Abstract. In this essay, I compare the atheism of Friedrich Nietzsche with that of Richard Dawkins. My purpose is to describe certain differences in their respective atheisms with the intent of showing that Nietzsche's atheism contains a richer and fuller affirmation of human life. In Dawkins’s presentation of the value of life without God, there is a naïve optimism that purports that human beings, educated in science and purged of religion, will find lives of easy peace and comfortable wonder. Part (...) of my argument is that this optimism regarding the power of objective science is subject to Nietzsche's criticism of Socrates and what he calls the “theoretical man.” As such, it fails in terms of providing a true affirmation of life in the godless world. (shrink)
With The Republic of Grace: Augustinian Thoughts for Dark Times, Charles Mathewes has given us a timely book that, I imagine, will be so for many times to come. His purpose throughout is to "offer a primer in the Augustinian-Christian vernacular, a language of religious, moral, and political deliberation" (2). This language and way of understanding reality, Mathewes argues, can provide us with ways of thinking about our own lives in the world as political and social creatures. The "dark times" (...) to which he refers in the subtitle have to do with life after 9/11 as citizens in a country that dominates as an economic and military powerhouse and greatly under the influence of what he calls "millennial capitalism" .. (shrink)
Galton and subsequent investigators find wide divergences in people's subjective reports of mental imagery. Such individual differences might be taken to explain the peculiarly irreconcilable disputes over the nature and cognitive significance of imagery which have periodically broken out among psychologists and philosophers. However, to so explain these disputes is itself to take a substantive and questionable position on the cognitive role of imagery. This article distinguishes three separable issues over which people can be "for" or "against" mental images. Conflation (...) of these issues can lead to theoretical differences being mistaken for experiential differences, even by theorists themselves. This is applied to the case of John B. Watson, who inaugurated a half-century of neglect of image psychology. Watson originally claimed to have vivid imagery; by 1913 he was denying the existence of images. This strange reversal, which made his behaviorism possible, is explicable as a "creative misconstrual" of Dunlap's "motor" theory of imagination. (shrink)
This debate, principally between myself (Nigel Thomas) and Patrick Hayes, the well known computer scientist and Artificial Intelligence researcher, took place through the internet mailing list for the discussion of the scientific study of consciousness, PSYCHE-D (moderated by Patrick Wilken), which is associated with the on-line journal PSYCHE. The discussion touches on the various different senses in which the expression "mental image" may be used, the underlying cognitive mechanisms of imagery, and the relevance of an understanding of imagery to (...) the understanding of conscious thought, and thought in general. As the debate became rather 'unthreaded' on the list, following it through this page may help the reader to better understand what was going on. (shrink)
This article was written as a commentary on a target article by Peter W. Ross entitled "The Location Problem for Color Subjectivism" [Consciousness and Cognition 10(1), 42-58 (2001)], and is published together with it, and with other commentaries and Ross's reply. If you or your library have the necessary subscription you can get PDF versions of the target article, all the commentaries, and Ross's reply to the commentaries here. However, I do not think that it is by any means essential (...) for you to have read Ross's piece in order to understand this one. Ross defends a view called "color physicalism" or color realism that holds (simplifying somewhat) that colors are real physical properties (in typical cases, spectral reflectances of object surfaces). This is in opposition to what is probably a more widely held "subjectivist" view of color, holding that color qualities really exist only in the mind. In my commentary I suggest that a realist view of qualitative properties, such as Ross's, together with a direct, active view of perception, and a concept of "extended mind" (Clark & Chalmers, 1998) may provide the materials for a real solution to the notorious hard problem of consciousness. I sketch this solution in outline. - N.J.T.T. (shrink)
