bluuebunny/crossref_metadata_2025 huggingface dataset:
Whose Water and Whose City? Towards an Emancipatory Water Politics
Authors: Swyngedouw Erik
Published: November 2020

Urban water is part and parcel of the political ecology of power that structures the functioning of the city. The preceding chapters showed how the circulation of water, the most natural of goods, is inserted into the maelstrom of social power relations through which the urbanization process unfolds. The urbanization of water and the urban hydrosocial cycle on which the sustainability of the city depends is impregnated by myriad social, cultural, political, and economic meanings and powers that place control over and access to nature squarely within the realm of key moral and ethical questions. In particular, it raises the issue of the relationship between nature, social justice, and the city. While the city cannot exist without the perpetual metabolic transformation of nature, this very transformation turns nature into a deeply social process in which nature, society, and the city can no longer be separated. It also suggests, of course, that some key questions need to be asked with respect to the social and material construction of the city’s nature and the power relationships through which this transformation and urban metabolism is organized and maintained. In this vein, we have attempted to explain how a political ecological analysis permits casting a new and different light onto the socio-ecological metabolic dynamics of the urbanization process itself. The previous chapters indicated that this urban transformation of water is a manifestation and expression of wider relations that clearly transcend the simple question as to who does and who does not have access to water. It also suggested that the water problem is not merely a question of management and technology, but rather, and perhaps in the first instance, a question of social power. The many manifestations of this power discussed in this book suggest how an enabling and empowering water politics need to address this question of power head on. In particular, those that defend the rights of the disempowered to the city’s nature have to understand the central political power relationships that structure the existing pattern.
Cultural Geography
Authors: Myers Garth A. , McGreevy Patrick
Published: November 2020

. . . We have not really prescribed limitations of inquiry, method, or thought upon our associates. From time to time there are attempts to the contrary, but we shake them off after a while and go about doing what we most want to do. . . . We thrive on cross-fertilization and diversity. Sauer (1956) You can’t go wrong when you call something cultural, for it is the one term that, without necessarily specifying anything, carries the full weight of all possible forms of specificity. Gallagher (1995: 307) . . . Both these quotations, one recent and one nearly a half-century old, point to the monumental task before us in attempting to report on the progress of cultural geography over the past dozen years. Many things get called cultural geography, for many different reasons, with varying purposes in mind. Different people who consider themselves cultural geographers often have wildly different ideas of what this label means, as well as radically different approaches to what they do. We cannot pretend to encompass the whole of this body of work, and we must admit as much at the outset. Instead, let us begin with the specialty group itself, since it provides some focus and continuity for taking stock of the subfield. The Cultural Geography Specialty Group’s membership has increased slowly but steadily since the group’s inception in the late 1980s. With 465 members, the CGSG was, as of 2000, the Association of American Geographers’ fourth-largest specialty group out of fifty-seven, behind the GIS, Urban Geography, and Remote Sensing groups. In terms of topical proficiency among AAG members, cultural geography looms even larger. Cultural geography is the third most frequently claimed area of proficiency, behind only GIS and Urban Geography, with 848 practicing professionals, or 13 per cent of the AAG membership. And, given Gallagher’s and Sauer’s points, the number of people who might be claimed by someone as cultural geographers would be much larger than this. Reflecting on these numbers, it appears that, far from being a moribund subfield dying out in the face of a technological revolution in the discipline, cultural geography, however it may be defined, is actually flourishing on the eve of a new millennium.
Geography Education
Authors: Bednarz Sarah W. , Downs Roger M.
Published: November 2020

The evolution of the profession of geography as an academic discipline has been intertwined with the teaching of geography in schools and colleges (Warntz 1964; Blouet 1981; Cormack 1997; Douglas 1998). Even today, the largest proportion of members of the Association of American Geographers (AAG) is employed in higher education and is charged with teaching high school graduates. The short-term fortunes of academic Departments of Geography are a direct function of student credit hours generated. Therefore, the long-term viability of Departments is a function of significant numbers of students being willing—or required—to take college geography courses. Motivation for optional or mandatory participation in geographic learning at all levels of instruction is a cause of and a response to society’s valuation of geographic knowledge. Over the past two decades, American society has placed an increasing value on geographic literacy, although what it means to be geographically literate remains subject to debate. In this chapter, we use the definition from the National Geography Standards (hereafter referred to as the Standards) (Geography Education Standards Project 1994: 34), “The outcome of Geography for Life is a geographically informed person (1) who sees meaning in the arrangement of things in space; (2) who see relations between people, places, and environments; (3) who uses geographic skills; and (4) who applies spatial and ecological perspectives to life situations.” The increasing valuation of geographic knowledge has been facilitated by an infrastructure ranging from the National Geographic Society’s (NGS) state alliance network to the AAG’s Commission on College Geography, publicized through activities such as the National Geographic Bee, and Environmental Science Research Institute (ESRI)’s “Geography Matters” campaign, and codified through public commitment to programs such as the Standards and the National Assessment of Educational Progress (NAEP). In light of the changing role of geography in American society, the Geography Education Specialty Group (GESG) adopted a revised mission statement in 1999. Its goal is, “To promote research on the lifelong development of knowledge about the world through geography; to develop the theory and foster the practice of teaching and learning geography in formal and informal educational contexts; and to be an advocate for geographic literacy” (AAG GESG 1999: 1).
Asian Geography
Authors: Shrestha Nanda , Lewis Martin
Published: November 2020

