bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mankind in polar habitats
Authors: Fogg G E 
Published: November 2023

Abstract
Only recently have the enormous areas around the poles been invaded by mankind (Sugden 1982; Ives and Sugden 1995). The Arctic, being nearer to centres of population and approachable by land, was the first to suffer intrusion. This came via the unglaciated lowland of northeast Siberia and the Beringia peninsula (p. 47) which was occupied by groups of people hunting mammoth, bison, and caribou with stone-tipped spears and living in winter in semi-subterranean dwellings. This Palaeo-Arctic culture persisted until around 7000 BP but long before, perhaps 20 000 BP, it had spread across the then existing land bridge to North America. About 11 000BP the climate became warmer, ice caps melted, and the land connection with Asia was cut by the rising sea, leaving the primitive Arctic hunters to evolve in isolation. Those that remained in coastal areas lived on sea mammals, muskoxen, and caribou, and gave rise to the palaeo-Eskimo who reached northern Greenland about 3000 years BP. Another group, the Dorset culture, with the same origin, moved to the eastern Canadian Arctic and developed the building of ice houses (igloos), boats (umiaks and kayaks), and efficient harpoon technology for hunting on ice. This exploitation of sea mammals was the key to successful occupation of the high Arctic.
Life at the Bottom
Authors: Herring Peter 
Published: November 2023

Abstract
The organisms furthest away from the surface productivity are, of course, those at the bottom of the ocean. The title of this chapter recognizes that this special fauna includes those that live on, in, and just above the seafloor. The first two categories comprise the benthos (cf. plankton and nekton), and respectively describe what are technically known as the epifauna and the infauna.
On being efficient
Authors: Herring Peter 
Published: November 2023

Abstract
In open water food is often reliably available in particular regions or seasons (e.g. in many coastal regions and/or springtime). In these circumstances animals are neither constrained to get the last calorie out of their diet nor is energy conservation a high priority. One frequent result is fast-swimming, solidly muscular animals with skeletons to match. Another is ‘messy’ feeding, in which carnivores scatter scraps of prey and herbivores eat more than they can process, allowing a considerable portion of the ingested phytoplankton to pass through the gut unabsorbed.
Chemical Messages
Authors: Herring Peter 
Published: November 2023

Abstract
The oceanic habitat is awash with organic compounds released deliberately or accidentally by the organisms that live within it. Seawater not only bathes the outer surface of an organism but in most multicellular animals it also travels through it, down the gut lumen. Every living organism is effectively a leaky bag of organic molecules, with survival being dependent upon achieving the right balance of molecular input and output, both qualitatively and quantitatively.
Introductory comments: Xenopus as a laboratory animal
Authors: Gurdon J B 
Published: November 2023

Abstract
Xenopus laevis, the South African clawed frog, has come to be, together with the mouse and the chick, the vertebrate species most widely used for research in the areas of developmental, cell and molecular biology. This somewhat surprising situation arose from the use of X. laevis about 50 years ago as an assay for pregnancy in humans; the injection of a few millilitres of urine from a pregnant woman under the female frog’s skin, into the dorsal lymph sac, causes it to lay eggs. From around the 1950s, this was replaced by a more convenient form of pregnancy test, but it was apparent that Xenopus can be induced to mate and provide fertile embryos by the gonadotrophic hormones (primarily luteinizing hormone) of other vertebrate species. This characteristic is not shared by Rana species in which the same result requires the injection of homogenized pituitary glands from several adults, a procedure that is very laborious and extremely wasteful of animals. Even then, fertile eggs can be obtained from Rana only during certain months of the year, as is also true of other amphibians such as newts and salamanders (Triturus) which were favourite objects of research for great names in the field of experimental embryology including Spemann, Holtfeter, etc.
Historical constraints and morphological novelties in the evolution of the skeletal system of pipid frogs (Anura: Pipidae)
Authors: Trues Linda 
Published: November 2023

Abstract
IPipid frogs of the genera Xenopus, Silurana, Hymenochirus, Pseudhymenochirus and Pipa are dissimilar to all other living anurans and highly derived rather than primitive. Among living pipids, Xenopus is the most primitive-i.e., the most similar to the hypothesized ancestor of the Pipidae. Nonetheless, the adults of this taxon possess many morphological features that distinguish them from their closest living non-pipid relatives, Rhinophrynus dorsalis (Rhinophrynidae) and the pelobatoid frogs. Many of the morphological novelties seem to be associated with the evolution of an aquatic anuran from a terrestrial saltatorial ancestor. The sprawled, laterally positioned limbs and dorsoventral compression of the body in pipids that facilitate their swimming inhibit their hopping or jumping and are correlated with modifications of the thigh musculature and structures of the pectoral and pelvic girdles. Movement of the trunk is limited to anterior-posterior shifts of the pelvic girdle on the sacrum; dorsal-ventral rotation of the posterior trunk, which is critical to saltatorial locomotion, is not possible. Many cranial modifications in Xenopus seem to be associated with its mode of feeding without a tongue, but little is known about the feeding mechanism. The mandible is robust, whereas the upper jaw is weak and suspended from the skull by a modified suspensory apparatus. The hyolaryngeal apparatus is highly modified. The plectra! apparatus is hypertrophied and the tympanic annulus is ossified and in synostosis with the dermal squamosal medially. The orbital region of the braincase is depressed and formed by membrane, rather than endochondral, bone.
Molecular approaches to the phylogeny of Xenopus
Authors: Graf Jean-Daniel 
Published: November 2023

