bluuebunny/crossref_metadata_2025_split huggingface dataset:
The role of collagens and proteoglycans in tumour angiogenesis
Authors: Rooney P , Kumar P , Ponting, J , Kumar S 
Published: November 2023

Abstract
The natural history of tumour development and growth is well established. A population of cells within a host is exposed to an initiation factor and a new wave of gene expression occurs, removing normal growth constraints from the primary tumour (1,2). The primary tumour can grow to approximately 1-2 mm in diameter but will grow no further unless it is vascularized (3-5). Tumour angiogenesis is a multistep cascade of events which proceeds only when a proportion of cells within the tumour, estimated to be less than 10% (6,7), switches to an angiogenic phenotype, and releases factors which either act directly on endothelial cells of neighbouring blood vessels or stimulate surrounding stromal tissue to release factors which act on the endothelial cells. Once activated, endothelial cells are induced to degrade local extracellular matrix (ECM), migrate through the ECM, proliferate, and reach the tumour.
Living, Growing, and Daylight
Authors: Herring Peter 
Published: November 2023

Abstract
Life on earth derives its existence, survival, and success from primary production, namely the biological synthesis of complex organic molecules using inorganic sources of carbon and an external source of energy. The open-ocean ecosystem is similar to the terrestrial one, both in this fundamental principle and in the biochemical pathways invoked, but the players and the controlling processes are very different. The deep-sea fauna are dependent upon them.
Control of thyroid hormones and their involvement in haemoglobin transition during Xenopus and Rana metamorphosis
Authors: Just John J , Kraus-Just Jeanne 
Published: November 2023

Abstract
It has been known for 75 years that thyroid hormones (THs) are involved in amphibian metamorphosis. In the last 25 years several investigators have shown that at or near the time of tail loss there is a sudden rise in circulating TH concentrations that is dependent on the pituitary and hypothalamus. The required pituitary hormone is thyroid stimulating hormone (TSH); however, c:irculating TSH concentrations have yet to be determined during metamorphosis. During the last decade much effort focused on measurements of thyrotropin releasing hormone (TRH) concentrations in the tissues of several anuran tadpoles, but there is no credible evidence showing that TRH can directly initiate metamorphic climax in any species. Recent data suggest that other hypothalamic hormones are involved in the control of TSH concentrations and therefore TH concentrations before climax. During metamorphosis THs are known to control cell death, stem cell stimulation and differentiation of existing cell populations. In order for larval tissues to respond to THs, they must have TH receptors. Several different types of TH receptors exist and all are members of a larger group of nuclear protein receptors that include receptors for THs, steroid hormones and retinoic acid. More recent evidence suggests that larval tissue TH receptor concentrations change during metamorphosis and that their concentrations are highest about the time of tail loss. The transition from larval to adult haemoglobin is used to document both hormonal and environmental factors involved in the control of this metamorphic process.
Parasites of Xenopus
Authors: Tinsley F C 
Published: November 2023

Abstract
The Xenopus species carry a richer assemblage of parasites than most other anurans, with over 25 genera from seven invertebrate groups. This spectrum reflects a dual origin: some of the parasites are characteristic of anurans and represent ‘heirlooms’ from a common ancestry of parasites which have evolved with the anuran lineages. In addition, a component of the fauna is related to parasites which typically infect fishes: these represent ecological acquisitions and reflect the overlap, in terms of diet, habitats etc., between Xenopus and fish. For both these subsets of parasites, the representatives infecting Xenopus are highly distinctive, with life-history and other specializations which are often unique within the respective parasite groups. From a systematic point of view, they are best interpreted as having had a very distant origin from their nearest relatives and having now diverged to the point where almost all forms infecting Xenopus are placed in their own genera, families or higher taxonomic categories, strictly specific to Xenopus. Some of the parasites exploit Xenopus as an intermediate host and await passage to final hosts which are predators of Xenopus (and usually also of fish). These parasites may be pathogenic, infecting the heart, body musculature, eyes and lateral line system: by interfering with normal function, infection increases the risks of predation and thus facilitates completion of the parasite’s life cycle. Other parasites employ Xenopus as a final host (in which their sexual reproduction occurs), and invade by a variety of routes (with the diet, by vector transfer, or by direct penetration of an active infective stage). For most of these parasites, pathogenic effects are difficult to detect and infection levels tend to occur below the point at which damage may be serious. The skin-infecting nematode, Pseudocapillaroides xenopodis, is exceptional in its pathogenicity, being responsible for lethal epidemics amongst laboratory-maintained X. laevis.
The immune system of Xenopus: with special reference to B celI development and immunoglobulin genes
Authors: Pasquier Louis Du , Wilson Melanie , Robert Jacques 
Published: November 2023

