bluuebunny/crossref_metadata_2025 huggingface dataset:
Solid Formulation, Comparison of Two Formulations, and Concluding Remarks
Authors: Kobayashi Shiro , Oh Soo-Ik , Altan Taylan
Published: November 2020

In the previous chapters we have discussed only the applications of flow formulation to the analysis of metal-forming processes. Lately, elastic-plastic (solid) formulations have evolved to produce techniques suitable for metal-forming analysis. This evolution is the result of developments achieved in large-strain formulation, beginning from the infinitesimal approach based on the Prandtl–Reuss equation. A question always arises as to the selection of the approach—“flow” approach or “solid” approach. A significant contribution to the solution of this question was made through a project in 1978, coordinated by Kudo, in which an attempt was made to examine the comparative merits of various numerical methods. The results were compiled for upsetting of circular solid cylinders under specific conditions, and revealed the importance of certain parameters used in computation, such as mesh systems and the size of an increment in displacement. This project also showed that the solid formulation needed improvement, particularly in terms of predicting the phenomenon of folding. For elastic-plastic materials, the constitutive equations relate strain–rate to stress–rates, instead of to stresses. Consequently, it is convenient to write the field equation in the boundary-value problem for elastic-plastic materials in terms of the equilibrium of stress rates. In this chapter, the basic equations for the finite-element discretization involved in solid formulations are outlined both for the infinitesimal approach and for large-strain theory. Further, the solutions obtained by the solid formulation are compared with those obtained by the flow formulation for the problems of plate bending and ring compression. A discussion is also given concerning the selection of the approach for the analysis. In conclusion, significant recent developments in the role of the finite-element method in metal-forming technology are summarized. The field equation for the boundary-value problem associated with the deformation of elastic-plastic materials is the equilibrium equation of stress rates. As stated in Chap. 1 (Section 1.3), the internal distribution of stress, in addition to the current states of the body, is supposed to be known, and the boundary conditions are prescribed in terms of velocity and traction-rate.
Patterns of Evolution
Authors: Thomson Keith Stewart
Published: November 2020

We now need to look more closely at the evolutionary patterns that we wish to explain. Again, we can use the study of patterns to discover and define important problems to be solved. The methods available for the study of patterns depend on the focal level of the mechanism with which one is concerned. If our interest is in individual variation, naturally we need extensive sampling and laboratory experimentation, looking at individuals within populations. In order to study the biology of populations we must work at the population level, and at such phenomena as gene and character frequencies in the field and laboratory. It is at this level that workers have most readily been able to measure selection coefficients and other quantitative elements of evolutionary science. If our interest is in the processes of speciation we must look as closely as possible at examples of the process in action—at sibling species, at a whole range of hybridization patterns in the wild and laboratory, at the distribution of closely related species in space and time. (It will be noted that between population-level work and species-level work there is an unfortunate gap; one can look at prespeciation and postspeciation situations but it is rare indeed to be confident that one is looking at speciation in flagrante delicto.) We can also look beyond the species level at phenomena of species distribution within higher taxa. Here we progress to using the methods of systematic biology and comparative morphology and paleontology. Each of these different approaches gives a different view of the evolutionary process and, therefore, in terms of the questions discussed in this book, gives us a different view of the role of mechanisms acting at the developmental level within evolutionary mechanisms. Obviously the most immediate element of causality in the origin of adaptive structures resulting from developmental properties is in the matter of individual phenotypic variation, but some of the most interesting questions concern the consequences of developmental properties for higher focal levels—their upwardly causing properties. To examine these we need to look at the species level and beyond (what has often been termed croevolution).
Introduction
Authors: Goody R. M. , Yung Y. L.
Published: November 2020

