failures of conservation efforts by organizations in the Monteverde Zone and the factors responsible for them, analyze problems that have been or need to be resolved, and determine the extent to which institutional developments in the Monteverde Zone may serve as models in conservation and sustainable development for other areas.
Waves and Patterns
Authors: Epstein Irving R. , Pojman John A.
Published: November 2020

In this chapter, we will examine how diffusion can interact with the sort of nonlinear reaction kinetics that we have discussed in previous chapters to generate propagating waves of chemical reactivity and structured, sometimes spectacular, spatial patterns. One might argue, particularly if one were a physicist rather than a chemist, that the oscillatory phenomena that we have discussed thus far, and even the chaotic behavior that we will treat a bit later, can be just as easily generated by nonlinear electrical circuits, and that those circuits are much easier to work with than wet, smelly, and often toxic, chemicals. However, as far as chemistry goes, “spatial is special” in the sense that the spatial phenomena that we will discuss in this chapter are most naturally and conveniently generated in chemical systems. These same patterns also occur in a number of biological systems; the resemblance between a structure that develops in an inorganic chemical reaction and one found in a living organism can be startling. We are inclined to think of diffusion as tending to make a system more homogeneous, with it acting to reduce and ultimately to obliterate local fluctuations in the concentration of a chemical species. The spontaneous appearance of concentration gradients might seem to violate the Great Law (i.e., the Second Law of Thermodynamics), since the free energy should be at a minimum or the entropy at a maximum when concentrations are uniform. However, as we have seen in the case of temporal oscillation, a system far from equilibrium can generate spontaneous transient spatial inhomogeneities and, in an open system, sustained spatial patterns as well. The most common kind of chemical wave is the single propagating front, where, in an unstirred medium, there is a relatively sharp boundary between reacted and unreacted material, and this boundary or wavefront moves through the solution at an essentially constant speed. These waves are, of course, most noticeable when the reaction involves a color change. Many autocatalytic reactions exhibit this phenomenon of traveling waves.
Introduction and Structure of the Book
Authors: Doraiswamy L. K.
Published: November 2020

A large part of the chemical industry is concerned with organic chemicals from simple to highly complex structures. In dealing with relatively simple structures, there does not appear to be any need usually for a deeper understanding of chemistry than that to which an engineer is normally exposed. Most reaction engineering texts are written with this basic assumption. Catalysis, which is invariably an integral part of the reaction engineer’s arsenal, has been limited to the production of large volume chemicals which are often relatively simple in structure. Increasing attempts by chemists today to extend the use of catalysis to the production of medium and small volume chemicals has triggered a change in perspective that augers well for a closer liaison between chemists and engineers. We examine this a little further below by defining an organic chemicals ladder, and the merging roles of the two in exploiting this ladder, particularly for chemicals stacked on its intermediate rungs. Another change that is taking place is the increasing role of process intensification, nowhere more evident than in the production of organic chemicals. Process intensification means improvement of a process, mainly the reaction, by any possible means, to increase the overall productivity. This usually takes the form of reaction rate enhancement by extending known or emerging laboratory techniques to industrial scale production. These techniques can be engineering intensive, chemistry intensive, or both. Examples are the use of ultrasound (sonochemistry), light (photochemistry), electrons (electrochemistry), enzymes (biotechnology), agents for facilitating a reaction between immiscible phases (phase-transfer catalysis), microparticles (microphase engineering), membranes (membrane reactor engineering), a second phase (biphasing), combinations of reactions with different techniques of separation (multifunctional or combo reactor engineering), and mixing. Their use in the production of medium and small volume chemicals like pesticides, drugs, Pharmaceuticals, perfumery chemicals, and other consumer products is being increasingly explored both by industry and academe. Some of these techniques have progressed little beyond the laboratory stage, although they have been a part of the synthetic organic chemist’s repertoire for a number of years. Thus, in addition to the use of catalysis in its various forms, this book will also explore different techniques of reaction rate and/or selectivity enhancement.
Homogeneous Catalysis
Authors: Doraiswamy L. K.
Published: November 2020