A massive continent, stretching from Turkey and the eastern shores of the Mediterranean and Red Seas to the Pacific, from the Indian Ocean to the vast desert of Mongolia right through the towering Himalayas and the plateau of Tibet, Asia is a colossal geographic collage. One can find in Asia virtually every form of landscape, both real and imagined, including James Hilton’s (1933) Shangri-La, planted in the imaginative geography of Western travelers and tourists (also see Bishop 1989). As the cradle of three of the world’s early civilizations, Asia is a magnificent tapestry of cultural diversity. Asia has also given birth to all the major institutional religions that are practiced today: Hinduism, Buddhism, Judaism, Christianity, Islam, and others. As such, few would deny its enormous historical significance and contributions to human progress in every respect—spiritually, materially, and intellectually. Home to some 60 per cent of the world’s population, Asia is a human mosaic that is unparalleled in history (Table 39.1). So it is hardly surprising that Asia offers endless research challenges and opportunities, in virtually every field of geographical studies. With this in mind, this chapter is divided into four major sections. First, we provide a brief journalistic survey of major regional political events across Asia. This is followed by a segment on the state of Asian geography in America in the second part. Third, we discuss some of the developments, trends, and research themes in Asian geography in America during the period 1988–2000. Finally, we conclude the chapter with some general remarks on the vexing question of what lies ahead for regional geography. We explore this question not because we foresee an imminent demise of regional geography, but because some of the remarkable developments during the 1990s have definite impacts on the way we see and do regional geography.
Computing Machinery and Intelligence (1950)
Authors: Turing Alan
Published: November 2020

Together with ‘On Computable Numbers’, ‘Computing Machinery and Intelligence’ forms Turing’s best-known work. This elegant and sometimes amusing essay was originally published in 1950 in the leading philosophy journal Mind. Turing’s friend Robin Gandy (like Turing a mathematical logician) said that ‘Computing Machinery and Intelligence’… was intended not so much as a penetrating contribution to philosophy but as propaganda. Turing thought the time had come for philosophers and mathematicians and scientists to take seriously the fact that computers were not merely calculating engines but were capable of behaviour which must be accounted as intelligent; he sought to persuade people that this was so. He wrote this paper—unlike his mathematical papers—quickly and with enjoyment. I can remember him reading aloud to me some of the passages— always with a smile, sometimes with a giggle. The quality and originality of ‘Computing Machinery and Intelligence’ have earned it a place among the classics of philosophy of mind. ‘Computing Machinery and Intelligence’ contains Turing’s principal exposition of the famous ‘imitation game’ or Turing test. The test first appeared, in a restricted form, in the closing paragraphs of ‘Intelligent Machinery’ (Chapter 10). Chapters 13 and 14, dating from 1951 and 1952 respectively, contain further discussion and amplification; unpublished until 1999, this important additional material throws new light on how the Turing test is to be understood. The imitation game involves three participants: a computer, a human interrogator, and a human ‘foil’. The interrogator attempts to determine, by asking questions of the other two participants, which of them is the computer. All communication is via keyboard and screen, or an equivalent arrangement (Turing suggested a teleprinter link). The interrogator may ask questions as penetrating and wide-ranging as he or she likes, and the computer is permitted to do everything possible to force a wrong identification. (So the computer might answer ‘No’ in response to ‘Are you a computer?’ and might follow a request to multiply one large number by another with a long pause and a plausibly incorrect answer.) The foil must help the interrogator to make a correct identification.
Introduction
Authors: Slack Paul , Ward Ryk
Published: November 2020

