bluuebunny/crossref_metadata_2025 huggingface dataset:
An Introduction to Climate Variability and Ecosystem Response
Authors: Greenland David , Goodin Douglas G.
Published: November 2020

The regularities of our planet’s climate determine a large part of the form and function of Earth’s ecosystems. The frequently nonlinear operation of the atmosphere gives rise to a rich complexity of variability superimposed on the fundamental regularities. A traditional definition of climate is “the long-term state of the atmosphere encompassing the aggregate effect of weather phenomena—the extremes as well as the mean values” (Barry and Chorley 1987). Ecosystems share some of the same properties as the climate system. At one level their operation is fairly straightforward. Ecologists, to a certain extent, understand the flows of energy and matter through these systems. A good deal of ecosystem operation over time is characterized by some degree of homeostasis. On the other hand, nonlinear change and multiple variables have placed uncertainty and surprise at the forefront of much ecological research. In both the climate and the ecosystem the only certainty often appears to be change. The task of this book is to focus on some of this change at the interface between the climate and the ecosystem and by doing so gain insights into the operation of both systems. Millennial-scale (1000-year) climate variability has driven large changes of vegetation and fauna at almost all of the Long-Term Ecological Research (LTER) sites. Decadal climate variability at some sites has seen dramatic changes in fish catches and has altered tree species composition. During the first two decades of study, LTER sites have been affected by two super El Niño events and several more “normal” El Niños and La Niñas. Major droughts have affected species diversity and killed some trees. Severe storms and floods have damaged stream restoration structures. Coastal sites have measured a rise in sea level. Antarctic sites have documented the decrease of some penguin populations and a rise in other populations as a result of climatic warming over 50 or more years. Climate variability has constantly been on investigators’ minds. It is little wonder that ecologists clearly recognize climate as a driver of biotic systems. Parmesan and her coworkers describe how climate affects individual fitness, population dynamics, and the distribution and abundance of species, as well as ecosystem structure and function (Parmesan et al. 2000).
An LTER Network Overview and Introduction to El Niño–Southern Oscillation (ENSO) Climatic Signal and Response
Authors: Greenland David
Published: November 2020

Part II of this book deals with the quasi-quintennial timescale that is dominated by the El Niño–Southern Oscillation (ENSO) phenomenon. During the last 50 years, ENSO has operated with a recurrence interval between peak values of 2–7 years. The term quasi-quintennial is chosen to recognize that climatic events other than ENSO-related ones might occur at this timescale. The general significance of the ENSO phenomenon lies in its influence on natural and human ecosystems. It has been estimated that severe El Niño–related flooding and droughts in Africa, Latin America, North America, and Southeast Asia resulted in more than 22,000 lives lost and more than $36 billion in damages during 1997– 1998 (Buizer et al. 2000). The specific significance of ENSO within the context of this book is that it provides fairly well-bounded climatic events for which specific ecological responses may be identified. In the other chapters in part II, we first look at the U.S. Southwest. The Southwest is home to an urban LTER site, the Central Arizona-Phoenix (CAP) site. Tony Brazel and Andrew Ellis describe the clear ENSO climatic signal at this site and identify surprising responses that cascade into the human/economic system. Ray Smith, Bill Fraser, and Sharon Stammerjohn provide more details of the fascinating ecological responses of the Palmer Antarctic ecosystem to ENSO. World maps of ENSO climatic signals do not usually show the Antarctic, and the LTER program provides some groundbreaking results at this location, with Smith and coworkers (see the Synthesis at the end of this part) providing such maps (figures S.1 and S.2). Kathy Welch and her colleagues present equally new discoveries related to freshwater aquatic ecosystems from the other Antarctic LTER site at the McMurdo Dry Valleys. This chapter gives a general introduction to ENSO and its climatic effects. How ever, these general patterns may mask the detailed responses that occur at individual locations. This is one reason for presenting the principal results of previous findings related to El Niños and LTER sites and one particular analysis focused on LTER sites. This analysis for the period 1957–1990 investigates the response of monthly mean temperature and monthly total precipitation standardized anomaly values to El Niño and La Niña events as indicated by the Southern Oscillation Index (SOI) (Greenland 1999).
Watershed Hydrological and Chemical Responses to Precipitation Variability in the Luquillo Mountains of Puerto Rico
Authors: Schaefer Douglas
Published: November 2020