Since the publication of my "Are Theories of Imagery Theories of Imagination? An _Active Perception_ Approach to Conscious Mental Content," (Thomas, 1999 - henceforth abbreviated as ATOITOI on this page), a good deal of published material has appeared or has come to my attention that either provides additional support for the Perceptual Activity Theory PA theory) of mental imagery presented in ATOITOI, or that throws further doubt on the rival (picture and description) theories that are criticized there. Other relevant (...) evidence was not mentioned in ATOITOI because I lacked the space for a proper explanation of its relevance. I hope eventually to write and publish a new account of
PA
theory, that will make use of much of this material. In the meantime this page provides citations (and, where possible, links) to the "new" support, and discussion sections that briefly explain the relevance of the cited material. Quite apart from presenting new lines of supporting evidence and argument, I hope this page will help to clarify many aspects of. (shrink)
Stich & Ravenscroft (1994) have argued that (contrary to most people's initial assumptions) a simulation account of folk psychology may be consistent with eliminative materialism, but they fail to bring out the full complexity or the potential significance of the relationship. Contemporary eliminativism (particularly in the Churchland version) makes two major claims: the first is a rejection of the orthodox assumption that realistically construed propositional attitudes are fundamental to human cognition; the second is the suggestion that with the advancement of (...) scientific understanding of the mind it will be possible to entirely eliminate the mentalistic and intentional from our ontology, thus dissolving the mind-body problem. The first claim (which has been argued in detail) supplies the principal grounds for accepting the second, much more ambitious and significant, claim. Robert Gordon's (1995, 1996, 2000) radical simulation theory of "folk psychology", proposed initially (Gordon, 1986) as an alternative to "theory theory" accounts of self and interpersonal understanding, but subsequently developing into a quite general challenge to symbolic computational accounts of mind, is not merely consistent with, but actually provides considerable additional support for, the first eliminativist claim. However, although radical simulationism has no use for reified propositional attitudes, it relies on another family of mentalistic and intentional notions, including perspective taking, "seeing as", pretending, imagery, and, most centrally, imagination. It is thus inconsistent with eliminativist metaphysical ambitions. Nevertheless, from this perspective the mind-body problem is transformed. Its solution no longer depends on accounting directly for the intentionality of the attitudes, but rather on accounting for the intentionality of imagination. Although standard accounts of imagination derive its intentionality from that of the attitudes, the recently proposed "perceptual activity" theory of imagery and imagination (Thomas, 1999) can provide a direct account of the intentionality of imagination that is consistent with physicalism.. (shrink)
The concepts of imagination and consciousness have, very arguably, been inextricably intertwined at least since Aristotle initiated the systematic study of human cognition (Thomas, 1998). To imagine something is ipso facto to be conscious of it (even if the wellsprings of imaginative creativity are in the unconscious), and many have held that our conscious thinking consists largely or entirely in a succession of mental images, the products of imagination (see, e.g., Damasio, 1994 -- or, come to that, see Aristotle, (...) or Hume, or almost any pre-twentieth century cognitive theorist). A venerable tradition also regards perceptual experiences, the main focus of most recent work on consciousness, as products of the imagination, whose primary function is to integrate sensory inputs and render them meaningful (Thomas, 1998, 1999). As Coleridge (1817) famously put it, primary imagination is "the living power and prime agent of all human perception." A better understanding of imagination is likely to deepen our insight into the nature of consciousness (and, probably, vice-versa). (shrink)
This article defends tradition and common sense against a widespread and rarely questioned contemporary philosophical orthodoxy that underpins the entrenched and exorbitant "lingualism" of so much 20th century thought, and leads the way to extreme doctrines like cognitive relativism and eliminative materialism. It also plugs what might otherwise have seemed to be a significant hole in the argument of my Are Theories of Imagery Theories of Imagination? (which I regard as my main positive contribution so far to the understanding of (...) the mind). For a relatively brief overview of the situation in cognitive theory and consciousness studies, as I see it, see A Stimulus to the Imagination. Click here to view the full article: Imagery and the Coherence of Imagination: a Critique of White. Earlier drafts of this article, one entitled "The White Images of Imagery and Imagination: A Critique and an Alternative", were formerly available on the net. Please make any citations to the published version. - N.J.T.T. (shrink)
