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Dead End (dead + end)
Selected AbstractsSOCIALITY IN THERIDIID SPIDERS: REPEATED ORIGINS OF AN EVOLUTIONARY DEAD ENDEVOLUTION, Issue 11 2006Ingi Agnarsson Abstract Evolutionary ,dead ends' result from traits that are selectively advantageous in the short term but ultimately result in lowered diversification rates of lineages. In spiders, 23 species scattered across eight families share a social system in which individuals live in colonies and cooperate in nest maintenance, prey capture, and brood care. Most of these species are inbred and have highly female-biased sex ratios. Here we show that in Theridiidae this social system originated eight to nine times independently among 11 to 12 species for a remarkable 18 to 19 origins across spiders. In Theridiidae, the origins cluster significantly in one clade marked by a possible preadaptation: extended maternal care. In most derivations, sociality is limited to isolated species: social species are sister to social species only thrice. To examine whether sociality in spiders represents an evolutionary dead end, we develop a test that compares the observed phylogenetic isolation of social species to the simulated evolution of social and non-social clades under equal diversification rates, and find that sociality in Theridiidae is significantly isolated. Because social clades are not in general smaller than their nonsocial sister clades, the spindly phylogenetic pattern,many tiny replicate social clades,may be explained by extinction rapid enough that a nonsocial sister group does not have time to diversify while the social lineage remains extant. In this case, this repeated origin and extinction of sociality suggests a conflict between the short-term benefits and long-term costs of inbred sociality. Although benefits of group living may initially outweigh costs of inbreeding (hence the replicate origins), in the long run the subdivision of the populations in relatively small and highly inbred colony lineages may result in higher extinction, thus an evolutionary dead end. [source] LIBYA: Migrant Dead End?AFRICA RESEARCH BULLETIN: ECONOMIC, FINANCIAL AND TECHNICAL SERIES, Issue 6 2010Article first published online: 3 AUG 2010 No abstract is available for this article. [source] Public-service values and ethics: Dead end or strong foundation?CANADIAN PUBLIC ADMINISTRATION/ADMINISTRATION PUBLIQUE DU CANADA, Issue 4 2007Ralph Heintzman This article reconsiders Langford's arguments. It suggests that public-service renewal requires ongoing attention to public-service values but also a widening of perspectives. It is now necessary to give more attention to the organizational, professional and institutional conditions for sound individual behaviour. Renewed attention to public-service values did not seek to supplant traditional approaches to individual decision-making but rather to re-frame them, grounded in the principles without which they cannot make sense of the world. The research literature on values and ethics contradicts the critique's main contentions. The critique is also based on a mistaken premise, false dichotomies, and inadequate and contradictory assumptions about the nature of individual decision-making. Three points that are useful contributions to the ongoing dialogue on public-service values and ethics are noted. But an individual perspective must now be augmented by a focus on organizational performance. Far from being a "dead end," public-service values remain the strong foundation , the only possible foundation , for the public service of the future. Sommaire: Le présent article réexamine celui de John Langford, publié dans le numéro d'hiver 2004, dans lequel il prononqait un verdict négatif sur la préoccupation au sujet des valeurs du service public qui a été un élément de la réforme de la fonction publique au cours de la dernière décennie. Une nouvelle attention portée aux valeurs du service public n'a pas cherchéà remplacer les approches traditionnelles concernant la prise de décisions, mais plutôt à les recadrer, à les faire reposer sur des principes sans lesquels le monde n'a pas de sens. La littérature de recherche sur les valeurs et l'éthique conrredit les principales allégations du critique et est également fondée sur des assomptions erronées et contradictoires au sujet de la nature de la prise de décision individuelle. Trois points qui représentent des contributions utiles au dialogue actuel sur les valeurs et l'éthique du service public sont mentionnés. Mais la perspective individuelle doit aussi avoir pour objectif la performance organisarionnelle. Loin d'être une « voie sans issue », les valeurs du service public restent le fondement solide , et en fait le seul fondement possible , du service public de l'avenir. [source] Dead ends and new directionsASTRONOMY & GEOPHYSICS, Issue 5 2008Article first published online: 23 SEP 200 No abstract is available for this article. [source] SOCIALITY IN THERIDIID SPIDERS: REPEATED ORIGINS OF AN EVOLUTIONARY DEAD ENDEVOLUTION, Issue 11 2006Ingi Agnarsson Abstract Evolutionary ,dead ends' result from traits that are selectively advantageous in the short term but ultimately result in lowered diversification rates of