Variations in temperature and precipitation are both components of climate variability. Based on coral growth rates measured near Puerto Rico, the Caribbean was 2–3ºC cooler during the “Little Ice Age” during the seventeenth century (Winter et al. 2000). At the millennial scale, temperature variations in tropical regions have been inferred to have substantial biological effects (such as speciation and extinction), but not at the multidecadal timescales considered here. My focus is on precipitation variability in particular, because climate models examining effects of increased greenhouse gases suggest greater changes in precipitation than in temperature patterns in tropical regions. Some correspondence between both the El Niño–Southern Oscillation (ENSO) and the Northern Atlantic Oscillation (NAO) and average temperatures and total annual precipitation have been reported for the LTER site at Luquillo (Greenland 1999; Greenland and Kittel 2002), but those studies did not refer to extreme events. Based on climate records for Puerto Rico since 1914, Malmgren et al. (1997) found small increases in air temperature during El Niño years and somewhat greater total rainfall during the positive phase of the NAO. Similar to ENSO, the NAO index is characterized by differences in sea-level atmospheric pressure, in this case based on measurements in Iceland and Portugal (Walker and Bliss 1932). Its effects on climate have largely been described in terms of temperature and precipitation anomalies in countries bordering the North Atlantic (e.g., Hurrell 1995). Puerto Rico is in the North Atlantic hurricane zone, and hurricanes clearly play a major role in precipitation variability. The association between extreme rainfall events and hurricanes is discussed in detail in this chapter. I examine the degree to which extreme rainfall events are associated with hurricanes and other tropical storms. I discuss whether the occurrence of these extreme events has changed through time in Puerto Rico or can be linked to the recurrent patterns of the ENSO or the NAO. I examine the 25-year daily precipitation record for the Luquillo LTER site, the 90-year monthly record from the nearest site to Luquillo with such a long record, Fajardo, and those of the two other Puerto Rico stations with the longest daily precipitation records, Manati and Mayaguez (figure 8.1).
Consequences of Borders
Authors: Goldsmith Jack , Wu Tim
Published: November 2020

Australia’s Joseph Gutnick is a billionaire, a diamond and gold miner, a political player, a philanthropist, and a rabbi. On October 20, 2000, Gutnick awoke in Victoria to find himself accused of tax evasion and money laundering by the American business magazine Barron’s. The article, “UnHoly Gains,” suggested that Gutnick had engaged in shady dealings with Nachum Goldberg, a Melbourne money launderer jailed in 2000 for washing AU$42 million in used notes through a bogus Israeli charity. Gutnick read the story, not in the print version of Barron’s but on the online version of its sister publication, “wsj.com,” a website on a server physically located in New Jersey. Gutnick was not the only Australian to read the story. Approximately seventeen hundred Australians subscribed to wsj.com, including many Australian business and finance leaders. An enraged Gutnick vehemently denied the illicit association with Goldberg. To protect his reputation, he sued Dow Jones & Company—the parent company of both Barron’s and the Wall Street Journal—in an Australian court, taking advantage of tough Australian libel laws unleavened by the U.S. First Amendment. The legal arguments in the Gutnick case mirrored those in the Yahoo litigation in France a few years earlier. Dow Jones argued that Australian courts were legally powerless (or “without jurisdiction”) to rule on the legality of information on a computer in the United States, even if it appeared in Australia. The Australian High Court, like the court in France, disagreed. For material published on the Internet, it stated, the place where the person downloads the material “will be the place where the tort of defamation is committed.” Within two years of this decision, Dow Jones agreed to pay Gutnick AU$180,000 in damages and AU$400,000 in legal fees to settle the case. It also issued this retraction: “Barron’s has no reason to believe Mr. Gutnick was ever a customer of Mr. Goldberg, and has no reason to believe that Mr. Gutnick was a money laundering customer of, or had any criminal or other improper relationship with, Mr. Goldberg.”
Successional Processes in the Alaskan Boreal Forest
Authors: Fastie Christopher L. , Ott Robert A.
Published: November 2020

Superimposed on the topographic and climatic gradients in vegetation described in Chapter 6 are mosaics of stands of different ages reflecting the interplay between disturbance and succession, that is, the ecosystem changes that follow disturbance. The nature of disturbance governs vegetation succession, and vegetation properties, in turn, influence disturbance regime. Both disturbance and succession are controlled by state factors and by stochastic variation in local conditions such as weather and the abundance of herbivores. Even in this relatively simple biome, the interactions among site, chance, and disturbance history result in a vast array of possible successional trajectories following a disturbance event, generating at least 30 forest types in interior Alaska (Viereck et al. 1992). Despite this broad range of possible dynamics, certain patterns recur more frequently than others (Drury 1956, Viereck 1970). In this chapter, we discuss selected successional pathways that commonly occur on river floodplains and on permafrost-free or permafrost-dominated upland sites in interior Alaska. River floodplains occupy only 17% of interior Alaska, but they account for 80% of the region’s commercial forests and therefore have attracted considerable attention from forest managers (Adams 1999). These forests provide an excellent example of primary succession, that is, the succession that occurs on surfaces that have not been previously vegetated. Although many successional pathways are possible on interior Alaska’s floodplains (Fig. 7.1; Drury 1956), the trajectory that actually occurs in a particular place is usually determined by the patterns of colonization during the first decades (Egler 1954). This, in turn, depends primarily on physical environment, flood events, and seed availability. For example, fine-textured sediments, which are common along the gradual grade of the Tanana River near Fairbanks (Chapter 3), retain more moisture than gravelly substrates and favor establishment of thinleaf alder (Alnus incana subsp. tenuifolia) following the initial colonization by willow (Salix). Alder is therefore a more important component of this successional sequence than along some other rivers. In this chapter, we focus on the alder-mediated pattern of floodplain succession, which has been the major focus of the LTER research program. The common and scientific names of species mentioned in this chapter are given in Table 6.1.
Summary and Synthesis: Past and Future Changes in the Alaskan Boreal Forest
Authors: Walker Marilyn W. , Edwards Mary E.
Published: November 2020

