bluuebunny/crossref_metadata_2025 huggingface dataset:
Nature and Cyber space
Authors: Heim Michael
Published: November 2020

In March 1993 at the SCI-ARC School of Architecture in Los Angeles, a student posed a question to Jaron Lanier, the famous entrepreneur or Virtual Reality. “How,” the student asked, “will VR enhance architecture.” The stocky genius smiled, ran a hand through dangling dreadlocks, and responded enthusiastically: “VR allows us to embellish computer-generated buildings with wonderful enhancements. Users can decorate electronic environments with dazzling colors and sign them with fun designs.” Lanier went on to say that the physical dwellings of the future would probably be cheap, dull, unadorned shelters generated by robot factories to put no-frills roofs over the heads of an overpopulated humanity. To compensate for the squalid physical surroundings, VR would provide habitations for interactive personal expression and aesthetic enjoyment. Lanier described a future in which cyberspace offers solace for the loss of natural, livable, environmental space. Lanier’s provocative mix of enthusiasm and pessimism supports many critics who attack cyberspace as a fatal form of escape. Chapter 2 showed us some of the critics who stand on the ground of naive realism. For them, virtual identities diminish physical identities. If we look, in fact, more closely at the naïve realists, we find an anxiety about the physical ground on which they stand. The firm ground the critics feel themselves standing on actually covers an underlying sinkhole. The nature to which the critics appeal has in recent years been threatened. A large cavity gapes in the human attachment to nature. Naïve realists want to protect reality from cyberspace, but they are not so sure about how deeply we are still attached to nature. Virtual reality seems to wean us from spontaneous affection toward mother nature where our birthright seems to shrink more every day. Is VR a consolation for the lost charms of natural things? Isn’t such a cyberspace a grand delusion, an electronic Tower of Babel? Is virtual reality an escapist opium for blocking the pain of planetary loss? Many of the metaphors we use today for computers suggest escapism. The “net” and the “web” are metaphors. We can be caught by these metaphors if we’re not careful.
Situation-Theoretic Account of Valid Reasoning with Venn Diagrams
Authors: Shin Sun-Joo
Published: November 2020

Venn diagrams are widely used to solve problems in set theory and to test the validity of syllogisms in logic. Since elementary school we have been taught how to draw Venn diagrams for a problem, how to manipulate them, how to interpret the resulting diagrams, and so on. However, it is a fact that Venn diagrams are not considered valid proofs, but heuristic tools for finding valid formal proofs. This is just a reflection of a general prejudice against visualization which resides in the mathematical tradition. With this bias for linguistic representation systems, little attempt has been made to analyze any nonlinguistic representation system despite the fact that many forms of visualization are used to help our reasoning. The purpose of this chapter is to give a semantic analysis for a visual representation system—the Venn diagram representation system. We were mainly motivated to undertake this project by the discussion of multiple forms of representation presented in Chapter I More specifically, we will clarify the following passage in that chapter, by presenting Venn diagrams as a formal system of representations equipped with its own syntax and semantics:. . . As the preceding demonstration illustrated, Venn diagrams provide us with a formalism that consists of a standardized system of representations, together with rules of manipulating them. . . . We think it should be possible to give an informationtheoretic analysis of this system, . . . . In the following, the formal system of Venn diagrams is named VENN. The analysis of VENN will lead to interesting issues which have their ana logues in other deductive systems. An interesting point is that VENN, whose primitive objects are diagrammatic, not linguistic, casts these issues in a different light from linguistic representation systems. Accordingly, this VENN system helps us to realize what we take for granted in other more familiar deductive systems. Through comparison with symbolic logic, we hope the presentation of VENN contributes some support to the idea that valid reasoning should be thought of in terms of manipulation of information, not just in terms of manipulation of linguistic symbols.
Toward The Rigorous Use Of Diagrams In Reasoning About Hardware
Authors: Johnson Steven D. , Barwise Jon
Published: November 2020

