Spelling suggestions: "subject:"cooccurrence"" "subject:"cooccurrences""
71 |
Co-ocorrência, interações tróficas e distribuição potencial da onça-pintada (Panthera onca) no bioma Amazônia / Co-occurrence, trophic interactions and potential distribution of jaguar (Panthera onca) in the Amazon biomeFrancesca Belem Lopes Palmeira 27 May 2015 (has links)
Predadores de topo desempenham um papel importante na manutenção dos sistemas em que eles ocorrem porque influenciam diretamente a estrutura e a dinâmica de comunidades. Desta forma, este estudo descreveu alguns mecanismos de co-ocorrência espaço-temporal entre a onça-pintada (Panthera onca) e duas espécies de mesopredadores (Puma concolor e Leopardus pardalis), o seu controle top-down na comunidade de mamíferos e os requerimentos ambientais que determinam a sua distribuição no bioma Amazônia. Para as análises de co-ocorrência espaço-temporal foram utilizados o modelo de ocupação e a densidade de Kernel utilizando os registros de armadilhamento fotográfico (2008-2011). Para descrever o controle top-down foi elaborada uma rede trófica utilizando os itens alimentares consumidos pelas espécies e disponíveis na literatura (1983-2014). Para indicar quais as áreas mais adequadas foi utilizado o modelo de distribuição de espécies utilizando as localizações geográficas de ocorrência da espécie que foram compiladas de três diferentes bases de dados (2000-2013). A ocorrência das duas espécies de mesopredadores não foi diferente nos sítios com e sem a onça-pintada nas quatro temporadas de amostragem. A probabilidade de detecção da jaguatirica foi maior nos sítios com a presença da onça-pintada em apenas uma temporada de amostragem. A sobreposição no período de atividade das espécies de mesopredadores com a onça-pintada foi baixa, com cerca de 55% de sobreposição. Também ocorreu uma mudança razoável no período de atividade das espécies entre as temporadas de amostragem, com mínima de 32% e máxima de 56% de sobreposição. As maiores diferenças na detecção e na sobreposição temporal ocorreram na terceira temporada quando teve o maior número de capturas e recapturas da onça-pintada. A rede trófica apresentou seis níveis e grande riqueza de espécies e densidade de interações. Após a remoção da onça-pintada, houve a perda de um nível trófico e de aproximadamente 20% de interações. Quando comparada a distribuição atual da onça-pintada com a histórica, foi possível constatar a perda de espaço ambiental em áreas mais frias (< 6,3 °C), mais secas (< 288 mm), mais úmidas (> 7517 mm) e com maior elevação (> 3597 m). O modelo de distribuição também indicou que muitas áreas potenciais estão disponíveis à ocorrência da onça-pintada e que algumas merecem atenção, especialmente, nas porções leste e sul da Amazônia onde a espécie corre maior risco de desaparecimento local devido à antropização acelerada. Este estudo forneceu significativa contribuição para a compreensão da população de onça-pintada na Amazônia, bioma que ainda possui a maior lacuna de conhecimento sobre a biologia e ecologia da espécie. Demonstrou o efeito da sua presença na detectabilidade e no período de atividade de outras espécies. Também demonstrou seu papel ecológico como predador de topo exclusivo porque foi a única espécie que predou todas as outras de níveis tróficos inferiores. Descreveu o espaço ambiental originalmente ocupado (distribuição histórica) e o perdido (distribuição atual). Indicou as áreas mais adequadas à sua ocorrência e aquelas potenciais ao seu desaparecimento. / Apex predators play an important role in the maintenance of systems in which occur because they directly influence the structure and dynamics of communities Thus, this thesis aims to describe some of the mechanisms of spatio-temporal co-occurrence between the jaguar (Panthera onca) and mesopredators (Puma concolor and Leopardus pardalis), their top-down control on the community and environmental requirements that determine their distribution. To the analyses of spatio-temporal co-occurrence were used the occupancy model and the Kernel density with records derived from camera trapping (2008-2011). To the analysis of trophic networks was used a foodweb model with prey spectra of felids compiled from the available literature (1983-2014). To indicate the most suitable areas to its occurrence was used a species distribution model with geographic location of the species compiled from three different databases. The occupation of the two species of mesopredators was not different among sites with and without jaguar. The probability of detection was different for ocelot, with higher detection on sites with than without jaguar. The overlap in the activity pattern among jaguar and mesopredators was low, with approximately 55% of overlapping. Also there was a reasonable change in the overlap between sampling seasons, with a minimum of 32% and maximum of 56% of the difference in the activity pattern. The differences in the detection and temporal overlap occurred in the third season when occurred the highest number of jaguar captures and recaptures. The trophic network