bluuebunny/crossref_metadata_2025 huggingface dataset:
Valvular Heart Disease and Atrial Fibrillation
Authors: Becker Richard C. , Spencer Frederick A.
Published: November 2020

There are an estimated 250,000 heart valve replacement surgeries performed yearly on a worldwide basis. Mechanical prostheses have an excellent track record of durability (25 years or more), but current models require lifelong anticoagulation. Improved hemodynamics and reduced thrombogenicity characterize bioprosthetic valves; however, there is the disadvantage of degeneration, particularly in younger individuals. The ideal replacement—a tissue engineered “copy” of a native valve—is under development. The most feared and devastating complications of native or prosthetic valvular heart disease for patients, clinicians, and surgeons are valve thrombosis and systemic embolism. Although the incidence of thromboembolic events has decreased in North America in parallel with the reduced occurrence of rheumatic heart disease, this has not been the case in other parts of the world. Moreover, despite the improvements in design and surgical techniques, thromboembolism remains a serious complication of prosthetic heart valve replacement. The risk of thromboembolism in patients with native valvular heart disease is influenced strongly by the site of involvement, chamber dimension, ventricular performance, and presence of concomitant risk factors such as atrial fibrillation. Prior thromboembolism is considered a strong risk factor for recurrent events regardless of the valvular pathology. The risk of thromboembolism in patients with prosthetic valvular heart disease is recognized. Despite methodologic limitations, the available information derived from relatively large studies and an ever-expanding clinical experience allows several conclusions to be drawn: . . . • Thromboprophylaxis for mechanical prostheses is achieved most effectively with oral anticoagulants. . . . . . . • Antiplatelet therapy alone does not offer adequate protection for patients with mechanical prostheses. . . . . . . • The thrombogenicity of mechanical heart valves, from greatest to least, is as follows: caged ball > tilting disk > bileaflet. . . . . . . • High-risk patients (increased risk for thromboembolism) benefit from combination (anticoagulant and platelet antagonist) antithrombotic therapy. . . . . . . • A “threshold” level of anticoagulation is required for benefit. . . . . . . • High-intensity anticoagulation (international normalized ratio [INR] >3.5) increases the risk for hemorrhagic complications. . . . . . . • The risk of thromboembolism following bioprosthetic heart valve replacement is greatest during the first 3 postoperative months (Acar et al., 1996; Horstkotte et al., 1994; Sethia et al., 1986; Vogt et al., 1990). . . .
Venous Thromboembolism Treatment
Authors: Becker Richard C. , Spencer Frederick A.
Published: November 2020

The potential morbidity and mortality associated with venous thromboembolism (VTE) dictates rapid diagnosis and effective treatment. An understanding of basic anatomy permits a strategic approach to diagnosis and decisions regarding initial therapy. VTE can include the superficial or deep venous systems of the lower (most common) and upper extremities. Because deep vein thrombosis (DVT) of the proximal vessels (iliac, femoral veins) is associated with the greatest risk of pulmonary embolism (PE) (as well as chronic complications such as postphlebitic [thrombotic] syndrome), a proactive response, which may include anticoagulant therapy pending a definitive diagnosis, is recommended. Many DVTs begin in the calf veins and most, in all likelihood, resolve spontaneously. The probability of extension to the popliteal vein or above (where embolism is more likely) is determined by the prothrombotic environment. Proximal thrombi resolve slowly with anticoagulant therapy, and may be detectable in up to 50% of patients 1 year later. Approximately 10% of patients develop postphlebitic syndrome within 5 years—a complication from progressive valvular damage that increases in prevalence with recurrent events (Anderson et al., 1991). Approximately 10% of all PEs are rapidly fatal, and an additional 5% of patients die even after treatment is initiated. Up to 5% of patients develop pulmonary hypertension because of limited thrombus resolution (Kearon, 2003). The diagnosis of DVT and PE is difficult and requires a mixture of clinical suspicion and objective testing. A complete history with attention to specific symptoms and signs should be recorded; a thorough family history is also invaluable. The laboratory evaluation is critical in establishing an unequivocal diagnosis, but most of the tests currently used are not of uniform high sensitivity and specificity. Thus, an accurate diagnosis requires experience and attention to detail. The cardinal symptoms of DVT are pain and swelling in the lower extremity. The pain may be sharp and sudden in onset or come on more gradually and be reported as restricting in character. There may be little or no swelling, or the entire lower extremity may be markedly enlarged. On examination, there is frequently reddish-purple discoloration of the leg in comparison with the noninvolved side.
Platelet Antagonists
Authors: Becker Richard C. , Spencer Frederick A.
Published: November 2020