The logician’s conventional notion of proof has grown increasingly anachronistic through the twentieth century as computing capabilities have advanced. classical proof theory provides a partial model of actual mathematical reasoning. when we move away from mathematics toward reasoning in engineering and computation, its limitations are even more pronounced. the standard idea of a formal system seems frozen in the information technology of frege’s time; it is decidedly quaint in the presence of today’s desk-top computer. contrary to formalists’ dogma, experience suggests that pictures, diagrams, charts, and graphs are important tools in human reasoning, not mere illustrations as traditional logic would have us believe. nor is the computer merely an optimized turing machine. the computer’s graphical capabilities have advanced to the point that diagrams can be manipulated in sophisticated ways, and it is time to exploit this capability in the analysis of reasoning, and in the design of new reasoning aids. in this chapter, we propose a new understanding of the role of various sorts of diagrams in the specification and design of computational hardware. this proposal stems from a larger project, initiated by barwise and etchemendy [1991a], the goals of which are to develop a mathematical basis from which to understand the substantive logical relationships between diagrams and sentences, and to develop a new generation of automated reasoning tools from that basis. microelectronic cad systems are among the supreme examples of visualized reasoning environments. their tools are highly oriented toward diagrams, are quite sophisticated, and are comparatively well integrated. these systems also integrate logical and physical design, providing a strong coherence between specification and implementation views. formalized reasoning meshes poorly with these working frameworks. although it provides needed rigor for today’s highly complex design challenges, its preoccupation with formulas at the expense of diagrams is simply too cumbersome. we should attempt to draw lessons from these advanced design environments, making the reasoning rigorous without subverting their character. this chapter is built around a simple design example, a synchronizing circuit. our purposes are, first, to illustrate heterogeneous use of pictoral “formalisms” in design, and second, to expose basic questions for the logical analysis that follows. we will develop a mathematical basis in which the example can be analyzed. these are admittedly modest beginnings, but we hope that they start to put to rest the idea that only formulas can be used in formal reasoning about hardware.
Introduction
Authors: Koch Christof
Published: November 2020

The brain computes! This is accepted as a truism by the majority of neuroscientists engaged in discovering the principles employed in the design and operation of nervous systems. What is meant here is that any brain takes the incoming sensory data, encodes them into various biophysical variables, such as the membrane potential or neuronal firing rates, and subsequently performs a very large number of ill-specified operations, frequently termed computations, on these variables to extract relevant features from the input. The outcome of some of these computations can be stored for later access and will, ultimately, control the motor output of the animal in appropriate ways. The present book is dedicated to understanding in detail the biophysical mechanisms responsible for these computations. Its scope is the type of information processing underlying perception and motor control, occurring at the millisecond to fraction of a second time scale. When you look at a pair of stereo images trying to fuse them into a binocular percept, your brain is busily computing away trying to find the “best” solution. What are the computational primitives at the neuronal and subneuronal levels underlying this impressive performance, unmatched by any machine? Naively put and using the language of the electronic circuit designer, the book asks: “What are the diodes and the transistors of the brain?” and “What sort of operations do these elementary circuit elements implement?” Contrary to received opinion, nerve cells are considerably more complex than suggested by work in the neural network community. Like morons, they are reduced to computing nothing but a thresholded sum of their inputs. We know, for instance, that individual nerve cells in the locust perform an operation akin to a multiplication. Given synapses, ionic channels, and membranes, how is this actually carried out? How do neurons integrate, delay, or change their output gain? What are the relevant variables that carry information? The membrane potential? The concentration of intracellular Ca2+ ions? What is their temporal resolution? And how large is the variability of these signals that determines how accurately they can encode information? And what variables are used to store the intermediate results of these computations? And where does long-term memory reside? Natural philosophers and scientists in the western world have always compared the brain to the most advanced technology of the day.
Earth: Imprint of Life
Authors: Yung Yuk L. , DeMore William B.
Published: November 2020

Earth is the largest of the four terrestrial planets, three of which have substantial atmospheres. The astronomical and orbital parameters are summarized in table 9.1. Our planet has an obliquity of 23.5°, giving rise to well-known seasonal variations in solar insolation. The orbital elements are slightly perturbed by other planets in the solar system (primarily Jupiter), with time scales from 20 to 100 kyr, and these changes are believed to cause the advance and retreat of ice sheets. The last glacial maximum (LGM) occurred 18 kyr ago, at which time the planet was colder by several degrees centigrade on average. At present Earth is in an interglacial warm period. The origin of Earth may not be very different from that of the other terrestrial bodies. However, three properties may be unique to this planet. One is the formation of the Moon, probably via collision between Earth and a Mars-sized body. Second is the release of a huge amount of water from the interior (see discussion in section 8.5). Third, Earth is endowed with a large magnetic field that protects it from direct impact by the solar wind. Seventy percent of Earth's surface is covered by oceans, which have a mean depth of 3 km. There is so much water that Arthur C. Clarke proposed that "Ocean" might be a better name for our planet than "Earth." The enormous body of water became the cradle of life as early as 3.85 Gyr ago. The present terrestrial environment is the end-product of billions of years of evolution driven by the hydrological cycle and global biogeochemical cycles, in addition to the slower forces of geodynamics and geochemistry. The massive hydrological cycle and the biogeochemical cycles that operate on Earth are absent from other planets in the solar system. Mars in the remote past might have had a milder climate with liquid water on the surface, but the planet dried up a few eons ago. There is to date no observational evidence for the hypothetical oceans (composed of liquid hydrocarbons) on Titan. Life on a planetary scale equivalent to the terrestrial biosphere does not exist elsewhere in the solar system.
Modeling Of Turbulent Transport Equations
Authors: Speziale Charles G.
Published: November 2020