presented six levels and, a high species richness and links density. After removal of the jaguar, a trophic level and approximately 20% of links were lost. When compared historical and current distributions, the loss of environmental space occurred in areas colder (< 6.3 ° C), drier (< 288 mm), wetter (> 7517 mm) and at higher elevation (> 3597 m). The distribution model also indicated that there is many potential suitable areas available to the jaguar occurrence and, some of them deserve attention, particularly, in eastern and southern portions of Amazonia where the species is most at risk of local extinction. This study provided a significant contribution to the knowledge of the population of jaguar in the Amazon biome which still has the largest gap of information on the biology and ecology of the species. It demonstrated the effect of the presence of the species in the detectability and the activity pattern of others. Also, it demonstrated their ecological role as an apex predator exclusive because it was the only one that ate all other species of lower trophic levels. It described the environmental space originally occupied (historical distribution) and lost (current distribution). It indicated potential suitable areas to its occurrence and threatened areas to its disappearance.
|
72 |
Padrões de comportamentos de risco e proteção relacionados a doenças crônicas não transmissíveis entre adolescentes brasileiros / Patterns of risk and protective behaviors related to non-communicable diseases among Brazilian adolescentsCamila Zancheta Ricardo 29 June 2017 (has links)
Introdução: Um pequeno grupo de fatores de risco modificáveis é responsável por grande parte da mortalidade e morbidade devidas a doenças crônicas não transmissíveis (DCNT). Esses comportamentos de risco, frequentemente, se originam na adolescência e se mantêm na vida adulta, com consequências a curto, médio e longo prazo. Atualmente, além de determinar a prevalência de cada um dos fatores de risco, destaca-se a importância de avaliar como eles se agrupam na população, pois alguns desses comportamentos podem interagir entre si, produzindo um risco ainda maior do que a soma de riscos individuais. Objetivos: Identificar padrões de comportamentos de risco e proteção relacionados a doenças crônicas entre adolescentes brasileiros e verificar sua associação com características socioeconômicas e demográficas; avaliar a coocorrência de múltiplos fatores de risco entre os adolescentes, identificar agrupamentos e verificar a associação do acúmulo de riscos com características da população. Método: A fonte de dados utilizada foi a Pesquisa Nacional de Saúde do Escolar 2012, que coletou informações sobre saúde de adolescentes por meio de questionário autoaplicável em amostra representativa de alunos matriculados no 9º ano do ensino fundamental de escolas públicas e privadas brasileiras. Foram utilizadas informações sobre alimentação, atividade física, tabagismo, consumo de álcool e características socioeconômicas e demográficas. A análise fatorial foi usada para identificar padrões de comportamento a partir de uma lista de fatores de risco e proteção para DCNT. A associação entre os padrões encontrados e as características dos estudantes foi avaliada com modelos de regressão linear. A coocorrência de múltiplos fatores de risco foi avaliada com um escore correspondente à soma de cinco comportamentos: 1) Consumo infrequente de frutas e hortaliças, 2) Consumo frequente de alimentos ultraprocessados; 3) Atividade física insuficiente; 4) Fumo; e 5) Consumo abusivo de álcool. Os agrupamentos foram identificados utilizando a razão entre a prevalência observada e a prevalência esperada (O/E) para cada uma das 32 combinações de fatores de risco possíveis. As razões de prevalência O/E maiores que um foram indicativas de um agrupamento (ou cluster). A associação entre o acúmulo de quatro ou cinco dos fatores de risco e as variáveis socioeconômicas e demográficas foi avaliada com a utilização de modelo de regressão logística. Resultados: Foram encontrados quatro padrões de comportamentos: \"alimentação não saudável\", \"alimentação saudável\", \"atividade física\" e \"álcool e cigarro\". De forma geral, os grupos que apresentaram pior perfil de adesão aos padrões comportamentais encontrados foram: meninas, adolescentes mais velhos, e aqueles que não viviam com a mãe e o pai. Em relação à ocorrência simultânea dos fatores de risco definidos, apenas 2,5% dos adolescentes não apresentou nenhum dos comportamentos, enquanto 38,1% acumulou dois, 34,2%, três, 8,9%, quatro e 1,5%, os cinco fatores de risco estudados. As combinações de comportamentos mais comuns nos adolescentes foram aquelas em que estavam presentes os fatores de risco relacionados a alimentação e atividade física, ainda que as razões O/E fossem próximas a um. As maiores razões O/E foram encontradas para as combinações em que estavam presentes o cigarro e o álcool, indicando a forte correlação entre o uso das duas substâncias, ainda que a prevalência seja baixa nessa faixa etária. As características associadas ao acúmulo de