lineages. In spiders, 23 species scattered across eight families share a social system in which individuals live in colonies and cooperate in nest maintenance, prey capture, and brood care. Most of these species are inbred and have highly female-biased sex ratios. Here we show that in Theridiidae this social system originated eight to nine times independently among 11 to 12 species for a remarkable 18 to 19 origins across spiders. In Theridiidae, the origins cluster significantly in one clade marked by a possible preadaptation: extended maternal care. In most derivations, sociality is limited to isolated species: social species are sister to social species only thrice. To examine whether sociality in spiders represents an evolutionary dead end, we develop a test that compares the observed phylogenetic isolation of social species to the simulated evolution of social and non-social clades under equal diversification rates, and find that sociality in Theridiidae is significantly isolated. Because social clades are not in general smaller than their nonsocial sister clades, the spindly phylogenetic pattern,many tiny replicate social clades,may be explained by extinction rapid enough that a nonsocial sister group does not have time to diversify while the social lineage remains extant. In this case, this repeated origin and extinction of sociality suggests a conflict between the short-term benefits and long-term costs of inbred sociality. Although benefits of group living may initially outweigh costs of inbreeding (hence the replicate origins), in the long run the subdivision of the populations in relatively small and highly inbred colony lineages may result in higher extinction, thus an evolutionary dead end. [source] Interfacing biocatalysis and organic synthesis,JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 12 2007Roland Wohlgemuth Abstract The path to new chemical entities often shows the limitations of existing tools both in biocatalysis and organic chemistry. Organic synthetic procedures to prepare a compound in a target-oriented synthesis can damage other functional parts of the molecule. Protection,deprotection schemes can lead to a dead end, when a certain protecting group cannot be cleaved off. In biocatalysis, on the other hand, the required biocatalytic toolbox and methodology might not be readily available, therefore limiting a biocatalytic approach. New toolboxes, ingredients, and methodologies at the interface of classical organic synthesis and biocatalytic reactions bridge the gap between these two areas. Since product isolation and purification involves a substantial amount of time in the preparation of chemicals, methodologies to simplify these tasks are necessary to get the pure product into the bottle with less work-up time. Efficient and safe new pharmaceuticals, intermediates and analytical reagents need to be prepared under certain safety, health, environmental and economical boundary conditions. Biocatalytic reactions have been shown to overcome these limitations successfully and are becoming increasingly important in industrial manufacturing. Building bridges between biocatalysis and organic synthesis will therefore create roads to new synthetic strategies and technological frontiers of both fundamental and practical interest. Copyright © 2007 Society of Chemical Industry [source] Tracing the route of Sphaerospora truttae from the entry locus to the target organ of the host, Salmo salar L., using an optimized and specific in situ hybridization techniqueJOURNAL OF FISH DISEASES, Issue 11-12 2003A S Holzer Abstract Sphaerospora truttae is an important pathogen of Atlantic salmon parr in Scottish aquaculture. To trace the early development of S. truttae and to overcome the common problem of detecting low numbers of cryptic, early myxosporean stages, a DNA-based approach was applied in this study. Specific primers were designed for S. truttae from Atlantic salmon, based on 18S rDNA sequences, obtained from isolated myxosporean spores. These were 5, biotin-labelled and used in an optimized and rapid in situ hybridization (ISH) protocol, which provided a strong and specific signal of the parasite within host tissue sections and, at the same time, minimized structural damage to tissues due to processing. This methodology provided a reliable tool enabling the detection of S. truttae stages down to single cell level. Using ISH the epithelium of the gills was identified as the predominant entry locus of the parasite. By 3 days after infection S. truttae had penetrated the vascular epithelia and thereafter proliferated in the blood for at least 10 days before exiting the vascular system through capillary walls. From day 12 post-infection onwards, the kidney, as well as the spleen and the liver, were invaded. Numbers of S. truttae invading the kidney (37.3%) differed little from numbers found in the spleen (35.3%) and the liver (27.4%). The latter organs represented a dead end in the development of S. truttae as all stages in these organs degenerated and sporogony was found to take place exclusively inside the renal tubules. Early sporogonic stages were found from day 25 post-infection but mature spores only developed after at least 15 days of proliferation