From the beginnings of human settlement the small marginal fringe of western Europe that eventually became the British Isles has represented a final frontier for successive waves of colonists—each bringing its own set of cultural adaptations and its own ethos into the landscape. Over time both landscape and culture have matured from raw frontier to settled centre, moulded by the advent of agriculture, towns, and industry, and by streams of migration both within Britain and from outside. The chapters in this book, together with some of the comments which followed their original delivery as lectures, trace the various phases of that process, showing how much of the story has only recently been unearthed, and how much remains to be discovered. The period surveyed is necessarily a very long one, and it is significant that successive chapters cover an increasingly narrow span of time, from the half a million years of the first chapter to the 150 of the last. That is partly a function of the historical record, which shifts from the scattered evidence of archaeology to the plentiful records of modern social surveys. But it is also a reflection of the accelerating pace of change, particularly in the past millennium, as increasing density of population, urbanization, and the manipulation of new sources of energy and wealth reshaped both culture and environment. In the process Britain shifted from being marginal, on the outer edge of human developments whose focus lay elsewhere, to being central: in the eighteenth and nineteenth centuries Britain was the originator of changes which have transformed the globe since then. That is one story, familiar enough in outline, but examined from new perspectives in the later chapters of this book. But there is also a second story, completed very much earlier, and forming the theme of the early chapters of this collection. It lies in the initial peopling of Britain by humans, and the stages by which biological evolution was replaced by cultural evolution as the main motor of change.
The Coming of Agriculture People, Landscapes, and Change c.4000 –1500 bc
Authors: Whittle Alasdair , Renfrew Colin
Published: November 2020

This chapter reviews the development of agriculture in Britain and Ireland from the Neolithic period to the middle of the Bronze Age (approximately 4000 to 1500 bc in calendar years), and the associated questions of the identity of the people involved, the density of populations, and their effect on the landscape. This brief account is set in the context of the wider development of an agricultural way of life on the adjacent continental mainland, going as far back as 6000 bc in central Europe. I hope to raise questions as much as to answer them, and to concentrate wherever possible on new evidence and approaches. I should like to frame my discussion by setting out four hypotheses: 1. Overall, change was slow, but punctuated by spurts or accelerations (notably around 5500 bc, 4000 bc, and 1500 bc), whose nature is still poorly understood. This hypothesis stands in opposition to a general tendency to envisage a steadily intensifying evolution of subsistence methods, population levels, and landscapes. 2. There was much continuity of population both in continental Europe and in Britain and Ireland, but the role of colonization still needs seriously to be considered. This hypothesis seeks to re-examine both the assumption in continental research of major colonization with the onset of the Neolithic and the recent British consensus that the beginnings of the Neolithic were essentially to do with the acculturation of an indigenous population. 3. Although some landscapes had been cleared of substantial tracts of woodland by about 2500–2000 bc, population levels in most parts of Britain and Ireland remained relatively low at least until the middle of the Bronze Age, and the lifestyle can be characterized by continuing mobility and/or short-term sedentism. This hypothesis restates recent opposition to the notion that the introduction of agriculture entailed sedentary existence, rapidly growing population, and intensifying production right from the start. The coming of agriculture in a more familiar guise, although preceded in Britain and Ireland by herding and piecemeal cultivation from about 4000 bc, was not seen till as late as about 1500 bc onwards.
The groupoid interpretation of type theory
Authors: Hofmann Martin , Streicher Thomas
Published: November 2020

Many will agree that identity sets are the most intriguing concept of intensional Martin-Löf type theory. For instance, it may appear surprising that their axiomatisation as an inductive family allows one to deduce the usual properties of equality, notably the replacement rule (Leibniz’s principle) which gives P(a′) from P(a) and a proof that a equals a′. This holds for arbitrary families of sets P, not only those corresponding to a predicate. This is not in conflict with decidability of type checking since if a equals a′ and p : P(a) then one does not in general have p : P(a′), but only subst(s, p) : P(a′) where s is the proof that a equals a′ and subst is defined from the eliminator for identity sets. It is a natural question to ask whether these translation functions subst(s, _) actually depend upon the nature of the proof s or, more generally, the question whether any two elements of an identity set are equal. We will call UIP(A) (t/niqueness of Identity Proofs) the following property. If a1, a2 are objects of type A then for any two proofs p and q of the proposition “a1 equals a2” we can prove that p and q are equal. More generally, UIP will stand for UIP(A) for all types A. Note that in traditional logical formalism a principle like UIP cannot even be expressed sensibly as proofs cannot be referred to by terms of the object language and thus are not within the scope of prepositional equality. The question of whether UIP is valid in intensional Martin-Löf type theory was open for a while, though it was commonly believed that UIP is underivable as any attempt for constructing a proof has failed (Coquand 1992; Streicher 1993; Altenkirch 1992). On the other hand, the intuition that a type is determined by its canonical objects might be seen as evidence for the validity of UIP as the identity sets have at most one canonical element corresponding to an instance of reflexivity.
Testing your metal: An exhibition of the metals which our body must have
Authors: Emsley John
Published: November 2020