quatro ou cinco fatores de risco foram: sexo feminino, ter mais de 16 anos, não viver com a mãe e o pai, menor escolaridade da mãe, ser aluno de escola pública, viver em municípios que sejam capitais de estado e nas regiões mais desenvolvidas do país. Conclusão: Os comportamentos de risco relacionados a alimentação e atividade física são os mais frequentes e se distribuem de forma independente nessa faixa etária. Por outro lado, o uso de cigarro e álcool é bastante correlacionado, apesar da baixa prevalência. A presença de múltiplos fatores de risco é comum nessa população e a identificação de grupos mais vulneráveis pode auxiliar no direcionamento de estratégias de promoção à saúde e prevenção de agravos relacionadas ao controle de DCNT ainda durante a adolescência / Introduction: A small group of modifiable risk factors accounts for most of the disease burden and mortality due to non-communicable diseases (NCD). These risk behaviors frequently originate in adolescence and remain in adulthood with short-, medium- and long-term consequences. Currently, in addition to determining the prevalence of each of the risk factors, it is important to evaluate how they cluster among the population, since some of these behaviors might interact with each other, producing an even greater risk than the sheer sum of individual risks. Objectives: To identify patterns of risk and protection behaviors related to chronic diseases among Brazilian adolescents and to verify their association with socioeconomic and demographic characteristics; And to assess the co-occurrence of multiple risk factors among adolescents, to investigate the clustering of risk factors, and to verify the association of presence of multiple risk factors with population characteristics. Methods: Our data source was the Brazilian National Survey of School Health (Pesquisa Nacional de Saúde do Escolar - PeNSE) 2012, which collected data on adolescent health through a self-administered questionnaire in a representative sample of students enrolled in the 9th grade of elementary education in public and private Brazilian schools. We used data about diet, physical activity, smoking, alcohol consumption, socioeconomic and demographic characteristics. Factor analysis was used to identify patterns of behavior from a list of risk and protective factors for NCD. The association between the identified patterns and students\' characteristics was evaluated using linear regression models. The co-occurrence of multiple risk factors was evaluated with a score corresponding to the sum of five behaviors: 1) Infrequent consumption of fruits and vegetables, 2) Frequent consumption of ultraprocessed foods; 3) Insufficient physical activity; 4) Smoke; and 5) Abuse of alcohol. The clustering was identified using the ratio between the observed and expected prevalence (O/E) for each of the 32 combinations of risk factors. Observed/expected ratios (O/E) higher than 1 were considered an indicative of clustering. The association between the prevalence of four or five risk factors and the socioeconomic and demographic variables was evaluated using a logistic regression model. Results: Four patterns of behavior were found: \"unhealthy diet\", \"healthy diet\", \"physical activity\" and \"alcohol and cigarette use\". In general, the groups that presented the worst profile of adherence to the behavioral patterns found were: girls, older adolescents, and those who did not live with the mother and the father. Regarding the simultaneous occurrence of defined risk factors, only 2.5% of adolescents did not present any of the behaviors, while 38.1% accumulated two, 34.2%, three, 8.9%, four and 1.5% all of risk factors analyzed. The most common combinations of behaviors in adolescents were those in which risk factors related to diet and physical activity were present, even though O/E ratios were close to one. The highest O/E ratios were found for the combination of cigarette and alcohol, suggesting a strong correlation between the use of both substances, although the prevalence is low in this age group. The characteristics associated with the presence of four or five risk factors were: female, being over 16 years old, not living with the mother and father, lower education of the mother, being a public school student, living in capitals, and living in the more developed regions of the country. Conclusion: The risk behaviors related to diet and physical activity are the most frequent and occur independently in this age group. On the other hand, cigarette and alcohol use is highly correlated, despite the low prevalence. The presence of multiple risk factors is common in this population and the identification of more vulnerable groups can support strategies for health promotion and prevention of diseases related to the control of CNCD even during adolescence
|
73 |
Отбор союзов для русского словника шведско-русского и русско-шведского словаря Мини+ / Selecting Russian Conjunctions for Swedish-Russian and Russian-Swedish Dictionary Mini+Dergacheva, Irina January 2013 (has links)
