1,720,985 research outputs found
Digit identity and digit number: indirect support for the descent of birds from theropod dinosaurs /
Get PDFDivergence and convergence in early embryonic stages of metazoans
No full textThe early stages of organogenesis in metazoans differ drastically between higher order taxa such as phyla and classes. The segmented germ band stage in insects, the nauplius stage of crustaceans, and the neurula/pharyngula stage in vertebrates are examples of this diversification. In striking contrast with this divergence, is the similarity of these stages within these taxa, i.e., within insects, crustaceans, and vertebrates. The early stages of organogenesis, or phylotypic stages, have, thus, remained very similar in most species since the evolutionary origin of the taxa. These phylotypic stages are considerably more similar to each other than to the earlier stages of cleavage and gastrulation. Cleavage and gastrulation stages display not only great variability, but also striking examples of apparent convergence among species in different phyla, for example in the many cases of epiblastic cleavage in yolk-rich eggs. This leads to the paradoxical situation that the overall similarity of cleavage and gastrulation stages is in general higher among metazoans than of the early stages of organogenesis, but within phyla and classes the situation is the reverse. We discuss data on cleavage, gastrulation, and early organogenesis and evaluate possible causes for conservation, homoplasy, and diversification in an attempt to throw light on this paradoxical situation. In addition, we discuss a hypothesis that has been proposed to explain the diversity of early stages of organogenesis at the level of metazoans and the similarity within many phyla and classes
Divergence and convergence in early embryonic stages of metazoans
No full textThe early stages of organogenesis in metazoans differ drastically between higher order taxa such as phyla and classes. The segmented germ band stage in insects, the nauplius stage of crustaceans, and the neurula/pharyngula stage in vertebrates are examples of this diversification. In striking contrast with this divergence, is the similarity of these stages within these taxa, i.e., within insects, crustaceans, and vertebrates. The early stages of organogenesis, or phylotypic stages, have, thus, remained very similar in most species since the evolutionary origin of the taxa. These phylotypic stages are considerably more similar to each other than to the earlier stages of cleavage and gastrulation. Cleavage and gastrulation stages display not only great variability, but also striking examples of apparent convergence among species in different phyla, for example in the many cases of epiblastic cleavage in yolk-rich eggs. This leads to the paradoxical situation that the overall similarity of cleavage and gastrulation stages is in general higher among meta
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Pienten eristyneiden susipopulaatioiden (<em>Canis lupus</em>) luupatologia
No full textAbstractMany populations of large carnivores are fragmented today and are therefore vulnerable to the harmful effects of inbreeding. Population health is central for the conservation and management of isolated populations. However, in wild populations inbreeding and health effects are usually difficult to assess. Two well-known cases of conservation concern are the inbred wolf (Canis lupus) populations from Scandinavia and Isle Royale, USA that have been more or less isolated for decades. The aim of this study was to analyze the frequency and morphology of vertebral malformations (i.e. anomalies) in these populations including two reference populations. Dental anomalies were also examined in wolves from Scandinavia including a review of reported soft tissue anomalies. In the separate studies I–III, we investigate a total of 324 wolves including 174 individuals from the contemporary Scandinavian population and 36 from Isle Royale. The reference populations included 84 wolves from the Finnish population and 30 wolves from the extinct historical Scandinavian population. The frequency of vertebral malformations in wolves from Isle Royale increased over time. The same pattern was evident in Scandinavian wolves when multiple types of anomalies were considered. The most common type of vertebral anomaly in the inbred populations was lumbosacral transitional vertebrae, LSTV, which is considered hereditary and clinically significant in dogs (Canis familiaris). Population comparisons showed that