1,720,999 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
Investigating the effects of osmotic stress and cellulose biosynthesis inhibition on cell morphology and plasma membrane tension in Arabidopsis thaliana using confocal microscopy and the mechanosensitive Flipper-TR
No full textPlanter trenger et system for å oppfatte og tilpasse seg miljøet rundt, ettersom de ikke kan forflytte seg. Plantecellen er omgitt av en cellevegg som støtter opp planten strukturelt og mekanisk. Mekanismene for celleveggintegritetsvedlikehold gjør det mulig for plantecellen å overvåke celleveggens tilstand under vekst eller stress fra omgivelsene. Stresspersepsjon er derfor en viktig forutsetning for celletilpasning.
Hypotesen som undersøkes i denne oppgaven er at plasmamembranen, eller komponenter forankret i plasmamembranen, er involvert i stresspersepsjon, som involverer forstyrrelser i det fysiske forholdet mellom plasmamembran og celleveggen.
For å studere den synlige effekten av Isoxaben (ISX) og hyperosmotisk stress på Arabidopsis thaliana røtter, spirer som uttrykker SYP121-YFP, som merker plasmamembranen, ble kontroll-, sorbitol-, ISX- eller ISX + sorbitolbehandlet. Spirene var også farget med propidiumjodid for å farge celleveggen og observere celledød.
I overensstemmelse med tidligere studier virker det som om sorbitol demper noe av effekten ISX har på cellene, selv om det ser ut til å være mer celledød hos spirer behandlet med ISX + sorbitol enn spirene som kun er behandlet med ISX. For å undersøke hva som skjer med plasmamembranspenningen i møte med stress ble fluorescens levetid mikroskopi (fluorescence lifetime imaging microscopy – FLIM) brukt til finne levetiden til Flipper-TR i Arabidopsis spirerenes plasmamembranen i epidermisceller. Flipper-TR har tidligere blitt brukt i dyreceller og gjærceller, men ikke i undersøkelser av planter. Forsøksbetingelser ble derfor først etablert før effekten av de tidligere nevnte behandlingene ble undersøkt. Resultatene av undersøkelsene viste at fire timer ISX-behandling gir en kortere fluorescens levetid sammenlignet med spirene som ble kontrollbehandlet. Til forskjell ga sorbitolbehandling en økning i levetid, også når det var i kombinasjon med ISX, som igjen antyder at sorbitol undertrykker effektene av ISX på spirene. Effekten av hyper-og hypo-osmotisk stress viste seg å ha motsatt effekt på fluorescens levetiden enn hva som tidligere har blitt observert i dyre- og gjærceller.Plants, unable to flee from stress or danger due to their immobile existence, need a system to perceive and adapt to the environment. A cell wall surrounds the plant cell, giving structural and mechanical support to the plant. The cell wall integrity maintenance mechanism is enabling the plant cell to monitor the state of the cell wall during growth or environmental stress. Stress perception is therefore a prerequisite of cell adaption. The working hypothesis to be investigated here is that the plasma membrane, or components anchored to the plasma membrane are involved in stress perception, involving plasma membrane – cell wall continuum disruption.