Abstract
Comparative molecular studies of Xenopus species have addressed four main ques¬tions: (1) the monophyly or polyphyly of the genus Xenopus, (2) the subdivisions of the genus and the relationships among species groups, (3) the age of major splitting events within the genus, (4) the age of polyploidization events. The first question has been examined in two studies, based on immunological distances and ribosomal DNA sequences, which strongly suggest that the genus Xenopus, including X. tropicalis, is monophyletic with respect to Hymenochirus. The second question has been considered in several studies using electrophoresis of proteins, peptide mapping of albumin or restriction mapping of mtDNA. Different criteria produce different classifications, although some consensus is obtained on the existence of a tropicalis group, a fraseri group and a laevis group. A partial answer to the third question has been provided by a comparison of nucleotide sequences of globin genes: the divergence between the two most distant species groups, i.e. the tropicalis group and the rest of the genus, is estimated to be about 120 million years old. The same study has produced a tentative answer to the fourth question: the divergence time between the homoeologous globin genes of the tetraploid-derived X. laevis is estimated at about 40 to 60 million years ago. However, if tetraploidy resulted from allopolyploidization, then this estimate corresponds to the age of the diploid parental species, and not to the date of polyploidization, which remains unknown.
Adaptations to life in running waters
Authors: Giller Paul S , Malmqvist Björn 
Published: November 2023

Abstract
From one perspective, terrestrial and aquatic habitats are similar in that they consist of a fluid (gaseous atmosphere or liquid water) overlying a solid (land surface or river or lake bed sediments). However, the greater density of water provides mechanical support that allows a vast array of aquatic organisms to live ‘free from contact with the ground’ suspended in the fluid medium, particularly in the oceans and lakes. It also means that any movement of the denser water is also or much greater and more immediate importance for aquatic organisms than air movements arc for terrestrial ones. The challenges to life in streams and rivers arc therefore going to be different from those in terrestrial systems, and as a consequence, we find unique adaptations among the lotic biota, some of’ which we explore in this chapter.
Community patterns, diversity, and biogeography
Authors: Giller Paul S , Malmqvist Björn 
Published: November 2023

Abstract
Freshwater biologists have traditionally lagged somewhat behind their terrestrial colleagues in studying the structure and function of communities, but in the recent past this situation has changed and there is now a considerable literature developing. However, this is not an ecology book and as such we cannot delve too deeply into this burgeoning literature. we have discussed various aspects of lotic communities elsewhere in this book, including longitudinal patterns and the River Continuum Concept (pp. 165-9) and the role of species interactions (pp. 182-92). we have also seen how various physical and chemical factors and disturbances influence aquatic communities and the distribution and abundance of species in Chapter 3. So, here, we will concentrate on a few other important community patterns and processes including resource partitioning, succession, persistence, trophic structure, and food webs, then turn to a consideration of species diversity in streams and rivers and finally to the larger scale biogeographic distribution patterns.
Systematics of sea snakes: a critical review
Authors: Rasmussen Arne Redsted 
Published: November 2023

Abstract
The taxonomy of elapid sea snakes is reviewed. There is no general agreement on generic and suprageneric relationships. The problematic genera are reviewed on the basis of published data and personal observations. Sea snakes form a group of aquatic snakes with a vertically flat paddle-like tail, which is not found in any other terrestrial or aquatic snakes. Sea snakes belong to the same group as terrestrial elapids; they are all characterized by the anterior position of the poison-fangs on the maxillary bone (proteroglyphous) (McCarthy 1985).
Systematics of the Bothrops atrox complex: new insights from multivariate analysis and mitochondrial DNA sequence information
Authors: Wuster W , Salomao G M , Thorpe R S , Puorto G , Furtado M F D , Hoge S A , Theakston R D G , Warrell D A 
Published: November 2023