Historically the boreal forest has experienced major changes, and it remains a highly dynamic biome today. During cold phases of Quaternary climate cycles, forests were virtually absent from Alaska, and since the postglacial re-establishment of forests ca 13,000 years ago, there have been periods of both relative stability and rapid change (Chapter 5). Today, the Alaskan boreal forest appears to be on the brink of further significant change in composition and function triggered by recent changes that include climatic warming (Chapter 4). In this chapter, we summarize the major conclusions from earlier chapters as a basis for anticipating future trends. Alaska warmed rapidly at the end of the last glacial period, ca 15,000–13,000 years ago. Broadly speaking, climate was warmest and driest in the late glacial and early Holocene; subsequently, moisture increased, and the climate gradually cooled. These changes were associated with shifts in vegetation dominance from deciduous woodland and shrubland to white spruce and then to black spruce. The establishment of stands of fire-prone black spruce over large areas of the boreal forest 5000–6000 years ago is linked to an apparent increase in fire frequency, despite the climatic trend to cooler and moister conditions. This suggests that long-term features of the Holocene fire regime are more strongly driven by vegetation characteristics than directly by climate (Chapter 5). White spruce forests show decreased growth in response to recent warming, because warming-induced drought stress is more limiting to growth than is temperature per se (Chapters 5, 11). If these environmental controls persist, projections suggest that continued climate warming will lead to zero net annual growth and perhaps the movement of white spruce to cooler upland forest sites before the end of the twenty-first century. At the southern limit of the Alaskan boreal forest, spruce bark beetle outbreaks have decimated extensive areas of spruce forest, because warmer temperatures have reduced tree resistance to bark beetles and shortened the life cycle of the beetle from two years to one, shifting the tree-beetle interaction in favor of the insect (Chapter 9).
Enzyme Chemistry in Carbon Dioxide
Authors: Rodney Rebecca L. , Russell Alan J.
Published: November 2020

Enzymes are biocatalysts constructed of a folded chain of amino acids. They may be used under mild conditions for specific and selective reactions. While many enzymes have been found to be catalytically active in both aqueous and organic solutions, it was not until quite recently that enzymes were used to catalyze reactions in carbon dioxide when Randolph et al. (1985) performed the enzyme-catalyzed hydrolysis of disodium p-nitrophenol using alkaline phosphatase and Hammond et al. (1985) used polyphenol oxidase to catalyze the oxidation of p-cresol and p-chlorophenol. Since that time, more than 80 papers have been published concerning reactions in this medium. Enzymes can be 10–15 times more active in carbon dioxide than in organic solvents (Mori and Okahata, 1998). Reactions include hydrolysis, esterification, transesterification, and oxidation. Reactor configurations for these reactions were batch, semibatch, and continuous. There are many factors that influence the outcome of enzymatic reactions in carbon dioxide. These include enzyme activity, enzyme stability, temperature, pH, pressure, diffusional limitations of a two-phase heterogeneous mixture, solubility of enzyme and/or substrates, water content of the reaction system, and flow rate of carbon dioxide (continuous and semibatch reactions). It is important to understand the aspects that control and limit biocatalysis in carbon dioxide if one wants to improve upon the process. This chapter serves as a brief introduction to enzyme chemistry in carbon dioxide. The advantages and disadvantages of running reactions in this medium, as well as the factors that influence reactions, are all presented. Many of the reactions studied in this area are summarized in a manner that is easy to read and referenced in Table 6.1. Carbon dioxide is cited as a good choice of solvents for a number of reasons. Some of the advantages of running reactions in carbon dioxide instead of the more traditional organic solvents include the low viscosity of the solvent, the convenient recovery of the products and non-reacted components, abundant availability, low cost, no solvent contamination of products, full miscibility with other gases, non-existent toxicity, low surface tension, non-flammability, and recyclability. The low mass-transfer limitations are an advantage because of the large diffusivity of reactants.
Coatings from Liquid and Supercritical Carbon Dioxide
Authors: Chernyak Yury , Henon Florence
Published: November 2020