Ask people which metals are essential for healthy living and I suspect most would say zinc and iron. Some might mention sodium and potassium, although sodium is often regarded as something deleterious to healthy living; and a few people will know that calcium is a metal also, and important. In fact the human body needs fourteen metal elements to function properly. But for every metal that we do need, there is another that our body contains that we could well do without. These metals serve no known purpose, but they come with the food we eat, the water we drink, and the air we breathe and our body absorbs them, mistaking them for more useful elements. As a result we find that the average adult contains measurable amounts of aluminium, barium, cadmium, caesium, lead, silver and strontium. There are also trace amounts of many others, including gold and uranium. Because strontium so closely resembles calcium we absorb a lot of this element, and the average person has about 320 mg in their body, far more than of many of the essential elements. On the other hand the weight of gold in the average person is only 7 mg, worth but a few pence, and the weight of uranium is only 0.07 mg, although turned into pure energy this could drive your car for five kilometres. Our body tends to retain these unwanted intruders either in our skeleton, as in the case of uranium which has a special propensity to bind to phosphate, or in our liver which has proteins that can trap metals like gold. The table below lists the amounts of the essential 14 metals in the average adult—someone who weighs 70 kg (155 pounds). As we would expect, calcium heads the list because, along with phosphate, it is what makes up the bones of our skeleton, which weighs 9 kg on average. Of this, i kg is calcium and 2.5 kg is phosphate. In fact 99% of the body's calcium and 85% of its phosphate is in the skeleton. Bone also contains water and the protein collagen, plus the elements sodium, potassium, iron, copper and chlorine.
The Major Transitions in Evolution
Authors: Maynard Smith John , Szathmary Eors
Published: November 2020

Over the history of life there have been several major changes in the way genetic information is organized and transmitted from one generation to the next. These transitions include the origin of life itself, the first eukaryotic cells, reproduction by sexual means, the appearance of multicellular plants and animals, the emergence of cooperation and of animal societies, and the unique language ability of humans. This ambitious book provides the first unified discussion of the full range of these transitions. The authors highlight the similarities between different transitions--between the union of replicating molecules to form chromosomes and of cells to form multicellular organisms, for example--and show how understanding one transition sheds light on others. They trace a common theme throughout the history of evolution: after a major transition some entities lose the ability to replicate independently, becoming able to reproduce only as part of a larger whole. The authors investigate this pattern and why selection between entities at a lower level does not disrupt selection at more complex levels. Their explanation encompasses a compelling theory of the evolution of cooperation at all levels of complexity. Engagingly written and filled with numerous illustrations, this book can be read with enjoyment by anyone with an undergraduate training in biology. It is ideal for advanced discussion groups on evolution and includes accessible discussions of a wide range of topics, from molecular biology and linguistics to insect societies.
What is life?
Authors: Maynard Smith John , Szathmary Eors
Published: November 2020

Imagine that, when the first spacemen step out of their craft onto the surface of one of the moons of Jupiter, they are confronted by an object the size of a horse, rolling towards them on wheels, and bearing on its back a concave disc pointing towards the Sun. They will at once conclude that the object is alive, or has been made by something alive. If all they find is a purple smear on the surface of the rocks, they will have to work harder to decide. This is the phenotypic approach to the definition of life: a thing is alive if it has parts, or ‘organs’, which perform functions. William Paley explained the machine-like nature of life by the existence of a creator: today, we would invoke natural selection. There are, however, dangers in assuming that any entity with the properties of a self-regulating machine is alive, or an artefact. In section 2.2, we tell the story of a self-regulating atomic reactor, the Oklo reactor, which is neither. This story can be taken in one of three ways. First, it shows the dangers of the phenotypic definition of life: not all complex entities are alive. Second, it illustrates how the accidents of history can give rise spontaneously to surprisingly complex machine-like entities. The relevance of this to the origin of life is obvious. In essence, the problem is the following. How could chemical and physical processes give rise, without natural selection, to entities capable of hereditary replication, which would therefore, from then on, evolve by natural selection? The Oklo reactor is an example of what can happen. Finally, section 2.2 can simply be skipped: the events were interesting, but do not resemble in detail those that led to the origin of life on Earth. There is an alternative to the phenotypic definition of life. It is to define as alive any entities that have the properties of multiplication, variation and heredity. The logic behind this definition, first proposed by Muller (1966), is that a population of entities with these properties will evolve by natural selection, and hence can be expected to acquire the complex adaptations for survival and reproduction that are characteristic of living things.
Outline of Crystallography for Biologists
Authors: Blow David
Published: November 2020