The high-Reynolds-number turbulent flows of technological importance contain such a wide range of excited length and time scales that the application of direct or large-eddy simulations is all but impossible for the foreseeable future. Reynolds stress models remain the only viable means for the solution of these complex turbulent flows. It is widely believed that Reynolds stress models are completely ad hoc, having no formal connection with solutions of the full Navier-Stokes equations for turbulent flows. While this belief is largely warranted for the older eddy viscosity models of turbulence, it constitutes a far too pessimistic assessment of the current generation of Reynolds stress closures. It will be shown how secondorder closure models and two-equation models with an anisotropic eddy viscosity can be systematically derived from the Navier-Stokes equations when one overriding assumption is made: the turbulence is locally homogeneous and in equilibrium. A brief review of zero equation models and one equation models based on the Boussinesq eddy viscosity hypothesis will first be provided in order to gain a perspective on the earlier approaches to Reynolds stress modeling. It will, however, be argued that since turbulent flows contain length and time scales that change dramatically from one flow configuration to the next, two-equation models constitute the minimum level of closure that is physically acceptable. Typically, modeled transport equations are solved for the turbulent kinetic energy and dissipation rate from which the turbulent length and time scales are built up; this obviates the need to specify these scales in an ad hoc fashion. While two-equation models represent the minimum acceptable closure, second-order closure models constitute the most complex level of closure that is currently feasible from a computational standpoint. It will be shown how the former models follow from the latter in the equilibrium limit of homogeneous turbulence. However, the two-equation models that are formally consistent with second-order closures have an anisotropic eddy viscosity with strain-dependent coefficients - a feature that most of the commonly used models do not possess.
An Introduction To Single-Point Closure Methodology
Authors: Launder Brian E.
Published: November 2020

The material presented in Section 1 will replicate that covered in earlier chapters. It may nevertheless be helpful to include it to familiarize the reader both with the nomenclature adopted and the assumptions being made.
Topological Degree Computation
Authors: Sikorski Krzysztof A.
Published: November 2020

In this chapter we address the problem of computing topological degree of Lipschitz functions. From the knowledge of the topological degree one may ascertain whether there exists a zero of a function inside the domain, a knowledge that is practically and theoretically worthwile. Namely, Kronecker’s theorem states that if the topological degree is not zero then there exists a zero of a function inside the domain. Under more-restrictive assumptions one may also derive equivalence statements, i.e., nonzero degree is equivalent to the existence of a zero. By computing a sequence of domains with nonzero degrees and decreasing diameters one can obtain a region with arbitrarily small diameter that contains at least one zero of the function. Such methods, called generalized bisections, have been implemented and tested by several authors, as described in the annotations to this chapter. These methods have been touted as appropriate when the function is not smooth or cannot be evaluated accurately. For such functions they yield close approximations to roots in many cases for which all available other methods tested have failed (see annotations). The generalized bisection methods based on the degree computation are related to simplicial continuation methods. Their worst case complexity in general classes of functions is unbounded, as results of section 2.1.2 indicate; however, for tested functions they did converge. This suggests the need of average case analysis of such methods. There are numerous applications of the degree computation in nonlinear analysis. In addition to the existence of roots, the degree computation is used in methods for finding directions proceeding from bifurcation points in the solution of nonlinear functional differential equations as well as others as indicated in annotations. Algorithms proposed for the degree computation were tested on relatively small number of examples. The authors concluded that the degree of arbitrary continuous function could be computed. It was observed, however, that the algorithms could require an unbounded number of function evaluations. This is why in our work we restrict the functions to still relatively large class of functions satisfying the Lipschitz condition with a given constant K.
Vorticity and Turbulence
Authors: Salmon Rick
Published: November 2020

Turbulence is an immense and controversial subject. Chapters 4, 5, and 6 present some ideas from turbulence theory that are relevant to flow in the oceans and atmosphere. In this chapter, we examine the connections between vorticity and turbulence. From ocean models that omit inertia, we turn to flows in which the inertia is a dominating factor. Vorticity is of central importance, and, in the case of threedimensional motion, we must take its vector character fully into account.
Incorporation of Interfacial Areas in Models of Two-Phase Flow
Authors: Gray William G. , Celia Michael A.
Published: November 2020

