bluuebunny/crossref_metadata_2025 huggingface dataset:
Entanglement
Authors: Barnett Stephen
Published: November 2020

We have seen, in Section 2.5, how the superposition principle leads to the existence of entangled states of two or more quantum systems. Such states are characterized by the existence of correlations between the systems, the form of which cannot be satisfactorily accounted for by any classical theory. These have played a central role in the development of quantum theory since early in its development, starting with the famous paradox or dilemma of Einstein, Podolsky, and Rosen (EPR). No less disturbing than the EPR dilemma is the problem of Schrödinger’s cat, an example of the apparent absurdity of following entanglement into the macroscopic world. It was Schrödinger who gave us the name entanglement; he emphasized its fundamental significance when he wrote, ‘I would call this not one but the characteristic trait of quantum mechanics, the one that enforces the entire departure from classical thought’. The EPR dilemma represents a profound challenge to classical reasoning in that it seems to present a conflict between the ideas of the reality of physical properties and the locality imposed by the finite velocity of light. This challenge and the developments that followed have served to refine the concept of entanglement and will be described in the first section of this chapter. We start by recalling that a state of two quantum systems is entangled if its density operator cannot be written as a product of density operators for the two systems, or as a probability-weighted sum of such products. For pure states, the condition for entanglement can be stated more simply: a pure state of two quantum systems is not entangled only if the state vector can be written as a product of state vectors for the two systems. In the discipline of quantum information, entanglement is viewed as a resource to be exploited. We shall find, both here and in the subsequent chapters, that our subject owes much of its distinctive flavour to the utilization of entanglement.
Kinetics of homogeneous chemical reactions
Authors: Bokstein Boris S. , Mendelev Mikhail I. , Srolovitz David J.
Published: November 2020

Kinetics considers the rates of different processes. Chemical kinetics refers to the rates and mechanisms of chemical reactions and mass transfer (diffusion). Recall that since thermodynamic equilibrium implies that the rates of all processes are zero, time is not a thermodynamic variable. Rather, time is the new parameter introduced by the consideration of kinetic processes. The rate of a kinetic process and how it depends on time is determined, in part, by the degree of the deviation from equilibrium. If the deviation from equilibrium is small, the rate decreases (without changing sign) as the system approaches equilibrium. If the deviation from equilibrium is large, the situation is more complicated. For example, non-monotonic (including oscillatory) processes are possible. The sign of the rate can change during such processes; that is, the reaction can proceed in one direction and then the other. Additionally, if the deviation from equilibrium is large, small changes to the system can produce very large changes in the rate of the kinetic process (i.e. chaos). Non-equilibrium, yet nearly stationary states of the system can arise (i.e. states that exist for a very long time). Finally, if the deviation from equilibrium is very large, the system can explode (i.e. the process continues to accelerate with time). In this chapter, we develop a formal description of the kinetics of rather simple chemical reactions. Consecutive and parallel reactions will also be considered here. A more general approach (irreversible thermodynamics) will be considered in Chapter 9. In Chapter 10, we examine diffusive processes. Then, in Chapter 11, we consider the kinetics of heterogeneous processes. In order to start the study of chemical reaction kinetics, we must first define what we mean by the rate of reaction. Consider the following homogeneous reaction: . . . Cl2 + 2NO → 2NOCl. (8.1) . . .
Introduction to statistical thermodynamics of condensed matter
Authors: Bokstein Boris S. , Mendelev Mikhail I. , Srolovitz David J.
Published: November 2020

In this Chapter we apply statistical thermodynamics to condensed matter. We start with a description of the structure of liquids and the relation between this structure and its thermodynamic properties. Taking the low density limit, we derive a general equation of state appropriate for both liquids and gases. Next, we turn to a statistical thermodynamic description of solids. Finally, we consider the statistical theory of solutions. Recall that interactions between molecules in an ideal gas can be ignored for the purpose of determining thermodynamic properties. Therefore, we can assume that the spatial position of a molecule is independent of the positions of all of the other molecules in the gas. In real gases under high pressure and, even more so, in condensed matter, the intermolecular interactions play an important role and the positions of molecules are not independent. In other words, intermolecular interactions lead to the formation of correlations in the location of the molecules or, equivalently, to the development of structure. The energy of the system and the other thermodynamic properties depend on this structure. Therefore, we now turn to a discussion of structure. There are two distinct approaches to this problem. The first approach is designed for crystalline materials and is based upon a description of crystal symmetry. The description of this method is outside the scope of this text. The second is based upon the introduction of probability functions for atom locations and is applicable to disordered systems such as dense gases, liquids, and amorphous solids. Consider, as we are apt to do, the ideal gas. In this case, the probability of finding s molecules at points r1, r2, . . . , rs is simply In contrast with the ideal gas, the positions of molecules in high density gases or condensed matter are not independent of each other. Therefore, we write where Fs(r1, . . . , rs) is called the s-particle correlation function. Note three obvious properties of such functions. First, the system does not change when we exchange two molecules. This implies that the correlation functions should be symmetric with respect to their arguments.
A First Course in Logic
Authors: Hedman Shawn
Published: November 2020

