31,244 research outputs found
Long-term disturbance ecology
No full textStudy object and approaches
Disturbance is a short-lasting event or a series of distinct brief events (lasting hours to days) that alter vegetation or ecosystem conditions, potentially releasing ecological and environmental trajectories that may continue over decades to centuries. Natural disturbance agents might be fire, browsing, pests, wind, frost, heat, floods, volcanic eruptions, avalanches, landslides or rockfalls. Some disturbances such as fire and browsing might be prevalently caused by human impact. Climate-change impacts act at different temporal scales and are thus usually not considered as disturbances. Indeed climate change is defined by a series of weather conditions over decades (>30 years) and deals more with averages (e.g. mean July temperatures, mean annual temperatures) than extremes or singularities (IPCC, 2013), which are characteristic for disturbance. Palaeoecological climate-impact studies thus usually have multi-decadal temporal resolutions, while disturbance- impact studies should possess decadal resolutions, ideally 5-10 years (Birks, 1997b). The higher temporal resolution needed for the reconstruction of disturbance ecology from sedimentary records is explained by short-lived processes that might be overlooked if resolutions are coarser than c. 10 years. For instance, a fire event may release widespread successional trajectories involving intermediate community stages, as observed in Yellowstone National Park in 1988 (Whitlock and Millspaugh, 1996). In the case of non-contiguous sampling, missing the one sample or year containing the disturbance signal (e.g. fire) may mean failing to attribute the resulting vegetational pattern to the right forcing. Moreover, having resolutions coarser than 10 years may result in a dilution of the disturbance signal (and thus its gradual loss) and/or the non-recognition of short-lived terrestrial plants (e.g. expansions of Epilobium angustifolium, Anemone, Mentha, Urtica, Cichorioideae, Poaceae, Rosaceae) or fungi such as Sporormiella (Tinner et al., 1999, 2008; Gobet et al., 2003; Schwörer et al., 2015). Similarly, disturbance impacts may be quick and transient in aquatic ecosystems, as shown by expansions of macrophytes such as Typha latifolia and Nymphaea alba in response to fire-related nutrient input (Tinner et al., 1999) or of diatoms such as Achnanthes minutissima, Aulacoseira, Asterionella formosa and Fragilaria brevistriata after volcanic eruptions (Birks and Lotter, 1994)
West Berlin and Willy Brandt
No full textWilly Brandt belongs to one of the most significant and popular political figures of the 20th century. His name is inextricably linked to the West Berlin, peacekeeping, defense of freedom, and the constant fight for social justice. Willy Brandt witnessed the Berlin blockade which started in June 1948. Several years later, in 1958, he had to face a difficult challenge in form of the First Berlin Crisis, and in August 1961, he had to promptly react to the construction of the Berlin Wall. This thesis analyzes reactions of Willy Brandt to these crises, and with the use of e.g. results of opinion polls and the contemporary media reports, it proves that his popularity in this period of time significantly increased. The thesis also provides evidence that Willy Brandt was not only able to ensure the viability of West Berlin, but also its economic and cultural boom and secure its international position
Treeline and timberline dynamics
No full textPolar treeline and timberline
Today’s polar treeline runs along the northernmost part of Fennoscandia and further along the northern edge of the Kola Peninsula and the northern Russian mainland. In continental northern Russia the limit of tree growth (>2–3 m growth height) lies only slightly to the north of the Arctic Circle (66°32’ N) and is formed by Picea abies ssp. obovata, while in oceanic Fennoscandia it goes beyond 71° N and consists of Betula pubescens ssp. tortuosa. South of the polar treeline, dwarf shrub tundra, open birch stands and isolated birch and pine forests form vegetation mosaics. These parklands build the forest tundra and are bordered to the south by closed Pinus sylvestris forests that form the polar timberline (or forest limit) between 69° and 70° N. The polar treeline and timberline represent heat-deficiency limits, whereby, as a rough rule, the minimum for the existence of conifer trees (>2–3 m) is assumed to be 30 days per year with a temperature average above 10°C (e.g. Walter and Breckle, 1986). The global polar treeline has also been associated with growing seasons of 90– 106 days and seasonal mean temperatures between 5.1 and 6.9°C, similar to other treeline positions in the world (6.4 ± 0.7°C; Körner, 2012)
History of selected taxa
No full textBasics: absence, presence, population establishment, spatial expansions, population expansions, population declines and extinctions of taxa