Antithrombotic and fibrinolytic drugs impair normal hemostasis and, as a result, increase the risk for hemorrhage. It is important to consider that many treatment strategies include agents of differing classes (platelet antagonists, anticoagulants, fibrinolytics) and categories (aspirin, clopidogrel, glycoprotein [GP] IIb/IIIa receptor antagonists), creating a multisite and/or hemostatic phase defect. Platelet antagonists, by impairing primary hemostasis, are associated most often with hemorrhage involving the skin and mucous membranes; however, the gastrointestinal and genitourinary tracts may occasionally be involved. Fixed-dose unfractionated heparin (UFH) therapy is a modifiable risk factor associated with hemorrhage in patients receiving GPIIb/IIIa receptor antagonists. The Evaluation of c7E3 Fab in Preventing Ischemic Complications of High-Risk Angioplasty (EPIC) trial was a prospective, randomized, placebo-controlled trial examining the efficacy of treatment with abciximab (EPIC Investigators, 1994). A total of 2,099 patients were scheduled for coronary angioplasty or direct atherectomy and were considered to be at high risk for abrupt closure. The primary composite endpoint of the study at 30 days was death from any cause, nonfatal myocardial infarction (MI), coronary artery bypass grafting (CABG) or repeat percutaneous coronary intervention (PCI), or placement of an intraaortic balloon pump to relieve refractory ischemia. All patients received therapy with 325 mg of aspirin and bolus dosing of UFH between 10,000 and 12,000 U followed by additional boluses of 3,000 U every 15 minutes to maintain an activated clotting time (ACT) between 300 and 350 seconds. Patients were randomized to receive either abciximab 0.25 mg/kg as a bolus followed by placebo infusion, or a placebo bolus and infusion. A significant increase in the incidence of major hemorrhage was demonstrated in patients receiving abciximab bolus and infusion compared to placebo bolus and infusion. A total of 14% of patients receiving abciximab bolus and infusion experienced a major bleeding complication as compared to 7% in the placebo bolus and infusion group (p = .001). Analysis of major hemorrhage in patients treated with abciximab bolus and infusion as a function of UFH dose revealed a dose-dependent increased risk.
Random Searches
Authors: Wei James
Published: November 2020

The reverse search starts from a set of desired properties and asks for substances that possess them. Theoretical knowledge and past experience should be relied upon to suggest where to look, since it is the fastest and least expensive approach. When theoretical knowledge and past experience have been exhausted, then random searches may be the only way to make progress, if the problem is sufficiently important and there is enough budget and patience. Table 7.1 compares some of the requirements and the pros and cons of the guided search and the random search The best strategy on how to spend resources of time and money most efficiently can be considered a problem in operations research, under the topic of “optimal resource allocation.” The best way to use the limited resources of money and time effectively may be a mixed strategy, with some guided and some random searches. Even a random search has to start somewhere. At the beginning, there should be a plan on what territories to cover and how to cover them. The plan can be deterministic, which is completely planned out in advance and executed accordingly. The plan can also be adaptive: after the arrival of each batch of results and preliminary evaluations, the plan would evolve to take advantage of the new information and understanding gained. Even a random search must begin at a starting point and stake out the most promising directions for initial explorations. In most cases, there is a lead compound that has some of the desired properties, but which is deficient in others, and serves as the starting point of the random search to find better compounds in this neighborhood. The historic cases in section 1.2 involve the modification of an existing product, such as vulcanizing raw rubber and adding an acetyl group to salicylic acid. One explores around the lead compound by using small amounts of additives, blending with other material, changing processing conditions and temperature, and changing structure by chemical reactions.
Self-Organized Critical Models
Authors: Newman M. E. J. , Palmer R. G.
Published: November 2020

The models discussed in the last chapter are intriguing, but present a number of problems. In particular, most of the results about them come from computer simulations, and little is known analytically about their properties. Results such as the power-law distribution of extinction sizes and the system's evolution to the "edge of chaos" are only as accurate as the simulations in which they are observed. Moreover, it is not even clear what the mechanisms responsible for these results are, beyond the rather general arguments that we have already given. In order to address these shortcomings, Bak and Sneppen (1993; Sneppen et al. 1995; Sneppen 1995; Bak 1996) have taken Kauffman's ideas, with some modification, and used them to create a considerably simpler model of large-scale coevolution which also shows a power-law distribution of avalanche sizes and which is simple enough that its properties can, to some extent, be understood analytically. Although the model does not directly address the question of extinction, a number of authors have interpreted it, using arguments similar to those of section 1.2.2.5, as a possible model for extinction by biotic causes. The Bak-Sneppen model is one of a class of models that show "self-organized criticality," which means that regardless of the state in which they start, they always tune themselves to a critical point of the type discussed in section 2.4, where power-law behavior is seen. We describe self-organized criticality in more detail in section 3.2. First, however, we describe the Bak-Sneppen model itself. In the model of Bak and Sneppen there are no explicit fitness landscapes, as there are in NK models. Instead the model attempts to mimic the effects of landscapes in terms of "fitness barriers." Consider figure 3.1, which is a toy representation of a fitness landscape in which there is only one dimension in the genotype (or phenotype) space. If the mutation rate is low compared with the time scale on which selection takes place (as Kauffman assumed), then a population will spend most of its time localized around a peak in the landscape (labeled P in the figure).
Constraints on the Interactive Organization as an Ideal Type
Authors: Krackhardt David
Published: November 2020