The ability to reason and think in a logical manner forms the basis of learning for most mathematics, computer science, philosophy and logic students. Based on the author's teaching notes at the University of Maryland and aimed at a broad audience, this text covers the fundamental topics in classical logic in an extremely clear, thorough and accurate style that is accessible to all the above. Covering propositional logic, first-order logic, and second-order logic, as well as proof theory, computability theory, and model theory, the text also contains numerous carefully graded exercises and is ideal for a first or refresher course.
Finite model theory
Authors: Hedman Shawn
Published: November 2020

This final chapter unites ideas from both model theory and complexity theory. Finite model theory is the part of model theory that disregards infinite structures. Examples of finite structures naturally arise in computer science in the form of databases, models of computations, and graphs. Instead of satisfiability and validity, finite model theory considers the following finite versions of these properties. • A first-order sentence is finitely satisfiable if it has a finite model. • A first-order sentence is finitely valid if every finite structure is a model. Finite model theory developed separately from the “classical” model theory of previous chapters. Distinct methods and logics are used to analyze finite structures. In Section 10.1, we consider various finite-variable logics that serve as useful languages for finite model theory. We define variations of the pebble games introduced in Section 9.2 to analyze the expressive power of these logics. Pebble games are one of the few tools from classical model theory that is useful for investigating finite structures. In Section 10.2, it is shown that many of the theorems from Chapter 4 are no longer true when restricted to finite models. There is no analog for the Completeness and Compactness theorems in finite model theory. Moreover, we prove Trakhtenbrot’s theorem which states that the set of finitely valid first-order sentences is not recursively enumerable. Descriptive complexity is the subject of 10.3. This subject describes the complexity classes discussed in Chapter 7 in terms of the logics introduced in Chapter 9. We prove Fagin’s theorem relating the class NP to existentional second-order logic. We prove the Cook–Levin theorem as a consequence of Fagin’s Theorem. This theorem states that the Satisfiability Problem for Propositional Logic is NP-complete. We conclude this chapter (and this book) with a section describing the close connection between logic and the P = NP problem. In this section, we discuss appropriate logics for the study of finite models. First-order logic, since it describes each finite model up to isomorphism, is too strong. For this reason, we must weaken the logic. It may seem counter-intuitive that we should gain knowledge by weakening our language.
Chemistry of Non-stoichiometric Compounds
Authors: Kosuge Koji
Published: November 2020

As inorganic materials are put to more and more practical uses--mainly in electric, magnetic, and optical devices--materials scientists must have an increasingly sophisticated understanding of the chemical and physical properties of inorganic compounds. This volume--the first of its kind in twenty years--provides a unified presentation of the chemistry of non-stoichiometric compounds based on statistical thermodynamics and structural inorganic chemistry. Four modern examples of non-stoichiometric compounds--ionic conducting compounds, hydrogen absorbing alloys, magnetic materials, and electrical materials--are discussed in detail. Students and researchers in structural inorganic chemistry, crystallography, materials science, and solid state physics will find this much-needed book both practical and informative.
Basic Statistical Mechanics
Authors: Gray C. G. , Gubbins K. E.
Published: November 2020

In this chapter we introduce distribution functions for molecular momenta and positions. All equilibrium properties of the system can be calculated if both the intermolecular potential energy and the distribution functions are known. Throughout, we shall make use of the ‘rigid molecule’ and classical approximations. In the rigid molecule approximation the system intermolecular potential energy u(rNωN ) depends only on the positions of the centres of mass rN ≡ r1 . . . rN for the N molecules and on their molecular orientations ωN ≡ ω1 . . . ωN; any dependence on vibrational or internal rotational coordinates is neglected. In the classical approximation the translational and rotational motions of the molecules are assumed to be classical. These assumptions should be quite realistic for many fluids composed of simple molecules, e.g. N2 , CO, CO2 , SO2 CF4 , etc. They are discussed in detail in §§ 1.2.1 and 1.2.2; quantum corrections to the partition function are discussed in §§ 1.2.2 and 6.9, and in Appendix 3D. In considering fluids in equilibrium we can distinguish three principal cases: (a) isotropic, homogeneous fluids (e.g. liquid or compressed gas states of N2 , O2 , etc. in the absence of an external field), (b) anisotropic, homogeneous fluids (e.g. a polyatomic fluid in the presence of a uniform electric field, nematic liquid crystals), and (c) inhomogeneous fluids (e.g. the interfacial region). These fluid states have been listed in order of increasing complexity; thus, more independent variables are involved in cases (b) and (c), and consequently the evaluation of the necessary distribution functions is more difficult. For molecular fluids it is convenient to introduce several types of distribution functions, correlation functions, and related quantities: (a) The angular pair correlation function g(r1r2 ω1 ω2). This gives complete information about the pair of molecules, and arises in expressions for the equilibrium properties for a general potential.
Perturbation Theory
Authors: Gray C. G. , Gubbins K. E.
Published: November 2020