The mathematical study of flow in porous media is typically based on the 1856 empirical result of Henri Darcy. This result, known as Darcy’s law, states that the velocity of a single-phase flow through a porous medium is proportional to the hydraulic gradient. The publication of Darcy’s work has been referred to as “the birth of groundwater hydrology as a quantitative science” (Freeze and Cherry, 1979). Although Darcy’s original equation was found to be valid for slow, steady, one-dimensional, single-phase flow through a homogeneous and isotropic sand, it has been applied in the succeeding 140 years to complex transient flows that involve multiple phases in heterogeneous media. To attain this generality, a modification has been made to the original formula, such that the constant of proportionality between flow and hydraulic gradient is allowed to be a spatially varying function of the system properties. The extended version of Darcy’s law is expressed in the following form: qα=-Kα . Jα (2.1) where qα is the volumetric flow rate per unit area vector of the α-phase fluid, Kα is the hydraulic conductivity tensor of the α-phase and is a function of the viscosity and saturation of the α-phase and of the solid matrix, and Jα is the vector hydraulic gradient that drives the flow. The quantities Jα and Kα account for pressure and gravitational effects as well as the interactions that occur between adjacent phases. Although this generalization is occasionally criticized for its shortcomings, equation (2.1) is considered today to be a fundamental principle in analysis of porous media flows (e.g., McWhorter and Sunada, 1977). If, indeed, Darcy’s experimental result is the birth of quantitative hydrology, a need still remains to build quantitative analysis of porous media flow on a strong theoretical foundation. The problem of unsaturated flow of water has been attacked using experimental and theoretical tools since the early part of this century. Sposito (1986) attributes the beginnings of the study of soil water flow as a subdiscipline of physics to the fundamental work of Buckingham (1907), which uses a saturation-dependent hydraulic conductivity and a capillary potential for the hydraulic gradient.
Present Directions and Future Research in Vadose Zone Hydrology
Authors: Jury William A.
Published: November 2020

The last decade has been an active one for research in vadose zone hydrology (VZH). There are a host of new experimental devices, lots of new theories, and a bright new generation of scientists eager to unlock the mysteries of the discipline. It would be tempting to say that we are well on our way to conquering the most difficult problems that face experimentalists and modelers in the VZH field. However, as is so often the case in science, new problems are discovered in the process of solving other ones. I have been given the task of providing an overview of the current directions in our field, and of pointing out unsolved problems and future research directions for the discipline. Execution of such a task is well beyond my abilities or vision, so what you will get is a compendium of my personal preferences and bias. I chose several methods carry out my charge. First, I examined the poster abstracts to get an idea of the content and breadth of the offerings for the symposium “Vadose Zone Hydrology—Cutting Across Disciplines.” Next, I examined 1 year’s worth of articles in the S-l section of the Soil Science Society of America Journal and in Water Resources Research at a 10-year interval to get an idea of the changes in people’s interests in research over that time span. Finally, I polled my own research group and asked some colleagues what the really tough problems were in the discipline of VZH. One way to find out what is going on in the world of VZH is to examine the poster abstracts from the above-named conference. Table 17.1 presents an organizational summary of the 78 posters by subject matter. It is clear that the most active areas are property measurement, monitoring, and characterizing large-scale systems, which reflects both the influx of new monitoring devices and also increased attention paid to details of scale-dependence, interpolation, disturbance during monitoring, and other issues that have become research areas in their own right.
Pleistocene Events in the Herpetofaunas of Britain and Europe, and North America Compared
Authors: Holman J. Alan
Published: November 2020

This last chapter deals with differences and similarities between British and European and North American Pleistocene herpetofaunas. Compared with North America, Britain and Europe had a depauperate Pleistocene herpetofauna, which has carried over into modern times. For instance, the large, "warm" country of Spain, which by European standards has a rich modern herpetofauna, has only 13 species of snakes and four species of nonmarine turtles (Engelmann et al., 1986). On the other hand, Michigan, a northern border state with cold winters, has 17 species of snakes and 11 species of turtles (Holman et al., 1989; Harding and Holman, 1990). Indiana, just south of Michigan, has 31 species of snakes and 15 species of turtles (Minton, 1972; Brown, 1996; Conant and Collins, 1991). The southern coastal state of Florida has 45 species of snakes and 20 species of nonmarine turtles (Conant and Collins, 1991). This is almost twice as many snakes and more than three times as many nonmarine turtles as occur in Britain and Europe. In the Pleistocene, British or European herpetofaunas are considered to be rich when they contain 10 species. In North America, Pleistocene herptofaunas with more than 20 species are common, and sites with more than 40 herpetological species are known (Holman, 1995c). The reasons for these differences are as follows. Both North America and Europe became herpetologically enriched in the Miocene. But the climatic deterioration at the end of the Miocene caused a depletion of the herpetofauna in Europe. Because Europe was mainly isolated from Africa by the Mediterranean Sea and from warm areas to the east by mountain ranges and seas, its depauperate herpetofauna persisted into modern times. Ireland and Britain have even more depauperate modern herpetofaunas than the continent because these islands were cut off from the mainland before they could be reinvaded by all of the species displaced by the last glaciation (Fig. 45). In North America, however, with a vast, accessible southern land mass, and equable Pleistocene climates south of the periglacial regions (Lundelius et al., 1983), the richness of the Miocene herpetofauna persisted into Pleistocene and modern times.
Needs for Food: Are We Asking Too Much?
Authors: Waterlow J. C.
Published: November 2020

