The literature on the early embryonic development of the vertebral column in various animal species was analyzed to evaluate so many unrelated or contradictory observations. The recurring problems are described. One of the first was the lack of correspondence between the metameric boundaries of the ‘primitive vertebral bodies’ arising from the somites and those of the adult vertebral bodies, as presumably shown by their relationship to the vertebral processes and spinal nerves. A century ago, Remak introduced the concept of ‘Neugliederung’, (...) according to which the ultimate vertebral body boundaries are determined by a shift of a half segment in comparison with the earlier segment boundaries. (shrink)

Localised configurations of the free electromagnetic field are constructed, possessing properties of massive, spinning, relativistic particles. In an inertial frame, each configuration travels in a straight line at constant speed, less than the speed of lightc, while slowly spreading. It eventually decays into pulses of radiation travelling at speedc. Each configuration has a definite rest mass and internal angular momentum, or spin. Each can be of “electric” or “magnetic” type, according as the radial component of the magnetic or electric field (...) vanishes in the rest frame, and each has an “antiparticle.” Any such configuration, of electric or magnetic type, is characterized in part by a set of labels (κ, ω0, σ,l, m), where ω0 is the mean of the angular frequencies of the plane waves making up the configuration, σ is the variance of those frequencies, κ is a positive constant with dimensions of action, andl, m are angular momentum “quantum numbers” withl a positive integer andm an integer such that ‖m‖≤l. The rest energy of the “particle” is κω0, its spin is κ ‖m‖, and its lifetime is of the order of 1/σ. Its antiparticle has ω0 replaced by −ω0. (shrink)

Phantom limb experiences demonstrate an unexpected degree of fragility inherent in our self-perceptions. This is perhaps most extreme when congenitally absent limbs are experienced as phantoms. Aplasic phantoms highlight fundamental questions about the physiological bases of self-experience and the ontogeny of a physical, embodied sense of the self. Some of the most intriguing of these questions concern the role of mirror neurons in supporting the development of self–other mappings and hence the emergence of phantom experiences of congenitally absent limbs. In (...) this paper, we will examine the hypothesis that aplasic phantom limb experience is the result of an ontogenetic interplay between body schemas and mirror neuron activity and that this interplay is founded on embedding in a social context. Phantom limb experience has been associated with the persistence of subjective experience of a part of the body after deafferentation through surgical or traumatic removal. We maintain that limited association is inconsistent with the extent to which phantom limb experience is reported by aplasic individuals. (shrink)

Deterministic models in population dynamics often are really approximations to stochastic models, justified by an appeal to the law of large numbers. It is proposed to call such models pseudodeterministic. Four questions are discussed in this article: (1) What errors may be made by equating deterministically predicted values to expectations? (2) When, and in what sense, may numbers be assumed to be large? (3) How large are the variances, coefficients of variations, etc., as assigned to the variables in the stochastic (...) versions of the models? (4) What role may pseudodeterministic models play in empirical research, where problems of statistical reliability arise?As an example, a modified Nicholson-Bailey model of the interaction between insect parasitoids and their hosts is discussed; the modification consists of assigning a random (density-independent) mortality to the parasitoid population. A stochastic version of this model is discussed. The expectation of the final host density is compared with the value computed from the deterministic model. The latter value is systematically lower than the former. The magnitude of the difference depends on parameter values. The variability to be expected with the stochastic model is characterized by the coefficient of variation of the final host density; its dependence on parameter values and initial conditions is discussed. It is concluded that it is worthwhile in practical applications to estimate parasitoid mortality, and that the coefficient of variation in real situations may be far from negligible. (shrink)

This book addresses the theme of global sustainable development across two dimensions.First it introduces its progress and prospects in both rich and poor countries. It then outlines the major trends that will in practice influence the direction of sustainable development into the next century. It encompasses an understanding of sustainable development as both a theoretical framework for thinking about how to deal with human needs and environmental limits on the one hand, and a more material understanding of it as a (...) set of practices, on the other.The book is written by a group of internationally-recognised experts in the field, and is distinctive in offering a variety of philosophical and ethical reflections on sustainable development. Core issues covered include economic growth, poverty reduction, future generations, technology, population and diversity, making it an ideal text for students.Key Features: The only available text to introduce the philosophical and ethical issues surrounding sustainable developmentContributors are internationally-renowned experts in the field and include activists and policy makers, as well as academicsCore areas include global equality, technology, women and populationAn ideal course textbook for Politics, Philosophy and International Relations student. (shrink)