In perturbation theory one relates the properties (e.g. the distribution functions or free energy) of the real system, for which the intermolecular potential energy is u(rN ωN), to those of a reference system where the potential is u0(rNωN), usually by an expansion in powers of the perturbation potential u1 ≡ u — u0. The first-order, second-order, etc. perturbation terms then involve both u1 and the distribution functions for the reference system. In the sections that follow we first briefly discuss the historical background of perturbation theory (§ 4.1). As a simple example we then derive the u-expansion for the free energy (§ 4.2). This is followed by general expansions for the angular pair correlation function (§ 4.3) and the free energy (§ 4.4). The expansions developed in these latter sections are for an arbitrary reference system and arbitrary perturbation parameter. We next consider some particular choices of reference system and perturbation parameter. We first consider the u-expansion (§ 4.5) further, for a potential having both attractive and repulsive parts, and also the f-expansion (§ 4.6) which uses a different reference fluid. This is followed by a description of methods for expanding the system properties for an anisotropic repulsive potential about those for a hard sphere potential (§4.7), and then the expansion for a general potential (attractive and repulsive parts) about a non-spherical reference potential (§ 4.8). We also discuss two approximation methods based on perturbation theory, the effective central potential method (§ 4.9), and generalized van der Waals models (§4.11). Non-additive potential effects are discussed in §4.10. Perturbation theories have been the subject of reviews for both atomic and molecular liquids. Perturbation expansions are closely related to inverse temperature expansions, which have been a standard technique since the earliest days of statistical mechanics. As examples, we mention some early work on gases (virial coefficients, dielectric and Kerr constants), and solids (lattice phonon specific heat, polar lattice thermodynamics, electric and magnetic susceptibility properties, alloy order-disorder transitions, ferromagnetism, and diamagnetism). In considering perturbation theory for liquids it is convenient first to discuss the historical development for atomic liquids.
Computational Text Analysis
Authors: Raychaudhuri Soumya
Published: November 2020

This book brings together the two disparate worlds of computational text analysis and biology and presents some of the latest methods and applications to proteomics, sequence analysis and gene expression data. Modern genomics generates large and comprehensive data sets but their interpretation requires an understanding of a vast number of genes, their complex functions, and interactions. Keeping up with the literature on a single gene is a challenge itself-for thousands of genes it is simply impossible. Here, Soumya Raychaudhuri presents the techniques and algorithms needed to access and utilize the vast scientific text, i.e. methods that automatically "read" the literature on all the genes. Including background chapters on the necessary biology, statistics and genomics, in addition to practical examples of interpreting many different types of modern experiments, this book is ideal for students and researchers in computational biology, bioinformatics, genomics, statistics and computer science.
Algorithms With Superpolynomial Speed-Up
Authors: Kaye Phillip , Laflamme Raymond , Mosca Michele
Published: November 2020

In this chapter we examine one of two main classes of algorithms: quantum algorithms that solve problems with a complexity that is superpolynomially less than the complexity of the best-known classical algorithm for the same problem. That is, the complexity of the best-known classical algorithm cannot be bounded above by any polynomial in the complexity of the quantum algorithm. The algorithms we will detail all make use of the quantum Fourier transform (QFT). We start off the chapter by studying the problem of quantum phase estimation, which leads us naturally to the QFT. Section 7.1 also looks at using the QFT to find the period of periodic states, and introduces some elementary number theory that is needed in order to post-process the quantum algorithm. In Section 7.2, we apply phase estimation in order to estimate eigenvalues of unitary operators. Then in Section 7.3, we apply the eigenvalue estimation algorithm in order to derive the quantum factoring algorithm, and in Section 7.4 to solve the discrete logarithm problem. In Section 7.5, we introduce the hidden subgroup problem which encompasses both the order finding and discrete logarithm problem as well as many others. This chapter by no means exhaustively covers the quantum algorithms that are superpolynomially faster than any known classical algorithm, but it does cover the most well-known such algorithms. In Section 7.6, we briefly discuss other quantum algorithms that appear to provide a superpolynomial advantage. To introduce the idea of phase estimation, we begin by noting that the final Hadamard gate in the Deutsch algorithm, and the Deutsch–Jozsa algorithm, was used to get at information encoded in the relative phases of a state. The Hadamard gate is self-inverse and thus does the opposite as well, namely it can be used to encode information into the phases. To make this concrete, first consider H acting on the basis state |x⟩ (where x ∊ {0, 1}). It is easy to see that You can think about the Hadamard gate as having encoded information about the value of x into the relative phases between the basis states |0⟩ and |1⟩.
Seed banks
Authors: Maun M. Anwar
Published: November 2020