Catalysis by soluble complexes of transition metals is a rapidly gaining mode of catalysis in organic synthesis. These metals form bonds with one or more carbons in an organic reactant resulting in complexes that are known as organometallic complexes. Catalysis by these complexes is often referred to as homogeneous catalysis. Among the important applications of homogeneous catalysis in organic synthesis are isomerization of olefins; hydrogenation of olefins (carried out using Wilkinson type catalysts); oligomerization; hydroformylation of olefins to aldehydes with CO and H2 (the oxo process); carbonylation of unsaturated hydrocarbons and alcohols with CO (and coreactants such as water); oxidation of olefins to aldehydes, ketones, and alkenyl esters (Wacker process); and metathesis of olefins (a novel kind of disproportionation). Enantioselective catalysis that rivals enzymes in selectivity is a major development in homogeneous catalysis. As a result, many earlier processes in the pharmaceutical and perfumery industries are being replaced by more elegant syntheses using soluble catalysts in which “handedness” is introduced in the critical step of the process, thus avoiding the costly separation of racemic mixtures. In view of its importance in organic synthesis, enantioselective (or asymmetric) catalysis was briefly introduced in Chapter 6 and is again considered as a powerful synthetic tool in Chapter 9. This chapter is concerned with the use in general of homogeneous catalysis in organic synthesis (including asymmetric synthesis). Among the several books and reviews written on the subject, the following may be mentioned: Halpern (1975, 1982), Bau et al. (1978), Parshall (1980), Masters (1981), Collman and Hegedus (1980), Eby and Singleton (1983), Chaudhari (1984), Davidson (1984), Kegley and Pinhas (1986), Collman et al. (1987), Parshall and Nugent (1988), Noyori and Kitamura (1989), Parshall and Ittel (1992), Gates (1992), Chan (1993), Akutagawa (1995). Gas (or liquid)-phase reactions on solid catalysts are among the most common industrial reactions. However, homogeneous catalysis is rapidly catching up. Excluding applications in petroleum refining, the dollar value of organic chemicals produced worldwide by homogeneous catalysis (more than $35 billion) is quite impressive compared to that by heterogeneous catalysis (more than $45 billion). Attempts are now under way to find an integrated approach to homogeneous and heterogeneous catalyses (Moulijn et al., 1993).
Multiphase Reactions and Reactors
Authors: Doraiswamy L. K.
Published: November 2020

The first three chapters of this part dealt with two-phase reactions. Although catalysts are not generally present in these systems, they can be used in dissolved form in the liquid phase. This, however, does not increase the number of phases. On the other hand, there are innumerable instances of gas-liquid reactions in which the catalyst is present in solid form. A popular example of this is the slurry reactor so extensively employed in reactions such as hydrogenation and oxidation. There are also situations where the solid is a reactant or where a phasetransfer catalyst is immobilized on a solid support that gives rise to a third phase. A broad classification of three-phase reactions and reactors is presented in Table 17.1 (not all of which are considered here). This is not a complete classification, but it includes most of the important (and potentially important) types of reactions and reactors. The thrust of this chapter is on reactions and reactors involving a gas phase, a liquid phase, and a solid phase which can be either a catalyst (but not a phasetransfer catalyst) or a reactant, with greater emphasis on the former. The book by Ramachandran and Chaudhari (1983) on three-phase catalytic reactions is particularly valuable. Other books and reviews include those of Shah (1979), Chaudhari and Ramachandran (1980), Villermaux (1981), Shah et al. (1982), Hofmann (1983), Crine and L’Homme (1983), Doraiswamy and Sharma (1984), Tarmy et al. (1984), Shah and Deckwer (1985), Chaudhari and Shah (1986), Kohler (1986), Chaudhari et al. (1986), Hanika and Stanek (1986), Joshi et al. (1988), Concordia (1990), Mills et al. (1992), Beenackers and Van Swaaij (1993), and Mills and Chaudhari (1997). Doraiswamy and Sharma (1984) also present a discussion of gas-liquid-solid noncatalytic reactions in which the solid is a reactant. In Chapter 7 we saw how Langmuir-Hinshelwood-Hougen-Watson (LHHW) models are normally used to describe the kinetics of gas-solid (catalytic) or liquid-solid (catalytic) reactions, and in Chapters 14 to 16 we saw how mass transfer between gas and liquid phases can significantly alter the rates and regimes of these two-phase reactions.
Pressure-Tuning Spectroscopy of Proteins: Fourier Transform Infrared Studies in the Diamond Anvil Cell
Authors: Heremans Karel , Goossens Koen
Published: November 2020