This chapter describes several aspects of the use of carbon dioxide as a solvent or cosolvent in coating applications. The primary impetus for using carbon dioxide for this purpose has been the alleviation of volatile emissions and liquid solvent wastes. However, the special physical properties of liquid and supercritical carbon dioxide may offer some processing advantages over conventional organic or aqueous solvents. Liquid carbon dioxide is quite compressible, and a reduction in temperature results not only in a reduction in the operating pressure, but also in a significant increase in the liquid density to values of approximately 0.9 g/cm3. At these high liquid densities, carbon dioxide exhibits improved solvent performance, but with much lower viscosities and interfacial tensions than aqueous or organic liquid solvents. Under supercritical conditions, carbon dioxide also exhibits high densities, low viscosities, and improved solvent power. Low viscosities and interfacial tensions tend to facilitate the transport of the solvents into any crevices or imperfections on the surface to be covered, and this might prove advantageous in the coating of patterned or etched surfaces. Since carbon dioxide dissolves and diffuses easily into many different polymers and organic liquids, it can also be used to reduce the viscosity of coating solutions. Whether in the liquid or the supercritical state, the temperature and pressure of the mixture can be used to control its physical properties in ways that are impossible to achieve with traditional solvents. These distinguishing features have raised the level of industrial interest in carbon dioxide as a solvent for coating applications, beyond those based solely on environmental concerns. In this chapter, we will discuss current applications and research on the use of CO2 as a solvent for coatings. The first section deals with spray coating from supercritical CO2. Subsequent sections deal with the use of liquid coatings, such as spin and free meniscus coatings, and impregnation coatings. Since the start of the 20th century (ca. 1907), atomization has been the basis for conventional spray coating applications (Muirhead, 1974). Typically, atomization is caused by high shear of the coating fluid in air, leading to droplet or particle formation.
An Introduction to Cellular Computing
Authors: Amos Martyn , Owenson Gerald
Published: November 2020

The abstract operation of complex natural processes is often expressed in terms of networks of computational components such as Boolean logic gates or artificial neurons. The interaction of biological molecules and the flow of information controlling the development and behavior of organisms is particularly amenable to this approach, and these models are well established in the biological community. However, only relatively recently have papers appeared proposing the use of such systems to perform useful, human-defined tasks. Rather than merely using the network analogy as a convenient technique for clarifying our understanding of complex systems, it is now possible to harness the power of such systems for the purposes of computation. The purpose of this volume is to discuss such work. In this introductory chapter we place this work in historical context and provide an introduction to some of the underlying molecular biology. We then introduce recent developments in the field of cellular computing. Despite the relatively recent emergence of molecular computing as a distinct research area, the link between biology and computer science is not a new one. Of course, for years biologists have used computers to store and analyze experimental data. Indeed, it is widely accepted that the huge advances of the Human Genome Project (as well as other genome projects) were only made possible by the powerful computational tools available to them. Bioinformatics has emerged as the science of the 21st century, requiring the contributions of truly interdisciplinary scientists who are equally at home at the lab bench or writing software at the computer. However, the seeds of the relationship between biology and computer science were sown long ago, when the latter discipline did not even exist. When, in the 17th century, the French mathematician and philosopher René Descartes declared to Queen Christina of Sweden that animals could be considered a class of machines, she challenged him to demonstrate how a clock could reproduce. Three centuries later, with the publication of The General and Logical Theory of Automata [19] John von Neumann showed how a machine could indeed construct a copy of itself.
Anticoagulation Clinics and Self-Testing
Authors: Becker Richard C. , Spencer Frederick A.
Published: November 2020

Oral anticoagulation is a time-tested and effective therapy for patients at risk for thromboembolism (Ansell, 1993). Because of the high risk–benefit ratio of oral vitamin K antagonists, physicians are sometimes reluctant to initiate therapy even for well-established indications (Kutner et al., 1991; McCrory et al., 1995). Furthermore, management is recognized as labor intensive. These factors can be minimized and the benefits of treatment maximized by implementation of an expert model of management that can be achieved with a coordinated and focused system of care known as a coordinated anticoagulation clinic (Ansell and Hughes, 1996). Patient self-testing (and management) may also foster more wide-scale and effective treatment of thromboembolic disorders. The concept of a coordinated anticoagulation clinic (ACC) is not new. Programs focusing on the management of oral anticoagulation have existed in the United States since the late 1950s, and several Scandinavian and other European countries are well known for their coordinated programs (Loeliger et al., 1984), some of which oversee the care of all anticoagulated patients in their respective countries. In the United States, ACCs are growing in number and diversity of services, spurred on by increasing evidence of improved clinical outcomes and cost-effectiveness. The basic elements of a coordinated ACC include (1) a manager or team leader (physician, pharmacist), (2) support staff (nurse practitioner, pharmacist, or physician assistant), (3) standardized record keeping and a computerized database, (4) a manual of operation and practice guidelines, and (5) a formal mechanism for communicating with referring physicians and patients. Currently, most oral anticoagulation therapy in the United States is managed by a patient’s personal physician. In essence, the monitoring and dose titration of patients with thromboembolic disease represents a relatively small proportion of the physician’s overall clinical practice. This approach can be characterized as “traditional” or routine medical care. There may be no specialized system or guidelines in place to track patients or ensure their regular follow-up. An ACC uses a focused and coordinated approach to managing anticoagulation (Ansell et al., 1997).
Anticoagulants
Authors: Becker Richard C. , Spencer Frederick A.
Published: November 2020