Earth, like the other inner planets, receives virtually all of its energy from space in the form of solar electromagnetic radiation. Its total heat content does not vary significantly with time, indicating a close overall balance between absorbed solar radiation and the diffuse stream of low-temperature, thermal radiation emitted by the planet. The transformation of the incident solar radiation into scattered and thermal radiation, and the thermodynamic consequences for the earth’s gaseous envelope, are the subjects of this book. The scope must be narrowed, however, because in its broadest interpretation our title could include atmospheric photochemistry and many other topics usually treated in books dealing with the upper atmosphere. By restricting attention to the thermodynamic aspects, this problem of selection usually resolves itself. For example, the absorption of energy accompanying photodissociation or photoionization will be considered if the energy involved is comparable to that of other sources or sinks, but not otherwise. Similarly, the oxygen airglow has some thermodynamic consequences in the upper atmosphere, but the important topic of the airglow will be mentioned only in this limited context. The irradiance at mean solar distance—the solar constant—is slightly less than 1400 Wm-2, giving an average flux of solar energy per unit area of the earth’s surface equal to 350 W m-2 (the factor 4 is the ratio of surface area to cross section for a sphere). Of this energy, approximately 31% is scattered back into space, 43% is absorbed at the earth's surface, and 26% is absorbed by the atmosphere. The ratio of outward to inward flux of solar radiation is known as the albedo. We may speak of the albedo of the entire earth or of individual surfaces with reference either to monochromatic radiation or to a weighted average whole is about 0.31, and an average of 224 Wm-2 is available for heating, directly and indirectly, the earth and its atmosphere. The redistribution of this absorbed solar energy by dynamic and radiative processes and its ultimate return to space as low-temperature planetary or terrestrial radiation are the most important topics of this book.
Evolution of the College-centered University: Tufts and Brandeis, 1945–1970
Authors: Freeland Richard M.
Published: November 2020

Tufts College, traditionally focused on undergraduate education in the arts and sciences, responded to the opportunities of the postwar years with new emphases on research and doctoral-level programs. A new name, “Tufts University,” signified the change. The leaders of Tufts intended, however, to retain a primary emphasis on undergraduate work. During these same years, a new university, Brandeis, sponsored by a group of American Jews, joined the state’s academic community. Brandeis’s founders also conceived their institution as centrally concerned with undergraduate education, although they too intended to build a modest array of graduate programs, especially in the arts and sciences. In projecting their development during the 1950s and 1960s, Tufts and Brandeis set out to become different versions of a distinctive institutional idea: the college-centered university. By the early 1940s, President Leonard Carmichael of Tufts, like his counterparts at Harvard and M.I.T., had come to regard World War II as a time of opportunity, despite immediate, war-related problems of enrollment and finance. Carmichael’s wartime reports referred repeatedly to new possibilities arising from the military emergency. He welcomed a Navy R.O.T.C. unit to Medford as a chance for greater visibility as well as for public service. He speculated that increased awareness of international issues would benefit the Fletcher School. Most important of all, given Tufts’s history of straightened finances, was the possibility of new federal support. “It is ... not too early,” Carmichael told his trustees in the middle of the war, “for all of us to do what we can to see to it that the men who administer our postwar education [at the federal level]... have an appreciation of the importance to this nation of colleges and universities with varied objectives and varied bases of administration and support.” If federal funds were to become available, Carmichael wanted to be sure that private institutions got their share, and he assured his board that “every effort is being made to maintain our relationships with the armed services... so that Tufts’s peculiar qualities—a university-college in which teaching and research go forward together—may be maintained ...”
Oxygen Chemistry
Authors: Sawyer Donald T. , Williams R. J. P.
Published: November 2020

This book places oxygen on the center stage of chemistry in a manner that parallels the focus on carbon by 19th century chemists. One measure of the significance of oxygen chemistry is the greater diversity of oxygen-containing molecules than of carbon-containing molecules. One of the most important compounds is water, containing the properties of being a unique medium for biological chemistry and life, the source of all the dioxygen in the atmosphere, and the moderator of the earth's climate. Sawyer first introduces the biological origins of dioxygen and role of dioxygen in aerobic biology and oxidative metabolism, and in separate chapters discusses the oxidation-reduction thermodynamics of oxygen species, and the nature of the bonding for oxygen in its compounds. Additional chapters focus on the reactivities of specific oxygen compounds. The book will be of interest to chemists and biochemists, as well as graduate students, life scientists, and medical researchers.
Spelling of Phonemes: Correct Spellings, Legal Substitutions, and Illegal Substitutions
Authors: Treiman Rebecca
Published: November 2020

So far, I have examined children’s spellings at the level of whole words. The results show that children have more difficulty with some kinds of words than others. For example, children often misspell words that contain multiple-letter graphemes, words such as that and sang. Children often misspell irregular words, words such as said and come. One would guess that th is the trouble spot in that and ai is the trouble spot in said. However, because the analyses presented so far are confined to whole words, I cannot say for sure. To determine which parts of words are difficult to spell, I must move from the level of whole words to the level of individual phonemes and individual graphemes. The need to examine children’s spellings at the level of phonemes and graphemes stems from the nature of the English writing system itself. As discussed in Chapter 1, the English writing system is basically alphabetic. Although most phonemes may be spelled in more than one way, there are relations between phonemes and graphemes. For instance, /k/ may be spelled with k, as in key, c, as in care, or ck, as in back, among other possibilities. Adults cannot always choose the correct spelling from among these possibilities, but we know that /k/ could never be written with m or b. Our knowledge of phoneme-grapheme correspondences tells us that Carl or Karl are reasonable renditions of the spoken form /k’arl/ but that Marl is not. Traditionally, it was thought that children learn to spell on a visual basis, by memorizing the sequence of letters in each word. In this view, children treat printed words as wholes. They do not learn relations between the parts of printed words (graphemes) and the parts of spoken words (phonemes). The traditional view further implies that children memorize one word at a time. They do not learn relations between sounds and spellings that apply to many different words. Findings reported in Chapter 2 suggest that this traditional view of learning to spell is incorrect For example, children's difficulty on irregular words like said and come suggests that children learn about the correspondences between phonemes and graphemes.
Searching for the Environment in Environmental Cognition Research
Authors: Zimring Craig , Gross Mark
Published: November 2020