In European pollen records, the frequencies of taxa vary between and within regions with regard to both timing and abundances. If curves of single taxa are parallelized in space (e.g. from west to east or north to south) according to age, often temporal differences appear in important data properties such as the onset and the maximum of the pollen curves. It is tempting to interpret the onset of the curve as arrival and the increase as expansion of the species, as was done by von Post (1924, 1929) and later on Bertsch (1935, 1940) and others, though in those early days, it was impossible to synchronize the pollen records using radiocarbon dating
The IIMI style manual
No full textDocumentation / Technical writing / Standards / Irrigation management / Computers / English language
Identifying Author Fingerprints in Texts via Graph Neural Networks
No full textThe world is generating more and more network data in many different areas (e.g., sensor networks, social networks and even text). A unique characteristic of these data is the coupling between data values and underlying irregular structure on which these values are defined. Thus, researchers developed Graph Neural Networks (GNNs) to use deep learning approaches on these irregular network data. GNNs developers tried to replicate the recent success of Convolutional Neural Networks (CNNs) and developed its graph counterpart Graph Convolutional Neural Network (GCNN) and more different variations of GNNs (e.g. EdgeNet). However, all these architectures are relatively young, and the impact of different parameters to classification result is not well researched compared to regular neural network architectures. To address this issue, we propose to use authorship attribution problem to research the impact of different architectures and their variations to classification accuracy and how GNNs can be used to improve on authorship attribution task compared to the baseline architectures. Explicitly, we define the dataset which is going to be used throughout the experiments and the method to convert text excerpts of authors into the network that can be classified with GNNs (called WAN). WAN is as a network that captures unique author fingerprint. We also define the set of GNN architectures (and different combinations and variations of them), baseline architecture (SVM) and experiments that are used with those architectures. This experiment setting allows us to compare different GNN architectures among themselves and the baseline architecture. Also, we define a method to reduce the dimensions of author fingerprints (WANs) and use these sparse author fingerprints for the same experiments with the same architectures. Numerical results show the improvement over the baseline architectures in nearly all defined experiments. Also, we found that more complex GNN architectures (e.g. EdgeNets) are superior to shallower architectures with more laborious experiments (e.g. classification by gender). More complex architectures also require hyperparameter re-tuning in order to achieve optimal results. Furthermore, experiments with sparse author fingerprints showed that we could achieve comparable results to standard fingerprints with faster training times and significantly reduced dimensions. GNN architectures used with sparse author fingerprints were usually superior to baseline architectures
Osteomorphological differences in the appendicular skeleton of Antidorcas marsupialis (Zimmerman, 1780) and Antidorcas bondi (Cooke & Wells, 1951) (Mammalia, Bovidae) with notes on the osteometry of Antidorcas bondi
No full textThe Trust Game: The influence of Trust on Collaboration in the light of Technological Innovations
No full textAdopting innovations is key for organizations to compete in a complex system, such as the transportation system. In a complex system where social (e.g. organizations) and technical (e.g. information systems) interact with each other, collaboration can be challenging. One of the barriers identified that hampers collaboration is trust. To understand the influence of trust on collaboration, enabled by technological innovations, simulation games in our perspective are a suitable method for our study. First, we introduce the results of a literature study that was carried out to identify related work regarding trust and simulation games. Subsequently, a case from the transport sector is defined to serve as a basis for the trust game. To conclude, we illustrate our simulation gaming approach and discuss the first initial results of a playtest session with the Trust Game.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Policy Analysi
Development and leadership in computer-mediated collaborative groups
No full textComputer-mediated collaboration is an important feature of modern organisational and educational settings. Despite its ever increasing popularity, it is still commonly compared unfavourably with face-to-face collaboration because non-verbal and paralinguistic cues are minimal. Although research on face-to-face group collaboration is well documented, less is known about computer-mediated collaboration.
