bluuebunny/crossref_metadata_2025 huggingface dataset:
Is “Arming the Future” with Geoengineering Really the Lesser Evil?: Some Doubts about the Ethics of Intentionally Manipulating the Climate System
Authors: Gardiner Stephen M.
Published: November 2020

The term geoengineering lacks a precise definition but is widely held to imply the intentional manipulation of the environment on a global scale. For most of the last 30 years, there has been a wide consensus that such manipulation would be a bad idea. However, in August 2006, Paul Crutzen, the climate scientist and Nobel laureate, published an article that reignited debate about whether we should explore geoengineering “solutions” as a response to the escalating climate-change problem. This was soon followed by other contributions and proposals, and now interest in geoengineering has become widespread, in both academia and the world of policy. As a result, Time magazine recently listed geoengineering as one of its “Ten Ideas That Are Changing the World.” Geoengineering is a relatively new and underexplored topic. This is true both of the science and the ethics. Just as we are not close to fully understanding exactly how to geoengineer if we were to choose to do so, or what the impacts of any geoengineering scheme would be, so we are also not sure how to understand the normative dimensions of undertaking geoengineering. Indeed, at this point almost no moral and political philosophy has even been attempted. In such a setting, it is useful to get some sense of the moral terrain: of what the major issues might be, of how they might be investigated, and so of how understanding might move forward. This is the main aim of this chapter. To pursue it, I shall focus on one prominent argument for geoengineering, raising a number of serious challenges that have wider application. In my view, these challenges are sufficient to seriously threaten the argument, at least in its most prominent and limited form, and so shift the burden of proof back onto proponents of geoengineering. Still, I want to make clear from the outset that my purpose is not to determine whether the pursuit of geoengineering can, in the end, be morally justified.
Land Administration
Authors: Dale Peter , McLaughlin John
Published: November 2020

This interdisciplinary work provides a high level overview of recent advances in building formal property systems throughout the world and reviews the role of property in advancing a society's economic and social agenda. It undertakes an in-depth examination of the land administration infrastructure required to support these modern property systems, giving particular attention to survey, registration, valuation, and land use control functions.
Mountain Geography
Authors: Friend Donald A.
Published: November 2020

The raw facts alone make mountains worthy of geographic interest: mountains constitute 25 per cent of the earth’s surface; they are home to 26 per cent of the world’s populace; and generate 32 per cent of global surface run-off (Meybeck et al. 2001). More than half the global population depends directly on mountain environments for the natural resources of water, food, power, wood, and minerals; and mountains contain high biological diversity; hence they are important in crop diversity and crop stability (Ives 1992; Smethurst 2000; UNFAO 2000). Elevation, relief, and differences in aspect make mountains excellent places to study all processes, human and physical: high energy systems make mountains some of the most inhospitable of environments for people and their livelihoods, and strikingly distinct changes in environment over short distances make mountains ideally suited to the study of earth surface processes. Mountains are often political and cultural borders, or in some cases, political, cultural, and biological islands. With ever-increasing populations placing ever-increasing environmental pressure on mountains, mountain environments are heavily impacted and are therefore quickly changing. Moreover, they are more susceptible to adverse impacts than lowlands and are degrading accordingly. Whatever environmental change or damage happens to mountain peoples and environments then moves to lower elevations, thus affecting all. Three seminal texts indicate an ongoing interest in mountain geography: the oldest, Peattie (1936), is still in print; the newest, Messerli and Ives (1997) is contemporary; and Price (1981) is now being rewritten. Indeed, mountain geography as a field in its own right has led to the recent formation of the Mountain Geography Specialty Group of the Association of American Geographers (Friend 1999). With increasing importance placed on sustainability science (Kates et al. 2001), mountain geography is at the cutting edge of inter- and multidisciplinary research that serves to unify rather than further specialize scholarly geography (Friend 1999). The United Nations proclaimed 2002 the International Year of Mountains and has devoted an entire chapter (13) of its Agenda 21 from the Rio Earth Summit to mountain sustainable development (Friend 1999; Ives and Messerli 1997; Ives et al. 1997a, b; Messerli and Ives 1997; Sène and McGuire 1997; UNFAO 1999, 2000).
Socialist Geography
Authors: Salmon Scott , Herod Andrew
Published: November 2020