The Royal Society has in recent years taken a great interest in the growth of the world’s population and has been represented at the two big international congresses on this subject, in Delhi and in Cairo (Graham-Smith, 1994). According to U.N. projections, in 20 year’s time the world population will be between 7.5 and 8.5 billion (Demeny, 1996). There does not seem to be much controversy about these figures. On the other hand, when it comes to the question of whether it will be possible to feed these 8 billion people, opinions diverge widely between optimists and pessimists. McCalla (1995), the director of the Agriculture and Natural Resources Department of the World Bank, in a very illuminating discussion of the controversy, has said, “The economists are always wrong,” presumably because they have to deduce future trends from those of the past. It seemed to us that the best way to make a useful contribution is to look at the subject and assess the possibilities from an objective scientific point of view. The Royal Society has done this twice in the past, with two discussion meetings: one on Agricultural Efficiency (Cooke et al., 1977) and the other on Technology in the 1990s: Agriculture and Food (Blaxter and Fowden, 1985). Now, 10 years on, it is time to have another go, widening the scope of the recent discussion meeting “Land Resources: On the Edge of the Malthusion Precipice?” The late Kenneth Blaxter, in a scries of lectures called “People, Food and Resources,” published in 1986, recalled a quotation from Friedrich Engels, writing in 1844 about the Malthusian dilemma: “Science advances in proportion to the knowledge bequeathed to it by the previous generation and thus under the most ordinary conditions grows in geometrical progression — and what is impossible for science?” (my italics).
On-line String Searching
Authors: Apostolico A.
Published: November 2020

In the previous two chapters, we have examined various serial and parallel methods to perform exact string searching in a number of operations proportional to the total length of the input. Even though such a performance is optimal, our treatment of exact searches cannot be considered exhausted yet: in many applications, searches for different, a-priorily unknown patterns are performed on a same text or group of texts. It seems natural to ask whether these cases can be handled better than by plain reiteration of the procedures studied so far. As an analogy, consider the classical problem of searching for a given item in a table with n entries. In general, n comparisons are both necessary and sufficient for this task. If we wanted to perform k such searches, however, it is no longer clear that we need kn comparisons. Our table can be sorted once and for all at a cost of O(n log n) comparisons, after which binary search can be used. For sufficiently large k, this approach outperforms that of the k independent searches. In this chapter, we shall see that the philosophy subtending binary search can be fruitfully applied to string searching. Specifically, the text can be pre-processed once and for all in such a way that any query concerning whether or not a pattern occurs in the text can be answered in time proportional to the length of the pattern. It will also be possible to locate all the occurrences of the pattern in the text at an additional cost proportional to the total number of such occurrences. We call this type of search on-line, to refer to the fact that as soon as we finish reading the pattern we can decide whether or not it occurs in our text. As it turns out, the auxiliary structures used to achieve this goal are well suited to a host of other applications. There are several, essentially equivalent digital structures supporting efficient on-line string searching. Here, we base our discussion on a variant known as suffix tree. It is instructive to discuss first a simplified version of suffix trees, which we call expanded suffix tree.
The Relevance of Biogeochemistry to Amazon Development and Conservation
Authors: McClain Michael
Published: November 2020

To read the press of recent years, one might imagine that the fate of the world rests in the hands of those who would develop the Amazon basin. Waves of incoming colonists are blamed for the bulk of the deforestation and development (Schomberg 1998), but Asian logging firms, multinational oil companies, and gold miners are also portrayed as destructive agents hacking down the forest, systematically undermining its biodiversity, and severely contaminating its myriad ecosystems (Althaus 1996, Ferreira 1996, James 1998). The effects of these varied threats are regularly broadcast in alarming tones. Rueters News Service warned in January 1998 that “Brazil’s Amazon rain forest, the world’s richest trove of biological diversity and source of much of the Earth’s oxygen, continues to be ravaged” (Craig 1998). And, in April 1999, a writer for the Associated Press communicated the “fear” of unspecified scientists that “damage to the rain forest... could throw the Earth’s climate out of balance” (Donn 1999). Clearly, the fate of the Amazon and the implications of its fate to the overall Earth system are topics of enormous scientific and popular interest. While there is little disagreement that the complete destruction of Amazon forests would be catastrophic, what about partial deforestation of the region? How much, and which parts, of the Amazon can be converted to sustainable human land uses without compromising the ecological integrity of the conserved areas? How might this development impact regional climate, adjoining coastal systems, and overall global processes? Answers to these volatile questions remain elusive and seemingly endless strands of controversy swirl about them. At the heart of the matter, yet largely beyond the public discussion, are biogeochemical cycles that support and regulate the functioning of the Amazonia’s biological systems. Moreover, it is the incomplete understanding of these cycles that promotes uncertainty and feeds the controversy. The purpose of this book is to present a coherent assessment of our current understanding of the biogeochemical functioning of the Amazon basin. Although it is surely presumptuous to assume that this presentation will shed sufficient light on the uncertainties to eliminate the current controversies, we hope that it will provide a basis for lifting the discussion to a higher level.
Nutrient Cycling as a Function of Landscape and Biotic Characteristics in the Cerrados of Central Brazil
Authors: Haridasan M.
Published: November 2020