Abstract
The immunoglobulin genes of Xenopus are organized in a manner similar to those of bony fish, birds and mammals, with multiple families of variable region elements, multiple Ds (for the heavy chain), multiple J segments, but a single gene foreach constant region. B cells, in which these gene segments rearrange to build up functional immunoglobulin genes, develop early in larval life and express a repertoire of antibodies different from that of the adult and restricted by the small numbers of lymphocyte clones. The comparison of larval and adult cDNAs showed that the N diversification which contributes to the adult complexity of the third hypervariable region of heavy chains is missing in tadpoles. The adult repertoire is less heterogeneous than that of mammals, presumably because somatic hypermutations occurring in the V genes are not properly selected. Some polyploid species retained polysomic inheritance of immunoglobulin genes, whereas they functionally diploidized their major histocompatibility complex. A lymphoid cell line with a larval phenotype with two complete lg heavy chain rearrangements has been isolated from a thymus tumour and grown in vitro: while expressing cell surface markers of a T cell, its immunoglobulin gene rearrangements are more typical of a B cell. This may contribute a new tool for Xenopus biologists in the future.
Running waters: a unique habitat
Authors: Giller Paul S , Malmqvist Björn 
Published: November 2023

Abstract
Uisce Bea/ha is Irish for whiskey but it actually translates as ‘Water of Life’. While some may see this as the raison d’être for water, this phrase has a rather different connotation lo the aquatic biologist, as water provides the very habitat in which aquatic life exists. Aquatic ecosystems range from the open oceans and intertidal marine systems, to freshwater lakes and streams and rivers. There will obviously be some overlap in the patterns and processes among these systems and trying to identify these similarities can only further our understanding of the natural world. However, there is sufficient that is unique about streams and rivers, the subject or this volume, to make their study an intriguing and rewarding experience.
Design concepts - birds that don’t fly
Authors: Davies S J J F , Bamford Michael J , Loomes Danika 
Published: November 2023

Abstract
First of all, loss of the ability to fly removes a restriction on size. The largest Recent flying bird is the great bustard Otis tarda, a male of which has been reliably recorded as weighing 18 kg (Cramp and Simmons 1980), with an unconfirmed record of 21 kg. As birds increase in size, the force of the flight muscles does not increase as rapidly as the mass of the bird and this places an upper limit on the size of flying birds.
Ratites and tinamous in the future
Authors: Davies S J J F , Bamford Michael J , Loomes Danika 
Published: November 2023

Abstract
In the last five hundred years more than half the recent species of large ratites have become extinct, including all the moas and elephant birds and two of the three emus. Two of the three kiwis are greatly reduced in number. Amongst the tinamous, several are now endangered. Although it is difficult to prove, it is also difficult to avoid the conclusion that most of these extinctions and declines are related, directly or indirectly, to the activities of humans. Clearing of woodland and forest impacts very severely on birds that evolved under stable conditions ,where food was abundant and cover plentiful.
Ostrich and elephant birds Family Struthionidae Vigors 1825
Authors: Davies S J J F , Bamford Michael J , Loomes Danika 
Published: November 2023

