1,721,807 research outputs found
A meta-analysis of plant tissue O2 dynamics
Get PDFAdequate tissue O2 supply is crucial for plant function. We aimed to identify the environmental conditions and plant characteristics that affect plant tissue O2 status. We extracted data and performed meta-analysis on >1500 published tissue O2 measurements from 112 species. Tissue O2 status ranged from anoxic conditions in roots to >53 kPa in submerged, photosynthesising shoots. Using information-theoretic model selection, we identified ‘submergence’, ‘light’, ‘tissue type’ as well as ‘light × submergence’ interaction as significant drivers of tissue O2 status. Median O2 status were especially low (<50% of atmospheric equilibrium) in belowground rhizomes, potato (Solanum tuberosum) tubers and root nodules. Mean shoot and root O2 were ~25% higher in light than in dark when shoots had atmospheric contact. However, light showed a significant interaction with submergence on plant O2, with a submergence-induced 44% increase in light, compared with a 42% decline in dark, relative to plants with atmospheric contact. During submergence, ambient water column O2 and shoot tissue O2 correlated stronger in darkness than in light conditions. Although use of miniaturised Clark-type O2 electrodes has enhanced understanding of plant O2 dynamics, application of non-invasive methods in plants is still lacking behind its widespread use in mammalian tissues
A new centre for maritime archaeology in Denmark.
No full textEn 1993, le Conseil national danois de la recherche décide de soutenir le Musée national danois pour la création d'un Centre de recherche d'archéologie maritime à Roskûde. Le nouveau centre a été ouvert en Septembre 1993 afin de prolonger les vingt-cinq années d'activités du Viking Ship Muséum et de l'Institut d'archéologie maritime du Musée national. Quarante millions de couronnes danoises ont été mis à la disposition du Centre pour les travaux de recherche couvrant les années 1993 à 1998.
Les activités du Centre portent sur trois domaines de recherche principaux:
-Aspects maritimes des sociétés anciennes.
-Archéologie navale.
- Outils et techniques.
Le premier thème implique les archéologues traditionnels dans divers projets pour lesquels l'élément maritime est un élément important dans la compréhension des sociétés anciennes, comme par exemple le commerce, la défense côtière, ou encore la symbolique du navire dans les cultes. Au cours des premières années, l'attention s'est portée sur l'âge du Fer et la période médiévale.
Le second thème principal concerne de nouvelles fouilles et une série de publications ayant trait à la découverte de Nydam (âge du Fer), aux navires vikings et aux caboteurs du Haut Moyen Âge provenant des eaux danoises.
Le troisième thème a pour but le lancement de projets relatifs à la préservation des bois humides, à la documentation, aux techniques de recherches sismiques et à certains aspects de l'architecture navale portant sur les navires anciens.
Nous espérons que cette initiative permettra de stimuler la recherche en archéologie maritime, d'une manière générale, pour toute l'Europe du Nord.Crumlin-Pedersen Ole. A new centre for maritime archaeology in Denmark.. In: Archaeonautica, 14, 1998. Construction navale maritime et fluviale. Approches archéologique, historique et ethnologique. pp. 327-332
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
Contrasting oxygen dynamics in Limonium narbonense and Sarcocornia fruticosa during partial and complete submergence
No full textTerrestrial saltmarsh plants inhabitin flood-prone habitats undergo recurrent and prolonged flooding driven by tidal regimes. In this study, the role of internal plant aeration in contrasting hypoxiclanoxic conditions during submergence was investigated in the two halophytes Linionhan narbonense Mill. and Sarcocornia fruticosa (L.) A.J. Scott. Monitoring of tissue O-2, dynamics was performed in shoots and roots using microelectrodes under drained conditions, waterlogging, partial and complete submergence, in light or darkness. For both species, submergence in darkness resulted in significant declines in tissue O-2 status and when in light, in rapid O-2, increases first in shoot tissues and subsequently in roots. During partial submergence, S. fruticosa benefitted from snorkelling and efficiently transported O-2 to roots, whereas the O-2 concentration in roots of L. narbonense declined by more than 90%, Significantly thinner leaves and articles were recorded under high degree of flooding stress and both species showed considerably high tissue porosity. The presence of aerenchyma seemed to support internal aeration in S. fruticosa whereas O-2 diffusion in L. narbonense seemed impeded, despite the higher porosity (up to 50%). Thus, the results obtained for L. narbonense, being well adapted to flooding, suggests that processes other than internal aeration could be involved in better flooding tolerance e.g. fermentative processes, and that traits resulting in flooding tolerance in plants are not yet fully understoo
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
Root acclimations to soil flooding prime rice (<i>Oryza sativa L.</i>) for subsequent conditions of water deficit
Get PDFBackground and aimsThe root barrier to radial O2 loss is a trait induced during soil flooding restricting oxygen loss from the roots to the anoxic soil. It can also restrict radial water loss, potentially providing tolerance towards drought during conditions of water deficit. Several root traits (aerenchyma and xylem vessels area) respond in a similar way to soil flooding and low soil water potentials. Therefore, we hypothesised that root acclimations to soil flooding prime plants to withstand conditions of water deficit.MethodsWe raised plants in hydroponics mimicking contrasting soil water conditions (aerated controls for well-watered soils; stagnant, deoxygenated solutions for flooded soils, and aerated solutions with different PEG6000 concentrations to mimic conditions of water deficit). We used O2 microsensors and gravimetric measurements to characterize the formation of a barrier to radial O2 loss during conditions of water deficit, and measured key anatomical root traits using light microscopy.ResultsSeveral root traits were induced in stagnant conditions as well as in conditions of water deficit, including the barrier to radial O2 loss. The tightness of the barrier to water loss was similar in both stagnant and PEG6000 treatments. Moreover, plants growing in stagnant conditions tolerated a following severe condition of water deficit, whereas those growing in mimicked well-watered conditions did not.ConclusionsWe demonstrated that plants growing in stagnant conditions can withstand following severe conditions of water deficit. We propose that key root traits, such as the barrier to radial O2 loss, which are induced in stagnant conditions as well as mild conditions of water deficit, prime the plants for a following severe condition of water deficit
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