| 1. |
- Ari Noriega, Jorge, et al.
(författare)
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Does ecotourism impact biodiversity? : An assessment using dung beetles (Coleoptera: Scarabaeinae) as bioindicators in a tropical dry forest natural park
- 2020
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Ingår i: Ecological Indicators. - : Elsevier. - 1470-160X .- 1872-7034. ; 117
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Tidskriftsartikel (refereegranskat)abstract
- Ecotourism can be defined as an environmental activity that takes place in well-preserved areas for recreation and with the responsibility of promoting their conservation. Nowadays, ecotourism is seen as a friendly pastime, but it can potentially affect negatively community diversity and structure by a number of processes such as soil compaction, erosion, and habitat alteration, among many others. Nonetheless, there is hardly any information on the impact of ecotourism in the Tropical Dry Forests and protected areas of the Neotropical region. In an attempt to fill this knowledge gap, the effect of ecotourism was evaluated in a study of a Tropical Dry Forest in the Tayrona National Natural Park of Colombia using dung beetles as bioindicators. A large-scale sampling of three sites with different levels of tourism intensity (no tourism - NT, low tourism - LT, and high tourism - HT) was performed using pitfall tramps baited with human/pig dung during two climatic seasons (rainy and dry). A total of 3238 individuals belonging to nine genera and 15 species were collected. Significant differences in abun-dances, richness, and the Shannon Wiener diversity index were observed between areas with tourism and those without. These differences disappeared during the dry season in response to the strong reduction in species abundance and richness associated to that time of year. All areas maintained a homogeneous beetle structure in terms of functional groups present irrelevant of the intensity level of tourism. Beta diversity analysis shows that the dung beetle assemblage has a nested structure, indicating that the pressure exerted by tourism entails the loss of particular species. Our results advocate that it is necessary to implement conservation strategies in order to reduce the negative impact of tourism on the National Park's biodiversity.
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| 2. |
- González-Zapata, José Luis, et al.
(författare)
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Introducing random bio-terpene segments to high cis-polybutadiene : making elastomeric materials more sustainable
- 2020
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 10:72, s. 44096-44102
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we explore the statistical copolymerization of 1,3-butadiene with the terpenic monomers myrcene and farnesene, carried out via coordination polymerization using a neodymium-based ternary catalytic system. The resultant copolymers, poly(butadiene-co-myrcene) and poly(butadiene-co-farnesene), were synthesized at different monomer ratios, elucidating the influence of the bio-based monomer content over the kinetic variables, molecular and thermal properties, and the reactivity constants (Fineman-Ross and Kelen-Tudos methods) of the resultant copolymers. The results indicate that through the herein employed conditions, it is possible to obtain more sustainable high-cis (approximate to 95%) polybutadiene elastomers with random and tunable content of bio-based monomer. Moreover, the polymers exhibit fairly high molecular weights and a rather low dispersity index. Upon copolymerization, the T-g of high-cis PB can be shifted from -106 to -75 degrees C (farnesene) or -107 to -64 degrees C (myrcene), without altering the microstructure control. This work contributes to the development of more environmentally friendly elastomers, to form green rubber materials.
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| 3. |
- Holzapfel, André, 1976-, et al.
(författare)
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On the automatic identification of difficult examples for beat tracking : towards building new evaluation datasets
- 2012
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Ingår i: Proceedings of the IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP). - : IEEE conference proceedings. ; , s. 89-92
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Konferensbidrag (refereegranskat)abstract
- In this paper, an approach is presented that identifies music samples which are difficult for current state-of-the-art beat trackers. In order to estimate this difficulty even for examples without ground truth, a method motivated by selective sampling is applied. This method assigns a degree of difficulty to a sample based on the mutual disagreement between the output of various beat tracking systems. On a large beat annotated dataset we show that this mutual agreement is correlated with the mean performance of the beat trackers evaluated against the ground truth, and hence can be used to identify difficult examples by predicting poor beat tracking performance. Towards the aim of advancing future beat tracking systems, we demonstrate how our method can be used to form new datasets containing a high proportion of challenging music examples.
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| 4. |
- Zapata, Jose Ricardo, et al.
(författare)
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Assigning a confidence threshold on automatic beat annotation in large datasets
- 2012
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Ingår i: Proceedings of ISMIR - International Conference on Music Information Retrieval. ; , s. 157-162
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Konferensbidrag (refereegranskat)abstract
- In this paper we establish a threshold for perceptually acceptable beat tracking based on the mutual agreement of a committee of beat trackers. In the first step we use an existing annotated dataset to show that mutual agreement can be used to select one committee member as the most reliable beat tracker for a song. Then we conduct a listening test using a subset of the Million Song Dataset to establish a threshold which results in acceptable quality of the chosen beat output. For both datasets, we obtain a percent age of trackable music of about 73%, and we investigate which data tags are related to acceptable and problematic beat tracking. The results indicate that current datasets are biased towards genres which tend to be easy for beat tracking. The proposed methods provide a means to automatically obtain a confidence value for beat tracking in non-annotated data and to choose between a number of beat tracker outputs.
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