Abstract
We use multivariate analysis of morphological characters and comparative sequencing of a 520 bp fragment of the cytochrome b gene (mitochondrial DNA) to investigate patterns of geographic variation in the Bothrops atrox species complex, and the population phylogeny of the group in parts of South America. Populations conventionally assigned to B. atrox and B. moojeni constitute morphologically distinct groupings, with a zone of phenetically intermediate specimens where their ranges meet. Bothrops marajoensis, B. isabelae, B. leucurus and B. pradoi are poorly differentiated or undifferentiated from B. atrox and each other. Phylogenetic analysis of the cytochrome b sequence information reveals that B. caribbaeus constitutes an outgroup to the South American populations of the B. atrox complex. Within the South American radiation, the conventional species, as generally understood, largely lack historical reality. Two well-corroborated basal dades are revealed: one includes the populations from the lower Amazon and Tocantins-Araguaia drainages, as well as Marajo Island. The other comprises two further basal clades within it, the first consisting of the populations conventionally assigned to B. moojeni, the other a number of populations from the eastern coast of Brazil, various places in western and central Amazonia and western Venezuela. Mantel matrix correlation tests show morphological variation among the populations of the complex to be most strongly associated with vegetation type. This suggests that morphological variation represents primarily an adaptation to current selection pressures, probably for crypsis, and not a reflection of population phylogeny.
Moas and kiwis
Authors: Davies S J J F , Bamford Michael J , Loomes Danika 
Published: November 2023

Abstract
The moas inhabited New Zealand, probably surviving into the nineteenth century. None ,were collected from life by Europeans but sub-fossil remains have been extensively studied. Anderson (1989) has provided a comprehensive recent review of the group and the information given at appropriate places in the introductory chapters of this book is based on his work. It remains only to provide a formal classification. which follows Bock and Biihler (1988) for the higher categories and Anderson (1989) and Brodkorb (1963) for the lower ones.
An introduction to reefs
Authors: Wood Rachel 
Published: November 2023

Abstract
The term ‘reef’ derives from the Old Norse nautical term rif,meaning a hazardous ‘rib’ of rock, sand, or biological material that lies close to the surface of the sea. But as organic constructions of calcium carbonate, the term reef has evolved different scientific meanings from its original nautical usage, such that now no definition is universally accepted by ships’ captains, biologists, and geologists. Consider the diversity of the following four examples.1. Living coral reefs grow to sea level in clear, tropical waters and may cover many square kilometres. They are constructed by large, heavily calcified organisms (mainly corals and coralline algae) whose growth is driven by photosynthesis. Such reefs show mechanical resistance to all but the most vigorous currents and storms, and often form steep walls in the face of severe wave impact.
Molecular Structure And Its change
Authors: Bader Richard F W 
Published: November 2023

Abstract
The essential understanding and original intent associated with the notion of structure in chemistry is that it be a generic property of a system. Structure originally implied the existence of a particular network of bonds, which was presumed to persist over a range of nuclear displacements until some geometrical parameter attained a critical value at which point bonds were assumed to be broken and/or formed to yield a new structure. However, the word ‘structure’ has over the years acquired a duality of meanings. This has occurred for two reasons. The first was a result of our inability to unambiguously assign a network of bonds to a given system. The second was a result of our ever-increasing ability to experimentally measure the geometrical parameters which characterize the minimum energy nuclear configuration of a system within the Born—Oppenheimer model. Thus, if one references the heading ‘molecular structure’ in early books on descriptive chemistry, one finds a discussion of valency and bonding and of models for assigning a network of bonds. Referenced under the same heading in present-day physical chemistry or spectroscopy texts are discussions of the experimental methods used to determine the bond lengths and bond angles which are used to characterize an equilibrium geometrical structure.
The Action Principle For A Quantum Subsystem
Authors: Bader Richard F W 
Published: November 2023

Abstract
It has been demonstrated in Chapter 5 that Schrodinger’s original derivation of the wave equation can be generalized to provide a quantum description of an atom in a molecule. His derivation uses the calculus of variations as applied to an energy functional of Ψ and its extension to an atom in a molecule entails two essential steps: the introduction of a particular type of operator through its identification with the variation of the state function and a variation of the surface bounding the atomic subsystem.
Notation
Authors: Altmann Simon L 
Published: November 2023

Abstract
Whereas no chemist would these days treat, say, molecular vibrations without using the vocabulary of group theory, there is, unfortunately, no elementary introduction to the band theory of solids which adopts this approach. There are, of course, excellent books on the group theory of the solid state, but they are all at a rather rigorous level and are not suitable as an introduction to band theory. Almost twenty years ago I wrote such an introduction in which I made much use of the concept of symmetry, but I could not employ the vocabulary of group theory since undergraduates in the physical sciences were not exposed to this subject in those days. Finite group theory is now the lingua franca of chemistry and many undergraduate courses in physics include some group theory. I felt, therefore, that the time had now come to have a book which would bridge the gap between the current elementary texts on band theory and the more advanced treatments of the group theory of solid state.
Symmetry and group theory: a revision
Authors: Altmann Simon L 
Published: November 2023