Anticoagulant therapy, particularly when used in combination with fibrinolytics and less often platelet antagonists, can cause life-threatening hemorrhage. This supports the importance of coagulation proteases in several phases of thrombus development; paradoxically, several anticoagulants can also cause microvascular and macrovascular thrombotic disorders. Hemorrhage is the most common adverse effect associated with warfarin administration. To predict the risk of bleeding, Beyth and colleagues (1998) developed a 5-point scoring system, with 1 point given for each of the following: . . . • Age greater than 65 . . . . . . • History of stroke . . . . . . • History of gastrointestinal bleeding . . . . . . • Specific comorbid conditions (recent myocardial infarction [MI], elevated serum creatinine, hematocrit <30%, or diabetes) . . . Low-risk patients have a score of 0; intermediate-risk patients, 1 or 2; and high-risk, 3 or 4. The risk of bleeding in these three groupings at 12 months was 3%, 8%, and 30%, respectively. Many commonly used medications have significant interactions with warfarin. In 1994, Wells and colleagues (1994) reviewed all reports of warfarin–drug interactions and found original reports totaling 186. Potentiation of warfarin effect was observed with six antibiotics, five cardiac drugs, two antiinflammatory agents, two histamine2-blockers, and alcohol in persons with concomitant liver disease. Inhibition of warfarin effect was noted with three antibiotics, three central nervous system (CNS) drugs, cholestyramine, and sucralfate. An important interaction between acetaminophen and warfarin has also been recognized (Hylek et al., 1998), and certain herbal remedies, such as ginkgo biloba, ginseng, and garlic, may enhance the effects of warfarin. The first step in the management of bleeding is to stop the drug; however, recovery of clotting factor levels may take several days, depending upon the vitamin K content of the patient’s diet and rate of intrinsic metabolism. To rapidly raise coagulant factor concentrations in patients with life-threatening hemorrhage, clotting factor concentrates are given (Makris et al., 1997). The older concentrates were plasma-derived and consisted mainly of activated prothrombin complex factors. They had the disadvantages of thrombogenicity and potential for transmission of infectious agents.
Cooperative Learning
Authors: Hamburg David A. , Hamburg Beatrix A.
Published: November 2020

U.S. society is becoming increasingly multicultural. With the proliferation of enclaves of arriving immigrants, it follows that conflict will often be defined along ethnic lines. Unfortunately, a legacy of prejudice, sometimes even hatred, has been passed on to some youth by parents, grandparents, and their ethnic communities. Although in general acts of intolerance in the United States are at a more subtle level than that of 20 years ago, currently there are more obvious expressions of violent discrimination and prejudicial behavior in schools. The wide spectrum of U.S. diversity is also experienced in the public school setting, with the racial and ethnic mix far greater than it was even 10 years ago. Similar circumstances now exist in many countries, because immigration and refugee movements have increased in a globalized, turbulent world. The challenges this presents for educators are great. Schools must seek to create safe environments for students to reach out across racial and ethnic borders and begin to empathize with members of other groups. One of the educators’ responses to this challenge has been the development of cooperative learning techniques. In cooperative learning programs, the traditional classroom of one teacher and many students is reorganized into heterogeneous ability groups of four or five students who work together to learn a particular subject matter. Cooperative learning is also an excellent example of contact theory, as previously discussed in Chapter 7, and the relationship is elaborated later in this chapter. Cooperative learning has grown steadily since the early 1970s. These efforts stem partly from a desire to find alternatives to the usual lecture mode and to involve students actively in the learning process. In part, coopera- tive learning builds on the recognized benefits of peer tutoring. Cooperative learning can offset the negative impacts of traditional individual competitiveness for grades, approval, and achievement in which there are inevitable and (after a while) predictable winners and losers. Moreover, cooperative learning can instill appreciation for student diversity and belief in the value of mutual aid. Teachers utilize cooperative methods in small groups in a variety of ways, seeking to strengthen students’ motivation to learn as well as providing individual help for students in the quest for content learning such as mathematics. They also seek to develop skills that lead to high productivity in joint problem solving.
Product Exploration and Discovery
Authors: Wei James
Published: November 2020