The production of knowledge is a political act. As such, geographical knowledge reflects and embodies the material conditions and social relations existing at the time of its production. This recognition serves as our point of intellectual engagement with Geography in America at the Dawn of the Twenty-First Century and provides the framework within which we interpret a number of changes within “socialist” geography during the 1990s. Thus, in this chapter we do not subscribe to a progressivist account of intellectual practice, one that proposes a model of social progress towards an ultimate “truth” through the teleology of reason, technology, production, and so on. Rather, our review of socialist geography in this chapter is a problematizing and contextualizing one, a treatment that seeks to remain open to both historical transformation and geographical particularity, and to the recognition that knowledge production is a discursive act that is inherently reflective of power relations. Believing that the production of knowledge and the creation of a more just society are inextricably linked processes, leftist geographers have historically sought to challenge those bodies of knowledge that maintain (implicitly or explicitly) the current economic and political structures of society that favor the haves over the have-nots, encourage environmental destruction in the pursuit of profit, foster racism and patriarchal systems of living, and generally reinforce social inequality and hinder the pursuit of social justice. Drawing precisely upon this notion that the production of knowledge is a political act, socialist geographers in the late 1960s came together to “promote critical analysis of geographic phenomena, cognizant of geographic research on the well-being of social classes; to investigate the issue of radical change toward a more collective society; and to discover the impact of economic growth upon environmental quality and upon social equity” (Socialist Geography Specialty Group 1999). Although the broad political goals of the Socialist Geography Specialty Group (SGSG) have not changed since the 1960s, the fact that the world has been transformed dramatically in the interceding years means that the focus and approaches adopted by leftist geographers within the AAG (and elsewhere) have, of necessity, evolved to meet these challenges and new realities.
Energy Geography
Authors: Solomon Barry D. , Pasqualetti Martin J.
Published: November 2020

Fossil fuels powered the Industrial Revolution and they continue to dominate our lives as we enter the twenty-first century. Yet there are clear signs that the grip they have on every sector of society must soon relax in favor of other energy sources. Such a transition will not come because we are running out of fossil fuels, but rather because the environmental and social costs of their rapid use threaten our very existence on the planet. This is an expected development. From the time when fossil fuels first enabled and magnified humans’ dominion over the earth, the costs they brought—as any good economist would argue—have been inseparable from their benefits. Although the benefits were explicit and the local costs were experienced by many, it was not until skilled writers such as Zola, Orwell, Llewellyn, and Dickens vividly portrayed them that their widespread and pernicious nature was broadcast to those outside their immediate reach. Nowadays the problems we are grappling with have spread to the global scale, including atmospheric warming, thinning ozone, and rising exposure to above-background radioactivity. Understanding earth–energy associations is a task well matched to the varied skills of geographers. The worth of such study is increasingly apparent as the world’s human population continues to rise, as fossil fuels become more difficult to wrest from the earth, and as we continue to realize that there will be no risk-free, cost-free, or impact-free rabbits coming out of the alternative energy hat. In this chapter, we review developments in energy geography in the US and Canada as posted to the literature since the first edition of Geography in America, including a sprinkling from overseas to provide context. Owing to the fundamental nature of energy, we have accordingly cast a wide net in our background research, albeit with some boundaries. For example, while we discuss several important contributions to energy research by physical and environmental geographers, we excluded consideration of such themes as energy budgets, most climate change research, and mine-land reclamation and radioactive waste transport studies by hydrologists and geomorphologists.
Geographic Information Systems
Authors: Brown Daniel G. , Elmes Gregory
Published: November 2020

The role of GIS within the discipline of geography, not to mention its role within the daily operation of a very large range of human enterprises in the developed world, has undergone major changes in the decade-plus since the first edition of Geography in America (Gaile and Willmott 1989) was published. Not the least of these major changes is an important redefinition of the acronym. In 1989, GIS meant only “geographic information systems” and referred to an immature but rapidly developing technology. Today, many geographers make an emphatic distinction between the technology (GISystems or GIS) and the science behind the technology (GIScience or GISci). This important transition from a focus on the technology to a focus on the farranging theoretical underpinnings of the technology and its use are clearly reflected in the research progress made in this field in the past decade. This chapter highlights some of the significant aspects of this diverse research and its related impacts on education and institutions. The chapter focuses on the work of North American geographers, though reference to the work of others is unavoidable. We recognize the many and increasing contributions of our colleagues in other disciplines and overseas to the development of GISci, but focus our attention to the scope defined by the present volume. The chapter closes with speculations on the future of GIS in geography in America in the coming decade. In the late 1980s, geographic information systems (GIS) were large stand-alone software and information systems being applied to a growing range of application areas. Today GIS are well integrated into the normal operations of a large range of industries as diverse as forestry, health care delivery, retail marketing, and city planning. Developments in the capabilities of and access to GIS technology during the past decade have paralleled developments in the computer industry as a whole. Similarly, academic research into the fundamental concepts and theories that underlie GIS has matured and become better connected across multiple disciplines. Drawing on fields as diverse as computer science, cognitive science, statistics, decision science, surveying, remote sensing, and social theory, “geographic information science” (Goodchild 1992b) has emerged as an important synthesizing influence during the 1990s.
American Ethnic Geography
Authors: Estaville Lawrence E. , Hardwick Susan W.
Published: November 2020