The initial focus of this thesis was an in-depth analysis of a case study of a computer-mediated collaborative group. The case study was a large international group of volunteer researchers who collaborated on a two-year research project using asynchronous communication (email). This case study was a window on collaborative dialogue in the early 1990s (1992-94) at a time when information and communication technologies were at an early stage of development.
After identifying the issues emerging from this early case study, another case study using technologies and virtual environments developed over the past decade, was designed to further understand how groups work together on a collaborative activity. The second case study was a small group of students enrolled in a unit of study at Murdoch University who collaborated on a series of nine online workshops using synchronous communication (chat room). This case study was a window on collaborative dialogue in the year 2000 when information and communication technologies had developed at a rate which few people envisioned in the early 90s.
The primary aim of the research described in this thesis was to gain a better understanding of how computer-mediated collaborative communities develop and grow. In particular, the thesis addresses questions related to the developmental and leadership characteristics of collaborative groups.
Internet research requires a set of assumptions relating to ontology, epistemology, human nature and methodological approach that differs from traditional research assumptions. A research framework for Internet research - Complementary Explorative Data Analysis (CEDA) - was therefore developed and applied to the two case studies.
The results of the two case studies using the CEDA methodology indicate that computer-mediated collaborative groups are highly adaptive to the aim of the collaborative task to be completed, and the medium in which they collaborate. In the organisational setting, it has been found that virtual teams can devise and complete a collaborative task entirely online. It may be an advantage, but it is certainly not mandatory to have preliminary face-to-face discussions. What is more important is to ensure that time is allowed for an initial period of structuration which involves social interaction to develop a social presence and eventually cohesiveness. In the educational setting, a collaborative community increases pedagogical effectiveness. Providing collaborative projects and interdependent tasks promotes constructivist learning and a strong foundation for understanding how to collaborate in the global workplace. Again, this research has demonstrated that students can collaborate entirely online, although more pedagogical scaffolding may be required than in the organisational setting. The importance of initial social interaction to foster a sense of presence and community in a mediated environment has also been highlighted.
This research also provided greater understanding of emergent leadership in computer-mediated collaborative groups. It was found that sheer volume of words does not make a leader but frequent messages with topic-related content does contribute to leadership qualities.
The results described in this thesis have practical implications for managers of virtual teams and educators in e-learning
Do UK based weight management programmes cause weight loss maintenance in adults? A systematic review
No full textThe aim of this dissertation was to examine whether UK based weight management programmes promote weight loss maintenance (follow up of 12 months to assess effectiveness of intervention in weight loss) in adults through the process of a systematic review. The World Health Organisation (WHO) has described obesity as a "global epidemic". Weight management comprises two phases; weight loss and weight loss maintenance. The latter phase is the true goal for obesity and the most difficult element of weight management to achieve. However much less is know about this as compared with the weight loss phase. There is little purpose in committing time and money to reducing obesity if the weight is regained. This is counter-productive and weight loss maintenance is essential to combat the obesity epidemic. Searches were made for relevant information from a variety of scientific online databases and journals,. Seven articles met the inclusion criteria and were analysed in the review. All studies incorporated a multi-component (diet, exercise, behaviur modification) intervention approach. All control and internvetion groups reported weight loss at 12 months when compared with baseline. All groups recieved an intervention. One study reported a significant difference (P<0.05) between groups. Four studies reported on at least one component (diet, physical activity, behaviour modification) however there was not enough information to conclude whether they complied with national guidelines (NICE CG43 and SIGN 115). High attrition rates and loss to follow up are problematic for each study except one. Analysis on an intention to treat basis was common however this is problematic and there are alternative methods which may be more suitable for dealing with missing data
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