Expressed in the theme of this book [C. Hecksher and A. Donnellon, The Post Bureaucratic Organization, the book from which this chapter is reproduced] is a hope, a desire for a better organization than the one we have experienced for generations, the infamous bureaucracy. I am sympathetic with this hope. All of us who have studied organizations have encountered the debilitating effects of bureaucratic forms, whether managed well or not. And progress is made, as the Kennedy quote in the epigraph suggests, by dreamers who are willing to let go of the way of the past and peer into the neverland of what could be. Dreams motivate. They liberate us from the institutional constraints of history and social inertia so that we can explore new, unimaginable landscapes. But dreams also conveniently leave out the obstacles and problems that reality so rudely interjects. Thus, dreams do not guarantee success. And although the last two words “Why not” from the above quote are presumably rhetorical, one could take them literally and suggest that dreams should be scrutinized for loopholes. The answer to the question. “Why not?” may just be, “Because it won’t work.” It is not my purpose here to prejudge the viability of the post bureaucratic form. But, if it is to succeed, we must explore the obstacles to its evolution, the possible constraints to its existence. If we can anticipate the sources of resistance to its survival, we will have a better chance of nurturing it along until it can predominate among its alternatives. This chapter is built around two questions: (1) Can the ideal post bureaucratic form exist? and (2) If it could exist, would we want it to? The characteristics of interactive forms are described in the Heckscher- Applegate “Introduction” and narrowed down in the Heckscher chapter “Defining the Post-Bureaucratic Type” [in The Post-Bureaucratic Organization]. Although I see differences in the various chapters about what ideal type might entail, there are characteristics that emerge as dominant in this proposed form. Foremost among these defining characteristics is the reliance on informal relations, or associations, that cut across, or perhaps replace, formal channels established by the organization.
Effective Complexity
Authors: Gell-Mann Murray , Lloyd Seth
Published: November 2020

It would take a great many different concepts—or quantities—to capture all of our notions of what is meant by complexity (or its opposite, simplicity). However, the notion that corresponds most closely to what we mean by complexity in ordinary conversation and in most scientific discourse is "effective complexity." In nontechnical language, we can define the effective complexity (EC) of an entity as the length of a highly compressed description of its regularities [6, 7, 8]. For a more technical definition, we need a formal approach both to the notion of minimum description length and to the distinction between regularities and those features that are treated as random or incidental. We can illustrate with a number of examples how EC corresponds to our intuitive notion of complexity. We may call a novel complex if it has a great many different characters, scenes, subplots, and so on, so that the regularities of the novel require a long description. The United States tax code is complex, since it is very long and each rule in it is a regularity. Neckties may be simple, like those with regimental stripes, or complex, like some of those designed by Jerry Garcia. From time to time, an author presents a supposedly new measure of complexity (such as the "self-dissimilarity" of Wolpert and Macready [17]) without recognizing that when carefully defined it is just a special case of effective complexity. Like some other concepts sometimes identified with complexity, the EC of an entity is context-dependent, even subjective to a considerable extent. It depends on the coarse graining (level of detail) at which the entity is described, the language used to describe it, the previous knowledge and understanding that are assumed, and, of course, the nature of the distinction made between regularity and randomness. Like other proposed "measures of complexity," EC is most useful when comparing two entities, at least one of which has a large value of the quantity in question.
Sources and Distribution of Sediments
Authors: Bianchi Thomas S.
Published: November 2020

The uplift of rocks above sea level on the Earth’s surface over geological time, produces rock material that can be altered into soils and sediments by weathering processes. Over geological time, a fraction of sediments can be sequestered for storage in the ocean basins—with most of it stored in the coastal margin. However, much of this material is modified via processing in large river estuarine systems which can ultimately affect the long-term fate of these terrigenous materials. Sediments produced from weathering of igneous, metamorphic, and sedimentary rocks are principally transported to the oceans through river systems of the world. The major routes of sediment transport from land to the open ocean can simply be illustrated through the following sequence: streams, rivers, estuaries, shallow coastal waters, canyons, and the abyssal ocean. It should be noted that significant and long-term storage occurs in river valleys and floodplains (Meade, 1996). Submarine canyons are also thought to be temporary storage sites for land-derived sediments; however, episodic events such as turbidity currents and mud slides can move these sediments from canyons to the abyssal ocean (more details on coastal margin transport to the deep ocean are provided in chapter 16). The annual sediment flux from rivers to the global ocean is estimated to range from 18 to 24 × 109 metric tonnes (Milliman and Syvitski, 1992). Conversely, estuaries will eventually fill-in with fluvial inputs of sediments over time, and ultimately reach an equilibrium whereby export and import of sediment supply are balanced (Meade, 1969). For example, recent studies have shown that sediment accumulation in the Hudson River estuary, both short (Olsen et al., 1978) and long term (Peteet and Wong, 2000), is in equilibrium with sea level rise. More specifically, it is believed that river flow controls the direction of sediment flux in the Hudson, while variations in spring-neap tidal amplitude control the magnitude (Geyer et al., 2001). Weathering is typically separated into two categories: physical and chemical. Physical weathering involves the fragmentation of parent rock materials and minerals through processes such as freezing, thawing, heating, cooling, and bioturbation (e.g., endolithic algae, fungi, plant roots, and earthworms).
The Antiquarians
Authors: Fagan Brian
Published: November 2020