The purpose of this paper is to work out criteria for selection of Russian conjunctions for the Swedish-Russian and Russian-Swedish dictionary Mini+ and to suggest a list of conjunctions to be included in it. The present study aims at collecting information, classifying it and examining Russian conjunctions in present-day Russian. The study also systemizes gathered material according to its diachronic features and makes corpus-based co-occurrence analysis, using Russian National Corpus (RNC) and Google Scholar. The paper presents a list of conjunctions to be included into the Russian part of the lexicon, based primarily on their grammatical and stylistic criteria as well as the results of the corpus-based frequency analysis. The choice takes into consideration limitations in size of the given dictionary. Out of a total 272 conjunctions, 55 were chosen for the Russian Swedish Mini+ dictionary. The major group (35) is simple conjunctions that frequently occur in corpus-based search and that are necessary to build basic grammar structures as well as other compound conjunctions, ex. а, даже, едва, если, чтобы, хотя. The second group (13) is compound conjunctions that are important for building most frequent subordinate clauses. The third group (7) is compound conjunctions that frequently occur in corpora.
|
74 |
The role of situations and thematic reorganization in the conceptual processing of abstract concepts / Le rôle des situations et d’organisation thématique dans le traitement conceptuel des concepts abstraitsBruhl, Analee 06 June 2014 (has links)
Le système conceptuel humain est connu pour contenir deux types de concepts principaux: concrets et abstraits. Les concepts abstraits tels que l'opinion ou la détermination expriment les relations séquentielles entre les entités, ainsi que les états mentaux et introspectifs qui caractérisent la conscience humaine. Les recherches antérieures se sont très peu intéressées à la manière dont les concepts abstraits sont représentés tant sur le plan cognitif que conceptuel. Dans la littérature, la représentation, récupération et traitement des concepts abstraits dans le système conceptuel sont principalement attribués au phénomène connu sous le nom de l’effet de concrétude (avantage pour les mots concrets relativement aux mots abstraits par rapport aux processus cognitifs). Les théories actuelles de la cognition incarnée telles que la Théorie des Symboles Perceptifs proposent que les expériences réelles et les informations situationnelles pourraient jouer un rôle clé dans la façon dont les gens simulent, comprennent et utilisent les concepts abstraits. Le but principal de la présente thèse était d’explorer la structure conceptuelle, l'organisation et la représentation des concepts abstraits dans le système cognitif. Pour ce faire, quatre séries d'études expérimentales utilisant des tâches de catégorisation et de jugement de similarité ont été réalisées. Le premier objectif était de déterminer l’effet des informations situationnelles sur la réorganisation des concepts abstraits. Le deuxième objectif était de déterminer si une organisation taxonomique ou thématique pourrait être à la base de la représentation conceptuelle des concepts abstraits. Les résultats suggèrent que la réorganisation thématique et les informations situationnelles jouent un rôle central dans le traitement et la réorganisation conceptuels des concepts abstraits. / The human conceptual system is known to contain two main types of concepts: concrete and abstract. Abstract concepts such as opinion or determination express the sequences of relations between different entities. They also manifest the internal and introspective states of existence that characterize the human consciousness. The semantic representation and organization of abstract concepts has received very little attention in the cognitive psychology literature over the past decades, whereas the vast majority of studies have been dedicated to concrete concepts. Previous research on abstract concepts has explained how they are conceptually represented by focusing on their differences from concrete concepts i.e., the concreteness effect. Current theories of grounded cognition such as the Perceptual Symbol Systems Theory propose that situational knowledge and experiences could play a key role in how people simulate, understand and use abstract concepts.Our aim was to assess the principles that underlie the conceptual structure, organization and representation of abstract concepts within the cognitive system. Four series of behavioural experiments using categorization and similarity judgment tasks were designed to investigate the role of situational information and thematic organization in the processing of abstract concepts. The results indicated that the co-occurrences and the experiencing of unrelated abstract concepts in relevant situations significantly influenced the emergence of novel thematic reorganizations between the concepts compared to baseline. Thus, suggesting the central role that thematic reorganization and situational information play in the conceptual representation of abstract concepts.