Twentieth century philosophy and psychology have been peculiarly averse to mental images. Throughout nearly two and a half millennia of philosophical wrangling, from Aristotle to Hume to Bergson, images (perceptual and quasi-perceptual experiences), sometimes under the alias of "ideas", were almost universally considered to be both the prime contents of consciousness, and the vehicles of cognition. The founding fathers of experimental psychology saw no reason to dissent from this view, it was commonsensical, and true to the lived experience of conscious (...) thinking. However, early in this century, just about when the behaviorist revolution in psychology was loudly declaring the scientific illegitimacy of any attempt to study consciousness, and the concomitant non-existence of imagery (Watson, 1913; see Thomas, 1989), philosophy was undergoing its "linguistic turn", a turn to seeing philosophy as essentially about language rather than the world, even the 'inner' world. For decades, the very concept of the mental image was suspect, and it was certainly banished from playing any major role in theories of mind and of thinking. Ralph Ellis' Questioning Consciousness, together with the recent speculations of certain influential neuroscientists (Edelman, 1992; Damasio, 1994), may be signaling the end this unusual era. (shrink)
Commentary on "On Specification and the Senses," by Thomas A. Stoffregen and Benoît G. Bardy: Behavioral and Brain Sciences, 24, 195-261 (2001). The target article's value lies not in its defence of specification, or the "global array" concept, but in its challenge to the paradigm of 5+ senses, and its examples of multiple receptor types cooperatively participating in specific information pick-up tasks. Rather than analysing our perceptual endowment into 5+ senses, it is more revealing to type perceptual systems according to (...) task. (shrink)
We use a result due to Rolin, Speissegger, and Wilkie to show that definable sets in certain o-minimal structures admit definable parameterizations by mild maps. We then use this parameterization to prove a result on the density of rational points on curves defined by restricted Pfaffian functions.
We explore the issue of media content and corporate social responsibility by considering three questions:1. Why is this issue becoming so salient to a variety of stakeholders across the political spectrum at this time?2. What are the ethical issues that companies and policy makers should be concerned about with regard to media content?3. How can media-related companies and industries either better self-regulate or enhance consumer choice to respond to legitimate concerns about access tocontent?
Nigel J. T. Thomas (1998). Zombie Killer. In Stuart R. Hameroff, Alfred W. Kaszniak & A. C. Scott (eds.), Toward a Science of Consciousness II. MIT Press.score: 120.0
Philosopher's zombies are hypothetical beings behaviorally, functionally, and perhaps even physically indistinguishable from normal humans, but who lack our consciousness. Many people seem to be convinced that such zombies are a real conceptual possibility, and that this bare possibility entails that understanding human consciousness must remain forever beyond the reach of science. However, the conceptual entailments of zombiehood have not been sufficiently examined. This brief article shows that any way of understanding the behavior of zombies that does in fact support (...) the suggested entailment, leads to contradictions and absurdities. Zombies are _not_ conceptually possible. (shrink)
A comprehensive theory of the structure and cognitive function of the human imagination, and its relationship to perceptual experience, is developed, largely through a critique of the account propounded in Colin McGinn's Mindsight. McGinn eschews the highly deflationary (and unilluminating) views of imagination common amongst analytical philosophers, but fails to develop his own account satisfactorily because (owing to a scientifically outmoded understanding of visual perception) he draws an excessively sharp, qualitative distinction between imagination and perception (following Wittgenstein, Sartre, and others), (...) and because of his fatally flawed, empirically ungrounded conception of hallucination. In fact, however, an understanding of perception informed by modern visual science will enable us to unify our accounts of perception, mental imagery, dreaming, hallucination, creativity, and other aspects of imagination within a single coherent theoretical framework. (shrink)
Defining Imagery: Experience or Representation? Historical Development of Ideas about Imagery Subjective Individual Differences in Imagery Experience Theories of Imagery, and their Implications for Consciousness Picture theory Description theory Enactive theory.