the incidence of this anomaly seemed to be associated with the extent of inbreeding in the populations. Paper ll in this thesis is the first study that indicates how genetic deterioration has compromised the morphology of Isle Royale wolves. This has a very important conservation implication since this population has been a famous example that policy makers have used to support arguments that small populations can avoid genetic deterioration. The results of this thesis have implication for understanding population health in small populations and are an important aspect for population health monitoring that can be used for the detection of population deterioration.Original papersOriginal papers are not included in the electronic version of the dissertation.Räikkönen, J., Bignert, A., Mortensen, P., & Fernholm, B. (2006). Congenital defects in a highly inbred wild wolf population (Canis lupus). Mammalian Biology, 71(2), 65–73. https://doi.org/10.1016/j.mambio.2005.12.002Räikkönen, J., Vucetich, J. A., Peterson, R. O., & Nelson, M. P. (2009). Congenital bone deformities and the inbred wolves (Canis lupus) of Isle Royale. Biological Conservation, 142(5), 1025–1031. https://doi.org/10.1016/j.biocon.2009.01.014Räikkönen, J., Vucetich, J. A., Vucetich, L. M., Peterson, R. O., & Nelson, M. P. (2013). What the Inbred Scandinavian Wolf Population Tells Us about the Nature of Conservation. PLoS ONE, 8(6), e67218. https://doi.org/10.1371/journal.pone.0067218Self-archived versionTiivistelmäNykyään monien suurpetojen populaatiot ovat pirstoutuneita ja siksi ne ovat alttiita sukusiitoksen haitallisille vaikutuksille. Populaation terveys on keskeistä eristyneiden populaatioiden suojelussa ja hoidossa. Sukusiitoksen haitallisia vaikutuksia luonnonvaraisissa populaatioissa on yleensä vaikea arvioida. Skandinavian ja Yhdysvaltojen Isle Royalen saaren vuosikymmeniä eristyneinä olleet sukusiittoiset susipopulaatiot (Canis lupus), ovat luonnonsuojelun esimerkkitapauksia. Tämän väitöskirjatutkimuksen tavoitteena oli analysoida näiden populaatioiden luupatologiaa suhteessa kahteen vertailupopulaatioon. Tämän lisäksi tutkittiin myös Skandinavian susipopulaation hampaiden epämuodostumia ja esitettiin yhteenveto aikaisemmissa tutkimuksissa raportoiduista pehmytkudoksen poikkeavuuksista. Väitoskirjan kolmessa erillisessä julkaisussa tutkittiin yhteensä 324 sutta sukusiittoisista populaatioista; 174 yksilöä nykyisestä Skandinavian ja 36 Isle Royalen populaatiosta. Vertailupopulaatioihin kuului 84 suomalaista sutta sekä 30 sutta sukupuuttoon kuolleesta historiallisesta Skandinavian populaatiosta. Isle Royalen susien selkärangan epämuodostumien esiintymistiheys kasvoi ajan myötä. Sama ilmiö näkyi myös skandinaavisissa susissa tarkasteltaessa useita epämuodostumatyyppejä. Yleisin tyyppi selkärangan poikkeavuuksista sisäsiittoisissa populaatioissa olivat välimuotoiset lanneristinikamat (LSTV), jota pidetään perinnöllisenä ja kliinisesti merkittävänä ominaisuutena koirilla (Canis familiaris). Populaatiovertailut osoittivat, että tämän poikkeavuuden esiintyminen liittyi populaation sukusiitoksen laajuuteen. Artikkeli II on ensimmäinen tutkimus, jossa on osoitettu, geneettisen heikentymisen olleen haitallista Isle Royalen susien morfologialle. Tämä on erittäin tärkeä havainto luonnonsuojelun kannalta. Tämä populaatio on ollut kuuluisa ja monien päätöksentekijöiden käyttämä esimerkki väitteille, joiden mukaan pienet populaatiot voivat välttää geneettistä kurjistumista. Tämän tutkimuksen tuloksilla on merkitystä pienten populaatioiden terveyden ymmärtämiselle, ja käytetyt menetelmät osoittautuivat hyödyllisiksi populaatioiden terveydentilan seurannassa.OsajulkaisutOsajulkaisut eivät sisälly väitöskirjan elektroniseen versioon.Räikkönen, J., Bignert, A., Mortensen, P., & Fernholm, B. (2006). Congenital defects in a highly inbred wild wolf population (Canis lupus). Mammalian Biology, 71(2), 65–73. https://doi.org/10.1016/j.mambio.2005.12.002Räikkönen, J., Vucetich, J. A., Peterson, R. O., & Nelson, M. P. (2009). Congenital bone deformities and the inbred wolves (Canis lupus) of Isle Royale. Biological Conservation, 142(5), 1025–1031. https://doi.org/10.1016/j.biocon.2009.01.014Räikkönen, J., Vucetich, J. A., Vucetich, L. M., Peterson, R. O., & Nelson, M. P. (2013). What the Inbred Scandinavian Wolf Population Tells Us about the Nature of Conservation. PLoS ONE, 8(6), e67218. https://doi.org/10.1371/journal.pone.0067218Rinnakkaistallennettu versioAcademic dissertation to be presented with the assent of the Doctoral Training Committee of Technology and Natural Sciences of the University of Oulu for public defence on 26 March 2021, at 17 p.m.Abstract
