1,720,983 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Can we accurately predict the distribution of soil microorganism presence and relative abundance?
Full text linkpeer reviewedSoil microbes play a key role in shaping terrestrial ecosystems. It is therefore essential to understand what drives their distribution. While multivariate analyses have been used to characterise microbial communities and drivers of their spatial patterns, few studies have focused on predicting the distribution of amplicon sequence variants (ASVs). Here, we evaluate the potential of species distribution models (SDMs) to predict the presence–absence and relative abundance distribution of bacteria, archaea, fungi, and protist ASVs in the western Swiss Alps. Advanced automated selection of abiotic covariates was used to circumvent the lack of knowledge on the ecology of each ASV. Presence–absence SDMs could be fitted for most ASVs, yielding better predictions than null models. Relative abundance SDMs performed less well, with low fit and predictive power overall, but displayed a good capacity to differentiate between sites with high and low relative abundance of the modelled ASV. SDMs for bacteria and archaea displayed better predictive power than for fungi and protists, suggesting a closer link of the former with the abiotic covariates used. Microorganism distributions were mostly related to edaphic covariates. In particular, pH was the most selected covariate across models. The study shows the potential of using SDM frameworks to predict the distribution of ASVs obtained from topsoil DNA. It also highlights the need for further development of precise edaphic mapping and scenario modelling to enhances prediction of microorganism distributions in the future
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
Bioottisten interaktioiden merkitys ympäristögradienteilla : Esimerkkinä variksenmarjan vaikutus arktis-alpiinisessa kasvillisuudessa
No full textPlant-plant interactions, i.e. biotic interactions, shape plant communities and the vegetation's succession along abiotic environmental factors. Positive interactions (e.g. facilitation) may expand species niches and enhance growth and reproduction. Negative interactions (e.g. competition, allelopathy) can interfere with growth and reproduction, even out competing some species from their niches. Negative and positive interactions co-occur, but research has shown that positive interactions are generally more common and important than negative ones in harsh environments. The theory of change of net-interaction from negative to positive along an environmental gradient is called the stress gradient hypothesis (=SGH). This work examines nordic crowberry's (Empetrum nigrum ssp. hermaphroditum) effect on arctic-alpine species' sexual reproduction under different environmental stress levels. Crowberry is a dominant species in low-nutrient, acidic arctic-alpine ecosystems. Its competitive ability is based on allelopathic characteristics and a forming of dense mats. It is also unpalatable for herbivores. The species facilitative characteristics include providing shelter from the wind and maintaining an ericoidmycorrhiza community. In this research environmental stress is represented by geomorphological disturbance and soil moisture, with the interactions between crowberry and other species are examined as the relationship between crowberry cover and the fitness measures (e.g. abundance of flowers or fruits) of study species. Explanation for the variation in the effects of crowberry is tried to find from the traits of the study species.
Data was collected in May 2011 from Kilpisjärvi, northernmost Finland. The study area comprised 960 1m2 cells. In each cell the cover of each species (including crowberry), the abundance of each species flowers or fruits, the cover of geomorfological disturbance and soil moisture were recorded. Generalized linear models (=GLM) were run for all species to identify the best model for predicting fitness (as selected by the AIC-criterion). Spatial autocorrelation was accounted for by repeating analyses using generalized estimation equation models (GEE), which explicitly account for the spatial structure of data. 17 species were included to the research based on the abundance of their flowers and berries in the research area.
Crowberry is included in the best fit model for 14 out of 17 species. The effect of crowberry was positive for four species and negative for ten species based on the modeling results. Interactions of the crowberry and one of the environmental variables are included to the models 19 times. In ten of these cases the interactions agreed with the predictions of the SGH (i.e. effect of crowberry became less negative with increasing abiotic stress). No species traits were consistently related to the outcome of interaction between crowberry and environmental variable, although crowberry effects on dwarf shrub species appeared to be more commonly positive than on other growthforms.