within the tubules. [source] Intra-oral Dirofilaria repens infection: report of seven casesJOURNAL OF ORAL PATHOLOGY & MEDICINE, Issue 8 2003W. M. Tilakaratne Abstract Cutaneous dirofilariasis usually affects animals such as cats and dogs which are known to be the natural host of Dirofilaria. Dirofilariasis displays a worldwide distribution. Certain geographic regions account for the majority of reported cases. South-eastern United States, Australia and Europe have been identified as endemic regions (1, 2). However, new endemic areas are arising with increased awareness in African and Asian regions. Out of about 40 different species of Dirofilaria only a few species are commonly known to infect man, namely Dirofilaria immitus, D. tenices and D. repens. Human infection occurs when a human becomes a blood meal of an infected arthropod vector and on accidental entering of the worm. Rarely this zoonotic infection affects the oral mucosa (3). Man is the dead end of this parasite. Since the human body is an abnormal environment for the parasite, the development of the larvae is inhibited by means of retardation of sexual maturity. Lesions are presented as single non-tender subcutaneous nodules, and most patients are asymptomatic. Diagnosis is established by H&E sections prepared from excised nodules. In a majority of the cases, only a single worm either a male or a female could be identified. The worm is usually dead and degenerated with a massive inflammatory cell infiltration. Seven new cases presented as intra-oral nodules with their clinicopathological correlation are discussed. [source] Acting on values: An ethical dead end for public servantsCANADIAN PUBLIC ADMINISTRATION/ADMINISTRATION PUBLIQUE DU CANADA, Issue 4 2004John W. Langford The central tenet of this approach is that a framework of core values can be used directly by public servants to solve ethical dilemmas or to justify more specific rules of behaviour. The author argues that this approach is conceptually flawed on a number of levels. Its advocates seem confused about what a value is and how to identify core values. They also seem tolerant of the existence of a large number of core values that are not clearly defined. This inevitably creates a situation in which there is substantial value conflict and no way to resolve such clashes. Finally, the values approach, at least as structured in Ottawa, subdivides values into groups, making a puzzling distinction between ethical and non-ethical values. After examining these flaws, the article explores the need to pay more attention to consequentiality approaches for enhancing ethical behaviour that resonate with the ways in which public servants intuitively approach ethical judgments. Sommaire: Cet article fait une analyse critique de l'éthique dans le secteur public fondée sur les valeurs, plus particulièrement la façon dont cette approche a étéélaborée à Ottawa. Cette approche repose essentiellement sur le principe que les fonctionnaires peuvent se servir d'un cadre directeur de valeurs fondamentales pour résoudre des dilemmes moraux ou pour justifier des règles de comportement plus précises. L'auteur soutient que sur le plan conceptuel, cette approche comporte des lacunes à plusieurs niveaux. Ses partisans ne semblent pas trop savoir ce qu'est une valeur ni comment dégager les valeurs fondamentales. Le fait qu'un grand nombre de valeurs fondamentales ne soient pas clairement définies ne semble pas non plus les déranger. On se trouve inévitablement en face d'une situation de conflits de valeurs sans moyens de les résoudre. Enfin, cette approche fondée sur les valeurs, tout au nioins telle que structurée par Ottawa, les subdivise en groupes, faisant Line étrange distinction entre les valeurs éthiques et non-éthiques. Apres avoir examiné ces lacunes, I'article explore la nécessité de s'intéresser davantage aux approches conséquentialistes pour valoriser le comportement éthique, qui font écho aux façons dont les fonctionnaires abordent d'instinct les jugements moraux. [source] A tale of two dead ends: origin of a potential new gene and a potential new transposable elementMOLECULAR MICROBIOLOGY, Issue 6 2007A. John Clutterbuck Summary An article in this issue of Molecular Microbiology by Cultrone et al. describes how a non-autonomous helitron element could arise from its autonomous parent transposon by deletion followed by readthrough into an adjacent gene and its promoter, thus providing a mechanism for distribution of a specifically regulated promoter sequence around the genome, where it would have the potential to evolve new functions. [source] Bootstrapping Cognition from Behavior,A Computerized Thought ExperimentCOGNITIVE SCIENCE - A MULTIDISCIPLINARY JOURNAL, Issue 3 2008Ralf Möller Abstract We show that simple perceptual competences can emerge from an internal simulation of action effects and are thus grounded in behavior. A simulated agent learns to distinguish between dead ends and corridors without the necessity to represent these concepts in the sensory domain. Initially, the agent is only endowed with a simple value system and the means to extract low-level features from an image. In the interaction with the environment, it acquires a visuo-tactile forward model