Can theories of mental imagery, conscious mental contents, developed within cognitive science throw light on the obscure (but culturally very significant) concept of imagination? Three extant views of mental imagery are considered: quasi-pictorial, description, and perceptual activity theories. The first two face serious theoretical and empirical difficulties. The third is (for historically contingent reasons) little known, theoretically underdeveloped, and empirically untried, but has real explanatory potential. It rejects the "traditional" symbolic computational view of mental contents, but is compatible with recent (...) *situated cognition* and *active vision* approaches in robotics. This theory is developed and elucidated. Three related key aspects of imagination (non-discursiveness, creativity, and *seeing as*) raise difficulties for the other theories. Perceptual activity theory presents imagery as non-discursive and relates it closely to *seeing as*. It is thus well placed to be the basis for a general theory of imagination and its role in creative thought. (shrink)
Talents that selectively facilitate the acquisition of high levels of skill are said to be present in some children but not others. The evidence for this includes biological correlates of specific abilities, certain rare abilities in autistic savants, and the seemingly spontaneous emergence of exceptional abilities in young children, but there is also contrary evidence indicating an absence of early precursors of high skill levels. An analysis of positive and negative evidence and arguments suggests that differences in early experiences, preferences, (...) opportunities, habits, training, and practice are the real determinants of excellence. Key Words: exceptional ability; expertise; gift; innate capacity; music; potential; prodigy; specific ability; talent. (shrink)
Not long ago, I received an email from a man who had been trying to get his seven-year-old son interested in science, and teach him a little bit about the workings of the brain. He had been showing his son one of those diagrams of a brain with various regions labeled as "speech center," vision center," and the like (something similar to this, I suppose), when the little boy suddenly asked, "Daddy, which part of the brain does imagination come from?". (...) It was not on the diagram, and the father, although he studied human biology at college, realized he did not know the answer. As we do these days, he got on the internet to try to find out. It was not as easy as he might have expected. "Imagination" is certainly a word that is found on a lot of web pages, and there are plenty that seem to be devoted to celebrating or promoting it, but very few of them seem to have anything at all to say about what it is, how it works, or where in the brain it might be implemented. Eventually, he found his way to this site. Even here, however, he could find no straightforward answer to his son's apparently straightforward question. (The truth is, the question is not nearly as straightforward as it appears.) He thought I might be a good a person to ask, however, and sent me an email. What follows is a lightly revised version of the reply I sent. It is not written in terms that a seven-year-old could understand (I am not clever enough to do that), but neither is it pitched at the professional, academic level of most of the material on this site. I would like to think that it answers the question (inasmuch as it can be answered in the current state of scientific knowledge) in a way that a layperson should be able to understand, and that they might then be able to explain to a curious and intelligent child. If you want to know the detailed reasons, and see the citations to the scientific literature, that justify the claims made here, you can find them in the other articles on this site.. (shrink)
Mental imagery (varieties of which are sometimes colloquially refered to as “visualizing,” “seeing in the mind's eye,” “hearing in the head,” “imagining the feel of,” etc.) is quasi-perceptual experience; it resembles perceptual experience, but occurs in the absence of the appropriate external stimuli. It is also generally understood to bear intentionality (i.e., mental images are always images of something or other), and thereby to function as a form of mental representation. Traditionally, visual mental imagery, the most discussed variety, was thought (...) to be caused by the presence of picturelike representations (mental images) in the mind, soul, or brain, but this is no longer universally accepted. (shrink)