The soil seed bank refers to a reservoir of viable seeds present on the soil surface or buried in the soil. It has the potential to augment or replace adult plants. Such reservoirs have regular inputs and outputs. Outputs are losses of seeds by germination, predation or other causes, while inputs include dispersal of fresh seeds from local sources and immigration from distant sources (Harper 1977). Since sand dunes are dynamic because of erosion, re-arrangement or burial by wind and wave action, efforts to find seed banks have largely been unsuccessful. Following dispersal, seeds accumulate in depressions, in the lee of plants, on sand surfaces, on the base of lee slopes and on the driftline. These seeds are often buried by varying amounts of sand. Buried seeds may subsequently be re-exposed or possibly lost over time. However, the existence of a seed bank can not be denied. Plant species may maintain a transient or a persistent seed bank depending on the longevity of seeds. In species with transient seed banks, all seeds germinate or are lost to other agencies and none is carried over to more than one year. In contrast, in species with a persistent seed bank at least some seeds live for more than one year. The four types of seed banks described by Thompson and Grime (1979) provide useful categories for discussion of coastal seed bank dynamics of different species. Type I species possess a transient seed bank after the maturation and dispersal of their seeds in spring that remain in the seed bank during summer until they germinate in autumn. Type II species possess a transient seed bank during winter but all seeds germinate and colonize vegetation gaps in early spring. Seeds of both types are often but not always dormant and dormancy is usually broken by high temperatures in type I and low temperature in type II. Type III species are annual and perennial herbs in which a certain proportion of seeds enters the persistent seed bank each year, while the remainder germinate soon after dispersal, and Type IV species are annual and perennial herbs and shrubs in which most seeds enter the persistent seed bank and very few germinate after dispersal.
Seed germination and seedling establishment
Authors: Maun M. Anwar
Published: November 2020

For the transformation of a seed to a seedling complex physical and biochemical changes occur within a seed before germination can proceed. Germination is controlled by diverse seed dormancy mechanisms in plant species that delays germination until the conditions are most favourable for seed germination and seedling establishment (Thompson 1970). Baskin and Baskin (1998) identified four benefits for the evolution of seed dormancy in plants: (i) persistence in risky environments as seed banks, (ii) decreased intraspecific competition, (iii) improved chances of seedling establishment and (iv) increased fitness (seed production) of the individual and the species as a whole. They showed that seed dormancy may be caused by any one of physiological, morphological, physical, chemical and mechanical constraints or by a combination of more than one of these factors. For instance, seeds may possess an embryo with a physiological inhibiting mechanism, immature embryo, impermeable seed coat or may contain chemical inhibitors and hard woody fruit walls. In all of these cases seed dormancy is eventually broken by one or more of the following treatments: after ripening, heat treatment, cold temperature stratification, prolonged exposure to high temperatures, exposure to light, softening of seed coat by microbes or physical scarification, leaching of inhibiting chemicals, ageing of seeds and other subtle changes in the habitat. In temperate North America with snow cover during winter months the seeds of a large majority of sand dune species—Cakile edentula, Ammophila breviligulata, Calamovilfa longifolia, Iva imbricata, Croton punctatus, Uniola paniculata—and others require cold stratification at <4°C for 4–6 weeks to break their dormancy requirements. Seeds of some species such as A. breviligulata and U. paniculata that require cold stratification at the northern end of their range lose this requirement in the south (Seneca 1972). At southern locations exposure to high temperatures may be required to fulfil the dormancy requirements. Winter annuals, Vulpia ciliata, Cerastium atrovirens, Mibora minima and Saxifraga tridactylites, that grow and mature their seeds in early summer on sand dunes at Aberffraw, North Wales, require exposure to high soil temperatures to overcome a state of dormancy in a certain proportion of seeds at the time of dispersal (Carey and Watkinson 1993; Pemadasa and Lovell 1975).
Salt spray and soil salinity
Authors: Maun M. Anwar
Published: November 2020