Outline of Crystallography for Biologists is intended for researchers and students in the biological sciences who require an insight into the methods of X-ray crystallography without needing to learn all the relevant theory. The main text is purely descriptive and is readable by those with minimal mathematical knowledge. Some mathematical detail is given throughout in boxes, but these can be ignored. Theory is limited to the essentials required to comprehend issues of quality. There is an extensive reference section and suggestions for further reading for those who wish to delve deeper. The first part 'Fundamentals' presents the underlying ideas which allow x-ray structure analysis to be carried out and provides an appropriate background to courses in structural determination. The second part 'Practice' gives more information about the procedures employed in the course of crystal structure determination. The emphasis is on the quality measures of X-ray diffraction analysis to give the reader a critical insight into the quality and accuracy of a structure determination and to enable the reader to appreciate which parts of a structure determination may have caused special difficulty. There is no pretence of completeness and many matters discussed in standard crystallography texts are deliberately omitted. However, issues not brought out in the standard texts are discussed, making it a useful resource for non-practising crystallographers as well.
Pyroelectricity
Authors: Newnham Robert E.
Published: November 2020

As the name implies, pyroelectricity is a first rank tensor property relating a change polarization P to a change in temperature δT. The defining relation can also be written in terms of the electric displacement D since no field is applied: . . . Pi = Di = piδT [C/m2]. . . Pyroelectricity is a first rank polar tensor because of the way it transforms. Being polar vectors, Pi and Di transform as . . . D'i = aijDj . . . whereas the temperature change transforms as a zero rank tensor, or a scalar: . . . δT' = δT. . . . Transforming the defining relation for pyroelectricity we get . . . D'i = aijDj = aijpjδT = aijpjδT' = p'iδT'. . . . Both the independent variable δT and the dependent variable Di have now been transformed to the new coordinate system. The property relating D'i to δT' is the transformed pyroelectric coefficient p'i = aijpj. Thus the pyroelectric coefficient is a polar first rank tensor property. In Sections 6.1 and 7.3 it was shown that the electrocaloric effect and the pyroelectric effect are governed by the same set of coefficients pi. The change in entropy per unit volume caused by an electric field is . . . δS = piEi [J/m3]. The pyroelectric (=electrocaloric coefficient) coefficient is usually expressed in units of μC/m2 K and can be either positive or negative in sign depending on whether the spontaneous (built-in) polarization is increasing or decreasing with temperature. Pyroelectricity disappears in all centrosymmetric materials. The proof follows. For a first rank tensor there are, in general, three nonzero coefficients p1, p2, and p3 representing the values of the pyroelectric coefficient along property axes Z1, Z2, and Z3, respectively. The principal axes are perpendicular to each other and are chosen in accordance with the IEEE convention (Section 4.3).
Thermal expansion
Authors: Newnham Robert E.
Published: November 2020

When a material is heated uniformly it undergoes a strain described by the Relationship . . . xij = αijΔT, . . . where αij are the thermal expansion coefficients and
Acoustic waves I
Authors: Newnham Robert E.
Published: November 2020

In this chapter we treat plane waves specified by a wave normal and a particle motion vector . Two types of waves, longitudinal waves and shear waves, are observed in solids. For low symmetry directions, there are generally three different waves with the same wave normal, a longitudinal wave and two shear waves. The particle motions in the three waves are perpendicular to one another. Only longitudinal waves are present in liquids because of their inability to support shear stresses. The transverse waves are strongly absorbed. Acoustic wave velocities (v) are controlled by elastic constants (c) and density (ρ). For a stiff ceramic (c ∼ 5 × 1011 N/m2) and density (ρ ∼ 5 g/cm3 = 5000 kg/m3), the wave velocity is about 104 m/s. For low frequency vibrations near 1 kHz the wavelength λ is about 10 m. The shortest wavelengths are around 1 nm and correspond to infrared vibrations of 1013 Hz. Acoustic wave velocities for polycrystalline alkali metals are plotted in Fig. 23.2. Longitudinal waves travel at about twice the speed of transverse shear waves since c11 > c44. Sound is transmitted faster in light metals like Li which have shorter, stronger bonds and lower density than heavy alkali atoms like Cs. The tensor relation between velocity and elastic constants is derived using Newton’s Laws and the differential volume element shown in Fig. 23.3(a). The volume is equal to (δZ1) (δZ2) (δZ3). Acoustic waves are characterized by regions of compression and rarefaction because of the periodic particle displacements associated with the wave. These displacements are caused by the inhomogeneous stresses emanating from the source of the sound. In tensor form the components of the stress gradient are ∂Xij/∂Zk and will include both tensile stress gradients and shear stress gradients, as pictured in Fig. 23.3(b). The force F acting on the volume element is calculated by multiplying the stress components by the area of the faces on which the force acts.
Nonlinear optics
Authors: Newnham Robert E.
Published: November 2020