Because the American Ethnic Geography Specialty Group was established in 1992 and was, therefore, not a part of the original Geography in America anthology in 1989, we think it is beneficial to present briefly the development and context of American ethnic geography into which we can place more current work. In 2000 the American Ethnic Geography Specialty Group changed its name to the Ethnic Geography Specialty Group; but because almost the whole of this report deals with the decade of the 1990s, we use the specialty group’s original name throughout. American ethnic geography encompasses the geographic dimensions and experiences of ethnic groups in the United States and Canada. Its roots are in cultural-historical and population geography. As such, American ethnic geography reflects the epistemologies and methodologies of human geography. Like geographers in general, most American ethnic geographers are empirical and inductive in their research. Because ethnicity is a complex concept, scholars who research ethnicity have been troubled over the years by definitional conundrums. Although in his 1974 study Isajiw determined that most ethnic researchers never explicitly define the meaning of ethnicity, he examined twenty-seven characteristics of ethnicity to construct a definition of North American ethnicity as “an involuntary group of people who share the same culture or . . . descendants of such people who identify themselves and/or are identified by others as belonging to the same involuntary group” (ibid. 122). To Isajiw, then, a person is either born into an ethnic group and is therefore socialized as Anglo, Chinese, French, Polish, etc., or can decide at some point in her/his life which ethnic identity fits best, or other people can perceive a person’s ethnicity. As underscored in the Harvard Encyclopedia of American Ethnic Groups (1980), these latter internal/external modes of ethnic identification have become increasingly more significant in North America. Paradoxically, in today’s multiethnic American society, many ethnic groups are celebrating their heritages with renewed vigor, while, simultaneously, many people are less bound by past ethnic loyalties and have either used innovative terms of self-identification to describe their multiethnicity or simply refused to be categorized ethnically.
Systems of Logic Based on Ordinals (1938)
Authors: Turing Alan
Published: November 2020

On 23 September 1936 Turing left England on a vessel bound for New York. His destination was Princeton University, where the Mathematics Department and the Institute for Advanced Study combined to make Princeton a leading centre for mathematics. Turing had applied unsuccessfully for a Visiting Fellowship to Princeton in the spring of 1935. When a year later he learned of Church’s work at Princeton on the Entscheidungsproblem, which paralleled his own (see ‘Computable Numbers: A Guide’), Turing ‘decided quite definitely’ to go there. He planned to stay for a year. In mid-1937 the offer of a Visiting Fellowship for the next academic year persuaded him to prolong his visit, and he embarked on a Ph.D. thesis. Already advanced in his academic career, Turing was an unusual graduate student (in the autumn of 1937, he himself was appointed by Cambridge University to examine a Ph.D. thesis). By October 1937 Turing was looking forward to his thesis being ‘done by about Christmas’. It took just a little longer: ‘Systems of Logic Based on Ordinals’ was accepted on 7 May 1938 and the degree was awarded a few weeks later. The following year the thesis was published in the Proceedings of the London Mathematical Society. ‘Systems of Logic Based on Ordinals’ was written under Church’s supervision. His relationship to Turing—whose formalization of the concept of an effective procedure and work on the Entscheidungsproblem was ‘possibly more convincing’ than Church’s own—was hardly the usual one of doctoral supervisor to graduate student. In an interview given in 1984, Church remarked that Turing ‘had the reputation of being a loner’ and said: ‘I forgot about him when I was speaking about my own graduate students—truth is, he was not really mine.’ Nevertheless Turing and Church had ‘a lot of contact’ and Church ‘discussed his dissertation with him rather carefully’. Church’s influence was not all for the good, however. In May 1938 Turing wrote: My Ph.D. thesis has been delayed a good deal more than I had expected. Church made a number of suggestions which resulted in the thesis being expanded to an appalling length. I hope the length of it won’t make it difficult to get it published.
Memorandum to OP-20-G on Naval Enigma (c.1941)
Authors: Turing Alan
Published: November 2020