According to these results, crowberry has dominant role in arctic-alpine plant communities. The species effect on sexual reproduction of other plant species is commonly negative, but the effect can change to positive along environmental stress gradients, supporting the SGH. Dwarf shrubs may interact positively with crowberry because of sharing the same mycorrhiza type, while more generally species may benefit from crowberry due to its provisioning of shelter from the wind and increased soil moisture. The negative effect of crowberry might be related to its production of allelopathic compounds or its dense growth. The reason for crowberry having a facilitative affect under disturbed conditions might be an indirect effect of disturbance decreasing crowberry's allelopathic effects. These results show that the roles of crowberry and biotic interactions in arctic-alpine vegetation are important. Therefore understanding their effects and mechanisms is important in predicting how this vegetation will respond to changing climate.Kasvien väliset vuorovaikutukset eli bioottiset interaktiot muokkaavat ympäristötekijöiden ohella tietylle alueelle kehittyvää kasvillisuutta. Positiiviset interaktiot (mm. fasilitaatio) laajentavat lajien levinneisyyksiä ja edesauttavat lajien kasvua ja lisääntymistä. Negatiiviset interaktiot (mm. kilpailu ja allelopatia) taas häiritsevät muiden lajien kasvua ja lisääntymistä ja jopa häätävät lajeja niiden esiintymisalueilta. Negatiiviset ja positiiviset interaktiot vaikuttavat lajien välillä samanaikaisesti, mutta tutkimuksissa on havaittu korkean ympäristöstressin alueilla positiivisten vuorovaikutuksen olevan negatiivisia voimakkaampia. Teoriaa kasvien välisen nettointeraktion suunnan muuttumisesta negatiivisesta positiiviseksi ympäristögradientilla kutsutaan stressigradienttihypoteesiksi (=SGH).Tässä työssä tarkastellaan pohjanvariksenmarjan (Empetrum nigrum ssp. hermaphroditum) vaikutusta muiden lajien lisääntymiskelpoisuudelle ympäristöstressin vaihdellessa. Variksenmarja on heikkoravinteisten ja happamien alueiden dominoivampia lajeja arktis-alpiinisissa ympäristöissä. Sen kilpailukyky perustuu sen allelopatisiin ominaisuuksiin, mattomaiseen kasvutapaan ja kelpaamattomuuteen kasvinsyöjien ravinnoksi. Sen fasilitoivia ominaisuuksia ovat mm. hyvä tuulensietokyky ja erikoidmykorritsayhdyskunnan ylläpito. Tutkimuksessa ympäristöstressiä edustavat geomorfologinen häiriö ja maaperän kosteus. Variksenmarjan ja lajien vuorovaikutusta tarkastellaan variksenmarjan peiton ja lajien lisääntymiskelpoisuuden välillä. Variksenmarjan vaikutuksen ja vaikutuksen suunnan muuttumisen lisäksi tarkastellaan lajien piirteitä mahdollisina interaktion suunnan selittäjinä.
Aineisto kerättiin heinäkuussa 2011 Kilpisjärveltä, Luoteis-Lapista. Aineisto koostuu 960 neliömetrin ruudusta, joista on laskettu kukkivien tai marjovien lajien kukat ja marjat, arvioitu variksenmarjan ja muiden lajien peitto ja geomorfologisen häiriön osuus sekä mitattu maaperän kosteus. Variksenmarjan vaikutuksen selvittämiseksi aineistoa analysoitiin tilastollisin menetelmin, ensisijaisesti käyttäen yleistettyjä lineaarisia malleja (GLM). Mallit ajettiin kaikille lajeille kaikilla mahdollisilla muuttujakombinaatioilla sallien toisen asteen interaktiot. Kunkin lajin kelpoisuutta parhaiten mallintava malli valittiin AIC-mallinvalintamenettelyllä. Spatiaalisen autokorrelaation mahdollisuus huomioitiin vertaamalla tuloksia GEE- (Generalised estimation equations) menetelmällä saatuihin vastaaviin tuloksiin. GEE:ssä on mahdollisuus huomioida aineiston spatiaalinen rakenne. Mallinnettavia lajeja oli 17. Lajit valittiin niiden kukkimisen ja marjomisen yleisyyden perusteella.
