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21.
Marta Horta de Sousa Vergílio Helena Maria Gregório Pina Calado 《Planning Practice and Research》2016,31(4):452-471
The concepts of green infrastructure and ecological structure (ES) are current topics of discussion among the scientific community and spatial planners. ES is mandatory in Portugal in land-planning, such as municipal master plans, but no consensus has been reached on how to implement it. The concept has not yet been implemented in the Azores, a Portuguese autonomous region, even though the Region has the responsibility of adapting legislation or accomplishing the Portuguese legislature. This study presents a critical analysis of the available literature about ES and proposes a conceptual framework to define ES for small islands, which have unique characteristics, focusing on the Azorean archipelago. The conceptual framework meets the requirements of local legislation and uses an ecological function approach that is increasingly advocated in recent European recommendations. This framework is presented as a strategic and flexible way to identify both the important elements (recognized in current legislation) in a territory and the remaining potential of the territory. The framework also supports decision-making by allowing the identification of integrated solutions, decreasing trade-offs as much as possible and reconciling the needs of nature conservation and socioeconomic development. This framework could be applied to other small islands and other territories, with local adaptations. 相似文献
22.
Yasmine Antonini Rogério Parentoni Martins Ludmilla Moura Aguiar Rafael Dias Loyola 《Urban Ecosystems》2013,16(3):527-541
Few studies directly address the consequences of habitat fragmentation for pollinating insect communities, particularly for the neotropical key pollinator group of stingless bees. Most studies on bees have defined habitat fragments as remnant patches of floral hosts or forests, overlooking the nesting needs of bees. Their conclusion is that habitat fragmentation is broadly deleterious; however, there are contrasting results in the literature. Insightful studies on habitat fragmentation and bees should consider fragmentation, alteration and loss of nesting habitats—not just patches of forage plants –, as well as the permeability of the surrounding matrix to interpatch movement. Here we investigated the effects of fragmentation caused by urbanization on stingless bee species’ composition and richness, as well as the permeability of the surrounding matrix. We collected bees from flowering plants and recorded phytosociological variables of five forest remnants (ranging from 64 ha to 900 ha) in southeastern Brazil. Large fragments did not contain more species per unit area than smaller ones; in fact, we found more species in small fragments, most of which were generalist bees. The presence of more habitat generalist stingless bee species was also correlated to the structure of vegetation in these fragments. In conclusion, the quality of the habitat within a fragment (structure of vegetation) as well as the quality of the matrix has a direct relation to the bee species composition. This can be seen in the direct relationship between structural diversity of the environment and age of the fragments. The matrix that holds the most recent fragments, probably due to the sprawl of the city, is more heterogeneous than the one with the oldest fragments. The most heterogeneous matrices have a certain balance between the trees, buildings and bare soil or herbaceous vegetation coverage, making the array less impermeable to bees. 相似文献
23.
Diego I. Gallardo Yolanda M. Gómez Mário de Castro 《Journal of Statistical Computation and Simulation》2018,88(11):2137-2149
Models for dealing with survival data in the presence of a cured fraction of individuals have attracted the attention of many researchers and practitioners in recent years. In this paper, we propose a cure rate model under the competing risks scenario. For the number of causes that can lead to the event of interest, we assume the polylogarithm distribution. The model is flexible in the sense it encompasses some well-known models, which can be tested using large sample test statistics applied to nested models. Maximum-likelihood estimation based on the EM algorithm and hypothesis testing are investigated. Results of simulation studies designed to gauge the performance of the estimation method and of two test statistics are reported. The methodology is applied in the analysis of a data set. 相似文献
24.
Paula Perre Rafael D. Loyola Thomas M. Lewinsohn Mário Almeida-Neto 《Urban Ecosystems》2011,14(4):711-722
Exotic plant species very often comprise a large proportion of urban floras. Because herbivorous insects depend on the presence
of suitable host plants to maintain their populations, it is imperative to elucidate the relative importance of native and
exotic hosts to understand the response of herbivorous guilds to urbanization. By using a plant-herbivore system composed
of Asteraceae hosts and flower-head endophagous insects, we investigated whether the diversity and composition of herbivorous
insects differs between native and exotic host-plant species in an urban environment. Although we found only seven exotic
Asteraceae among the 30 species recorded, the overall abundance of exotics was considerably greater than that of native host
plants. Overall, the exotic host species supported a small subset of the herbivore assemblage found on the native ones. The
number of herbivore species per host species was significantly higher among the native plants, but we did not find a difference
in herbivore abundance. Moreover, the higher taxonomic composition of herbivores on exotic Asteraceae was reduced, being composed
of only three genera and two families from a total of 16 genera and six families of herbivores. These results provide support
for the idea that plants outside of their original geographic distribution have lower loads of enemies than phylogenetically
related native species. Our findings indicate that native host plants in urban areas play a critical role in supporting the
native herbivorous insect fauna. 相似文献
25.