Abstract
Largest living birds. Bill broad and depressed, the culmen with a strong, rounded tip overlapping the mandible. The nostrils lie in a membranous groove near the middle of the bill. There are no clavicles, the tibia is without a bony bridge, the after shaft is absent and in the alimentary canal, the caecae and rectum arc large. Wings are short and imperfect, with long soft plumes; the tail is also of long, curved soft plumes.
Mass extinctions: collapse and recovery
Authors: Wood Rachel 
Published: November 2023

Abstract
The previous chapter emphasized the importance of disturbance for maintaining the high diversity of modern coral reef communities. The response of reefs to events which cause catastrophic disturbance is, however, highly complex and depends on the timing, intensity, and history of events. Indeed, some combinations of disturbances can act synergistically to cause seemingly permanent shifts in the composition of individual reef communities. But it is now clear that while reef biotas (and therefore ecosystems) may be robust to environmental variability over both ecologically and geologically significant timescales, reefs themselves are relatively fragile, transient phenomena. And we have seen that over even longer timescales, a succession of different ecosystems have formed reefs over the past 3.5 Ga, and that the ‘incumbency’ of many of these long-lived ecosystems was terminated by mass extinctions.
Mathematical Models Of Structural Change
Authors: Bader Richard F W 
Published: November 2023

Abstract
The definition of structure obtained through the application of the equivalence relation to the gradient vector fields of the charge density leads to the partitioning of nuclear configuration space into a finite number of structural regions. The boundaries of these regions denote the configurations of the unstable structures. This information enables one to construct a system’s structure diagram, a diagram which details all of its stable structures and all of the unstable structures that are transitional in form between those of neighbouring structural regimes. The collection of the structurally unstable points in nuclear configuration space R, is called the catastrophe set C. As a corollary of the theorem of structural stability stated by Palis and Smale (1970) one finds that only two types of catastrophe points are possible a configuration X∈ R is structurally unstable if and only if its associated charge density ρ (r; X) exhibits (a) at least one degenerate critical point, also known as a singularity in the charge density or (b) a non-transversal intersection of the stable and unstable manifolds of a pair of its critical points. A configuration satisfying either (a) or (b) is called a bifurcation or conflict point, respectively.
Methods of calculation of band structures
Authors: Altmann Simon L 
Published: November 2023

Abstract
In parallel with the development of modern computers in the last twenty or thirty years, several methods for the calculation of the energy eigenvalues E(k) in crystals have been perfected, and computer programs now exist which make the calculation of band structures a fairly routine matter. Some results of such calculations have already been discussed in the last chapter. No attempt, however, will be made in this chapter to give an account of the accurate methods of numerical calculation now available. The discussion will concentrate instead on the methods that provide some simple, although approximate, insights into the main features of band structures.
Phase stability: Brillouin zone effects
Authors: Altmann Simon L 
Published: November 2023

Abstract
Copper is face-centred cubic but, when zinc is added to it, this phase eventually becomes unstable and it changes over to the body-centred cubic structure. It is possible to explain such changes of phase by considering the change in the Fermi energy which takes place when the Fermi surface expands (as it must, for increasing electron concentrations) until it touches a face of the Brillouin zone. We shall study in the first few sections of this chapter the rules which determine such phase transformations in alloys. We shall then consider another effect which is due to the properties of the Fermi energy at the Brillouin zone edges, and which requires that regular one-dimensional chains be unstable with respect to transformations into structures with alternating short and long bonds. This effect is called the Peierls instability.
Surface and impurity states
Authors: Altmann Simon L 
Published: November 2023

Abstract
We have so far seen that the electron states of a periodic structure are described by Bloch functions which form energy bands as a function of k, and that these bands are such that, in general, forbidden energy gaps exist between them. It is reasonable to expect, on the other hand, that electrons which arise from impurities or from surface states in the crystal will not give rise to periodic states and will not, therefore, be described by Bloch functions. We must expect, accordingly, that the corresponding energies may appear in the forbidden energy gaps, as will be confirmed in this chapter. The first thing which we shall do is to look for the possible existence of states in the gap, and this will lead in§ 1 to the Tamm states. We shall then consider a simple model of surface states (Shockley states) in§ 2. A more detailed method of calculation of surface and impurity states, proposed by Koster and Slater, will be discussed in § 3 and will serve as a simple introduction to the use of Green functions. A practical example of this treatment will be given in § 4.
Lariat ethers
Authors: Gokel George W 
Published: November 2023