In most dielectrics, the linear relation between electric polarization and applied electric field is accurately obeyed even for fairly large fields of 107 V/m. The reason is that the atomic displacements are extremely small, in the range of nuclear sizes—millions of times smaller than the size of atoms. Though nonlinear effects such as electrostriction have been known for some time, it was not until the invention of the laser that sufficiently large optical fields became available to produce sizeable nonlinear optical effects. The induced polarization P can be written as a power series in an electric field, . . . P = χE + dE2 +· · · , . . . where χ is the linear electric susceptibility, and the higher-order terms lead to nonlinear effects such as second harmonic generation. The electric field associated with the incident light is sinusoidal, E = E0 sin ωt, and when E is substituted in the expression for P, a power series in sin ωt results. The second term is dE20 sin2 ωt = 1/2dE20 (1 − cos 2ωt), which includes a component of polarization with twice the frequency of the impressed field E. This rapidly oscillating induced dipole moment is the source of second harmonic light. The intensity of the light depends on the size of d, the second order coefficient. Crystal symmetry is a major factor in the second-order effect. The one-dimensional polar chain in Fig. 29.2 illustrates the origin of the quadratic term. When the applied field is directed to the left, the ions and bonding electrons are in very close contact and the displacements will be small because of short range repulsive forces. These forces do not oppose motion in the opposite direction, so that fields directed to the right give larger motions and larger polarizations. A centric chain does not show this effect. Such a chain can give rise to odd-order terms producing saturation but not to even power terms in the P(E) relation. This means that centric crystals are useless as second harmonic generators.
In search of possible causes of mass extinctions
Authors: Hallam Tony
Published: November 2020

When the subject of extinctions in the geological past comes up, nearly everyone’s thoughts turn to dinosaurs. It may well be true that these long-extinct beasts mean more to most children than the vast majority of living creatures. One could even go so far as to paraphrase Voltaire and maintain that if dinosaurs had never existed it would have been necessary to invent them, if only as a metaphor for obsolescence. To refer to a particular machine as a dinosaur would certainly do nothing for its market value. The irony is that the metaphor is now itself obsolete. The modern scientific view of dinosaurs differs immensely from the old one of lumbering, inefficient creatures tottering to their final decline. Their success as dominant land vertebrates through 165 million years of the Earth’s history is, indeed, now mainly regarded with wonder and even admiration. If, as is generally thought, the dinosaurs were killed off by an asteroid at the end of the Cretaceous, that is something for which no organism could possibly have been prepared by normal Darwinian natural selection. The final demise of the dinosaurs would then have been the result, not of bad genes, but of bad luck, to use the laconic words of Dave Raup. In contemplating the history of the dinosaurs it is necessary to rectify one widespread misconception. Outside scientific circles the view is widely held that the dinosaurs lived for a huge slice of geological time little disturbed by their environment until the final apocalypse. This is a serious misconception. The dinosaurs suffered quite a high evolutionary turnover rate, and this implies a high rate of extinction throughout their history. Jurassic dinosaurs, dominated by giant sauropods, stegosaurs, and the top carnivore Allosaurus, are quite different from those of the Cretaceous period, which are characterized by diverse hadrosaurs, ceratopsians, and Tyrannosaurus. Michael Crichton’s science-fiction novel Jurassic Park, made famous by the Steven Spielberg movies, features dinosaurs that are mainly from the Cretaceous, probably because velociraptors and Tyrannosaurus could provide more drama.
Introduction To Crystal Dislocations
Authors: Bulatov Vasily , Cai Wei
Published: November 2020

Dislocations first appeared as an abstract mathematical concept. In the late 19th century, Italian mathematician Vito Volterra examined mathematical properties of singularities produced by cutting and shifting matter in a continuous solid body [1]. As happened to some other mathematical concepts, dislocations could have remained a curious product of mathematical imagination known only to a handful of devoted mathematicians. In 1934, however, three scientists, Taylor, Polanyi and Orowan, independently proposed that dislocations may be responsible for a crystal’s ability to deform plastically [2, 3, 4]. While successfully explaining most of the puzzling phenomenology of crystal plasticity, crystal dislocations still remained mostly a beautiful hypothesis until the late 1950s when first sightings of them were reported in transmission electron microscopy (TEM) experiments [5]. Since then, the ubiquity and importance of dislocations for crystal plasticity and numerous other aspects of material behavior have been regarded as firmly established as, say, the role of DNA in promulgating life. Dislocations define a great many properties of crystalline materials. In addition to a crystal’s ability to yield and flow under stress, dislocations also control other mechanical behaviors such as creep and fatigue, ductility and brittleness, indentation hardness and friction. Furthermore, dislocations affect how a crystal grows from solution, how a nuclear reactor wall material is damaged by radiation, and whether or not a semiconductor chip in an electronic device will function properly. It can take an entire book just to describe the various roles dislocations play in materials behavior. However, the focus of this book is on the various computational models that have been developed to study dislocations. This chapter is an introduction to the basics of dislocations, setting the stage for subsequent discussions of computational models and associated numerical issues. Like any other crystal defect, dislocations are best defined with respect to the host crystal structure. We begin our discussion by presenting in Section 1.1 the basic elements and common terminology used to describe perfect crystal structures. Section 1.2 introduces the dislocation as a defect in the crystal lattice and discusses some of its essential properties. Section 1.3 discusses forces on dislocations and atomistic mechanisms for dislocation motion.
Phase Field Method
Authors: Bulatov Vasily , Cai Wei
Published: November 2020