The document that forms this chapter was written by Alan Turing and sent to the US Navy codebreaking unit, OP-20-G, in Washington, DC, probably to the celebrated cryptanalyst Mrs Agnes Driscoll. It is undated, but was probably dispatched in the autumn of 1941. Turing solved the indicating system of the principal Naval Enigma cipher, Heimisch (codenamed ‘Dolphin’ by the Government Code and Cypher School (GC & CS)), at Bletchley Park by the end of 1939. Typically, he thought Dolphin ‘could be broken because it would be so interesting to break it’ (see ‘Enigma’, p. 257).Hut 8 at Bletchley Park solved some wartime Naval Enigma signals in May and June 1940. Internal evidence shows that Turing wrote his outstanding Treatise on the Enigma around autumn 1940.GC&CS read Dolphin traffic currently, using captured keys, in June and July 1941. The resulting data provided enough cribs and other information to break Dolphin signals cryptanalytically from August onwards, within 24 to 36 hours of their transmission. Mrs Driscoll was assigned to attack Naval Enigma, with two assistants, around October 1940. However, the US Navy was then intercepting only a small proportion of the Naval Enigma signals being transmitted, and was unable to make any progress against Dolphin, especially since it could not reconstruct the wiring of Enigma’s wheels. It did not even fully understand the wheels’ noncyclometric motion, which considerably complicated any solution of Naval Enigma, in particular, since each of the special Kriegsmarine wheels VI to VIII had two notches. Notching made the wheel motion irregular, especially when a doubly notched wheel was in the middle or right-hand position. Using two doubly notched wheels could reduce Enigma’s period from its normal 16,900 (26´25´26) to 4,056 (24´13´13). In February 1941, following lengthy negotiations between the US Army and Navy, a four-man team led by Abraham Sinkov visited GC & CS. (Sinkov was accompanied by Leo Rosen, also from the US Army’s Signal Intelligence Service, and Lt. Robert Weeks and Lt. Prescott Currier, both from OP-20-G.)
On universes in type theory
Authors: Palmgren Erik
Published: November 2020

The notion of a universe of types was introduced into constructive type theory by Martin-Löf (1975). According to the propositions-as-types principle inherent in type theory, the notion plays two roles. The first is as a collection of sets or types closed under certain type constructions. The second is as a set of constructively given infinitary formulas. In this paper we discuss the notion of universe in type theory and suggest and study some useful extensions. We assume familiarity with type theory as presented in, for example, Martin-Löf (1984). Universes have been effective in expanding the realm of constructivism. One example is constructive category theory where type universes take the roles of Grothendieck universes of sets, in handling large categories. A more profound example is Aczel’s (1986) type-theoretic interpretation of constructive set theory (CZF). It is done by coding ϵ-diagrams into well-order types, with branching over an arbitrary type of the universe. The latter generality is crucial for interpreting the separation axiom. The introduction of universes and well-orders (W-types) in conjunction gives a great proof-theoretic strength. This has provided constructive justification of strong subsystems of second-order arithmetic studied by proof-theorists (see Griffor and Rathjen (1994) and Setzer (1993), and for some early results, see Palmgren (1992)). At present, it appears that the most easily justifiable way to increase the proof-theoretic strength of type theory is to introduce ever more powerful universe constructions. We will give two such extensions in this paper. Besides contributing to the understanding of subsystems of second-order arithmetic and pushing the limits of inductive definability, such constructions provide intuitionistic analogues of large cardinals (Rathjen et al, in press). A third new use of universes is to facilitate the incorporation of classical reasoning into constructive type theory. We introduce a universe of classical propositions and prove a conservation result for ‘Π-formulas’. Extracting programs from classical proofs is then tractable within type theory. The next section gives an introduction to the notion of universe. The central part of the paper is section 3 where we introduce a universe forming operator and a super universe closed under this operator.
Home, sweet home: An exhibition of detergents, dangers, delights and delusions
Authors: Emsley John
Published: November 2020

Few people today lead home-centred lives, and perhaps that’s how it should be. For earlier generations the home was all important: it was a place of comfort after a hard day’s work, a place to be proud of, a place of love and security for young children—and possibly a place of drudgery, boredom, quarrels and abuse. But whatever a home was, it was a place which chemistry was to transform, so that today it is cleaner, healthier, safer to live in, and with some remarkable labour-saving gadgets and entertainment facilities. It is cleaner because of detergents, healthier because of disinfectants and safer because the chemicals we use may be protected by other chemicals, as we shall see. Throughout the 19605, 708 and 8os the use of detergents was portrayed by some as almost wanton pollution of rivers and lakes. The chemicals that lift grease and dirt from dishes, clothes and even our own bodies were accused of causing ‘eutrophication’: the imbalance in rivers, lakes or inland seas that produces an excess of slimy algae or weeds. The main culprit was said to be phosphate in detergents, but even the surfactants they relied on for their cleaning ability were under a cloud, because these were produced from oil. Such was the odium under which detergents laboured that companies strove to produce ‘green’ alternatives that were phosphate-free. Unfortunately many consumers did not like them, but their rejection in the end hardly mattered because it turned out that phosphates were not so environmentally damaging after all. Detergents are made up of many components, but two are worth a closer look: surfactants, which dissolve grease, and phosphates, which soften the water. It is not difficult to find something good to say about them both of them. During the Gulf War of 1991, millions of barrels of crude oil were deliberately released by the Iraqi invaders into the waters of the Persian Gulf. As usually happens, it was the local birds who bore the brunt of this ecological vandalism.
Diffraction by crystals
Authors: Blow David
Published: November 2020