Research in environmental cognition has been fragmented into at least three related but separate areas that reflect different purposes, viewpoints, and disciplinary conventions (Evans and Gärling, this volume). One tradition has focused on predicting spatial choices such as choosing shops or modes of transportation (Timmermans, this volume). A second tradition, driven in part by the necessity to make value judgments about settings to be spared or modified in development, has focused on the assessment of environments, and particularly on the visual quality of natural settings (R. Kaplan, this volume). Finally, a third tradition, coming principally from psychology and geography, has focused on exploring the content and structure of mental representations of the environment (Golledge, this volume). In this chapter we discuss these three approaches to environmental cognition and examine how they can contribute to each other and to a more general view of action, evaluation, and cognition. We focus specifically on the linkages between the physical environment, cognitive mediators, and outcomes such as wayfinding, decision making, and other actions. We pay particular attention to how the environment and mediators are represented. This chapter is organized into several sections. After the introduction, we review the chapters in this volume by Timmermans, R. Kaplan, and Golledge. Unlike much previous work in evaluation and in spatial decision making, all three authors discuss the cognitive processes that mediate between environment and behavior. The following section considers alternative approaches to cognitive mediators such as mental models and schemas. Following this, we briefly examine how the physical setting has been represented in environmental cognition. We then turn to computational models that attempt to provide rigorous definitions of both environment and mediator. Next, we propose our own preliminary schema-based model of wayfinding. Finally, we suggest some questions for further research. In artificial intelligence research a distinction is made between two alternative approaches to theory: “scruffy” and “neat” (Luger & Stubblefield, 1989). Whereas researchers following both traditions are interested in simulating human cognitive behavior, the scruffies primarily focus on producing a computational system where the outcomes mimic human behavior.
From Environmental to Ecological Cognition
Authors: Gärling Tommy , Lindberg Erik
Published: November 2020

In this book we have discussed how two subfields of environmental psychology— environmental cognition and assessment—are linked to each other as well as to research in related fields on decision making and action in real-world environments. We hope this discussion will stimulate integration of these heretofore unrelated fields of research. By integration we mean the establishment of a framework that shows how research in the different subfields fits together into some overall view of environmental psychology. Initially a framework of this kind must be established through analyses of existing research. The chapters in this book include such analyses. However, an integrative framework should eventually develop into a theory subject to empirical tests. This final chapter analyzes what bearings the preceding chapters have on the possibility of integration across environmental cognition, assessment, and action. We will do this by discussing a number of obstacles to integration. In doing so, a tentative, integrative framework and an agenda for future research directions are proposed. The basic motivation behind this book is that integration should lead to future, more promising research directions than currently available for understanding human-environment relationships. However, there are other benefits of integration as well. One additional such benefit is its potential value for applications through policy formation, planning, and design. Because applications have been and continue to be important to environmental psychology, a final section of the present chapter comments on this issue. The preceding chapters have revealed a number of potentially significant obstacles to the integration of research on cognition, assessment, and action in real-world environments. The most critical ones are that different researchers prefer different theoretical perspectives, that they, partly as a consequence of that, emphasize different aspects of their respective problems, and that they often prefer research paradigms that may make integration more difficult. A serious obstacle to integration across the different subfields of environmental cognition, assessment, and action is created by the low level of integration even within the subfields. Particularly striking are differences in theoretical perspectives. Such differences have far-reaching consequences because they determine how problems are framed, how hypotheses are formulated, and what research methods are chosen (Gärling & Golledge, 1989; Moore, 1987; Saegert & Winkel, 1990).
Turbulent Transfer Near the Interface
Authors: Kraus Eric B. , Businger Joost A.
Published: November 2020