The principal temptation toward substance dualisms, or otherwise incorporating a question begging homunculus into our psychologies, arises not from the problem of consciousness in general, nor from the problem of intentionality, but from the question of our awareness and understanding of our own mental contents, and the control of the deliberate, conscious thinking in which we employ them. Dennett has called this "Hume's problem". Cognitivist philosophers have generally either denied the experiential reality of thought, as did the Behaviorists, or have (...) taken an implicitly epiphenomenalist stance, a form of dualism. Some sort of mental duality may indeed be required to meet this problem, but not one that is metaphysical or question begging. I argue that it can be solved in the light of Paivio's "Dual Coding" theory of mental representation. This theory, which is strikingly simple and intuitive (perhaps too much so to have caught the imagination of philosophers) has demonstrated impressive empirical power and scope. It posits two distinct systems of potentially conscious representations in the human mind: mental imagery and verbal representation (which is not to be confused with 'propositional' or "mentalese" representation). I defend, on conceptual grounds, Paivio's assertion of precisely two codes against interpretations which would either multiply image codes to match sense modes, or collapse the two, admittedly interacting, systems into one. On this basis I argue that the inference that a conscious agent would be needed to read such mental representations and to manipulate them in the light of their contents can be pre-empted by an account of how the two systems interact, each registering, affecting and being affected by developing associative processes within the other. (shrink)
The so called "Knowledge Argument" of Frank Jackson (1982, 1986) 1 claims to show that there is something about the human mind that must inevitably escape the grasp of physical science: "There are truths about . . . people ( . . . ) which escape the physicalist story" (Jackson, 1986). In effect, materialism is false, and science, as opposed to metaphysics, cannot hope to attain to an understanding of consciousness.
Classical and medieval writers had no term for consciousness in anything like the modern sense, and their philosophy seems not to have been troubled by the mind-body problem. Contemporary eliminativists find strong support in this fact for their claim that consciousness does not exist, or, at least, is not an appropriate scientific explanandum. They typically hold that contemporary conceptions of consciousness are artefacts of Descartes' (now outmoded) views about matter and his unrealistic craving for epistemological certainty. Essentially, they say, our (...) belief in consciousness is a residue of once pressing, but now irrelevant, intellectual tensions between religion and the rising new science of the Early Modern period. With the attempts of Descartes and his successors to resolve these tensions, Western thought began down a track toward the conceptual cul-de-sac of the "hard problem". Plausibly, the problem will only be (dis)solved, and the onward march of science assured, when we are able to shake off the pervasive influence of the Cartesian tradition in a way that goes far beyond the mere rejection of dualism. But when we do so, eliminativists contend, the distinctively Cartesian notion of consciousness will simply drop out of our world-picture, like phlogiston or the vital entelechy. (shrink)
To the best of my knowledge, with the exception of Galton's original work (1880, 1883), Sommer's brief case study (1978), and Faw's (1997, 2009) articles, this is the only really substantial discussion of the phenomenon of non-brain-damaged "non-imagers" available anywhere.
This Response addresses eight issues raised in the commentaries: (1) the question of how innate talents should be defined; (2) relationships between the talent account and broader views concerning genetic variability; (3) the quality of the empirical evidence for and against the talent account; (4) the possible involvement of innate influences on specific abilities; (5) the possibility of talent-like phenomena in autistic savants; (6) alternative explanations of exceptional expertise at skills; (7) practical and educational implications of the talent account and (...) alternative positions. Finally, (8), we conclude by discussing the impact of the commentaries on our own views. (shrink)
A comprehensive theory of the structure and cognitive function of the human imagination, and its relationship to perceptual experience, is developed, largely through a critique of the account propounded in Colin McGinn's Mindsight. McGinn eschews the highly deflationary (and unilluminating) views of imagination common amongst analytical philosophers, but fails to develop his own account satisfactorily because (owing to a scientifically outmoded understanding of visual perception) he draws an excessively sharp, qualitative distinction between imagination and perception (following Wittgenstein, Sartre, and others), (...) and because of his fatally flawed, empirically ungrounded conception of hallucination. In fact, however, an understanding of perception informed by modern visual science will enable us to unify our accounts of perception, mental imagery, dreaming, hallucination, creativity, and other aspects of imagination within a single coherent theoretical framework. (shrink)
Pylyshyn's critique is powerful. Pictorial theories of imagery fail. On the other hand, the symbolic description theory he manifestly still favors also fails, lacking the semantic foundation necessary to ground imagery's intentionality and consciousness. But, contrary to popular belief, these two theory types do not exhaust available options. Recent work on embodied, active perception supports the alternative perceptual activity theory of imagery.