In Chapter 4 many two-dimensional examples were shown, in which a diffraction pattern represents the Fourier transform of the scattering object. When a diffracting object is three-dimensional, a new effect arises. In diffraction by a repetitive object, rays are scattered in many directions. Each unit of the lattice scatters, but a diffracted beam arises only if the scattered rays from each unit are all in phase. Otherwise the scattering from one unit is cancelled out by another. In two dimensions, there is always a direction where the scattered rays are in phase for any order of diffraction (just as shown for a one-dimensional scatterer in Fig. 4.1). In three dimensions, it is only possible for all the points of a lattice to scatter in phase if the crystal is correctly oriented in the incident beam. The amplitudes and phases of all the scattered beams from a three-dimensional crystal still provide the Fourier transform of the three-dimensional structure. But when a crystal is at a particular angular orientation to the X-ray beam, the scattering of a monochromatic beam provides only a tiny sample of the total Fourier transform of its structure. In the next section, we are going to find what is needed to allow a diffracted beam to be generated. We shall follow a treatment invented by Lawrence Bragg in 1913. Max von Laue, who discovered X-ray diffraction in 1912, used a different scheme of analysis; and Paul Ewald introduced a new way of looking at it in 1921. These three methods are referred to as the Laue equations, Bragg’s law and the Ewald construction, and they give identical results. All three are described in many crystallographic text books. Bragg’s method is straightforward, understandable, and suffices for present needs. I had heard J.J. Thomson lecture about…X-rays as very short pulses of radiation. I worked out that such pulses…should be reflected at any angle of incidence by the sheets of atoms in the crystal as if these sheets were mirrors.…It remained to explain why certain of the atomic mirrors in the zinc blende [ZnS] crystal reflected more powerfully than others.
Molecular replacement
Authors: Blow David
Published: November 2020

The methods described in the Chapters 7 and 8 are the only ones practicable when the structure under study is completely unknown. But as soon as a few structures were known, they suggested that related problems might be tackled in a more direct way. For example, if I know the molecular structure of horse oxyhaemoglobin, surely it can help me in the study of horse deoxyhaemoglobin crystals. Also it should help me to tackle the crystal structure of human oxyhaemoglobin. And, by the way, shouldn’t the first protein crystal structure at atomic resolution, that of sperm-whale myoglobin, help me with all of these? Well-developed techniques are now available to apply these ideas. They will be presented first for the simplest case. Suppose I know accurately the structure of a protein crystal form, A, and I can use this crystal structure to define a molecule M. This requires decisions about the boundaries that identify a molecule in A. Now I have crystallized the protein in a different crystal form, X, the diffraction intensities of which I have measured. How can the crystal structure of X be determined? From what I know of protein structure, it is fair to assume that the two molecular structures are very similar. M can be used as a model for the structure which may be in X. There is a very simple case where the crystal symmetry is unchanged and the unit cells are virtually the same. Such cases may be studied by electron-density difference maps, similar to those described for the assignment of heavy atom positions in Chapter 7. This is quite common, for example, in the case of single-site amino-acid substitutions in a protein, and the difference map may show the electron-density differences at the substituted amino acid, while the absence of significant density in the rest of the map could confirm that negligible changes had occurred in the rest of the structure. In the more important case, the crystal forms A and X crystallize differently, and the space-group symmetry is probably different. It is important to begin by determining the symmetry and cell dimensions of the X crystals.
Structural refinement
Authors: Blow David
Published: November 2020

At this stage, we have derived a model from an electron-density map and have interpreted it as closely as we can in terms of molecular structure. Provided the job has been done well enough, the next task of improving that interpretation can be left to computational procedures known as structural refinement. If further uninterpreted features of the structure are revealed, it will be necessary to go back to the methods of Chapter 11 to improve the interpretation. The purpose of structural refinement is to adjust a structure to give the best possible fit to the crystallographic observations. The intensities of the Bragg reflections constitute the observations, and the various quantities that define the structure are adjusted to give the best fit. Box 12.1 gives an outline of what is meant by refinement of quantities to fit observations. In structural refinement, a measure of the discrepancies between the calculated X-ray scattering by the model structure and the observed intensities is defined: this is called the refinement parameter. The purpose of the refinement procedure is to alter the model to give the lowest possible refinement parameter. Box 12.1 uses a simple example to bring out some important general points: 1. My model will be specified by a number of variables. In a diffraction experiment, they are usually the coordinates and B factor of every atom. If the number of observed quantities is less than the number of variables, the results can have no validity. 2. If the number of observations equals the number of variables, a perfect fit can be obtained, irrespective of the accuracy of the observations or of the model. (This is true of so-called linear problems, and approximately so in non-linear cases.) 3. If the number of observations exceeds the number of variables by only a small quantity, the estimate of the reliability of the model is questionable. In practice, refinement procedures can only work when there is a sufficient number of observations which are sufficiently accurate. Also, the model must already be good enough to make the refinement procedure meaningful.
The Emperor's New Mind
Authors: Penrose Roger , Gardner Martin
Published: November 2020