Salt spray is an important abiotic stress that affects plant and other biotic communities in the vicinity of sea coasts. Salt stress refers only to excess of ions in the environment, but along sea coasts it specifically involves increased amounts of Na+ and Cl− ions. Anyone who has visited a sea coast on windy days has experienced the landward movement of salt in the form of salt spray. Salisbury (1805) reported details of a marine storm in England following gale force winds from the east for one week. He writes: ‘On the 14th of January 1803, I observed an east window of my house, which had been cleaned a few days before, covered on the outside with an apparent hoar frost.’ Chemical analysis showed that it was salt from salt spray that had been deposited on plants, buildings and other objects. In spring of that year he made two observations: (i) plant taxa showed differential tolerance to salt spray and (ii) injury was more pronounced on the windward than the leeward sides of plants. Salt spray acts as a strong environmental stress and populations of biotic organisms have evolved traits that allow them to tolerate the effects of salt. The salt crystals also act as condensation nuclei in the air and damage plants by abrasion during wind storms. However, salt spray may also be beneficial because it improves plant growth by providing some essential nutrients. Many researchers have examined the role of salt spray on survival, distribution and growth form of plant species. In this chapter the effects of salt spray and soil salinity on seed germination, seedling survival and plant growth will be examined. Symptoms of injury to plants, mechanisms of salt tolerance and comparisons between plant species native to the coastal dunes will also be discussed. Three factors—wind speed, wave amplitude and wind direction—influence the formation of salt spray. Waves of high amplitude produce four basic types of breakers: surging, collapsing, plunging and spilling. The steepest waves with high turbulence create spilling breakers with a bore accompanied by large quantities of small foam bubbles.
Plant communities
Authors: Maun M. Anwar
Published: November 2020

Plant communities of the dune complex are a result of interaction between tolerance of plant species and sandy substrate, high wind velocities, salt spray, sand accretion and environmental heterogeneity. Propagules of many plant species are dispersed by water currents and deposited on the driftline. Most of these species find ideal conditions for germination but seedling establishment, growth and reproduction is denied to all but a few species with ecological amplitude sufficient to withstand the physical stresses associated with sand accretion, erosion and sandblasting in the highly disturbed environment. The distinct differences between habitats from the water´s edge to the inland grass-forest ecotone leads eventually to the establishment of ecologically distinct communities consisting of both plants and animals. The distinction is caused by sharp differences in the physical environment that may create sharp zones with abrupt or gradual blending of the two community types. In some locations these zones are relatively stable for long periods before any visible change occurs in the community depending on the recession of the shoreline, availability of new bare areas and the advance of communities towards the sea coast. The occurrence of plant communities in zones has been documented along sea coasts worldwide. This chapter examines the plant communities of the sand dune complex along seashores of the world. The following information has been assembled from Doing (1985), Dry coastal ecosystems Vol. 2 A, B, C, edited by Eddy van der Maarel (1993), Doody (1991) and Thannheiser (1984). It presents data on plant communities and ecology of each zone from various parts of the world. The species complement in the ´foredune complex´ in tropical, temperate and other regions around the world may be different, but their response to the prevailing environmental stresses of foredunes is convergent. In different world regions the boundaries between vegetation zones of the sand dune complex may not be defined sharply because of climatic variability, geographic location, physiography of the dune system and other factors peculiar to each location. Usually three to six different plant assemblages have been identified on the dune complex along sea coasts and lakeshores. A brief description of vegetation and ecological traits of species in each zone are presented below.
Millennial tendencies in responses to apocalyptic threats
Authors: Hughes James J.
Published: November 2020

Aaron Wildavsky proposed in 1987 that cultural orientations such as egalitarianism and individualism frame public perceptions of technological risks, and since then a body of empirical research has grown to affirm the riskframing effects of personality and culture (Dake, 1991; Gastil et al., 2005; Kahan, 2008). Most of these studies, however, have focused on relatively mundane risks, such as handguns, nuclear power, genetically modified food, and cellphone radiation. In the contemplation of truly catastrophic risks – risks to the future of the species from technology or natural threats – a different and deeper set of cognitive biases come into play, the millennial, utopian, or apocalyptic psychocultural bundle, a characteristic dynamic of eschatological beliefs and behaviours. This essay is an attempt to outline the characteristic forms millennialism has taken, and how it biases assessment of catastrophic risks and the courses of action necessary to address them. Millennialism is the expectation that the world as it is will be destroyed and replaced with a perfect world, that a redeemer will come to cast down the evil and raise up the righteous (Barkun, 1974; Cohn, 1970). Millennialism is closely tied to other historical phenomena: utopianism, apocalypticism, messianism, and millenarian violence. Western historians of millenialism have focused the most attention on the emergence of Christianity out of the messianic expectations of subjugated Jewry and subsequent Christian movements based on exegesis of the Book of Revelations expecting the imminent return of Christ. But the millennial impulse is pancultural, found in many guises and with many common tropes from Europe to India to China, across the last several thousand years. When Chinese peasants followed religiopolitical revolutionaries claiming the mantle of the Coming Buddha, and when Mohammed birthed Islam preaching that the Last Judgement was imminent, they exhibited many similar features to medieval French peasants leaving their fields to follow would-be John the Baptists. Nor is the millennial impulse restricted to religious movements and beliefs in magical or supernatural agency. Revolutionary socialism and fascism embodied the same impulses and promises, although purporting to be based on science, das Volk, and the secular state instead of prophecy, the body of believers, and the Kingdom of Heaven (Rhodes, 1980; Rowley, 1983).
Catastrophe, social collapse, and human extinction
Authors: Hanson Robin
Published: November 2020