that allows the agent to predict how the visual input is changing under its movements, and whether movements will lead to a collision. From short-term predictions based on the forward model, the agent learns an inverse model. The inverse model in turn produces suggestions about which actions should be simulated in long-term predictions, and long-term predictions eventually give rise to the perceptual ability. [source] SOCIALITY IN THERIDIID SPIDERS: REPEATED ORIGINS OF AN EVOLUTIONARY DEAD ENDEVOLUTION, Issue 11 2006Ingi Agnarsson Abstract Evolutionary ,dead ends' result from traits that are selectively advantageous in the short term but ultimately result in lowered diversification rates of lineages. In spiders, 23 species scattered across eight families share a social system in which individuals live in colonies and cooperate in nest maintenance, prey capture, and brood care. Most of these species are inbred and have highly female-biased sex ratios. Here we show that in Theridiidae this social system originated eight to nine times independently among 11 to 12 species for a remarkable 18 to 19 origins across spiders. In Theridiidae, the origins cluster significantly in one clade marked by a possible preadaptation: extended maternal care. In most derivations, sociality is limited to isolated species: social species are sister to social species only thrice. To examine whether sociality in spiders represents an evolutionary dead end, we develop a test that compares the observed phylogenetic isolation of social species to the simulated evolution of social and non-social clades under equal diversification rates, and find that sociality in Theridiidae is significantly isolated. Because social clades are not in general smaller than their nonsocial sister clades, the spindly phylogenetic pattern,many tiny replicate social clades,may be explained by extinction rapid enough that a nonsocial sister group does not have time to diversify while the social lineage remains extant. In this case, this repeated origin and extinction of sociality suggests a conflict between the short-term benefits and long-term costs of inbred sociality. Although benefits of group living may initially outweigh costs of inbreeding (hence the replicate origins), in the long run the subdivision of the populations in relatively small and highly inbred colony lineages may result in higher extinction, thus an evolutionary dead end. [source] Are Oxazolidinones Really Unproductive, Parasitic Species in Proline Catalysis?HELVETICA CHIMICA ACTA, Issue 3 2007Experiments Pointing to an Alternative View, Thoughts Abstract The N,O-acetal and N,O-ketal derivatives (oxazolidinones) formed from proline, and aldehydes or ketones are well-known today, and they are detectable in reaction mixtures involving proline catalysis, where they have been considered ,parasitic dead ends'. We disclose results of experiments performed in the early 1970's, and we describe more recent findings about the isolation, characterization, and reactions of the oxazolidinone derived from proline and cyclohexanone. This oxazolidinone reacts (THF, room temperature) with the electrophiles , -nitrostyrene and chloral (=trichloroacetaldehyde), to give the Michael and aldol adduct, respectively, after aqueous workup (Scheme,5). The reactions occur even at ,75° when catalyzed with bases such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) or EtN(i-Pr)2 (DIPEA) (10%; Table,1). It is shown by NMR (Figs.,1 and 3) and IR analysis (Figs.,2 and 4) that the primarily detectable product (before hydrolysis) of the reaction with the nitro-olefin is again an oxazolidinone. When dissolved in hydroxylic solvents such as MeOH, ,hexafluoroisopropanol' ((CF3)2CHOH; HFIP), AcOH, CF3COOH, or in LiBr-saturated THF, the ring of the oxazolidinone from cyclohexanone and proline opens up to the corresponding iminium ion (Tables,2,4), and when treated with strong bases such as DBU (in (D8)THF) the enamino-carboxylate derived from proline and cyclohexanone is formed (Scheme,8). Thus, the two hitherto putative participants (iminium ion and enamine) of the catalytic cycle (Scheme,9) have been characterized for the first time. The commonly accepted mechanism of the stereoselective C,C- or C,X-bond-forming step (i.e., A,D) of this cycle is discussed and challenged by thoughts about an alternative model with a pivotal role of oxazolidinones in the regio- and diastereoselective formation of the intermediate enamino acid (by elimination) and in the subsequent reaction with an electrophile (by trans -addition with lactonization; Schemes,11,14). The stereochemical bias between endo - and exo -space of the bicyclo[3.3.0]octane-type oxazolidinone structure (Figs.,5 and 6) is considered to possibly be decisive for the stereochemical course of events. Finally, the remarkable consistency, with which the diastereotopic Re -face of the double bond of pyrrolidino-enamines (derived from proline) is attacked by electrophiles (Schemes,1 and 15), and the likewise consistent reversal to the Si -face with bulky (Aryl)2C-substituents on the pyrrolidine ring (Scheme,16) are discussed by invoking stereoelectronic assistance from the lone pair of pyramidalized enamine N-atoms. [source] | |||||||||||||