Home  About us  Contact
 

Distinctive Elements (distinctive + element)

Distribution by Scientific Domains
Life Sciences40%
Humanities and Social Sciences40%

Selected Abstracts

Two conserved structural components, A-rich bulge and P4 XJ6/7 base-triples, in activating the group I ribozymes

GENES TO CELLS, Issue 12 2002
Yoshiya Ikawa
Background: The A-rich bulge of the group I intron ribozyme, a highly conserved structural element in its P5 peripheral region, plays a significant role in activating the ribozyme. The bulge has been known to interact with the P4 stem forming P4 XJ6/7 base-triples in the conserved core. The base-triples by themselves have also been identified as a distinctive element responsible for enhancing the activity of the ribozyme. Results: A weakly active variant of the Tetrahymena ribozyme lacking the P5 extension was dramatically activated by the addition of an A-rich bulge at the peripheral region, or by replacement of the original P4 XJ6/7 base-triples in the core structure with more stabilized isosteric ones. Biochemical analyses showed that the two methods of activation affect the ribozyme differently. Conclusions: The long-range interaction between the A-rich bulge and P4 or additionally stabilized P4 XJ6/7 base-triples can contribute dramatically to activation of the Tetrahymena ribozyme. Both improve the kcat value, which represents the rate of the limiting step of the ribozyme reaction when its binding site is saturated with GTP. However, the bulge or the modified base-triples gave a moderate reduction or considerable increase, respectively, to the Km(GTP) value. [source]

Self,Deception, Motivation, and the Desire to Believe

PACIFIC PHILOSOPHICAL QUARTERLY, Issue 4 2002
Dana K. Nelkin
In the debate over the nature of self,deception, "intentionalists" argue that self,deception requires an intention to deceive oneself, and "motivationists" argue that a desire, and not an intention, typically plays a crucial causal role in self,deception. Intentionalists have criticized motivationist views for ignoring what is distinctive about self,deception, and for failing to account for cases of "twisted" self,deception. I offer a new motivationist account whose distinctive element is the desire to believe. I argue that this account identifies what is common to cases of both "twisted" and "straight" self,deception, and that it captures what is distinctive about self,deception. [source]

REPRODUCTIVE ISOLATION CAUSED BY NATURAL SELECTION AGAINST IMMIGRANTS FROM DIVERGENT HABITATS

EVOLUTION, Issue 4 2005
Patrik Nosil
Abstract The classification of reproductive isolating barriers laid out by Dobzhansky and Mayr has motivated and structured decades of research on speciation. We argue, however, that this classification is incomplete and that the unique contributions of a major source of reproductive isolation have often been overlooked. Here, we describe reproductive barriers that derive from the reduced survival of immigrants upon reaching foreign habitats that are ecologically divergent from their native habitat. This selection against immigrants reduces encounters and thus mating opportunities between individuals from divergently adapted populations. It also reduces the likelihood that successfully mated immigrant females will survive long enough to produce their hybrid offspring. Thus, natural selection against immigrants results in distinctive elements of premating and postmating reproductive isolation that we hereby dub "immigrant inviability". We quantify the contributions of immigrant inviability to total reproductive isolation by examining study systems where multiple components of reproductive isolation have been measured and demonstrate that these contributions are frequently greater than those of traditionally recognized reproductive barriers. The relevance of immigrant inviability is further illustrated by a consideration of population-genetic theory, a review of selection against immigrant alleles in hybrid zone studies, and an examination of its participation in feedback loops that influence the evolution of additional reproductive barriers. Because some degree of immigrant inviability will commonly exist between populations that exhibit adaptive ecological divergence, we emphasize that these barriers play critical roles in ecological modes of speciation. We hope that the formal recognition of immigrant inviability and our demonstration of its evolutionary importance will stimulate more explicit empirical studies of its contributions to speciation. [source]

CO-OPTATION, COMMODIFICATION AND THE MEDICAL MODEL: GOVERNING UK MEDICINE SINCE 1991

PUBLIC ADMINISTRATION, Issue 2 2009
STEPHEN HARRISON
Self-regulation and autonomy are traditionally treated as distinctive elements of how professions are governed in contrast to other occupations. For medicine, these elements provide a collective medium of governance (through the institutions of professional self-regulation) and an individual medium (through the practice of 'clinical autonomy'). Both are reinforced by the intellectual dominance of the so-called 'biomedical model' of health and illness. Analysts generally agree that, in many countries, both self-regulation and clinical autonomy are under significant challenge. But it is less obvious that, in the UK at least, the biomedical model has effectively been co-opted for managerial purposes to support the commodification of medical care. Thus ideas that have traditionally been considered as supporting medical dominance have transpired to be a source of weakness for the profession. [source]

,BACK TO THE ROUGH GROUND!' WITTGENSTEINIAN REFLECTIONS ON RATIONALITY AND REASON

RATIO, Issue 4 2007
Jane Heal
Wittgenstein does not talk much explicitly about reason as a general concept, but this paper aims to sketch some thoughts which might fit his later outlook and which are suggested by his approach to language. The need for some notions in the area of ,reason' and ,rationality' are rooted in our ability to engage in discursive and persuasive linguistic exchanges. But because such exchanges can (as Wittgenstein emphasises) be so various, we should expect the notions to come in many versions, shaped by history and culture. Awareness of this variety, and of the distinctive elements of our own Western European history, may provide some defence against the temptation of conceptions, such as that of ,perfect rationality', which operate in unhelpfully simplified and idealised terms. [source]