The main reason to be careful when you walk up a flight of stairs is not that you might slip and have to retrace one step, but rather that the first slip might cause a second slip, and so on until you fall dozens of steps and break your neck. Similarly, we are concerned about the sorts of catastrophes explored in this book not only because of their terrible direct effects, but also because they may induce an even more damaging collapse of our economic and social systems. In this chapter, I consider the nature of societies, the nature of social collapse, and the distribution of disasters that might induce social collapse, and possible strategies for limiting the extent and harm of such collapse. Before we can understand how societies collapse, we must first understand how societies exist and grow. Humans are far more numerous, capable, and rich than were our distant ancestors. How is this possible? One answer is that today we have more of most kinds of ‘capital’, but by itself this answer tells us little; after all, ‘capital’ is just anything that helps us to produce or achieve more. We can understand better by considering the various types of capital we have. First, we have natural capital, such as soil to farm, ores to mine, trees to cut, water to drink, animals to domesticate, and so on. Second, we have physical capital, such as cleared land to farm, irrigation ditches to move water, buildings to live in, tools to use, machines to run, and so on. Third, we have human capital, such as healthy hands to work with, skills we have honed with practice, useful techniques we have discovered, and abstract principles that help us think. Fourth, we have social capital, that is, ways in which groups of people have found to coordinate their activities. For example, households organize who does what chores, firms organize which employees do which tasks, networks of firms organize to supply inputs to each other, cities and nations organize to put different activities in different locations, culture organizes our expectations about the ways we treat each other, law organizes our coalitions to settle small disputes, and governments coordinate our largest disputes.
Catastrophic nuclear terrorism: a preventable peril
Authors: Ackerman Gary , Potter William C.
Published: November 2020

One can conceive of at least three potentially catastrophic events involving the energy of the atom: a nuclear accident in which massive quantities of radiation inadvertently are released into the environment including inadvertent nuclear missile launches; nuclear war among nation-states; and nuclear violence inflicted by non-state actors. This chapter focuses on the last of these threats – the dangers posed by nuclear terrorism, a phenomenon that lies at the nexus between what are widely considered to be two of the primary security threats of the modern era. Non-state actors have essentially four mechanisms by which they can exploit civilian and military nuclear assets intentionally to serve their terrorist1 goals: • the dispersal of radioactive material by conventional explosives or other means; • attacks against or sabotage of nuclear facilities, in particular nuclear power plants and fuel storage sites, causing the release of radioactivity; • the theft, purchase, or receipt of fissile material leading to the fabrication and detonation of a crude nuclear explosive, usually referred to as an improvised nuclear device (IND); and • the theft, purchase, or receipt and detonation of an intact nuclear weapon. All of these nuclear threats are real; all merit the attention of the international community; and all require the expenditure of significant resources to reduce their likelihood and potential impact. The threats, however, are different and vary widely in their probability of occurrence, in consequences for human and financial loss, and in the ease with which intervention might reduce destructive outcomes (for a detailed analysis, see Ferguson and Potter, 2005). Nuclear terrorism experts generally agree that the nuclear terror scenarios withthehighestconsequences–thoseinvolvingnuclearexplosives–aretheleast likely to occur because they are the most difficult to accomplish. Conversely, the scenarios with the least damaging consequences – those involving the release of radioactivity but no nuclear explosion – are the most likely to occur because they are the easiest to carry out. Constructing and detonating an IND, for example, is far more challenging than building and setting off a radiological dispersal device (RDD), because the former weapon is far more complex technologically and because the necessary materials are far more difficult to obtain.
Nanotechnology as global catastrophic risk
Authors: Phoenix Chris , Treder Mike
Published: November 2020

The word ‘nanotechnology’ covers a broad range of scientific and technical disciplines. Fortunately, it will not be necessary to consider each separately in order to discuss the global catastrophic risks of nanotechnology, because most of them, which we will refer to collectively as nanoscale technologies, do not appear to pose significant global catastrophic risks. One discipline, however, which we will refer to as molecular manufacturing, may pose several risks of global scope and high probability. The ‘nano’ in nanotechnology refers to the numeric prefix, one-billionth, as applied to length: most structures produced by nanotechnology are conveniently measured in nanometres. Because numerous research groups, corporations, and governmental initiatives have adopted the word to describe a wide range of efforts, there is no single definition; nanotechnology fits loosely between miniaturization and chemistry. In modern usage, any method of making or studying sufficiently small structures can claim, with equal justice, to be considered nanotechnology. Although nanoscale structures and nanoscale technologies have a wide variety of interesting properties, most such technologies do not pose risks of a novel class or scope. Interest in nanotechnology comes from several sources. One is that objects smaller than a few hundred nanometres cannot be seen by conventional microscopy, because the wavelength of visible light is too large. This has made such structures difficult to study until recently. Another source of interest is that sufficiently small structures frequently exhibit different properties, such as colour or chemical reactivity, than their larger counterparts. A third source of interest, and the one that motivates molecular manufacturing, is that a nanometre is only a few atoms wide: it is conceptually (and often practically) possible to specify and build nanoscale structures at the atomic level. Most nanoscale technologies involve the use of large machines to make tiny and relatively simple substances and components. These products are usually developed to be integral components of larger products. As a result, the damage that can be done by most nanoscale technologies is thus limited by the means of production and by the other more familiar technologies with which it will be integrated; most nanoscale technologies do not, in and of themselves, appear to pose catastrophic risks, though the new features and augmented power of nano-enabled products could exacerbate a variety of other risks.
Other Systems
Authors: Chemin Jean-Yves , Desjardins Benoit , Gallagher Isabelle , Grenier Emmanuel
Published: November 2020

