1,721,933 research outputs found
Cycling of trace metals in coastal waters : biogeochemical processes involving suspended particles
No full textRecent investigations have shown that suspended particles exert a significant influence on the distribution and biogeochemical cycling of trace metals in seawater. These processes are particularly important in temperate coastal waters, characterised by elevated phytoplankton activity during the spring period. In order to investigate the effect of suspended particles, particularly those of biogenic origin, on the biogeochemical cycling of Fe, Mn, Cu, Co, Ni, Cd, Zn and Pb in coastal waters, dissolved and particulate trace metal samples (suspended and settling), together with salinity, nutrients, total particulate carbon and other related data were collected during 19 cruises aboard RV Calanus between March, 1991 and February, 1992 in Loch Linnhe; a silled fjord on the west coast of Scotland. Particulate trace metal samples were also collected on a single cruise (CH72, October 1990) in the extended estuarine plume of the River Rhine as part of the Rhine Outflow Experiment. Analytical techniques for the analysis of particulate material were developed. These include weak acid leaches of the environmentally available metal fraction and strong acid digestion, utilising microwave heating, to liberate the metals associated with the refractory mineral phases. Electron microscopy of suspended sediment samples showed the spring phytoplankton bloom comprised the diatoms Skeletonema costatum and Thallassiosira sp. Particulate Cd and leachable-P showed increasing levels coincident with the onset of the bloom. Phosphorus was rapidly recycled after the bloom crash while Cd concentrations continued to increase in particles, reaching a maximum of 6.33 nmol g-1, an enrichment relative to the winter particle population of ∼8.5. The difference in the peak of recycling of Cd relative to P was greater than 8 days but less than 15 days and suggests that in contrast to the deep ocean, Cd and P are decoupled in the coastal environment. A substantial amount (∼44% ) of the total annual flux of Mn to the sediments was recycled. The estimated recyling flux was found to have a strong seasonal pattern, with little or no Mn recycling prior to the spring phytoplankton blooms and increasing value after the bloom crash, reaching a maximum of 348 μmol m^-1 day^-1 in late autumn. Levels then decreased, attaining pre-bloom levels early in the following year. This cycle suggests that bacterial decay of deposited organic carbon associated with the spring bloom maintained reducing conditions in the sediments throughout most of the year. Surface sediments were sufficiently oxic to prevent the release of reduced Mn for only a brief period prior to the spring bloom.</p
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
Ecological and genetic advances in the cultivation of Tuber Spp
No full textRecent advances on the ecology and genetics of true truffles (Tuber spp.) are reported and their impact on truffle cultivation is discussed. New insights have been gained on truffle soil ecology and interrelationships of truffles with associated microorganisms in the soil. For instance, some bacteria seem to play a key role in truffle fruiting body formation and maturation. However, the most important advance in truffle genetics over the past 20 years has been the sequencing of the Tuber melanosporum genome and the discovery that truffles, like other Pezizalean fungi, are heterothallic. This finding has had a significant impact on research on truffles and many studies have been devoted to better understanding the distribution of the mating types in soil in natural and cultivated truffià ̈res. The characterization of the mating type idiomorphs of several Tuber species has led to the possibility of selecting mycelial strains for truffle cultivation in particular sites
What makes a good truffle infected tree?
No full textModern truffle cultivation is based on planting Tuber infected plants in suitable sites. The first step is the production of truffle infected plants in greenhouses, generally using spore inoculation techniques. Other less common methods include the inoculating plants with pure cultures and the mother plant techniques. Regardless of the inoculation technique used, it is advisable to check the geographic origin of the inoculum, and selecting the most suitable one for the climatic conditions of the site where the plants are to be planted. It is also important to verify the quality of the inoculum before inoculating the plants. In particular, when using spore inoculation techniques, the ascomata used for making the spore suspension should undergo morphological observation and molecular testing to verify the absence of less valuable Tuber species. It is also advisable to assess the abundance of mature spores and their vitality particularly when the inoculum is not produced from fresh truffle. In contrast when mycelial inoculation or mother plant techniques is used it is important to ensure that the plants are carrying two compatible mating types and that the mother plants are free of contamination with other ectomycorrhizal fungi
Ecological and genetic advances in the cultivation of Tuber Spp
No full textRecent advances on the ecology and genetics of true truffles (Tuber spp.) are reported and their impact on truffle cultivation is discussed. New insights have been gained on truffle soil ecology and interrelationships of truffles with associated microorganisms in the soil. For instance, some bacteria seem to play a key role in truffle fruiting body formation and maturation. However, the most important advance in truffle genetics over the past 20 years has been the sequencing of the Tuber melanosporum genome and the discovery that truffles, like other Pezizalean fungi, are heterothallic. This finding has had a significant impact on research on truffles and many studies have been devoted to better understanding the distribution of the mating types in soil in natural and cultivated truffià ̈res. The characterization of the mating type idiomorphs of several Tuber species has led to the possibility of selecting mycelial strains for truffle cultivation in particular sites
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
The Mysteries of the White Truffle: Its Biology, Ecology and Cultivation
Full text linkTuber magnatum Picco is the most expensive of the truffles and a great deal of research has been carried out in an attempt to solve the mysteries of its ecology and biology. However, considerable work remains to be done particularly on those secrets of its life cycle that remain a mystery. It is known that T. magnatum is heterothallic, but it has yet to be determined how fertilization occurs between the two strains of different mating types. It is also known that the white truffle is an ectomycorrhizal fungus, and its mycorrhizas can be produced in greenhouses, but then they seem to disappear in the field. The role of other soil microorganisms, fungi and bacteria, on its soil mycelial development and fructification is intriguing but is far from being completely understood. All these uncertainties have made the cultivation of T. magnatum extremely difficult and only recently have we had the scientific proofs that it is possible. Even so, many questions remain unanswered and the management practices of T. magnatum plantations are still to be better defined to also enable the taming of this truffle
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