Variksenmarja on mukana 14 lajin parhaassa mallissa 17:stä lajista. Variksenmarjan vaikutus on mallinnustulosten perusteella positiivinen neljälle lajille ja negatiivinen kymmenelle. Variksenmarjan ja toisen ympäristömuuttujan interaktio on mukana 19 kertaa. Kymmenessä tapauksessa interaktion suunnan muuttuminen ympäristögradientilla tukee stressigradienttihypoteesia. Lajien piirteistä ei löytynyt yksiselitteistä selitystä interaktion suunnalle, mutta tulosten perusteella variksenmarja vaikuttaa positiivisesti yleisimmin muihin varpukasveihin.
Tulosten perusteella variksenmarjalla on varsin dominoiva rooli arktis-alpiinisessa ympäristössä. Se vaikuttaa lajien kelpoisuuteen yleisesti negatiivisesti, mutta vaikutus muuttuu usein positiiviseksi lajin ankaraksi kokemassa ympäristössä tukien SGH:a. Variksenmarjan negatiivinen vaikutus liittyy luultavasti allelopatisiin ominaisuuksiin ja mattomaiseen kasvutapaan. Fasilitointi taas erikoidmykorritsayhdyskunnan ylläpitoon, tuulen suojan tarjoamiseen ja maaperän kosteuttamiseen, sekä välillisesti allelopatisten mekanismien heikentymiseen geomorfologisen häiriön ollessa suurta. Varpukasvien positiiviseen ragointiin voi olla syynä samanlainen kasvumuoto tai symbioosin muodostaminen saman mykorritsatyypin kanssa. Tulokset osoittavat, että bioottisten interaktioiden merkitys arktis-alpiinisessa kasvillisuudessa ovat tärkeitä. Niiden vaikutusten ja mekanismien tunteminen on tärkeää muuttuvassa ilmastossa
Biotic interactions in driving biodiversity : Insights into spatial modelling
No full textThe effects of co-occurring species, namely biotic interactions, govern performance and assemblages of species along with abiotic factors. They can emerge as positive or negative, with the outcome and magnitude of their impact depending on species and environmental conditions. However, no general conception of the role of biotic interactions in functioning of ecosystems exists. Implementing correlative spatial modelling approaches, combined with extensive data on species and environmental factors, would complement the understanding of biotic interactions and biodiversity. Moreover, the modelling frameworks themselves, conventionally based on abiotic predictors only, could benefit from incorporating biotic interactions and their context-dependency.
In this thesis, I study the influence of biotic interactions in ecosystems and examine whether their effects vary among species and environmental gradients (sensu stress gradient hypothesis = SGH), and consequently, across landscapes. Species traits are hypothesized to govern the species-specific outcomes, while the SGH postulates that the frequency of positive interactions is higher under harsh environmental conditions, whereas negative interactions dominate at benign and productive sites. The study applies correlative spatial models utilizing both regression models and machine-learning methods, and fine-scale (1 m2) data on vascular plant, bryophyte and lichen communities from Northern Finland and Norway (69°N, 21°E). In addition to conventional distribution models of individual species (SDM), also species richness, traits and fitness are modelled to capture the community-level impacts of biotic interactions. The underlying methodology is to incorporate biotic predictors into the abiotic-only models and to examine the impacts of biotic interactions and their dependency on species traits and environmental conditions. Cover values of the dominant species of the study area are used as proxies for the intensity of their impact on other species.
The results show, firstly, that plant plant interactions consistently and significantly affect species performance and richness patterns. Secondly, the results make evident that the impacts of biotic interactions vary between species, and, more importantly, that the guild, geographic range and traits of species can indicate the outcome and magnitude of the impact. For instance, vascular plant species, particularly competitive ones, respond mainly negatively to the dominant species, whereas lichens tend to show more positive responses. Thirdly, as proposed, the manifestation of biotic interactions also varies across environmental gradients. Support for the SGH is found as the effect of the dominant species is more negative under ameliorate conditions for most species and guilds. Finally, simulations of species richness, where the cover of the dominant species is modified, demonstrate that the biotic interactions exhibit a strong control over landscape-level biodiversity patterns. These simulations also show that even a moderate increase in the cover of the dominant species can lead to drastic changes in biodiversity patterns. Overall, all analyses consistently demonstrate that taking into account biotic interactions improves the explanatory power and predicting accuracy of the models.