The methods developed in this book can be applied to various physical systems. We will not detail all the possible applications and will only quote three systems arising in magnetohydrodynamics (MHD) and meteorology, namely conducting fluids in a strong external “large scale” magnetic field, a classical MHD system with high rotation, and the quasigeostrophic limit. The main theorems of this book can be extended to these situations. The theory of rotating fluids is very close to the theory of conducting fluids in a strong magnetic field. Namely the Lorenz force and the Coriolis force have almost the same form, up to Ohm’s law. The common feature is that these phenomena appear as singular perturbation skew-symmetric operators. The simplest equations in MHD are Navier–Stokes equations coupled with Ohm’s law and the Lorenz force where ∇φ is the electric field, j the current, and e the direction of the imposed magnetic field. In this case ε is called the Hartmann number. In physical situations, like the geodynamo (study of the magnetic field of the Earth), it is really small, of order 10−5–10−10, much smaller than the Rossby number. These equations are the simplest model in geomagnetism and in particular in the geodynamo. As ε→0 the flow tends to become independent of x3. This is not valid near boundaries. For horizontal boundaries, Hartmann layers play the role of Ekman layers and in the layer the velocity is given by The critical Reynolds number for linear instability is very high, of order Rec ∼ 104. The main reason is that there is no inflexion point in the boundary layer profile (10.1.2), therefore it is harder to destabilize than the Ekman layer since the Hartmann profile is linearly stable for the inviscid model associated with (10.1.1). As for Ekman layers, Hartmann layers are stable for ReRec. There is also something similar to Ekman pumping, which is responsible for friction and energy dissipation. Vertical layers are simpler than for rotating fluids since there is only one layer, of size (εν)1/4. We refer to for physical studies.
Other Layers
Authors: Chemin Jean-Yves , Desjardins Benoit , Gallagher Isabelle , Grenier Emmanuel
Published: November 2020

Note that Ω=Ω×[0, 1] is a particular case where the boundary layers are purely horizontal or purely vertical. In the general case of an open domain Ω, the boundaries have various orientations. As long as the tangential plane ∂Ω is not vertical, the boundary layers are of Ekman type, with a size of order where ν is the normal of the tangential plane. When ν.r→0, namely when the tangential plane becomes vertical, Ekman layers become larger and larger, and degenerate for ν.r=0 in another type of boundary layer, called equatorial degeneracy of the Ekman layer. We will now detail this phenomenon in the particular case of a rotating sphere. Mathematically, almost everything is widely open! Let Ω=B(0,R) be a ball. Let θ be the latitude in spherical coordinates. The equatorial degeneracy of the Ekman layer is difficult to study. We will just give the conclusions of the analytical studies of. The Ekman layer is a good approximation of the boundary layer as long as |θ|≫E1/5. For |θ|≪E1/5 the Ekman layer degenerates into a layer of size E2/5. • for |θ|≫(εν)1/5, Ekman layer of size • for |θ| of order (εν)1/5, degeneracy of the Ekman layer into a layer of size (εν)1/5 in depth and (εν)2/5 in latitude. Let us now concentrate on the motion between two concentric rotating spheres, the speed of rotation of the spheres being the same. In this case, Ω=B(0,R) − B(0, r) where 0<r<R. Keeping in mind meteorology, the interesting case arises when R − r ≪ R: the two spheres have almost equal radius. Let us study the fluid at some latitude θ. If θ ≠0, locally, the space between the two spheres can be considered as flat and treated as a domain between two nearby plates. The conclusions of the previous paragraphs can be applied. Two Ekman layers are created, one near the inner sphere and the other one near the outer sphere.
An Hypothesis
Authors: Weiner J. S. , Stringer Chris
Published: November 2020