The effect of hydrostatic pressure on the secondary structure of proteins can be followed by Fourier transform infrared (FTIR) spectroscopy in the diamond anvil cell. Pressure-induced changes in the amide I’ region of the deconvolved spectrum are used to follow the features of the secondary structure up to 20 kbar. The changes in the side chains such as tyrosine also can be followed. A self-deconvolution and fitting procedure is presented that allows the determination of both pressure-induced and temperature-induced changes in the secondary structure of proteins. The method takes into account the elastic, as well as the possible conformational, effects on the spectral bands of the protein. Applications are presented on pressure-induced changes in several proteins. Attention is also given to the influence of inert cosolvents. The fundamental principles of the phase diagram of proteins are presented to clarify their importance for understanding the behavior of proteins under pressure at different temperatures. Our results show that the infrared technique explores unique aspects of the behavior of proteins under these extreme conditions. The study of the effects of pressure has received considerable attention in recent years (Balny et al., 1992; Silva & Weber, 1993). In general, low pressures induce reversible changes such as the dissociation of protein-protein complexes, the binding of ligands, and conformational changes. Pressures higher than about 5 kbar induce denaturation, which in most cases is irreversible. However, reports on a few proteins indicate that such high pressures may also cause reversible changes. One such protein is horse scrum albumin (Chen & Heremans, 1990). A molecular interpretation of these phenomenon is based on the fact that pressure mainly affects the volume of a system, thus damping the molecular fluctuations. Temperature effects are known to affect both the kinetic energy and the volume of the system. Early in this century, it was shown that one can cook an egg by subjecting it to high pressure (Bridgman, 1914). The appearance of the pressure-induced coagulum of egg white is quite different from the coagulum induced by temperature.
Pressure Effects on the Ligand-Binding Kinetics for Hemoproteins and Their Site-Directed Mutants
Authors: Morishima Isao
Published: November 2020

The effects of high pressure up to 1500 bar on the recombination kinetics of oxygen and carbon monoxide (CO) binding to human hemoglobin (intact and isolated chain forms), human myoglobin (and its mutants), and cytochrome P-450 were studied by the use of millisecond and nanosecond laser photolysis. The activation volumes for the binding of CO to the R- and T-quaternary states of hemoglobin (Hbs) were determined to be –9.0 and –31.7 ml, respectively. The characteristic pressure dependence of the activation volume was observed for the R-state Hb but not for the T-state Hb. More detailed studies were made with isolated α- and β-chains of human Hb. The kinetic data were analyzed on the basis of a simple three-species model, which assumes two elementary reaction processes of bond formation and steps of ligand migration. A pressure-dependent activation volume change from negative lo positive values in the bimolecular CO association reaction was observed for both chains. This is attributed to a change of the rate-limiting step from the bond-formation step to the ligandmigration step. High-pressure ligand-binding kinetics were also examined for site-specific mutants of human myoglobin in which some amino acid residues at the heme distal sites, such as Leu 29, Lys 45, Ala 66, and Thr 67, are substituted by others. The pressure dependence of the CO binding rate for the L29 mutants was unusual: a positive value was obtained unexpectedly for overall CO binding. Corresponding to this anomaly was an unusual geometry of the iron-bound CO, which was determined by IR and NMR spectroscopies. The effects of camphor and camphor analogues as substrates on the CO-binding kinetics for P-450cam were also studied under pressure. The positive activation volumes for CO binding were obtained for substrate-free and norcamphor- and adamantane-bound P-450, whereas other substrate analogue-bound P-450 complexes exhibited the negative activation volumes. All of the present high-pressure results are discussed in relation to (1) the dynamic aspects of the protein conformation, and (2) the specific participation of amino acid residues in the heme distal site in each elementary step of the ligand-binding reaction process.
Transient Enzyme Kinetics at High Pressure
Authors: Balny Claude
Published: November 2020