The cerrados of central Brazil have long been designated savannas without sufficient understanding of the structure and functioning of the different vegetation forms in the region. Excessive emphasis on identifying similarities with other savannas in Africa and Australia, and even within South America outside Brazil, prevented researchers from recognizing the cerrados’ special features and interdependence among themselves in the landscape where they occur. The more extensive cerrado sensu stricto on dystrophic soils, and to a lesser extent the gallery forests known locally as matas de galeria or matas ciliares, dominated the attention of most botanists and other researchers (Ratter and Dargie 1992, Furley 1992, Furley and Ratter 1988, Furley et al. 1992). Even with increasing interest in biodiversity and ecosystem functioning, very little ongoing research is reported on nutrient cycling from the cerrado region (Solbrig et al. 1996). Information available in the literature is restricted to isolated attempts to describe and quantify specific processes like litterfall and decomposition (Peres et al. 1983), rainwater composition (Schiavini 1983, Delitti 1984), soil fertility gradients (Lopes and Cox 1977), leaf nutrient concentrations (Haridasan 1987, 1992, Araújo and Haridasan 1988), primary productivity of the ground layer (Batmanian and Haridasan 1985, Meirelles and Henrique 1992), effects of burning (Coutinho 1990, Kauffman et al. 1994, Miranda et al. 1996c) and activities of soil fauna (Constantino 1988, Egler and Haridasan 1987, Oliveira Jr. 1985) at specific sites within a particular vegetation. Results of long duration experiments from permanent plots or watersheds are not yet reported in the literature. Very little information is available on the food webs or the role of fauna in nutrient cycling. Research on specific processes like CO2 emission on an ecosystem basis is quite recent (Miranda et al. 1996a, b, Mier et al. 1996). The following discussion is therefore restricted to the occurrence of different vegetation forms in the cerrado region and environmental factors affecting their distribution and functioning in relation to nutrient availability and nutrient cycling processes. One of the difficulties in getting information on research already carried out in Brazil is that the dissertations of graduate students in the universities are seldom published in indexed journals.
The Role of the United States in the Post-Cold War World
Authors: Rostow W. W.
Published: November 2020

As in the other chapters in this book, it is wise to begin by recalling the past. In this case, I begin with the history and concepts that have guided U.S. foreign policy. This historical survey is useful first because the issues we will confront in the next half century, while distinctive, will not be wholly new. Americans have wrestled with them, wisely or otherwise, in the past, and that should help provide perspective as we face the future on the other side of the Great Spike. Second, looking forward, it is necessary to see the past as objectively as we can. There are endless aphorisms about the usefulness of history to illuminate the present and the future, as well as many concerning its lack of usefulness. In general, the use of history as a guide to the future has a bad name. Samuel Taylor Coleridge in one century and Lewis Namier in another both asserted that humanity could only look at the past and was incapable of looking forward. But in a book about the future, there is virtue in trying to belie Coleridge and Namier and, looking backward as well as forward, in trying to clarify where we have come from and what we face in the time ahead. In the half century from the Revolutionary War to President James Monroe's message to the Congress in 1823, the United States evolved from a group of colonies to a nation-state. In this half century, the United States gained its independence with the decisive aid of France. It struggled through another war with Britain over a neutral country's right to freedom of the seas. In 1823, it moved to guarantee the independence of its hemisphere against military intrusion from outside. There was an abiding security as well as an ideological component in the Monroe Doctrine. As for security, it warned the nations of Europe, including Russia, not to extend their military presence in the hemisphere. John C. Calhoun, then secretary of war, wished the United States to guarantee not merely the independence of Latin America from any extension of European power but also Latin America's movement toward democracy. John Quincy Adams, then secretary of state, had two objections. First, he felt that "the feudal and clerical heritage" of Latin America would render its movement toward democracy problematic.
Primary Production
Authors: Bowman William D. , Fisk Melany C.
Published: November 2020