“Time we may comprehend,” wrote the English physician Sir Thomas Browne in 1643. “’Tis but five days older than ourselves.” Browne’s view of the past encompassed the Greeks and Romans and a humankind created by God in the Old Testament. Also in the seventeenth century, Archbishop James Ussher of Armagh in Ireland used the long genealogies in the Scriptures to calculate that the world had been created on the evening of October 22, 4004 B.C. Thus, according to Christian dogma, the entire span of human existence was a mere six thousand years. After the collapse of the Roman Empire, the study of the past fell into oblivion. Babylon reverted to desert; Petra slumbered in its secluded canyon. Ancient ruins of any kind were a curiosity, often thought to be the work of giants. With the Renaissance came a renewed interest in classical learning and in the remains of ancient civilizations. Thomas Browne and his English contemporaries were steeped in knowledge of ancient Greece and Rome. The Renaissance was an age of collectors and scholars, of acquisitive cardinals and nobles who flocked to Mediterranean lands and returned laden with antiquities for their private collections and for what were then known as “cabinets of curiosities.” Soon, a stream of young travelers followed in their footsteps to Italy, taking what became known as the “grand tour” as part of their education (see Chapter 3). Such often frivolous travelers became the first archaeological tourists, but not necessarily the most perceptive. By 1550, it was fashionable to be an antiquary, a collector or student of ancient things. But only the wealthiest traveler could afford a grand tour and could pay for classical treasures. The less affluent indulged their passion for the past at home, collecting Roman coins and inscriptions and, above all, traveling the countryside in pursuit of what the English schoolmaster William Camden (1551–1623) called “the backward-looking curiosity.” This open-ended inquisitiveness took Camden and his contemporaries to eroded burial mounds on windy uplands, to ancient fortifications in Denmark, and to the mysterious stone circles known as Stonehenge.
Greece Bespoiled
Authors: Fagan Brian
Published: November 2020

The grand tour took the young and wealthy to Rome and Naples, but not as far as Greece, which had sunk into oblivion under its Byzantine emperors, who began to rule in A.D. 527. For seven hundred years Greece remained masked in obscurity as Crusaders, Venetians, and then Turks established princedoms and trading posts there. The Turks entered Athens in 1455 and turned the Parthenon and Acropolis into a fortress, transforming Greece into a rundown province of the Ottoman Empire. Worse yet, the ravages of wind, rain, and earthquake, of villagers seeking building stone and mortar, buried and eroded the ancient Greek temples and sculptures. Only a handful of intrepid artists and antiquarians came from Europe to sketch and collect before 1800, for Greek art and architecture were still little known or admired in the West, overshadowed as they were by the fashion for things Roman that dominated eighteenth-century taste. A small group of English connoisseurs financed the artists James Stuart and Nicholas Revett on a mission to record Greek art and architecture in 1755, and the first book in their multivolume Antiquities of Athens appeared in 1762. This, and other works, stimulated antiquarian interest, but in spite of such publications, few travelers ventured far off the familiar Italian track. The Parthenon was, of course, well known, but places like the oracle at Delphi, the temple of Poseidon at Sounion—at the time a pirates’ nest— and Olympia were little visited. In 1766, however, Richard Chandler, an Oxford academic, did visit Olympia, under the sponsorship of the Society of Dilettanti. The journey took him through overgrown fields of cotton shrubs, thistles, and licorice. Chandler had high expectations, but found himself in an insect-infested field of ruins: Early in the morning we crossed a shallow brook, and commenced our survey of the spot before us with a degree of expectation from which our disappointment on finding it almost naked received a considerable addition. The ruin, which we had seen in evening, we found to be the walls of the cell of a very large temple, standing many feet high and well-built, its stones all injured . . .
Soil Nutrient Deficiencies in an Area of Endemic Osteoarthritis (Mseleni Joint Disease) and Dwarfism in Maputoland, South Africa
Authors: Pooley Justin , Fey Martin
Published: November 2020