In this paper we deal with robust inference in heteroscedastic measurement error models. Rather than the normal distribution, we postulate a Student t distribution for the observed variables. Maximum likelihood estimates are computed numerically. Consistent estimation of the asymptotic covariance matrices of the maximum likelihood and generalized least squares estimators is also discussed. Three test statistics are proposed for testing hypotheses of interest with the asymptotic chi-square distribution which guarantees correct asymptotic significance levels. Results of simulations and an application to a real data set are also reported. 相似文献
26.
Mário de Castro Ming‐Hui Chen Joseph G. Ibrahim John P. Klein 《Scandinavian Journal of Statistics》2014,41(1):187-199
In this paper, we propose a general class of Gamma frailty transformation models for multivariate survival data. The transformation class includes the commonly used proportional hazards and proportional odds models. The proposed class also includes a family of cure rate models. Under an improper prior for the parameters, we establish propriety of the posterior distribution. A novel Gibbs sampling algorithm is developed for sampling from the observed data posterior distribution. A simulation study is conducted to examine the properties of the proposed methodology. An application to a data set from a cord blood transplantation study is also reported. 相似文献
27.
Luzia Gonçalves M. Rosário de Oliveira Cláudia Pascoal Ana Pires 《Journal of applied statistics》2012,39(11):2453-2473
The poor performance of the Wald method for constructing confidence intervals (CIs) for a binomial proportion has been demonstrated in a vast literature. The related problem of sample size determination needs to be updated and comparative studies are essential to understanding the performance of alternative methods. In this paper, the sample size is obtained for the Clopper–Pearson, Bayesian (Uniform and Jeffreys priors), Wilson, Agresti–Coull, Anscombe, and Wald methods. Two two-step procedures are used: one based on the expected length (EL) of the CI and another one on its first-order approximation. In the first step, all possible solutions that satisfy the optimal criterion are obtained. In the second step, a single solution is proposed according to a new criterion (e.g. highest coverage probability (CP)). In practice, it is expected a sample size reduction, therefore, we explore the behavior of the methods admitting 30% and 50% of losses. For all the methods, the ELs are inflated, as expected, but the coverage probabilities remain close to the original target (with few exceptions). It is not easy to suggest a method that is optimal throughout the range (0, 1) for p. Depending on whether the goal is to achieve CP approximately or above the nominal level different recommendations are made. 相似文献
28.
Eveliny Barroso Da Silva Jalmar Manuel Farfan Carrasco Mário De Castro 《统计学通讯:模拟与计算》2018,47(1):229-248
In this article, we propose a beta regression model with multiplicative log-normal measurement errors. Three estimation methods are presented, namely, naive, calibration regression, and pseudo likelihood. The nuisance parameters are estimated from a system of estimation equations using replicated data and these estimates are used to propose a pseudo likelihood function. A simulation study was performed to assess some properties of the proposed methods. Results from an example with a real dataset, including diagnostic tools, are also reported. 相似文献
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30.
José Marmeleira Mário Godinho Peter Vogelaere 《European review of aging and physical activity》2009,6(1):29-38
The elderly represent the fastest growing driving population. Older drivers have a high crash rate per distance traveled,
a high risk of injury or death in traffic accidents, and are commonly found to be ‘at fault’ in crashes. This reality has
focused more interest on issues associated with the fitness to drive and the safety of older drivers. Many older adults depend
greatly on their personal vehicle for transportation and suffer a marked loss of quality of life when, as a consequence of
no longer being able or permitted to drive, their mobility becomes significantly restricted. The reasons for the deterioration
of driving performance that occur during the aging process are multi-factorial and a great deal of research has focused on
the identification of those factors. Nevertheless, some studies incorporating training programs have tried, with some success,
to improve the driving-related abilities of older drivers. It has been demonstrated that physical activity can promote several
skills that are associated with driving performance in older drivers. Few studies, though, have conducted exercise interventions
among older drivers intended to enhance their driving-related abilities and promote road safety. In this context, the purpose
of this work consists of examining the perceptual, cognitive, health, and physical factors related to fitness to drive in
older adults and identifying possible strategies that can enhance their driving-related abilities. Moreover, potential mechanisms
underlying the relationship among physical activity, driving ability, and road safety are discussed. 相似文献