There are global demands to understand species-environment relationships to enable predictions of biodiversity changes with regard to a warming climate or altered land-use. However, uncertainties in such estimates exist, especially due to the precarious influence of biotic interactions. This thesis complements the understanding of biotic interactions in ecosystems by demonstrating their fundamental, yet species-specific and context-dependent, role in shaping species assemblages and performance across landscapes. From an applied point of view, our study highlights the importance of recognizing biotic interactions in future forecasts of biodiversity patterns.Bioottiset interaktiot (= lajien väliset vuorovaikutukset) vaikuttavat lajien levinneisyyteen abioottisten (mm. lämpötila, vesi) tekijöiden ohella. Bioottisten interaktioiden vaikutus voi olla negatiivinen (esim. lajien välinen kilpailu) tai positiivinen (esim. auringon paahteelta suojaaminen), ja vaikutuksen suunnan ja voimakkuuden on havaittu riippuvan lajeista ja vallitsevista ympäristöoloista. Ymmärrys bioottisten interaktioiden merkityksestä biodiversiteetille on kuitenkin vähäistä, mutta tätä voitaisiin täydentää useita lajeja ja ympäristöoloja yhtäaikaisesti käsittelevillä alueellisilla malleilla. Lisäksi myös alueellisia biodiversiteettiennusteita voitaisiin parantaa huomioimalla bioottiset interaktiot malleissa.
Tämä väitöskirja tutkiikin bioottisten interaktioiden vaikutusta kasvillisuuteen, sekä miten nämä vaikutukset vaihtelevat lajien välillä ja erilaisissa ympäristöoloissa. Tutkimus nojautuu alueelliseen mallintamiseen hyödyntäen kattavia laji- ja ympäristöaineistoja Pohjois-Suomesta ja -Norjasta (69°N, 21°E). Mallinnuksessa käytetään niin yksittäisiä lajilevinneisyysmalleja, kuin myös lajirunsautta ja -rakennetta ja lajien kelpoisuutta tarkastelevia malleja. Mallinnusprosessissa malleihin tuodaan abioottisten tekijöiden lisäksi myös bioottisia muuttujia; tässä työssä valtalajien peittävyysarvot.
Tutkimustulokset osoittavat ensinnäkin, että bioottiset interaktiot vaikuttavat kasvillisuuteen ja sen diversiteettiin. Tutkimuksen ennusteiden perusteella vähäinenkin kasvu tutkimusalueen valtalajin peitossa voi vähentää lajirunsautta merkittävästi. Toiseksi, bioottisten interaktioiden vaikutukset vaihtelevat lajien välillä, mutta vaikutuksen suuntaa ja voimakkuutta voidaan arvioida lajien ominaisuuksien perusteella. Kolmanneksi, bioottisten interaktioiden vaikutuksen suunta ja voimakkuus vaihtelee myös ympäristöolojen suhteen siten, että negatiivisimmat interaktiot vallitsevat suotuisissa ympäristöoloissa (ts. tuottoisat ympäristöt), kun positiivisia vuorovaikutuksia ilmenee taas karuissa ympäristöissä (esim. kylmät ja kuivat alueet). Viimeiseksi, bioottiset interaktiot vaikuttavat kasvillisuuteen koko maisematasolla ja niiden huomiotta jättäminen heikentää siten alueellisia biodiversiteettimalleja.
Ilmastonmuutos ja maankäytön muuttuminen uhkaavat ekosysteemejä, mikä asettaa tarpeen tarkoille ja realistisille ennusteille biodiversiteetin muutoksista tulevaisuudessa. Tämä tutkimus osoittaa, että näitä ennusteita on mahdollista parantaa huomioimalla bioottiset interaktiot malleissa. Lisäksi tämä tutkimus valottaa bioottisten interaktioiden merkitystä kasvillisuudelle, etenkin herkillä pohjoisilla tundra-alueilla.ei saavutettav
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