|
75 |
Photometric Methods for Autonomous Tree Species Classification and NIR Quality InspectionValieva, Inna January 2015 (has links)
In this paper the brief overview of methods available for individual tree stems quality evaluation and tree species classification has been performed. The use of Near Infrared photometry based on conifer’s canopy reflectance measurement in near infrared range of spectrum has been evaluated for the use in autonomous forest harvesting. Photometric method based on the image processing of the bark pattern has been proposed to perform classification between main construction timber tree species in Scandinavia: Norway spruce (Picea abies) and Scots Pine (Pinus sylvestris). Several feature extraction algorithms have been evaluated, resulting two methods selected: Statistical Analysis using gray level co-occurrence matrix and maximally stable extremal regions feature detector. Feedforward Neural Network with Backpropagation training algorithm and Support Vector Machine classifiers have been implemented and compared. The verification of the proposed algorithm has been performed by real-time testing.
|
76 |
VARIATIONS IN THE CO-OCCURRENCE OF MENTAL HEALTH PROBLEMS IN ADOLESCENTS WITH PRENATAL DRUG EXPOSUREKim, June-Yung 07 September 2020 (has links)
No description available.
|
77 |
The Ecology of Cactoblastis Cactorum (Berg) (Lepidoptera:pyralidae) in FloridaSauby, Kristen Erica 08 August 2009 (has links)
I used a theoretical model to determine the conditions under which Cactoblastis cactorum populations would be expected to experience positive population growth. Results from simulations suggest that host species richness, host quality, and the C. cactorum death rate interact to determine the probability of C. cactorum positive population growth. I also studied the influence of host diversity empirically. Cactoblastis cactorum prevalence was significantly higher when O. stricta was present in the community. Also, higher species richness within host assemblages led to a higher prevalence of infestation than in single-species host assemblages. Finally, I explored cooccurrence patterns of native cactuseeding insects in an effort to document the impact of C. cactorum to native insect assemblages. The presence of C. cactorum in a community did not appear to affect the structure of native cactuseeding insect assemblages.
|
78 |
Quantifying Phonological Feature Co-occurrenceApril Lynn Grotberg (13171419) 29 July 2022 (has links)
<p>This study argues that the observed-over-expected ratio, or O/E, is an inadequate metric for measuring the strength of consonant co-occurrence in Similar Place Avoidance. I advocate for the use of Yule's Q, an odds ratio based statistic that is not influenced by the relative proportions of labials, coronals, and dorsals in the dataset. This position is advanced on general statistical and linguistic considerations as well as through the analysis of empirical data from 32 languages. </p>
<p><br></p>
<p>Parallel typological analyses are conducted using O/E and Yule's Q. Cross-linguistic comparisons using O/E suggest that CVC sequences with two coronals are the least marked of the homorganic pairs. The same analysis using Yule's Q suggests any place of articulation may be the least/most marked in a given language; there are no cross-linguistic preferences. The disagreement between the two statistics can be accounted for by the fact that O/E is sensitive to the margin totals: coronals only appear to pattern separately from the labials and dorsals in the O/E analysis because they are considerably more frequent than are labial and dorsal segments.</p>
<p><br></p>
<p>To advance the use of Yule's Q in the study of Similar Place Avoidance, the paper provides guidance on constructing confidence intervals, measuring/interpreting effect size, and appropriate use of significance testing. Two case studies on aspects of Similar Place Avoidance in Latin and Medieval Castilian illustrate the proposed methodology.</p>
|
79 |
Applying ecological models to positive interactions among lotic fishes: implications for population and community regulation at multiple spatial scalesPeoples, Brandon Kevin 06 May 2015 (has links)
Positive biotic interactions such as mutualism, commensalism and facilitation are ubiquitous in nature, but historically have received considerably less research attention than negative interactions such as competition, predation and parasitism. The paucity of research on positive interactions is particularly evident in stream ecosystems and in vertebrate communities. Stream fishes clearly provide an ideal system for advancing research on positive interactions. Many minnows (Cyprinidae) of eastern North America engage in a potentially mutualistic reproductive interaction known as nest association, in which individuals of one species (nest associates) spawn in nests constructed by host species. In nest association, hosts provide unsilted gravel substrate for spawning nest associates, and increased parental care to associate broods. High associate: host egg ratios can create a dilution effect, reducing the probability that host eggs will be preyed upon by egg predators. Nest associative interactions are common, but are relatively understudied compared to other interactions among stream fishes.