It is sometimes said that “necessity is the mother of invention.” Many product innovations have begun with the observation and recognition that many people are in need of a new or improved product, and investigators then looked for a technology that would produce such a product to satisfy this market need. Investigators may examine current products to find what properties need improvement and whether these properties can be modified; for example, raw rubber is brittle when cold and is sticky when hot, whereas vulcanized rubber, which is used to make tires and gaskets, remains flexible whether hot or cold. Investigators may take the more ambitious approach of looking for materials that are not currently used for a particular product to see whether they have better properties to offer: for example, the use of ether as an anesthetic relieved the pain from surgery and childbirth that people were subjected to previously. The more ambitious investigator would attempt to create new synthetic materials to suit a particular market: Freon, a chlorofluorocarbon (CFC), was invented to make a safe refrigerant for home refrigerators. These are called the Market-Pull products, or market looking for a technology. Another frequent innovation path begins with a technology that is dormant or underutilized, followed by the search for new markets. When Freon was established as a safe refrigerant, it became the platform for new markets, such as air conditioning, aerosol propellants, and computer cleaning. Some technologies began as accidental discoveries when investigators were looking for something else, or were driven by curiosity. Penicillin is one of the best known examples of serendipity, of making unexpected discoveries. The most ambitious paths start from planned explorations to create a new technology, followed by the quest for a place in the market. Carothers created the field of synthetic condensation polymerization, and DuPont decided that this method could be used to make nylon fibers to replace silk stockings. These are called the Technology-Push products, or technology looking for a market.
Interspecies Connection Models
Authors: Newman M. E. J. , Palmer R. G.
Published: November 2020

In the Bak-Sneppen model studied in the previous chapter there is no explicit notion of an interaction strength between two different species. It is true that if two species are closer together on the lattice, then there is a higher chance of their participating in the same avalanche. But beyond this there is no variation in the magnitude of the influence of one species on another. Real ecosystems, on the other hand, have a wide range of possible interactions between species, and as a result the extinction of one species can have a wide variety of effects on other species. These effects may be helpful or harmful, as well as strong or weak, and there is in general no symmetry between the effect of A on B and B on A. For example, if species A is prey for species B, then A's demise would make B less able to survive, perhaps driving it also to extinction, whereas B's demise would aid A's survival. On the other hand, if A and B compete for a common resource, then either's extinction would help the other. Or if A and B are in a mutually supportive or symbiotic relationship, then each would be hurt by the other's removal. A number of authors have constructed models involving specific speciesspecies interactions, or "connections." If species i depends on species j , then the extinction of j may also lead to the extinction of i, and possibly give rise to cascading avalanches of extinction. Most of these connection models neither introduce nor have need of a fitness measure, barrier, viability, or tolerance for the survival of individual species; the extinction pressure on one species comes from the extinction of other species. Such a system still needs some underlying driving force to keep its dynamics from stagnating, but this can be introduced by making changes to the connections in the model, without requiring the introduction of any extra parameters.
Environmental Stress Models
Authors: Newman M. E. J. , Palmer R. G.
Published: November 2020

In chapters 2 to 4 we discussed several models of extinction which make use of ideas drawn from the study of critical phenomena. The primary impetus for this approach was the observation of apparent power-law distributions in a variety of statistics drawn from the fossil record, as discussed in section 1.2; in other branches of science such power laws are often indicators of critical processes. However, there are also a number of other mechanisms by which power laws can arise, including random multiplicative processes (Montroll and Shlesinger 1982; Sornette and Cont 1997), extremal random processes (Sibani and Littlewood 1993), and random barrier-crossing dynamics (Sneppen 1995). Thus the existence of power-law distributions in the fossil data is not on its own sufficient to demonstrate the presence of critical phenomena in extinction processes. Critical models also assume that extinction is caused primarily by biotic effects such as competition and predation, an assumption which is in disagreement with the fossil record. As discussed in section 1.2.2.1, all the plausible causes for specific prehistoric extinctions are abiotic in nature. Therefore an obvious question to ask is whether it is possible to construct models in which extinction is caused by abiotic environmental factors, rather than by critical fluctuations arising out of biotic interactions, but which still give power-law distributions of the relevant quantities. Such models have been suggested by Newman (1996, 1997) and by Manrubia and Paczuski (1998). Interestingly, both of these models are the result of attempts at simplifying models based on critical phenomena. Newman's model is a simplification of the model of Newman and Roberts (see section 3.6), which included both biotic and abiotic effects; the simplification arises from the realization that the biotic part can be omitted without losing the power-law distributions. Manrubia and Paczuski's model was a simplification of the connection model of Solé and Manrubia (see section 4.1), but in fact all direct species-species interactions were dropped, leaving a model which one can regard as driven only by abiotic effects. We discuss these models in turn. The model proposed by Newman (1996, 1997) has a fixed number N of species which in the simplest case are noninteracting.
Introduction
Authors: Cross Rob , Parker Andrew
Published: November 2020