Abstract
The award of the 1987 Nobel prize in chemistry to Charles J. Pedersen, Donald J. Cram, and Jean-Marie Lehn provided important recognition to the field called variously ‘macrocycle chemistry’, ‘host-guest chemistry’, ‘supramolecu lar chemistry’ or ‘molecular recognition’. In its essence, the field encompasses the study of non-covalent interactions that occur between hosts and guests or substrates and receptors of many different types. Although Liittringhaus had previously prepared examples of what are now known as crown ethers (e.g. (1)), Pedersen recognized their importance as cation binders when he uncovered these compounds in the 1960s. Lehn elaborated these macrocycles into macrobicyclic ‘cryptands’ (e.g. (2)) or three-stranded crown ethers that can completely envelop a cation, anion, or other molecular species.
Bridged pyridine hosts
Authors: Bell Thomas W , Sahni Suresh K 
Published: November 2023

Abstract
The popularity of pyridine as a structural unit m macrocycles is largely explained by its unique combination of coordination properties. Pyridine’s dipole moment (2.2D; ID= 3.34 × 10 Cm) coincides with the orientation of its nonbonded electron pair, leading to stable solvates and u-complexes with metal cations and other Lewis acids. Low-lying π* molecular orbitals further stabilize pyridine complexes of transition metals by d-electron back bonding. Pyridine is also an effective hydrogen-bond acceptor, while pyridinium ions and pyridones are good hydrogen-bond donors. Thus, bridged pyridine hosts can be used to form complexes with hard or soft metals or with charged or neutral molecular guests.
Clathrasils and zeosils: inclusion compounds with silica host frameworks
Authors: Gies Hermann 
Published: November 2023

Abstract
The structural analogy of crystalline phases of ice and crystalline phases of silica is well known and has been reviewed by several authors.1 In 1981, structure determinations of the mineral melanophlogite2 and synthetic ZSM-39 (dodecasil 3C),3 isostructural with the clathrate hydrates of Type I and II respectively, expanded that relationship to include clathrate-type compounds. In 1983, the name clathrasils was introduced for a family of silica host-frameworks. In a new general classification scheme for porous tectosilicates proposed by Barrer5 and expanded by Liebau et al., clathrasils and zeosils are branches of the porosils, a subclass of the porous tectosilicates, which comprises all silica end endmembers with the general formula [SiO2]
The structural chemistry and reactivity of organic guests in layered aluminosilicate hosts
Authors: Thomas John M , Theocharis Charis R 
Published: November 2023

Abstract
There has been an explosive growth in the studies carried out on sheet aluminosilicate intercalates since the subject was last reviewed by one of us1 in 1982. In this series of publications, reference to inclusion compounds based on layered silicate hosts has hitherto been brief (see Chapter 7, Volume 1). There are many reasons for the enhanced interest: first, more powerful techniques are now available to probe the nature of the wide variety of guest-host systems discovered within this family of solids; second, an ever-widening range of catalytic reactions has been discovered with aluminosilicates as the precursor catalyst; third, there is considerable scope for exquisite modification of both the parent layered solid and also the resulting solid intercalate.
Porphyrins for the future
Authors: Milgrom Lionel R 
Published: November 2023