In a detailed study of an enzyme reaction pathway, a measured composite rate constant, for example, kcat, can be interpreted in ways that lead to ambiguous conclusions. Two conditions must be met to solve this problem: (1) an elementary rate constant must be measured, and (2) a maximum number of physical-chemical parameters must be used to perturb the system under study. To gain access to elementary rate constants, cryobaroenzymology and/or transient methods, such as stopped-flow and flow-quench kinetics, can be used. Both perturbation and kinetics measurements performed under either high pressure or low temperatures can then be used to probe the thermodynamics of the interconversion of two successive intermediates to obtain parameters such as ΔG‡, ΔS‡, ΔH‡, and ΔV‡ The interdependence of the two major variables, namely temperature and pressure, is presented in this article, in which the role of organic cosolvents is considered as a third variable. During catalytic reactions, enzymes undergo a number of conformational changes related to their dynamic structural flexibility. This appears as a succession of different steps. A complete study of such processes, which generally are very rapid, consists of the exploration of the properties of these steps, including thermodynamic features obtained by the action of temperature and pressure. As long ago as 1950, Laidler (1950) formulated the first theoretical basis for explaining the responses of enzymes to high hydrostatic pressures. Chemists used this parameter extensively, and in the early stages of high-pressure kinetics they attempted to analyze the observed results on the basis of collision theory (Asano, 1991) or transition-state theory (Evans & Polanyi, 1935). These theories are still used to describe pressure effects on enzyme reactions. It is postulated that between two successive intermediates there is a labile transition state which governs the energetics of the reaction (Glastone et al., 1941). But we must remember that this theory was first applied only to simple homogeneous reactions in gases. For solutions, the treatment can require the introduction of other parameters such as the viscosity.
Electrostatic Adsorption of Cations
Authors: Ji G. L. , Li H. Y.
Published: November 2020

Adsorption of ions is a direct consequence of the carrying of surface charge for soils. Owing to the characteristics of variable charge soils in chemical and mineralogical compositions, these soils possess distinct amphoteric properties. Therefore, they can adsorb cations as well as anions. Under field conditions, most of the variable charge soils carry more negative surface charge than positive surface charge, hence they adsorb more cations than anions. Under certain conditions the quantities of adsorbed cations and anions are equal to each other. In this case the soil is said to be at its iso-ionic point. Generally, for most cations commonly found in soils, the interaction force between them and the surface of soil particles during adsorption is electrostatic in nature. However, owing to the characteristics of variable charge soils, a specific force may also be involved in the adsorption of some cations. This latter topic shall be discussed in Chapter 5. In this chapter, only electrostatic adsorption is dealt with. In the present chapter, the mechanism of electrostatic adsorption of cations by variable charge soils and the factors that may affect this type of adsorption are presented first. Then, the dissociation of adsorbed cations is discussed. Finally, the competitive adsorptions of potassium ions with sodium ions and of potassium ions with calcium ions are examined. According to the definition in physical chemistry, the concentration of solute in the surface layer of the solution is different from that in the interior of the bulk solution. If the concentration of solute in the surface layer is higher than that in the interior, the phenomenon is called adsorption. Conversely, it is called negative adsorption. In soil science, on the other hand, the heterogeneity in distribution of ions in soil colloidal systems is interpreted mainly in terms of electrostatic interactions occurring at the interface between soil colloidal particles and the liquid phase (Bear, 1964). Owing to adsorption or negative adsorption, the concentration of ions at the surface of soil colloidal particles or adjacent to the surface is higher or lower than that in the diffuse layer or the free solution.
Oxidation-Reduction Reactions
Authors: Liu Z. G. , Ding C. P.
Published: November 2020

Oxidation-reduction reactions are chemical reactions caused by the transfer of electrons between two substances. These reactions occur actively in variable charge soils. This is because that under conditions of high temperature and high precipitation both the accumulation and the decomposition of organic matter proceed rapidly. The decomposition products of organic matter may release electrons, providing the necessary condition for the occurrence of reduction reactions. In particular, because the soil may have a high content of water during seasonal rainy periods, the presence of a strongly reducing condition is possible. Furthermore, large areas of variable charge soils have been cultivated for rice production. For these paddy soils there are always intensive oxidation-reduction reactions proceeding alternately. Variable charge soils have a high content of iron oxides. The content of manganese is also higher than that of constant charge soils. Thus, the soil itself possesses plenty of electron-acceptors. Besides, the high concentration of hydrogen ions in variable charge soils is favorable for the occurrence of reduction reactions. Therefore, as shall be seen in this chapter, contrary to the belief that the significance of oxidation- reduction reactions is confined chiefly to submerged soils, these reactions may play an important role in soil genesis and soil fertility for variable charge soils even under well-aerated conditions. In this chapter, after discussions on factors affecting the intensity of oxidation-reduction and interactions among various oxidation-reduction substances, the oxidation-reduction regimes of variable charge soils under different utilization conditions will be presented. Ferrous and manganous ions, two important inorganic reducing substances in soils, shall be dealt with in the next chapter. The oxidation-reduction intensity of a substance is determined by its ability to liberate or accept electrons. Therefore, electron activity in an equilibrium system may be used as an index for expressing its reduction strength. An electron has a radius of only approximately 1/20,000 of that of a hydrogen atom. Its large charge-to-size ratio prevents it from persisting in free form in aqueous systems. The ephemeral “hydrated electron” has a half-life of less than 1 msec (Bartlett and James, 1993). As a species with a potential of -2.7 V vs. the standard potential of H+/H2, it is a powerful reducing agent.
Proton and 19F NMR Spectroscopy of Pesticide Intermolecular Interactions
Authors: Anderson Sharon J.
Published: November 2020

Sorption of organic pollutants by soils and sediments is one of the main chemical processes that controls pollutant migration in the environment. Information about the molecular mechanisms by which an organic pollutant interacts with other solution-phase constituents and with solid-phase sorbents would be invaluable for more accurate prediction of pollutant fate and transport and for optimal design and application of remediation procedures. Many current models and remediation strategies are based upon the “partition theory” of organic compound sorption, which predicts sorption coefficients from properties such as water solubility or octanol-water partition coefficients. Partition theory is well suited for nonpolar hydrocarbons but may not be appropriate for pesticides with electrophilic or weakly acidic or basic substituents, which may interact with soils or organic matter through specific interactions such as hydrogen bonding or charge-transfer complexes. If a pesticide can form hydrogen bonds or a charge-transfer complex with a sorbent, sorption may be greater than in the absence of specific interactions. Nuclear magnetic resonance (NMR) spectroscopy is well suited for the study of pesticide-solution or pesticide-sorbent interactions because NMR is an element-specific method that is extremely sensitive to the electron density (shielding) near the nucleus of interest. Consequently, solution-state NMR can distinguish between closely related functional groups and can provide information about intermolecular interactions. All nuclei with nonzero nuclear spin quantum number can be studied by NMR spectroscopy. Of the more than 100 NMR-active nuclei, 1H and 19F are the easiest to study because both have natural abundances near 100% and greater NMR sensitivity than any other nuclei. In addition, both 1H and 19F have zero quadrupolar moments, which means that sharp, well resolved NMR peaks can be obtained, at least in homogeneous solutions. Proton NMR is well suited for elucidating molecular interactions in solution but cannot be used to study interactions between pesticides and heterogeneous sorbents such as soils, humic acid, or even cell extracts, since protons in the sorbent generally produce broad peaks that mask the NMR peaks from the solute or sorbate of interest. In contrast, 19F NMR can be used to study interactions between fluorine-containing molecules and heterogeneous sorbents because the fluorine concentration in most natural sorbents is negligible.