Spend some time in most any organization today and you are sure to hear of the importance of networks, in one form or another, for getting work done. In this age of increasingly organic, flat, and flexible structures, many managers and scholars are using networks as a central organizing metaphor for twenty-first-century firms (e.g., Dimagio, 2001; Nohria & Ghoshal, 1997). In large part, this focus seems a product of two trends. First, over the past decade or so initiatives such as de-layering, TQM, reengineering, team-based structures, and outsourcing, to name a few, have been undertaken to promote organizational flexibility and efficiency (Hirschhorn & Gilmore, 1992; Hammer & Champy, 1993; Mohrman, Cohen, & Mohrman, 1995; Kerr & Ulrich, 1995). One outcome of these restructuring efforts is that information flow and work increasingly occur through informal networks of relationships rather than through channels tightly prescribed by formal reporting structures or detailed work processes. Along with the drive to more organic structures in organizations we have also seen a rise in the prevalence and value of knowledge-intensive work (Quinn, 1992; Drucker, 1993). Early initiatives to support knowledge workers focused heavily on databases and organizational processes to ensure the capture and sharing of lessons and reusable work products (e.g., Stewart, 1997; O’Dell & Grayson, 1998; Ruggles, 1998; Davenport, Delong, & Beers, 1998). However, these investments rarely, if ever, had the intended impact on the effectiveness and efficiency of knowledge work. As a result, a “second wave” of knowledge-management advice is coming forth that pays a great deal more attention to knowledge embedded within employees and relationships in organizations (e.g., Brown & Duguid, 2000; Cross & Baird, 2000; Dixon, 2000; Von Krogh et al., 2000; Cohen & Prusak, 2001). Among other things, this work has illustrated the importance of trust and informal networks for knowledge creation and sharing within organizations. We suggest that in today’s de-layered, knowledge-intensive settings, most work of importance is heavily reliant on informal networks of employees within organizations. For example, networks sitting across core work processes, weaving together new product development initiatives or integrating strategic initiatives such as alliances or mergers can be critical to organizational effectiveness.
Distributions of High-Frequency Stock-Market Observables
Authors: Osorio Roberto , Borland Lisa
Published: November 2020

Power laws and scaling are two features that have been known for some time in the distribution of returns (i.e., price fluctuations), and, more recently, in the distribution of volumes (i.e., numbers of shares traded) of financial assets. As in numerous examples in physics, these power laws can be understood as the asymptotic behavior of distributions that derive from nonextensive thermostatistics. Recent applications of the (Q-Gaussian distribution to returns of exchange rates and stock indices are extended here for individual U.S. stocks over very small time intervals and explained in terms of a feedback mechanism in the dynamics of price formation. In addition, we discuss some new empirical findings for the probability density of low volumes and show how the overall volume distribution is described by a function derived from q-exponentials. In March 1900 at the Sorbonne, a 30-year-old student—who had studied under Poincaré—submitted a doctoral thesis [2] that demonstrated an intimate knowledge of trading operations in the Paris Bourse. He proposed a probabilistic method to value some options on rentes, which were then the standard French government bonds. His work was based on the idea that rente prices evolved according to a random-walk process that resulted in a Gaussian distribution of price differences with a dispersion proportional to the square root of time. Although the importance of Louis Bachelier's accomplishment was not recognized by his contemporaries [24], it preceded by five years Einstein's famous independent, but mathematically equivalent, description of diffusion under Brownian motion. The idea of a Gaussian random-walk process (later preferably applied to logarithmic prices) eventually became one of the basic tenets of most twentieth-century quantitative works in finance, including the Black-Scholes [3] complete solution to the option-valuation problem—of which a special case had been solved by Bachelier in his thesis. In the times of the celebrated Black-Scholes solution, however, a change in perspective was already under way. Starting with the groundbreaking works of Mandelbrot [18] and Fama [11], it gradually became apparent that probability distribution functions of price changes of assets (including commodities, stocks, and bonds), indices, and exchange rates do not follow Bachelier's principle of Gaussian (or "normal") behavior.
Theories of Self-Interest and Collective Action
Authors: Monge Peter R. , Contractor Noshir
Published: November 2020

Many social theories are based on generative mechanisms that are directly relevant to the emergence and coevolution of human networks. Ironically, as Monge and Contractor (2001) demonstrate, many published network studies fail to acknowledge or explicitly identify the social theories and generative mechanisms that motivate their research. In much of the rest of this book we examine a number of social theories in order to identify their generative mechanisms. These mechanisms can be used in conjunction with others to populate the multitheoretical, multilevel framework for the realization of communication and other networks described in chapter 2. For example, the theory of social capital suggests that people who try to exploit social holes will do so by seeking to improve their structural autonomy. On the other hand, theories of social exchange suggest that individuals and organizations forge ties by exchanging material or information resources. Of course, it is quite possible that people do both at the same time, thus requiring a multitheoretical framework. If this were the case, we would develop multitheoretical hypotheses. These would predict that statistical p* analysis of observed networks would reveal significant components for structural autonomy, mutuality, and reciprocation. Further, we would expect that other possible network components, such as transitivity and cyclicality, which are generative mechanisms in other theories, would not be statistically significant in the realization of this particular observed network. In this chapter we examine theories of self-interest and theories of mutual interest, the latter sometimes called theories of collective action, in order to identify their theoretical mechanisms. The self-interest theories are the theory of social capital, specifically Burt’s theory of structural holes, and transaction cost economics. The theory of collective interest that we examine is public goods theory. Social theorists have long been fascinated by self-interest as a motivation for economic and other forms of social action (Coleman, 1986). Theories of self-interest postulate that people make what they believe to be rational choices in order to acquire personal benefits. The strong form of this theoretical mechanism, originally postulated by Adam Smith, is “rationality.” It stipulates that people attempt to maximize their gains, or equivalently, minimize their losses.
Estuarine Science and Biogeochemical Cycles
Authors: Bianchi Thomas S.
Published: November 2020

