1,720,978 research outputs found
NutGEnIE 1.0: nutrient cycle extensions to the cGEnIE Earth system model to examine the long-term influence of nutrients on oceanic primary production
Full text linkUnderstanding the nuances of the effects of nutrient limitation on oceanic primary production has been the focus of many bioassay experiments by oceanographers. A theme of these investigations is that they identify the currently limiting nutrient at a given location, or in other words they identify the proximate limiting nutrient (PLN). However, the ultimate limiting nutrient (ULN; the nutrient whose supply controls system productivity over extensive timescales) can be different from the PLN. Our motivation is to investigate the identity of the ULN. The ULN constrains oceanic primary production over extensive timescales and consequently overall ocean fertility. The rate of oceanic photosynthesis affects planetary oxygen and carbon dioxide, impacting climate. Understanding past ocean fertility is fundamental to understanding Earth system history and biological evolution.Investigations that have considered the ULN have often utilised box models for example the work of, Tyrrell (1999) and Lenton and Watson (2000). To facilitate investigation of the ULN the carbon-centric Grid Enabled Integrated Earth system model (cGEnIE) nutrient cycles have been extended to create NutGEnIE. NutGEnIE incorporates three open nutrients cycles nitrogen, phosphorus, and iron. The impacts of diazotrophs, capable of fixing nitrogen, are represented alongside those of other phytoplankton. NutGEnIE is capable of extended duration model simulations necessary to investigate the ULN while, at the same time, including iron as a potentially limiting nutrient. NutGEnIE is described here, with particular focus on the biogeochemical cycles of iron, nitrogen and phosphorus. Model results are compared to ocean observational data to assess the degree of realism. Model-data comparisons include physical properties, nutrient concentrations, and process rates (e.g., export and nitrogen fixation). The comparisons of NutGEnIE to ocean observational data are largely positive, suggesting that the dynamics of NutGEnIE are valid. The validations, allied to the ability to run an Earth System model with open nutrients cycles of nitrogen, phosphorus, and iron over extensive time periods supports the proposed use of NutGEnIE to revisit the question of the ULN for oceanic primary production
Neurodiversity: An Important Axis of Diversity in Ocean Sciences
Full text linkNeurodiversity refers to variations in the human brain that affect information processing; it includes conditions, or “neurotypes,” such as autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), dyslexia, dyscalculia, and dyspraxia, among others. Neurodiversity can be conceptualized as significant differences in the ways that individuals process information; such differences may concern written or verbal language, sensory information, body language, or social interactions. These differences have been historically viewed within the medical model of disability, for example, as deficits in ability through a diagnosed condition, often associated with a goal of curing or managing the condition.</jats:p
Long-term impacts of mixotrophy on ocean carbon storage: insights from a 10 000 year global model simulation
Full text linkMixotrophs-organisms that combine the use of light and inorganic resources with the ingestion of prey-have been shown in simulations to increase mean organism size and carbon export in the ocean. These simulations have, however, been limited to decade-long timescales that are insufficient to investigate the impacts of mixotrophy on the ocean's long-term capacity for carbon storage. Here we explore these long-term impacts using a low-resolution ocean model that resolves important feedbacks between surface ecology and the ocean interior over multi-millennial periods. The model was compared in two configurations: one with a strict distinction between phytoplankton and zooplankton populations and one in which all populations were assumed to be capable of mixotrophy. Consistent with earlier studies, we found that increased carbon and nutrient export associated with mixotrophy was rapidly established within the first few years of the simulation and was robust over long time scales. However, we also found that these increases were partially offset over longer time scales by a decline in “preformed” inorganic carbon and nutrients entering the deep ocean via the sinking of surface waters. Over the 10 000 year duration of the simulations, we found that ecologically-driven changes in C export increased the oceanic C inventory by up to 537 Pg, and that this was partially offset by decline of 150 Pg in the preformed C inventory, leaving a net increase of up to 387 PgC (∼1 %)
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
A trait-based modelling approach to planktonic foraminifera ecology
Full text linkDespite the important role of planktonic foraminifera in regulating the ocean carbonate production and their unrivalled value in reconstructing paleoenvironments, our knowledge on their ecology is limited. A variety of observational techniques such as plankton tows, sediment traps and experiments, have contributed to our understanding of foraminifera ecology. But, fundamental questions around costs and benefits of calcification, and the effect of nutrients, temperature and ecosystem structure on these organisms remain unanswered. To tackle these questions, we take a novel mechanistic approach to study planktonic foraminifera ecology based on trait theory. We develop a 0-D trait-based model to account for the biomass of prolocular (20 μm) and adult (160 μm) stages of non-spinose foraminifera species and investigate their potential interactions with phytoplankton and other zooplankton under different temperature and nutrient regimes. Building on the costs and benefits of calcification, we model two ecosystem structures to explore the effect of resource competition and temperature on planktonic foraminifera biomass. By constraining the model results with ocean biomass estimations of planktonic foraminifera, we estimate that the energetic cost of calcification could be about 25–50 % and 20–35 % for prolocular and adult stages respectively. Our result suggest that the shell provides protection among predation (e.g. pathogens protection) and that the invariably low standing biomass of planktonic foraminifera plays a key role in their survival from predation, along with their shell protection. Temperature appears to be an important factor in regulating foraminifera biomass in the early developmental stage, whereas resource competition is a key in controlling adults' biomass and feeding strategy
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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