The production of biomass by plants is of central importance to energy, carbon, and nutrient fluxes in ecosystems. Knowledge of the spatial and temporal variation of production and the underlying biotic and physical controls on this variation are central themes in ecosystem science. The goals of this chapter are to present the estimates of spatial patterns in above- and belowground production associated with the major community types found on Niwot Ridge and other alpine areas of the southern Rocky Mountains and to examine the likely environmental causes and underlying mechanisms responsible for spatial and temporal variation in production as elucidated by experimental and observational studies. Rates of primary production and standing crops of plant biomass are low in alpine tundra relative to other ecosystem types (Lieth and Whittaker 1975; Zak et al. 1994). However, within communities (i.e., at the plot level), there is large variation in rates of production, the degree of biotic control over response to environmental change, and the principal environmental constraints of primary production. As a result, the alpine is one of the most dynamic ecosystems for research. For example, there is a tenfold difference in annual aboveground production between the most and least productive sites with continuous plant cover on Niwot Ridge. In addition, the high plant diversity is a source of potential variation in physiological and developmental control of plant response to the environment. Dominant species include sedges, grasses, shrubs, and forbs, among which are N2-fixing Trifolium species. Nearly all of the dominant species may be mycorrhizal. Soil moisture, a driving force for many biotic processes, may vary by an order of magnitude between wet and dry sites following prolonged periods of drought. Thus the alpine tundra of Niwot Ridge, which might appear superficially homogeneous, in fact has complex physical and biotic gradients. This spatial variation prevents simple generalizations about single limiting resources or climatic driving forces determining spatial and temporal variation in productivity. Billings (1973) defined the mesotopographic gradient as a working unit for describing the alpine landscape, as it encompasses the full range of snow accumulation and associated microclimates and thus biological diversity.
Soil-Atmosphere Gas Exchange
Authors: Schmidt Steven K. , West Ann E.
Published: November 2020

The alpine, while not extensive in global area, has several advantages for trace gas research, particularly the spatial landscape heterogeneity in soil types and plant communities. This variation can be viewed as a “natural experiment,” allowing field measurements under extremes of moisture and temperature. While the atmospheric carbon dioxide (CO2) record at Niwot Ridge extends back to 1968 (chapter 3), and NOAA has done extensive measurements on atmospheric chemistry at the subalpine climate station (e.g., Conway et al. 1994), work on tundra soil-atmosphere interactions were not initiated until recently. In 1992, studies were begun on Niwot Ridge to gain a comprehensive understanding of trace gas fluxes from alpine soils. Our sampling regime was designed to capture the spatial and temporal patterns of trace gas fluxes in the alpine. In addition, we coupled our studies of trace gas fluxes with ongoing studies of nitrogen cycling on Niwot Ridge (Fisk and Schmidt 1995,1996; Fisk et al. 1998; chapter 12). Methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) were studied because of their role in global environmental change and because they could be easily monitored at our remote sites. On a per-molecule basis, CH4 and N2O are much more potent as greenhouse gases than CO2 is (Lashof and Ahuja 1990; Rodhe 1990). In addition, N2O plays a role in ozone depletion in the stratosphere. The global CH4 and N2O budgets are still poorly understood and the relative importance of soils in these budgets is even less clear. For example, estimates of the global soil sink for CH4 range from 9.0 to 55.9 Tg per year (Dörr et al. 1993). This range is large compared with the approximately 30 Tg of excess CH4 that is accumulating in the atmosphere every year. To better assess the role of soil in trace gas budgets, our work focused on investigating landscape patterns of gas fluxes (CH4, N2O, and CO2) and environmental controls on these fluxes.
Drift Mechanisms in the 1920s
Authors: Oreskes Naomi
Published: November 2020

The final chapter of the third edition of The Origin of Continents and Oceans was devoted to the dynamic causes of drift, and Wegener’s tone in these final fifteen pages was decidedly more tentative than in the rest. Frankly acknowledging the huge uncertainties surrounding this issue, he proceeded on the basis of a phenomenological argument. Mountains, Wegener pointed out, are not randomly distributed: they are concentrated on the western and equatorial margins of continents. The Andes and Rockies, for example, trace the western margins of North and South America; the Alps and the Himalayas follow a latitudinal trend on their equatorial sides of Europe and Asia. If mountains are the result of compression on the leading edges of drifting continents, then the overall direction of continental drift must be westward and equatorial. Continental displacements are not random, as the English word drift might imply, but coherent. This coherence had been the inspiration for an earlier version of drift proposed by the American geologist Frank Bursley Taylor (1860–1938). A geologist in the Glacial Division of the U.S. Geological Survey under T. C. Chamberlin, Taylor was primaril known for his work on the Pleistocene geology of the Great Lakes region. But his knowledge extended beyond regional studies: as a special student at Harvard, he had studied geology and astronomy; as a survey geologist under the influence of Chamberlin and G. K. Gilbert, he had published a number of articles on theoretical problems. One of these was an 1898 pamphlet outlining a theory of the origin of the moon by planetary capture; in 1903, Taylor developed his theoretical ideas more fully in a privately published book. Turning the Darwin–Fisher fissiparturition hypothesis on its head, Taylor proposed that the moon had not come from the earth but had been captured by it after the close approach of a cornet. Once caught, (lie tidal effect of the moon increased the speed of the earth’s rotation and pulled the continents away from the poles toward the equator. In 1910, Taylor pursued the geological implications of this idea in an article in the Bulletin of the Geological Society of America entitled “Bearing of the Tertiary Mountain Belt on the Origin of the Earth’s Plan.”
Nonequilibrium Fractionation and Isotopic Transport
Authors: Criss Robert E.
Published: November 2020