Unusually high incidences of dwarfism and an endemic osteoarthritis, called Mseleni Joint Disease (MJD), occur on the flat, sandy coastal plain of Maputaland. This rare disease begins with stiffness and pain in the joints and progresses to varying degrees of disability, with some of the afflicted requiring aid in walking and others completely immobile. Almost 3% of local adults are dwarfs, while 38% of women and 11% of men have MJD (Fellingham 1973, Lockitch 1974). Medical studies since the 1970s have examined hematological, radiological, mycotoxicological, and genetic factors, and made comparisons with other diseases (Ballo 1996, Burger 1973, Lockitch 1973, Marasas 1986), yet have been fruitless in determining the etiology of MJD or the dwarfism. Dwarfism has been linked to Zn deficiencies in other areas and several bone-related disorders have been associated with P, Ca, and Mg deficiencies (Hidiroglou 1980). Calcium, Mg, Mn, and F deficiencies have all been speculated as possible causative factors of MJD (Fincham 1981, 1986), and the possibility of soil-derived nutrient deficiencies within this landscape is addressed. Maputaland is located on the northeast corner of South Africa, occupying an area about 50 by 100 km. It has a warm, subtropical climate, with summer rainfall occurring as cyclonic events, and varying from 1000 mm at the coast to 600 mm near Mseleni. Summer temperatures are high, averaging 29° C, and winters mild at 17° C. The region has high floral and faunal diversity and endemism (van Wyk 1996), and contains 15 major vegetation zones. Geologically, Maputaland is covered with recent Quaternary sands, with several north-south paleodune cordons parallel to the coast. There is little relief and, besides the coastal dunes reaching almost 200 m above mean sea level, the average elevation is 100 m. No rivers cross the plain, but groundwater is frequently exposed at the surface, as evidenced by Lake Sibayi and the numerous pans in the region. Soils are mostly the Waterton family of the Fernwood form (thermic, coated Typic Quartzipsamments) (SCWG 1991, USDA 1999). These sands are inherently infertile, vary in pH from neutral to acidic, have a low cation exchange capacity, low organic matter content, and are dominated in the clay fraction by kaolinite.
Introduction
Authors: Hibbert D. Brynn , Gooding J. Justin
Published: November 2020

• To understand that chemical measurements are made for a purpose, usually to answer a nonchemical question. • To define measurement and related terms. • To understand types of error and how they are estimated. • What makes a valid analytical measurement…. Chemistry, like all sciences, relies on measurement, yet a poll of our students and colleagues showed that few could even start to give a reasonable explanation of ‘‘measurement.’’ Reading textbooks on data analysis revealed that this most basic act of science is rarely defined. Believe it or not there are people that specialize in the science of measurement: a field of study called metrology. The definition used in this book for measurement is a ‘‘set of operations having the object of determining the value of a quantity.’’ We will come back to this but first . . . The world spent an estimated US$3.1 billion on chemical measurements for medical diagnosis in 1998, most of this measurement being done in the United States and the European Union. These measurements were carried out to discover something about the patients. The sequence of events that involve a chemical measurement are: (1) state the real-world problem; (2) decide what chemical measurement can help answer that problem; (3) find a method that will deliver the appropriate measurement; (4) do the measurement and obtain a result (value and uncertainty, including appropriate units); and (5) give a solution to the problem based on the measurement result. It is important to understand the relationship between the real-world problem and the proposed measurement. The chemical measurement may give only part of the answer, and should not be confused with the answer itself. In forensic analytical chemistry, matching a suspect’s DNA with DNA sampled at the crime scene does not necessarily mean that the suspect is guilty. In health care, a cholesterol measurement might tell the doctor about the likelihood of a patient contracting heart diesease, but a full analysis of high- and low-density lipids and other fats will be more useful.
Describing Data: Means and Confidence Intervals
Authors: Hibbert D. Brynn , Gooding J. Justin
Published: November 2020

• To understand the concept of mean, variance, and standard deviation pertaining both to a large sample (population) and a small sample. • To define the standard deviation of the mean of a number of repeated measurements and understand its relation to the sample standard deviation. • To define confidence intervals about a mean and show how to use them to indicate measurement precision. • To introduce robust estimators of representing the average and sample standard deviation. • To appreciate the difference between measurement repeatability and reproducibility…. Why do we bother with means and standard deviations? Because these two statistics tell us a great deal about the data and the population from which they come. A mean of a number of repeated measurements of the concentration of a test solution is an estimate of the concentration of the test solution and the sample standard deviation gives a measure of the random scatter of the values obtained by measurement. Together with the appropriate units they represent the result. This information is not necessarily the answer to: ‘‘What is the concentration of the test solution and how sure are you of that answer?’’ To answer this question an uncertainty budget must be prepared, which includes errors, random and systematic, arising from all aspects of the experiment (of which the standard deviation of repeated measurements is just one). Why is it good to repeat analytical measurements? There might be an argument for the ‘‘quit while you are ahead’’ school but repeating a measurement gives increased confidence in the result, especially if the numbers appear to agree. But apart from the appearance of consistency, do you get better answers by repeating measurements, and are more repeats better than fewer repeats? The answer to both questions is ‘‘yes,’’ as we shall see in this chapter. Note that the statistical treatment of repeated results does not tell us about systematic error unless we can compare our mean with a known or assigned value of the quantity being measured.
Calibration
Authors: Hibbert D. Brynn , Gooding J. Justin
Published: November 2020