The phase field method (PFM) can be used as an approach to dislocation dynamics simulations alternative to the line DD method discussed in Chapter 10. The degrees of freedom in PFM are continuous smooth fields occupying the entire simulation volume, and dislocations are identified with locations where the field values change rapidly. As we will see later, as an approach to dislocation dynamics simulations PFM holds several advantages. First, it is easier to implement into a computer code than a line DD model. In particular, the complex procedures for making topological changes (Section 10.4) are no longer necessary. Second, the implementation of PFM can take advantage of well-developed and efficient numerical methods for solving partial differential equations (PDEs). Another important merit of PFM is its applicability in a wide range of seemingly different situations. For example, it is possible to simulate the interaction and co-evolution of several types of material microstructures, such as dislocations and alloying impurities, within a unified model. PFM has become popular among physicists and materials scientists over the last 20 years, but as a numerical method it is not new. After all, it is all about solving PDEs on a grid. Numerical integration of PDEs is a vast and mature area of computational mathematics. A number of efficient methods have already been developed, such as the finite difference method [121], the finite element method [122], and spectral methods [123], all of which have been used in PFM simulations. The relatively new aspects of PFM are associated with the method’s formulation and applications, which are partly driven by the growing interest in understanding material microstructures. In Section 11.1, we begin with the general aspects of PFM demonstrated by two simple applications of the method not related to dislocations. Section 11.2 describes the elements required to adapt PFM to dislocation simulations. There we will briefly venture into the field of micromechanics and consider the concept of eigenstrain. The elastic energy of an arbitrary eigenstrain field is derived in Section 11.3. Section 11.4 discusses an example in which the PFM equations for dislocations are solved using the fast Fourier transform method.
Stochastic Equations Of Motion
Authors: Nitzan Abraham
Published: November 2020

We have already observed that the full phase space description of a system of N particles (taking all 6N coordinates and velocities into account) requires the solution of the deterministic Newton (or Schrödinger) equations of motion, while the time evolution of a small subsystem is stochastic in nature. Focusing on the latter, we would like to derive or construct appropriate equations of motion that will describe this stochastic motion. This chapter discusses some methodologies used for this purpose, focusing on classical mechanics as the underlying dynamical theory. In Chapter 10 we will address similar issues in quantum mechanics. The time evolution of stochastic processes can be described in two ways: 1. Time evolution in probability space. In this approach we seek an equation (or equations) for the time evolution of relevant probability distributions. In the most general case we deal with an infinite hierarchy of functions, P(zntn; zn−1tn−1; . . . ; z1t1) as discussed in Section 7.4.1, but simpler cases exist, for example, for Markov processes the evolution of a single function, P(z, t; z0t0), fully characterizes the stochastic dynamics. Note that the stochastic variable z stands in general for all the variables that determine the state of our system. 2. Time evolution in variable space. In this approach we seek an equation of motion that describes the evolution of the stochastic variable z(t) itself (or equations of motion for several such variables). Such equations of motions will yield stochastic trajectories z(t) that are realizations of the stochastic process under study. The stochastic nature of these equations is expressed by the fact that for any initial condition z0 at t = t0 they yield infinitely many such realizations in the same way that measurements of z(t) in the laboratory will yield different such realizations. Two routes can be taken to obtain such stochastic equations of motions, of either kind: 1. Derive such equations from first principles. In this approach, we start with the deterministic equations of motion for the entire system, and derive equations of motion for the subsystem of interest. The stochastic nature of the latter stems from the fact that the state of the complementary system, “the rest of the world,” is not known precisely, and is given only in probabilistic terms.
Integral Equation Methods
Authors: Gray C. G. , Gubbins K. E.
Published: November 2020