At the Earth’s surface, isotopic disequilibrium is far more common than isotopic equilibrium. Although isotopic equilibrium is approached in certain instances, numerous constituents of the lithosphere, hydrosphere, atmosphere, and biosphere are simply not in mutual isotopic equilibrium. This condition is consistent with the complex and dynamic conditions typical of the Earth’s surface, particularly the large material fluxes, the rapid changes in temperature, and the biological mediation of chemical systems. Fortunately, several aspects of isotopic disequilibrium may be understood in terms of elementary physical laws. For homogeneous phases such as gases or well-stirred liquids, or for cases where spatial gradients in isotopic contents are not of primary interest, then the principles of elementary kinetics can be applied. For cases where isotopic gradients are important, the laws of diffusion are applicable. If two phases are out of isotopic equilibrium, they will progressively tend to approach the equilibrium state with the passage of time. This phenomenon occurs by the process of isotopic exchange, and its rate may be understood by examining isotopic exchange reactions from the viewpoint of elementary kinetic theory. In particular, consider the generalized exchange reaction where A and B are two phases that share a common major element, and A* and B* represent the same phases in which the trace isotope of that element is present. The present analysis is simplified if the exchange reaction is written so that only one atom is exchanged, in which case the stoichiometric coefficients are all unity. For reaction 4.1, kinetic principles assert that the forward and reverse reactions do not, in general, proceed at identical rates, but rather at the rates indicated by the quantities kα and k written by the arrows, multiplied by the appropriate concentrations terms. Assuming that the reaction is first order, then the reaction progress, represented by the quantity dA*/dt, may be expressed by the difference between these forward and reverse rates, as follows: . . . dA*/dt = kα(A)(B*) − k(A*)(B) (4.2) . . . In order to evaluate the exchange process more completely, is important to carefully chose a consistent set of concentrations for substitution equation 4.2.
Patterns and Controls of Soil Water in the Jornada Basin
Authors: Mitchell Katherine A. , Herrick Jeffrey E.
Published: November 2020

This chapter focuses on controls and patterns of soil moisture in the Jornada Basin. First we describe general properties that commonly contribute to soil water heterogeneity; second, we offer a brief overview of soil water research in the Jornada Basin; and last, we describe specific patterns of soil water content and availability observed in the Jornada Basin. Our goal is to describe general patterns of soil water that are likely to occur across the Chihuahuan Desert region. In arid and semiarid regions, water is typically thought to be the most limiting resource to biological activity (Noy-Meir 1973), though colimitation by water and nitrogen may be a more general rule (Hooper and Johnson 1999; see also chapter 6). The availability of water affects plant productivity, microbial activity, activity of biological soil crusts, nutrient cycling, and organic matter decomposition. It also directly and indirectly affects soil erosion, chemical weathering, and carbonate formation. There are several hypotheses addressing how water availability affects plant productivity in desert environments. Beatley (1974) proposed that various functional types (e.g., shrub, perennial grass, annual forb) have different seasonal rainfall thresholds to trigger phenological responses. The annual productivity of functional types is therefore determined by the timing and amount of rainfall. Westoby (Noy-Meir 1973) proposed the pulse-reserve paradigm to explain population dynamics of desert plants. In this view, a rain event triggers a pulse of production. Some of that production is used to generate new tissue, but part of the production is diverted into reserves. The amount of reserves in part determines the next production pulse, as well as the minimum size of the next trigger event. Rainfall is highly variable both spatially and temporally in arid regions; therefore, understanding patterns of rainfall and interactions between rainfall patterns, soil characteristics, temperature, and topography are critical to predicting ecosystem responses. The relationship between average annual precipitation and plant productivity across arid regions has substantial predictive ability (Le Houérou 1984). However, for a given site, the relationship between annual precipitation and yearly plant productivity has limited explanatory power (Lauenroth and Sala 1992).