To study visible effects of Isoxaben (ISX) and hyper-osmotic stress on Arabidopsis thaliana roots, seedlings expressing SYP121-YFP, which labels plasma membranes, were mock-, sorbitol-, ISX-, or ISX + sorbitol-treated. In addition, they were stained with propidium iodide to label cell walls and detect cell death. In accordance with other studies, sorbitol seems to hinder some of the effect ISX has on the cells, though there seems to be more cell death in ISX + Sorbitol-treated seedlings than in those treated only with ISX. To investigate what happens to plasma membrane tension in response to stress, fluorescence lifetime imaging microscopy was used to measure the lifetime of Flipper-TR in the epidermal plasma membrane of Arabidopsis seedlings. Flipper-TR has previously been used in mammalian cells and yeast cells but not in plants. Therefore, experimental conditions were first established before the effects of the same treatments as before were determined. ISX-treatments shorten the fluorescent lifetime compared to mock controls after around 4 hours. In contrast sorbitol-treatments increase the lifetime, also when combined with ISX, again implying sorbitol suppress the ISX effects on the seedling. Interestingly, the effect of hyper- and hypo-osmotic stress were found to have the opposite effect on the lifetime than what has been described previously in mammalian and yeast cells
Characterization of the Plant Cell Wall Response to Isoxaben induced Cell Wall Damage
Full text linkCell wall damage (CWD) causes extensive changes in cell wall composition and structure, which seem to be mediated by a cell wall integrity signalling mechanism. Though parallels have been found to the cell wall integrity signalling pathway in yeast, it is clear that a more detailed study in plants is necessary to understand the process in detail. Classical induction of CWD (pathogens, stress, foraging animals) is often local, or overlaps with other response systems and has rarely been studied specifically. Treating Arabidopsis thaliana seedlings with isoxaben (a specific CESA3 and 6 inhibitor) allows the induction of highly specific CWD in growing tissues. Cross-referencing the genes which respond to isoxaben induced CWD with publically available tissue expression data allow identification of genes of interest. Based on this analysis, 108 genes were identified, and KO insertion lines isolated to assign a biological function to the individual candidate gene. 24 of these genes have been characterised both with and without CWD induction in this PhD. Genes of particular interest were picked using a FTIR clustering method. This method identified genes for which the insertions changed the response to isoxaben and genes which have a different cell wall composition from the outset. Modified cell wall composition of mutants was confirmed using chemical assays and lignin staining for the 10 selected genes. Of these, 6 genes had substantial mutant phenotypes. Saccharification assay showed high sugar yields for more than 50% of the candidates, in seedlings and stems. The specific cell wall features which lead to this improvement in saccharification have yet to be established
Analysis of the signalling mechanisms involved in Cell Wall Integrity maintenance in A.thaliana
Full text linkThe plant cell wall is a dynamic structure that has an integral role during plant development and responses to biotic and abiotic stresses. A cell wall integrity (CWI) maintenance mechanism in plants has been inferred. The aim of this study was to investigate the signalling mechanism that regulates the response of Arabidopsis thaliana to CWI impairment.
Here I show that JA and SA levels increase after 3 and 5 hours (respectively) of CWI impairment. In order to determine the downstream functions of the different signalling mechanisms and their cross-talk upon CWI impairment; lignin deposition, JA & SA induction and root growth inhibition (RGI) phenotypes were used as downstream readouts. My results show that ROS are required for lignin deposition whereas JA & SA-based mechanisms are required to inhibit lignin deposition. ROS and JA act antagonistically to regulate downstream lignin deposition. In addition, a bi-phasic ROS-based signal is induced after CWI impairment, with the initial signal required for JA induction and the later signal required for inhibition of JA induction. H2O2 increased at the plasma membrane in the elongation zone of the root during CWI impairment, as determined by the genetically encoded probe HyPer.
The functions of several RLKs in CWI maintenance were investigated. These included BAK1 and BIK1. Most of the mutant RLKs investigated affected one or two of the downstream readouts, highlighting the complexity of CWI signalling and demonstrating the involvement of elements of the innate immunity signalling. However, THE1 and XII7, mutant seedlings display altered responsiveness to all CWI impairment downstream readouts. These results suggest that these two RLKs represent key regulators of CWI maintenance.
To summarise, the research piresented here has provided novel insights into the signalling mechanisms mediating the response to CWI impairment; has clarified the involvement of several RLKs whose functions had not been defined before and has shown that THE1 and XII7 are key regulators required for mediating all responses to CWI impairment.Open Acces
Investigating the effects of osmotic stress and cellulose biosynthesis inhibition on cell morphology and plasma membrane tension in Arabidopsis thaliana using confocal microscopy and the mechanosensitive Flipper-TR
No full textPlanter trenger et system for å oppfatte og tilpasse seg miljøet rundt, ettersom de ikke kan forflytte seg. Plantecellen er omgitt av en cellevegg som støtter opp planten strukturelt og mekanisk. Mekanismene for celleveggintegritetsvedlikehold gjør det mulig for plantecellen å overvåke celleveggens tilstand under vekst eller stress fra omgivelsene. Stresspersepsjon er derfor en viktig forutsetning for celletilpasning.