• To describe the linear calibration model and how to estimate uncertainties in the calibration parameters and test concentrations determined from the model. • To show how to perform calibration calculations using Excel. • To calculate parameters and uncertainties in the standard addition method. • To calculate detection limits from measurements of blanks and uncertainties of the calibration model.… Calibration is at the heart of chemical analysis, and is the process by which the response of an instrument (in metrology called ‘‘indication of the measuring instrument’’) is related to the value of the measurand, in chemistry often the concentration of the analyte. Without proper calibration of instruments measurement results are not traceable, and not even correct. Scales in supermarkets are periodically calibrated to ensure they indicate the correct mass. Petrol pumps and gas and electric meters all must be calibrated and recalibrated at appropriate times. A typical example in analytical chemistry is the calibration of a GC (gas chromatography) analysis. The heights of GC peaks are measured as a function of the concentration of the analyte in a series of standard solutions (‘‘calibration solutions’’) and a linear equation fitted to the data. Before the advent of computers, a graph would be plotted by hand and used for calibration and subsequent measurement. Having drawn the best straight line through the points, the unknown test solution would be measured and the peak height read across to the calibration line then down on to the x-axis to give the concentration (figure 5.1). Nowadays, the regression equation is computed from the calibration data and then inverted to give the concentration of the test solution. Although the graph is no longer necessary to determine the parameters of the calibration equation, it is good practice to plot the graph as a rapid visual check for outliers or curvature. Because we can choose what values the calibration concentrations will take, the concentration is the independent variable, with the instrumental output being the dependent variable (because the output of the instrument depends on the concentration).
Livestock Early Warning System for Africa’s Rangelands
Authors: Stuth Jerry W. , Angerer Jay
Published: November 2020

Rangelands in Africa (i.e., grasslands, savannas, and woodlands, which contain both grasses and woody plants) cover approximately 2.1 × 109 ha. Africa’s livestock population of about 184 million cattle, 3.72 million small ruminants (sheep and goats), and 17 million camels extract about 80% of their nutrition from these vast rangelands (IPCC, 1996). Rangelands have a long history of human use and are noted for great variability in climate and frequent drought events. The combination of climatic variability, low ecological resilience, and human land use make rangeland ecosystems more susceptible to rapid degeneration of ecosystems. From a land-use perspective, there are differences between West Africa and East Africa in rangelands use. In arid and semiarid areas of West Africa (rainfall 5–600 mm), millet (or another crop) is planted over a unimodal (one peak in rainfall per year) rainy season (three to four months); then fields remain fallow during the dry season, ranging from eight to nine months. Livestock eat crop residues. Land use is dominated by cultivation, with livestock playing a subsidiary role in the village economy. In East Africa, by contrast, areas with higher rainfall (up to 600 mm) are inhabited by pastoralists rather than farmers. In dry parts, cultivation occurs mainly where irrigation is possible or where water can otherwise be sequestered and stored for cropping. Rainfall is bimodal (two peaks in rainfall per year) in most rangelands, resulting in two growing seasons. As much as 85% of the population live and depend on rangelands in a number of countries in Africa. With emerging problems associated with the increasing population, the changes in key production areas, and the prevalence of episodic droughts and insecurity due to climatic change and ecological degradation and expansion of grazing territories, the traditional coping strategies of farmers, ranchers, and pastoralists have become inappropriate. More uncertainties require new innovations in characterizing, monitoring, analyzing, and communicating the emergence of drought to allow pastoral communities to cope with a rapidly changing environment. To this end, the United States Agency for International Development (USAID) awarded the Texas A&M University System an assessment grant to develop a Livestock Early Warning System (LEWS) as part of the Global Livestock Collaborative Research Support Program.
Agricultural Drought in Bangladesh
Authors: Ahmed Ahsan U. , Iqbal Anwar
Published: November 2020

Bangladesh is globally known as a flood-vulnerable country—an almost flat land with too much water. In terms of annual per capita availability of water resources, it ranks among the highest in the world. But a lesserknown disaster that affects a significant proportion of its fertile land is drought. The occurrence of droughts may largely be attributed to two recent phenomena: (1) an extensive adoption of high yielding varieties (HYV) of paddy (i.e., rice) in the drier months; and (2) constraints faced in water availability during premonsoon months due to upstream water withdrawal from river systems. Up to 15% of the total cultivable land (about 0.9 million ha) now experiences droughts of moderate to very severe intensity, once in every two years (Iqbal and Ali, 2001). This chapter examines the causes of droughts in the context of the country’s complex water regime, the implications of droughts, and the ways to monitor them. About 80% of annual monsoon rainfall over the country occurs during the period from June to the first week of October. The western zones of the country receive less rainfall, averaging about 1400 mm, compared to the national average of 2150 mm, and therefore the susceptibility to droughts in the western zones of the country is higher. Table 24.1 provides a chronological overview of areas and populations in Bangladesh affected by droughts during the 1950–79 period. The economy of Bangladesh significantly depends on agriculture. More than 63% of 130 million people, confined within a territory of 147,750 km2, find employment in agriculture (MOF, 2003). Although the share of the crop production in the gross domestic product (GDP) has been declining steadily in recent times, dropping from 24.66% in 1990–91 to 18.58% in 2002–03, it still is the predominant economic activity of the majority of the people (Ahmad and Ahmed, 2002). More than 80% of the households in rural Bangladesh are directly dependent on the production of various crops. Paddy (rice) is the main crop, occupying about 80% of the cultivated land. Multiple varieties of paddy are grown in the country.
Serpentine Geoecology of Western North America
Authors: Alexander Earl B. , Coleman Roger G. , Keeler-Wolfe Todd , Harrison Susan P.
Published: November 2020