For many decades, the proponents of `artificial intelligence' have maintained that computers will soon be able to do everything that a human can do. In his bestselling work of popular science, Sir Roger Penrose takes us on a fascinating tour through the basic principles of physics, cosmology, mathematics, and philosophy to show that human thinking can never be emulated by a machine. Oxford Landmark Science books are 'must-read' classics of modern science writing which have crystallized big ideas, and shaped the way we think.
Vibrational Energy Relaxation
Authors: Nitzan Abraham
Published: November 2020

An impurity molecule located as a solute in a condensed solvent, a solid matrix or a liquid, when put in an excited vibrational state will loose its excess energy due to its interaction with the surrounding solvent molecules. Vibrational energy accumulation is a precursor to all thermal chemical reactions. Its release by vibrational relaxation following a reactive barrier crossing or optically induced reaction defines the formation of a product state. The direct observation of this process by, for example, infrared emission or more often laser induced fluorescence teaches us about its characteristic timescales and their energetic (i.e. couplings and frequencies) origin. These issues are discussed in this chapter. Before turning to our main task, which is constructing and analyzing a model for vibrational relaxation in condensed phases, we make some general observations about this process. In particular we will contrast condensed phase relaxation with its gas phase counterpart and will comment on the different relaxation pathways taken by diatomic and polyatomic molecules. First, vibrational relaxation takes place also in low density gases. Collisions involving the vibrationally excited molecule may result in transfer of the excess vibrational energy to rotational and translational degrees of freedom of the overall system. Analysis based on collision theory, with the intermolecular interaction potential as input, then leads to the cross-section for inelastic collisions in which vibrational and translational/rotational energies are exchanged. If C∗ is the concentration of vibrationally excited molecules and ρ is the overall gas density, the relaxation rate coefficient kgas is defined from the bimolecular rate law When comparing this relaxation to its condensed phase counterpart one should note a technical difference between the ways relaxation rates are defined in the two phases.
Solvation Dynamics
Authors: Nitzan Abraham
Published: November 2020

Solvent dynamical effects on relaxation and reaction process were considered in Chapters 13 and 14. These effects are usually associated with small amplitude solvent motions that do not appreciably change its configuration. However, the most important solvent effect is often equilibrium in nature—modifying the free energies of the reactants, products, and transition states, thereby affecting the free energy of activation and sometime even the course of the chemical process. Solvation energies relevant to these modifications can be studied experimentally by calorimetric and spectroscopic methods, and theoretically by methods of equilibrium statistical mechanics. With advances of experimental techniques that made it possible to observe timescales down to the femtosecond regime, the dynamics of solvation itself became accessible and therefore an interesting subject of study. Moreover, we are now able to probe molecular processes that occur on the same timescale as solvation, making it necessary to address solvation as dynamic in addition to energetic phenomenon. This chapter focuses on the important and most studied subclass of these phenomena—solvation dynamics involving charged and polar solutes in dielectric environments. In addition to their intrinsic importance, these phenomena play a central role in all processes involving molecular charge rearrangement, most profoundly in electron transfer processes that are discussed in the next chapter. Consider, as a particular example, a neutral (q = 0) atomic solute embedded in a dielectric solvent, that undergoes a sudden change of its charge to q = e, where e is the magnitude of the electron charge. This can be achieved, for example, by photoionization. The dipolar solvent molecules respond to this change in the local charge distribution by rotating in order to make their negative end point, on the average, to the just formed positive ion. Thus, the solvent configuration changes in response to the sudden change in a local charge distribution. The driving force for this change is the lowering of overall free energy that accompanies the buildup of solvent polarization.
Computability and complexity
Authors: Hedman Shawn
Published: November 2020

In this chapter we study two related areas of theoretical computer science: computability theory and computational complexity. Each of these subjects take mathematical problems as objects of study. The aim is not to solve these problems, but rather to classify them by level of difficulty. Time complexity classifies a given problem according to the length of time required for a computer to solve the problem. The polynomial-time problems P and the nondeterministic polynomial-time problems NP are the two most prominent classes of time complexity. Some problems cannot be solved by the algorithmic process of a computer. We refer to problems as decidable or undecidable according to whether or not there exists an algorithm that solves the problem. Computability theory considers undecidable problems and the brink between the undecidable and the decidable. There are only countably many algorithms and uncountably many problems to solve. From this fact we deduce that most problems are not decidable. To proceed beyond this fact, we must state precisely what we mean by an “algorithm” and a “problem.” One of the aims of this chapter is to provide a formal definition for the notion of an algorithm. The types of problems we shall consider are represented by the following examples. • The even problem: Given an n ∈ ℕ, determine whether or not n is even. • The 10-clique problem: Given finite graph, determine whether or not there exists a subgraph that is isomorphic to the 10-clique. • The satisfiability problem for first-order logic: Given a sentence of first-order logic, determine whether or not it is satisfiable. The first problem is quite easy. To determine whether a given number is even, we simply check whether the last digit of the number is 0, 2, 4, 6 or 8. The second problem is harder. If the given graph is large and does contain a 10-clique as a subgraph, then we may have to check many subsets of the graph before we find it. Time complexity gives precise meaning to the ostensibly subjective idea of one problem being “harder” than another. The third problem is the most difficult of the three problems.
Negation as Failure, Completion and Stratification
Authors: Shepherdson J. C.
Published: November 2020

The usual way of introducing negation into Horn clause logic programming is by ‘negation as failure’: if A is a ground atom . . . the goal ¬A succeeds if A fails the goal ¬A fails if A succeeds. . . . This is obviously not classical negation, at least not relative to the given program P; the fact that A fails from P does not mean that you can prove ¬A from P, e.g. if P is . . . a ← ¬b . . . then ? - b fails so, using negation as failure, ? – a succeeds, but a is not a logical consequence of P. You could deal with classical negation by using a form of resolution which gave a complete proof procedure for full first order logic. To a logician this would be the natural thing to do. Two reasons are commonly given for why this is not done. The first is that it is believed by most, but not all, practitioners, that this would be infeasible because it would lead to a combinatorial explosion, whereas negation as failure does not, since it is not introducing any radically new methods of inference, just turning the old ones round. The second is that, in practical logic programming, negation as failure is often more useful than classical negation. This is the case when the program is a database, e.g. an airline timetable. You list all the flights there are. If there is no listed flight from Zurich to London at 12.31, then you conclude that there is no such flight. The implicit use of negation as failure here saves us the enormous labour of listing all the non-existent flights. This implicit usage is made precise in the closed world assumption, one of the two commonest declarative semantics given for negation as failure. This was introduced by Reiter [1978] and formalises the idea that the database contains all the positive information about objects in the domain, that any positive ground literal which is not implied by the program is assumed to be false.
After the Professions
Authors: Susskind Richard , Susskind Daniel
Published: November 2020

When we started working on this book in 2010, our principal focus was on what the future might hold for the professions. In the course of our research and writing, however, we realized that to confine our attention to our current professions would, for two related reasons, be too limiting. In the first instance, when we gave thought to why we have the professions at all, and when we explored theories of the professions in trying to make sense of the work of professionals, we unearthed a more basic and important question that had to be answered: How do we share practical expertise in society? It became clear to us that ‘through the professions’ was only one answer to this question. In a print-based industrial society the professions have emerged as the standard solution to one shortcoming of human beings, namely, that we have ‘limited understanding’. When people need help in certain kinds of situation in life, those that call for specific types of specialist knowledge, then we naturally turn to professionals. But we cannot assume that this current answer is the only or best answer for all time. We should be alive to the possibility, as we move from a print-based industrial society into a technologybased Internet society, that there are alternatives. And we should also want to investigate these. Which leads to our second reason for concluding that our current professions are too limited an object of study. When we undertook our research at the vanguard, we found that technology and the Internet are not just improving old ways of working; they are also enabling us to bring about fundamental change. They are providing new ways to make practical expertise far more widely available. And so, what is coming over the horizon are not just better ways of handling the work within the current remit of the professions, but systems that are greatly extending our capacity to sort out problems that arise from insufficient access to practical expertise. In short, therefore, we concluded in the early stages of our work that to concentrate only on the future of the professions would be to let the tail wag the dog.
Oxford Cases in Medicine and Surgery
Authors: Farne Hugo , Norris-Cervetto Edward , Warbrick-Smith James
Published: November 2020

Oxford Cases in Medicine and Surgery, second edition, teaches students a logical step-by-step diagnostic approach to common patient presentations. This approach mirrors that used by successful clinicians on the wards, challenging students with questions at each stage of a case (history-taking, examination, investigation, management). In tackling these questions, students understand how to critically analyse information and learn to integrate their existing knowledge to a real-life scenario from start to finish. Each chapter focuses on a common presenting symptom (e.g. chest pain). By starting with a symptom, mirroring real life settings, students learn to draw on their knowledge of different physiological systems - for example, cardiology, respiratory, gastroenterology - at the same time. All the major presenting symptoms in general medicine and surgery are covered, together with a broad range of pathologies. This book is an essential resource for all medicine students, and provides a modern, well-rounded introduction to life on the wards. Ideal for those starting out in clinical medicine and an ideal refresher for those revising for OSCEs and finals.
Caries control for the patients with active lesions
Authors: Kidd Edwina , Fejerskov Ole
Published: November 2020

Chapter 4 described caries control measures for everybody, a whole population approach. The emphasis was on oral hygiene, regularly disturbing the biofilm with fluoride toothpaste. The mode of action of fluoride was discussed in some detail to show that this therapeutic agent acts topically to interfere with the deand remineralizing processes and delaying lesion development. The relevance of minimizing sugar intake was discussed. The metabolism of sugar, by microorganisms in the biofilm, creates the acidic environment for demineralization. However, what more should be done for those presenting with active lesions? This chapter will consider how to find out why these patients are developing lesions. The chapter will then explore further oral hygiene measures that might be useful. It will question how fluoride might be boosted and their diet modified. Specific groups, such as babies and young children, those with erupting teeth, patients undergoing orthodontic treatment, and patients with dry mouths will be individually discussed. Finally, a section will discuss the difficulties of advising carers on helping those who can no longer care for themselves, either though illness, disability, old age, or dementia. The caries activity of any patient, child, or adult, is assessed at the first visit of the patient by noting how many lesions judged as active are present (both cavitated and non-cavitated) and where they are located (see Chapter 3). Please note, this assessment is mainly based on clinical assessment. Some companies produce a battery of chairside salivary tests, such as microbiological counts of specific microorganisms, but these are not needed. If the patient is coming for a regular check-up, a history of recent caries activity is available (number of lesions and fillings over the last 1–3 years). This information is most valuable. A yearly increment of one or more lesions detected clinically, would indicate a high rate of lesion formation and progression. Once a dentist has assessed an individual patient’s caries activity as high, an attempt should be made to identify the relevant risk factors for this patient. It is possible to interfere with and modify many of these factors, and thus arrest ongoing active lesions, or slow down the disease activity and diminish the rate of progression.
The Plateau Zone East of G St
Authors: James Simon
Published: November 2020

The N end of the city’s plateau zone E of G St, bounded by the N wadi, the river cliff, and the head of the inner wadi, comprising the remotest corner within the walls, also became part of the Roman military quarter. Here, as across the whole N part of the city, the stratigraphy is shallow, rarely deeper than a metre, with bedrock showing in places. Surface indications and magnetometry suggest that much of the region had been built up in pre-Roman times, although there may have been areas of open ground. The street grid had been substantially laid out here, especially H St which ran to the N city wall, but E of this line it seems partly to break down. In particular, in the nominal areas of projected block positions X1–X8, 10th St actually curved off-grid to the S, probably preserving the line of an early approach road to the N end of the Citadel before the stronghold was separated from the plateau by a great quarry and rebuilt. This far N region was presumably mostly residential before AD 165, except for two known sanctuaries beside H St: the so-called Dolicheneum in X7, and a temple of unknown dedication in X9. Under Roman rule it became dominated by insertion of the massive residence known as the ‘Palace of the dux ripae’, here referred to as the Roman Palace. Closures of both G and I Sts on the N side of 10th St, by the building of Roman structures across them, indicates that the zone N of this line became a military enclosure. This was accessible from the civil town only via an entrance on H St, and from the W part of the base area on the plateau, already enclosed by a boundary along the W side of G St, via a smaller entrance on the diverted line of ‘12th St’ at the N-most point of block E3. Within the re-entrant to the continuous base perimeter created by the G St and 10th St lines, more blocks appear to have been taken over by the military.
The Turing Guide
Authors: Copeland Jack , Bowen Jonathan , Sprevak Mark , Wilson Robin
Published: November 2020

Alan Turing has long proved a subject of fascination, but following the centenary of his birth in 2012, the code-breaker, computer pioneer, mathematician (and much more) has become even more celebrated with much media coverage, and several meetings, conferences and books raising public awareness of Turing's life and work. This volume will bring together contributions from some of the leading experts on Alan Turing to create a comprehensive guide to Turing that will serve as a useful resource for researchers in the area as well as the increasingly interested general reader. The book will cover aspects of Turing's life and the wide range of his intellectual activities, including mathematics, code-breaking, computer science, logic, artificial intelligence and mathematical biology, as well as his subsequent influence.