Hypotesen som undersøkes i denne oppgaven er at plasmamembranen, eller komponenter forankret i plasmamembranen, er involvert i stresspersepsjon, som involverer forstyrrelser i det fysiske forholdet mellom plasmamembran og celleveggen.
For å studere den synlige effekten av Isoxaben (ISX) og hyperosmotisk stress på Arabidopsis thaliana røtter, spirer som uttrykker SYP121-YFP, som merker plasmamembranen, ble kontroll-, sorbitol-, ISX- eller ISX + sorbitolbehandlet. Spirene var også farget med propidiumjodid for å farge celleveggen og observere celledød.
I overensstemmelse med tidligere studier virker det som om sorbitol demper noe av effekten ISX har på cellene, selv om det ser ut til å være mer celledød hos spirer behandlet med ISX + sorbitol enn spirene som kun er behandlet med ISX. For å undersøke hva som skjer med plasmamembranspenningen i møte med stress ble fluorescens levetid mikroskopi (fluorescence lifetime imaging microscopy – FLIM) brukt til finne levetiden til Flipper-TR i Arabidopsis spirerenes plasmamembranen i epidermisceller. Flipper-TR har tidligere blitt brukt i dyreceller og gjærceller, men ikke i undersøkelser av planter. Forsøksbetingelser ble derfor først etablert før effekten av de tidligere nevnte behandlingene ble undersøkt. Resultatene av undersøkelsene viste at fire timer ISX-behandling gir en kortere fluorescens levetid sammenlignet med spirene som ble kontrollbehandlet. Til forskjell ga sorbitolbehandling en økning i levetid, også når det var i kombinasjon med ISX, som igjen antyder at sorbitol undertrykker effektene av ISX på spirene. Effekten av hyper-og hypo-osmotisk stress viste seg å ha motsatt effekt på fluorescens levetiden enn hva som tidligere har blitt observert i dyre- og gjærceller
Arabidopsis thaliana THESEUS1 modulates phytohormone responses induced by plant cell wall damage
No full textPlantecelleveggen er den definerende strukturen til landplanter som tillot dem å nå sine til tider imponerende størrelser, men vår forståelse av prosessene som opprettholder celleveggintegritet (CWI) er ekstremt begrenset. Arabidopsis thaliana Catharanthus roseus reseptorlignende kinase (CrRLK) THESEUS1 (THE1) er et celleveggs integritetsfølende PM-lokalisert protein. THE1-aktiviteten er avhengig av tilgjengeligheten av peptidet Rapid Alkalinization Factor 34 (RALF34). THE1 antas å samhandle med en annen nært beslektet CrRLK FERONIA (FER). FER har vist seg å samhandle med fytohormonene Jasmonic acid (JA) og abscisic acid (ABA) som respons på celleveggskade (CWD), men om og hvordan THE1 interagerer med fytohormoner er ennå ikke helt forstått. THE1-mutantene, the1-1 og the1-4, ble krysset med hormonreporter JAZ10:: YFP for JA, pRAB18 :: GFP-GUS for ABA, og DR5 :: 3xVENUS for auxin. Disse THE1 mutant-hormon reporter kryssene ble behandlet med isoxaben (ISX) for å etterligne redusert CWI og sorbitol for å indusere osmotisk stress. Disse behandlingene ble avbildet ved 0, 2, 4, 6 og 8 timer tidspunkter, og disse dataene ble brukt til å beregne prosent arealdekning. Flere forskjeller ble notert mellom villtype THE1 og THE1 mutanter; JAZ10 respons på CWD ble vist å avta under the1-1 mutanten, men ikke vist å øke under the1-4 mutanten. Plasseringen av pRAB18-signalering i Col-0 var forskjellig fra the1-1 og the1-4. Et økt DR5-signal i stele-initialer, hvilesenter (QC), cortex / endodermal initial, columella initial og columella-celler ble notert i THE1-mutantene, men ikke i vill type THE1. Disse resultatene antyder at THE1 er direkte koblet til JA og mulige ABA-svar på celleveggskader. Det antyder også at THE1 ikke er direkte koblet til auxinsvarene på celleveggskader, og at dette er forårsaket av endringer i apoplastisk pH forårsaket av endrede RALF34 THE1-interaksjoner
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
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