The interlocutors of Plato’s Cratylus agree that “it is far better to learn and to inquire from the things themselves than from their names” (439b6–8). Although surprisingly little attention has been paid to these remarks, at least some commentators view Plato as articulating a preference for direct, nonlinguistic cognitive access to the objects of inquiry. Another commentator takes Plato simply to recommend first-hand, yet linguistic, experience in addition to instruction from experts. This paper defends, in contrast to both interpretations, (...) the view that inquiry without names is dialectical, linguistic inquiry into metaphysical first principles. As such, inquiry without names is (logically) prior to inquiry from or through names. Inquiry without names is a form of transcendental metaphysics. (shrink)
There was a brief inaugural session of the Association for the Scientific Study of Consciousness during the Psychonomic Society Conference in Los Angeles in November 1995, but the first full conference of the Association was held this June in the very pleasant surroundings of the Claremont Colleges. Being at this conference was very different from being at Tucson II the previous year. This was a less ballyhooed, more intimate event, maybe less exciting, and less intellectually eclectic, but also perhaps more (...) conducive to serious scientific exchange. Certainly the roster of speakers was replete with luminaries of the consciousness studies movement, and highly respected names from psychology, neuroscience, and philosophy: Christof Koch, Bernard Baars, Ned Block, Philip Merikle, Daniel Schacter, Larry Jacoby, Walter Freeman, Valerie Hardcastle, both Churchlands, Melvyn Goodale, Owen Flanagan . . . to unfairly pick out just a few. (shrink)
Until a few years ago, Cognitive Science was firmly wedded to the notion that cognition must be explained in terms of the computational manipulation of internal representations or symbols. Although many people still believe this, the consensus is no longer solid. Whether it is truly threatened by connectionism is, perhaps, controversial, but there are yet more radical approaches that explicitly reject it. Advocates of "embodied" or "situated" approaches to cognition (e.g., Smith, 1991; Varela _et al_ , 1991, Clancey, 1997) argue (...) that thought cannot be understood as entirely internal. Furthermore, it is argued that autonomous robots can be designed to behave more intelligently if representationalist programming techniques are avoided (Brooks, 1991), and that the way our brains control our behavior is better understood in terms of chaos and dynamical systems theory rather than as any sort computation (e.g., Freeman & Skarda, 1990; Van Gelder & Port, 1995; Van Gelder, 1995; Garson, 1996). (shrink)
We have synthesized a 582,970-base pair Mycoplasma genitalium genome. This synthetic genome, named M. genitalium JCVI-1.0, contains all the genes of wild-type M. genitalium G37 except MG408, which was disrupted by an antibiotic marker to block pathogenicity and to allow for selection. To identify the genome as synthetic, we inserted "watermarks" at intergenic sites known to tolerate transposon insertions. Overlapping "cassettes" of 5 to 7 kilobases (kb), assembled from chemically synthesized oligonucleotides, were joined by in vitro recombination to produce intermediate (...) assemblies of approximately 24 kb, 72 kb ("1/8 genome"), and 144 kb ("1/4 genome"), which were all cloned as bacterial artificial chromosomes in Escherichia coli. Most of these intermediate clones were sequenced, and clones of all four 1/4 genomes with the correct sequence were identified. The complete synthetic genome was assembled by transformation-associated recombination cloning in the yeast Saccharomyces cerevisiae, then isolated and sequenced. A clone with the correct sequence was identified. The methods described here will be generally useful for constructing large DNA molecules from chemically synthesized pieces and also from combinations of natural and synthetic DNA segments. 10.1126/science.1151721. (shrink)