The goals of this study were to apply general ecological models to this novel system to (a) gain new insight into the mechanisms structuring nest associative stream fish communities, and (b) to use inference from stream fish communities to potentially expand and improve the general ecological models. These goals required completion of three objectives, including (1) examining the influence of abiotic and biotic contexts on reproductive behavior and fitness outcomes between a cyprinid host and associate, using the biological markets model to generate predictions; (2) examining the utility of the nest web framework (previously only used for cavity nesting vertebrate communities) and the stress gradient hypothesis (previously applied almost exclusively to plant communities) for predicting which associate species spawn on nests built by various nest building species, and the consequences of these choices, respectively; and (3) using two-species occupancy modeling to determine the relative influence of biotic interactions and habitat covariates on the co-occurrence of a host and two nest associates.
To accomplish these goals, I conducted a large-scale experiment to manipulate presence of mutualists (Nocomis leptocephalus, host; Chrosomus oreas, associate), egg predators (biotic context) and habitat quality (abiotic context). I conducted behavioral nest observations and conducted repeated stream fish stream fish community surveys to collect demographic data. I constructed a nest web from observational data, and implemented structural equation modeling through an information-theoretic framework to identify nest web plausibility across a large spatial extent. I tested some predictions of the stress gradient hypothesis by regressing juveniles-per-nest and a metric of cyprinid community structure on a composite measure of physical stress (scaled gradients of catchment-scale agricultural land use and catchment area). I used two-species occupancy modeling to model co-occurrence of N. leptocephalus hosts and two associates, C. oreas and Clinostomus funduloides, and used an information-theoretic framework to compare hypotheses representing the importance of biotic interactions, habitat covariates or both at determining species co-occurrence.
Results corroborated some (but not all) model predictions, and identified room for improvement in each of the general models. Nest associative spawning by C. oreas was not context dependent; C. oreas did not spawn in the absence of a reproductively active male N. leptocephalus at any treatment level. However, the net fitness outcome of host and associate species was mutualistic, and the interaction outcome switched from commensalistic to mutualistic with abiotic context. N. leptocephalus reproductive success was improved by C. oreas presence in less-silted habitats, but not in heavily-silted habitats. This is most likely because broods were subject to predation in both habitat types, but were also negatively affected by siltation in silted habitats. Accordingly, egg dilution by associates was not sufficient to support a mutualistic relationship in less favorable habitats. Results suggest that the biological markets model may be a useful tool for predicting fitness outcomes of nest associative mutualism, but may not be as useful for predicting the behavioral outcomes of obligate mutualisms. Future applications of the biological markets model should carefully consider species traits, specifically the degree to which trading behavior is obligate for participants. Future work with this model will yield more insight by considering highly facultative associates.
Nest webs constructed from nest observational data suggested an interaction topology in which strong (nearly-obligate) associates relied most frequently on N. leptocephalus nests, and less frequently on nests constructed by Campostoma anomalum. Weak (facultative) associates were seldom associated with nests constructed by either species, and probably spawned before hosts began nesting activity. Structural equation models corroborated this topology throughout the New River basin, although some less-supported model evidence specified some nest association by weak associates. Juveniles-per-nest of strong associates responded positively to physical stress, while this metric for other cyprinid reproductive groups showed no relationship. Proportional representation of Nocomis and strong associates also increased predictably with physical stress. This study suggests that the nest web framework can be informative to systems outside the ones for which it was developed; future studies may be able to use this framework to better understand the role of habitat-modifying species in communities other than cavity nesting terrestrial vertebrates and nest associative stream fishes. This work extended the nest web framework by (a) modeling the outcomes of interactions instead of the interactions themselves, and (b) by using structural equation modeling to test nest web predictions with an information-theoretic framework. This study also suggests that the stress gradient hypothesis can be useful for understanding interaction dynamics in vertebrate communities; this represents the first direct evidence that this model can be used in vertebrate communities. Further, I demonstrate that the stress gradient hypothesis may be extended to predict community structure. However, more research in a diversity of systems will be needed to determine the extent to which this can be applied.