Geoecology is a fruitful interdisciplinary field, relating rocks to soils to plant and animal communities and studying the interactions between them. Modern geoecology especially concentrates on showing how geology and soils affect the structure, composition, and distribution of plant communities in a certain research area. This book applies the principles of geoecology to Western North America, and to a specific kind of rock, the fascinating serpentine belts that run along the continental margins of the West Coast from Alaska to Baja. The authors come from different disciplines: Alexander is a soil scientist, Coleman a geologist, Harrison a biological researcher, and Keeler-Wolfe a vegetation ecologist. It begins with an overview of the geology of this rock and this region, covering mineralogy, petrology, and stratigraphy of West Coast serpentine. It will continue with serpentine soils and their development and distribution, and serpentine effects on plants and vegetation and animals. The serpentine geoecology of the different regions of Western North America, concentrating on California, will conclude the study. So, this academic book should appeal to plant ecologists, soil scientists, researchers in geoecology, and students in advanced courses in soil science.
Mineralogy and Petrology of Serpentine
Authors: Alexander Earl B. , Coleman Roger G. , Keeler-Wolfe Todd , Harrison Susan P.
Published: November 2020

“Serpentine” is used both as the name of a rock and the name of a mineral. Mineralogists use “serpentine” as a group name for serpentine minerals. Petrologists refer to rocks composed mostly of serpentine minerals and minor amounts of talc, chlorite, magnetite, and brucite as serpentinites. The addition of “-ite” to mineral names is common practice in petrologic nomenclature. For instance, quartzite is a name for a rock made up mostly of quartz. Serpentinites are rocks that form as a result of metamorphism or metasomatism of primary magnesium–iron silicate minerals. This entails the replacement of the primary silicate minerals by magnesium silicate serpentine minerals and the concentration of excess iron in magnetite. “Mafic” is a euphonious term derived from magnesium and ferric that is used for dark colored rocks rich in ferromagnesian silicate minerals. “Ultramafic” is used when the magnesium–ferrous silicate minerals compose >90% of the total rock. Olivine, clinopyroxene, and orthopyroxene are the minerals in primary ultramafic rocks, with minor amounts of plagioclase, amphibole, and chromite. Ultrabasic has been used by some geologists in referring to ultramafic rocks. The most common ultramafic rocks are harzburgite, containing <75% olivine and 25% orthopyroxene; dunite, with 100% olivine; and lherzolite, which has 75% olivine, 15% orthopyroxene, and >10% clinopyroxene, with or without plagioclase. Very small amounts of chromite are present in all of the mantle ultramafic rocks (Coleman 1971). The alteration of primary ultramafic rocks to serpentine mineral assemblages is incremental due to episodic invasion of water into the ultramafic rock. It is difficult to distinguish and map the gradations from primary ultramafic rock to serpentinite. Because of this difficulty in distinction, we prefer to use the term ultramafic or serpentinized peridotite for all gradations to serpentinite. Pedologists and botanists commonly group serpentinites with primary ultramafic rocks and refer to these substrates as serpentine because all of them have similar chemical compositions. As will become apparent later, there is great variability in the mineralogical compositions of these rocks and the soils derived from them.
Animals, Fungi, and Microorganisms
Authors: Alexander Earl B. , Coleman Roger G. , Keeler-Wolfe Todd , Harrison Susan P.
Published: November 2020