Towards the end of July 1953 a congress of palaeontologists was held in London under the auspices of the Wenner-Gren Foundation. The problems of fossil man were the subject of its deliberations. Java man, Neanderthal man, Rhodesian man, the South African prehumans—all these were given close attention. But Piltdown man was not discussed. Not surprisingly. He had lost his place in polite society. What more could one usefully say about him? Yet, unofficially, the Dawn Man did manage an appearance. Most of those present had not seen the original fossil specimens, so on a tour of the Natural History Museum these were shown along with others housed there. The sight of the actual fragments provoked the familiar tail-chasing discussion. As always there were those who could not feel that the famous jaw really harmonized with the rest, but there were others who took the opposite view. The enigma remained. At the dinner that night Dr. Oakley remarked casually to Dr. Washburn of Chicago and myself that owing to Dawson’s early death in 1916 the Museum had no record of the exact spot where the remains of the second Piltdown had been found. They knew the place—Sheffield Park—but the actual spot or even the field had never been marked on a map. ‘The fact is’, said Oakley, ‘that all we know about site II is on a postcard sent in July 1915 by Dawson to Woodward, and an earlier letter in that year, from neither of which can one identify the position of Piltdown II.’ This was surprising. The second group of finds had done so much to convince many people that the first Piltdown man was by no means an isolated phenomenon. One had imagined that if it were ever thought worthwhile it would be possible to go and excavate the second site. Now it appeared that this had never been done because the second site could not be located, though Woodward had apparently visited it before the second find. This curious piece of information greatly puzzled me.
‘The Eye Wink’
Authors: Weiner J. S. , Stringer Chris
Published: November 2020

In 1941 Mr. F. W. Thomas, on the staff of the News Chronicle and the Star, was advised to evacuate from Seaford and went to live in Lewes where he and his wife stayed with Mr. A. P. Pollard, Assistant Surveyor of the Sussex County Council. One day as they were touring round Chailey they found themselves near the famous Piltdown site. They had some discussion of the gravels and the circumstances of the finds. When his visitor remarked on the great evolutionary importance of the Piltdown man he was extremely surprised at his guide’s reply, which was that there was really nothing in the great discovery, and that he was entirely sceptical of it all. Mr. Pollard did not add anything more at that time. From Mr. Salzman (now President of the Sussex Archaeological Society) I learnt in August 1953 that Mr. Pollard was well acquainted with the gravels and gravel workings in the Lewes region, and that he might be able to help me with my inquiries on the history of Piltdown. When I explained I was interested in the discovery, Mr. Pollard immediately asked me whether I had any reason to distrust the discovery, and on my admitting as much, he said, ‘I am not surprised. I believe it to be a fraud. At least, that is what my old friend Harry Morris used to say.’ What Mr. Pollard had to tell me he had learnt from Harry Morris, a bank clerk and keen amateur archaeologist, whose acquaintance he had first made on taking up his post at Lewes in 1928. Morris and he became close friends, and he was Morris’s executor and saw to the donations of the latter’s collection of eoliths and other flints to the two Lewes museums. Morris in 1912 or 1913, right at the beginning, had come to the conclusion that the flints at Piltdown were not genuine. When he first saw the flints, he at once rejected them because ‘Harry Morris knew every flint bed and gravel bed in the district’.
The Question of Complicity
Authors: Weiner J. S. , Stringer Chris
Published: November 2020

In 1908 (as far as we can ascertain), long before he went to see his ‘old friend’ the Keeper of Geology at South Kensington, some time before he met Teilhard de Chardin, Dawson had in his hands the first piece of the skull of Eoanthropus. This piece, we know, had been chemically treated, by iron sulphate, to produce the brown colour, and in the process the bone had undergone the change in its crystal structure revealed by the X-ray diffraction method. This piece was part of the braincase, the ‘coconut’, smashed by the labourers, according to the story the origins of which are by no means clear. Once again a question faces us which raises sharply and finally the issue of Dawson’s complicity. We might put the question as the ‘Piltdown Riddle’:—Was the pit completely barren at the birth of Piltdown Man or did he begin life there as a burial? Was the cranium genuinely in the gravel or had it been planted where the workmen found it? In the first stages of the investigation, before we fully appreciated the artificiality of the iron-staining, we were inclined to regard the skull-case in the gravel as a genuine though not very ancient fossil. The fluorine values, while not really high, taken with the reduced content of organic matter, certainly gave grounds for accepting a semi-fossilized condition in the cranium. So it was presumed at first that the hoax had been based on a genuine discovery of portions of an ancient skull in the gravel, and that the ape jaw and canine and the other animal remains and implements had been subsequently planted. As the investigations went on, stage by stage, this view became untenable. The iron-staining threw serious doubt on the skull’s derivation from the gravel; the sulphate in the bone, in the form of gypsum, is the result of artificial and deliberate chemical treatment, and gypsum does not occur in the Piltdown or Barcombe Mills gravel. The chemical conditions in the Piltdown subsoil and gravel water are not at all such that this unusual alteration in the bone could have taken place naturally in the gravel.