This book is a philosopher's examination of the dispute, which raged amongst cognitive psychologists in the 1970s, and has continued to sputter on since, about the nature of mental imagery. As Tye sees things (and, indeed, as the textbooks generally have it) on the one side of the issue we find Stephen Kosslyn and certain close associates, arguing that mental images are best understood on analogy with pictures; and on the other side we find Zenon Pylyshyn, ably seconded by Geoffrey (...) Hinton, arguing that the pictorial analogy is thoroughly misleading, and should be replaced by an analogy to descriptions. Tye's consideration of this debate, attempting to clarify and arbitrate a tangled mess of argument and to explore the implications of what he takes to be the proper outcome, is generally excellent. If you want to understand the strengths of the arguments of Kosslyn, Pylyshyn, and their allies, then this book is to be recommended very warmly. (shrink)
This paper is a reading of Schelling’s 1809 treatise Of Human Freedom in light of its relationship to the question why? and the principle of sufficient reason.This “principle of ground” defines the limits of rational inquiry and poses substantial difficulties for the three central themes of Schelling’s text: God, freedom,and the reality of evil. God and freedom go beyond the principle by requiring an absolute beginning—a ground that is not itself grounded. Evil defies rationalexplanation, deriving its existence from a specifically (...) human freedom to do evil. Schelling’s text traces God, freedom, and evil back to their origin at the momentwhen God’s existence and its ground “sprung forth” from the non-ground. Here at the origins of ground the principle of reason no longer applies. (shrink)
This study examined the effect of various antecedent variables on marketers’ perceptions of the role of ethics and socialresponsibility in the overall success of the firm. Variables examined included Hofstede’s cultural dimensions (i.e., power distance, uncertainty avoidance, individualism, masculinity, and Confucian dynamism), as well as corporate ethical values and enforcement ofan ethics code. Additionally, individual variables such as ethical idealism and relativism were included. Results indicated that most ofthese variables impacted marketers’ perceptions of the importance of ethics and social responsibility, (...) although to varying degrees. (shrink)
A study is reported which focused on the problem-solving strategies employed by expert electronics engineers pursuing a real-world task: integrated-circuit design. Verbal protocol data were analysed so as to reveal aspects of the organisation and sequencing of ongoing design activity. These analyses indicated that the designers were implementing a highly systematic solution-development strategy which deviated only a small degree from a normatively optimal top-down and breadth-first method. Although some of the observed deviation could be described as opportunistic in nature, much (...) of it reflected the rapid depth-first exploration of tentative solution ideas. We argue that switches from a predominantly breadth-first mode of problem solving to depth-first or opportunistic modes may be an important aspect of the expert's strategic knowledge about how to conduct the design process effectively when faced with difficulties, uncertainties, and design impasses. (shrink)
Lanthanide bioprobes and bioconjugates are ideal luminescent stains in view of their low propensity to photobleaching, sharp emission lines and long excited state lifetimes permitting time-resolved detection for enhanced sensitivity. In this paper, we expand our previous work which demonstrated that self-assembled dinuclear triple-stranded helicates [Ln2(LC2X)3] behave as excellent cell and tissue labels in immunocytochemical and immunohistochemical assays. The synthetic strategy of the hexadentate ditopic ligands incorporating dipicolinic acid, benzimidazole units and polyoxyethylene pendants is revisited in order to provide a (...) more straightforward route and to give access to further functionalization of the polyoxyethylene arms by incorporating a terminal function X. Formation of the helicates [Ln2(LC2X)3] (X=COOH, CH2OH, COEt, NH2, phthalimide) is ascertained by several experimental techniques and their stability tested against diethylenetriaminepentaacetate. Their photophysical properties (quantum yield, lifetime, radiative lifetime and sensitization efficiency) are presented and compared with those of the parent helicates [Ln2(LC2)3]. Finally, the cellular uptake of five EuIII helicates is monitored by time-resolved luminescence microscopy and their localization in HeLa cells established by co-staining experiments. (shrink)