The atmosphere and the ocean are in intimate contact at their interface, where momentum, water substance, heat, and trace constituents are exchanged. This exchange is often modest when a light breeze strokes the surface; sometimes the processes are violent, when gale force winds sweep up ocean spray into the atmosphere and when braking waves engulf air into the ocean. It may even appear that the transition between ocean and atmosphere becomes gradual and indistinct. The transition from ocean to atmosphere is usually an abrupt transition of one fluid to another. The interface may then be considered a continuous material surface. On both sides of the interface the fluids are usually in turbulent motion and properties are transported readily, but upon approaching the interface turbulence is largely suppressed so that on both sides of the interface a very thin layer exists where the molecular diffusion coefficients play a major role in the transport. The interface is consequently a significant barrier to the transport from ocean to atmosphere and vice versa, with little or no turbulent transport of scalar quantities across it. The quantitative determination of the thickness of the molecular sublayers and the strength of the gradients and shear layers within them are discussed in Section 5.1. We also examine the transition from the molecular sublayers to the well-mixed turbulent layers that exist beyond them, and the structure of these turbulent layers on either side of the interface. In Section 5.2 we discuss the effect of stratification on the structure of these surface layers. Some of the nonstationary interactions between the wind and the sea surface are described in Section 5.3. Sections 5.4 and 5.5 deal with practical applications: a formulation of gas transfer across the interface and of the sea surface temperature. Several observational techniques are discussed in Section 5.6.
Simulating Humans
Authors: Badler Norman I. , Phillips Cary B. , Webber Bonnie Lynn
Published: November 2020

During the past decade, high-performance computer graphics have found application in an exciting and expanding range of new domains. Among the most dramatic developments has been the incorporation of real-time interactive manipulation and display for human figures. Though actively pursued by several research groups, the problem of providing a synthetic or surrogate human for engineers and designers already familiar with computer-aided design techniques was most comprehensively solved by Norman Badler's computer graphics laboratory at the University of Pennsylvania. The breadth of that effort as well as the details of its methodology and software environment are presented in this volume. The book is intended for human factors engineers interested in understanding how a computer-graphics surrogate human can augment their analyses of designed environments. It will also inform design engineers of the state of the art in human figure modeling, and hence of the human-centered design central to the emergent concept of concurrent engineering. In fulfilling these goals, the book additionally documents for the entire computer graphics community a major research effort in the interactive control of articulated human figures.
Spatial Interaction
Authors: Badler Norman I. , Phillips Cary B. , Webber Bonnie Lynn
Published: November 2020

This chapter describes the basic architecture of the Jack interactive system. The primary tools available to the Jack user involve direct manipulation of the displayed objects and figures on the screen. With articulated figures, movement of one part will naturally affect the position of other parts. Constraints are used to specify these relationships, and an inverse kinematics algorithm is used to achieve constraint satisfaction. As a consequence of user actions, certain global postural manipulations of the entire human figure are performed by the system. This chapter presents the direct spatial manipulations offered in Jack and shows how constraints are defined and maintained. One particular application of the body constraints is included: the generation of the reachable workspace of a chain of joints. 3D direct manipulation is a technique for controlling positions and orientations of geometric objects in a 3D environment in a non-numerical, visual way. It uses the visual structure as a handle on a geometric object. Direct manipulation techniques derive their input from pointing devices and provide a good correspondence between the movement of the physical device and the resulting movement of the object that the device controls. This is kinesthetic correspondence. Much research demonstrates the value of kinesthetically appropriate feedback [Bie87, BLP78, Sch83]. An example of this correspondence in a mouse-based translation operation is that if the user moves the mouse to the left, the object moves in such a way that its image on the screen moves to the left as well. The lack of kinesthetic feedback can make a manipulation system very difficult to use, akin to drawing while looking at your hand through a set of inverting mirrors. Providing this correspondence in two dimensions is fairly straightforward, but in three dimensions it is considerably more complicated. The advantage of the direct manipulation paradigm is that it is intuitive: it should always be clear to the user how to move the input device to cause the object to move in a desired direction. It focuses the user’s attention on the object, and gives the user the impression of manipulating the object itself.
Task-Level Specifications
Authors: Badler Norman I. , Phillips Cary B. , Webber Bonnie Lynn
Published: November 2020