In this chapter we describe some of the integral equation methods which have been devised for calculating the angular pair correlation function g(rω1ω2) and the site-site pair correlation function gαβ( r ) for molecular liquids. These methods are in the main natural extensions of methods devised for calculating the pair correlation function g(r) for atomic liquids. They can be derived from infinite-order perturbation theory (an example is given in § 5.4.8), whereby one partially sums the perturbation series of Chapter 4 to infinite order usually with the help of diagrams, or graphs, but alternative methods of derivation are also available, e.g. functional expansions. The original integral equation theories are in a certain sense more complete than perturbation theories, in that the full correlation function g (or gαβ) is calculated, whereas in perturbation theory one calculates the correction g — g0 to the reference fluid value g0. On the other hand the perturbation theory approximations are controlled; one can estimate the error by calculating the next term. I t is extremely difficult to estimate a priori the error in integral equation approximations, since certain terms are neglected almost ad hoc. Their validity must therefore be a posteriori, according to agreement with computer simulation results (or, less satisfactorily, with experiment). Of particular interest are theories which are a combination of perturbation theory and an integral equation, which tend to have some of the advantages of both approaches (see also §5.3.1). An example is the GMF/SSC theory of §5.4.7. The structure of the integral equation approach for calculating g(r ω1 ω2) is as follows. One starts with the Ornstein-Zernike (OZ) integral equation (3.117) between the total correlation function h = g — 1 and the direct correlation function c, which we write here schematically as . . . h = c + pch (5.1) . . . or, even more schematically, as . . . h = h[c], (OZ) (5.2) . . . where h[c] denotes a functional of c.
Human impacts on soft-sediment systems—trawling and fisheries
Authors: Gray John S. , Elliott Michael
Published: November 2020

Given the discussion above regarding natural changes in the marine benthos, we should now consider the human-mediated (anthropogenic) changes and the response of benthic systems to human impacts. From the 1960s to the 1980s the general opinion seemed to be that pollution (considered in the next chapter) was the most important marine problem, but we now realize that habitat change and habitat loss are of greater concern: see, for example, the Quality Status Report 2000 (OSPAR 2000). One of the greatest effects on the integrity of the seabed and hence its biota is now known to be caused by bed trawling. This has now generated an enormous literature, and the reader is directed to Daans and Eleftheriou (2000) and Hollingworth (2000) for more details. We can take this information and summarize the overall ecosystem effects of fisheries in detailed flow diagrams (referred to as ´horrendograms´!) to show the interlinked and complex nature of the impact—the effects trawling are included here, but see also those in McLusky and Elliott (2004) (e.g. Fig. 8.1). Historically, the effects of trawling on benthos caused concern as early as 1376 when a petition was made to the English parliament by fishermen concerned over the damage done to the seabed and fisheries by bottom trawling (De Groot 1984). This was despite the gear used by sailing vessels in those days being relatively light and towed at slow speeds and in shallow water only. When steam trawlers were developed in the early 1900s, everything changed. The weight and size of trawls increased and use of tickler chains (mounted on the bottom rope to disturb bottom-living fish upwards and into the trawl net) were of great concern, although studies done in the 1970s to allay the fears of fishermen did not find long-term effects on macrobenthos (Jones 1992). At the end of World War II the otter trawl was developed and its use became widespread. This and the beam trawl (see Fig. 8.4) were (and still are) the types of gear most widely used to fish the seabed.
Mycorrhizal fungi
Authors: Maun M. Anwar
Published: November 2020

Mycorrhizal fungi (mycobionts) form a ubiquitous mutualistic symbiotic association with the roots of higher plants (phytobionts) in coastal sand dunes worldwide. These obligate biotrophs perform vital functions in the survival, establishment and growth of plants by playing an active role in nutrient cycling. As such they serve as a crucial link between plants, fungi and soil at the soil–root interface (Rillig and Allen 1999). Mycorrhizas occur in a wide variety of habitats and ecosystems including aquatic habitats, cold or hot deserts, temperate and tropical coastal dunes, tropical rainforests, saline soils, volcanic tephra soils, prairies and coral substrates (Klironomos and Kendrick 1993). Simon et al. (1993) sequenced ribosomal DNA genes from 12 species of arbuscular mycorrhizal (AM) fungi and confirmed that mycorrhizas (fungal roots) fall into three families. He estimated that they originated about 353–462 million years ago and were instrumental in facilitating the colonization of ancient plants on land. Further evidence was provided by Remy et al. (1994) who discovered arbuscules in an early Devonian land plant, Aglaophyton major, and concluded that mycorrhizal fungi were already established on land > 400 million years ago. Thus the nutrient transfer mechanism of AM fungi was already in existence before the origin of roots. Plant roots probably evolved from rhizomes and AM fungi served as an important evolutionary step in the acquisition of water and mineral nutrients (Brundrett 2002). Over evolutionary time the divergence among these fungi has accompanied the radiation of land plants, and about 200 species of AM fungi have been recognized (Klironomos and Kendrick 1993) that exist in association with about 300 000 plant species in 90% of families (Smith and Read 1997), indicating that AM fungi are capable of colonizing many host species. Approximately 150 of the described mycorrhizal species may occur in sand dunes (Koske et al. 2004). Most host–fungus associations are beneficial to both the plant and the fungus and are thus regarded as mutualistic (++); however, the widespread use of the term mutualism (mutual benefit) for mycorrhizal interactions has been questioned because all associations are not beneficial to both the plant and fungus (Brundrett 2004).