Many populations of large carnivores are fragmented today and are therefore vulnerable to the harmful effects of inbreeding. Population health is central for the conservation and management of isolated populations. However, in wild populations inbreeding and health effects are usually difficult to assess. Two well-known cases of conservation concern are the inbred wolf (Canis lupus) populations from Scandinavia and Isle Royale, USA that have been more or less isolated for decades. The aim of this study was to analyze the frequency and morphology of vertebral malformations (i.e. anomalies) in these populations including two reference populations. Dental anomalies were also examined in wolves from Scandinavia including a review of reported soft tissue anomalies. In the separate studies I–III, we investigate a total of 324 wolves including 174 individuals from the contemporary Scandinavian population and 36 from Isle Royale. The reference populations included 84 wolves from the Finnish population and 30 wolves from the extinct historical Scandinavian population. The frequency of vertebral malformations in wolves from Isle Royale increased over time. The same pattern was evident in Scandinavian wolves when multiple types of anomalies were considered. The most common type of vertebral anomaly in the inbred populations was lumbosacral transitional vertebrae, LSTV, which is considered hereditary and clinically significant in dogs (Canis familiaris). Population comparisons showed that the incidence of this anomaly seemed to be associated with the extent of inbreeding in the populations. Paper ll in this thesis is the first study that indicates how genetic deterioration has compromised the morphology of Isle Royale wolves. This has a very important conservation implication since this population has been a famous example that policy makers have used to support arguments that small populations can avoid genetic deterioration. The results of this thesis have implication for understanding population health in small populations and are an important aspect for population health monitoring that can be used for the detection of population deterioration.Tiivistelmä
Nykyään monien suurpetojen populaatiot ovat pirstoutuneita ja siksi ne ovat alttiita sukusiitoksen haitallisille vaikutuksille. Populaation terveys on keskeistä eristyneiden populaatioiden suojelussa ja hoidossa. Sukusiitoksen haitallisia vaikutuksia luonnonvaraisissa populaatioissa on yleensä vaikea arvioida. Skandinavian ja Yhdysvaltojen Isle Royalen saaren vuosikymmeniä eristyneinä olleet sukusiittoiset susipopulaatiot (Canis lupus), ovat luonnonsuojelun esimerkkitapauksia. Tämän väitöskirjatutkimuksen tavoitteena oli analysoida näiden populaatioiden luupatologiaa suhteessa kahteen vertailupopulaatioon. Tämän lisäksi tutkittiin myös Skandinavian susipopulaation hampaiden epämuodostumia ja esitettiin yhteenveto aikaisemmissa tutkimuksissa raportoiduista pehmytkudoksen poikkeavuuksista. Väitoskirjan kolmessa erillisessä julkaisussa tutkittiin yhteensä 324 sutta sukusiittoisista populaatioista; 174 yksilöä nykyisestä Skandinavian ja 36 Isle Royalen populaatiosta. Vertailupopulaatioihin kuului 84 suomalaista sutta sekä 30 sutta sukupuuttoon kuolleesta historiallisesta Skandinavian populaatiosta. Isle Royalen susien selkärangan epämuodostumien esiintymistiheys kasvoi ajan myötä. Sama ilmiö näkyi myös skandinaavisissa susissa tarkasteltaessa useita epämuodostumatyyppejä. Yleisin tyyppi selkärangan poikkeavuuksista sisäsiittoisissa populaatioissa olivat välimuotoiset lanneristinikamat (LSTV), jota pidetään perinnöllisenä ja kliinisesti merkittävänä ominaisuutena koirilla (Canis familiaris). Populaatiovertailut osoittivat, että tämän poikkeavuuden esiintyminen liittyi populaation sukusiitoksen laajuuteen. Artikkeli II on ensimmäinen tutkimus, jossa on osoitettu, geneettisen heikentymisen olleen haitallista Isle Royalen susien morfologialle. Tämä on erittäin tärkeä havainto luonnonsuojelun kannalta. Tämä populaatio on ollut kuuluisa ja monien päätöksentekijöiden käyttämä esimerkki väitteille, joiden mukaan pienet populaatiot voivat välttää geneettistä kurjistumista. Tämän tutkimuksen tuloksilla on merkitystä pienten populaatioiden terveyden ymmärtämiselle, ja käytetyt menetelmät osoittautuivat hyödyllisiksi populaatioiden terveydentilan seurannassa
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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