Although plants are the major living components of terrestrial geoecosystems, other organisms are very important. Some animals move large amounts of soil, and many microoganisms promote the weathering of rocks and minerals in soils. Perhaps the greatest effects of animals, fungi, and microorganisms on geoecosystems are indirect through their effects on plants and plant communities. Mycorrhizal fungi are beneficial to plants in nutrient-limiting substrates where the fungi can scavenge phosphorous and nitrogen for plants. Many animals, from large ungulates (moose, elk, deer, etc.) to microscopic nematodes, graze on the leaves and roots of plants. Microorganisms cause many diseases in plants. A complete inventory of plant interactions with other organisms is virtually limitless. This chapter concentrates on organisms that live in serpentine soils, that live on ultramafic rocks, or that are dependent on plants that grow on serpentine soils. There have been few field investigations of living organisms, other than plants, on serpentine soils. Many of the investigations on animals, fungi, and microorganisms in serpentine soils of the western North America have been conducted on Jasper Ridge in San Mateo County, and some have been on Coyote Ridge in Santa Clara County and on the McLaughlin Reserve in Napa and Lake counties, California. Some investigations of animals and other organisms for which there are no published accounts relating to serpentine soils in western North America (e.g., termites) are cited from other areas. The associations of organisms with serpentine soils, whether utilization or avoidance, largely depend on the chemistry of the soil parent materials. Therefore, this chapter begins with a review of the effects of serpentine chemistry on living organisms. Organisms are about 50% or more water. Moss plants that are less than 50% water when desiccated can absorb much more water than their dry weights to increase their weights several fold within hours. About half of the biomass of living organisms that is not water is carbon. Other than water, carbon dominates the chemistry of all organisms. It forms large polymers that are far beyond the capabilities of other elements. Carbon dioxide in the atmosphere is the primary source of carbon in soils.
Southern California Coast Ranges, Domain 3
Authors: Alexander Earl B. , Coleman Roger G. , Keeler-Wolfe Todd , Harrison Susan P.
Published: November 2020

The Southern California Coast Range domain is a mountainous region with subparallel ridges aligned north–south, or more precisely north, northwest–south, southeast, and with intervening valleys that are controlled by strike-slip faulting. It extends about 400 km from the Golden Gate at the entrance to San Francisco Bay south to the Transverse Ranges that have east–west trending ridges. The domain corresponds to a physiographic region about 400 km long and 100 km wide that is bound by the Pacific Ocean on the west, the Great Valley of California on the east, on the north by the drainage outlet of the Sacramento and San Joaquin Rivers through the Carquinas Straight and San Pablo Bay, and on the south by the Transverse Ranges. Ridges in the Southern California Coast Ranges generally have nearly level crests (Page et al. 1997), but they range considerably in height up to about 1500 m on some of the higher peaks. No streams from the Great Valley cross the Southern California Coast Ranges to the Ocean; the Great Valley drains through the Carquinez Straight and Golden Gate at the north end of these ranges. The larger streams in the Southern California Coast Ranges drain from the Santa Clara Valley, Salinas Valley, and Cuyama Valley to the San Francisco, Monterey, and San Luis Obispo bays. Only relatively small streams drain to the Great Valley, but some of them have large alluvial fans in the valley. There are many Tertiary-faultbound valleys and basins among the mountain ranges. Some of the more prominent basins are the Santa Maria basin, Carrizo Plains, Paso Robles basin, and Watsonville basin. Serpentine is scattered in relatively small bodies throughout the domain and is concentrated along some of the major faults and in the New Idria area (locality 3-12). Climates range from cool and foggy along the coast to warm inland, with hot and dry summers inland from the fog belt.
Klamath Mountains, Domain 5
Authors: Alexander Earl B. , Coleman Roger G. , Keeler-Wolfe Todd , Harrison Susan P.
Published: November 2020

Domain 5 has mountains on the west aligned in broad arcs; in the eastern Klamath Mountains this arcuate pattern is not as evident. The outer arc curves from the triple junction of the California Coast Ranges, Great Valley, and Klamath Mountains in western Tehama County around through Del Norte County, where it is within a few kilometers of the Pacific Ocean, to Douglas County in Oregon. This western edge of the Klamath Mountains marks a boundary with the California Coast Ranges. The eastern edge of the Klamath Mountains forms a boundary with the Cascade Mountains. The southern, or southeast, boundary is where sediments of the Great Valley lap over the Klamath Mountains in Shasta and western Tehama counties. Serpentine rocks are more extensive in the Klamath Mountains than in any other domain or physiographic province in North America. Through the middle of the Tertiary, the Klamath Mountains were eroded to a nearly level plain called the Klamath peneplain (Diller 1902). According to Diller, the Klamath peneplain and the submerged coastal area that had been accumulating sediments were uplifted slightly during the Miocene, and erosion reduced the northern California Coast Ranges to a nearly level plain which he called the Bellsprings peneplain, noting that it is practically continuous with the Klamath peneplain. Subsequently discovered sediments of the Weaverville formation were deposited in a depression, or graben, in the Klamath Mountains during the Oligocene, indicating that uplift of the Klamath peneplain must have begun during the Paleogene, before the Miocene. Uplift was intermittent, allowing time for the erosion of broad valleys in less resistant rocks between episodes of uplift. Concordant summits, or mountains with summits of nearly equal elevation, are the evidence that led Diller (1902) to suspect a former peneplain. Although the mountain summits in any particular area are nearly equal or subequal, there is a general increase in summit elevation from the coast inland to 2.5–2.7 km. The altitude of Mt. Eddy on the eastern edge of the Klamath Mountains is 2751 m and that of Mt.