This study provides some of the first evidence of large-scale positive co-occurrence patterns in vertebrates. However, the precise roles of habitat covariates and biotic interactions were species-specific. Occupancy results suggest that co-occurrence between N. leptocephalus and nest associate C. funduloides is driven only by reproductive behavioral interactions. Alternatively, evidence suggests that co-occurrence between N. leptocephalus and C. oreas is driven by both nest association and habitat covariates. That two-species occupancy modeling can be a useful tool for comparing difficult-to-test hypotheses involving biotic interactions at large spatial scales. This study represents the first quantitative, multi-scale treatment of positive interactions in stream ecosystems.
This study demonstrates that applying general ecological models to stream fish communities can yield new insights about both the study system and the models themselves. While models of negative interactions, food webs and dispersal have been applied to stream fishes, we stand to gain much ground by also considering positive biotic interactions. In doing so, stream fish ecologists will also be able to contribute to the advancement of general ecology, and thus raise awareness for these understudied ecosystems and taxa. / Ph. D.
|
80 |
世界城市的概念輪廓與連結:以Flickr Tags為例 / The World Cities Concept Profiling And Concatenation:A Case Study On Flickr Tags曹期鈞, Tsao, Chi Chun Unknown Date (has links)
在這社會網路蓬勃發展之中、網際網路頻寬與速度相繼提昇的資訊年代,結合網路科技所衍生的Flickr網路相簿因應而生。Flickr提供許多API程式讓使用者或有興趣研究的專家學者能透過Flickr所收集及其所探討的議題,來觀察社會網路的變化情形。
社會網路主要是由節點以及節點間彼此相連結所形成,常見的網路模型大致可分為One-mode與Two-mode兩種網路結構,而本文則採用內部同時有兩種類節點、由兩個城市與Tags共同組合而成的Two-mode網路為基礎架構,期望藉此來闡述一個Tags系統分析法,利用Flickr使用者收集、標註之Flickr標記來與世界城市的概念輪廓相連結,透過提取城市語義分配給Flickr上照片的Tags,以及解決Part-Of-Speech (POS)、詞幹還原及雜訊處理…等問題,來達成依據排名結果分析出城市概念輪廓的最終目的。
除此之外,本文還運用了Flickr tag資料來彙整出41個城市的前100名tag,再篩選出前10名的tag,將其與相關的城市歸類一起比較。本文亦使用字詞共現指標(Tag co-occurrence)來計算與該城市的關聯性,再利用此法則來歸納出這兩個城市字詞共同出現的機會,以便於了解城市與城市之間的關連字詞組合。最後,本研究亦透過Flickr網站本身Popular Tags經由分析及匯出標籤雲的結果來與本文之實驗結果相對照,本實驗85%的吻合度驗證了可靠性。 / The Flickr Web Albums was born in the information age of social network growth, internet bandwidth and speed improvement. Users and researchers can observe the changing of social network from topics collected and studied by Flickr using API programs provided by Flickr.
The main structure of social network can be distinguished one-mode and two-mode network which is composed by nodes, generally. An approach for world cities concept profiling analysis is developed in this study by conbineing two types of nodes and two cities with tag which is the two-mode network using extracting city semantics for tags assigned to photos on Flickr, solving Part-of-Speech(POS), Stemming reduction and noise handing by collecting Flickr's tags from Flickr users.
The top 100 tags were slected for 41 cities and then top 10 tags for each city were also extracted. The Tag co-occurrence was also applied to analysis the relationship of cities. Then the connection between the cities can be understood by the result of tag co-occurrence opportunities. The 85% accurancy was demonstrated by comparing the result of analysised and exported Popular Tags from Flickr Website service and the result of experiments in this study.
|
Page generated in 0.2148 seconds