Estuaries are commonly described as semi-enclosed bodies of water, situated at the interface between land and ocean, where seawater is measurably diluted by the inflow of freshwater (Hobbie, 2000). The term “estuary,” derived from the Latin word aestuarium, means marsh or channel (Merriam-Webster, 1979). These dynamic ecosystems have some of the highest biotic diversity and production in the world. Not only do they provide a direct resource for commercially important estuarine species of fishes and shellfish, but they also provide shelter and food resources for commercially important shelf species that spend some of their juvenile stages in estuarine marshes. For example, high fish and shellfish production in the northern Gulf of Mexico is strongly linked with discharge from the Mississippi and Atchafalaya rivers and their associated estuarine wetlands (Chesney and Baltz, 2001). Commercial fishing in this region typically brings in 769 million kg of seafood with a value of $575 million. Fisheries production and coastal nutrient enrichment, via rivers and estuaries, are positively correlated within many coastal systems around the world (Nixon et al., 1986; Caddy, 1993; Houde and Rutherford, 1993). The coupling of physics and biogeochemistry occurs at many spatial scales in estuaries (figure 1.1; Geyer et al., 2000). Estuarine circulation, river and groundwater discharge, tidal flooding, resuspension events, and exchange flow with adjacent marsh systems (Leonard and Luther, 1995) all constitute important physical variables that exert some level of control on estuarine biogeochemical cycles. There has been considerable debate about the definition of an estuary because of the divergent properties found within and among estuaries from different regions of the world. Consequently, there have been numerous attempts to develop a comprehensive and universally accepted definition. Pritchard (1967, p. 1) first defined estuaries based on salinity as “semi-enclosed coastal bodies of water that have a free connection with the open sea and within which sea water is measurably diluted with fresh water derived from land drainage.” A general schematic representation of an estuary, as defined by Pritchard (1967), and further modified by Dalrymple et al. (1992) to include more physical and geomorphological processes, is shown in figure 1.2.
Sulfur Cycle
Authors: Bianchi Thomas S.
Published: November 2020

Sulfur (S) is an important redox element in estuaries because of its linkage with biogeochemical processes such as SO42− reduction (Howarth and Teal, 1979; Jørgensen, 1982; Luther et al., 1986; Roden and Tuttle, 1992, 1993a,b; Miley and Kiene, 2004), pyrite (FeS2) formation (Giblin, 1988; Hsieh and Yang, 1997; Morse and Wang, 1997), metal cycling (Krezel and Bal, 1999; Leal et al., 1999; Tang et al., 2000), ecosystem energetics (King et al., 1982; Howarth and Giblin, 1983; Howes et al., 1984), and atmospheric S emissions (Dacey et al., 1987; Turner et al., 1996; Simo et al., 1997). The range of oxidations for S intermediates formed in each of these processes is between +VI and −II. Many of the important naturally occurring molecular species of S are shown in table 12.1. On a global scale, most of the S is located in the lithosphere; however, there are important interactions between the hydrosphere, biosphere, and atmosphere where important transfers of S occur (Charlson, 2000). For example, coal and biomass burning, along with volcano emissions inject SO2 into the atmosphere, which can then be further oxidized in the atmosphere and removed as SO42− in rainwater (Galloway, 1985). An example of biogenic sulfur formation is the reduction of seawater SO42− to sulfide by phytoplankton and eventual incorporation of the S into dimethylsulfoniopropionate (DMSP). DMSP, in turn, is converted to volatile dimethyl sulfide (DMS; CH3SCH3)m which is emitted to the atmosphere. In the seawater, SO42− represents one of the major ions, with concentrations that range from 24 to 28 mM, which is considerably higher than the concentrations found in freshwaters (∼0.1 mM). This marked difference makes seawater the major input to estuaries and sets up an important gradient in estuarine biogeochemical cycling. In this chapter, the focus will be on the nonanthropogenic biogenic transformations of S that are relevant to biogeochemical cycling in estuarine and coastal waters. Approximately 50% of the global flux of S to the atmosphere is derived from marine emissions of DMS. Oxidation of DMS in the atmosphere leads to production of SO42− aerosols, which can influence global climate patterns (Charlson et al., 1987; Andreae and Crutzen, 1997).