In this paper we describe a test for Nijhout's hypothesis that the eyespot patterns on butterfly wings are the result of a threshold reaction of the epidermal cells to a concentration gradient of a diffusing degradable morphogen produced by focal cells at the centre of the future eyespot. The wings of the nymphalid butterfly, Bicyclus anynana, have a series of eyespots, each composed of a white pupil, a black disc and a gold outer ring. In earlier extirpation and transplantation experiments (...) it has been established that these eyespots are indeed organised around groups of signalling cells active during the first hours of pupal development. If these cells were to supply the positional information for eyespot formation in accordance with Nijhout's diffusion-degradation gradient model, then, when two foci are close together, the signals should sum, and this effect should be apparent in the detailed shape of the resulting pigment pattern. We give an equation for the form of the contours that would be obtained in this manner. We use this to test the morphogen gradient hypothesis on measurements of the outlines of fused eyespots obtained either by grafting focal cells close together, or by using a mutation that produces adjacent fused eyespots. The contours of the fused patterns were found to satisfy our equation, thus corroborating Nijhout's hypothesis to the extent possible with this particular type of experiment. (shrink)

Recent controversy over philosophical advocacy of infanticide (or the comically-styled euphemism ‘postnatal abortion’) reveals a surprisingly common premise uniting many of the opponents and supporters of the practice. This is the belief that the moral status of the early fetus or embryo with respect to a right to life is identical to that of a newly born or even very young baby. From this premise, infanticidists and strong anti-abortionists draw opposite conclusions, the former that the healthy newly born have no (...) inherent right to life and the latter that minute embryos and the very early fetus have the same right to life as young babies. (Indeed strong anti-abortionists tend to regard this right to life as identical to that possessed by adult humans.) This paper argues that these opposed conclusions are both deeply implausible and that the implausibility resides in the common premise. The argument requires some attention to the structure of the philosophical case underpinning the supposed vice of speciesism that has been given intellectual currency by many philosophers, most notably Peter Singer, and also to the reasoning behind the strong anti-abortionist adoption of the common premise. (shrink)

Recent policy in relation to clinical research proposals in the UK has distinguished between two types of review: scientific and ethical. This distinction has been formally enshrined in the recent changes to research ethics committee structure and operating procedures, introduced as the UK response to the EU Directive on clinical trials. Recent reviews and recommendations have confirmed the place of the distinction and the separate review processes. However, serious reservations can be mounted about the science/ethics distinction and the policy of (...) separate review that has been built upon it. We argue here that, first, the science/ethics distinction is incoherent, and, second, that RECs should not only be permitted to consider a study’s science, but that they have anobligation do so. (shrink)

Originally published in 1969. This volume was composed by an eminent Sufi mystic whilst in prison in Baghdad, awaiting execution, in a vain attempt to overthrow his sentence; he was put to death in AD 1311 at the age of 33. This apologia is a document of great poignancy, composed in most elegant Arabic and translated with the customary skill and elegance for which A J Arberry became so well-known.

The divine attributes of omniscience and omnipotence have faced objections to their very consistency. Such objections rely on reasoning parallel to semantic paradoxes such as the Liar or to set-theoretic paradoxes like Russell's paradox. With the advent of paraconsistent logics, dialetheism—the view that some contradictions are true—became a major player in the search for a solution to such paradoxes. This paper explores whether dialetheism, armed with the tools of paraconsistent logics, has the resources to respond to the objections levelled against (...) the divine attributes. (shrink)

A number of recent papers have described the successful derivation of egg and sperm precursor cells from mouse embryonic stem cells—so-called “artificial” gametes. Although many scientific questions remain, this research suggests numerous new possibilities for stem cell research and assisted reproductive technology, if a similar breakthrough is achieved with human embryonic stem cells. The novel opportunities raised by artificial gametes also prompt new ethical questions, such as whether same-sex couples should be able to access this technology to have children who (...) are genetically related to them both.THE CREATION OF “ARTIFICIAL” GAMETESOver the past two years, a number of papers have been published detailing the first successful attempts at differentiating mouse embryonic stem cells into egg1 and sperm2 precursor cells. Previously, researchers had used embryonic stem cells to generate tissues such as brain, liver, and pancreatic cells, but not germ cells of any kind. Production of gamete precursor cells was achieved initially through allowing stem cell lines to differentiate more or less randomly, but recent research has focused on identifying the precise ways in which differentiation into gametes can be precipitated and controlled. These breakthroughs make it seem likely that ongoing research on human stem cells will yield similar possibilities,3 raising questions over the practicalities of what might be achieved with such “artificial” gametes. In turn, the novel opportunities presented by artificial gametes raise a number of ethical concerns.The initial breakthrough, namely the obtaining of egg cells from mouse stem cells, was achieved by means of relatively simple science. Rather than coaxing stem cells to develop into eggs using complicated cocktails of growth factors, researchers adopted standard cell culture conditions, but grew the cells at higher density than usual.3–6 Growing the cells in this way led to the formation of ovary-like cell aggregates, which (when separated and stimulated with …. (shrink)