So far we have been talking about real-time interactive display and manipulation of human figures, with the goal of enabling human factors engineers to augment their analyses of designed environments by having human figures carry out tasks intended for those environments. This chapter explores the use of task-level specifications as an alternative to direct manipulation for generating task simulations. By now, the reader should be convinced of the value of being able to simulate, observe and evaluate agents carrying out tasks. The question is what is added by being able to produce such simulations from high-level task specifications. The answer is efficient use of the designer’s expertise and time. A designer views tasks primarily in terms of what needs to be accomplished, not in terms of moving objects or the agent’s articulators in ways that will eventually produce an instance of that behavior – e.g., in terms of slowing down and making a left turn rather than in terms of attaching the agent’s right hand to the clutch, moving the clutch forward, reattaching the agent’s right hand to the steering wheel, then rotating the wheel to the left and then back an equal distance to the right. As was the case in moving programming from machinecode to high-level programming languages, it can be more efficient to leave it to some computer system to convert a designer’s high-level goal-oriented view of a task into the agent behavior needed to accomplish it. Moreover, if that same computer system is flexible enough to produce agent behavior that is appropriate to the agent’s size and strength and to the particulars of any given environment that the designer wants to test out, then the designer is freed from all other concerns than those of imagining and specifying the environments and agent characteristics that should be tested. This chapter then will describe a progression of recent collaborative efforts between the University of Pennsylvania’s Computer Graphics Research Lab and the LING Lab (Language, INformation and Computation) to move towards true high-level task specifications embodying the communicative richness and efficiency of Natural Language instructions.
Augmented-Reality Displays
Authors: Barfield Woodrow , Rosenberg Craig
Published: November 2020

Recent technological advancements in virtual environment equipment have led to the development of augmented reality displays for applications in medicine, manufacturing, and scientific visualization (Bajura et al., 1992; Janin et al., 1993; Milgram et al., 1991; Lion et al., 1993). However, even with technological advances in virtual environment equipment, the development of augmented reality displays are still in the early stages of development, primarily demonstrating the possibilities, the use, and the technical realization of the concept. The purpose of this chapter is to review the literature on the design and use of augmented reality displays, to suggest applications for this technology, and to suggest new techniques to create these displays. In addition, the chapter also discusses the technological issues associated with creating augmented realities such as image registration, update rate, and the range and sensitivity of position sensors. Furthermore, the chapter discusses humanfactors issues and visual requirements that should be considered when creating augmented-reality displays. Essentially, an augmented-reality display allows a designer to combine part or all of a real-world visual scene, with synthetic imagery. Typically, the real-world visual scene in an augmented-reality display is captured by video or directly viewed. In terms of descriptions of augmented reality found in the literature, Janin et al. (1993) used the term “augmented reality” to signify a see-through head-mounted display (HMD) which allowed the user to view his surroundings with the addition of computer graphics overlaid on the real-world scene. Similarly, Robinett (1992) suggested the term “augmented reality” for a real image that was being enhanced with synthetic parts; he called the result a “merged representation”. Finally, Fuchs and Neuman (1993) observed that an augmented-reality display combined a simulated environment with direct perception of the world with the capability to interactively manipulate the real or virtual object(s). Based on the above descriptions, most current augmented-reality displays are designed using see-through HMDs which allow the observer to view the real world directly with the naked eye. However, if video is used to capture the real world, one may use either an opaque HMD or a screen-based system to view the scene (Lion et al., 1993).
Parallelism and Fault Tolerance
Authors: Ashcroft E. A. , Faustini A. A. , Jaggannathan R. , Wadge W. W.
Published: November 2020

The intensional nature of Lucid and eduction has two important practical consequences: (i) Lucid programs possess massive amounts of implicit parallelism and (ii) their evaluation can automatically tolerate faults. This chapter is devoted to explaining these two consequences. We start with massive implicit parallelism in Lucid programs. There are three forms of parallelism that arise in problem solving [13, 6]. The simplest form of parallelism, functional parallelism, is in the simultaneous execution of independent functions (or operators). This is sometimes referred to as structural parallelism or static parallelism.
Symplectic Geometry in Optics
Authors: Beris Antony N. , Edwards Brian J.
Published: November 2020

The scope of this book is to address the fundamental problem of modeling transport processes within complex systems, i.e., systems with internal microstructure. The classical engineering approach involves the modeling of the systems as structured continua and the subsequent use of the models in order to derive (if possible) analytical results, exact or approximate. The advent of powerful computers and the promise through parallel processing of even more substantial computational gains in the near future have introduced yet another paragon to the established engineering practice: that of the numerical simulation. Numerical simulation has emerged as a viable alternative to experiments (contrast Computational Fluid Dynamics (CFD) simulations versus wind tunnel experiments); however, the key limitation to a wider application of numerical simulations in engineering practice lies in the reliability of the models (as well as in their simplicity). CFD applications are successful since the Navier/Stokes equations which they employ are quite capable of describing accurately enough the hydrodynamics of air and water. However, as we move our emphasis to materials of such internal complexity as polymer melts, liquid crystals, suspensions, etc., the development of reliable continuum models becomes an increasingly arduous task. The main objective of this treatise is to investigate a more systematic approach through which continuum models may be developed and analyzed. The key issue that the modeler has to cope with is how to construct models which describe more of the underlying physics without, at the same time, becoming excessively complex so that they either require a prohibitively large, experimentally determined number of adjustable parameters (such as current phenomenological theories) or a prohibitively large computational time (such as required for a detailed “brute force” description of the molecular dynamics). It is the thesis of the present work that a lot of effort can be saved if the appropriate formulation is used in deriving model equations, a formulation which is capable of exploiting to a maximum degree the inherent symmetry and consistency of the collective phenomena exhibited by a large number of internal degrees of freedom.
Non-Conventional Transport Phenomena
Authors: Beris Antony N. , Edwards Brian J.
Published: November 2020

In this chapter, we wish to exploit the availability of the bracket formalism in the description of complex, non-conventional transport phenomena. In the first section, §10.1, we analyze relaxational phenomena in heat and mass transfer. The next section, §10.2, includes the description of phase transitions in inhomogeneous media. The last section, §10.3, contains a first effort to describe inertial effects in viscoelasticity. These problems have rarely been considered in the past, and when they have it has always been from a phenomenological perspective. We explore the availability of the bracket formalism here to provide a more systematic basis for these systems than has heretofore been available, and hence we characterize the models in this chapter as semi-phenomenological. The basic approach that we use is to first establish an appropriate internal variable for the system in consideration, and then to divine an appropriate Hamil-tonian which does, in some limits, produce available phenomenological models. (The latter step indicates why we characterize the models deve-loped in this chapter as “semi-phenomenological.”) As we shall see, describing the models on this more fundamental basis clears up a number of inconsistencies, as well as extending their range of validity without unduly sacrificing their simplicity. In most engineering applications of heat and mass transfer, the simple linear constitutive relations of (6.4-12) are adequate in order to describe the respective transport processes. A couple of very simple examples are the heat flux, when the affinity is the temperature gradient (giving Fourier's law of heat conduction), and the mass diffusion flux, when the affinity is the chemical potential (giving Pick's law of mass diffusion). The importance of such relationships in engineering practice cannot be overestimated. The validity of the linearized equations is generally established by steady-state experiments, so the question that naturally arises is whether or not the same constitutive relationship will hold for transient phenomena. This question cannot be answered as long as only steady-state experiments are performed. From physical considerations alone, it is obvious that the linearized constitutive relationships cannot be complete, in and of themselves.
Nuclear Power: A Nonsolution
Authors: Hardin Garrett
Published: November 2020

Constrained, structured thinking has been the predominant habit of successful operators in both business and science for at least two millennia—at least since Epicurus of Samos. Only occasionally have surprising discoveries upset the equilibria of scientists, and then only for a little while. Surprises are soon reconciled with old pictures of reality: structure and constraint reign once more. But in the disequilibrium of the interim, believers in a free lunch have a field day. By the latter half of the nineteenth century the laws of conservation of matter and energy seemed to have tied everything up into one neat package. Then in 1896 Becquerel discovered radioactivity and the old constrained view of energy was in trouble. During a decade of intense experimentation the properties and significance of radioactivity and radioactive decay were investigated, culminating in 1905 in the publication of Einstein's celebrated equation, E = me2. Conservation was redefined in terms of a new synthetic entity, mass-energy. Constraint ruled once more. Despite Einstein's rescue of conservation, there was still some turmoil because, from a practical point of view, the fact that a tiny mass could be converted into a great quantity of energy made the conservation of mass-energy seem rather academic. In 1916 the English physicist Ernest Rutherford pointed out that the energy resident in a single pound of radioactive material was equivalent to that obtainable from the combustion of 100 million pounds of coal. Since his country was then at war, it is not surprising that the physicist should have expressed a hope that radioactive energy would not be available to human beings until they had learned to live in peace with one another. Scientists of considerable stature sometimes denied the possibility of an atomic bomb. In 1930 Robert A. Millikan, a Nobel laureate in 1923 and at the time president of the California Institute of Technology, called the prospect of an atomic bomb a hobgoblin and a myth. "It is highly improbable that there is any appreciable amount of available energy for man to tap." That the grounds for Millikan's conclusion were not wholly scientific was apparent when he confessed his faith that humanity can "sleep in peace with the consciousness that the Creator has put some foolproof elements into His handiwork, and that man is powerless to do any titanic physical damage."
Choline-Containing Phospholipids: Diacyl-, Alkylacyl-, and Alkenylacylcholine Phosphoglycerides and Sphingomyelin
Authors: Hanahan Donald J.
Published: November 2020

In choosing the order for discussion of phospholipids, it is not the intention to single out one particular group as the most important; rather, an initial premise would be that all phospholipids are critical to a cell’s structure and metabolism. Certainly, as has been emphasized before, phospholipids have been shown to have key roles in the process of cellular signal transduction, and it is debatable which of several types of phospholipids is the most important. There is no doubt that the mechanism of involvement of membrane phospholipids in these complex reactions has presented a major experimental challenge, and as such this has titillated the acute scientific senses of many researchers. It is equally true also that an important field of study is emerging in cell signaling, in which unusual cellular disorders have been noted. Certainly the latter will implicate alterations or aberrations in membrane phospholipid chemistry and metabolism in one way or another. This digression was made to show quite simply that it behooves one to understand the chemical/ biochemical characteristics of the phospholipids in order to best meet the challenges of this field (and, of course, other related ones as well). On the basis of undoubted faulty logic on the choice of the order of topics, one simply can retreat to the argument of personal preference. Thus, the first group of compounds will be the choline-containing phospholipids—that is, the choline phosphoglycerides and the choline sphingolipids. As it so happens, these are among the most ubiquitous phospholipids in nature and, at least in the early “chemical” years of investigations on the phospholipids, the best-studied group. It is assumed at this junction that a highly purified phospholipid has been obtained, usually through the use of chromatographic procedures. A frequently asked question is, How do I tell whether the sample is pure? It is a logical question, especially with compounds isolated from naturally occurring sources. In actual fact, there is no simple answer.
Prologue to the Future
Authors: Iachello F. , Levine R. D.
Published: November 2020

At this point, we hope to have demonstrated that the algebraic approach provides a viable method for the quantitative description of molecular vibrotational spectra. Chapters 4 (triatomic molecules, both linear and bent) and 5 (linear tetratomic molecules) and Appendix C provide extensive documentation for the quantitative applications, while Chapter 6 shows that larger molecules can also be treated. Throughout, but most particularly in Chapter 7, we have sought to forge a link with the more familiar geometrical approach. It is precisely our requirement that even in zeroth order the Hamiltonian with which we start describes an anharmonic motion, which makes this link not trivial. The advantage of our approach in providing, even in zeroth order, high overtone spectra that are typically more accurate than 10 cm−1, should not be overlooked. Yet much remains to be done. In this chapter we look to the future: Where and why do we think that the algebraic approach will prove particularly advantageous? Of course, what we really hope for is to be surprised by unexpected new developments and applications. Here, however, is where we are certain that some of the future progress will be made, with special reference to the spectroscopy of higher-energy states of molecules. One area of spectroscopy where the Hamiltonian in matrix form is the route of choice is that of large polyatomics, particularly so when in an electronically excited state (see Note 3 of the Introduction). Such states are isoenergetic with very high vibrational overtones of the ground electronic states so that a fully geometrical approach is impractical. Even at lower energies, the exceedingly high density of vibrational states strongly favors an alternative approach, and the use of model Hamiltonian matrices is not uncommon. Such model matrices are introduced in order to account for the regularities that often survive in the observed spectrum. One such striking feature is often referred to as a “clump” (Hamilton, Kinsey, and Field, 1986). Consider a pure vibrational progression of states, as can be observed in stimulated emission spectroscopy.
Geographic Variation in Sexual Behavior: Sex, Signals, and Speciation
Authors: Verrell Paul A.
Published: November 2020

The chapters in this volume share the theme that our understanding of pattern, process, and consequence in the study of behavioral evolution can be advanced by examining differences among conspecific populations. Traditionally, biologists have sought such understanding by comparing different species. Although differences among species are usually greater than differences among conspecific populations, so many factors can vary interspecifically that determining selection pressures driving behavioral divergence may be difficult. As Arnold (1992) has argued, confounding variables often are less prevalent in intraspecific studies; in addition, relatively small evolutionary changes may be perceptible. From a historical perspective, there appear to be good reasons for believing that sexual behavior should show little variation among conspecific populations. First, early species concepts largely were typological, and accorded intraspecific variation with no reality, let alone importance (Mayr 1976). Partially due to such thinking, early ethologists argued that certain behavior patterns should be largely invariant. For Lorenz (1970), courtship behavior was a prime example of such a “fixed action pattern” (or FAP), a predictable and stereotyped sequence of actions that was elicited by a specific releasing stimulus. Later work revealed that such sequences are more variable than once thought, leading to the suggestion that the FAP be replaced by the MAP, or “modal action pattern.” This stresses the average or modal nature of much behavior (Barlow 1977). The second reason for expecting little intraspecific variation in sexual behavior derives in part from the modern synthesis. The “founding fathers” of modern evolutionary biology placed great emphasis on the role of species differences in preventing interspecific mating and wastage of reproductive effort in the production of unfit hybrid offspring (e.g., Dobzhansky 1937). Indeed, Tinbergen (1953) stated that one of the functions of mating behavior is to ensure such reproductive isolation among species. Presumably, selection would strongly favor the production of unambiguous signals, leading to invariance. The earliest evidence demonstrating the existence of intraspecific variation in sexual behavior patterns came from studies that were firmly rooted in concepts that characterized the early stages of the modern synthesis.
Controlled Drug Delivery Systems
Authors: Saltzman W. Mark
Published: November 2020

In most forms of drug delivery, spatial localization and duration of drug concentration are constrained by organ physiology and metabolism. For example, drugs administered orally will distribute to tissues based on the principles of diffusion, permeation, and flow presented in Part II of this book. If the duration of therapy provided by a single administration is insufficient, the drug must be readministered. Localization of drug can be controlled by injection, but only within limited spatial constraints, and effectiveness after an injection is usually short-lived. Controlled-delivery systems offer an alternative approach to regulating both the duration and spatial localization of therapeutic agents. In controlled delivery, the active agent is combined with other (usually synthetic) components to produce a delivery system. Unlike drug modification, which results in new agents that are single molecules, or assemblies of a limited number of molecules, drug delivery systems are usually macroscopic. Like drug modification, controlled-delivery systems frequently involve combinations of active agents with inert polymeric materials. In this text, controlled-delivery systems are distinguished from “sustained-release” drug formulations. Sustained release is often achieved by mixing an active agent with excipients or binders that alter the agent’s rate of dissolution in the intestinal tract or adsorption from a local injection site. The distinction between sustained release (often achieved by drug formulation) and controlled delivery or controlled release is somewhat arbitrary. In our definition, controlled delivery systems must (1) include a component that can be engineered to regulate an essential characteristic (e.g., duration of release, rate of release, or targeting) and (2) have a duration of action longer than a day. Many polymeric materials are available for the development of drug delivery systems (see Appendix A). Non-degradable, hydrophobic polymers have been used the most extensively. Reservoir drug delivery devices, in which a liquid reservoir of drug is enclosed in a silicone elastomer tube, were first demonstrated to provide controlled release of small molecules several decades ago [1]. This discovery eventually led to clinically useful devices, including the Norplant® (Wyeth-Ayerst Laboratories) contraceptive delivery system, which provides reliable delivery of levonorgestrel for 5 years following subcutaneous implantation.
R.G.V. Eigen: Legendary Father Of Mathematical Geology
Authors: Doveton J.H. , Davis J.C.
Published: November 2020

The original 1968 constitution of the International Association for Mathematical Geology provided that a newsletter be distributed to members. Initially the newsletter drew limited attention and consisted of little more than membership lists and postings of proposed revisions to the by-laws. As time went on, the content expanded to news of conferences and topics of interest to the geoscience community. Then a newsletter event sparked extraordinarily wide interest among the membership: the appearance in 1975 of a series on the life and contributions of R.G.V. Eigen. The idea was born during a luncheon hosted by John Harbaugh at the Eldridge Hotel in Lawrence, Kansas. Because Manfred Eigen was a guest, the conversation naturally turned to the sad neglect of the memory of his illustrious namesake. It was also observed that geomathematiciaiis owed a special debt to R.G.V. Eigen as the earliest author of a mathematical geology paper. Clearly, the IAMG News Letter would be an ideal forum to recall the achievements of this great pioneer, as an inspiration to the society members and as a simple matter of justice. The publication of the series resulted in a number of letters to the News Letter editor, John Davis. Most of the correspondents threw light on previously unknown incidents in Eigen's life as well as contributing items on Eigen's colleagues and rivals. Other, more cynical readers claimed to find an uncanny resemblance between pictures of Eigen and D.F. Merriam. However, the voices of these skeptics were stilled as anecdotal evidence of Eigen's career poured in from around the world. To ensure that the legacy of this legendary Father of Mathematical Geology will be preserved for future generations of mathematical geologists, much of the currently known Eigen material from the News Letter series and ensuing correspondence is summarized here, as well as a previously unpublished account of Eigen's meeting with Lewis Carroll. Rudolf Gottlieb Viktor Eigen (1833-1876) is remembered by all mathematical geologists for his elucidation of the matrix properties that bear his name.