Abstract
A lump of metal was considered in Chapter 1 as if it had no internal structure at all, the surface of the metal acting as the walls of a container inside which a free-electron gas is to be found. Even in this case we did find a degeneracy which arises from the isotropy of the space in which the electrons move: the pair of free-electron states corresponding to the values k and - k of the wave vector must be degenerate. (See§1–3.) We shall want in the rest of this book, of course, to introduce the effect of the crystal structure on the electron states and we must expect many more, and more complicated, symmetries which, as we shall see, will lead also to more complicated degeneracies. The study of these degeneracies is essential: if we did not know, for example, that the level 2p of the free sodium atom is six-fold degenerate, we would get the electronic structure of this atom hopelessly wrong. As we shall remind ourselves in this chapter, the study of degeneracy is very much simplified by using some simple ideas of group theory. We shall expect the reader to have some familiarity with these ideas, as treated for instance in the well-known textbook of physical chemistry by Atkins (1990, Chapter 15).
Space groups
Authors: Altmann Simon L 
Published: November 2023

Abstract
We have learnt in Chapter 2 how group theory allows us to classify the degeneracies of a physical system, as long as we know its symmetry group. Symmetry groups of crystals are substantially more involved than those of molecules and they are called space groups. We must learn some of their properties in order to be able to study those of the energy eigenvalues in crystals.
The reciprocal lattice and the Fourier series
Authors: Altmann Simon L 
Published: November 2023

Abstract
A crystal pattern is periodic in the translation lattice, that is, it is obtained in its (infinite) entirety by repeated translations of the unit cell, these translations thus providing periodicity along each of the corresponding directions. As a result, many functions of physical importance in the crystal will be periodic .functions which, once defined inside the unit cell, are then known throughout the crystal by the periodicity condition. An important example of this situation is the crystal potential, but we shall see that various other periodic functions play a very important part in the study of bands in crystals.
Bloch functions and Brillouin zones
Authors: Altmann Simon L 
Published: November 2023

Abstract
We have proved in § 1–3 that, in free space, the momentum eigenfunctions are eigenfunctions of the energy (see eqn 1–3.6), and these momentum eigenfunctions have just been written as the plane waves I k&gt; in (4–10.2), labelled by a propagation vector k in the reciprocal lattice. We want to consider in this chapter the electrons moving in the crystal not just as free particles but rather under the influence of the crystal potential field. In these circumstances, we cannot expect the energy eigenfunctions to continue being the plane waves I k &gt;, although, when we obtain their general form, we shall see that they are deeply related to them. (It is in fact for this reason that we have paid so much attention to these plane waves.)
Brillouin zones and energy bands
Authors: Altmann Simon L 
Published: November 2023

Abstract
We shall start this chapter by considering a three-dimensional Brillouin zone, which will serve us as an example in order to study the properties of the Brillouin zone faces. After this, we shall go back to a one-dimensional example so as to be able to discuss in detail various schemes which are used in order to plot energy bands and Fermi surfaces in k space.
Phonons and conductivity
Authors: Altmann Simon L 
Published: November 2023

Abstract
We have already used more than once the idea that electrical conductivity is due to the fact that the electric field promotes electrons which are near the Fermi level to unoccupied levels above it. We have then assumed that the size of the Fermi surface is a determining factor in conductivity, a point which we shall confirm and refine in § 1. Once this is done we shall see that, because the electric field provides a constant acceleration to the Fermi electron sea, a mechanism must be found which prevents this process from continuing indefinitely, since otherwise a steady state of conduction by the electrical carriers would never be achieved. We must therefore discover in what way the electrons may be scattered and thus slowed down. There are two ways in which this may happen. One is through electron-electron collisions, but this, of course, cannot affect the energy of the electron sea as a whole, whereas it is this energy which we must ensure does not run up to infinity. A second possible mechanism is by collisions between the electrons and the crystal structure. We shall see, though, that a perfect, that is, a rigid crystal cannot exchange energy with the electron sea. It is only a vibrating crystal that can do this, as we shall discover when we study crystal vibrations, which will lead us to the important concept of the phonon.
Wannier functions and Lowdin orbitals
Authors: Altmann Simon L 
Published: November 2023

Abstract
Plane waves and Bloch functions, which have so far been our tools for describing electron states in solids, are delocalized functions which extend throughout the crystal. When dealing with localized phenomena, such as impurities or surface states, it is useful to replace the Bloch functions or the plane waves by functions which are, as far as possible, localized. This means that whereas the Bloch functions are labelled by the different k vectors of the Brillouin zone, the functions we seek, which are called the Wannier functions, must be labelled in terms of the different primitive cells of the crystal. This does not mean that they are entirely localized within each cell but, because each function is associated with one primitive cell, a degree of localization might be achieved, as we shall see later on (§ 2) is in fact the case.