Abstract
The porphyrins we have dealt with so far are naturally occurring, and are involved in the light-harvesting reactions of photosynthesis and the electron-or oxygen-transporting and storage functions of cellular metabolism. Synthetic porphyrins are also useful, and, as our knowledge progresses, the number of applications is expanding. Sophisticated porphyrin derivatives are already being tried out in laboratories around the world in a wide variety of applications, including medicine, electronics, and alternative energy generation. However, before we examine some of these new applications, we should start with a lucky fluke that led to one of the most successful families of synthetic pigments ever invented—the phthalocyanines.1 These blue to green pigments now have a wide variety of uses, including artists’ colours, printing inks (especially for bank notes), surface coatings, paper dyes, floor coverings, and even as high temperature lubricants for space vehicles. But the success of synthetic pigments like the phthalacyanines is relatively recent.
Crystallographic studies of inter- and intra-molecular interactions
Authors: Krygowski Tadeusz M 
Published: November 2023

Abstract
Inter- and intra-molecular interactions of chemical species are of primary importance in chemical research. They influence chemical reactivity and are associated with changes in the geometry of the chemical species involved. Hence, knowledge of the precise geometry of chemical systems is valuable as the starting point for understanding their chemical{ physical and biological properties (Hoffmann, 1983). The most effective way to study molecular geometry is by crystallography with X-ray and (to a lesser extent) neutron diffraction on crystals. The thousands of crystal and molecular structures solved and published annually mean that thousands of geometries of chemical species become available for interpretation.
Strain in cyclo-annulated aromatic systems
Authors: Boese R , Blaser D , Niederprum N , Miebach T 
Published: November 2023

Abstract
One of the essentials for organic crystal structure investigations is the availability of a single crystal. Because of the special problems of investigation and the difficulties in handling crystals of highly strained molecules, which are usually extremely sensitive to heat or are liquid under ambient conditions, the first part of this contribution will describe the techniques for crystallizing samples and for getting them onto the diffractometer without damage.
Influence of electric field on polymorphism in isotactic polypropylene
Authors: Paukszta D , Garbarczyk J , Sterzynski T 
Published: November 2023

Abstract
As happens with small molecules, polymorphism often also occurs in synthetic polymers. Thus, polyethylene crystallizes in orthorhombic and triclinic forms, polypropylene in monoclinic and orthorhombic forms (Wunderlich 1973; Samuels, Yee 1972; Neapolitano, Pirozzi 1986). These polymers provide examples of this phenomenon and of transformations between the different forms. One among several factors that can lead to the formation of one, rather than another, of the polymorphic modifications is the addition of specific low molecular weight compounds to the polymers.
Phasing at low resolution
Authors: Roth M 
Published: November 2023

Abstract
The specificity of low resolution diffraction is that it does not depend on local atomic order but is determined only by the local scattering length density in the unit cell and by the translational symmetry of this density in the crystal. An important domain of application of low resolution diffraction is, therefore, the structure determination of systems showing local atomic disorder. Examples of such cases are the studies of RNA in a virus (Bentley et al., 1987), detergent micelles in membrane protein crystals (Zulauf et al., 1986; Roth et al., 1989) , lipid domains in lipoproteins (Banaszak el al., 1989). Another application is the structural study of large complex systems which often do not diffract to atomic resolution. They may also be too large to be phased by heavy atom derivative techniques. This domain of application is probably going to become more important in the future, with the development for instance of structural studies of ribosomes (Yonath et al., 1989; Trakhanov et al., 1989).
Accurate solutions of the maximum entropy equations. Their impact on the foundations of direct methods
Authors: Navaza J 
Published: November 2023

Abstract
Information theory provides a conceptually clear framework where the importance of the many possible combinations of data and prior knowledge can be assessed. The theoretical interest of the formulation resides in the independence of the maximum entropy estimates, with respect to missing information. Its major contribution is perhaps the new insight it gave to the foundations of direct methods (Bricogne, 1984). Most procedures based on the maximum entropy principle produce estimates m(r) of the electron density function p(r), which agree with the experimental data. Then, according to the non- committance of the method, if some expected property of the electron density is not displayed by the estimated map, we can safely conclude that the data and prior information used to construct it, were not sufficient enough to bring out the sought property. Despite the attractive qualities of the formulation, some difficulties are encountered when trying to apply it to the phase problem: